Assume $K/F$ be a field extension and $A,B \in M_n(F)$ . If $A,B$ be conjugate in $GL_n(K)$, is it true that $A,B$ are conjugate in $GL_n(F)$? Assume $K/F$  be a field extension and $A,B \in M_n(F)$ and $P\in GL_n(K)$ such that $PAP^{-1}=B$. Can we find $C\in GL_n(F)$ such that $CAC^{-1}=B$?
Similar matrices and field extensions Given a field $F$ and a subfield $K$ of $F$. Let $A$, $B$ be $n\times n$ matrices such that all the entries of $A$ and $B$ are in $K$. Is it true that if $A$ is similar to $B$ in $F^{n\times n}$ then they are similar in $K^{n\times n}$?   Any help ... thanks!
Python: Invalid Token WOL was working great on Bionic until yesterday's kernel update. How to diagnose/recover it?  Edit: if set to boot from 4.15.0-23 kernel it works. If set to boot from 4.15.0-24 it does not.  Edit2: WoL can be enabled with   sudo ethtool -s [card] wol g   but it isn't persistent. Searching for how to set it every boot.  Edit3: Per a comment by Kai-Heng Feng on this  this was an advertent change! (and therefore not a bug)  This is because the fix of LP: #1752772 has one commit [1] that disables WoL by default. Set WoL explicitly should solve your issue.  [1] https://github.com/torvalds/linux/commit/7edf6d314cd061e1d0a1b7bc0b511d64322c3f72 Self-promotion in chat We know from the  that it is accepted only in a limited way in answers and frowned upon if found to be spammy. We know from  that it can be deleted at any time from comments if the comment is not relevant or spammy.  But what about the chat? This leaves chat to be the only legitimate place to promote products or services that the user is affiliated to (albeit in an ad-like way).  What is your opinion? Find the expected value of $\frac{1}{X+1}$ where $X$ is binomial The problem:  X is a binomial random variable, find $E[\frac{1}{X+1}]$ n and p are not given  PDF for a binomial distribution is $\binom{n}{k}p^k(1-p)^{n-k}$  Expected value is $\sum{x_ip(x_i)}$  But this is where I get stuck, I'm really rusty on my statistics and I'm not sure exactly how to structure it in the next step? I think I want to get the form of the following out of the summation  $\sum _{k=0}^{n} \binom{n}{k}p^k(1-p)^{n-k} = (p + 1 - p)^n = 1$  But I'm not sure if it should look like  $\sum \frac{1}{xp(x)+1} $  and if it should where to go from here? Is There Any Way to get the template Name By full URL for example  If the full url is  www.example.com/hello-world   I need a function that return the template name (page.php)  I know that WordPress matches every url with regular expression to determine the query and decide which template to include.  That's exactly what I need, a built in or (custom made) function that takes the URL and returns back the corresponding template Sums in math mode: how to display index under the sigma sign? I have a fraction with sums above and under the line. How can I convince LaTeX to write the indices of the sums under the sigma instead of next to it?  \begin{displaymath}   \frac{\sum_{s \in S} s^2}{\sum_{p \in P} p^2} \end{displaymath} In bash, read after a pipe is not setting values With ksh I'm using read as a convenient way to separate values: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a  2 1 $  But it fails in Bash: $ echo 1 2 3 4 5 | read a b dump $ echo $b $a     $  I didn't find a reason in the man page why it fails, any idea? I would like to be able to change the default CSS used by chrome, such as removing the underlines for links, etc. However, I cannot find the default CSS file used by Chrome. Does anyone know where it is? What regulations should a European driver know when driving in the US? There are the obvious ones. The US has the keep-your-lane system, where as in Europe you are expected to keep to the right (left for UK) as long as possible.  On my latest travel to the US, I was confronted with the possibility to go through a red light if you turn right, unless it is explicitly not allowed.  What should a european driver know when driving in the US? What are the do's and don'ts compared to driving in Europe. Shell Script to move folders containing a specific word I'm searching for an simple shell script to mv all folders in /var/www/uploads/ that containing Math or Physics in the name to /mnt/Backup/. Is "this Monday" or "next Monday" the correct way to refer to the very next Monday in the future? Possible Duplicate:          When I refer to the very next Monday that will occur in the future, I say "next Monday". Some colleagues refer to it as "this Monday", with "next Monday" meaning the second Monday which will occur in the future (I would refer to that as "Monday week", "this Monday" to me would mean the most recent Monday in the past).  Are these both acceptable usages, or is one more correct than the other? I know that nobody likes duplicate questions, but I haven't found my answer on any of the other questions with this topic.  I built a computer with a  (made by Gigabyte).  It supposedly has 512 CUDA cores.  I followed  tutorial, (which enabled the Nvidia proprietary drivers) and was able to enable dual monitors and all the desktop graphics that are needed.  Unfortunetly, the GPU processing option still doesn't show up in Blender.  I've tried installing nvidia-cuda-toolkit, and that didn't make a difference.  I also tried to update my drivers from nvidia-346 to nvidia-349, and this had no apparent effect either.  What can I do to enable GPU rendering?  (I've tried both blender installed and just downloaded from the site). ShareLaTeX compilation flags Is it possible and if so how can you pass flags to the ShareLaTeX compiler which one would have passed as parameters to the LaTeX compiler?  I am using the minted package and need to pass the -shell-escape flag. I`m using Firefox Sync on a bunch of computers.   I would like to manage my account, by removing some computers. I can't find the place to do this, it should be on the Firefox Sync page, but the official page only has the privacy and download information. Let $G$ be a group, possibly a singleton. Let $M$ be a set, possibly empty. Let $\mu: M \times G \to M$ be a right group action. Let $1_G$ be the identity of $G$.  I understand 's second definition of faithful as follows:     $\mu$ is faithful if for each $g \in G$ such that $g \ne 1_G$, there exists $x \in M$ such that $\mu(x,g) \ne x$. $\tag{1}$   Later  says if $\mu$ is free and $M$ is a non-empty set, then $\mu$ is faithful.  Question: Given the idea that we can have $M$ as an empty set, I would like to clarify: Are these correct?   If $G$ is a singleton, then every action $\mu$ is faithful, whether or not $M$ is empty. If $G$ is not a singleton, but $M$ is empty, then every action $\mu$ is not faithful. Dealing with rust on a steel frame I can copy, move, create, and delete them. I can rename them using the REN command from a command prompt. I cannot rename folders through Windows Explorer anywhere on my machine, including on other drives.   When I try to do so, I receive an error titled "Rename Folder" that says "Can't find the specified file. Make sure you specify the correct path and file name." Then when I click Try Again or Cancel, I get another error titled "Rename" that says "The file or folder does not exist."  As far as I can tell, nothing else is wrong with my computer, but I'm pulling my hair out trying to fix this problem. I don't know for sure if superuser is the right place to ask this question, but feel free to redirect me.  Summary of Failed Attempts:   Booted into Safe Mode  Made a New User Account System Restore Point (two days ago, 9 days ago)  Deleting / Restoring / Modifying FolderDescriptions registry entries SFC /scannow  Removing windows update KB2984006  Scanned for viruses using Nod32  Scanned for malware using MalwareBytes   Details:  Tried rolling back to two different system restore points, both immediately before I observed the problem and one release prior to that.  Tried restoring FolderDescriptions registry entries as found here:   Booting in safe mode as suggested here:   SFC /scannow as suggested here:   Tried removing registry keys and windows update KB2984006 as suggested here:   Tried exporting folderdescriptions from other machine and importing as suggested here:   Compared my exported registry with other machine's exported registry for both:  HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Windows\CurrentVersion\Explorer\FolderDescriptions   My FolderDescriptions branch of the registry in both cases are binary equal to those exported from my wife's Windows 8.1 laptop which works fine. Why does no line appear when using Interpolate Line in ArcMap? How to ignore certain files in Git How to address a professor in person at US universities? At US universities, how should one address a professor while talking to him or her? In my home country, we usually address the professors as either "sir" or "madam" while talking about our queries in person.   What's the norm at US universities?