text:
In a PN-junction diode not connected to any circuit

(a) The potential is the same everywhere

(b) The P-type is at higher potential than the N-type side

(c) There is an electric field at the junction directed from the N- type side to the P- type side

(d) There is an electric field at the junction directed from the P-type side to the N-type side

Concept Questions :-

PN junction
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

Which of the following statements is not true

(a) The resistance of intrinsic semiconductors decrease with increase of temperature

(b) Doping pure with trivalent impurities give P-type semiconductors

(c) The majority carriers in N-type semiconductors are holes

(d) A PN-junction can act as a semiconductor diode

Concept Questions :-

Types of semiconductors
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The dominant mechanisms for motion of charge carriers in forward and reverse biased silicon P-N junctions are

(a) Drift in forward bias, diffusion in reverse bias

(b) Diffusion in forward bias, drift in reverse bias

(c) Diffusion in both forward and reverse bias

(d) Drift in both forward and reverse bias

Concept Questions :-

PN junction
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

Which one is reverse-biased

Concept Questions :-

Applications of PN junction
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

Which one is in forward bias

Concept Questions :-

PN junction
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The reason of current flow in P-N junction in forward bias is

(a) Drifting of charge carriers

(b) Minority charge carriers

(c) Diffusion of charge carriers

(d) All of these

Concept Questions :-

PN junction
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

The resistance of a reverse biased P-N junction diode is about
(a) 1 ohm                        (b) ${10}^{2}$ohm
(c) ${10}^{3}$ ohm                     (d) ${10}^{6}$ ohm

Concept Questions :-

PN junction
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

Avalanche breakdown is due to

(a) Collision of minority charge carrier

(b) Increase in depletion layer thickness

(c) Decrease in depletion layer thickness

(d) None of these

Concept Questions :-

Energy band theory
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

Zener breakdown in a semi-conductor diode occurs when

(a) Forward current exceeds certain value

(b) Reverse bias exceeds certain value

(c) Forward bias exceeds certain value

(d) Potential barrier is reduced to zero

Concept Questions :-

Applications of PN junction
High Yielding Test Series + Question Bank - NEET 2020

Difficulty Level:

When forward bias is applied to a P-N junction, then what happens to the potential barrier ${V}_{\mathbit{B}}$, and the width of charge depleted region x

(a) ${V}_{\mathbit{B}}$ increases, x decreases

(b) ${V}_{\mathbit{B}}$ decreases, x increases

(c) ${V}_{\mathbit{B}}$ increases, x increases

(d) ${V}_{\mathbit{B}}$ decreases, x decreases

Concept Questions :-

PN junction


text:
## Wednesday, December 31, 2008 ... /////

### Happy New Year 2009

Try JibJab Sendables® eCards today!

Thanks to Rae Ann!

2008 will be over tonight. Don't forget about the extra leap second that will be added!

2009 is going to be the International Year of Astronomy and the International Year of Natural Fibres. Recall that strings in string theory are the ultimate natural fibres. The LHC will hopefully begin to generate real data.

Czech EU presidency will replace the old French-led progress towards the New European Soviet. See a new portrait of the Czech president by the Daily Mail and fresh, today's pictures from Klaus' skiing.

If you need to factorize or Romanize,
2009 = 7 * 7 * 41 = MMIX.
Happy New Year!

### Feynman: The reason for antiparticles

1986 Dirac memorial lectures:

Playlist (click for 7x 10 minutes)
In the first video, Richard Feynman begins his talk at 4:00.

## Tuesday, December 30, 2008 ... /////

### Klaus: Treaty of Lisbon: a tutorial for beginners

Every single day, I am being surprised how many people ask me what that Treaty of Lisbon is. And how many of them admit that they couldn't say even a few simple words about it to their kids or grandparents. And all of them add: why don't you explain it to us in simple terms? The treaty is not simple but I will try to do it, anyway.

1. The European Union (EU, formerly the European Communities, EC, and the European Economic Community, EEC, before that) is defined by treaties signed by the member states. These treaties are commonly named after the place where they were signed. The first treaties were the so-called Treaties of Rome in 1957. So far the latest one is the Treaty of Nice from 2001.

2. All these treaties - except for the first one - elaborate upon and modify the previous treaties. In other words, they have no meaning if separated. It is not even possible to understand them unless we have access to the other treaties. Each treaty represents either a gradual or fundamental shift of the European integration process towards closer, tighter, and greater unification and centralization and towards the weakening of the positions and competences of the member states.

3. There used to be a special treaty that was supposed to be radically new and it was therefore named differently, too - it was the 2004 European Constitution (or the Constitutional Treaty). Former prime minister Mr Gross signed it on behalf of the Czech Republic. That treaty differed both by its scope as well its form (it was a comprehensive text that was replacing all the previous treaties). This fact led - together with the word "Constitution" included in its name as well as its text - to the need to organize referenda in many countries in order to approve it. We know the result: the 2005 referenda in France and the Netherlands have rejected it.

## Monday, December 29, 2008 ... /////

### Richard Feynman, Mr X, and the arrow of time

As we have mentioned, on Christmas Eve, Sean Carroll began to understand that the previous 40 years of his thinking about the arrow of time had been plagued by elementary, childish mistakes. In his very recent text

Have a Thermodynamically Consistent Christmas,
he announced that he finally understood that subsystems with opposite arrows of time cannot co-exist and interact in the same Universe, i.e. that the arrow of time is and must be universal. That was a pretty radical departure from his previous writings that included "pearls" such as
Incompatible Arrows I
Incompatible Arrows II
Incompatible Arrows III
Incompatible Arrows IV
The Arrow of Time in Scientific American
Latest Declamations about the Arrow of Time
and dozens of similarly dumb articles - including bizarre fairy-tales about the Boltzmann Brains - that he has written over the years. In all these texts, Carroll had promoted the absurd opinion that incompatible arrows of time are a priori allowed to co-exist and the origin of the second law of thermodynamics lies in cosmology (wrong), and not in statistical physics (correct).

In the newest article at Cosmic Variance,
Richard Feynman on Boltzmann Brains,
Carroll mentions Feynman's attitude to the problem. Feynman thought the same thing about these issues as every sufficiently intelligent and independently thinking person does after having looked into the problem at least for a few days.

For example, the hypothesis of the Boltzmann Brains - namely that we are just a low-entropy fluctuation in a high-entropy world - can be easily ruled out because it predicts that virtually everything in the Universe (that is unnecessary for our brains to exist) should be found in a disordered state without a consistent history - but the prediction is falsified as soon as you see that there seem to be other objects that apparently follow from an organized, meaningful past - an argument we have mentioned repeatedly at TRF.

It's really not a big deal. The Boltzmann Brain hypothesis can be falsified by any tiny amount of empirical evidence. Also, no physical or cosmological theory - as opposed to a philosophical theory - can ever predict that we should be Boltzmann Brains. If it could make such a prediction, that would make it inconsistent with the very basic observations.

Obviously, no kind of cosmology - neither inflationary nor cyclic nor other cosmology - is inconsistent with the existence of objects of an increasing entropy and with their basic qualitative "local" behavior. It follows that no such theory can be predicting that we are the Boltzmann Brains, and everyone who thinks that such a prediction is generated is making a trivial logical mistake. Sadly, there are hundreds if not thousands of wrong papers built on this meme.

But Feynman's opinions about this issue were not only much closer to mine than Carroll wants you to believe. They were also much more militant. ;-) You may read a text by Stephen Hawking,
The No Boundary Condition And The Arrow Of Time
in a book called "Physical Origins of Time Asymmetry".

In this article, Hawking talks about what he considers the greatest scientific blunder of his life (rightfully, in my opinion): Hawking used to think (because of some arguments based on the imaginary time) that the logical arrow of time is bound to be aligned with the cosmological arrow of time given by the expansion of the Universe.

But at the beginning, he talks about a conference on the direction of time that took place at Cornell in 1963. A lot of nonsense, pretty much identical to the nonsense printed by Sean Carroll during his previous life, has been said on the conference. Stephen Hawking explains that Richard Feynman considered the proceedings so worthless - he was so disgusted - that he didn't want his name to be associated with them. So he was referred to as Mr X even though everyone has always known that Mr X was no one else than Richard Feynman.

You know, when Feynman was determining the right QED propagators, a work that was initiated by his and Wheeler's research of advanced and retarded waves, he has made some important insights about the direction of time in the fundamental formulation of the physical laws. He realized that the propagators must be half-advanced, half-retarded, a rule that is equivalent to the "i epsilon" prescription in the momentum space. This rule reflects one of the aspects of the microscopic time-reversal symmetry.

However, when it came to the observed time asymmetry, Richard Feynman realized what your humble correspondent and every sensible person does: the arrow of time is always a consequence of ordinary statistical mechanics. Read the bottom of page 346 in Hawking's article

In fact, the arrow of time always follows from ordinary statistical mechanics. QED is just an example but all these arrows of time - all thermodynamic and logical arrows of time associated with friction, heat transfers, decoherence, or memory of humans or computers or anything else - are always aligned with each other.

Using the words of Mr X, matter is thermodynamically one-sided. It has the disposition to damp when you shake it. The hypothetical anti-thermodynamic matter is just an image of the normal matter, and the two arrows can't ever co-exist. The time-asymmetric logic or thermodynamics does not contradict the T- (or CPT-) symmetric microsopic laws in any way. And whatever words you identify as the "ultimate reason for the thermodynamic asymmetry", it is a basic and true fact about the real world. A very important one.

It's of course fair to say that we don't understand the very origin of the Universe and the beginning of the Universe is connected with a very low-entropy state. But it is an entirely different thing to say that the very ordinary phenomena that we observe today are not properly understood by the physical laws as we know them. The latter proposition is absurd and the misunderstanding is only a testimony of the incompetence of many cosmologists as physicists rather than a testimony of an incompleteness of the laws of physics as we know them.

Of course, the 1963 conference was not the first cosmological conference that drove Feynman up the wall. :-) In 1962, he wrote a famous letter to his wife about another cosmological conference in Warsaw:
"I am not getting anything out of the meeting. I am learning nothing. Because there are no experiments, this field is not an active one, so few of the best men are doing work in it. The result is that there are hosts of dopes here (126) and it is not good for my blood pressure. Remind me not to come to any more gravity conferences!"
Well, not much has changed about similar conferences during the last 45+ years. There are still hosts of dopes over there who discuss nonsense. But maybe, once Sean Carroll realized that he's been saying nonsense about similar issues for years and as soon as he starts to pretend that he has been saying the very opposite thing than what he was ;-), rational reasoning could perhaps return to these debates.

### La Niña conditions are back

According to the newest, today's weekly ENSO status report, La Niña conditions are back and they are likely to continue at least for a few months.

Video 1: Twelve days of global warming: compare with the Xmas versions. Thanks to Anthony Watts & Minnesotans for Global Warming. ;-)

Commercial: Dr Roy Spencer (UAH) has a new, more professional website dedicated to the climate than ever before.

### Bob McElrath, gravitons are not made out of dust

Attempts to "construct" gravity out of easy-to-imagine ingredients have become a modern counterpart of medieval alchemy.

The alchemists believed that by "cooking" the ordinary metals just a little bit differently from their predecessors, they could have produced gold, silver, or the elixir of life.
A mostly unrelated commercial break: N. Sriram has sent me a beautiful essay by Paul Graham about heresies and taboos now and then, "What You Can't Say"
The contemporary gravitational alchemists believe that by combining random ordinary particles and mathematical indices just a little bit differently than their predecessors, they can explain the gravitational force in layman's terms. They're probably driven by the laymen's desire to make gravity look closer to our everyday life: see Feynman's comments about LeSage's theory of gravity at 5:20 of his Messenger 2 Lecture for a similar sociological example.

Needless to say, both beliefs are equally scientifically ludicrous and unsupportable. The difference between gold and iron is more profound than the question how much time you spend by "cooking" the iron. Analogously, the difference between gravitons and random composite states of random particles is more profound than the shape of mathematical indices or the percentage of different kinds of condensed matter papers that are being cited.

Emergent electroweak gravity
by Bob McElrath. Gravitons are bound states of neutrinos, the author boldly claims. I know that Prof Conway is able to do all kinds of things but his excitement about this type of manifest nonsense represents such a complete failure of judgment about so many fundamental questions of physics that I am simply unable to fully respect Prof Conway as a physicist.

## Sunday, December 28, 2008 ... /////

### Windows Movie Maker: unspecified error

I couldn't run Movie Maker 2.1. It immediately gave me an "Unspecified Error" popup message. Movie Maker 2.6 behaved in the same way. I learned that it worked fine for other users.

It turned out that the temporary directory got wrong read-only file permissions - who knows why.

## Friday, December 26, 2008 ... /////

### Czech EU presidency: January 2009 program

In six days, the Czech Republic will take over the EU presidency.

A leader with Napoleon complex who loves the financial crisis, irrational fears of a changing weather, and wars in the Caucasus because they are tools to "prove" his own greatness will be replaced by a tall, pragmatic, down-to-earth prime minister of a country with a brilliant president.

We will show Europe the sweet taste of its own medicine...

It may be a good time to buy things like the European stocks right now because the Czech government is likely to adopt a more rational attitude towards the turmoil in the economy. They will not emphasize the "catastrophic crisis" every day in order to increase their importance and they won't try to intervene everywhere. After a dramatic drop during the counterproductive French presidency, it may be reasonable to expect a Czech bounce, not to be confused with a bouncing cheque.

You shouldn't expect much from the EU presidency because it is mostly an administrative job. However, as a climate skeptic who is located in Europe, you should be able to resist attempts of your environment to marginalize you during H1 of 2009. Don't forget that the continent is officially led by some of the world's most prominent climate skeptics, to the dismay of all the liars and fraudsters in the world's politically correct media.
See a new, unusually neutral BBC portrait of Václav Klaus.
Czech ministers are in charge

However, what the presidency actually means is that the Czech ministers will become the "leaders" of groups of their colleagues from the EU countries. They will invite them to Prague and other places in Czechia to chat and to have a lunch, coffee, and tea. As hosts, they may be more visible, but because they must also cook, they may actually have less time for more serious work. ;-)

Once again, don't expect miracles: try to do them yourself.

Here is the program for January 2009:
• 07 Jan, Prague: Czech government meets the European Commission (government EU) in the Lobkowicz palace: chat about energy security and transatlantic relations
• 07 Jan, Prague: European year of creativity and innovation (2009) starts: expect a lot of nice clichés about the importance of creativity and innovation that will probably lead nowhere
• 08 Jan, Prague: General Affairs Council: a gala opening in the National Theater plus a dinner in the Municipal House, followed by talks about energy security and transatlantic relations
• 08-09 Jan, Prague: Gender Mainstreaming: eurofeminists will meet at a "high level working group meeting" to prepare new plans to phase out men out of the society: the Czech presidency can't change anything about the existence of this movement
• 15-16 Jan, Prague: Justice and Home Affairs: the ministers of these two resorts will discuss safe technologies, technology helping security, mutual recognition of crime matters, and future of the family law
• 22-23 Jan, Prague: Ministers of innovation: INCOM, a conference of ministers for innovation, creativity, and development
• 22-24 Jan, Luhačovice (spa): Employment and social affairs: EU ministers chat about their social bullshit
• 29-30 Jan, Prague: Development ministers: discussions about the financial crisis will include some people from the EU commission
• 29-30 Jan, Ostrava (Northeast coal capital of the country): Energy security and common electricity market: a conferenec about the harmonization of the laws, transmission

## Thursday, December 25, 2008 ... /////

### Merry Christmas

Below this Christmas posting, you can find newer non-Christmas postings, too!

TRF wishes the readers, including atheists, pagans, agnostics, Muslims, Jews, Hindus, Buddhists, and last but not least Christians, Merry Christmas! ;-)

White Christmas with Bing Crosby (written by Irving Berlin) remains the best-selling single in any music category ever. By the way, Marjorie Reynolds' 1942 looks, haircut, and fashion remains pretty hot in my eyes: not much "progress" for the last 66 years.

### Emergent spacetime from modular motives

Once again, I believe that the best hep-th article today is the first one. Rolf Schimmrigk wrote about

Emergent spacetime from modular motives (PDF)
Schimmrigk's work may sound as hardcore mathematics - and it arguably is - but don't forget that there are millions of people who are familiar with his name: the readers of "The Elegant Universe" by Brian Greene. ;-)

The term "motive" sounds very mysterious, mathematically obscure, and these papers contain a lot of other jargon of category theory (also known as "general abstract nonsense"), too. However, the goal of all of these fancy things is to actually make things more physical, not less physical. For example, there are all kinds of homologies that are morally equivalent - including de Rham cohomology, Betti cohomology, and Čech cohomology (yes, the last name of Eduard Čech is a Czech name and it means Czech).

While a physicist would simply adopt these notions as being equivalent, mathematicians can't do so. Instead, Alexander Grothendieck had to visualize an enigmatic object, the motive, that unifies all the moral and morally equivalent ideas underlying various kinds of homology. The motive is supposed to unify all essential features of a manifold. You can see the "very big picture", quasi-religious sentiments penetrating all these words that make the situation analogous to M-theory before it was demystified.

After all, "motives" begin with an "M", too, so M-theory could be a M(otive) theory, too. :-)

However, many of these notions in the theory of motives have been given rigorous definitions and exact results have been proven. Schimmrigk is now using the spiritual flavor of motives ;-) to reconstruct spacetime geometry from a conformal field theory. So you should immediately notice that his emergent geometry is linked to perturbative string theory, not necessarily to "all of string theory", and as we know, the geometry that emerges from a particular CFT is not unique (due to mirror symmetry and related dualities).

## Wednesday, December 24, 2008 ... /////

### Joe Polchinski: String Theory: problem solutions

Matt Headrick has finally released his old solutions to the problems in "String Theory" by Joe Polchinski:

A solution manual for Polchinski's "String Theory" (PDF)
It's 114 pages of rather impressive stuff. Lazy students no longer have to torture their branes ;-) and parroting and plagiarizing will be enough - but it's not Matt's fault!

## Tuesday, December 23, 2008 ... /////

### Peak oilers' mental meltdown

Although the oil price returned to $40.00 or so, it has already seen prices below$34.00 which is less than 23% of the peak price ($147.50) in July 2008, just five months ago. The decrease we have witnessed was by a factor of 4.5 which is a pretty amazing change for such a short interval. Most peak oilers have gone silent but there exists at least one peak oiler whom we know well and who used the recent events as evidence that the world will run out of oil soon, that the price will diverge, and that we need the leadership of messiahs like himself. Yes, his name is Alexander Ač. In his newest posting, he asks whether the Slovak government will revise its energy strategic plans. Their government plans the Slovak oil imports in 2030 to be twice as large as the current figures which sounds reasonable because Slovakia is exactly the kind of a country that may expect such an increase. Alexander's hysterical rant is composed of three sections: • Oil production will plummet and the depletion will accelerate • We need a global energy revolution • We have to increase the investment In the first section, he writes that the output is going to shrink dramatically. In the second section, he emphasizes that all energy in the world must be replaced by the ludicrous sources of energy. In the final section, he uses the recent drop of the oil price to argue that there will be no oil in the future because the investment will drop, and the price will therefore drift towards infinity. What Alexander Ač is able to write is just stunning and it shows that there is no meritocracy left in our society. In the 10th posting below the newest one, Alexander Ač writes that the oil price is soon going to surpass$500 per barrel

The real prices are smaller by a factor of twelve or so. His forecasts has failed so miserably that if his life depended on these forecasts, he would have been dead for quite some time. If he had made substantial investments, he would be broke by now.

However, Alexander is just an irrelevant grad student whose skull is full of dirt. But there are many similar people who are equally uncapable to evaluate the reality and their own miserable failures who are controlling all kinds of official institutions, including the hacks who have been named as members of Barack Obama's presidential team.

For any real application, the essential question is the future price of oil. Anyone who makes any decision or investment - a medium-term one or a long-term one - depends on this unknown piece of information.

Power-thirsty, mentally sick pseudointellectuals similar to Alexander Ač are completely unable to predict absolutely anything, their predictions systematically differ from reality by many orders of magnitude, but they constantly want their influence to increase. Alexander, could you please try to imagine the deep lake of excrements into which the world would immerse if you had any influence on it?

Do you understand the difference between gold and shit? It's been established beyond any reasonable doubts that your thinking and writing belongs squarely to the latter category.

Of course, the price oscillates because no one really knows how the supply and demand will compare next year or in 2015. But these oscillations are not a way to show that ultracommunist fanatics who want to regulate the world should be listened to because the world can't survive without them. Quite on the contrary, these price fluctuations are natural processes by which the invisible hand of the free markets regulates the situation.

Indeed, the investment into new oil fields (and alternative energy sourecs) is going to decrease markedly is oil price stays below $50. But that's exactly the right thing that should happen because if the price is low, it means that oil is not that valuable - a tautology that the communist freaks simply can't ever understand - and it's simply not a good idea to invest much to obtain much more of this stuff. Roughly speaking, a liter of oil is as cheap as a liter of bottled water. Whoever assumes that oil must be treated on par with gold is simply a moron, if he makes investments based on his theory, he should quickly become broke, and everyone should let the laws of Nature to remove such a failed life form from the visible surface of the Earth, in order to free space for others. If oil ever gets more scarce, the investment into new oil fields and other energy sources will naturally increase once again and help to lower the oil price. At any rate, the last thing that the system needs are the hands of power-thirsty regulating fanatics, especially not those who have failed in all the predictions they have ever made in their lives and who don't even realize the relationships between the price and the value, the supply and the demand. Finally, I want people to be responsible for their bad predictions and counterproductive interventions which means that I want someone to give failed people like Alexander Ač a proper thrashing. And that's the memo. ## Saturday, December 20, 2008 ... ///// ### Czech American keyboard If you essentially prefer the U.S. keyboard but you still need all the Czech characters with diacritical signs, you are recommended Czech LUMO keyboard (old version) for Windows. Download the ZIP file above, unpack it, and run setup.exe – which is the same thing as if you run the layout01 for i386 installation package (or the corresponding files for 64-bit systems based on Intel or AMD: setup.exe chooses the right microprocessor). It will add the "Czech LUMO" keyboard as an additional choice for the Czech language. Whenever possible, all the special characters are arranged just like on the U.S. keyboard. ## Friday, December 19, 2008 ... ///// ### Harebrained theorist John Holdren will become Obama's science adviser Science magazine has reported that John Holdren, a professional environmental judgment day doomsayer, was going to become Barack Obama's top science adviser. Indeed, on Saturday, Barack Obama announced that Holdren was tapped. See also NY Times Tierney Lab: Flawed science advice for Obama? John Holdren is the ultimate example of the pseudointellectual impurities that have recently flooded universities and academies throughout the Western world. Population growth means death Do you want to know what is his specialization? The easiest path to the answer is to look at his publication list at scholar.google.com. No, he hasn't found anything about laser cooling, like Steven Chu, despite his PhD in plasma physics. Instead, he has only written 3 very well-known texts - with at least 100 citations - and all of them were concerned with the "catastrophic" population growth. A few additional, newer articles with 50 citations or so are about the "catastrophic" climate change. ## Thursday, December 18, 2008 ... ///// ### Dow Jones similarity graph Besides WeatherData, Mathematica 7 has another function that is crowded with data, namely FinancialData. If you ask what is Length[FinancialData[]], the result is 189,616. It means that Mathematica knows about the detailed history (and present status) of stock prices, exchange rates, and similar numbers from 189,616 companies, currency pairs, and their generalizations. So I tried to change the "core function" of an algorithm to draw a similarity graph, a set of procedures that have already been applied to the picture of David Gross. However, I was not connecting pieces of pictures but rather 30 companies in the Dow Jones index. This is the result for similaritygraph[2]: Click the picture to get a larger screenshot that also contains similaritygraph[3] and some commands. Note the nice "supermarket/food" subgraph of 5 companies with Johnson & Johnson in the middle, surrounded by Procter & Gamble, Kraft Foods Inc., and Wal-Mart Stores, Inc. followed by McDonald's Corporation. It seems to make sense - probably more sense than the decoupling of IBM from the technological corner of Microsoft, Intel, etc. I must tell you how I determined the "distance" between the companies. I took the daily stock prices since January 1st, 2007 through December 17th, 2008. The logarithm of all these prices were computed so that the overall scaling becomes irrelevant. All these graphs (lists of numbers) were supplemented with their mirror, anti-chronological copies, in order to obtain an even periodic function for each company and to be ready for the simplest - complex/complex - Fourier transform function available in Mathematica. ## Wednesday, December 17, 2008 ... ///// ### A giant breach in Earth's magnetic field First, see: NASA HTML, NASA video, Anthony Watts They seem to be puzzled by a lot of things about the interactions between the Sun's and Earth's magnetic fields. Various changes differ from their expectations by an order of magnitude, and so on. At any rate, there seem to be a lot of effects that depend on the relative orientation of the magnetic fields. One of five THEMIS probes that study these issues We normally say that the solar activity has an 11-year periodicity but the even and odd cycles differ by the sign of the magnetic field and their effects on the Earth may differ due to the Earth's own magnetic field. So the underlying periodicity is 22 years. In fact, a 20+ year temperature (or related) signal has been observed in tree rings. It was puzzling because people thought that only the absolute value of the Sun's magnetic field should matter, and the latter had a 11-year periodicity. However, already in 2007, we mentioned a paper about a possible role of interstellar dust as a climate driver: this dust was proposed to realize the 22-year cycles. Something of this sort is probably happening. It is not exactly clear which of the effects related to the magnetic fields and magnetic storms and auroras etc. are going to be crucial for the temperature. At any rate, I find it likely that a proper understanding of the flow of charged particles - not only cosmic rays - and their interactions with the magnetic fields is going to be important for a proper understanding of climate variability. And be sure that the periodic effects with the 22-year period are not the only ones that will exist and matter. ### Mafia II: Holiday confession trailer Click the image to see the trailer. (YouTube.) Mafia II is going to be released in 2009 and it is likely to become one of the relatively few PC games that your humble correspondent has ever bought. The graphics and the atmosphere look pretty amazing to me. ### Klaus the knight Last night, I was honored to be invited (with a friend) to an X-mas "party" of CEP (Center for Economics and Politics), a libertarian think tank of Czech president Václav Klaus and Petr Mach who may be just establishing a new political (libertarian euroskeptical) party (plus a finite set of others). It was a pleasant experience. At least after some time, it is fun to see many of the very famous faces from the world of the Czech culture and politics again. Their number could have been slightly lower than a year ago but it was arguably above 50% of the last year's number, indicating that after the velvet Klaus-ODS divorce, you shouldn't underestimate the new party that could import lots of voters (and politicians) from ODS (and other places). While I didn't have any gift for the president, I actually received one: what a painful combination. It was the new issue of Euro (euro.cz), a magazine targeting Czech managers. There's a lot of mainstream "gossip" from the world of these people: the managers like to read it. The magazine treats businessmen as rock stars and tells you stories from their (and the economy's) life. You wouldn't be certain what they think about Klaus' struggle against the global warming religion, the Lisbon treaty, and similar fashionable tendencies. You might even guess that a magazine with such a Euro name is going to endorse the centralistic Euronaive position. Well, you would be wrong. It turns out that the magazine totally supports Klaus, and there are many articles in this issue to demonstrate my assertion. The picture above - on the cover - shows Klaus as a knight who finds it "necessary to fight against everyone, if you own the truth" or simply "with truth against everybody", a slogan of a top Czechoslovak politician from the 1920s, Mr Karel Kramář, that I am currently unable to translate in a more faithful and readable way. The picture looks more respectful than the Prague Castle Batman in The Economist (or other places) and I assure you that the text of the articles shows a similar difference in the attitude. That's pretty cute because the Western media that I normally hear about - including the business media - often like to join the irrational witch hunts and they endorse the "only" politically correct line. Well, it works differently here and if you're doing business in Czechia or a few other places of the New Europe, you may actually be expected to denounce some of the recent anti-business extempores of people like Nicolas Sarkozy! (Incidentally, Sarkozy has attacked the Czech president for his refusal to fly the EU flag above the Prague Castle, the symbol of Czech statehood, which Klaus is known not to intend. It seems that Sarkozy is slowly losing his mind. Imagine that he asked the U.S. president to obediently fly the EU, French, or the U.N. flag above the White House. I can't believe Sarkozy is serious. Has he learned something about the history, the meaning of countries' sovereignty, and the wars that often erupt when it is breached? Mr Sarkozy, do you seriously think that according to the existing international law, it is the French president, and not the Czech president, who determines the flags flying above the historical home to the Czech kings?) We love our EU royal pair, Carla and Nicolas. Nicolas, you could find out that you're not only against the Czechs but also some Britons and many other nations. Václav Klaus mentioned that I was slightly left-wing. Of course, I didn't have a sufficient level of testosterone at that moment to argue with the president that I was more right-wing than he was - even though I probably am! :-). Instead, I understood the criticism as a deserved one in the context of my newspaper article supporting the (then)$700 billion bailout. (If you're completely missing the rules of the game, let me explain that saying that someone is left-wing is surely not a compliment!) :-)

Funny but not realistic: latex Sarkozy conspires against latex Klaus during a dinner
You know, I surely didn't support any (or escalating) interventions to the economy. Also, I supported the bailout because
1. the value of the fiat money is a priori ill-defined and controllable by the central bank or the government. Because they can do many things, it is a question which approach is actually "market neutral", and as I explained in the thought experiment about the Dow Jones money, I think that the natural "non-interventionist" monetary politics is actually trying to keep the ratio of money and equities nearly constant. The bailout is a slightly different procedure but it has similar consequences. If you find this enough to associate me with Keynes - whom I don't like - OK, then I will accept it: I may be agreeing with some of the Keynesian arguments, after all.
2. capitalism should be sustainable. There is some trade-off and some (or many) market players (or politicians) have surely made some recent errors in their estimates of the value of assets and risks. When I say that I completely believe the markets, I mean that I believe the principle of markets. I surely don't believe that every immediate decision or opinions of the market players - their weighted average - is guaranteed to be correct (or even accurate) and confirmed as wise in the future. When things fluctuate wildly, it is simply impossible to declare that the market was correctly quantifying the prices and values at both moments because the values are vastly different while the "objective" reality (as opposed to the "subjective" one) hasn't changed much. I think it should be admitted that the people are and have always been imperfect and a sufficient yet "small" number of "corrections" should be done so that people lose their desire (and power) to remove much more fundamental features of the market economy which is always a threat during an economic downturn.
But again, I understand where the statements (by Václav Klaus or some beloved members of the TRF community) that my comments about this issue were Keynesian or left-wing in character come from, and I am not going to be insulted. ;-)

Another person proves that the catastrophic acceleration of the global warming isn't slowing down.

Alcohol may have been involved. Thanks to Bob Ferguson! ;-)

Schmidt and the cool year 2008

By the way, as it is becoming increasingly more likely that 2008 is going to be the coldest year since 2000, Gavin Schmidt is scared to death that people could realize that the years of the 21st century saw mostly cooling. So he has emitted a huge amount of fog and emphasized that the new century began after December 31th, 1999 (and not on January 1st, 2001), because that was the only time when he was drunk like a pig (a statement that I, frankly speaking, don't believe).

## Tuesday, December 16, 2008 ... /////

### CKM matrix from F-theory

See these related articles:

F-theory GUTs
F-theory and experiments
Sweet SUSY from F-theory
Strings 2008: Tuesday (Vafa's talk)
Less than a month ago, I forgot to highlight the following cute paper:
Heckman, Vafa: Flavor hierarchy from F-theory
There exists a nice large collection of unexplained numbers in the Standard Model: the fermion masses or the Yukawa couplings, if you wish. They are pretty hierarchical, vastly different from each other, and have a lot of unexplained detailed features.

As far as the hierarchical character goes, people have been explaining them e.g. in terms of worldsheet instantons in string-theoretical braneworlds. The couplings are naturally exponentials of some negative areas (of triangular "disks"), and for reasonable distributions of the areas, you obtain an exponentially hierarchical distribution of the couplings.

In phenomenology, outside string theory, people often talked about Yukawa textures. These are guesses about the form of the mass terms in a particular basis where many elements of the matrices are strictly zero. Of course, in reality, they will never be strictly zero because they're not protected by any complete symmetries. But there might exist approximations in which they're zero and the structure of the couplings is then "qualitatively" explained.

## Monday, December 15, 2008 ... /////

### Steven Chu vs a sane homeowner

A few days ago, Marc Morano received some credit from a Joe Romm - the cheerleader-in-chief at recent wild orgies celebrating the death of Michael Crichton - for having determined that Steven Chu, the future U.S. secretary of energy, is not quite psychiatrically OK (much like many similar participants of the Poznań conference) when it comes to warmophobia and related disorders.

Well, your humble correspondent would like to modestly inform everyone that it is me, and not Marc Morano, who has figured it out. ;-) Thanks!

To see why Steven Chu is psychiatrically impaired, let us look at his new talk about the
... electrical wiring.
After a small fire in your house, a woman comes to your house and tells you that you have to pay $20,000 to get a new wiring, otherwise your house will burn in a few years at the 50% confidence level. Related: Veteran psychiatrist finds out that all left-wing people are mentally ill Chu's opinion is that it would be foolish to "look for" an expert who says that the new wiring is not necessary. Clearly, you must trust the woman and her first friend who says the same thing, he says: you have to pay$20,000. In the same way, the United States of America (and perhaps other countries as well) must immediately sacrifice a part of the national economy, too, in order to avoid the burning house - a planet, in this case - in a few years.

It's not his money, after all, so why wouldn't he sacrifice it? Why wouldn't he give up essential liberty to obtain a little temporary safety?

How an actual homeowner would think?

## Sunday, December 14, 2008 ... /////

### The roots of environmentalism

Many environmentalists seem to think that their movement is cool, new, original, and thought-provoking. They think that their "modern" ideas were invented by their widely promoted icons. It is hard to believe that they think so but some of them probably do. Well, the reality is very different. Similar ideas have been around for centuries and their incorporation within the modern industrial society began roughly seven decades ago.

Let me begin with the following quote:

"We recognize that separating humanity from nature, from the whole of life, leads to humankind's own destruction and to the death of nations. Only through a re-integration of humanity into the whole of nature can our people be made stronger. That is the fundamental point of the biological tasks of our age. Humankind alone is no longer the focus of thought, but rather life as a whole... This striving toward connectedness with the totality of life, with nature itself, a nature into which we are born, this is the deepest meaning and the true essence of ******** ********* thought."
Beautiful, isn't it? You may ask who wrote these sentences. Was it Jared Diamond in 2005? Or was it Al Gore in 1992? Or Rachel Carson in 1962? Or Alexander Ač in 2007? No, someone else was the author. It was Prof Ernst Lehmann, a leading German biologist.

## Saturday, December 13, 2008 ... /////

### Mathematica WeatherData: 17,168 stations

Click the picture to zoom in.

Would you recognize the pattern on this image? Well, yes, the axes are the longitude and latitude and you can see the continents, especially their industrialized subcontinents, on it.

The picture shows 17,168 weather stations across the world. You see that some regions are covered more densely than others. Mathematica 7 users have access to all the detailed current and historical weather data from these stations.

For example, you can pick a station in Florida and determine when its managers started their barbecue party last Sunday (most U.S. weather stations are cleverly attached to a grill, see wattsupwiththat.com).

## Friday, December 12, 2008 ... /////

### Obama is flooding NASA with annoying & incompetent women and men

Orlando Sentinel informed its readers about a subtle tension between the professionals at NASA on one side and members of Barack Obama's team who may have been sent to NASA to deliberately create problems on the other side.

Barack Obama doesn't find the U.S. space program important enough to talk to Mike Griffin in person. So instead, he has sent six people - led by Ms Lori Garver - to NASA to talk about the transition with Griffin.

Now, you should realize who Ms Lori Garver is. She has served as a lead space policy adviser to John Kerry, Hillary Clinton, and Barack Obama but she clearly has no engineering qualification to talk about the issues.

She received her Bachelors degree in Political Science and Economics from the Colorado College in 1983 and her Master degree in Science, Technology, and Public Policy from the George Washington University in 1989. Imagine a lot of politicized bullshiting about science and technology by a typical political appointee.

On the other hand, Mike Griffin has received seven degrees, including a PhD, that cover physics, aerospace engineering, business administration, electrical engineering, and civil engineering. This is not quite a silly anomaly because NASA kind of needs the people with a similar expertise at the top. Although the competence and other skills are not directly proportional to the number of degrees, the difference between this paragraph and the previous one is statistically significant and surely means something.

### Klaus: Climate issues are silly luxury good

Czech president hits at EU climate deal

PRAGUE, Dec 12 (AFP) - Czech President Václav Klaus hit out at the EU climate [20-20-2020-20-20] deal concluded Friday and described global climate issues as "a silly luxury."

"I do not like the way they forced it", Klaus said shortly after an agreement was announced in Brussels.

He also claimed that his French counterpart Nicolas Sarkozy had "pushed" the deal so that it would not be left when the Czech Republic takes over the EU presidency from France on January 1.

### Cyclic cosmology: motivation still unknown

Cyclic cosmology remains one of the research directions whose motivation and value looks utterly incomprehensible to your humble correspondent. Originally, I only wanted to write about another very weak article in Nude Socialist about Abhay Ashtekar's cyclic loop quantum cosmology but then I decided to be more general after squeehunter asked a question about the infinite cyclic cosmology.

The purpose of theoretical work

Let me begin with an explanation of my perspective on the value of a theorist's work. Good results in theory resemble the key and the lock:

You see, something fits together. The lock may be a set of experimental and observational data and the key is a theory with its calculations for the given situation. They often lead to the same result. The patterns agree. The lock may be opened.

Alternatively, the key and the lock may be two assumptions in our previous successful theoretical understanding of the world that were thought to be independent. A new insight may show that they are not independent, after all. They may become two manifestations of a deeper logic, of a more fundamental starting point. Theoretical work may find out that they only looked independent because the people in the past didn't think about the consequences of their own theories carefully enough.

## Thursday, December 11, 2008 ... /////

### Hippies want another IPCC to control the world's economy

Rafa has brought my attention to this text:

Can science help solve the economic crisis?
Four authors write a lot of neutral comments about the economy. However, the text escalates and at some moment, they announce that their goal is nothing less than to control the world's economy:
If this research succeeds then a discussion of whether a given financial instrument should be allowed or how it should be regulated should not be a matter of opinion or ideology. It should be based on detailed modeling and data taken from real world experiment and treated with the scrutiny brought to the introduction of a new airplane.

In the longterm, there needs to be an independent, non-partisan methodology for economic and financial modeling which involves globally agreed upon standards, as in the world of climate modeling. As in that world, one can imagine an international commission of economic scientists who develop, test and benchmark economic models against each other, and against past data, so that there is a reliable understanding of what the best models are and how reliable they are for studying different kinds of problems and predicting the impacts of proposed new economic and financial regulation. This will allow new proposals for innovative financial instruments or changes in trading rules or accounting rules to be tested in an open environment using best practices to understand their results.
Wow. This is just stunning. Make no mistake about it. People like Mr Lee Smolin, a hippie who is known by every physicist to be a crackpot, claim to own "models" that will "objectively" decide whether a financial instrument should be allowed. Opinions - except for theirs - will become obsolete. A new IPCC-like body is supposed to run these "models" and tell everyone what to do. I am simply speechless.

The IPCC has been one of the worst scandals in the history of the political manipulation of science. It is predominantly composed out of opportunists - who were attracted by an increasing funding of the pseudoscientific discipline of "climate change" - and by far-left political hacks who dream about abolishing the market economy and the industrial society in the world.

It is composed out of dishonest jerks such as Michael Mann who always prefer to expand their lies and frauds by another order of magnitude over admitting them and fixing them. It is led by people like Rajendra Pachauri who just said in the Guardian:
I refuse to accept that a few papers are in any way going to influence the long-term projections the IPCC has come up with.
In other words, Pachauri is saying that he is and his comrades are fanatical blinded religious zealots who will pay no attention to any new evidence and who will allow no progress in science - just like the Inquisition did not - until someone will remove them. (Thanks, Willie.)

The IPCC is a body whose predictions have been universally falsified by the evidence (they predicted a huge warming in the last 10 years, there's been no warming at all), an institution that has played a key role in developing the tumor in the society that has swallowed roughly 2% of the world's economy it covers by this moment. They have planned the prices of the carbon indulgences but these prices unexpectedly for them dropped by 3 orders of magnitude at some moment. These people are dangerous imbeciles. Make no mistake about it: the IPCC is a gigantic piece of collective biological waste, a group of power-thirsty sub-par pseudoscientists, and the main exponents of this organization should be put in jail.

And now, you have four self-confident revolutionaries - one of them has been unable to learn the undergraduate quantum mechanics for 55 years even though he's been paid as a physicist - who claim to have everything they need to control not the 2% of the world's economy, like the IPCC, but 100% of the world's economy, without paying any attention to the opinions of other people on this planet. I am telling you: it is impossible to control the world economy without paying attention to other people unless you want to become another group of dictators who are completely legitimate targets for assassination.

Even if it were possible to write down computer models that could predict anything about the economy - and it is clearly impossible (and it will always be) - it would still not be enough to decide which policy is actually the right one because such decisions always depend on subjective moral judgment of what is good and what is bad. Moreover, any kind of "insider information" always means an opportunity for a dirty profit (via actions that would make the predictions inaccurate, anyway).

You're playing far too dangerous a game, Ladies and Gentlemen. It's a game about the very fate of democracy in this world. What I am amazed by is the breathtaking arrogance with which they use various words. For example, they think that their efforts are "non-partisan". If you're non-partisan, why are you proposing plans about the central regulation of the world that would make even Karl Marx's dreams look like modest centrist policies in comparison? Why are so many of you hippies all the time?

The recent financial turmoil was partly caused by overly self-confident "intellectuals"employed as traders and bankers who thought that they could predict anything just because they were "intellectuals" who could use "computer models", but in reality, they were not even able to reproduce basic common sense of ordinary traders because, as it turns out, being an "intellectual" actually isn't enough for being any good. At this moment, I would expect these people to ask their parents or wives for a proper spank rather than trying to inflate their crazy desire to control the world to unprecedented proportions.

### Steven Chu, a new energy secretary

Steven Chu, the 1997 physics Nobel prize winner for laser cooling, is likely to be picked by Barack Obama as the new secretary of energy: CNN, Google News.

This is surely a bold - or crazy - experimental move because Chu's political experience is probably negligibly small. It may backfire.

But I admit, picking a famous experimental physicist in politics is the kind of experiments that I find intriguing. Expect lasers everywhere. And the guys from AMO physics may perhaps expect increasing grants from the Department of Energy (DoE). ;-)

When it comes to climate change, Steven Chu is a nutcase just like everyone else who could have been considered by Obama. If you ask me whether I am surprised that the new energy secretary is going to be an alarmist nutcase, the answer is No, I am not surprised. ;-) Still, I wish America that he will be forced to realize that this insane postmodern religion is not the bulk of things he needs to do his job.

Useful wisdom for readers-schoolkids: Homework causes global warming
Hat tip: Gordon W.

## Wednesday, December 10, 2008 ... /////

### Eichler et al.: Half of recent warming was solar

In this dose of peer-reviewed skeptical climatological literature, we follow Climate Research News. The blog was intrigued by a new article in Geophysical Research Letters that was accepted on Friday, December 5th.

Eichler, A., S. Olivier, K. Henderson, A. Laube, J. Beer, T. Papina, H. W. Gäggeler, and M. Schwikowski: Temperature response in the Altai region lags solar forcing
Recall that the Siberian Altai Mountains are found at the intersection of Russia, China, Mongolia, and Kazakhstan.

The authors looked at 750 years worth of the local ice core, especially the oxygen isotope. They claim to have found a very strong correlation between the concentration of this isotope (i.e. temperature) on one side and the known solar activity in the epoch 1250-1850. Their data seem to be precise enough to determine the lag, about 10-30 years. It takes some time for the climate to respond to the solar changes.

It seems that they also have data to claim that the correlation gets less precise after 1850. They attribute the deviation to CO2 and by comparing the magnitude of the forcings, they conclude that "Our results are in agreement with studies based on NH temperature reconstructions [Scafetta et al., 2007] revealing that only up to approximately 50% of the observed global warming in the last 100 years can be explained by the Sun."

## Tuesday, December 09, 2008 ... /////

### Fast comment transition: HaloScan to JS-Kit

The provider of the fast comments on this blog, HaloScan, has been acquired by JS-Kit a few months ago. This transaction will force all HaloScan users to switch their comment systems into JS-Kit. I have just clicked at "Upgrade Me Now".

The new threads, such as one below this article, should already be using the new system even though at the moment when this sentence was being written, I had no idea whether it would work. The older threads would be upgraded later.

I have no experience with the new system but if some of the issues about the system are counter-intuitive, your humble correspondent and the more skillful readers will try to help others in making things work. The JS-Kit people should help, too.

Only once the old fast comments are transferred to the new JS-Kit platform, we will regain the tools to reconfigure the styles. Also, some donations may be needed to cover some fees because TRF will probably (significantly?) exceed the limit of 25,000 fast comment impressions per month.

## Sunday, December 07, 2008 ... /////

### Zuzana Norisová: Š Š Š Šepotám (I Whisper)

Original: Nancy Sinatra: Sugar Town, 1967 (lyrics)
Source: "Rebelové" (Rebels), a Czech 2001 retro-movie
Actress/singer: Ms Zuzana Norisová (*1979), Slovakia

### Relativistic and particle-physics cultures

Recently, I've heard many people talking about the "cultures" in theoretical physics and quantum gravity. The two most important "cultures" in the field of quantum gravity are the "relativists" and the "particle physicists". The assumption is that the "relativists" consider the Einsteinian tradition of classical general relativistic theories to be more important and want to add the quantum features as a "detail" while the "particle physicists" build on quantum field theory - that's been very useful to describe particle physics - and want to properly add gravity to it.

But people also tend to assume that the two groups should naturally have different answers to well-defined questions. For example, if someone belongs to the "relativistic culture", he or she is allowed to "think" that it is the singularity, not the horizon, where the solution to the information loss paradox must start.

## Saturday, December 06, 2008 ... /////

### Václav Klaus resigns as the ODS honorary chairman

This Friday was a nice day. I went to Prague to see an enthusiastic talk of a former colleague of mine, MG, and to spend some pleasant time with him or her, but if you allow, we will keep the private and public things separated.

Among the public events, amusingly enough, I met a Czech X Factor finalist, Ms Kamila Nývltová (search), in the subway. Some regular readers will surely remember this young woman.

I didn't want to create a scandal so I didn't talk to her in the crowded wagon: no one else did either - the privacy of stars and starlets seems to be protected much more than I expected.

## Thursday, December 04, 2008 ... /////

### Black hole singularities in AdS/CFT

Moshe Rozali wrote an innocent article about the "hometown" of the gauge theory in the AdS/CFT correspondence. Where does it live?

We think of gravity as being defined in the bulk of the space - by variables such as g_{mn}(t,w,x,y,z) - while the gauge theory is living on the lower-dimensional boundary, being made out of fields like F_{mn}(t,x,y,z). But as Moshe explains, this is just an artifact of a choice of variables. Both theories are physically equivalent so we should say that they "live" on the same space.

When the bulk is large enough, it is better to imagine that both (equivalent) theories live in the bulk. When the gauge theory is weakly coupled, it is more natural to imagine that both (equivalent) theories live on the boundary and there is no bulk. However, this comment by Moshe became just a boundary of a more extensive discussion whose bulk focused on something different, namely a question by Bee:

What happens with black hole singularities in the AdS/CFT correspondence?

A detailed terminological convention: on this blog and all the threads, "anti de Sitter space" means the covering space of the hyperboloid shape - a toilet paper that is wound around the hyperboloid infinitely many times. This AdS space has no closed time-like curves. Moderating police will enforce that you use a different word for the hyperboloid with closed CTCs.

## Wednesday, December 03, 2008 ... /////

### CCNet: Eight articles about the climate socialism

Benny Peiser is sending us interesting stuff. Send an e-mail to listserver@livjm.ac.uk with "subscribe cambridge-conference" or "unsubscribe cambridge-conference" in the body.

1. China View: Ten thousand EU workers protest in Brussels against the "climate" plans to cripple Europe's steel industry
2. PhysOrg: German carmakers denounce the EU "compromise" on CO2 emissions
3. World Climate Report: Will one of the 10,000 participants of the Poznan climate conference notice that there hasn't been any warming for 10 years?
4. Deutsche Welle: Václav Klaus, a leading AGW "doubter", will become more visible during the Czech EU presidency
5. Investor's Business Daily: Cooling down: people will realize that there exist serious issues, too
6. Climate Progress: Maybe, Obama is not the ultimate green messiah, after all
7. WSJ blog: Analysts are scrabling to dampen already low expectations in the Poznan summit
8. Orange Punch: The Terminator and friends have edited their warming books to make his heroic struggle to terminate climate change look much cheaper
Bonus from your humble correspondent: Michael Mann's hockey stick from Brownian noise

As a part of the refreshing of my basic Mathematica skills, I've created this simple self-explanatory Mathematica notebook explaining why Michael Mann gets the hockey stick even from random data - Brownian noise.

In order to make the effect really nice and obvious, I first prepare 5,000 random Brownian temperature proxies, obtained by a resummation of random independent numbers between -0.5 and +0.5 over time. Click the picture below to zoom in.

In the second step, I create "instrumental" 20th century data. To simplify a bit and extract the qualitative message of this whole homework, I assume that the temperature was increasing linearly. At this moment, I am ready to compute the correlation coefficients of each of the 5,000 proxies with the "instrumental" temperature data. The average temperature of the proxies, weighted by the correlation coefficients - telling you how "good" the proxy is according to Michael Mann - is drawn below: click to zoom in.

What we're doing is completely obvious. We're choosing the "good" and "important" proxies by their having an unusual 20th century trend, without paying any attention to their behavior in the previous centuries. It follows that the behavior of the random proxies before 1900 averages to zero while the selection criterion for the 20th century survives. The result is inevitably a hockey stick.

Let me emphasize that we have entered random data from a virtual world where the temperature in the 20th century had the same variability as the temperature in the previous centuries. Nevertheless, the Mannian method has transformed the random data into a hockey stick. That's the simplest way, due to M&M, to prove that Mann's methodology is complete rubbish.

If you're worried about the linear 20th century, it doesn't really matter because the 20th century trend was pretty similar to the linear function and with the exactly measured 20th century temperatures, we would obtain (and Mann obtained) qualitatively similar data. Still, the appearance of the hockey-like graph clearly doesn't mean that the 20th century was any special: in our world, we were very careful to guarantee that the 20th century was generic and ordinary.

Using Mann's method, you get the hockey stick if the data are random and unrelated to the temperature. But even if the data are correlated with the temperature, it is easy to see that the resulting hockey stick doesn't imply that the real temperatures looked like a hockey stick. In fact, the temperatures could have been linearly increasing from the year 1000 to 2000 - imagine that you add this "real" linear function to all the proxies. The result, using Mann's method, would still have the hockey stick, superimposed onto a negligible linear trend. You can play with the program yourself. If you add any "real temperature profile" to the Brownian motion, Mann's method still gives you the "real temperature profile" plus (superimposed on) the hockey stick (that comes from the random contribution to the proxies, more precisely from the bad proxies that were overrepresented because they agreed with a warming trend "by chance").

To put it simply, Mann misinterprets the 20th century warming as a proof that the warming was unprecedented, uses this misinterpretation to select proxies, and "surprisingly" derives his assumptions back. If you have Mathematica, you may download the notebook here:
mann-hockey-fun.nb

### Dyson spheres and Fermi paradox

Let me postpone the serious part of this posting. ;-)

As you know, we are surrounded by extraterrestrial aliens. The Drake equation proves that the intelligent life must arise almost everywhere. However, we haven't seen any extraterrestrial friends yet. The question "where are they?" is known as the Fermi paradox.

Clearly, they must be hiding. Why?

Well, as you know, the fossil fuels are a global problem. All extraterrestrial civilizations realize that it is a problem they must wrestle with. Moreover, they need the optimum kind of energy. Most of them choose solar panels and they surround their whole star by solar panels, to capture all the emitted energy.

Still, the large artificial sphere surrounding the star - a Dyson sphere - is eventually heated to a new temperature. Its thermal radiation emits the same total energy (from the whole surface) as the star. You can see that the total power emitted per unit time

T4 R2 = const.
The fourth power of temperature comes from the well-known black body laws and the squared radius is the surface area. Note that the temperature goes like the inverse square root of the radius.

For example, the surface of the Sun has temperature around 5,000 K and it is 2 light seconds from the center. However, the Earth is around 500 light seconds from the Sun, about 250 times further than the surface. The corresponding temperature is therefore sqrt(250) = 15+epsilon times lower than the Sun's surface temperature. Numerically, 5000 K/15 = 300+epsilon K, close to the observed average temperature on the Earth. (You would have to deal with the albedo and the absorption by the atmosphere to get more accurate results.)

Let me use the figure 0 °C = 273.15 K for the temperature at the Earth's distance from the Sun to simplify the numbers. ;-)

## Tuesday, December 02, 2008 ... /////

### Mathematica 7

A very important person (VIP) has kindly allowed me to check the newly released Mathematica 7. See

Wolfram.COM.
It is a very impressive program (buy!). Happily enough, the notebooks from older versions of Mathematica seem to work. The new system offers you to upgrade certain obsolete commands in your old notebooks automatically but the new dialect is unlikely to affect simple enough "classical" mathematics, anyway.

To see some of the abilities of the new Mathematica, see
Demonstrations.Wolfram.COM
• Search the previous web e.g. for surface and browse for a while
Reference.Wolfram.COM (standard help pages)
Screencasts (short educational videos, try this 2-minute one)
The Learning Center (screencasts, seminars, tutorials)
MathWorld (a Wikipedia-like math encyclopedia with lots of technical references and many Mathematica notebooks)
Blog.Wolfram.COM
From the last website I mentioned, let me recommend you e.g. this article about image processing - a new set of capabilities besides built-in parallel computing, geodesy & GIS, and other new things:

### La Niña may be returning

La Niña, a Pacific atmospheric phenomenon that ended during the summer, to be replaced by ENSO-neutral conditions, shows some signs of life again.

Click the picture above for more maps. The weekly status (click PDF or PPT) indicates that the ENSO region 1+2 has a -0.9 °C anomaly (page 5/30). The regions 3, 3.4, and 4 have -0.4 °C which is close to -0.5 °C, the official cutoff for the La Niña regime (decided according to the 3.4 region).

If La Niña returns, expect more global cooling to be more likely than global warming. Plan for more snow in Colorado and many other things. The cool phase of the PDO (Pacific Decadal Oscillation) could bring more frequent La Niñas in the next 20-30 years and less frequent El Niños and take the global temperature down.

More news about the climate change

The climate conference began in Poznan, Poland. The bureaucrats will try to convince each other that they should negotiate a Kyoto II treaty in Copenhagen in 2009. Pressures from Italian, Polish, German, and other economies are fortunately likely to dilute any proposed plans.

The Telegraph (U.K.) explains that
President-elect Barack Obama proposes economic suicide for U.S.
Well, if you found out that he is not a real American, it would be homicide, after all. Incidentally, it was recently found that the wind mills and turbines built across the U.S. can substantially alter the character of storms. So far this form of energy generates 1% of the U.S. electricity so any such effect is negligible. But the wind turbine's deadly ice shower could matter.

### Heat expansion of the spectral action and loop diagrams

Ali Chamseddine and Alain Connes have a new paper,

The uncanny precision of the spectral action,
which argues that under some assumptions they find worth considering, two terms in an expansion of an action give the correct initial 6820 decimal places of an action.

It's a typical paper where I feel that there is something extremely cool and exciting going on, but once I spend ten minutes with each such thing, it seems to evaporate. Recall that they want to write a theory of everything as a simple system in noncommutative geometry. The action is
S = Tr [ f(D/Lambda) ]
It's the so-called spectral action. The trace should probably be taken over a first-quantized (one-particle) Hilbert space only, generating the classical spacetime action of a field theory in some way. Here, "D" is the Dirac operator - including all dimensions they consider.

The letter "Lambda" stands for a cosmological constant. You would think that it is extremely small but they actually study "Lambda goes to infinity" limit. That's bizarre and I am afraid that you won't find any justification of such an approach in the paper but some other things are fun so you shouldn't stop reading yet.

## Monday, December 01, 2008 ... /////

### Background independence in AdS spaces

Moshe Rozali opened his and David Berenstein's blog to a discussion of background independence (BI) and emergent character of gravity, especially in the context of the anti de Sitter (AdS) space. As explained in that thread, the following facts are important:

• states in a theory of quantum gravity with different asymptotic conditions than the AdS space are physically disconnected; they're in different superselection sectors
• states within the same superselection sectors allow any physical configurations "in the bulk", i.e. inside the space defined by the boundary, to evolve; all physically conceivable configurations in the "bulk" are included in the gauge theory; the latter is therefore at least as background independent as general relativity
• Riemannian geometry, strings, string fields, and/or branes are just approximate, emergent degrees of freedom in this context; they're no longer fundamental, universally valid, or leading to a known exact description of physics
• gauge theory is the fundamental description of all physical phenomena in the superselection sector and it is defined beyond any perturbative expansion and beyond other limits
• while this gauge theory can be found as a limit of another string theory, it can also be formulated completely independently of string theory, which is the philosophy relevant for the AdS/CFT correspondence
• there is additional, virtually unquestionable evidence that string theory is more background-independent: it inevitably makes topology transitions legal, and leads to the exact equivalences of physical phenomena at geometrically vastly and qualitatively different backgrounds (dualities)
Let me discuss these points one by one.

Superselection sectors

In a theory of gravity, extending general relativity, the spacetime may have many different shapes. The space may get curved or less curved, approximate event horizons may be created for a while, the shape (and topology) of internal dimensions of space may change.

format: plain


text:
# Both Quadratic and Linear Drag

1. Jan 27, 2008

### Col.Buendia

An object is coasting on the horizontal axis, in the positive direction and is subject to a drag force f = -bv - cv$$^{2}$$.
Write down Newton's 2nd Law and solve for v using separation of variables.

So first I wrote out Newton's law as:
F= m(dv/dt) = -bv - cv$$^{2}$$

Solving the integral: dt = $$\frac{dv}{-bv-cv^{2}}$$, with boundaries from 0 to t and v(0) to v

I got: t = $$\frac{-m}{b}$$ ln$$\frac{v}{1+\frac{c}{b}v^{2}}$$

Note: I haven't put in my boundaries on v yet. However, Once I put in my boundaries on v and try to rearrange to solve for v, I can't get anywhere. Any suggestions or help would be greatly appreciated.

Thx, CB

2. Jan 28, 2008

### CompuChip

Are you sure about the ln? If I differentiate it, I first get
$$\frac{ 1 + (c/b) v^2 }{ v }$$
times the derivative of that (chain rule!) which will be something like (... - ...) / v^2
in total giving me something containing 1/v^3.

If you want to do it analytically, you could try writing
$$\frac{-dv}{v} \frac{1}{b + c v}$$
as
$$\left( \frac{A}{v} + \frac{B}{b + c v}\right) dv$$
with A and B constants (which, in this case, works). Then split the integral and solve both parts separately.

3. Jan 28, 2008

### Col.Buendia

Well looks like I made an error in my calculations: the integral turns out to be :
t =$$\frac{-m}{b} \frac{1}{b + c v}$$ ln$$\frac{v}{1+\frac{c}{b}v}$$

And yes, using partial fractions will also solve this integral, and yes a ln function will turn out to be there.

Anyway, then the solution is solved for just rearranging for v in terms of t.


text:
zbMATH — the first resource for mathematics

Oscillatory second order linear difference equations and Riccati equations. (English) Zbl 0619.39005
A nontrivial solution of the equation $$c_ nx_{n+1}+c_{n-1}x_{n- 1}=b_ nx_ n$$, $$c_ n>0$$, $$b_ n>0$$, is called oscillatory if for every $$N>0$$ there exists $$n\geq N$$ such that $$x_ nx_{n+1}\leq 0$$. Either all nontrivial solutions are oscillatory or none are. Authors’ abstract: Oscillation criteria are established for the equation $$c_ nx_{n+1}+c_{n-1}x_{n-1}x_{n-1}=b_ nx_ n$$, $$c_ n>0$$, involving asymptotic behavior of the quantity $$\alpha_{n,m}=4\prod^{m}_{j=0}(4q_{n+j})^{-1},$$ where $$q_ n=c^ 2_ n/(b_ nb_{n+1})$$. We also show that the given equation is oscillatory if $$y_{n+1}+y_{n-1}=(q_ n^{-1}-1)y_ n$$ is oscillatory. This result is then employed to obtain several new oscillation criteria. Riccati difference equations are used to prove the basic results.
Reviewer: K.Cooke

MSC:
 39A10 Additive difference equations 39A12 Discrete version of topics in analysis
Full Text:


text:
## Algebra: A Combined Approach (4th Edition)

$\frac{9}{5}\times\frac{1}{3}-\frac{1}{3}=\frac{4}{15}$
Recall the order of operations, "Parentheses first, Exponents second, Multiplication and Division third(from left to right), and Addition and Subtraction fourth(from left to right)". So, first we do, $\frac{9}{5}\times\frac{1}{3}$ ,giving us $\frac{9}{15}$ Then, we see that the remaining two fractions do not share the base but must be subtracted, so we must find the least common denominator. In this case, we multiply the numerator and denominator by 5 for the fraction $\frac{1}{3}$ so that it may have the least common denominator of 15. $\frac{9}{15}-\frac{1}{3}\times\frac{5}{5}=\frac{9}{15}-\frac{5}{15}=\frac{4}{15}$


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## CCC '20 J4 - Cyclic Shifts (Hard)

View as PDF

Points: 12 (partial)
Time limit: 0.4s
Java 0.6s
Python 0.7s
Memory limit: 512M

Author:
Problem type

This is an extension of ccc20j4. In this version constraints are higher. You can make hacks only if all versions of the problem are solved. Hacks are no longer being accepted.

Thuc likes finding cyclic shifts of strings. A cyclic shift of a string is obtained by moving characters from the beginning of the string to the end of the string. We also consider a string to be a cyclic shift of itself. For example, the cyclic shifts of ABCDE are:

ABCDE, BCDEA, CDEAB, DEABC, and EABCD.

Given some text, , and a string, , determine if contains a cyclic shift of .

#### Input Specification

The input will consist of exactly two lines containing only uppercase letters. The first line will be the text , and the second line will be the string .

##### Subtask 1 [90%]

Each line will contain at most characters.

##### Subtask 2 [10%]

Each line will contain at most characters.

Tip: the intended solution runs well within the time limit without constant optimization.

#### Output Specification

Output yes if the text, , contains a cyclic shift of the string, . Otherwise, output no.

#### Sample Input 1

ABCCDEABAA
ABCDE

#### Output for Sample Input 1

yes

#### Explanation of Output for Sample Input 1

CDEAB is a cyclic shift of ABCDE and is contained in the text ABC CDEAB AA.

#### Sample Input 2

ABCDDEBCAB
ABA

#### Output for Sample Input 2

no

#### Explanation of Output for Sample Input 2

The cyclic shifts of ABA are ABA, BAA, and AAB. None of these shifts are contained in the text ABCDDEBCAB.

## Comments

• commented on Jan. 30, 2022, 8:44 a.m. edit 4

Can this be solved using Python within the time limits? No accepted solutions for python or pypy exist.

 I see that there is an explicit time limit for python which suggests it ought to be solvable.

I'm stuck on 90%. Getting TLE on 2nd problem in part 3.

• commented on Jan. 29, 2022, 7:17 a.m.

A mystery to solve: why can't I exit() in python? I get NameError if I exit() rather than use logic to control program flow.

• commented on Jan. 29, 2022, 7:55 a.m.
• commented on Jan. 30, 2022, 8:45 a.m.

That would explain it :)

• commented on Jan. 30, 2022, 10:04 a.m.

you can still use sys.exit(0) however


text:
edit

Grove - Infrared Reflective Sensor

Grove - Infrared Reflective Sensor is used to detect the presence of an object within a specific range. The sensor consists of an IR LED and a photosensor (phototransistor) pair. The light emitted by the IR LED gets reflected by any object placed in front of the sensor and this reflection is detected by the photosensor(phototransistor). Any white (or lighter) colored surface reflects more than black (or darker) colored surface.

When the reflected light is detected, it produces Digital LOW (or Binary 0) output on the SIG pin. The on-board LED indicator will also glow. If no reflection is detected or if the object is too far from the sensor, the output on the SIG pin stays at Digital High (Binary 1). The on-board LED indicator will be off as well. The detectable range of this sensor is 4–16 mm. The module incorporates a Rail-to-Rail Operational Amplifier to amplify the output of phototransistor. There is a potentiometer which can be used to adjust the gain of the amplifier, that is, sensitivity of detection.

With this sensor, you can build the following (but not limited to) applications: line following robots, optical encoders and object counting applications.

Caution

This product is also mildly sensitive to non-IR radiations and hence any bright light on photosensor impairs or disturbs IR light detection.

Version Tracker¶

Product version Changes Release date
Versions older than v1.2 Initial June 2012
Version 1.2(current version) Optimized layout April 2016

Features¶

• Grove compatible and easy to use
• Highly sensitive and reliable
• Small footprint
• Adjustable sensitivity for different occasions

Tip

Specifications¶

Parameter Value
Operating voltage(V) 3.3–5V
Operating current(mA) 14.69–15.35 mA
Effective detectable distance 4–15 mm
Response time 10 μs
Phototransistor: Peak sensitivity wavelength 800 nm
IR LED: Peak light emitting wavelength 940 nm
Reflective photosensor datasheet
Output operational amplifiers datasheet
Weight 4 g

Platforms Supported¶

Arduino Raspberry Pi

Caution

The platforms mentioned above as supported is/are an indication of the module's software or theoritical compatibility. We only provide software library or code examples for Arduino platform in most cases. It is not possible to provide software library / demo code for all possible MCU platforms. Hence, users have to write their own software library.

Hardware Overview¶

• RPR220 Reflective photosensor - Highly sensitive reflective photosensor.
• LMV358 - rail-to-rail operational amplifier.
• LED Indicator - The LED will switch on when the received infrared light intensity exceeds a preset level.
• Light sensitivity adjustment potentiometer - adjust the sensitivity of photosensor to light.

Getting Started¶

Let us see how to implement few basic applications with this module:

Play With Arduino¶

Line Following¶

This sensor can be used to help a robotic car follow a black line.

Hardware¶
• Step 1. Prepare the following materials:
Seeeduino V4.2 Base Shield Grove - Infrared Reflective Sensor White paper and black pen
Get One Now Get One Now Get One Now 🙂
• Step 2. Connect Grove - Infrared Reflective Sensor to any port of Grove-Base Shield via the Grove cable, we use D2 in this demo.

• Step 3. Place this sensor 12mm above the white(or other bright color) paper.

• Step 4. Adjust the potentiometer with a screwdriver to change the sensitivity of reflective photosensor, until the LED indicator glows. As your rotate clockwise, the reflective photosensor will be more sensitive to light.

Note

Use a proper screw-driver to adjust the tiny potentiometer. Applying heavy pressure or frequent adjustments might damage the wiper of the potentiometer.
• Step 5. Maintain the vertical distance, move the sensor horizontally towards the black line. The indicator LED should go off over the black line. If it is still on, adjust the potentiometer until it is off.

Rotary Speed Detection¶

Let us implement simple optical encoder to detect the speed of a motor

Hardware¶
• Step 1. Prepare the following materials:
Seeeduino V4.2 Base Shield Grove - Infrared Reflective Sensor 3V/5V DC Motor
Get One Now Get One Now Get One Now Get One Now
• Step 2. Connect the Infrared Reflective Sensor to the D2 port of Grove - Base Shield and connect the motor to the D6 (In fact, you can just connct VCC and GND to power the motor).

• Step 3. Attach a round, white paper plate (with a black line marked on it) to the motor. Place the sensor near this rotatory encoder. Run the motor.

Software¶
• Step 1. Download the library Arduino timer1 library and add it into the libraries file of Arduino IDE. A guide about how to run our demo code.

• Step 2. Refer to How to install library to install library for Arduino.

• Step 3. Open a new sketch, and copy the following code into the sketch.

unsigned int counter=0;
{
counter++;
}
void timerIsr()
{
Timer1.detachInterrupt();  //disable the timer1
Serial.print("The speed of the motor: ");
Serial.print(counter,DEC);
Serial.println("round/s");
counter=0;
Timer1.attachInterrupt( timerIsr );  //enable the timer1
}
void setup()
{
Serial.begin(9600);
Timer1.initialize(1000000); // set a timer of length 1sec
Timer1.attachInterrupt( timerIsr ); // attach the service routine here
}
void loop()
{

}

• Step 5. Open the Serial Monitor of Arduino IDE by click Tool-> Serial Monitor. Or tap the Ctrl+Shift+M key at the same time. if every thing goes well, you will get the speed.

Play With Raspberry Pi¶

Hardware¶

• Step 1. Prepare the following materials:
Raspberry pi GrovePi_Plus Grove - Infrared Reflective Sensor
Get One Now Get One Now Get One Now
• Step 2. Plug the GrovePi_Plus into Raspberry.

• Step 3. Connect Grove - Infrared Reflective Sensor to D4 port of GrovePi_Plus.

• Step 4. Connect the Raspberry to PC via USB cable.

Software¶

Tip

In this wiki we use the path ~/GrovePi/ instead of /home/pi/Desktop/GrovePi, you need to make sure Step 2 and Step 3 use the same path.

Note

We strongly suggest you to update the firmware, or for some sensors you may get errors.

• Step 3. Git clone the Github repository.
cd ~
git clone https://github.com/DexterInd/GrovePi.git

• Step 4. Check the code.
cd ~/GrovePi/Software/Python
sudo nano grove_infrared_reflective_sensor.py

Then the code should be like:

import time
import grovepi

# Connect the Grove Infrared Reflective Sensor to digital port D4
# SIG,NC,VCC,GND
sensor = 4

grovepi.pinMode(sensor,"INPUT")

while True:
try:
# Sensor returns HIGH on a black surface and LOW on a white surface
print "black surface detected"
else:
print "white surface detected"

time.sleep(.5)

except IOError:
print "Error"

Then tap Ctrl+X to quit nano.

• Step 5. To run the demo, execute the following command in terminal:
sudo python grove_infrared_reflective_sensor.py

The result should be like:

pi@raspberrypi:~/GrovePi/Software/Python \$ sudo python grove_infrared_reflective_sensor.py
black surface detected
black surface detected
black surface detected
black surface detected
black surface detected
white surface detected
white surface detected
white surface detected
black surface detected
black surface detected
black surface detected
black surface detected
black surface detected
black surface detected

Tech Support¶

Please submit any technical issue into our forum.


text:
BOTTOM, CHARMED MESONS($\boldsymbol B$ = $\boldsymbol C$ = $\pm{}$1) ${{\mathit B}_{{c}}^{+}}$ = ${\mathit {\mathit c}}$ ${\mathit {\overline{\mathit b}}}$, ${{\mathit B}_{{c}}^{-}}$ = ${\mathit {\overline{\mathit c}}}$ ${\mathit {\mathit b}}$, similarly for ${{\mathit B}_{{c}}^{*}}$'s INSPIRE search

# ${{\boldsymbol B}_{{c}}{(2S)}^{\pm}}$ $I(J^P)$ = $0(0^{-})$

Quantum numbers neither measured nor confirmed.


text:
# What is Gleason theorem about

1. Jan 9, 2004

### thankqwerty

Hi all, i'm doing a modcule on Quantum Logic and there is this Gleason theorem but the lecturer didnt explain it clear enough, can somebody help me out please?

sorry that i really have no idea what it is about, all i've got is a heading "gleason theorem" in my note, then it started going on talking about logic of all hilbert subspaces.... then go to introduce pure quantum states and convex combination of pure states.....

thank you

2. Jan 9, 2004

Staff Emeritus
I think you will find what you want in this paper. I found it by googling on gleason's theorem.

3. Jan 14, 2004

### slyboy

Gleason's theorem

Gleason's theorem is a derivation of the quantum probability rule from the structure of observables in quantum theory. It has two assumptions:

1. Assume that observable quantities are represented by Hermitian observables and that the possible outcomes are represented by the projectors in the spectral decomposition of such operators.

2. Assume that the probability is a function of the projectors only, i.e. it does not depend on which observable the projector came from. This is called non-contextuality.

Conclusion: There is a density operator representing the quantum state, with measurement probabilities given by the standard probability rule.

The theorem holds in Hilbert sapces of dimension 3 or larger, so interestingly it does not hold for the spin of a spin 1/2 particle. However, a POVM version of the theorem has been proved which does hold for these cases.

4. Jan 15, 2004

### thankqwerty

thank you very much


text:
Euclid's Lemma/Proof 2

Theorem

Let $a, b, c \in \Z$.

Let $a \divides b c$, where $\divides$ denotes divisibility.

Let $a \perp b$, where $\perp$ denotes relative primeness.

Then $a \divides c$.

Proof

Let $a, b, c \in \Z$.

We have that $a \perp b$.

That is:

$\gcd \set {a, b} = 1$

where $\gcd$ denotes greatest common divisor.

From Bézout's Lemma, we may write:

$a x + b y = 1$

for some $x, y \in \Z$.

Upon multiplication by $c$, we see that:

$c = c \paren {a x + b y} = c a x + c b y$

Now note that $c a x + c b y$ is an integer combination of $a c$ and $b c$.

So, since:

$a \divides a c$

and:

$a \divides b c$

it follows from Common Divisor Divides Integer Combination that:

$a \divides \paren {c a x + c b y}$

However:

$c a x + c b y = c \paren {a x + b y} = c \cdot 1 = c$

Therefore:

$a \divides c$

$\blacksquare$

Source of Name

This entry was named for Euclid.


text:
# Why t3 , t8 plane ?

preet0283
in sampling about the flavor u,d,s ...we use the t3, t8 generators amd plot all the possible combinations of their eigen values ...and then define u ,d , s...
i want 2 ask that why specifically these 2 SU(3) generators are used t o
define flavors?
I have vague answers 2 this question but m not satisfied with those ...

You posed a bit of a vague question, you might want to reformulate it.

But I think the answer you are looking for is that that the up and down quark are much better symmetry partners (to a great approximation they are eigenstates of isospin symmetry, which the mass of the strange quark spontaneously breaks).

Gold Member
preet0283 said:
in sampling about the flavor u,d,s ...we use the t3, t8 generators amd plot all the possible combinations of their eigen values ...and then define u ,d , s...
i want 2 ask that why specifically these 2 SU(3) generators are used t o
define flavors?
I have vague answers 2 this question but m not satisfied with those ...


text:
# zbMATH — the first resource for mathematics

##### Examples
 Geometry Search for the term Geometry in any field. Queries are case-independent. Funct* Wildcard queries are specified by * (e.g. functions, functorial, etc.). Otherwise the search is exact. "Topological group" Phrases (multi-words) should be set in "straight quotation marks". au: Bourbaki & ti: Algebra Search for author and title. The and-operator & is default and can be omitted. Chebyshev | Tschebyscheff The or-operator | allows to search for Chebyshev or Tschebyscheff. "Quasi* map*" py: 1989 The resulting documents have publication year 1989. so: Eur* J* Mat* Soc* cc: 14 Search for publications in a particular source with a Mathematics Subject Classification code (cc) in 14. "Partial diff* eq*" ! elliptic The not-operator ! eliminates all results containing the word elliptic. dt: b & au: Hilbert The document type is set to books; alternatively: j for journal articles, a for book articles. py: 2000-2015 cc: (94A | 11T) Number ranges are accepted. Terms can be grouped within (parentheses). la: chinese Find documents in a given language. ISO 639-1 language codes can also be used.

##### Operators
 a & b logic and a | b logic or !ab logic not abc* right wildcard "ab c" phrase (ab c) parentheses
##### Fields
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Biharmonic submanifolds in spheres. (English) Zbl 1038.58011

Harmonic maps $\phi$ are critical points of the energy functional $E\left(\phi \right)={\int |d\phi |}^{2}$, and $\phi$ is harmonic if and only if $\tau \left(\phi \right)=0$, where $\tau \left(\phi \right)$ is the tension field of $\phi$. Biharmonic maps are critical ones of the bienergy functional ${\int |\tau \left(\phi \right)|}^{2}$.

The authors study biharmonic maps into a manifold $N$ of constant curvature, in particular an $n$-dimensional standard sphere. This paper consists of two parts: (1) non-existence results of non-harmonic biharmonic maps. (2) examples of non-harmonic biharmonic maps.

##### MSC:
 58E20 Harmonic maps between infinite-dimensional spaces 53C43 Differential geometric aspects of harmonic maps
##### Keywords:
biharmonic map; sphere
##### References:
 [1] R. Caddeo, S. Montaldo and C. Oniciuc, biharmonic submanifolds ofS 3, International Journal of Mathematics, to appear. [2] B. Y. Chen,Some open problems and conjectures on submanifolds of finite type, Soochow Journal of Mathematics17 (1991), 169–188. [3] B. Y. Chen and S. Ishikawa,Biharmonic pseudo-Riemannian submanifolds in pseudo-Euclidean spaces, Kyushu Journal of Mathematics52 (1998), 167–185. · Zbl 0892.53012 · doi:10.2206/kyushujm.52.167 [4] B. Y. Chen and K. Yano,Minimal submanifolds of a higher dimensional sphere, Tensor (N.S.)22 (1971), 369–373. [5] I. Dimitric,Submanifolds of E m with harmonic mean curvature vector, Bulletin of the Institute of Mathematics. Academic Sinica20 (1992), 53–65. [6] J. Eells and J.H. Sampson,Harmonic mappings of Riemannian manifolds, American Journal of Mathematics86 (1964), 109–160. · Zbl 0122.40102 · doi:10.2307/2373037 [7] H. Gluck,Geodesics in the unit tangent bundle of a round sphere, L’Enseignement Mathématique34 (1988), 233–246. [8] T. Hasanis and T. Vlachos, Hypersurfaces inS 4 with harmonic mean curvature vector field, Mathematische Nachrichten172 (1995), 145–169. · Zbl 0839.53007 · doi:10.1002/mana.19951720112 [9] G. Y. Jiang,2-harmonic isometric immersions between Riemannian manifolds, Chinese Annals of Mathematics. Series A7 (1986), 130–144. [10] G. Y. Jiang,2-harmonic maps and their first and second variational formulas, Chinese Annals of mathematics. Series A7 (1986), 389–402. [11] H. B. Lawson, Complete minimal surfaces inS 3, Annals of Mathematics (2)92 (1970), 335–374. · Zbl 0205.52001 · doi:10.2307/1970625 [12] C. Oniciuc,Biharmonic maps between Riemannian manifolds, Analele Stiintifice ale University Al. I. Cuza Iasi. Mat. (N.S.), to appear. [13] J. Simons,Minimal varieties in Riemannian manifolds, Annals of Mathematics88 (1968), 62–105. · Zbl 0181.49702 · doi:10.2307/1970556