text:
## Sunday, December 21, 2014

### Medieval Cyrllic (aka "Old Church Slavonic", "Old Bulgarian") fonts in LibreOffice

The only way I've seen this work is to take the TTF fonts created for Microsoft Word and adapt them. LibreOffice appears to require not only the TTF files, but also the associated AFM and PFB files. These cannot be created perfectly, but with font-forge, it's possible to produce versions of AFM and PFB which are reasonably close.
1. Copy the TTF files into /home/foo/.fonts
2. Open one of the TTF's in Font Forge
3. Select "Generate Font", using the PFB option. An AFM will automatically be created
4. Make sure all three versions of the file, TTF, AFM, and PFB files are in the /home/foo/.fonts
5. Restart X
6. Open LibreOffice -- the font should be in the font list
7. Profit

### locale issue

Full implementation of these fonts requires multi-byte encoding -- there are more than 256 glyphs available. This means of course dealing with locales. I don't like to use UTF-8 because, when encoding, it's inefficient. The best possible solution for a locale with these fonts appears to be "C". I checked my locale with the following (reports according to information in /etc/profile.d/locale.sh ). PAM (which I hate), apparently however stats /etc/environment. Plenty more can be read here.

$locale LANG=C LC_CTYPE="C" LC_NUMERIC="C" LC_TIME="C" LC_COLLATE="C" LC_MONETARY="C" LC_MESSAGES="C" LC_PAPER="C" LC_NAME="C" LC_ADDRESS="C" LC_TELEPHONE="C" LC_MEASUREMENT="C" LC_IDENTIFICATION="C" LC_ALL= Or, one by one...$ echo $LANG C$ echo $LC_CTYPE C The LC_ALL variable is one I've wanted to investigate more fully. For example, I was reading on Stack Exchange that LC_ALL can override the settings of the other variable settings. manually updating locale variables There are several programs which update locale settings. I prefer to hand edit configurations. The primary Arch file to customize these settings is /etc/locale.conf, which generally must be created. Other distros use /etc/default/locale. Alternatively, suppose I just wanted to set one or two of these variables? I'd likely export them to the kernel directly from ~.bashrc (as I do my TexLive path). Using LC_ALL as an example, and assuming a more intelligent user...$ nano .bashrc
export LC_ALL="C"
Masochists or less intelligent users might want to use...
nano .bashrc export LC_ALL="en_US.UTF-8" ## Monday, December 15, 2014 ### [solved] "disabled" printers in cups, "rendering complete" PT II With an HP printer, if you click "print", but have left anything disconnected... you're going to get pissed. CUPS should simply print the job once the printer cable is reconnected. But instead of helpfully printing, CUPS is much more likely to invoke TWO horrible-to-undo factors... simultaneously. 1. CUPS invokes a "disabled" status for the printer and does not reveal this. When you reconnect the printer, the document does not print, but the icon will only (unhelpfully) indicate "rendering complete" with a green "pause" status for the printer. 2. You'll think, "I just need to delete the document and try again now that the cable is connected". YES, you'll have to delete the document from the queue or the problem can't be fixed. (Use lpstat -o to get the job number and then cancel [job number] to eliminate it from the queue). NO, the problem is not yet fixed, and if you try to print again, you need to delete those attempts as well. Delete all print jobs and re-enable the printer using one of the two options below. ### option 1 (5 minutes) If a person is extremely fortunate, CUPS was installed with CUPS-specific permissions and group categories aligned. There are three layers to these, the first layer being correct permissions for loopback/localhost. Users can check this by attempting to access the CUPS browser-based administration page, running out of port 631, ie, http://localhost:631/. If that works, attempt to clear the disabled printer status as follows. • Find your paused printer and click on it. • Under the "maintenance" options for that printer, click on "resume". This is what re-enables the printer. • Authenticate to activate changes. Typically the user is "root" and then root's password. At this stage, printing should work again. If authentication failed, either skip to Option 2 below, or take the time* to untangle the group/member permissions (these are the second and third layers of CUPS configuration -- see "cups printer permissions" below) and then go back to the CUPS administration page, once complete. *an entire afternoon ### option 2 (15 minutes) Remove and reinstall your printer, which hopefully is not an HP. Find your USB port for the printer (lsusb) and then, eg... # lpadmin -x Officejet_Pro_8500_A910 hp-setup -i --auto 001:004
If not an HP printer, then you will likely never have this "disabled" printer problem, but if you do have to reinstall a non HP printer, then the easiest way I've found is, eg...
# lpadmin -x Brother # lpadmin -p Brother -E -v usb:/dev/usb/lp0 -m brother.ppd

### summary

1. Cancel all print jobs. The fix might work without this, but it's unlikely. Find print job numbers using # lpstat -o and then # cancel [print number], one by one. You will see no change yet in the "rendering complete" status, but print jobs need to be cleared for the "rendering complete" status to subsequently be cleared.
2. "resume" the printer in the CUPS browser interface (if available), or remove and reinstall the printer using the terminal. Either way, "rendering complete" should disappear at this step.
3. Verify that CUPS changes have succeeded by attempting to print or, in a terminal, type "lpstat -p": the printer name should be there and have a status of "idle".

### cups printer permissions (in progress)

Users will often only learn their CUPS configuration is misaligned when CUPS authentication fails at the final step of a long process that otherwise seemed to be successful. Any or all of the layers below can be the cause of the problem. Layer 1: loopback/localhost Sadly, CUPS is a network, not a standalone, print server. This means one must disable a percentage of their loopback protections if they want to use CUPS and the CUPS administration page. Outrageous, but true. Loopback is not dealt with on this page. Layer 2: groups
Layer 3: permissions Layer 4: /etc/cups/cups.conf (not always) Most times, nothing needs to be done to this file. When it does, the most typical adjustment involves.

### x crashes, video crashes, mouse crashes, kernel panics

A friend has an old HP box that was running Arch. He was experiencing system lock-ups using Wikimapia in concert with Google Maps in a browser. These programs paint a lot of polygons when scrolling and the kernel panics seemed to show memory leaks or other unauthorized writing to the drive. The failures were to varieties: 1) lockups, and 2) exit to terminal with kernel panics. Some possibilities:
1. xorg setting for video card
2. xorg setting for mouse
3. browser leaks with multiple many-polygon pages open (maps)
4. the old Intel 82G33/G31 integrated controller card being overwhelmed
5. ?

### logs

We're looking for two main log types: Xorg crashes, and Kernel crashes. Xorg is the easiest -- hasn't changed much over the years. We can still find Xorg logs in /var/log/Xorg.0.log.old and copy to our user directory to read them in any text editor. Failures stand out, and there is usually enough information to start modifying one's xorg.conf file to fix whatever's wrong. In the case of my friend, it appears there was nothing failing and writing to Xorg.log, at least on a first-look.

Kernel crashes. During crashes, writing can be inconsistent; we can't be certain we'll have information. Additionally, journald crash logs are written in binary and, further, compressed, and so require the journalctl client to read whatever's in there (and of course "whatever's in there" can become corrupted during a panic). So it's 50-50 if we can see anything in these logs. IMO, verifying a corruption-free log is the place to begin.
# journalctl --verify
...in the case of my friend's logs, this revealed a plethora of corruptions at times I could not decipher, but may have corresponded to the panics.

Given all of this, it appeared the best thing to do was get some text readable log information.
# nano /etc/systemd/journald.conf
Storage=none
ForwardToSyslog=yes
...next crash, I should be able to see if there's anything out there in human readable text. Meanwhile...
# journalctl -b
... and look for errata.

### video card

On the video card front, his old Intel 82G33/G31 is onboard and shares memory (fatal), but also appears to have some VRAM. No GPU.

## Friday, December 5, 2014

### [solved] (kinda) magical cups disappearance

Edit: I eventually rebooted after the CUPS reinstall and ran
# systemctl list-unit-files |grep cups
This time, and I'm not sure why, CUPS units appeared. One unit was org.cups.cupsd.service. Of course! A more complicated name for the service... how could I not guess this? So now, instead of the simpler...
# systemctl start cups
...we now have the impossible to remember...
# systemctl start org.cups.cupsd.service
...thanks a million, CUPS team. More keystrokes and slips of paper, perhaps that's the Linux legacy. At least this one is solved for now.

Edit 2: Evince not printing. Everything appears fine, but only blank pages result. Check it with a direct print. First command to get a list of the printer names, second command to directly print the file. In this case, suppose the name of the printer is "Foo", and the file to be printed is "somefile.pdf"...
# lpstat -p
# lp -d Foo somefile.pdf
If it prints this way, but not in Evince, it's got the f*cking bug.

I recently (12/5/2014) updated Arch and CUPS disappeared. It wasn't even there in the list of units. I ran...
# systemctl list-unit-files |grep -i cups
org.cups.cupsd.path
...which is just the CUPS scheduler, so no printers appeared. (The reason to use list-unit-files is it reveals any units, enabled or disabled). A check with
# pacman -Ss cups
showed cups was already installed. I reinstalled it, but still no appearance in the systemd list. Hmmm...

### startup service

Then I recalled I'd made a custom startup service to remove the realtek module so it wouldn't continue sending errors. Could this be the problem?
# cat /etc/systemd/system/foostartup.service
[Unit]
Description=startup actions

[Service]
Type=oneshot
RemainAfterExit=no
ExecStart=/usr/bin/sleep 10s
ExecStart=/usr/bin/rmmod ums_realtek

[Install]
WantedBy=multi-user.target
But no, there was nothing in there which would effect CUPS.

## Saturday, November 29, 2014

### [solved] arch - update and java

Following Oracle's purchase of Java (2010), Java users can't be certain when Oracle attorneys or developers might make users' lives uncomfortable. If one wants Java functionality however, Oracle can't be avoided entirely. I am not a lawyer, but Oracle's open-source version of Java, OpenJDK, may be the most legally prudent Java option. That said, not every application plays nice with OpenJDK, of course, or Oracle wouldn't be able to profit from licensing its more user-friendly proprietary versions of Java.

What has the above meant to me operationally? When upgrading Arch with OpenJDK onboard, I've sometimes experienced conflicts which required a solution of, 1) uninstalling Java, 2) running the Arch update(s), and, 3) reinstalling or upgrading to the latest OpenJDK.

Arch update Java conflicts may look something like these (during pacman -Syu):
error: failed to commit transaction (conflicting files)
java-runtime-common: /usr/bin/java exists in filesystem
java-runtime-common: /usr/bin/keytool exists in filesystem
java-runtime-common: /usr/bin/orbd exists in filesystem
java-runtime-common: /usr/bin/pack200 exists in filesystem
java-runtime-common: /usr/bin/policytool exists in filesystem
java-runtime-common: /usr/bin/rmid exists in filesystem
java-runtime-common: /usr/bin/rmiregistry exists in filesystem
java-runtime-common: /usr/bin/servertool exists in filesystem
java-runtime-common: /usr/bin/tnameserv exists in filesystem
java-runtime-common: /usr/bin/unpack200 exists in filesystem
java-runtime-common: /usr/lib/jvm/default exists in filesystem
java-runtime-common: /usr/lib/jvm/default-runtime exists in filesystem
Errors occurred, no packages were upgraded.

The shortest path appears to be removing "java-common". Not so fast: OpenJDK requires java-common as a dependency; pacman typically will not allow its removal. The solution is to remove OpenJDK (at this writing version 7), update the system, and then reinstall OpenJDK:
# pacman -Rns jre7-openjdk
# pacman -Syu
# pacman -S jre7-openjdk

Applications (eg, geogebra, icedtea-web) that bark at this removal may also have to be removed prior to the Arch update, and then reinstalled (after jre).

### location in system

$ls -an /usr/bin/java /usr/bin/java -> /usr/lib/jvm/default-runtime/bin/java$ locate /bin/java
locate /bin/java
/usr/bin/java
/usr/bin/javaws
/usr/lib/jvm/java-8-openjdk/jre/bin/java
/usr/lib/libreoffice/ure/bin/javaldx
/usr/share/icedtea-web/bin/javaws

$ls /usr/lib/mozilla/plugins IcedTeaPlugin.so libflashplayer.so [missing java-plugin libnpjp2.so] # find -name libjava.so /usr/lib/jvm/java-8-openjdk/jre/lib/amd64/libjava.so You can't find libnpjp2.so because you don't have normal java installed. Typically, you make a soft link between libnpjp2.so and the mozilla plugin directory. But in this case WITH OPEN JDK, our java soft link for mozilla (when we need it) is the icedtea plugin so we're actually set. All you have to do is go into "Add-Ons" in your browser and enable/disable it. ### LibreOffice After an Arch OpenJDK update, the LibreOffice portion sometimes still will notice you... Optional dependencies for libreoffice-still java-runtime: adds java support java-environment: required by extension-wiki-publisher and extension-nlpsolver ...telling you for sure LibreOffice didn't detect OpenJDK. I opened LibreOffice -->Tools --> Options --> Advanced. I selected the radio button for the Oracle option and then "OK". These actions seemed to activate Java. ### Blackboard and Pipelight apps Only Firefox has the stuff needed to process Moonlight, instead of Silverlight. Software must be installed that allows geolocating and so forth. These can be turned on and off by creating a softlink. On the Blackboard account, also use Firefox (JRE). ln -s /usr/lib/pipelight/libpipelight-silverlight5.1.so /usr/lib/mozilla/plugins/libpipelight-silverlight5.1.so ## Sunday, November 16, 2014 ### [solved] xbacklight -- try to adjust your backlight to preserve it I recently had an LCD display burn-out its backlight element and had the following consideration: •$60 (1.5 hrs) Replace screen and backlight combo
• $12 (5 hrs) Replace backlight only On my current schedule,I did the$60 but, since I was doing it for the backlight, I wanted to be sure I adjusted the backlight to a low setting going forward. The commands I'm aware of are
• xgamma
• xbacklight
• xrandr
I've regularly used xgamma and xrandr in the past, but was never sure what I was adjusting -- the lcd, the backlight, or some blend. For example, with the new display, even when I set the gamma very low, eg
$xgamma -gamma 0.1 ...I would see what appeared to be a full-intensity backlight combined with a low contrast LCD setting. A similar problem appeared if I used xrandr, eg$ xrandr --output LVDS --brightness 0.2
... which would give a bright haze (the backlight?) overlaying a barely visible display underneath. I wanted to definitively adjust the backlight so I could begin to untangle what was what. "Xbacklight" seemed the most logical choice. Murphy arrived immediately.

$xbacklight No outputs have backlight property Checking the arch wiki on backlight control, we get the mysterious information: All methods are exposed to the user through /sys/class/backlight and xrandr/xbacklight can choose one method to control brightness. It is still not very clear which one xbacklight prefers by default. There is a note about how to fix the error message if one is using Debian, but of course Arch is not Debian. I did find the following directory however: /sys/class/backlight/acpi_video0/ Based on what I read here from greengeek, I did the following with a nice dimming effect (required root) # echo 1 > /sys/class/backlight/acpi_video0/brightness Echoing a value obviously doesn't use an application (eg., xbacklight), but it appears to set the backlight effectively, and uses settings between 0 and 2. ### final command combination With the new LCD and backlight, a crisp setting appears to be$ xgamma -gamma 0.4
# echo 0 > /sys/class/backlight/acpi_video0/brightness

### xrandr and external displays or projectors

A person can get a printout of possible display settings for an external device attached to their desktop or laptop by simply typing $xrandr. Using these, a person can set exact refresh settings for secondary displays, however, I haven't found backlight control of these displays. Still, xrandr is great to simply turn the display/projector on and off (with the proper screen resolution). Note the screen resolution of your laptop (eg. 1200x800)and send it to a projector...$ xrandr --output VGA-0 --mode "1280x800" [initiates external video]
$xrandr --output VGA-0 --off [terminates external video] If I don't put the quotation marks around 1280x800, xrandr will bark at me that the resolution isn't found (most projectors don't natively have it). ## Sunday, August 24, 2014 ### Brother HL-2275DW Links: Arch instructions :: Brother Network Guide (PDF) As always, handy commands: LIST OF PENDING PRINT JOBS # lpstat -o CANCEL ALL PENDING PRINT JOBS # cancel -a Cancel -a sometimes doesn't work. In that case, one must individually cancel each named printjob, eg "cancel Brother-001", "cancel Brother-002", etc. ### USB connection (10 minutes) Connect a known-good printer using a USB cable. Turn on the printer. Next, go to this Arch page which lists the connection steps. Here is an abbreviated version, but note there are a few problems in 2015: 1. I have CUPS but a2ps is also needed: #pacman -S a2ps. 2. Reboot (or use systemctlto make sure CUPS daemon loads and is running. If users have good knowledge of systemctl command, check CUPS with systemclt or simply run any CUPS command and see what happens, eg...$ lpstat -p
...indicates CUPS is not yet running.
# systemctl list-unit-files |grep -i "cups"
org.cups.cupsd.path enabled
cups-browsed.service disabled
org.cups.cups-lpd@.service static
org.cups.cupsd.service enabled
org.cups.cups-lpd.socket disabled
org.cups.cupsd.socket enabled
The lpd-socket is disabled, because I'm not on a network. It's not necessary. For normal stand-alone usage in this kludge, I only need cupsd.service. So I disable any lpd (network) services, browsed services, etc.
# systemctl disable org.cups.cups-lpd@service
# systemctl start org.cups.cupsd.service
Now I can browse to the CUPS administration page (http://localhost:631). CUPS is running.
3. $yaourt brother-hl2270dw 4. Navigate to CUPS: http://localhost:631. 5. Click the Administration tab then click the Add Printer button. The username is "root" and the password is the root password of the user's computer. Follow the steps. ### USB connection [fail version (4 hrs)] I went to openprinting.org, typically helpful with Brothers, but this time filled with gobbledy gook and an empty PPD. The order of installation was supposed to be the printer and then the cupswrapper. 1. Downloaded and unpacked the DEB's for the cupswrapper and the lprdriver. This was weird, since no "cupswrapper" is typically needed for a Brother, just a PPD. 2. Found the PPD in the kludge of unpacked folders, rooted up and copied the PPD as /usr/share/cups/model/brother.ppd, then chowned it to 0:0 and chmodded it to 755 3. # lpadmin -p Brother -E -v usb:/dev/usb/lp0 -m brother.ppd 4. restarted CUPS and attempted to print. At first it looked promising, but then it exited, unable to locate the file, "/usr/lib/cups/filter/brother_lpdwrapper_BrGenML1". That file was in the unpacked kludge and I copied it to /usr/lib/cups/filter/, and chowned it to 0:0. Restarted CUPS and tried another print but received "waiting for printer to become available" status message. 5. Verified the "Brother" entry generated during installation in /etc/cups/printers.conf looked normal. No obvious problems. 6. Forced a testprint... cat /etc/printcap |lp -d Brother. Not working, so lpadmin -x Brother ### WiFi connection Unattempted ## Friday, August 8, 2014 ### [solved] yet another CUPS related failure -- interference with xsane. We've all encountered the problem with Xsane where it fails to detect a properly attached USB scanner. Many times this is due to an error in permissions around the scanning group -- the scanner will only be detected as root. Here's a variant: a detection fail in both root or user modes due to CUPS. In my system, if CUPS is running, the scanner cannot be detected in user or root. No informative error message explaining this will be displayed. There are many ways to determine if the CUPS daemon is running, most involving root. The fastest way is to remember "I just used the printer", but another way from user-space is:$ lpstat
lpstat returns this message when CUPS is not running, and will return a blank line if CUPS is running.

Depending on one's distribution, disable CUPS with...
# systemctl stop cups
Once CUPS is deactivated, Xsane should again detect the scanner in user mode if permissions are properly set.

CUPS accesses stand-alone boxes through loopback privileges into localhost and the CUPS daemon runs under root. Looping-back has associated permission locks which apparently block USB detection, not sure. Anyway, turn CUPS off and scan normally.

Editorial: Since the majority of Linux users are stand-alone users with non-network printers, I consider it a conceit of CUPS developers not to have created a simple stand-alone variant which doesn't need the spaghetti or security issues of loopback privileges. When one considers that the CUPS code is 20 years mature, that its PPD's are actively updated by others, and that only a few lines of code are likely necessary to access USB ports, it becomes annoying. Currently, many CUPS installations require more manipulation of groups than most Linux users possess. More importantly are the security liabilities created by loopback access. Few advanced users, and probably no average users, possess the significant PAM, LDAP, port scrambling, ipchains, etc, knowledge to be certain they've closed less obvious loopback security holes. By the normal desire of Linux users to print, and the lack of any direct stand-alone solution, it's possible many of our systems are quietly compromised.

## Thursday, August 7, 2014

### [solved] CUPS "rendering completed" errors PT I

Editorial: Stand alone systems with, say, a USB printer attached, are forced to behave like a network when printing with CUPS. This faux-network process on stand-alone systems is one of looping back ("loopback") to one's system ("localhost") -- occasionally a complicated process, depending on port set-up and permissions. Added to this are network security settings since one is opening one's ports "as if" on a network. Entire books are written about this -- it's way over the head of the average user to configure ipchains, LDAP, PAM, port scramblers, and so on properly. Long story short, conflicts are nearly certain on a simple stand-alone printing setup due to CUPS negligence of stand-alone users. I hope that someday, although it's already been 20 years, CUPS developers will humble themselves and address a direct printing solution (in addition to their excellent network solution). /end rant

At any rate, here is a recent fail. I attempted to print a document, but forgot to attach the printer first. CUPS often provides unhelpful or misleading error messages, but no error message was generated. Rather, CUPS continued to display normal status, with a message of "rendering completed". When the printer was attached, it never printed, and no additional documents could be printed. The message that rendering was completed continued to display.

### Reinstall (10 minutes)

I verified there was still a PPD in /usr/share/cups/model, located the printer using $lsusb (in my case 001:004). then... # lpadmin -x Officejet_Pro_8500_A910$ hp-setup -i --auto 001:004
Partway through installation is root authentication. The printer installs perfectly and is back to printing.

A tray icon is available as well, but it uses some RAM: /usr/bin/hp-devicesettings

### SystemGroup (hours and hours)

CUPS makes a simple conceptual distinction between administrator and user. SystemGroup is a category of users with system-administrator CUPS privileges. Group refers to CUPS users with printing privileges. Although simple in concept and perhaps great on a network, CUPS permissions cause suffering for stand-alone Linux users. Linux systems already isolate administrator (root) and user (user) access. Adding an additional CUPS layer is both redundant and rife with permission overlap possibilities.

First, deal with Group -- add your username to group lp in the system's group administration file, /etc/group. This is a beneficial overlap between Linux and CUPS. CUPS simply looks to see if you're in lp, and you can print.

Now, the harder category, SystemGroup. At the top of /etc/cups/cups-files.conf are the default user settings (typically lp, as just noted). At the bottom of the file are the SystemGroup settings. These are finnicky.
# nano /etc/cups/cups-files.conf
# Default user and group for filters/backends/helper programs; this cannot be
# any user or group that resolves to ID 0 for security reasons...
User daemon
Group lp

# Administrator user group, used to match @SYSTEM in cupsd.conf policy rules...
SystemGroup sys root

# Do we allow file: device URIs other than to /dev/null? [No]
FileDevice Yes

You want the CUPS SystemGroup membership to be root, so it mirrors your Linux authentications for administration. But unlike the user (lp) level, you don't want a CUPS "SystemGroup" line in your Linux system. That is, don't add a "SystemGroup" group to /etc/group; lp -yes, SystemGroup - no. The latter is CUPS specific only. Confusing.

## Tuesday, June 24, 2014

### cp to/from a usb from terminal

With a USB drive attached to a desktop, I attempt to copy some files from the desktop to the USB HDD. I receive "filesystem does not support symbolic links" errors and can't copy. This becomes maddening because I have no symbolic links in the files to be copied nor am I attempting to establish any symbolic links. In short, I'm asking it to copy, it's responding by claiming I'm asking something else, and that it can't do that other thing. What can we verify to help ourselves troubleshoot this mess?
• Make sure the file owners are the same, eg the same UID.
• Double check that you can fstab various MSOFT file systems
$cat /etc/fstab /dev/sdb1 /media/sdb1 ext2 uid=1000,noauto,user 0 0$ parted /dev/sdb -l
Model: USB DISK 2.0 (scsi)
Disk /dev/sdb: 1032MB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number Start End Size Type File system Flags
1 1049kB 1032MB 1031MB primary

Is this an fstab problem?

## Wednesday, April 30, 2014

### cp, dd, dump, rsync -- diff

I want to back-up some items, and have 3 requirements, plus 3 hopefuls.

1.) Back-up to an ISO, eg to "20141231_bak.iso"
2.) Able to exclude some directories from the process.
3.) Fast
4.) If possible, backup an unmounted partition to avoid any "live acquisition" write errors
5.) If possible, update the ISO with file changes.
6.) If possible, prior to, or following backup, an app which locates duplicate files.

### cp solution

For a mounted partition, cp is a reasonable option. We can take an entire data directory, say /home/foo, and safely back it up to an external HDD with a date. We would have to cycle the dumps, since there will be no indexes of changed files.
$cp -a /home/foo/. /dev/hdb/20140430 Problem: again, slow. Doesn't write to a file, eg to an ISO. Doesn't allow excluded directories. Only works on mounted drives. ### dd solution We prefer backing-up an unmounted partition since there's no chance of new data being written during the backup -- dd fits this bill. Also it's fast. Thirdly, it does exactly what we want for our format: writes from a device to a file$ dd if=/dev/hda2/ of=/home/foo/20141231_bak.iso
Problem: No directory exclusion since dd backs-up the entire partition. A second problem with duplicating the entire partition is the image includes all free space on the partition, requiring equivalent backup space to the partition. Solution: possibly use "conv=sparse" option to exclude blank space. This means, prior to backups, using something like zerofree to rapidly zero unallocated areas on the partion.

### rsync solution

Rsync is not so fast the first time it's run, but subsequent incremental back-ups can be fast, and delta transfer (-W flag) may increase speed even on a USB (as opposed to network) backup. Problem: It's live acquisition; disk must be mounted. It doesn't natively write to a file.

## Tuesday, April 8, 2014

### Is an ellipse really a conic?

I don't think so. Consider that an ellipse is supposed to have equal eccentricity on each end -- it's not supposed to be shaped like a cross section of an egg.

But now consider that a cone has a varying radius from it's base to its vertex. At the vertex of a cone, the peak of the cone, the radius is zero, at its base, the radius of the cone is however large you want to make it.

The ellipse is (supposedly) the result of cutting the cone at a SLANT. This means the radius of the cone is different at one end of the ellipse than the other. This means that the only way to have a true ellipse is to have a section of a cylinder, not of a cone. Nevertheless, they persist in calling it a "conic". Is there something I overlooked?

## Monday, March 24, 2014

### xdg-mime for media files

After I upgrade a browser or install a new file manager, clicking on links opens an undesired application: a browser, mail client, etc. These have to do with MIME settings. There are two main MIME categories: 1) local HDD files, and 2) behavior when encountering remote files via a browser.

But locating MIME types and overseeing them has been kludgy. Recently, I located xdg-mime (probably one of "xdg-utils"). Xdg-mime can apparently operate across both root or user modes. Unless admin (root) locks them out, users can apparently create their own MIME approach. I'll post back on this once I determine the syntax and file location of the oversight file (mimetypes-file) but, at first glance, xdg-mime looks to be a central way to make changes.

#### manual changes

Before resorting to xdg-mime, it may be possible to determine which files contain "MimeType", since there may be ways to directly update these files. Caches contain a lot of this kind of syntax too, so it's good to clear caches before searching:
$rm -r .cache/*$ grep -rn MimeType

## Saturday, March 15, 2014

### stop changing sh*t...

...just STOP.

We choose Linux because we like a stable OS we rarely have to upgrade or alter. But that's becoming more and more difficult. Unless I've overlooked something, even simple utilities are eventually "improved".

The latest is a bedrock of operation; dhcpcd. This has been a great application and whomever designed dhcpcd has my thanks. Unfortunately, it now appears to have been "upgraded".
Bingo.

### yaourt install

Using the yaourt install was still kind of a drag because of the compilation of the libraries. A lot of messages showed up suggesting edits to the install, but I figured any alterations I made could create subsequent errors I wouldn't have notes for, so I just let it compile.

### tilp

Probably because I didn't make the alterations, I got some error messages, but everything seemed to work OK in spite of this. Except the OS update. For that, I shut down tilp, checked the calculator again to be sure it was "on", and started tilp in root. At that point, I just dragged the new OS from the computer directory over to the calculator directory and let off the mouse. The software update program began to run and even showed a % progress reading. Once it was done, turned off tilp, disconnected and restarted calculator. Voila, software version was 3.1 and impDer available.

## Friday, January 24, 2014

### Medieval Cyrillic fonts in LaTeX (or XeLaTeX)

Links: tfm font install :: ttf fonts available :: old bulgarian lcyw

NB: A short note about WYSIWYG processor LibreOffice is at bottom.

Although analysts of Medieval Russian want to author text in modern Russian typefaces, they want their software to convert selected passages into Old Slavonic typefaces, change formatting, scale the text, and so on. These tasks could theoretically be accomplished in any good word processor. LaTeX with its immense formatting flexibility, would presumably be near the top of such a list but, unfortunately, straightforward LaTeX configuration solutions appear difficult to locate for older Cyrillic typefaces. Here's an outline of some of the steps I took.

### LaTeX - installed cyrillic fonts

LaTeX font files have an associated .tfm file. Find their directory by following the variable (TEXMFLOCAL) which points to it. The list of directories for various fonts is underneath it...
$kpsewhich --var-value TEXMFLOCAL$ ls ~/latex/2013/texmf-dist/fonts/tfm/
$unzip lcwy.zip -d ~/texmf$ texhash

### xelatex - packages

Using xelatex, the following compiled...

\documentclass[letterpaper]{article}

\usepackage{fontspec}
\usepackage{xunicode}
\usepackage{xltxtra}

\setmainfont{DejaVu Sans}

\begin{document}
Russian text block
\end{document}
... but produces a severe, sans-serif Ukrainian.

### LibreOffice - ttf

For WYSIWYG, a partial solution is true-type fonts. We can obtain fonts here for some medieval slavic fonts. One researcher particularly liked "dilyan.ttf", and "BukyVede-Regular.ttf"; he said they were accurate except for lacking diacritics. I explained he could place TTF's into LibreOffice /usr/share/fonts or ~/.fonts, directory (I prefer ~./fonts); they were immediately available on his font list the next time he opened LibreOffice.

## Monday, January 6, 2014

### [solved] zotero consistency - standalone w/browsers

After an update to Chromium, and using standalone Zotero, I no longer had Zotero icons in the URLbar at book and article sites. What a pisser --- it looks like yet another "one of those things" on the long list of problems we all face during updates. I wish I were a database designer so I didn't have to rely on database products (eg. Zotero), but that's life.

### solution

It appears the new disconnect between the browser and Zotero is a "translation" issue. I went to the Zotero site and downloaded the Chromium extension "Zotero Connector" and, voila, my URLbar icons for documents reappeared.

### citation backup - zotero

Some of us forget where we installed the data directory when we installed Zotero originally. Open Zotero then note the "Show Data Directory" button (Edit-> Preferences -> Files and Folders) which points to it. The best backup is to copy the "zotero" folder with all subdirectories (eg., "storage").

### bare bones

In a pinch, copy the file and subdirectory:
• zotero.sqlite
• "storage" subdirectory
With these, use a file manager to overwrite the vanilla versions of these after a vanilla install.

### restoration

If I only have the database, without storage, I'd have to reenter all the notes and so forth, but I'd at least have my titles and authors. Overwriting an entire install's "storage" directory and zotero sqlite is a complete restoration.


text:
## Even Ten By Ten

You have a $10\times 10$ checkerboard. How many different squares can be made using an even number of $1\times 1$ squares?
Source: mathcontest.olemiss.edu 1/28/2013

SOLUTION
This problem is similar to the problem titled “Odd Squares” dated 11/6/2006.
A smaller checkerboard $4\times 4$

How many $2\times 2$ squares in a $4\times 4$ checkerboard?
First, we draw a $2\times 2$ square at the upper left corner of the checkerboard. We notice that there are two empty units under it. We move the square down one unit at a time to form two additional $2\times 2$ squares for a total of three. The pattern is $1+\left (4-2\right )=3$.
Likewise, there are two empty units to the right of the original square. We move it one unit at a time to the right to form two additional $2\times 2$ squares for a total of three. The pattern is $1+\left (4-2\right )=3$.
In general, the number of different $x\times x$ squares in an $n\times n$ checkerboard is
$\left [1+\left (n-x\right )\right ]\left [1+\left (n-x\right )\right ]=\left [1+\left (n-x\right )\right ]^2$
A bigger checkerboard $10\times 10$
Let’s use the general formula to calculate the number of different
even squares.
$2\times 2:\left [1+\left (10-2\right )\right ]^2=9^2=81$
$4\times 4:\left [1+\left (10-4\right )\right ]^2=7^2=49$
$6\times 6:\left [1+\left (10-6\right )\right ]^2=5^2=25$
$8\times 8:\left [1+\left (10-8\right )\right ]^2=3^2=9$
$10\times 10:\left [1+\left (10-10\right )\right ]^2=1^2=1$
Total =$81+49+25+9+1=165$

Answer: $165$

format: plain


text:
# How to make mini 5 channel AUDIO MIXER (for home usage)

#### iamrdb

Joined Jul 31, 2021
6
I want to make a mini audio mixer of 5 channels.
Need circuit diagram

Last edited by a moderator:

#### ronsimpson

Joined Oct 7, 2019
1,465
Inputs, mic or line level?
"Base & Treble"? for each input or only for the output?

#### iamrdb

Joined Jul 31, 2021
6
Inputs, mic or line level?
"Base & Treble"? for each input or only for the output?
No No.. Just volume up down knob only...

#### AnalogKid

Joined Aug 1, 2013
9,353
It's not always about what you want. Make an effort - Search for 'audio mixer schematic' (without quotes) to get dozens (hundreds?) of examples. Find one you think will do what you want - which is a secret since you have given exactly zero details about the application, signals, power source, loads being driven, input voltage levels, etc. - and post it here, and we will help.

ak

#### Ian0

Joined Aug 7, 2020
3,234
It's not always about what you want. Make an effort - Search for 'audio mixer schematic' (without quotes) to get dozens (hundreds?) of examples. Find one you think will do what you want - which is a secret since you have given exactly zero details about the application, signals, power source, loads being driven, input voltage levels, etc. - and post it here, and we will help.

ak
I'll also add to AK's list - "How good does it need to be?"

#### MrChips

Joined Oct 2, 2009
24,180

1) connector
2) level
3) impedance
4) powered or not powered
5) unbalanced or balanced
6) mono or stereo
7) preamp or gain amp
8) level meter
10) mute button

#### Ian0

Joined Aug 7, 2020
3,234
The signal processing is the one thing that HAS been specified:
No tone controls, with or without parametric mid, no graphic equaliser

Then the outputs.
1) Balanced or unbalanced
2) USB
3) SPDIF
4) Effects loop

#### iamrdb

Joined Jul 31, 2021
6
I want to make a mini 5 channel AUDIO MIXER (for home usage).
I am a newbie in this section and have a minimum idea of circuit design that's why I am asking for help.
Mixer Like This ( Watch Here )
1) Components That I want to use :
3.5 mm mono female jack for input
I want to use as input :
(1) Dynamic mic
(2) Condenser Microphone
(3) 3.5mm Stereo Mic
for Stereo to Mono conversion, I will use an adapter

I want to use 5v DC mobile charger as a power supply
Need only one potentiometer for each input line (no bass or treble)
If not possible to make a circuit from the given above details then make an audio mixer for only 3.5mm Stereo Mic

Need only circuit diagram (if possible in EasyEDA) and clear list of components...

#### LowQCab

Joined Nov 6, 2012
1,096
Both the Condenser-Mic, and the Lapel-(Clip-on)-Mic,
(which BTW is not "Stereo"),
require special-considerations, and/or, a Power-Supply-Voltage sent to them for operation.

A "real" "High-End" Condenser-Mic requires "48-Volt-Phantom-Power".
Fortunately, 98% of the "Condenser-Mics" that You will see on-line are
simply constructed to "look-like" an expensive Condenser-Mic.
Some are pure-garbage, and some are actually quite high in performance.
Prices for "real" Condenser-Mics start at around ~$600.oo. This means that you really must have the Microphone FIRST, and then build an appropriate Pre-Amp specifically designed for that particular Model of Microphone. The "Clip-On" "Lapel", or "Lavalier" type Microphone is normally the best choice for getting consistent high-quality Audio for Pod-Casting / making Videos, however, these Microphones usually require Power of some sort. Some have a built-in "Button-Battery", and some require external Power, (usually ~5-Volts from a Computer Mic-Jack). The requirements of the particular Model of Mic that You choose will determine what type of Jack will be required, ( Stereo or Mono ), and whether or not a separate Power-Voltage must be supplied by the Mixer. The "Low-Impedance" "Dynamic" Microphone, ( usually a copy of the ~50-year-old, industry-standard, "Shure-SM-58" ), makes things very simple, and will provide generally "good", "average", performance with no headaches. Limiting your Power choices to ~5-Volts, requires quite a few compromises, but it can be done. Virtually all commercial Microphone-Mixers use a "Plus and Minus ~15-Volt" Power-Supply, (~30-Volts). 5-Volts doesn't give You very much "wiggle-room" to work with, and limits your choices of Amplifiers, (Op-Amps), and will have an Output that is just barely adequate for a standard "Line-Level" Input. A 5-Volt supply is also more likely to create higher Noise-Levels, ( background-Hiss ). This also means that careful setting of Levels between different Amplifier-Stages becomes critical, and may require quite a bit of "tweaking" to obtain acceptable performance levels of Distortion and Noise. A good compromise Power-Supply would be 4- Li-Ion Cells in series, which would make a Plus and Minus ~7.5-Volt Supply, (~15-Volts). Batteries are inherently "quiet", which means less Noise issues to deal with, plus, they're portable. . . . Thread Starter #### iamrdb Joined Jul 31, 2021 6 Both the Condenser-Mic, and the Lapel-(Clip-on)-Mic, (which BTW is not "Stereo"), require special-considerations, and/or, a Power-Supply-Voltage sent to them for operation. A "real" "High-End" Condenser-Mic requires "48-Volt-Phantom-Power". Fortunately, 98% of the "Condenser-Mics" that You will see on-line are simply constructed to "look-like" an expensive Condenser-Mic. Some are pure-garbage, and some are actually quite high in performance. Prices for "real" Condenser-Mics start at around ~$600.oo.

This means that you really must have the Microphone FIRST, and then build an appropriate
Pre-Amp specifically designed for that particular Model of Microphone.

The "Clip-On" "Lapel", or "Lavalier" type Microphone is normally the best choice for
getting consistent high-quality Audio for Pod-Casting / making Videos,
however, these Microphones usually require Power of some sort.
Some have a built-in "Button-Battery",
and some require external Power, (usually ~5-Volts from a Computer Mic-Jack).
The requirements of the particular Model of Mic that You choose
will determine what type of Jack will be required, ( Stereo or Mono ),
and whether or not a separate Power-Voltage must be supplied by the Mixer.

The "Low-Impedance" "Dynamic" Microphone,
( usually a copy of the ~50-year-old, industry-standard, "Shure-SM-58" ),
makes things very simple,
and will provide generally "good", "average", performance with no headaches.

Limiting your Power choices to ~5-Volts, requires quite a few compromises, but it can be done.
Virtually all commercial Microphone-Mixers use
a "Plus and Minus ~15-Volt" Power-Supply, (~30-Volts).
5-Volts doesn't give You very much "wiggle-room" to work with,
and limits your choices of Amplifiers, (Op-Amps), and will have an Output that is
just barely adequate for a standard "Line-Level" Input.
A 5-Volt supply is also more likely to create higher Noise-Levels, ( background-Hiss ).
This also means that careful setting of Levels between different Amplifier-Stages becomes critical,
and may require quite a bit of "tweaking" to obtain
acceptable performance levels of Distortion and Noise.

A good compromise Power-Supply would be 4- Li-Ion Cells in series,
which would make a Plus and Minus ~7.5-Volt Supply, (~15-Volts).
Batteries are inherently "quiet",
which means less Noise issues to deal with,
plus, they're portable.
.
.
.
Thank you very much sir,
I have learned many things from you ..

I have understood what you want to tell,
so decided to make the only mixer for "Clip-On" "Lapel", or "Lavalier" type Microphone only.
, So then what will be the design (how to give power supply them)
the output will be attached with a computer 3.5mm input jack..

Anyone in this forum is also welcome for answering...

#### iamrdb

Joined Jul 31, 2021
6
I want to make a simple clear Microphone circuit. I will use this circuit for use on mobile or computer.
1) The electret mic that I want to use :

2) I want to provide a 5v power supply ( from mobile charger )

#### LowQCab

Joined Nov 6, 2012
1,096
The first point is .....
I can not recommend that You purchase a Microphone from China,
( Banggood, Aliexpress, Ebay, Walmart.com, etc., etc., etc. ),
because You really have no idea of what You are going to get.
It will be super-cheap, but the sellers have NO IDEA of what it is that they are selling,
how it works, what the specifications are, how the Jack is Wired,
how much Voltage it requires, absolutely NO Information at all.

There are probably ~10 or more Jack configurations,
will save You a lot of profanities and throwing of Tools.

The Microphone that I found seems to be reasonably priced,
and has a "no-brainer" Mono-Jack, and specified Power requirements.
( it seems that their Site is temporarily broken, the Link might not work )
https://www.markertek.com/product/ex-503/azden-ex-503-omni-directional-lavalier-microphone

I've just about finished a Schematic for a Mixer specifically designed for this Model of Microphone,
sit tight .............
.
.
.

Last edited:

#### iamrdb

Joined Jul 31, 2021
6
The first point is .....
I can not recommend that You purchase a Microphone from China,
( Banggood, Aliexpress, Ebay, Walmart.com, etc., etc., etc. ),
because You really have no idea of what You are going to get.
It will be super-cheap, but the sellers have NO IDEA of what it is that they are selling,
how it works, what the specifications are, how the Jack is Wired,
how much Voltage it requires, absolutely NO Information at all.

There are probably ~10 or more Jack configurations,
will save You a lot of profanities and throwing of Tools.

The Microphone that I found seems to be reasonably priced,
and has a "no-brainer" Mono-Jack, and specified Power requirements.
( it seems that their Site is temporarily broken, the Link might not work )
https://www.markertek.com/product/ex-503/azden-ex-503-omni-directional-lavalier-microphone

I've just about finished a Schematic for a Mixer specifically designed for this Model of Microphone,
sit tight .............
.
.
.
Thank you, sir, Thank you very much.. from you I have learnt so many things..
I will be grateful to you if you provide me with the diagram of "Schematic for a Mixer specifically designed for this Model of Microphone".

#### Ian0

Joined Aug 7, 2020
3,234
Always used to use Panasonic condenser mic inserts. Never gave any trouble.

#### Audioguru again

Joined Oct 21, 2019
3,514
The specs for the expensive mic has no details about its deviation (usually +/-2dB).
Its frequency response from 30Hz to 18kHz might sound like a muffled and tinny telephone like this:

#### Attachments

• 9.7 KB Views: 9

#### Ian0

Joined Aug 7, 2020
3,234
A flat frequency response is an inherent characteristic of the condensor mic. The difference appears to be mainly in the quality of build - generally whether the JFET gate is welded to the element or whether it is just held in place by the can crimp.
I took one of these apart
https://www.behringer.com/product.html?modelCode=P0118
and found inside what looked suspiciously like a Panasonic condensor mic insert.

One thing to watch out for is that some of the parts designed for telephony have a bass roll-off that starts above 100Hz (to fit with the 300-3400Hz telephone bandwidth)

I've also had some success with MEMS microphones. They have a low-impedance output, and just need a 3.3V supply. They are generally excellent quality, but a bit noisy (-60dB) for professional use.

#### LowQCab

Joined Nov 6, 2012
1,096
Here's the Schematic for a Low-Voltage-Mic-Mixer designed to
provide Bias-Power to Electret-Condenser-Mics.
Dynamic-Mics will probably work too.
If perfect extremely-High-Frequency-Response is important to You,
then You will need Op-Amps that cost ~10-times as much,
but these cheapo-chips should do just fine.
All of the Resistors need to be "Metal-Film", 0.5% tolerance, 1/2-Watt rated,
to keep the background noise to a minimum.
All Capacitors, 1uf and smaller, are Ceramic, and at least 10%,
You get what You pay for.
.
.
.

Last edited:


text:
# Warmup

Algebra Level 2

If $\dfrac{25}{3-4i}=a+bi$, where $a$ and $b$ are real numbers and $i$ is the imaginary unit, find $a+b$.

×


text:
## College Algebra (11th Edition)

-14$q^{2}$ + 11q - 14
1. Apply distributive property. -3(4$q^{2}$ - 3q + 2) + 2(-$q^{2}$ + q - 4) = -12$q^{2}$ + 9q - 6 - 2$q^{2}$ + 2q - 8 2. Group like terms together. -12$q^{2}$ - 2$q^{2}$ + 9q + 2q - 6 - 8 3. Add like terms. -14$q^{2}$ + 11q - 14


text:
# What are the different types of “averages” and when to use each one?

So, the concept of an average truly is somewhat abstract. Most statisticians define it as a "measure of central tendency." Others say it is the "center of gravity" for a set of numbers.

I personally prefer a slightly more concrete explanation: A statistic that describes the "typical", or better yet, "representative" value of a data set. We humans get to decide what "representative" actually means. Is it the most common number? The number that falls "in the middle" of a set of numbers? Etc.

I am going to list a few types of averages and am wondering if someone could provide a data set where that particular average is the best choice for describing a "typical" or "representative" value for that data set.

## Types of averages:

• Arithmetic Mean: The number that you could use in place of each of the values of a data set, and still have the same sum. Formula: $$\overline{X}=\frac1N\sum\limits_{i=1}^{N} X_i$$

• Mode: The most common value in a data set. No formula that I know of.

• Median: The literal middle number of a data set where the values are listed in ascending order. No formula that I know of.

• Root Mean Square: Don't really know how to describe this average in a physical sense. Maybe the average that gives larger numbers in the data set more "weight" or "significance?" Formula: $$X_{rms}=\sqrt{\frac1N\sum\limits_{i=1}^{N} X_i^2}$$

• Mean Root Square: I just made this one up, but it seems to work well when I applied it to some random data sets. It seems to do the opposite of the RMS and gives smaller numbers in the data set more "weight" and "significance." Formula: $$X_{mrs}=\frac1N\sqrt{\sum\limits_{i=1}^{N} X_i^2}$$ EDIT: Turns out this should not be considered an average because it fails to describe a data set that consists of only one number, unlike all the other averages.

• Geometric mean: The number that you could use in place of each of the values of a data set, and still have the same product. Formula: $$GM=\sqrt[N]{\prod\limits_{i=1}^{N} X_i}$$

Feel free to add in any other popular or useful types of averages and when to use them!

• The "mean root square" of the dataset 1,1,1,1 is 1/2, so it is not an average in any sense. You should try the "square mean root" instead. – Rahul Apr 13 '17 at 18:53
• @Rahul Hmm, but I could make a similar argument for other averages as well. In this data set, 1, 1, 20, 21, 22, 23, 24, 25, the mode is 1, but certainly fails to describe the "representative" value and thus also not an average in any sense. – Nova Apr 13 '17 at 19:17
• @Rahul I don't think there is any one average that works universally. Maybe my MRS idea fails to work for some data sets, but is effective in many others. – Nova Apr 13 '17 at 19:19
• @Rahul Unless there is some mathematical rule about averages that I don't know about. For example, for any data set, an average must always be a number that is greater than or equal to the lower boundary and lesser than or equal to the highest boundary. If this is so, then yes, MRS would fail to be an average. – Nova Apr 13 '17 at 19:19
• There is no complete axiomatization that covers all the existing averaging methods as far as I know, but certainly all averages I know of have the property that if all values in the dataset are identical then the average is the same as that value. Anyway, your mean root square is just the root mean square divided by $\sqrt N$. – Rahul Apr 13 '17 at 19:43


text:
# Non-Hermitian Quantum Quenches in Holography

### Submission summary

 As Contributors: Karl Landsteiner · Sergio Morales-Tejera Arxiv Link: https://arxiv.org/abs/2203.02524v1 (pdf) Date submitted: 2022-03-17 10:19 Submitted by: Morales-Tejera, Sergio Submitted to: SciPost Physics Academic field: Physics Specialties: High-Energy Physics - Theory

### Abstract

The notion of non-Hermitian PT symmetric quantum theory has recently been generalized to the gauge/gravity duality. We study the evolution of such non-Hermitian holographic field theories when the couplings are varied with time with particular emphasis on the question non-unitary time vs. unitary time evolution. We show that a non-unitary time evolution in the dual quantum theory corresponds to a violation of the Null Energy Condition (NEC) in the bulk of the asymptotically AdS spacetime. We find that upon varying the non-Hermitian coupling the horizon of a bulk AdS black hole shrinks. On the other hand varying the Hermitian coupling in the presence of a constant non-Hermitian coupling still violates the NEC but results in a growing horizon. We also show that by introducing a non-Hermitian gauge field the time evolution can be made unitary, e.g. the NEC in the bulk is obeyed, and an exactly equivalent purely Hermitian description can be given.

###### Current status:
Editor-in-charge assigned

### Submission & Refereeing History

Submission 2203.02524v1 on 17 March 2022

## Reports on this Submission

### Report

This paper explores the idea of non-Hermitian holography. This is inspired by the observation that it is possible to have a non-Hermitian Hamiltonian with real eigenvalues, provided it has PT symmetry. Such theories carry the interpretation of an open quantum system, and in the PT-symmetric phase there is a steady balance between inflow and outflow.

The authors take a holographic superconductor model, and fix boundary conditions to engineer non-Hermitian field theory couplings. They then consider quench protocols involving the non-Hermitian coupling, solving the 1+1 bulk equations in ingoing coordinates.

I think this is a valuable contribution to a novel and interesting research direction (extending [32]) and this paper should be published in SciPost. But I think there is one aspect that should be clarified first, especially given the open quantum system interpretation:

Apparent and event horizons will eventually be the same once the system returns to equilibrium at late times, after the quench is over. Normally, if the null curvature condition is obeyed and you have an apparent horizon, then the event horizon has to be outside it or coinciding with it [see e.g. Hawking and Ellis]. Figure 3 shows the apparent horizon shrinking. Given the exotic bulk matter it is not at all clear whether the event horizon also shrinks, since we don't know for sure that it has to be outside the apparent horizon. So my question is - does the event horizon shrink? and, does it lie inside the apparent horizon for some time? Integrating null geodesics backwards through their computed solution to find the event horizon would answer this.

• validity: -
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### Report

In [32] one of the authors used gauge/gravity duality to study PT symmetric quantum field theory. The current manuscript extends this work by considering time-dependent couplings. Interesting relations are found between non-unitary evolution in holographic quantum field theory and violation of the Null Energy Condition in the dual bulk theory, and various types of time-dependences are explored numerically. This is a new line of research, of which it is hard to predict where exactly it will lead, but I find it interesting.

I would like to request, however, that the authors explain more clearly the relation between PT symmetry in their holographic model and in previously studied PT symmetric quantum field theories. I find the paragraph starting at the bottom of page 10 (starting with “Let us also note how the PT symmetry acts in this case”) not clear enough. Hopefully the following specific questions will help convey what confuses me:

1) About the notation: Is there a reason why straight P and T are used, but the combination seems to be denoted as curly PT?
2) It is stated that the authors take the point of view that the PT symmetry only acts on the boundary conditions of the bulk theory, i.e., on the couplings of the dual field theory. Does this mean that PT does not act on the fields of the dual field theory (in contrast to what one might have expected of the parity and time reversal operators)?
3) For comparison, in arXiv:1201.1244, the $i\phi^3$ theory is studied, where $\phi$ is assumed to be a pseudoscalar. It is stated that this interaction term is invariant under PT because P changes the sign of $\phi$ and T changes the sign of $i$. How is this action of P and T related to the point of view in the current manuscript?
4) In the manuscript, it is stated that the imaginary part of a complex scalar is a pseudoscalar and thus parity and time reversal odd. Could the authors explain why the imaginary part of a complex scalar is automatically a pseudoscalar? And could they clarify how the sign change of this pseudoscalar under T relates to the previous point 3) and to the discussion in [32], where T does not appear to change the sign of the imaginary part of the scalar? Perhaps relatedly, could the authors explain in more detail why the complexified boundary conditions are PT symmetric?
5) When describing the actions of P and T, the arguments of the scalar field are not displayed. I would have expected that T maps the boundary condition of a scalar field at a certain time to the boundary condition of the field at the reflected time. If the boundary conditions are allowed to display arbitrary time-dependence, how can they be PT symmetric? Is there a hidden assumption that boundary values at a certain time are the same as those at the reflected time?

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text:
## Seneta-Heyde norming in the branching random walk.(English)Zbl 0873.60062

Summary: In the discrete-time supercritical branching random walk, there is a Kesten-Stigum type result for the martingales formed by the Laplace transform of the $$n$$th generation positions. Roughly, this says that for suitable values of the argument of the Laplace transform the martingales converge in mean provided an “$$X\log X$$” condition holds. Here it is established that when this moment condition fails, so that the martingale converges to zero, it is possible to find a (Seneta-Heyde) renormalization of the martingale that converges (in probability) to a finite nonzero limit when the process survives. As part of the proof, a Seneta-Heyde renormalization of the general (Crump-Mode-Jagers) branching process is obtained; in this case the convergence holds almost surely. The results rely heavily on a detailed study of the functional equation that the Laplace transform of the limit must satisfy.

### MSC:

 60J80 Branching processes (Galton-Watson, birth-and-death, etc.) 60G50 Sums of independent random variables; random walks
Full Text:

### References:

 [1] ASMUSSEN, S. and HERING, H. 1983. Branching Processes. Birkhauser, Boston. \" · Zbl 0516.60095 [2] BIGGINS, J. D. 1977a. Martingale convergence in the branching random walk. J. Appl. Probab. 14 25 37. · Zbl 0997.60093 [3] BIGGINS, J. D. 1977b. Chernoff’s Theorem in the branching random walk. J. Appl. Probab. 14 630 636. · Zbl 0997.60093 [4] BIGGINS, J. D. 1992. Uniform convergence of martingales in the branching random walk. Ann. Probab. 20 137 151. · Zbl 0748.60080 [5] BIGGINS, J. D. and KYPRIANOU, A. E. 1996. Branching random walk: Seneta Heyde norming. In Z Trees: Proceedings of a Workshop, Versailles June 14 16, 1995 B. Chauvin, S. Cohen. and A. Rouault, eds.. Birkhauser, Basel. \" · Zbl 0864.60070 [6] CHAUVIN, B. 1988. Arbres et Processus de Branchement. Ph.D. thesis, Univ. Paris 6. [7] CHAUVIN, B. 1991. Product martingales and stopping lines for branching Brownian motion. Ann. Probab. 19 1195 1205. · Zbl 0738.60079 [8] CHAUVIN, B. and ROUAULT, A. 1996. Boltzmann Gibbs weights in the branching random walk.In Classical and Modern Branching Processes K. B. Athreya and P. Jagers, eds. 84 41 50. Springer, New York. Z. Z. · Zbl 0866.60074 [9] COHN, H. 1985. A martingale approach to supercritical CMJ branching processes. Ann. Probab. 13 1179 1191. · Zbl 0587.60086 [10] DURRETT, R. and LIGGETT, M. 1983. Fixed points of the smoothing transform.Wahrsch. Verw. Gebiete 64 275 301. Z. · Zbl 0506.60097 [11] FELLER, W. 1971. An Introduction to Probability Theory and Its Applications, 2nd ed. Wiley, New York. · Zbl 0219.60003 [12] HEYDE, C. C. 1970. Extension of a result of Seneta for the supercritical branching process. Ann. Math. Statist. 41 739 742. · Zbl 0195.19201 [13] JAGERS, P. 1975. Branching Processes with Biological Applications. Wiley, New York. · Zbl 0356.60039 [14] JAGERS, P. 1989. General branching processes as Markov fields. Stochastic Process. Appl. 32 183 212. · Zbl 0678.92009 [15] KAHANE, J. P. and PEYRIERE, J. 1976. Sur certaines martingales de Benoit Mandelbrot. Adv. Math. 22 131 145. · Zbl 0349.60051 [16] KINGMAN, J. F. C. 1975. The first birth problem for an age-dependent branching process. Ann. Probab. 3 790 801. · Zbl 0325.60079 [17] KURTZ, T. G. 1972. Inequalities for the law of large numbers. Ann. Math. Statist. 43 1874 1883. · Zbl 0251.60019 [18] LIU, Q. 1996. Fixed points of a generalized smoothing transformation and applications to branching processes. Unpublished manuscript. [19] LIU, Q. 1997. Sur une equation fonctionelle et ses applications: une extension du theoreme de Kesten Stigum concernant des processus de branchement. Adv. in Appl. Probab. 29. JSTOR: · Zbl 0901.60055 [20] LYONS, R. 1996. A simple path to Biggins’ martingale convergence. In Classical and ModernBranching Processes K. B. Athreya and P. Jagers, eds. 84 217 222. Springer, New York. Z. Z. · Zbl 0897.60086 [21] NERMAN, O. 1981. On the convergence of supercritical general C-M-J branching process.Wahrsch. Verw. Gebiete 57 365 395. Z. · Zbl 0451.60078 [22] NEVEU, J. 1988. Multiplicative martingales for spatial branching processes. In Seminar onStochastic Processes, 1987 E. C \?inlar, K. L. Chung and R. K. Getoor, eds. Prog. Probab. Statist. 15 223 241. Birkhauser, Boston. \" Z. · Zbl 0652.60089 [23] PAKES, A. G. 1992. On characterizations via mixed sums. Austral. J. Statist. 34 323 339. · Zbl 0759.62006 [24] SENETA, E. 1968. On recent theorems concerning the supercritical Galton Watson process. Ann. Math. Statist. 39 2098 2102. · Zbl 0176.47603 [25] WAYMIRE, E. C. and WILLIAMS, S. C. 1994. A general decomposition theory for random cascades.Bull. Amer. Math. Soc. N. S. 31 216 222. Z. · Zbl 0805.60045 [26] WAYMIRE, E. C. and WILLIAMS, S. C. 1995. Multiplicative cascades: dimension spectra and dependence. J. Fourier Analysis and Applications. Special issue in honour of J.-P. Kahane 589 609. · Zbl 0889.60050 [27] WAYMIRE, E. C. and WILLIAMS, S. C. 1996. A cascade decomposition theory with applications to Markov and exchangeable cascades. Trans. Amer. Math. Soc. 384 585 632. JSTOR: · Zbl 0857.60028 [28] SHEFFIELD, S3 7RH UNITED KINGDOM E-MAIL: j.biggins@sheffield.ac.uk
This reference list is based on information provided by the publisher or from digital mathematics libraries. Its items are heuristically matched to zbMATH identifiers and may contain data conversion errors. It attempts to reflect the references listed in the original paper as accurately as possible without claiming the completeness or perfect precision of the matching.


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# A book is at rest on top of a table. Which of the following is correct?

$\begin{array}{1 1} (a)\;\text{There is no force acting on the book.} \\ (b)\; \text{The book has no inertia.} \\ (c)\; \text{There is no force acting on the table.} \\ (d)\; \text{The book is in equilibrium.} \end{array}$


text:
시간 제한 메모리 제한 제출 정답 맞은 사람 정답 비율
1 초 128 MB 0 0 0 0.000%

## 문제

A typical bus timetable has a column of stops down the left hand side, followed by a series of columns specifying a particular service and labelled with the number of a bus route. Each entry in the table, i.e. each intersection of the row for a given stop and a column for a given service, will be either blank or contain the time that that service is scheduled to leave that stop.

As you can imagine, producing these timetables by hand is very difficult and error prone, so this is where you come in. Write a program to produce a timetable, given details of the various routes and services.

## 입력

Input will consist of a number of scenarios. Each scenario will start with the title of the scenario, followed by a number of lines, one for each route in the scenario. The sequence of scenarios will be terminated by a line consisting of a single ‘#’.

The line for a route will start with the time that the first service for that route leaves the depot (hours and minutes) followed by the interval between services (minutes). This will be followed by a series of pairs of integers representing travel times and bus stops. The list of routes will be terminated by a line containing two zeroes (0 0) and will never contain details of more than 10 routes. Note that routes are numbered implicitly, starting from 1, bus stops are also numbered from 1 and are always visited in order (apart from the return to the depot), there will never be more than 99 stops, and that the depot is effectively bus stop 0 (thus the last bus stop number in the list will always be 0). Note that no buses leave before 6:00 am and all services terminate (i.e. are back in the depot) by midnight, thus you should not generate a service that violates these constraints.

## 출력

Output will consist of one timetable per scenario. Each timetable will start with the name of the scenario on a line by itself, followed by a heading line detailing the services (sorted in order of departure time from the depot, see example) followed by as many lines as there are bus stops mentioned in the input. Each line starts with the number of the stop (two columns) followed by an entry for each service. Each entry is 6 columns wide and starts with a ‘|’ followed either by 5 spaces (if that service does not stop there) or a departure time in the form hh:mm, using a 24 hour clock (i.e., including leading zeroes). The line is terminated by a ‘|’. Note that times increase monotonically downwards, but not necessarily across. Leave a blank line between scenarios.

## 예제 입력 1

MadeUpAsIWentAlong
7 0 240 20 1 10 2 20 3 10 0
9 0 240 20 1 10 2 20 3 10 0
0 0
#

## 예제 출력 1

MadeUpAsIWentAlong
|    1|    2|    1|    2|    1|    2|    1|    2|    1|
1|07:20|09:20|11:20|13:20|15:20|17:20|19:20|21:20|23:20|
2|07:30|09:30|11:30|13:30|15:30|17:30|19:30|21:30|23:30|
3|07:50|09:50|11:50|13:50|15:50|17:50|19:50|21:50|23:50|


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# cirq.MeasurementGate¶

class cirq.MeasurementGate(num_qubits: Optional[int] = None, key: str = '', invert_mask: Tuple[bool, …] = (), qid_shape: Tuple[int, …] = None)[source]

A gate that measures qubits in the computational basis.

The measurement gate contains a key that is used to identify results
of measurements.
__init__(num_qubits: Optional[int] = None, key: str = '', invert_mask: Tuple[bool, …] = (), qid_shape: Tuple[int, …] = None) → None[source]
Parameters
• num_qubits – The number of qubits to act upon.

• key – The string key of the measurement.

• invert_mask – A list of values indicating whether the corresponding qubits should be flipped. The list’s length must not be longer than the number of qubits, but it is permitted to be shorter. Qubits with indices past the end of the mask are not flipped.

• qid_shape – Specifies the dimension of each qid the measurement applies to. The default is 2 for every qubit.

Raises

ValueError – If the length of invert_mask is greater than num_qubits. or if the length of qid_shape doesn’t equal num_qubits.

Methods

 controlled([num_controls, control_values, …]) Returns a controlled version of this gate. If no arguments are Returns the invert mask for all qubits. The number of qubits this gate acts on. on(*qubits) Returns an application of this gate to the given qubits. validate_args(qubits) Checks if this gate can be applied to the given qubits. with_bits_flipped(*bit_positions) Toggles whether or not the measurement inverts various outputs. wrap_in_linear_combination([coefficient])


text:
12:37 AM
@user202729 latest weird result: tested my last layout and @isaacg's last layout with three exit types, my original exit, @isaacg's tricky exit, and my new trident exit. my layout works best with trident exit, other two exits perform equally worse. @isaacg's layout works equally well with trident exit and tricky exit, my original exit proving so bad that adding more 2-way branches does better.

1:07 AM
0

Rage Against the Dying of the Light code-golfkolmogorov-complexity Introduction "Do not go gentle into that good night" is the title of a poem by 20th century English poet Dylan Thomas. If you've heard it before it was probably because you watched Interstellar, where it was quoted multiple times....

1:24 AM
Today is the 365th day in a row I've visited CGCC
No, I'm not addicted, I just like the site

3 hours later…
4:34 AM
1

Given two base ten integers m and n, you will need to make the last n digits of m its first digits. Tests Num,n => Output 123,1 => 312 123,2 => 231 123,3 => 123 123,4 => 312 1,637 => 1 10,1 => 1 (01=>1) 100,2 => 1 (Final result was 001, but the leading zeros were removed) 10,2 => 10 110,2 => 10...

5 hours later…
9:40 AM
0

Combinatorial Decomposition code-golf combinatorics base-conversion Any nonnegative integer \$m\$, given arbitrary nonnegative integer \$r\$, can be written as a unique series of combinations such that $$m=\sum\limits_{i=1}^{r}\begin{pmatrix}C_i\\i\end{pmatrix}$$ provided \$C\$ is strictly increa...

2 hours later…
11:10 AM
@Neil Equal as in having the exact same score?

@user202729 well I'm assuming the small difference is due to floating-point inaccuracies

I think scipy is good. The error is in the order of ~1e-14 (double precision) of the result?

11:37 AM
@Neil Also do you use anything (other than pure Python code) to manipulate the board?

the thing is, I only compared the results to the nearest integer, which is 8 digits, and I can't remember what I did with the original results, or whether I kept enough of the scripts to reproduce them

@Neil "Wall finder"?

but as a comparison, I think that moving the start squares to be horizontal instead of vertical made a difference of <1e-10
@user202729 "Wall finder" just goes through every horizontal and vertical wall, recalculates the score with them added, then picks the highest score, rinse and repeat. It likes width 2 corridors.

@Neil or removed?

but, it's what I used to find my trident layout (I based the idea on my "fewer dead ends" applied to width 3 corridors, and it suggested adding the tridents)

11:43 AM
I think it would be better to move a wall by one unit (perpendicular to the wall). Both adding and removing a wall is not a good idea.

@user202729 no, I didn't try that

@Neil Did you write a faster judge program? It rating through 10^4 options would take forever.

yeah, it's not fast. it took a few hours. I did apply multiprocessing to it in one of my scripts, but then I couldn't work out how to use my "this wall blocks the way to the exit, don't try it again" optimisation

12:18 PM
Decide to implement from_compact_ascii to edit the maze manually.
def as_compact_ascii(self):
self._fix_maze()
vertex="·"
lines = [vertex + ("-"+vertex)*self.width]
for y in range(self.height):
lines.append("|" + "".join("{}{}".format("S" if (x, y) in self.starts else "E" if (x, y) in self.exits else " ",
" |"[x == self.width - 1 or int(self.hwalls[x,y])])
for x in range(self.width)))
lines.append(vertex + "".join(("-" if y == self.height - 1 or self.vwalls[x,y] else " ")+vertex
for x in range(self.width)))
return "\n".join(lines)
Can't find any way to improve that solution.

1 hour later…
1:44 PM
More idea: 90-degree turns?
I think there would be twice as many turns...

2 hours later…
4:08 PM
@user202729 instead of a width 3 corridor, I tried an arrangement whereby the route zigzagged a bit like a width 2 corridor concertinaed in on itself, however this also turned out to score the same (within <1e-10) as a regular width 3 corridor

(deleted)


text:
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# Smoking, oh its so much fun to quit.

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SVP
Joined: 30 Mar 2006
Posts: 1738
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Kudos [?]: 46 [0], given: 0

[#permalink]  15 Mar 2007, 20:24
rhyme wrote:
jaynayak wrote:
Agree completely with Rhyme...

I quit while back and started again few days ago... I know i should not have.... but this time I am trying to retrain my mind to form new connections.... then I will quit again and retrain the brain again....

Nice way to keep the grey cells functioning.

A few days ago???? Why????

Didja visit whyquit.com and watch the palmolive bottle video?

No ..... it is a lame excuse.....

I still haven't been able to retrain my mind to do anything when I am utterly bored....
GMAT Club Legend
Affiliations: HHonors Diamond, BGS Honor Society
Joined: 05 Apr 2006
Posts: 5926
Schools: Chicago (Booth) - Class of 2009
GMAT 1: 730 Q45 V45
WE: Business Development (Consumer Products)
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Kudos [?]: 1710 [0], given: 7

[#permalink]  15 Mar 2007, 20:38
jaynayak wrote:
rhyme wrote:
jaynayak wrote:
Agree completely with Rhyme...

I quit while back and started again few days ago... I know i should not have.... but this time I am trying to retrain my mind to form new connections.... then I will quit again and retrain the brain again....

Nice way to keep the grey cells functioning.

A few days ago???? Why????

Didja visit whyquit.com and watch the palmolive bottle video?

No ..... it is a lame excuse.....

I still haven't been able to retrain my mind to do anything when I am utterly bored....

Its a lame excuse all right! But I do understand it. I can appreciate how it happens... If you ever need inspiration to quit, you know where to find it.
SVP
Joined: 30 Mar 2006
Posts: 1738
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Kudos [?]: 46 [0], given: 0

[#permalink]  15 Mar 2007, 20:44
thanks .....

No deadlines for me this time..... I just have to try retraining ....
GMAT Club Legend
Affiliations: HHonors Diamond, BGS Honor Society
Joined: 05 Apr 2006
Posts: 5926
Schools: Chicago (Booth) - Class of 2009
GMAT 1: 730 Q45 V45
WE: Business Development (Consumer Products)
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Kudos [?]: 1710 [0], given: 7

[#permalink]  15 Mar 2007, 20:48
jaynayak wrote:
thanks .....

No deadlines for me this time..... I just have to try retraining ....

If you do try again...

1. Use about.com forums.
2. Get a quit meter. I have a firefox extension called quitomzilla. Watching it tick up is a good motivator.
3. Tell your friends your quitting (the shame of failing if you dont will keep you motivated)
Current Student
Joined: 29 Jan 2005
Posts: 5242
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Kudos [?]: 180 [0], given: 0

[#permalink]  17 Mar 2007, 21:43
rhyme wrote:
jaynayak wrote:
thanks .....

No deadlines for me this time..... I just have to try retraining ....

If you do try again...

1. Use about.com forums.
2. Get a quit meter. I have a firefox extension called quitomzilla. Watching it tick up is a good motivator.
3. Tell your friends your quitting (the shame of failing if you dont will keep you motivated)

It also helps to be humiliated. I once saw a guy who was shopping with his kid suddenly get struck with a serious hacking attack. People around him started getting so concerned that one lady even called 911. Eventually his explosive coughing subsided, the guy apologized to the crowd which had gathered around him, admitted that he was a smoker, and pleaded to his crying kid that everything was going to be OK. I would be willing to bet that he quit then and there.
GMAT Club Legend
Affiliations: HHonors Diamond, BGS Honor Society
Joined: 05 Apr 2006
Posts: 5926
Schools: Chicago (Booth) - Class of 2009
GMAT 1: 730 Q45 V45
WE: Business Development (Consumer Products)
Followers: 272

Kudos [?]: 1710 [0], given: 7

[#permalink]  18 Mar 2007, 08:08
GMATT73 wrote:
rhyme wrote:
jaynayak wrote:
thanks .....

No deadlines for me this time..... I just have to try retraining ....

If you do try again...

1. Use about.com forums.
2. Get a quit meter. I have a firefox extension called quitomzilla. Watching it tick up is a good motivator.
3. Tell your friends your quitting (the shame of failing if you dont will keep you motivated)

It also helps to be humiliated. I once saw a guy who was shopping with his kid suddenly get struck with a serious hacking attack. People around him started getting so concerned that one lady even called 911. Eventually his explosive coughing subsided, the guy apologized to the crowd which had gathered around him, admitted that he was a smoker, and pleaded to his crying kid that everything was going to be OK. I would be willing to bet that he quit then and there.

Yea, thatd probably do it....

2 weeks, 5 days and 14 hours, saving 391.74 cigarettes and $148.86. GMAT Club Legend Affiliations: HHonors Diamond, BGS Honor Society Joined: 05 Apr 2006 Posts: 5926 Schools: Chicago (Booth) - Class of 2009 GMAT 1: 730 Q45 V45 WE: Business Development (Consumer Products) Followers: 272 Kudos [?]: 1710 [0], given: 7 [#permalink] 19 Mar 2007, 11:02 2 weeks, 6 days and 16 hours, saving 414.15 cigarettes and$157.37.

coming up on three weeks....
Manager
Joined: 04 Nov 2006
Posts: 158
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[#permalink]  19 Mar 2007, 11:27
rhyme wrote:
2 weeks, 6 days and 16 hours, saving 414.15 cigarettes and $157.37. coming up on three weeks.... Ok, so when we hang out in Chicago, absolutely no coffee shops or bars. We'll have to stick to walking around Humboldt Park...which actually might be just as bad for your health as smoking Seriously, though, keep kickin' ass on this thing. When you've kicked it completely, you can start training for the '07 marathon with me. GMAT Club Legend Affiliations: HHonors Diamond, BGS Honor Society Joined: 05 Apr 2006 Posts: 5926 Schools: Chicago (Booth) - Class of 2009 GMAT 1: 730 Q45 V45 WE: Business Development (Consumer Products) Followers: 272 Kudos [?]: 1710 [0], given: 7 [#permalink] 19 Mar 2007, 15:28 artshep wrote: rhyme wrote: 2 weeks, 6 days and 16 hours, saving 414.15 cigarettes and$157.37.

coming up on three weeks....

Ok, so when we hang out in Chicago, absolutely no coffee shops or bars. We'll have to stick to walking around Humboldt Park...which actually might be just as bad for your health as smoking

Seriously, though, keep kickin' ass on this thing. When you've kicked it completely, you can start training for the '07 marathon with me.

4 miles on the treadmill today
Manager
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[#permalink]  19 Mar 2007, 15:45
Are you guys really going to run any road races? I don't mess with marathons because I think I would go too hard and injure my knees.

Assuming I get in to business school, I plan on running some 5K's over the summer after I quit my job.
Manager
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[#permalink]  19 Mar 2007, 16:07
I'm definitely running several road races this year.

I'm running the Shamrock Shuffle 8k in Chicago this weekend. Also planning a half marathon in April or May. And finally the Chicago Marathon in October of this year.
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[#permalink]  19 Mar 2007, 16:29
I'm running the Shamrock Shuffle this weekend. Last year I wimped out because it was cold and windy and I felt sick.
Manager
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[#permalink]  19 Mar 2007, 16:31
Oh, nice! What starting corral are you in?
Manager
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[#permalink]  19 Mar 2007, 16:44
I put myself in Corral B. I'm not positive, but I think that I could have started in Corral A because I had a decent time in 2004. Which one are you in?

I've been getting back into shape since mid-January. My sense of pace is all off because I haven't been racing, but if I can run somewhere around 7:00-per-mile pace I'll be satisified. I've dropped close to 10 pounds of fat since January and have detected a noticable increase in my endurance.

If I train through the summer, I think I can lose another 10 pounds of fat and get my 5K pace down to around 6:00 per mile pace.
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[#permalink]  19 Mar 2007, 16:49
flapjack wrote:
I put myself in Corral B. I'm not positive, but I think that I could have started in Corral A because I had a decent time in 2004. Which one are you in?

I've been getting back into shape since mid-January. My sense of pace is all off because I haven't been racing, but if I can run somewhere around 7:00-per-mile pace I'll be satisified. I've dropped close to 10 pounds of fat since January and have detected a noticable increase in my endurance.

If I train through the summer, I think I can lose another 10 pounds of fat and get my 5K pace down to around 6:00 per mile pace.

This is inspiring.

How frequently and how long do you run? Also, any special needs as far as diet is concerned?

thanks
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[#permalink]  19 Mar 2007, 16:59
I've just been running on the treadmill after work at my gym. I haven't really even been running that much, but I do run, I run at a fairly quick tempo. I just do around 3.5-4 miles on the treadmill. I've been starting out at around 7:47 for the first mile and then progressively speed up until I'm too out of breath. Last Friday I ran 4.3 miles and did the last 1.3 miles at 6:40 pace. I run outside on the weekends, weather permitting.

I tend to get junk food when I get stressed out, but I've managed to cut back on it quite a bit during the week. I've also been eating a lot of chicken lately and really cut back on regular soda once a week.
Manager
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Posts: 158
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[#permalink]  19 Mar 2007, 16:59
flapjack wrote:
I put myself in Corral B. I'm not positive, but I think that I could have started in Corral A because I had a decent time in 2004. Which one are you in?

I've been getting back into shape since mid-January. My sense of pace is all off because I haven't been racing, but if I can run somewhere around 7:00-per-mile pace I'll be satisified. I've dropped close to 10 pounds of fat since January and have detected a noticable increase in my endurance.

If I train through the summer, I think I can lose another 10 pounds of fat and get my 5K pace down to around 6:00 per mile pace.

Looks like you and I will be neck-and-neck in this race. I'm also in corral B and hoping to run this one under 35 minutes. I'll be the short-ish, meditteranean-looking guy with the soccer legs.

Best of luck. How about running the marathon in October?
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[#permalink]  19 Mar 2007, 17:09
Good luck with the race. I'm not sure if I can maintain that pace for an 8K right now, although 35 minutes is my goal.

I'll probably never run a marathon. I prefer 5-10K races. What's your marathon pace?
GMAT Club Legend
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[#permalink]  22 Mar 2007, 06:38
GMAT Club Legend
Affiliations: HHonors Diamond, BGS Honor Society
Joined: 05 Apr 2006
Posts: 5926
Schools: Chicago (Booth) - Class of 2009
GMAT 1: 730 Q45 V45
WE: Business Development (Consumer Products)
Followers: 272

Kudos [?]: 1710 [0], given: 7

[#permalink]  22 Mar 2007, 06:51
3 weeks, 2 days and 12 hours, saving 470.66 cigarettes and \$178.85.

Almost at 500 smokes...

Christ I smoked a lot.
[#permalink] 22 Mar 2007, 06:51

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# Question #9defc

May 6, 2016

see below

#### Explanation:

$\frac{13}{2}$= Finite decimal
$\frac{11}{3}$= Repeating decimal
$\frac{3}{5}$= Finite decimal
$\frac{15}{6}$= Finite decimal
$\frac{17}{7}$= Repeating decimal
$\frac{15}{8}$= Finite decimal

Every fraction is a rational number, so it cannot be an infinite decimal. Infinite decimal represent irrational numbers like $\sqrt{2}$

To check if a fraction is a finite or periodic (repeating) decimal you have to:

• simplify the fraction

• check the prime factorization of its denominator.

If the factorization consists only of $2$ and $5$ the fraction can be written as a finite decimal, else the fraction can be only written as a repeating (periodic) decimal.


text:
Corpus ID: 209531858

# Asymptotic convergence rate of the longest run in an inflating Bernoulli net.

@article{Ni2019AsymptoticCR,
title={Asymptotic convergence rate of the longest run in an inflating Bernoulli net.},
author={Kai Ni and Shanshan Cao and Xiaoming Huo},
journal={arXiv: Applications},
year={2019}
}
• Published 31 December 2019
• Mathematics, Engineering
• arXiv: Applications
In image detection, one problem is to test whether the set, though mostly consisting of uniformly scattered points, also contains a small fraction of points sampled from some (a priori unknown) curve, for example, a curve with $C^{\alpha}$-norm bounded by $\beta$. One approach is to analyze the data by counting membership in multiscale multianisotropic strips, which involves an algorithm that delves into the length of the path connecting many consecutive "significant" nodes. In this paper, we… Expand

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text:
# Quotient Rings of Polynomials

Let $$R = \mathbb{C}[x,y]$$. Then $$R/Rx$$ is isomorphic to $$\mathbb{C}[y]$$.

My Proof

$$R = ax+by+c , a,b,c \in \mathbb{C}$$ and $$Rx = (ax+by+c)x , a,b,c \in \mathbb{C}$$

So, $$R/(R\cdot x) = (ax+by+c) + (a'x+b'y+c')x, a,b,c a',b',c' \in \mathbb{C}$$ $$= by+c + (a'x+b'y+(c'+a))x, a,b,c a',b',c' \in \mathbb{C}$$ So the set of cosets of $$R/(R\cdot x)$$ is clearly isomorphic to $$\mathbb{C}[y]$$.

This argument feels incredible handwavy. Is there a more rigorous way to prove this?

(I know in some cases defining an appropriate ring homomorphism and finding the kernel gives us the isomorphism by the first isomorphism theorem, but I couldn't find a homomorphism that worked.)

• I'd say $R=\mathbb C[x,y]=c+ax+by+dx^2+exy+fy^2+gx^3+hx^2y+ixy^2+jy^3+...$ – J. W. Tanner Nov 24 '19 at 15:37
• When you typed $r$, did you mean $R$? – J. W. Tanner Nov 24 '19 at 15:38
• But still $R \cdot x$ has no terms with just $y$ and no constant terms correct? So when we mod out $R \cdot x$, we have two cosets: identity coset, and one with all multiples of y @J.W.Tanner – Jess Nov 24 '19 at 15:59
• correct; $Rx=cx+ax^2+byx+dx^3+..$ – J. W. Tanner Nov 24 '19 at 16:02
• Thanks! Is there an approach that doesn't use the coset descriptions? or is this the most straightforward approach? – Jess Nov 24 '19 at 16:03

Hint. Can you prove that \begin{align*} \Phi:\mathbf{C}[X,Y] &\longrightarrow \mathbf{C}[Y] \\ f(X,Y) &\longmapsto f(0,Y) \end{align*} is a surjective ring homomorphism? Its kernel is exactly $$(X)\subset \mathbf{C}[X,Y]$$ (why?). Now you are ready to use the first isomorphism theorem.
• But don't I need the kernel to be ($X \cdot \mathbb{C}[X,Y]$)? – Jess Nov 24 '19 at 16:23
• This is just notation. We can denote the ideal by $(X)$ and $(X)\cdot \mathbf{C}[X,Y]$. Both mean the same thing: all polynomials in $X,Y$ with coefficients in $\mathbf{C}$ that are divisible by $X$. – rae306 Nov 24 '19 at 16:24