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* [beamer] When are :BEAMER_envargs: used or ignored?
@ 2012-02-27  7:07 James Harkins
2012-04-25  4:41  Eric Fraga
From: James Harkins @ 2012-02-27  7:07 UTC (permalink / raw)
To: emacs-orgmode

According to the online documentation [1], it seems that :BEAMER_envargs: should apply to all Beamer environments:

~~~
BEAMER_envargs
The beamer-special arguments that should be used for the environment, like [t] or [<+->] of <2-3>. If the BEAMER_col property is also set, something like C[t] can be added here as well to set an options argument for the implied columns environment. c[t] or c<2-> will set an options for the implied column environment.
~~~

This does work in the example presentation at [1], but it seems only for B_block entries. I was trying to use B_beamercolorbox, where presumably the color selections (fg=, bg=) should be environment arguments, but this is ignored. What's more, if I take the colors out of the color box's envargs and replace it with another argument syntax -- <2-> -- that definitely works with B_block, this is also ignored. So it seems, if you wanted to have a colorbox appear in a later overlay, you would be screwed (would have to write the LaTeX by hand).

A bit confused.

Or, the simple question -- how do you set the colors of a color box in Beamer export?

Oh, wait, I just figured it out... though you would have to admit, this is not remotely obvious.

** Frame 2 \\ where we will not use columns
#+LaTeX: \setbeamercolor{ybg}{bg=yellow}
*** ybg 						   :B_beamercolorbox:
:PROPERTIES:
:BEAMER_env: beamercolorbox
:END:

It kind of strikes me like an epic hack: you have to name the headline after the Beamer color ID, instead of naming the headline after the content... not very /org/anized.

Worth a bug report or feature request?

hjh

[1] http://orgmode.org/manual/Beamer-class-export.html

--
James Harkins /// dewdrop world
jamshark70@dewdrop-world.net
http://www.dewdrop-world.net

"Come said the Muse,
Sing me a song no poet has yet chanted,
Sing me the universal."  -- Whitman

blog: http://www.dewdrop-world.net/words
audio clips: http://www.dewdrop-world.net/audio
more audio: http://soundcloud.com/dewdrop_world/tracks

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [beamer] When are :BEAMER_envargs: used or ignored?
2012-02-27  7:07 [beamer] When are :BEAMER_envargs: used or ignored? James Harkins
@ 2012-04-25  4:41  Eric Fraga
2012-04-25 10:09    James Harkins
From: Eric Fraga @ 2012-04-25  4:41 UTC (permalink / raw)
To: James Harkins; +Cc: emacs-orgmode

James Harkins <jamshark70@gmail.com> writes:

> According to the online documentation [1], it seems
> that :BEAMER_envargs: should apply to all Beamer environments:

And it does generally although I have tried setting it (for your example
below) to {ybg} and it disappears.  If I set it to [ybg], it does appear
in the exported latex.  I haven't delved into the beamer export code in
a long while but it must be checking for constructs of the form [...] or
<...>, I would guess.

[...]

> Or, the simple question -- how do you set the colors of a color box in
> Beamer export?

> Oh, wait, I just figured it out... though you would have to admit,
> this is not remotely obvious.

> ** Frame 2 \\ where we will not use columns
> #+LaTeX: \setbeamercolor{ybg}{bg=yellow}
> *** ybg 						   :B_beamercolorbox:
>     :PROPERTIES:
>     :BEAMER_env: beamercolorbox
>     :END:
>
> It kind of strikes me like an epic hack: you have to name the headline
> after the Beamer color ID, instead of naming the headline after the
> content... not very /org/anized.

Well, the problem is that a beamercolorbox is *not* a block and does not
expect a title parameter.  It actually expects only a colour (well, a
beamer colour structure, to be precise, such as the one you have
defined).  What is /org/ expected to do with the entry you specify?

To achieve what you want (maybe, as I am not clear exactly what you want
;-), you should probably define a block *within* the beamercolorbox or
vice versa.  For instance:

--8<---------------cut here---------------start------------->8---
** Frame 2 \\ where we will not use columns
*** ybg                                                    :B_beamercolorbox:
:PROPERTIES:
:BEAMER_env: beamercolorbox
:END:
**** Title                                                          :B_block:
:PROPERTIES:
:BEAMER_env: block
:END:
--8<---------------cut here---------------end--------------->8---

> Worth a bug report or feature request?

It is not a bug, IMO.

Whether it should be a feature request or not is debatable.  The syntax
is, at present, fairly straightforward in that the headline text becomes
the argument to the environment defined.  What that environment does
with the argument is obviously up to the environment itself!

HTH,
eric
--
: Eric S Fraga (GnuPG: 0xC89193D8FFFCF67D) in Emacs 24.1.50.1
: using Org-mode version 7.8.06 (release_7.8.06.181.g67694.dirty)

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [beamer] When are :BEAMER_envargs: used or ignored?
2012-04-25  4:41  Eric Fraga
@ 2012-04-25 10:09    James Harkins
2012-04-25 12:49      James Harkins
2012-04-25 13:15      Eric Fraga
0 siblings, 2 replies; 8+ messages in thread
From: James Harkins @ 2012-04-25 10:09 UTC (permalink / raw)
To: emacs-orgmode

At Wed, 25 Apr 2012 14:11:51 +0930,
Eric Fraga wrote:
> > It kind of strikes me like an epic hack: you have to name the headline
> > after the Beamer color ID, instead of naming the headline after the
> > content... not very /org/anized.
>
> Well, the problem is that a beamercolorbox is *not* a block and does not
> expect a title parameter.  It actually expects only a colour (well, a
> beamer colour structure, to be precise, such as the one you have
> defined).  What is /org/ expected to do with the entry you specify?

If the subtree is folded, then the headline shows the color descriptor but nothing about the content of the subtree! That's some distance away from "an outline works like your brain."

It's not that I can't get the right output. It *is* a pretty stark inconsistency against org-mode's governing principle. Here, formatting information that is irrelevant to content is promoted to be the *most important thing* (the headline) of that subtree. What I need to see, in order to understand the structure of the content at a glance -- this IMO is org-mode's genius -- is hidden if the subtree is folded. Hm?

It strikes me as flawed design.

> > Worth a bug report or feature request?
>
> It is not a bug, IMO.

Okay, it's not a bug in the strict sense of a feature that doesn't behave as designed. I would say it's a d@mn ugly design.

> Whether it should be a feature request or not is debatable.  The syntax
> is, at present, fairly straightforward in that the headline text becomes
> the argument to the environment defined.

I think "the headline text becomes the argument..." is the opposite of straightforward. :-)

It's also a matter of incomplete documentation. The syntax is /perhaps/ straightforward, *after* spending some time wondering why it didn't work to put the color into an environment argument (as one might reasonably guess), and then spending more time constructing some tests and looking at the *.tex output to find out which bit of org text gets put where in the TeX code.

C-c C-b lists 19 ways to tag headlines for Beamer environments. [1] doesn't describe any of them. I do understand about volunteer documentation efforts (if days were 48 hours long, I still wouldn't be able to write more than half of the documentation I want to contribute to SuperCollider [2]), but I can't help feeling something is missing here.

James

[1] http://orgmode.org/manual/Beamer-class-export.html#Beamer-class-export
[2] http://supercollider.sourceforge.net

--
James Harkins /// dewdrop world
jamshark70@dewdrop-world.net
http://www.dewdrop-world.net

"Come said the Muse,
Sing me a song no poet has yet chanted,
Sing me the universal."  -- Whitman

blog: http://www.dewdrop-world.net/words
audio clips: http://www.dewdrop-world.net/audio
more audio: http://soundcloud.com/dewdrop_world/tracks

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [beamer] When are :BEAMER_envargs: used or ignored?
2012-04-25 10:09    James Harkins
@ 2012-04-25 12:49      James Harkins
2012-04-26  8:14        Eric Fraga
2012-04-25 13:15      Eric Fraga
From: James Harkins @ 2012-04-25 12:49 UTC (permalink / raw)
To: emacs-orgmode

At Wed, 25 Apr 2012 18:09:18 +0800,
James Harkins wrote:
> > Whether it should be a feature request or not is debatable.  The syntax
> > is, at present, fairly straightforward in that the headline text becomes
> > the argument to the environment defined.
>
> I think "the headline text becomes the argument..." is the opposite of straightforward. :-)

OK, wait, I get it:

OK, it's a consistent translation. But I still have the issue with it that the user has to adapt the org-file structure to suit beamer's requirements. Org-mode is all about reflecting the content in a way that makes sense FIRST to humans, and only secondarily to exporting engines.

hjh

--
James Harkins /// dewdrop world
jamshark70@dewdrop-world.net
http://www.dewdrop-world.net

"Come said the Muse,
Sing me a song no poet has yet chanted,
Sing me the universal."  -- Whitman

blog: http://www.dewdrop-world.net/words
audio clips: http://www.dewdrop-world.net/audio
more audio: http://soundcloud.com/dewdrop_world/tracks

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [beamer] When are :BEAMER_envargs: used or ignored?
2012-04-25 10:09    James Harkins
2012-04-25 12:49      James Harkins
@ 2012-04-25 13:15      Eric Fraga
1 sibling, 0 replies; 8+ messages in thread
From: Eric Fraga @ 2012-04-25 13:15 UTC (permalink / raw)
To: James Harkins; +Cc: emacs-orgmode

James Harkins <jamshark70@gmail.com> writes:

> At Wed, 25 Apr 2012 14:11:51 +0930,
> Eric Fraga wrote:
>> > It kind of strikes me like an epic hack: you have to name the headline
>> > after the Beamer color ID, instead of naming the headline after the
>
>> > content... not very /org/anized.
>>
>> Well, the problem is that a beamercolorbox is *not* a block and does not
>> expect a title parameter.  It actually expects only a colour (well, a
>> beamer colour structure, to be precise, such as the one you have
>> defined).  What is /org/ expected to do with the entry you specify?
>
> If the subtree is folded, then the headline shows the color descriptor
> but nothing about the content of the subtree! That's some distance
> away from "an outline works like your brain."

Yes.  You could, of course, turn my suggestion inside out: have the
block first and then the coloured box as a subheading...  then the main
heading would at least give you an indication of what follows.

> It's not that I can't get the right output. It *is* a pretty stark
> inconsistency against org-mode's governing principle. Here, formatting
> information that is irrelevant to content is promoted to be the *most
> important thing* (the headline) of that subtree. What I need to see,
> in order to understand the structure of the content at a glance --
> this IMO is org-mode's genius -- is hidden if the subtree is
> folded. Hm?
>
> It strikes me as flawed design.

Well, it's a compromise, I would suggest.  most compromises can indeed
be considered flawed design from an aesthetic point of view.  org is
based on outlines, not on containers.  Latex is based on containers
(mostly).  This basic inconsistency comes up all the time on this list
(e.g. a lower level entry can only be ended by starting a new headline
at the same or higher level).

>> > Worth a bug report or feature request?
>>
>> It is not a bug, IMO.
>
> Okay, it's not a bug in the strict sense of a feature that doesn't behave as designed. I would say it's a d@mn ugly design.

Fine.  That's one view.  I would suggest that maybe you could suggest a
better design, remembering, of course, that the basis of org is an
outliner...?

> It's also a matter of incomplete documentation. The syntax is

Indeed.  And I am partly to blame for this.  I do have a number of
outstanding TODO items with respect to the documentation of beamer
support in org.  But I also do have a real job which, unfortunately,
seems to take increasingly more hours every day...

> /perhaps/ straightforward, *after* spending some time wondering why it
> didn't work to put the color into an environment argument (as one
> might reasonably guess), and then spending more time constructing some
> tests and looking at the *.tex output to find out which bit of org
> text gets put where in the TeX code.
>
> C-c C-b lists 19 ways to tag headlines for Beamer environments. [1]

Yes, because the documentation was written to illustrate how org could
support beamer; a comprehensive document has never been written.  I
would be happy if you would consider contributing to the documentation?

--
: Eric S Fraga (GnuPG: 0xC89193D8FFFCF67D) in Emacs 24.1.50.1
: using Org-mode version 7.8.06 (release_7.8.06.181.g67694.dirty)

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [beamer] When are :BEAMER_envargs: used or ignored?
2012-04-25 12:49      James Harkins
@ 2012-04-26  8:14        Eric Fraga
2012-04-26  9:51          James Harkins
From: Eric Fraga @ 2012-04-26  8:14 UTC (permalink / raw)
To: James Harkins; +Cc: emacs-orgmode

James Harkins <jamshark70@gmail.com> writes:

> At Wed, 25 Apr 2012 18:09:18 +0800,
> James Harkins wrote:
>> > Whether it should be a feature request or not is debatable.  The syntax
>> > is, at present, fairly straightforward in that the headline text becomes
>
>> > the argument to the environment defined.
>>
>> I think "the headline text becomes the argument..." is the opposite of straightforward. :-)
>
> OK, wait, I get it:
>
>
>
> OK, it's a consistent translation.

Yes.

> But I still have the issue with it
> that the user has to adapt the org-file structure to suit beamer's
> requirements. Org-mode is all about reflecting the content in a way
> that makes sense FIRST to humans, and only secondarily to exporting
> engines.

I agree.  However, the problems arise when exporting because of
fundamentally different structures between org and the export
target.  This is why we have the various kludges (if people can forgive
me for calling them this) like ATTR_HTML and ATTR_LATEX.  There is no
easy or elegant mechanism in org for satisfying all the different export
target requirements that are fundamentally inconsistent with org's
outline heritage.

For this particular case, it could be that the beamercolorbox
environment could be made to expect a specific PROPERTY, much like the
column environment does.  The question would then be: what should the
headline be used for as beamercolorbox has no real text content
argument.

I would guess that if you could suggest a consistent and more elegant
solution, it would be considered favourably and maybe somebody would
take it up and implement it.  No promises, however!
--
: Eric S Fraga (GnuPG: 0xC89193D8FFFCF67D) in Emacs 24.1.50.1
: using Org-mode version 7.8.06 (release_7.8.06.181.g67694.dirty)

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [beamer] When are :BEAMER_envargs: used or ignored?
2012-04-26  8:14        Eric Fraga
@ 2012-04-26  9:51          James Harkins
2012-04-26 11:15            Sebastien Vauban
From: James Harkins @ 2012-04-26  9:51 UTC (permalink / raw)
To: emacs-orgmode

At Thu, 26 Apr 2012 17:44:56 +0930,
Eric Fraga wrote:
> > But I still have the issue with it
> > that the user has to adapt the org-file structure to suit beamer's
> > requirements. Org-mode is all about reflecting the content in a way
> > that makes sense FIRST to humans, and only secondarily to exporting
> > engines.
>
> I agree.  However, the problems arise when exporting because of
> fundamentally different structures between org and the export
> target.  This is why we have the various kludges (if people can forgive
> me for calling them this) like ATTR_HTML and ATTR_LATEX.  There is no
> easy or elegant mechanism in org for satisfying all the different export
> target requirements that are fundamentally inconsistent with org's
> outline heritage.

I understand. An elegant solution would take some mulling over (especially considering that I've only recently started using the export features, and my knowledge of LaTeX is superficial at best). In the meantime, I can live with the current situation.

That the headline title is used for the color specification is probably not such an unbearable thing in practice. How many color boxes are there likely to be on one slide? (Meaning, if you're tempted to load up a slide with so many color boxes that you get confused about the content, maybe the content needs to be restructured.) If it's the only color box on the slide, quite likely you can infer its content from the frame title or other headings nearby.

It just struck me as a loose end, and I'm glad I asked about it, because I have a better understanding of the issues now.

> For this particular case, it could be that the beamercolorbox
> environment could be made to expect a specific PROPERTY, much like the
> column environment does.  The question would then be: what should the
> headline be used for as beamercolorbox has no real text content
> argument.

There are other beamer tags that don't use the headline text, namely quote and quotation. According to the beamer user guide, there's no place for the headline:

\begin{quote}<action specification>
environment contents
\end{quote}

Compared to

\begin{block}<action specification>{block title}<action specification>
environment contents
\end{block}

So, there is already a situation where you have to put some dummy text into the headline that won't appear. Maybe there could be special handling for title-less environments, so that the headline would become the environment contents and colorbox could take its color from a property...

> I would guess that if you could suggest a consistent and more elegant
> solution, it would be considered favourably and maybe somebody would
> take it up and implement it.  No promises, however!

... but the elegance of that approach would be debatable, I suppose.

James

--
James Harkins /// dewdrop world
jamshark70@dewdrop-world.net
http://www.dewdrop-world.net

"Come said the Muse,
Sing me a song no poet has yet chanted,
Sing me the universal."  -- Whitman

blog: http://www.dewdrop-world.net/words
audio clips: http://www.dewdrop-world.net/audio
more audio: http://soundcloud.com/dewdrop_world/tracks

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [beamer] When are :BEAMER_envargs: used or ignored?
2012-04-26  9:51          James Harkins
@ 2012-04-26 11:15            Sebastien Vauban
0 siblings, 0 replies; 8+ messages in thread
From: Sebastien Vauban @ 2012-04-26 11:15 UTC (permalink / raw)
To: emacs-orgmode-mXXj517/zsQ

Hi James,

James Harkins wrote:
> At Thu, 26 Apr 2012 17:44:56 +0930,
> Eric Fraga wrote:
>> > But I still have the issue with it
>> > that the user has to adapt the org-file structure to suit beamer's
>> > requirements. Org-mode is all about reflecting the content in a way
>> > that makes sense FIRST to humans, and only secondarily to exporting
>> > engines.
>>
>> I agree.  However, the problems arise when exporting because of
>> fundamentally different structures between org and the export
>> target.  This is why we have the various kludges (if people can forgive
>> me for calling them this) like ATTR_HTML and ATTR_LATEX.  There is no
>> easy or elegant mechanism in org for satisfying all the different export
>> target requirements that are fundamentally inconsistent with org's
>> outline heritage.
>
> I understand. An elegant solution would take some mulling over (especially
> considering that I've only recently started using the export features, and my
> knowledge of LaTeX is superficial at best). In the meantime, I can live with
> the current situation.
>
> That the headline title is used for the color specification is probably not
> such an unbearable thing in practice. How many color boxes are there likely to
> be on one slide? (Meaning, if you're tempted to load up a slide with so many
> color boxes that you get confused about the content, maybe the content needs
> to be restructured.) If it's the only color box on the slide, quite likely you
> can infer its content from the frame title or other headings nearby.
>
> It just struck me as a loose end, and I'm glad I asked about it, because I
> have a better understanding of the issues now.
>
>> For this particular case, it could be that the beamercolorbox
>> environment could be made to expect a specific PROPERTY, much like the
>> column environment does.  The question would then be: what should the
>> headline be used for as beamercolorbox has no real text content
>> argument.
>
> There are other beamer tags that don't use the headline text, namely quote and
> quotation. According to the beamer user guide, there's no place for the
>
> \begin{quote}<action specification>
> environment contents
> \end{quote}
>
> Compared to
>
> \begin{block}<action specification>{block title}<action specification>
> environment contents
> \end{block}
>
> So, there is already a situation where you have to put some dummy text into
> the headline that won't appear.

And, in Org-Beamer, you have the explicit tag b_ignore' as well, to ignore
the entry title, using the contents only.

> Maybe there could be special handling for title-less environments, so that
> the headline would become the environment contents and colorbox could take
> its color from a property...

I don't find that a particularly attractive option, since you would end up
with very long headlines (often more than 80 characters) and you would not be
able to have multiline (or multiparagraph) contents.

Best regards,
Seb

--
Sebastien Vauban

^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2012-04-26 11:15 UTC | newest]

2012-02-27  7:07 [beamer] When are :BEAMER_envargs: used or ignored? James Harkins
2012-04-25  4:41  Eric Fraga
2012-04-25 10:09    James Harkins
2012-04-25 12:49      James Harkins
2012-04-26  8:14        Eric Fraga
2012-04-26  9:51          James Harkins
2012-04-26 11:15            Sebastien Vauban
2012-04-25 13:15      Eric Fraga

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text:
# Modifying an edge in a Feynman diagram generated by tikz-feynman

Consider the following Feynman diagram:

% !TeX program = lualatex
\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{tikz-feynman}
\begin{document}
\begin{center}

\feynmandiagram [large, horizontal=a to t1] {
a  -- [plain,reversed momentum=$$k_1+k_2$$] t1 -- [scalar, momentum'=$$q$$,edge label=$$m_1$$] t2 --[plain, momentum'=$$q+k_1$$,edge label=$$m_2$$]t3 -- [plain, momentum'=$$q+k_1+k_2$$,edge label=$$m_3$$]t1,
t2 -- [plain,reversed momentum=$$k_1$$] p1 ,
t3 -- [plain,reversed momentum=$$k_2$$] p2,
};
\end{center}
\end{document}

Now what I want to have is that the dotted edge to become semi-dotted together with a way to specify the orientation.

The transformed image in one of the two possible orientations should look like:

How to achieve this?

On my machine, your code does not reproduce your screenshot, but an upside-down version of it. However, it is rather straightforward to get the "semidashed" line. Just remember the nodes and draw the solid half-line as an overlay.

\documentclass[a4paper,10pt]{article}
\usepackage{amsmath}
\usepackage{tikz-feynman}
\begin{document}
\begin{center}

\feynmandiagram [large, horizontal=a to t1,remember picture] {
a  -- [plain,reversed momentum=$$k_1+k_2$$] t1
-- [scalar, momentum=$$q$$,edge label'=$$m_1$$] t2
--[plain, momentum=$$q+k_1$$,edge label'=$$m_2$$]t3
-- [plain, momentum=$$q+k_1+k_2$$,edge label'=$$m_3$$]t1,
t2 -- [plain,reversed momentum=$$k_1$$] p1 ,
t3 -- [plain,reversed momentum=$$k_2$$] p2,
};
\tikz[overlay,remember picture]{\path (t1) --(t2) coordinate[midway] (m1);
\draw[thick] (m1) --(t2);
}
\end{center}
\end{document}

• Thanks! But how come it became upside down? This seems really odd. – Subho Jun 19 '18 at 15:01
• @Subho95 I do not know for sure, but tikz-feynman gets continuously updated. When did you update your TeX distribution for the last time? (I stress that's just a guess.) – marmot Jun 19 '18 at 15:03
• A while back actually – Subho Jun 19 '18 at 15:09
• Is there a way to make a cleaner diagram? This one will work but the edge looks jagged. – Subho Jun 19 '18 at 15:14
• @Subho95 To tell you the truth, I do not use the layout algorithms myself because I find them hard to control (plus you can't upload these on the arXiv yet). Almost the same diagram without the automatic layout can be found e.g. here (except that the OP asked me to spoil it afterwards ;-). It would be much nicer if one could adjust the tension between the vertices (which should be possible, but I never tried to find out how that works). – marmot Jun 19 '18 at 15:23

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 Title: Vibronic transitions in the X-Sr series (X=Li, Na, K, Rb): on the accuracy of nuclear wavefunctions derived from quantum chemistry Author(s): Hauser, Andreas W. Contributor(s): Ernst, Wolfgang E.; Pototschnig, Johann V.; Meyer, Ralf Subject(s): Theory and Computation Abstract: Research on ultracold molecules has seen a growing interest recently in the context of high-resolution spectroscopy and quantum computation. The preparation of molecules in low vibrational levels of the ground state is experimentally challenging, and typically achieved by population transfer using excited electronic states. On the theoretical side, highly accurate potential energy surfaces are needed for a correct description of processes such as the coherent de-excitation from the highest and therefore weakly bound vibrational levels in the electronic ground state via couplings to electronically excited states. Particularly problematic is the correct description of potential features at large intermolecular distances. Franck-Condon overlap integrals for nuclear wavefunctions in barely bound vibrational states are extremely sensitive to inaccuracies of the potential at long range. In this study, we compare the predictions of common, wavefunction-based ab initio techniques for a known de-excitation mechanism in alkali-alkaline earth dimers. It is the aim to analyze the predictive power of these methods for a preliminary evaluation of potential cooling mechanisms in heteronuclear open shell systems which offer the experimentalist an electric as well as a magnetic handle for manipulation. The series of $X$-Sr molecules, with $X$ = Li, Na, K and Rb, has been chosen for a direct comparison. Quantum degenerate mixtures of Rb and Sr have already been produced,\footnote{B. Pasquiou, A. Bayerle, S. M. Tzanova, S. Stellmer, J. Szczepkowski, M. Parigger, R. Grimm, and F. Schreck, Phys. Rev. A, 2013, 88, 023601} making this combination very promising for the production of ultracold molecules. Issue Date: 2016-06-21 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper/Presentation Type: Text Language: En URI: http://hdl.handle.net/2142/91307 Rights Information: Copyright 2016 by the authors Date Available in IDEALS: 2017-01-26


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## Pushing the Limits of Fewshot Anomaly Detection in Industry Vision: Graphcore

Abstract: In the area of few-shot anomaly detection (FSAD), efficient visual feature plays an essential role in the memory bank $\mathcal{M}$-based methods. However, these methods do not account for the relationship between the visual feature and its rotated visual feature, drastically limiting the anomaly detection performance. To push the limits, we reveal that rotation-invariant feature property has a significant impact on industrial-based FSAD. Specifically, we utilize graph representation in FSAD and provide a novel visual isometric invariant feature (VIIF) as an anomaly measurement feature. As a result, VIIF can robustly improve the anomaly discriminating ability and can further reduce the size of redundant features stored in $\mathcal{M}$ by a large amount. Besides, we provide a novel model GraphCore via VIIFs that can fast implement unsupervised FSAD training and improve the performance of anomaly detection. A comprehensive evaluation is provided for comparing GraphCore and other SOTA anomaly detection models under our proposed few-shot anomaly detection setting, which shows GraphCore can increase average AUC by 5.8%, 4.1%, 3.4%, and 1.6% on MVTec AD and by 25.5%, 22.0%, 16.9%, and 14.1% on MPDD for 1, 2, 4, and 8-shot cases, respectively.


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# Shanks' square forms factorization

Shanks's square forms factorization is a method for integer factorization devised by Daniel Shanks as an improvement on Fermat's factorization method.

The success of Fermat's method depends on finding integers $x$ and $y$ such that $x^2-y^2=N$, where $N$ is the integer to be factored. An improvement (noticed by Kraitchik) is to look for integers $x$ and $y$ such that $x^2\equiv y^2\pmod{N}$. Finding a suitable pair $(x, y)$ does not guarantee a factorization of $N$, but it implies that $N$ is a factor of $x^2-y^2=(x-y)(x+y)$, and there is a good chance that the prime divisors of $N$ are distributed between these two factors, so that calculation of the greatest common divisor of $N$ and $x-y$ will give a non-trivial factor of $N$.

A practical algorithm for finding pairs $(x,y)$ which satisfy $x^2\equiv y^2\pmod{N}$ was developed by Shanks, who named it Square Forms Factorization or SQUFOF. The algorithm can be expressed in terms of continued fractions, or in terms of quadratic forms. Although there are now much more efficient factorization methods available, SQUFOF has the advantage that it is small enough to be implemented on a programmable calculator.

## Algorithm

Input: $N$, the integer to be factored, which must be neither a prime number nor a perfect square, and a small multiplier $k$.

Output: a non-trivial factor of $N$.

The algorithm:

Initialize $P_0=\lfloor\sqrt{kN}\rfloor,Q_0=1,Q_1=kN-P_0^2.$

Repeat

$b_i=\left\lfloor\frac{\lfloor\sqrt{kN}\rfloor+P_{i-1}}{Q_i}\right\rfloor,P_i=b_iQ_i-P_{i-1},Q_{i+1}=Q_{i-1}+b_i(P_{i-1}-P_i)$

until $Q_i$ is a perfect square.

Initialize $b_0=\left\lfloor\frac{\lfloor\sqrt{kN}\rfloor-P_{i-1}}{\sqrt{Q_i}}\right\rfloor,P_0=b_0\sqrt{Q_i}+P_{i-1},Q_0=\sqrt{Q_i},Q_1=\frac{kN-P_0^2}{Q_0}$

Repeat

$b_i=\left\lfloor\frac{\lfloor\sqrt{kN}\rfloor+P_{i-1}}{Q_i}\right\rfloor,P_i=b_iQ_i-P_{i-1},Q_{i+1}=Q_{i-1}+b_i(P_{i-1}-P_i)$

until $P_{i+1}=P_i.$

Then if $f=\gcd(N,P_i)$ is not equal to $1$ and not equal to $N$, then $f$ is a non-trivial factor of $N$. Otherwise try another value of $k$.

Shanks's method has time complexity $O(\sqrt[4]{N})$.

Stephen S. McMasters (see link in External Link section) wrote a more detailed discussion of the mathematics of Shanks's method, together with a proof of its correctness.

## Example

N = 11111, k = 1

P0 = 105 Q0 = 1 Q1 = 86

P1 = 67 Q1 = 86 Q2 = 77

P2 = 87 Q2 = 77 Q3 = 46

P3 = 97 Q3 = 46 Q4 = 37

P4 = 88 Q4 = 37 Q5 = 91

P5 = 94 Q5 = 91 Q6 = 25

Here Q6 is a perfect square

P0 = 104 Q0 = 5 Q1 = 59

P1 = 73 Q1 = 59 Q2 = 98

P2 = 25 Q2 = 98 Q3 = 107

P3 = 82 Q3 = 107 Q4 = 41

P4 = 82

Here P3 = P4

gcd(11111, 82) = 41, which is a factor of 11111.


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when quoting this document, please refer to the following
DOI: 10.4230/LIPIcs.STACS.2009.1826
URN: urn:nbn:de:0030-drops-18263
URL: http://drops.dagstuhl.de/opus/volltexte/2009/1826/

Englert, Matthias ; Röglin, Heiko ; Spönemann, Jacob ; Vöcking, Berthold

Economical Caching

 pdf-format:

Abstract

We study the management of buffers and storages in environments with unpredictably varying prices in a competitive analysis. In the economical caching problem, there is a storage with a certain capacity. For each time step, an online algorithm is given a price from the interval $[1,\alpha]$, a consumption, and possibly a buying limit. The online algorithm has to decide the amount to purchase from some commodity, knowing the parameter $\alpha$ but without knowing how the price evolves in the future. The algorithm can purchase at most the buying limit. If it purchases more than the current consumption, then the excess is stored in the storage; otherwise, the gap between consumption and purchase must be taken from the storage. The goal is to minimize the total cost. Interesting applications are, for example, stream caching on mobile devices with different classes of service, battery management in micro hybrid cars, and the efficient purchase of resources. First we consider the simple but natural class of algorithms that can informally be described as memoryless. We show that these algorithms cannot achieve a competitive ratio below $\sqrt{\alpha}$. Then we present a more sophisticated deterministic algorithm achieving a competitive ratio of $\textstyle \frac{1}{W\left(\frac{1-\alpha}{e\alpha}\right)+1} \in \left[\frac{\sqrt{\alpha}}{\sqrt{2}}, \frac{\sqrt{\alpha}+1}{\sqrt{2}} \right] \enspace,$ where $W$ denotes the Lambert~W function. We prove that this algorithm is optimal and that not even randomized online algorithms can achieve a better competitive ratio. On the other hand, we show how to achieve a constant competitive ratio if the storage capacity of the online algorithm exceeds the storage capacity of an optimal offline algorithm by a factor of $\log \alpha$.

BibTeX - Entry

@InProceedings{englert_et_al:LIPIcs:2009:1826,
author =	{Matthias Englert and Heiko R{\"o}glin and Jacob Sp{\"o}nemann and Berthold V{\"o}cking},
title =	{{Economical Caching}},
booktitle =	{26th International Symposium on Theoretical Aspects of Computer Science},
pages =	{385--396},
series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN =	{978-3-939897-09-5},
ISSN =	{1868-8969},
year =	{2009},
volume =	{3},
editor =	{Susanne Albers and Jean-Yves Marion},
publisher =	{Schloss Dagstuhl--Leibniz-Zentrum fuer Informatik},


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# Confusion about git; how to undo?

I wanted to install some source code that was on git. Don't really know what that means ; I've never used git before, but I figured it was time to learn so,

• I first installed git.

• Next I tried to clone the git directory of the software I want to install.

• I got a message saying "the authenticity of (IP) can't be established". I went ahead and ended up with another message saying, "warning, such and such will be added to known hosts." I went ahead, and it said something about hanging up on the connection.

After searching the internet for a while I realized I didn't need git to install the software but now I have it installed, and have added some host to some file or another. I'm concerned I've created some security issues I need to fix.

Can anyone help me undo what I've done, or better understand what I've done. Did adding a git project open up my system? Beyond that can anyone tell me how git works. Everything I've found assumes I know stuff that I don't yet.

Thanks

-

Git is a version control system (a DVCS to be more exact). A VCS (version control system) on a server (or on a computer, or in the cloud), is used to store and track changes to data. This just means that there is a repository of files (usually code in some programming language, along with configuration, instructions, etc.), and in addition to sitting on a server, it has changes made to it tracked across time. The version control system keeps track of any changes to any file in a project, and these projects are hosted, and frequently public or shareable.

A version control system with a front-end (whether git, or subversion/svn, bazaar/bzr, mercurial/hg, etc.) really just allows you to install applications (or packages, code, scripts, patches) that aren't available or up-to-date in the standard channels. Another way to put this is that it allows the authors of the code to share it with you and others.

Git (or another VCS) does this by pulling in all of the data from a repository (the remote IP.IP.IP.IP in your example) and dropping into a directory (that you choose, ultimately) on your system. By itself, this does nothing, unless you are actually running the code that you've gotten.

When you are using a VCS, having gotten the code doesn't necessarily mean you are going to run it as a complete suite. You might test it, update it, merge in some changes, take out some pieces. But in some cases, you can install complete applications (or more) from a repository.
If you can be sure that the code is safe, then this is a great way to play around with goodies that might not be available otherwise.

Having git on your system is unlikely to be a problem. If you're tight on space, you can remove it from the software center or with sudo apt-get remove git. (There might be additional packages, depending on how you installed it.)

It's hard to know how to undo anything that might have been done with downloaded code without knowing what it is that you've downloaded. You might start by doing something like ls -lart in your home directory (from the command line), or looking in Nautilus file manager for recently modified directories. For both of these methods, you're looking for the last changed directories files, some of which might be the ones you pulled onto your system with git. If you find that, you'll have a better idea if there's anything else you need to remove or get help with undoing.

As far as the adding the host, I'm pretty sure that @Christoph (as well as @psusi) is correct. The easiest way to rollback ssh key changes you have made is to do this:

 buntubox#\$  rm -i ~/.ssh/known_hosts

Note that this will delete the entire known_hosts file. This isn't usually a problem, because it will be rebuilt as you ssh to additional or repeat hosts. Alternately, you can edit the file (with gedit, nano, etc.) and remove lines you don't need. (Each line is associated with a remote host.) Again, this should be safe to do -- at worst, you'll have to accept new keys when logging into systems you've logged into before.

-
to add something here: the thing where it added some host to some file is probably that the ssh security key of the server you connected to was added to the ssh known hosts file at ~/.ssh/known_hosts. see amath.colorado.edu/computing/unix/sshknownhosts.html for more info –  Christoph Mar 3 '11 at 9:04

The message you got was from ssh, which was probably the protocol you were using to connect to the git server. Ssh remembers the fingerprint of remote servers you have used in the past so that when you try to connect again, it can verify that it is actually the same server, and not someone trying to impersonate that server. Naturally the first time you connect, it can't do this, which is what it was warning you about. What you saved was the fingerprint so that future connections can be verified as being to the legitimate server.

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# Euler Method – Numerical Differentiation with MATLAB

Euler method is numerical method to solve the first order ordinary differential equation with given initial condition. The Euler method is only first order convergent, i.e., the error of the computed solution is O(h), where h is the time step.

At here, we write the code of Euler Method in MATLAB step by step. MATLAB is easy way to solve complicated problems that are not solve by hand or impossible to solve at page. MATLAB is develop for mathematics, therefore MATLAB is the abbreviation of MATrix LABoratory.

The formula of Euler method is $y_{n+1}=y_{n}+hf(t_{n},y_{n})$

At here, we solve the differential equation $\frac{dy}{dt}=y-t^{2}+1$ by using Euler method with the help of MATLAB.

% Numerical Method
% Euler method using MATLAB coding
% Euler method also known as Runge-Kutta method of order 2
clear all;
close all;
clc;

f=inline('y-t^2+1');
x0=input('Enter x0=');
y0=input('Enter y0=');
xn=input('Enter upper limit of interval xn=');
h=input('Enter width (equal space) h=');
n=(xn-x0)/h;

fprintf('--------------------------------------------\n')
fprintf('    x              y            ynew\n');
fprintf('--------------------------------------------\n')

for i=1:n
y1=y0+h*f(x0,y0);
fprintf('%f      %f       %f \n',x0,y0,y1)
y0=y1;
x0=x0+h;
end


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# What is the domain and range of f(x) = 5/(x-9)?

Jan 13, 2016

DOMAIN: $x \in \left(- \infty , 9\right) \cup \left(9 , + \infty\right)$

RANGE: $y \in \left(- \infty , 0\right) \cup \left(0 , + \infty\right)$

#### Explanation:

$y = f \left(x\right) = \frac{k}{g} \left(x\right)$

Existence Condition is:

$g \left(x\right) \ne 0$

$\therefore x - 9 \ne 0$

$\therefore x \ne 9$

Then:

$F . E .$= Field of Existence=Domain: $x \in \left(- \infty , 9\right) \cup \left(9 , + \infty\right)$

$x = 9$ could be a vertical asymptote

To find the range we have to study the behavior for:

• $x \rightarrow \pm \infty$

${\lim}_{x \rightarrow - \infty} f \left(x\right) = {\lim}_{x \rightarrow - \infty} \frac{5}{x - 9} = \frac{5}{-} \infty = {0}^{-}$

${\lim}_{x \rightarrow + \infty} f \left(x\right) = {\lim}_{x \rightarrow + \infty} \frac{5}{x - 9} = \frac{5}{+ \infty} = {0}^{+}$

Then

$y = 0$ is a horizontal asymptote.

Indeed,

$f \left(x\right) \ne 0 \forall x \in F . E .$

• $x \rightarrow {9}^{\pm}$

${\lim}_{x \rightarrow {9}^{-}} f \left(x\right) = {\lim}_{x \rightarrow {9}^{-}} \frac{5}{x - 9} = \frac{5}{0} ^ \left(-\right) = - \infty$

${\lim}_{x \rightarrow {9}^{+}} f \left(x\right) = {\lim}_{x \rightarrow {9}^{+}} \frac{5}{x - 9} = \frac{5}{0} ^ \left(+\right) = + \infty$

Then

$x = 9$ it's a vertical asympote

$\therefore$ Range of $f \left(x\right)$: $y \in \left(- \infty , 0\right) \cup \left(0 , + \infty\right)$


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# Dynamic light scattering laplace inversion

1. Jul 27, 2012

### Steve Drake

Hi,

Those of you familar with dynamic light scattering (DLS), will know that a common method used to obtain a particle size distribution is via a laplace inversion of the autocorrelation function.

What I want to know is why? What does Laplace space have to do with DLS (I've only learned basics Laplace transforms and Laplace inversions from simple elec eng...). My understanding is that the scattered light depends on how fast the particles are diffusing. And that the propagating light from the sample to the detector undergoes an optical Fourier transform.

I also know that you can take the Fourier transform of the ACF to obtain the power spectrum...

But where does laplace come into this? All papers I read just say that the spectrum can be described by the equation

$g^{(1)}=\int G(\Gamma )e^{(-\text{\Gamma t})}$

Thanks

2. Jul 27, 2012

### M Quack

Hint: How is G[Gamma] related to g(t)?

Gamma = q^2 D

where D is the diffusion coefficient. I guess that the particle size can be derived from D.

Then G(Gamma) gives you a measure for the number of particles with that size.

3. Jul 27, 2012

### Steve Drake

Yes, I do know that $\Gamma$ is Dq2,

for example the simplest case is just an exponential decay exp(-Dq2$\tau$), where we obtain the diffusion coefficient D, and intern the radius (stokes Einstein).

But what I dont understand is why does the Laplace inversion describe g(1)?

4. Jul 27, 2012

### Andy Resnick

From my perspective, the Laplace transform is very similar to a Fourier transform- the Laplace transform can be used when dissipative processes occur. If you like, think of exp(iwt), but allow the frequency w to be imaginary (or complex, if you want to think more generally). Because DLS probes diffusive transport, the processes are dissipative.

Does that help?

5. Jul 27, 2012

### M Quack

Laplace inversion is nothing else than inverting the equation you cite.

G(Gamma) = Laplace(g(t))

If there is only one contribution then G(Gamma) = delta(Gamma-Dq^2)

If there are more then G(Gamma) will be a distribution. The width of the distribution will tell you about polydispersity, the peak position about avg. size, etc.

6. Jul 28, 2012

### Steve Drake

Thanks guys,

So basically its inverting that equation for each delay time (t) and trying to get the best fit?

But what I still dont understand is why you cant just put a trial distribution in for G (say Gaussian), and then just do numerical integration to solve for $\Gamma$?

7. Jul 29, 2012

### M Quack

You can do that, but you need to have a guess about the trial function first. You can also assume a Gaussian and then fit the parameters (FHWM, peak position, ...) until the (numerical) integral matches the measured spectrum.

A Laplace inversion does not require a model.

8. Jul 29, 2012

### Steve Drake

Thanks, I think im beginning to understand it more now. I think my problem is the lack of knowledge of laplace stuff, i never can understand it. Fourier makes sense but not laplace. So the laplace inversion can take into account the possibility of bimodal solutions or solutions with a broad or narrow distribution. But if you do it numerically you have to put in say a Gaussian of a certain FWHM and peak position, do the numerical integration, change the FWHM or peak, do it again etc etc till the best fit, and then it may not even be a Gaussian shaped distribution.

So if for instance you put in particles of a certain size and you KNOW all aspects of the distribution (say gaussian), would the laplace inversion give the same answer as a gaussian + numerical (in a perfect world), or a close one...?

Thanks a lot again

9. Jul 29, 2012

### M Quack

I guess yes.

It should be possible to do a numerical Laplace inversion without any prior assumtions about the data, similar to a numerical Fourier transform.

10. Jul 31, 2012

### Steve Drake

Ok thanks a lot for this,

so in general, The numerical methods of laplace inversion are a 'quick way' to fully describe the data points rather than just doing numerical integration with heaps of different parameters?


text:
Display real apostrophe in parts of a document

The question How to make a real apostrophe or single-quote in LaTeX is my question too, but the answer points to a package upquote that affects the entire document. I need to display an apostrophe (U+0027) only a couple of times within the document. Otherwise I would like the general conversion to quote to take place.

\documentclass{article}
\usepackage{fontspec, xunicode, xltxtra}
\defaultfontfeatures{Mapping = tex-text}

\begin{document}
\noindent I would like an apostrophe to appear in the word ap'ple (U+0027), but a right quotation mark (U+2019) when I quote the word orange'.
\end{document}

-
So you actually want in some places to not have the typographically right apostrophe/right quotation mark (U+2019) but the vertical typewriter apostrophe ' (U+0027, the one that you get by hitting the ' key, which is the one that appears in the input)? How should LaTeX distinct between the two types of input? –  Qrrbrbirlbel Feb 24 '13 at 21:09
@Qrrbrbirlbel: Presumably by having two distinct inputs ... –  Sverre Feb 25 '13 at 12:06

Solution 1: Markup for quotations

One simple way to do this would be to not use the Mapping=text-tex (which, BTW has been replaced with the Ligatures=TeX option) and use the csquotes package to manage your quoting. Here's an example:

% !TEX TS-program = XeLaTeX
\documentclass{article}
\usepackage{fontspec}
\setmainfont{Linux Libertine O}
\usepackage{csquotes}
\MakeOuterQuote{"}

\begin{document}
\noindent I would like an apostrophe to appear in the word ap'ple (U+0027), but a
right proper quotations marks (U+2019) when I quote a word with double quotes:
\enquote{orange} or single quotes: \enquote*{orange} or double quotes using the
"Active Quotes" function of the package.
\end{document}

Solution 2: Define an apostrophe font and markup

Another way would be to load your font twice, once using the Ligatures=TeX and the other without, and then define markup for the apostrophe.

% !TEX TS-program = XeLaTeX
\documentclass{article}
\usepackage{fontspec}
\setmainfont[Ligatures=TeX]{Linux Libertine O}
\newfontfamily\quotefont{Linux Libertine O}
\newcommand{\apostrophe}{{\quotefont'}} % or just use {\quotefont text}

\begin{document}
\noindent I would like an apostrophe to appear in the word ap\apostrophe ple
(U+0027), or {\quotefont ap'ple} but a right proper quotations marks (U+2019) when I
quote a word with double quotes: orange'' or single quotes: orange'.
\end{document}

In this solution, the markup for the apostrophe isn't actually necessary, since any text that is grouped with {\quotefont ... } will use the single quote as typed.

-
Both of these solutions seem to be perfect. In my specific scenario, however, it turns out that your pointing out the Ligatures=TeX is all I need, because in the cases I need the apostrophe to appear as an apostrophe, the font is not my main font, so I can just not include Ligatures=TeX as an option in my \newfontfamily\coolfont\{Name of my cool font} call. –  Sverre Feb 25 '13 at 12:41
Another, and perhaps the easiest, solution is given in tex.stackexchange.com/questions/103076/… –  Sverre Mar 20 '13 at 15:38
@Sverre The Mapping solution only works for XeLaTeX and can't be extended to LuaLaTeX, though. –  Alan Munn Mar 20 '13 at 18:37

Another method (I got the idea from reading 2 Font commands in the XeTeX reference (texdoc xetexref)):

\documentclass{article}
\usepackage{fontspec}
\usepackage{libertine}

\newcommand{\apostrophe}{\XeTeXglyph\XeTeXcharglyph"0027\relax}

\begin{document}
\noindent I would like an apostrophe to appear in the word ap\apostrophe ple
(U+0027) but a right proper quotations marks (U+2019) when I
quote a word with double quotes: orange'' or single quotes: orange'.
\end{document}
`

Here is the result (also tested ok with other fonts):

-


text:
## Monday, July 27, 2015

### UCI Summer School part 2: Duality Theorem (Monroe Eskew)

The Duality Theorem gives a general technique for forcing to make an ideal whose quotient algebra has various properties. It appears in Matthew Foreman's "Calculating quotient algebras of generic embeddings." My version of these notes omits a lot of the dots which indicate that certain objects are just names in a forcing extension. This is for aesthetic reasons, and hopefully does not lead to confusion.

Duality Theorem: Suppose $I$ is a precipitous ideal on $Z$ and $\mathbb{P}$ is any partial order. If: there is a further generic extension of the extension by $P(Z)/I$ so that if $j:V\rightarrow M\subseteq M\subseteq V[G]$ is the ultrapower embedding from $G\subseteq P(Z)/I$, there is $H\subseteq \mathbb{P}$ generic over $V$ and $\hat{H}\subseteq j(\mathbb{P})$ generic over $M$ and some extension of $j$ to $\hat{j}:V[H]\rightarrow M[\hat{H}]$.

Then: there is a $\mathbb{P}$-name for an ideal $J$ on $Z$ and a $P(Z)/I$-name for an ideal $K$ on $j(\mathbb{P})$ and a canonical isomorphism $$\iota:\mathcal{B}(\dot{\mathbb{P}\ast P(Z)/J})\equiv \mathcal{B}(P(Z)/I\ast j(\mathbb{P})/\dot{K}).$$

So a very general statement of lifting a generic ultrapower map to a forcing extension gives a useful isomorphism for computing $P(Z)/J$ in the generic extension by $\mathbb{P}$. We remark that in some cases, this will be an equivalence.

Note: In what follows, we tacitly identify all of the posets involved with their Boolean completions. Occasionally for emphasis, this identification will be explicit.

Proof: Assume (1). There is some $A\in I^+$ and some $P(Z)/I$-name for a forcing $\dot{\mathbb{Q}}$ so that
$$A\Vdash_{P(Z)/I}(\Vdash_\dot{\mathbb{Q}} \dot{H_0}\subseteq j(\mathbb{P}) \textrm{ is generic over }M \textrm{ and }H:=j^{-1}[H_0]\subseteq \mathbb{P}\textrm{ is generic over }V).$$

Note that the set $\{p\in\mathbb{P}:\quad \Vdash_{P(A)/I\ast \mathbb{Q}} j(p)\not\in H_0\}$ cannot be dense, since it is the complement of the generic $j^{-1}[H_0]$. So there is $p_0\in \mathbb{P}$ so that for all $p\le p_0$, $\| j(p)\in H_0 \|_{P(A)/I\ast \mathbb{Q}}\neq 0$. We will constrain ourselves to work below this $p_0$ in $\mathbb{P}$ and below $A$ in $P(Z)/I$. For simplicity, assume that $A=Z$ and $p_0=1_\mathbb{P}$.

In $V^{P(Z)/I}$, define
$$K=\{p\in j(\mathbb{P}):\quad \Vdash_{\mathbb{\dot{Q}^G}} p\not\in H_0\}.$$
Let $G\ast h$ be generic for $P(Z)/I\ast j(\mathbb{P})/K$. From the $j(\mathbb{P})/K$-generic $h$, we can define a $j(\mathbb{P})$-generic $\hat{H}=\{p:[p]_K\in h\}$.

Claim: The following properties of $H_0$ are also true of $\hat{H}$:

1. $\Vdash_{P(Z)/I\ast \mathbb{Q}} \hat{H}$ is $j(\mathbb{P})$-generic over $M$.
2. $\Vdash_{P(Z)/I\ast \mathbb{Q}} j^{-1}[\hat{H}]$ is $\mathbb{P}$-generic over $V$.
3. For all $p\in \mathbb{P}$, $\not\Vdash_{P(Z)/I\ast \mathbb{Q}} j(p)\not\in \hat{H}$.
Proof of Claim: For (1), suppose $D\in M$ is open dense in $j(\mathbb{P})$. Then $\{[d]_K:d\in D\textrm{ and }d\not\in K\}$ is dense in $j(\mathbb{P})/K$. Otherwise, there would exist $p\in j(\mathbb{P})/K$ so that $p\wedge d\in K$ for all $d\in D$. But this is impossible because we could then force with $\mathbb{Q}$ over $V[G]$ to get a generic $H_0$ containing $p$ (as $p\not\in K$), and then $H_0\cap D=\emptyset$, contradicting genericity of $H_0$ over $M$.

The remaining parts of the claim can be checked similarly, and are left as an exercise. $\Box$.

Now let $e:\mathbb{P}\rightarrow \mathcal{B}(P(Z)/I\ast \dot{j(\mathbb{P})/K})$ be defined by $e(p)=\|j(p)\in \hat{H}\|$.

By (3) of the claim above, $\mathrm{ker}(e)=0$. Also $e$ preserves Boolean operations simply by the elementarity of $j$. By (2) of the claim, $e$ is a regular embedding (maps maximal antichains pointwise to maximal antichains).

Exercise: $e:\mathbb{P}\rightarrow \mathbb{Q}$ is a regular embedding iff for every $q\in\mathbb{Q}$ there is $p\in \mathbb{P}$ so that for every $p'\le p$, $e(p')$ is compatible with $q$.

Thus, if $H\subseteq \mathbb{P}$ is generic over $V$, we can force with the quotient $\mathcal{B}(P(Z)/I\ast \dot{j(\mathbb{P})/K})/e"H$ over $V[H]$ to obtain a generic $G\ast h$ for $P(Z)/I\ast j(\mathbb{P})/K$. By the definition of $e$, we have $j_G"H\subseteq \hat{H}$, where $\hat{H}$ is defined from $h$ as before. So we can extend the embedding $j_G$ to $\hat{j}:V[H]\rightarrow M[\hat{H}]$.

In $V[H]$ we can finally define $J=\{A\subseteq Z:1\Vdash [\mathrm{id}]\not\in \hat{j}(A)\}$, where the forcing is with the quotient $\mathcal{B}(P(Z)/I\ast \dot{j(\mathbb{P})/K})/e"H$. In $V$, let
$$\iota(p,\dot{A})=e(p)\wedge \|[id]\in\hat{j}(\dot{A})\|.$$

Exercise: $\iota$ is order and incompatibility preserving.

It remains to show that the range of $\iota$ is dense. So take an arbitrary $(B,\dot{q})\in P(Z)/I\ast j(P)/K$. By strengthening this condition, we may assume without loss of generality that there is $f:Z\rightarrow \mathbb{P}$ in $V$ so that $B\Vdash [[f]_M]_K=\dot{q}$.

By regularity of $e$ (using the characterization in the exercise), there is a $p$ so that for all $p'\le p$, $e(p')\wedge (B,\dot{q})\neq 0$. Let $\dot{A}$ be a $\mathbb{P}$-name for a subset of $Z$ such that $p \Vdash \dot{A}=\{z\in B: f(z)\in H\}$ and $\neg p \Vdash \dot{A}\in J^+$.

We check that $(p,\dot{A})$ is actually a condition, which involves checking that $p\Vdash \dot{A}\in J^+$. So take a generic $G\ast \dot{h}$ containing $e(p)\wedge (B,\dot{q})$ (which is nonzero by choice of $p$). Then clearly $B\in G$ and since $[[f]_M]_K=q\in h$, we have $[f]_M=j(f)([\mathrm{id}])\in\hat{H}$. Therefore $[\mathrm{id}]\in \hat{j}(A)$, so this generic $G\ast \dot{h}$ shows that it is not forced by $\mathcal{B}(P(Z)/I\ast \dot{j(\mathbb{P})/K}/e"H$ that $[\mathrm{id}]\not\in \hat{j}(A)\}$.

By definition $\iota:=\iota(p,\dot{A})$ forces $j(p)\in \hat{H}$ and $[\mathrm{id}]\in\hat{j}(\dot{A})$. Since $\hat{j}$ extends $j$ and it's forced that $\dot{A}\subseteq B$, $\iota$ must force $B\in G$. And since $j(p)\Vdash_{j(\mathbb{P})} j(\dot{A})=j(\{z:j(f)(z)\in \hat{H}\})$, $\iota$ must force $\dot{q}=[j(f)(\mathrm{id})]_K\in h$. $\Box$

Remark: Suppose $K$ as in the Duality Theorem is forced to be principal, i.e., there is $m$ so that $$\Vdash K=\{p\in j(\mathbb{P}:p\le \neg m\}.$$
Then the Duality Theorem is easily seen to be an equivalence.

We can compute some nice properties of the ideal $J$ arising from the previous theorem.

Proposition: Using the notation of the previous theorem, $J$ is forced to be precipitous, with the same completeness as $I$. If $I$ is normal, then $J$ is also normal. Also, if $\bar{G}\subseteq P(Z)/J$ is generic over $V[H]$ and $G\ast h=\iota[H\ast \bar{G}]$ and $\hat{j}:V[H]\rightarrow M[\hat{H}]$ are as before, then $V[H]^Z/{\bar{G}}=M[\hat{H}]$ and $\hat{j}$ is the ultrapower embedding.

Finally, we relate $J$ to the ideal in $V[H]$ generated by $I$.

Proposition: Suppose $K$ as in the Duality Theorem is forced to be principal, with $m$ so that $\Vdash K=\{p\in j(\mathbb{P}):p\le \neg m\}.$ Suppose further that there exist $f$ and $A$ so that $A\Vdash \dot{m}=[f]_G$ and $\dot{B}$ is a $\mathbb{P}$-name for $\{z\in A: f(z)\in \dot{H}\}$. Then $\bar{I}\upharpoonright B=J\upharpoonright B$, and $A\setminus B\in J$, where $\bar{I}$ is the ideal in $V[H]$ generated by $I$.


text:
How to understand “a.s. convergence does not come from a metric, or even from a topology”?

The sentence "a.s. convergence does not come from a metric, or even from a topology" comes from a remark in Durrett's probability theory textbook, after following two theorems.

Theorem 2.3.2. $Xn \rightarrow X$ in probability if and only if for every subsequence $X_{n(m)}$ there is a further subsequence $X_{n(m_k)}$ that converges almost surely to $X$.

Theorem 2.3.3. Let $y_n$ be a sequence of elements of a topological space. If every subsequence $y_{n(m)}$ has a further subsequence $y_{n(m_k)}$ that converges to $y$ then $y_n \rightarrow y$.

The remark says "Since there is a sequence of random variables that converges in probability but not a.s., it follows from Theorem 2.3.3(above theorem) that a.s. convergence does not come from a metric, or even from a topology.

I don't know how to understand this. Although I know metric is about distance and topology is about open sets, I didn't see the connection between these. And what are some implications/applications of this property?

Let {X_n} be a sequence of random variables which converges in probability but not a.s. Take any subsequence of this sequence. The subsequence also converges in probability. This implies that there is a further subsequence which converges a.s. According to Theorem 2.3.3, if there is a topology on the space of all random variables on a given probability space in which convergence of a sequence is equivalent to a.s. convergence, then the original sequence {X_n} must itself converge a.s., which is not true.

I shall first define some notions of topology and their link with metric spaces and then answer your particular question about a.s. convergence. This is long but your initial question seems to ask for the link between topology and distance.

Almost sure convergence does not come from a topology

Take any sequence $(X_{n})_{n}$ of random variables converging in probability to some random variable $X$. Then, you know that any subsequence $(X_{n_{k}})_{k}$ converges in probability to $X$. But you know that from a sequence converging in probability to $X$, you can take a subsequence that converges almost surely to $X$. In that case, you can make every subsequence of $X_{n}$ converge almost surely to $X$. But then, if almost convergence comes from a topology, theorem 2.3.3 implies that the all sequence $(X_{n})_{n}$ converges almost surely to $X$. This is a contradiction since there exists sequences of random variables converging in probability but not almost-surely.

General definitions of metric spaces and topological spaces

A metric space is a set $X$ endowed with a distance (or metric) $d$, which is a function $d:X\times X\to\Bbb R_{+}:(x,y)\mapsto d(x,y)$ respecting the following properties:

• For all $x,y\in X$, $d(x,y)=d(y,x)$ (symmetry);
• For all $x,y\in X$, $d(x,y)\geq 0$ and $d(x,y)=0\iff x=y$ (positivity) and
• For all $x,y,z\in X$, $d(x,y)\le d(x,z)+d(z,y)$ (triangular inequality).

As an exercise, you can verify that $d:\Bbb R^{2}\times \Bbb R^{2}\to\Bbb R_{+}:((x_{1},y_{1}),(x_{2},y_{2})\mapsto \max\{\vert x_{1}-x_{2}\vert,\vert y_{1}-y_{2}\vert\}$ is a distance on $\Bbb R^{2}$.

A topological space is a set $X$ endowed with a collection $\mathcal{T}$ of subsets of $X$, which are called open sets, and such that:

• $X\in\mathcal{T}$ and $\emptyset\in\mathcal{T}$;
• For all $U,V\in\mathcal{T}$, we have $U\cap V\in\mathcal{T}$ (stability by finite intersections) and
• For any family $\{U_{\alpha}\}_{\alpha\in A}$ of open sets (i.e. of elements of $\mathcal{T}$), their union $\cup_{\alpha\in A}U_{\alpha}\in\mathcal{T}$ where $A$ is any set of indices ($A$ may be finite, countably infinite or uncountably infinite) (stability by unions).

A collection $\mathcal{T}$ of subsets of $X$ for which the three previous properties hold is called a "topology" on $X$. The complement in $X$ of an open set $U\in\mathcal{T}$ is called a closed set. Beware that this terminology can be dangerous: a set may be open and closed or may be neither open or closed (for a given topology)!

Link between metric space and topology

When you have a metric space $X,d$, you can define the so-called "open ball" of radius $r>0$ centered at $x_{0}\in X$:

$$B_{r}(x_{0})=\{x\in X\vert d(x,x_{0})<r\}$$

The "natural" topology on a metric space is the topology generated by the open balls. What does that mean? You define the topology to be the emptyset $\emptyset$, the finite intersections of open balls and any union of open balls. Then, obviously, this respects the property of a topology and so is a topology.

An equivalent way that is more intuitive is to say that a set $U$ is open for the topology induced by the metric if for any point $x\in U$, there exists $r>0$ such that $B_{r}(x)\subset U$, that is, there exists an open ball centered at $x$ that is still contained in $U$. This is quite intuitive, I think. One of the simplest example is $\mathbb{R}$ endowed with the "standard" distance/metric: the absolute value of the difference, that is, $d(x,y)=\vert x-y\vert$ where $x,y\in\mathbb{R}$. With the previous definition, you can determine what is an open ball and then you can check that any interval $(a,b)$ is an open set ($a\le b$), any interval $[a,b]$ ($a\le b$) is a closed set (you have to prove that $(-\infty,a)\cup(b,\infty)$ is open) and that $(a,b]$ or $[a,b)$ are neither close or open.

Notion of metrizability

Now, one can take a general topological space $X,\mathcal{T}$ and one can ask whether there exists a distance on $X$ such that the topology induced by $d$ on $X$ is the same as $\mathcal{T}$. If there exists such a distance, we say that $X,\mathcal{T}$ is metrizable. For example, if I take $\mathcal{T}$ to be all the subsets of $X$, then in particular $\mathcal{T}$ contains the singleton $\{x\}$ for every $x\in X$. And, obviously, the topology generated by the singletons is the topology that contains all the subsets of $X$ since any subset is a union of all its singletons, etc. This topology is called the discrete topology. Is there a distance which induces the same topology? Here, the answer is yes: take

$$d:X\times X\to\Bbb R_{+}:(x,y)\mapsto \begin{cases} d(x,y) = 1 &\text{if } x\neq y\\d(x,y) = 0 &\text{if } x= y\end{cases}$$

If you take $r=1/2$ for a radius, you see that open balls centered at $x$ are the singletons $\{x\}$.

(One of) The initial purpose(s) of topology

Now that the link between topology and metric spaces has been done, why would one study them? Topology is a convenient setting to talk about convergence despite having less structure than a metric space. In a metric space $X,d$, we say that a sequence $x_{n}$ converges to $x$ if for any $\epsilon>0$, there exists $N_{\epsilon}$ such that for all $n\geq N_{\epsilon}$, we have $d(x_{n},x)<\epsilon$. This is equivalent to say that for any $\epsilon>0$, there exists $N_{\epsilon}$ such that for all $n\geq N_{\epsilon}$, $x_{n}\in B_{\epsilon}(x)$, that is, from a certain index $n\geq N_{\epsilon}$, the remaining terms of the sequence are all contained in a small open ball around $x$. Naturally, in a topological space $X,\mathcal{T}$, we say that a sequence $(x_{n})_{n}$ converges to $x\in X$ (for the topology $\mathcal{T}$) if and only if, for every open set $U_{x}$ that contains $x$, there exists $N_{U_{x}}$ such that for all $n\geq N_{U_{x}}$, we have $x_{n}\in U_{x}$.

These are exactly the same definitions, but obviously the second one includes the first and is more general as there exists topological spaces that are not metrizable.

It wouldn't be fair to not talk about continuity of functions while introducing topology. Actually, I said that topology was convenient for talking about convergence, but this not exactly true. There exists topological spaces where some sequences converge to more than one point. This means that "limits" are not unique anymore (wrong choice of terminology since a "limit" is unique by definition but I hope you get the point). To ensure the unicity of "limits", one has to consider particular topological spaces called "Hausdorff" spaces or "$T_{2}$-spaces" or "separated spaces".

However, we can always talk about continuity in a well-defined manner. Let $X,d_{X}$ and $Y,d_{Y}$ be two metric spaces. A function $f:X\to Y$ is continuous at $x_{0}\in X$ if and only if for all $\epsilon>0$, there exists $\delta>0$ such that for all $x\in X$ with $d_{X}(x,x_{0})<\delta$, it holds that $d_{Y}(f(x),f(x_{0}))<\epsilon$. A function is said continuous if it is continuous at each point of $X$. We can rephrase that by saying that a function $f$ is continuous if for each $x_{0}\in X$, for each open ball $B_{\epsilon}(f(x_{0}))$ (of $Y,d_{Y}$) centered at $f(x_{0})\in Y$ and of radius $\epsilon>0$, there exists an open ball $B_{\delta}(x_{0})$ (of $X,d_{X}$) centered at $x_{0}$ such that $f(B_{\delta}(x_{0}))\subset B_{\epsilon}(f(x_{0}))$, that is, for any open ball in $Y$ containing $f(x_{0})$, there exists a small open ball in $X$ containing $x_{0}$ such that the image of this open ball is contained in the open ball containing $f(x_{0})$.

Now, you see it coming. A function $f:X\to Y$ between topological spaces $X,\mathcal{T}_{X}$ and $Y,\mathcal{T}_{Y}$ is said continuous if for any open set $U_{Y}\in\mathcal{T}_{Y}$, the preimage of $U_{Y}$ by $f$ is open in $X,\mathcal{T}_{X}$, that is, $f^{-1}(U_{Y})\in\mathcal{T}_{X}$.

Importance of metrizability

Metric spaces are particular cases of topological spaces, as suggested above. The particular structure they have because of the metric structure gives them very convenient properties that do not always hold for general topological space. Knowing that a topological space is metrizable implies that this topological space possesses all the properties of a metric space, which is very convenient. Indeed, one sometimes defines a topology to serve one's needs at the time but this topology may be useful for some applications but difficult to use for other. Knowing that it is metrizable can help broaden the range of applications of this topology.

One can define a topology in terms of closed sets and then define the open sets as the complements of closed sets. A closed set has the particular property that any convergence sequence in a closed set converges in the closed set, that is if $(x_{n})_{n}\subset C$ is a convergent sequence included in a closed set $C$ (closed for some topological space $X,\mathcal{T}$), then if $x_{n}\to x$ where $x\in X$, it follows that $x\in C$.
Others have already shown how to put the two theorems together but this observation, while being true, still seems somewhat mystical to me. But I think I have an explanation for what is going on here exactly and I will post it as an answer in case anyone else feels the same way. Suppose that the statement of Theorem 2.3.2 holds. Let $\Omega_m$ denote the full measure set on which a.s. convergence occurs along a subsequence of subsequence $m$. Note that there are an uncountable number of subsequences of $1,2,\ldots$. It is not necessarily true that the intersection of an uncountable number of full measure sets has also full measure (the intersection does not even need to be measurable). So then the condition of the theorem does not imply a.s. convergence along the original sequence but it implies convergence in probability.


text:
# Monte Carlo simulation

#### Juliana

##### New Member
Hi

I'm currently doing a third year university stats course. I need help with some questions.

The question gives Wind speed and Temperature data. It then asks to do linear regression to determine the relationship between them, which I've done. (explanatory variable is Wind speed)

It then asks to simulate Wind speed values according to a given distribution (which I've done) but then to use correlated simulation to predict the resultant temperatures.

After some google searches I used an the equation:
Temperature=c*Simulated Wind speed +sqrt(1-C squared)* given Wind Speed
where c is the correlation coeff.

but i also used another method, just using the regression equation:
Temp=-0.29Wind +35

I'm not sure which is right (if they are) or any other way to approach it.

Any help would be appreciated
Thanks

#### Dragan

##### Super Moderator
Well, your close, but you are not there yet. You will need an error term (Error) that is independent of "Simulated Wind Speed" (X) to create Temperature on the right-hand side of the equation. For example, if you draw independent random samples from a Standard Normal Distribution (Mu=0, Var=1), then for sure the correlation between Temp and Wind Speed will be "c". However, you cannot use "given Wind Speed", you need to use an Error term (E) from the statistical distribution. In short, that variable needs to be the error term (independent of X) associated with the statistical distribution.

If need be, when you simulate the data, just conduct a linear transformation on the data and it will make no difference because the Pearson Correlation is invariant to linear transformations i.e., it will not change.

#### rogojel

##### TS Contributor
hi,
would using the regression equation work if I added a term containing a data point from the residuals? E.g. If the residials were normally distributed with mean 0 and sd of 1.5, say, then Temp=-0.29Wind +35+eps where eps is N(0,1.5)?

regards

#### Dragan

##### Super Moderator
hi,
would using the regression equation work if I added a term containing a data point from the residuals? E.g. If the residials were normally distributed with mean 0 and sd of 1.5, say, then Temp=-0.29Wind +35+eps where eps is N(0,1.5)?

regards
Well, yes. However, the OP has not identified the statistical distribution that the random deviates are being drawn from. Basically, the two of us are assuming that the random deviates are being drawn from a standard normal distribution, which implies that the sum of the two standard normal independent random variables are also normally distributed, which is correct.

However: Suppose X and E are both independent Standard Uniform RVs distributed as: X, E are iid U~[-Sqrt[3.0], Sqrt[3.0]]. The algorithm to obtain the correct correlation (between Y and X) still works i.e., Y = r*X + Sqrt[1-r**2]*E where X and E both have a mean of 0 and a Standard Deviation of 1.

The potential problem is that if the shape parameters (skew, kurtosis) of Y are of concern. If this is the case, then Y (in general) cannot be Uniformly distributed because of the Central Limit Theorem (CLT), albeit the correlation will still be r. For example, if X and E have some specified correlation of r then Y is distributed as somewhere between a Triangular and Uniform Distribution because of the CLT.

#### Juliana

##### New Member
Well, your close, but you are not there yet. You will need an error term (Error) that is independent of "Simulated Wind Speed" (X) to create Temperature on the right-hand side of the equation. For example, if you draw independent random samples from a Standard Normal Distribution (Mu=0, Var=1), then for sure the correlation between Temp and Wind Speed will be "c". However, you cannot use "given Wind Speed", you need to use an Error term (E) from the statistical distribution. In short, that variable needs to be the error term (independent of X) associated with the statistical distribution.

If need be, when you simulate the data, just conduct a linear transformation on the data and it will make no difference because the Pearson Correlation is invariant to linear transformations i.e., it will not change.
Thanks so much for your help


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### Akka Clustering and Remoting: Application Scaling

In my previous post (Akka Clustering and Remoting: The Experiment), I defined a ping-pong application and deployed it into a local JVM cluster. In this post, I want to examine how we can scale this application into a vendor's cloud (e.g. Amazon or Rackspace).

However when pushing into the cloud, it is wise to remove any reliance upon a single cloud vendor. So, I'll also look at how that may be accomplished.

Tags: akka

### Akka Clustering and Remoting: The Experiment

This blog post is based on some concepts that I was using a few years ago to build clusters hosting distributed Actor applications. We will build an example application and scale it into a cloud evironment.

In general, I'll be focused on using Amazon for our cloud deployment. However, I'll also consider what happens if our cloud vendor fails in some way. Whilst such events may be rare, they do occur. So when we scale our Akka application, I will consider how we can avoid reliance upon any single cloud vendor.

Tags: akka

### Volatility Plugin Contest

Results are in for the 1st Annual Volatility Framework Plugin Contest - and I'm happy to say that I came joint fourth.

Tags: digital forensics, volatility

### Month of Volatility Plugins

I was just looking over the Month of Volatility Plugin posts published by the Volatility team, and stumbled across the post MoVP 4.4 Cache Rules Everything Around Me(mory) by AAron Walters.

Not only does it have a nice overview behind the development of the Volatility 2.3 dumpfiles plugin, but (and very much to my surprise!), it has a very complementary historical overview of my implementation work here.

Thanks to the Volatility team for providing such a great memory analysis framework. :-)

Tags: digital forensics, volatility

### Honeynet Reverse Engineering Challenge

Recently, I've succeeded in coming joint first in Honeynet challenge 11: Dive Into Exploit by Georg Wicherski. Both of the winning answers are worthwhile reading as they supply highly complementary analyses (Ruud rightly pipped myself at the post here as he managed to succeed in getting gdlog to behave).

This was essentially a reverse engineering challenge with a serious piece of cryptography thrown in for good measure!

Tags: honeynet, digital forensics, reverse engineering

### Clock Descriptions

This is the final article in a series of articles related to analysing the Honeynet Log Mysteries Challenge data set by applying the Scientific Method (see Casey2009 and Carrier2006) and utilising data visualisation (see Conti2007 and Marty2008).

With this final blog article, we shall use the logging events present in sanitized_log/apache2/www-*.log to build a reference clock description (see An Improved Clock Model for Translating Timestamps by Florian Buchholz). In doing this, we are then able to provide date and time estimates to events in terms of a standard reference clock.

Tags: honeynet, digital forensics, data visualisation, clock descriptions

### Wordpress Versioning: Part 2

This is part of a series of articles related to analysing the Honeynet Log Mysteries Challenge data set by applying the Scientific Method (see Casey2009 and Carrier2006) and utilising data visualisation (see Conti2007 and Marty2008).

Using just the logging events present in sanitized_log/apache2/www-*.log, this article explores how we might provide probability estimates (via naive Bayesian classifiers) for the version numbers of Wordpress and its plugins.

In the final blog article to this series, we shall look at how the work of Florian Buchholz (eg. see An Improved Clock Model for Translating Timestamps) can be used to measure logging event times relative to a suitable reference clock description.

Tags: honeynet, digital forensics, data visualisation, wordpress

### Estimating Apache2 Restarts

This is part of a series of articles related to analysing the Honeynet Log Mysteries Challenge data set by applying the Scientific Method (see Casey2009 and Carrier2006) and utilising data visualisation (see Conti2007 and Marty2008).

Using just the logging events present in sanitized_log/apache2/www-*.log, this article explores how we might estimate the Apache2 restart times by reconstructing the scoreboard worker thread data structure.

In the final blog article to this series, we shall look at how the work of Florian Buchholz (eg. see An Improved Clock Model for Translating Timestamps) can be used to measure logging event times relative to a suitable reference clock description.

Tags: honeynet, digital forensics, data visualisation, apache2, score board

### Wordpress Versioning: Part 1

This is part of a series of articles related to analysing the Honeynet Log Mysteries Challenge data set by applying the Scientific Method (see Casey2009 and Carrier2006) and utilising data visualisation (see Conti2007 and Marty2008).

Using just the logging events present in sanitized_log/apache2/www-*.log, this article explores how we might estimate the version numbers for Wordpress and its plugins. A latter article will explore how to add probabilistic certainties to such versioning estimates.

Tags: honeynet, digital forensics, data visualisation, wordpress

### Tagging and Timelines: Part 2

This is part of a series of articles related to analysing the Honeynet Log Mysteries Challenge data set by applying the Scientific Method (see Casey2009 and Carrier2006) and utilising data visualisation (see Conti2007 and Marty2008).

In Tagging and Timelines: Part 1 we had introduced a tagging algorithm that utilised Debian's package tags (ie. debtags). This blog post explores how we may use these tagging relationships, along with an interactive timeline (implemented using Protovis), to explore and analyse the auth.log sudo events.

Tags: honeynet, digital forensics, data visualisation, timeline

### Tagging and Timelines: Part 1

This is part of a series of articles related to analysing the Honeynet Log Mysteries Challenge data set by applying the Scientific Method (see Casey2009 and Carrier2006) and utilising data visualisation (see Conti2007 and Marty2008).

Using a tagging algorithm that utilises Debian's package tags (ie. debtags), this blog post explores how we may quickly and objectively classify logging events using tagging. The next post introduces an interactive timeline (implemented using Protovis) that we shall use to further explore and analyse the auth.log sudo events.

Tags: honeynet, digital forensics, data visualisation, tagging

### Apache2 Version Analysis: Ubuntu Packaging

During a recent attempt at answering the Honeynet Log Mysteries Challenge, I wrote a series of reasoned analyses for the supplied Honeynet logging data. Unfortunately, teaching workloads stopped me from submitting any realistic challenge answer.

Inspired by the idea of applying the Scientific Method to Digital Forensics (see Casey2009 and Carrier2006) and using data visualisation (see Conti2007 and Marty2008), I set about attempting to apply the same principles to analysing the Log Mysteries data sets.

In the blog post Apache2 Version Analysis: Data Visualisation, we estimated that Apache2 is at a revision < 596448 (ie. tag release is ≤ 2.2.6) and, under minimal additional assumptions, we also estimated that Apache2 was at a revision ≥ 420983 (ie. tag release is ≥ 2.2.3). Obviously, these revision and tag numbers are taken relative to the Apache2 subversion repository and not the Ubuntu package repository.

As Ubuntu packages (like Debian packages) essentially consist of the original (pristine!) upstream source code (eg. a tagged release straight from the Apache2 subversion repository) with a patch that is to be applied on installation, we clearly have some extra work to do here!

Tags: honeynet, digital forensics

### Apache2 Version Analysis: Data Visualisation

During a recent attempt at answering the Honeynet Log Mysteries Challenge, I wrote a series of reasoned analyses for the supplied Honeynet logging data. Unfortunately, teaching workloads stopped me from submitting any realistic challenge answer.

Inspired by the idea of applying the Scientific Method to Digital Forensics (see Casey2009 and Carrier2006) and using data visualisation (see Conti2007 and Marty2008), I set about attempting to apply the same principles to analysing the Log Mysteries data sets.

In the blog post Apache2 Version Analysis, we presented an argument that purported to provide an upper bound estimate on the version of Apache2 that was present on the Log Mysteries web server. It was pointed out, in that blog post, that this version estimate had a subtle error that needed to be located and fixed. In this article, we aim to rectify this situation by using a timeline to correctly estimate that Apache2 is at a revision < 596448 (ie. tag release is ≤ 2.2.6). Under minimal additional assumptions, we can also deduce that Apache2 is at a revision ≥ 420983 (ie. tag release is ≥ 2.2.3).

Tags: honeynet, digital forensics, data visualisation, timeline

### Apache2 Version Analysis

During a recent attempt at answering the Honeynet Log Mysteries Challenge, I wrote a series of reasoned analyses for the supplied Honeynet logging data. Unfortunately, teaching workloads stopped me from submitting any realistic challenge answer.

Inspired by the idea of applying the Scientific Method to Digital Forensics (see Casey2009 and Carrier2006), I set about attempting to apply the same principles to analysing the Log Mysteries data sets.

Using just the apache2/www-* logs from the Log Mysteries Honeynet challenge, this blog post demonstrates how we can define upper bounds on the version of Apache2 used and, more interestingly, data regarding Apache's worker threads. We are also able to establish how to obtain the log events with microsecond (instead of just second) timestamp accuracy.

Tags: honeynet, digital forensics


text:
# Coefficients of potential

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In electrostatics, the coefficients of potential determine the relationship between the charge and electrostatic potential (electrical potential), which is purely geometric:

${\displaystyle {\begin{matrix}\phi _{1}=p_{11}Q_{1}+\cdots +p_{1n}Q_{n}\\\phi _{2}=p_{21}Q_{1}+\cdots +p_{2n}Q_{n}\\\vdots \\\phi _{n}=p_{n1}Q_{1}+\cdots +p_{nn}Q_{n}\end{matrix}}.}$

where Qi is the surface charge on conductor i. The coefficients of potential are the coefficients pij. φi should be correctly read as the potential on the i-th conductor, and hence "${\displaystyle p_{21}}$" is the p due to charge 1 on conductor 2.

${\displaystyle p_{ij}={\partial \phi _{i} \over \partial Q_{j}}=\left({\partial \phi _{i} \over \partial Q_{j}}\right)_{Q_{1},...,Q_{j-1},Q_{j+1},...,Q_{n}},}$

or more formally

${\displaystyle p_{ij}={\frac {1}{4\pi \epsilon _{0}S_{j}}}\int _{S_{j}}{\frac {f_{j}da_{j}}{R_{ji}}}.}$

Note that:

1. pij = pji, by symmetry, and
2. pij is not dependent on the charge,

The physical content of the symmetry is as follows:

if a charge Q on conductor j brings conductor i to a potential φ, then the same charge placed on i would bring j to the same potential φ.

In general, the coefficients is used when describing system of conductors, such as in the capacitor.

## Theory

System of conductors. The electrostatic potential at point P is ${\displaystyle \phi _{P}=\sum _{j=1}^{n}{\frac {1}{4\pi \epsilon _{0}}}\int _{S_{j}}{\frac {\sigma _{j}da_{j}}{R_{j}}}}$.

Given the electrical potential on a conductor surface Si (the equipotential surface or the point P chosen on surface i) contained in a system of conductors j = 1, 2, ..., n:

${\displaystyle \phi _{i}=\sum _{j=1}^{n}{\frac {1}{4\pi \epsilon _{0}}}\int _{S_{j}}{\frac {\sigma _{j}da_{j}}{R_{ji}}}{\mbox{ (i=1, 2..., n)}},}$

where Rji = |ri - rj|, i.e. the distance from the area-element daj to a particular point ri on conductor i. σj is not, in general, uniformly distributed across the surface. Let us introduce the factor fj that describes how the actual charge density differs from the average and itself on a position on the surface of the j-th conductor:

${\displaystyle {\frac {\sigma _{j}}{\langle \sigma _{j}\rangle }}=f_{j},}$

or

${\displaystyle \sigma _{j}=\langle \sigma _{j}\rangle f_{j}={\frac {Q_{j}}{S_{j}}}f_{j}.}$

Then,

${\displaystyle \phi _{i}=\sum _{j=1}^{n}{\frac {Q_{j}}{4\pi \epsilon _{0}S_{j}}}\int _{S_{j}}{\frac {f_{j}da_{j}}{R_{ji}}}}$

can be written in the form

${\displaystyle \phi _{i}=\sum _{j=1}^{n}p_{ij}Q_{j}{\mbox{ (i = 1, 2, ..., n)}},}$

i.e.

${\displaystyle p_{ij}={\frac {1}{4\pi \epsilon _{0}S_{j}}}\int _{S_{j}}{\frac {f_{j}da_{j}}{R_{ji}}}.}$

## Example

In this example, we employ the method of coefficients of potential to determine the capacitance on a two-conductor system.

For a two-conductor system, the system of linear equations is

${\displaystyle {\begin{matrix}\phi _{1}=p_{11}Q_{1}+p_{12}Q_{2}\\\phi _{2}=p_{21}Q_{1}+p_{22}Q_{2}\end{matrix}}.}$

On a capacitor, the charge on the two conductors is equal and opposite: Q = Q1 = -Q2. Therefore,

${\displaystyle {\begin{matrix}\phi _{1}=(p_{11}-p_{12})Q\\\phi _{2}=(p_{21}-p_{22})Q\end{matrix}},}$

and

${\displaystyle \Delta \phi =\phi _{1}-\phi _{2}=(p_{11}+p_{22}-p_{12}-p_{21})Q.}$

Hence,

${\displaystyle C={\frac {1}{p_{11}+p_{22}-2p_{12}}}.}$

## Related coefficients

Note that the array of linear equations

${\displaystyle \phi _{i}=\sum _{j=1}^{n}p_{ij}Q_{j}{\mbox{ (i = 1,2,...n)}}}$

can be inverted to

${\displaystyle Q_{i}=\sum _{j=1}^{n}c_{ij}\phi _{j}{\mbox{ (i = 1,2,...n)}}}$

where the cij with i = j are called the coefficients of capacity and the cij with i ≠ j are called the coefficients of electrostatic induction.[1]

The capacitance of the above two-conductor example system can be expressed in terms of the cij as

${\displaystyle C={\frac {c_{11}c_{22}-c_{12}^{2}}{c_{11}+c_{22}+2c_{12}}}}$

(the system of conductors can be shown to have similar symmetry cij = cji.)

## References

1. ^ L. D. Landau, E. M. Lifshitz, and L. P. Pitaevskii, Electrodynamics of Continuous Media (Course of Theoretical Physics, Vol. 8), 2nd ed. (Butterworth-Heinemann, Oxford, 1984) p. 4.