I am using Ubuntu 14.04 Trusty Tahr with kernel (3.13.29). A couple of days ago the login screen doesn’t allow me to login. In the error log there is a   gnome-session error Segmentation fault on LibX11.so.6.3 error 4   This line occurs every time I try to log in. I have a Lenovo W530 and I am using the nouveau display driver.  I installed the gnome desktop environment, so at login I can choose the environment I want but this hasn't solved the problem. I re-installed Ubuntu and this error cropped up when I did a distribution upgrade on the system.
My laptop was working perfectly yesterday, and now today I can't log in.  At first, I was only getting a black screen. However, after following instructions in some questions here on AskUbuntu, I first reinstalled lightdm, and then I had to change the ownership of the file ~/.Xauthority to be my user name. Now, I get the log in GUI screen.  However, once I enter my username, it flickers and then comes back to the login GUI. It does not matter if I use Gnome, Unity, or Gnome-Flashback.  I don't know why lightdm needed to be reconfigured, or how ~/.Xauthority got changed, but in any case, what is still standing in my way, preventing me from logging in?  Update: I have tried deleting the .Xauthority file, and the .profile files in my home directory. It has not changed anything.  Logging in as guest also fails to work.  The following commands did not work:  mv ~/.config ~/.config.BAK mv ~/.cache ~/.cache.BAK   Inside .xsession-errors in my home directory, it says:  Gdk-CRITICAL: gdk_x11_display_get_xdisplay: assertion 'GDK_IS_DISPLAY (display)' failed
How to make a blank page in Google Chrome at start-up? Is it possible to raise stats? I would like to show that   $$ \int_{0}^{1} \frac{x-1}{\ln(x)} \mathrm dx=\ln2 $$  What annoys me is that $ x-1 $ is the numerator so the geometric power series is useless.  Any idea? CSS bug with printing site pages (now with 100% more suggested fix included!) What is the difference between a class and a set? I know what a set is. I have no idea what a class is.   As best as I can make out, every set is also a class, but a class can be "larger" than any set (a so-called "proper class").  This obviously makes no sense whatsoever, since sets are of unlimited size. It's not like you get up to 25 elements and go "oh, hey, sets are limited to a maximum of 20 elements, so we'll have to call this 25-element thing something else".  Does anybody know what the actual difference between a set and a class is?  Several people have pointed out that you can write paradoxes which involve sets. I get that. But where do classes come into the picture? Using multiple wildcard parameters with arcpy.ListFeatureClasses I know there has to be a way to do this but I'm having trouble figuring out how to do so. I would like to create a list of feature classes to perform operations on however, I want to have the list contain feature classes which have 2 separate and distinct file name identifiers. The code would look something like:  FCS = arcpy.ListFeatureClasses("X_*" OR "*_Y")   I know OR is incorrect however, is there some way to do this without having to re write code to work with the second wildcard. Thanks for helping gout, i know there is a selection method in the Select By Attributes which allows for multiple wildcard use using the OR statement. Trying to dual boot Ubuntu 14.10 with Windows 10, last one not detected $g^k$ is a primitive element modulo $m$ iff $\gcd (k,\varphi(m))=1$ Is there a built-in checksum/hash utility on Windows 7? How can I decide between the medium sized intuos tablet or the small one? I am a high school student with an interest for drawing tablets for some hobby. I went to check on a store that sell Intuos, a sales representative (or something) of Wacom told me that most students buy the medium sized tablets. Even the staff said that since it is always bought the supplies of the medium size are a lot more than the small size.  I am on a tight budget (which is why I am buying the Intuos), and the small size seems small to me (when my hands are open, my thumb and my pinky would reach the sides). But then, why would Wacom sell the Manga variant in small? Is the staff just saying that so I would buy the more expensive one?  I have enough savings from my small allowance to buy the small size right now, should I wait for another month so that I can buy the medium size? Horn and spindle tori Galois Group of $\sqrt{2+\sqrt{2}}$ over $\mathbb{Q}$ So I want to show that $\mathbb{Q}(\sqrt{2+\sqrt{2}})$ is Galois over $\mathbb{Q}$ and determine its Galois group.   My thoughts are as follows:  Define $\alpha := \sqrt{2+\sqrt{2}}$. Then it is easily shown that $\alpha$ satisfies $\alpha^4-4\alpha^2+2=0$.  Define $f(x) := x^4-4x^2+2$. Then $f$ is irreducible over $\mathbb{Q}$ by Eisenstein with $p=2$.  So we have that $f$ is the irreducible polynomial for $\alpha$ over $\mathbb{Q}$.   Further $|\mathbb{Q}(\alpha):\mathbb{Q}|=4$.  For $\mathbb{Q}({\alpha})$ to be Galois, it must contain all roots of $f$.   Define $K=\mathbb{Q}(\alpha)$ for convenience.  Define $\alpha := \alpha_1$.  Since $f$ has only even powers, we know that $-\alpha := \alpha_2$ is a root, and therefore contained in $K$ since $K$ is a field.  We note that the other two roots are $\alpha_3=\sqrt{2-\sqrt{2}}$ and $\alpha_4=-\sqrt{2-\sqrt{2}}$.  So in order to show $K$ is Galois, it must be shown that $\alpha_3$ and $\alpha_4$ lie in $K$.  Now $\alpha_1^2=2+\sqrt2$ and so $\sqrt2 \in K$. Thus $-\sqrt2 \in K$ since $K$ is a field.  Can somebody explain why $\alpha_3$ and $\alpha_4$ lie in $K$?  Next we are to determine the Galois group of $K$.  Assuming $K$ is Galois, since it has degree $4$ over $\mathbb{Q}$ (shown earlier), we know that its Galois group has size $4$. There are only two groups of size $4$, namely $V_4$ and $C_4$, the Klein four group and the cyclic group of order $4$.  How do we determine which of these choice is in fact the Galois Group? Statistics  () In Q1 of 2012 - 0.0134 such comments per question (~1.33%) In Q2 of 2012 - 0.0167 such comments per question (~1.66%) In Q3 of 2012 - 0.0169 such comments per question (~1.68%) In Q4 of 2012 - 0.0193 such comments per question (~1.92%) In Q1 of 2013 - 0.0223 such comments per question (~2.22%)  The vast majority of these questions need serious help.  Unfortunately, there is a growing trend towards abuse Along with the good, comes some bad -- as usual in life. These comments are bad when  Posting &quot;what have you tried&quot; multiple times per question is severely obnoxious Posting &quot;what have you tried&quot; when the user has clearly shown that they have tried to solve it on their own  It is becoming increasingly common to see &quot;what have you tried?&quot; comments in these scenarios. Some examples     Workarounds Flagging Comments - It is considered a good thing to be liberal with comment flagging -- that helps us clean up after the fact. &quot;Too Chatty&quot; is a no-brainer here. Unfortunately, that only cleans up after the damage has been done. All signs point toward the continued increase of the trend of using &quot;what have you tried&quot; comments. I spend a lot of time editing and cleaning up bad questions. This trend came up on my radar toward the end of last year and it is getting worse. So, I thought at the very least that I'd raise some awareness. I've been trying to understand $\sigma$-algebras and how it encodes information in context of filtration. While certain parts seem clear and logical, I can't say I get the whole picture.  I'll try to explain the counter-intuition I get with the classical example of : the probability space $\Omega = \{ HH, HT, TH, TT \}$ and a r.v. $X(\omega)$ equal to the number of heads.  At times $0$, $1$ and $2$ the available information is represented using $\sigma$-algebras $\mathcal{F}_0=\{\emptyset,\Omega\}$, $\mathcal{F}_1=\{\emptyset, \Omega, \{HH,HT\},\{TH,TT\}\}$ and $\mathcal{F}_2=\{\emptyset, \Omega,\{HH,HT\},\{TH,TT\},\{HH\},\{HT\},\{TH\},\{TT\}\}$.  One can notice that $X(\omega)$ is not measurable with respect to $\mathcal{F}_0$ and $\mathcal{F}_1$, because $X^{-1}((\frac{3}{2}; +\infty))=\{HH\}$. To me it is quite surprising: intuitively $X$ makes perfect sense at all times. In particular it has an expected value at time $0$, which I interpret as that the probability and value of all outcomes $\{\omega\}$ can be computed. How do you think of a non-measurable function?  Here's another way of expressing the same confusion. The most natural choice of $\sigma$-algebra in a finite discrete case is $\mathcal{F}=2^\Omega$, and it is implicitly used in all elementary probability problems. However, this choice of $\mathcal{F}$ does not reflect the fact that some information is known or unknown, conditional probability does. Does it mean that the statement "$\sigma$-algebra is known information" make sense only in conditioning? Why is it convenient then? How did they dispose old Joe's wife's body in the movie Looper (2012)? The reason given in the movie Looper for sending targets to the past is that it is difficult to dispose bodies.  From ,     Thirty years into the future in 2074, time travel is invented, but is   immediately outlawed. However, because by that point tracking   technology has rendered it nearly impossible to dispose of bodies   secretly, crime bosses turn to time travel to send their targets to   the past to be killed using "loopers": hired guns paid in silver to   kill whoever is sent to them.   When trying to capture old Joe, they kill his wife. So how did they dispose the body of his wife? Or is it difficult to dispose bodies only in US and not in China? And they came for old Joe only because the Rainmaker wanted to close the loops?  Could someone explain? What am I missing? What are some examples of awkward sounding but grammatically correct sentences? What are some examples of awkward sounding but grammatically correct sentences? Salesforce, Oracle and the Seven Dwarfs Over my time as a Salesforce developer, I've written some code which on occasion managed to surface Oracle plsql exceptions and curiously the error text contains the name of one of Disney's .  I've teased out Doc, Grumpy, Happy, Bashful and Sneezy. I'm sure the other two are not far away.   What is the underlying "thing" on the database platform that is named after a Dwarf? Why were these named after Dwarves?      java.sql.SQLException: ORA-30006: resource busy; acquire with WAIT   timeout expiredORA-06512: at "DOC.CAPEX", line 2200ORA-06512: at line   1: SQLException while executing plsql statement: {call   cApex.update_sysmodstamp(?)}([       java.sql.SQLException: ORA-30006: resource busy; acquire with WAIT   timeout expiredORA-06512: at "GRUMPY.CAPEX", line 2563ORA-06512: at   line 1: SQLException while executing plsql statement: {call   cApex.update_sysmodstamp(?)}([       java.sql.SQLException: ORA-30006: resource busy; acquire with WAIT   timeout expiredORA-06512: at "HAPPY.CAPEX", line 2715ORA-06512: at   line 1: SQLException while executing plsql statement: {call   cApex.update_sysmodstamp(?)}([       java.sql.SQLException: ORA-30006: resource busy; acquire with WAIT   timeout expiredORA-06512: at "BASHFUL.CAPEX", line 2715ORA-06512: at   line 1: SQLException while executing plsql statement: {call   cApex.update_sysmodstamp(?)}([       java.sql.SQLException: ORA-30006: resource busy; acquire with WAIT   timeout expiredORA-06512: at "SNEEZY.CAPEX", line 2718ORA-06512: at   line 1: SQLException while executing plsql statement: {call   cApex.invalidate_agc(?,?)}([      Error: ORA-20000: ORA-06512: at "SNEEZY.SIMPORTLOOKUP", line 850   ORA-06512: at "SNEEZY.SIMPORTLOOKUP", line 823 ORA-06512: at line 1 :   SQLException while executing plsql statement: {call   sImportLookup.get_by_ext_id_text(?,?,?,?,?,?,?)}([ Should a toggle button show its current state or the state to which it will change? I have a quick question about buttons that toggle between two states. (Think Play/Pause, or Shuffle/Regular Play.) As the title says, should the toggle show it's current state or the state to which it will transition?  I think people are used to the Play/Pause convention. But the Shuffle/Regular play might be more confusing if you show the transition state instead of current. For example, the built-in music player on the Xbox 360 does it this way: when it's in shuffle mode, it shows the icon for direct play and vice versa and it always confuses me (am I in shuffle mode or straight play).  I see it this way: Play/Pause is more like action as in begin playing or pause playing. Yes behind the scenes it is a state transition but to the user, there is an action. Whereas Shuffle/Straight Play is an option and it's best to show the current state (and possibly have only one icon and change button to show that the option is enabled/disabled). Thoughts? How to get the current URL within a Django template? Why do close votes expire? I nominated  to be closed as a dup. I see that two other people upvoted my comment, so they might have voted to close it as well. Now, we didn't gather enough votes, and all close votes expired ... and I can't re-vote to close. What is the motivation behind expiring close votes ... especially for close-as-duplicate? Update: Please take into consideration:  Beta Stack Exchange sites have a smaller community, and fewer people with voting privileges Closing as a duplicate is &quot;usually the right thing&quot; IMHO - much less controversial than closing as off topic. After a vote is reset, the original users can't vote again. On a small site, this makes it even harder to get a consensus of five votes.