Strangely, I've never heard Ext functors referred to by any other name, and so I'm not sure what "Ext" actually means. The only thing I can think of that "Ext" might stand for is "Exterior", which makes a little bit of sense. Does anybody know the meaning and/or history of the term?
The names of the derived functors $\operatorname{Tor}$ and $\operatorname{Ext}$ seem quite cryptic to me. Does anyone know what these abbreviations stand for? I would be glad if someone could tell me where these names come from.
OAuth redirect URL is not honored Animation Cycles rendering remains incredible slow Why can't Transporter technology be used as a weapon? Seems like this is the most powerful weapon of all: transport your enemy into a bulkhead, planet, etc. Transport your enemy's ship inside a planet, etc.  Is there some technical reason that it can not be used this way? A ring element with a left inverse but no right inverse? Can I have a hint on how to construct a ring $A$ such that there are $a, b \in A$ for which $ab = 1$ but $ba \neq 1$, please? It seems that square matrices over a field are out of question because of the determinants, and that implies that no faithful finite-dimensional representation must exist, and my imagination seems to have given up on me :) What does the tilde at the end of a file name stand for? In Windows, I believe that files with a tilde in the file name represent files that are currently open in an application. For example, Microsoft Word creates a file with almost the same name as the file you currently have open, but with a tilde in the name. It's icon is also partially faded. As far as I'm aware, this signifies a temporary file that exists   in case the application crashes and you didn't get a chance to save your file, or to allow the original file to remain unlocked by the file system and accessible to other applications.   In Linux, I ran into a *.log file with a tilde at the end of the file name (scan.log~). Does that mean the log file is currently open in another application that is potentially writing to it? How come everyone easily takes or say the name of "Voldemort" without any fear in Scorpius's world? Why can other users see the files in my home folder? I just added a new, underprivileged "desktop user," and I was surprised to discover that it can see the files in my home folder.  What is the rational for setting up such lax permissions? HTTP GET request in JavaScript? I need to do an  request in JavaScript. What's the best way to do that?  I need to do this in a Mac OS X dashcode widget. Where should I start with Star Trek? (TV series only, not the movies) I haven't seen any of the stuff in the Star Trek franchise, except for one of the movies, and now I want to remedy the situation. I am not interested in the movies, just the TV series. However, since the show has many seasons, I am not interested in watching the show start to finish. So, where (i.e what series/season) should I start with? Do I really need to see the series in real-world chronological order?   Note: I am somewhat familiar with Star Trek, that is I know the basic premise - ships in space, with war between different space-faring sentient species. "Planar" graphs on Möbius strips Good Afternoon all,  I am trying to typeset a symbol that I have been using to represent the integral of a regulated function. This symbol is the standard integral symbol, with the letter "R" superimposed on it.  I have tried using \mathllap, \mathclap and \mathrlap (as suggested ), however none of these have managed to give the desired effect. When I tried doing it without the limits of integration, it got close to working, however then I was unable to have the limits to the right hand side of the symbol:  \mathop{\mathrlap{\int}R}_a^b f   Any help would be greatly appreciated, thank you in advance!  Minimal Example:  \documentclass{article}  \usepackage{amsmath,mathtools}  \begin{document}  Take the regulated function $f$, we want to compare the Riemann integral, $\int_a^b f$ to the regulated integral $\mathop{\mathrlap{\int}R}_a^b f$ by taking sequences of step functions.  We will prove that $$ \mathop{\mathrlap{\int}R}_a^b f = \int_a^b f $$  \end{document} Is it possible to run some code when an assembly is loaded, without doing anything specific in the loading code? What I am looking for is like a static constructor on a type.  Eg:  Assembly A does not know about Assembly B, but B does know about A. Assembly A needs to know certain things about B if B is loaded. When Assembly B is loaded by the runtime (referenced, or explicit), I want a piece of code (static method or attribute) to be executed that calls a method in Assembly A.  The root cause of this problem is unknown types being encountered when serializing a type in A that contains types from B not known at compile time as interfaces are used. How can I explain to people that the phrase “off of ” is grammatically incorrect? How do I drill a 2⅛ inch door knob hole over an existing 1½ inch hole? I need to replace the door knob for this interior door:    The door knobs I've found at the stores require a 2⅛ inch hole.  Mine is only 1½:    Did door knobs used to be smaller?  Is there some place I can find a replacement door knob that will fit my door?  If I need to modify the door to fit a modern door knob, will the new hole completely overlap the old? and can I reuse the latch hole? How would gravity change on a planet rotating around itself very fast? Let's take a planet identical to Earth, but with rotation speed multiplied by ten thousand. What would happen with the gravity if it was spinning madly around itself? Would the centrifugal force make objects seem lighter than on normal Earth? Would the people on that planet be able to jump higher? Where do I put item tags on items inside a chest or your inventory? I cannot respond to comments on my own question (no "add a comment" link anywhere) I joined a new community and asked a question ()  People are commenting &amp; asking questions, but I cannot answer them back. Even "Comment Everywhere" privilege requires 50 reputations and I have 101 reputations.  Am I missing something? Extended Euclidean Algorithm: backward vs. forward How to use C++ 11 features in the latest version of g++ Newbie here. I just got an error running from the terminal a C++ program I wrote: error: ‘stoi’ is not a member of ‘std’. They told me the compiler is too old.  I'm using Ubuntu 14.04.  My g++ version is 4.8.4.  How do I upgrade? Rank of a Matrix Sum I have $3\times3$ matrices such that S=A+B. I know there is an inequality connecting rank of the matrices A, B and its sum S. Could you write down that here? It will be a great help for me.  Means equation  or inequality connecting rank(S), rank(A) and rank(B).