Which of the following is right?  I am reading a paper (math) where it says:  Demanding that A is a Lorentz scalar, ...  But I feel like it should be  Demanding that A be a Lorentz scalar, ...  I'd be grateful for help and would appreciate if someone could point out what kind of grammatical construction this actually is.
We will make the convention that exact categories be skeletally small.   Is this construction (used in a mathematical context) correct? There is something that strikes me as odd in that "be". Should it be "are"? I know I've seen a similar way of using "be" like that, without conjugating the verb, but I'm not completely sure when it should be used.
What do "." and ".." mean when in a folder? when I used ls -a to view hidden files in folder there were 2 hidden files created by default what is the significance of this two files . and ..?  ls -a   Produces  .  .. What would be the disadvantages of using a 4 stranded ethernet cable? I got this cable with a homeplug AV 200 device - its labelled cat 5e    But looking at the plug end has me rather dubious about it.   (There's only 4 strands there, not the standard 8 - and missing pins, so I suspect these cables are designed to do so. The wire jacket is also surprisingly loose).  Another angle. This isn't a standard connector, no, someone has went and made a non standard connector specifically for this    I figured the cable was crap so I cut into it - some of you were wondering if they had merely left out the additional pairs - and the answer is no - its basically half a cat 5 cable.    I'm currently using it for some legacy equipment that runs on fast ethernet and the plug it came with and it seems to work. However, I'm curious - what're the downsides of such a cable? What do I need to look out for? In what situations would this cat-5 cable be unsuitable for use in anything other than a ethernet cat o'nine tails? Four balls with different colors in a box, how many times do I need to pick to see all four colors? Here is the situation.  I have hexagonal board,and a unit on it,with speed or move value 4.Diffrent terrain has a diffrent cost.When i click on the unit,game should show me a move range.  My solution was to check each  hex in range of 4,with A* pathfinding,and if path cost was less than 4 then this hex was in range.Finally game nicely show me range of that unit.  My question is:   Is there other solution to search for range on hex grids or square grid,because even if i am really proud of what i did in my solution,i think,it is a little to exaggerated?:))  What make me ask this question?I noticed that when unit speed is 4 or 6 or even 8,time to computing range for my computer was really good,but when speed was 10 and more i noticed that i needed to wait few second to compute.Well in real games i rather dont see something like this and my A* pathfinding is rather well optimized,so im thinking that my solution is wrong.  Thanks for any replies. Show a matrix in detail Below it is a very useful command to create a matrix. But it has a short point to me since it shows Parentheses not Square brackets. My question it how should I change this to show square brackets? I appreciate your answer. Thank you so much.  \[ K =   \underbracket{\begin{pmatrix}    K_1 &amp; 0      &amp; 0    \\    0   &amp; \ddots &amp;    0   \\    0   &amp; 0      &amp; K_n    \\    \end{pmatrix}}_{d\times M} \] Help, i tried installing kaltools and my Ubuntu is messed up! I tried installing Kali Linux tools.  I started installing some tools and there were several things I had to "agree" to and one message said add users... something in terminal, and when I came back I saw terminal reporting removing a bunch of core programs that I needed. I canceled the process but I don't know if I should reinstall Ubuntu or not.  How can I repair my system? Not to Mention ≈ [Let Alone ≈ Much Less ≈ Still Less] For brevity, I symbolise synonymity with ≈.  So  X ≈ Y  means  X and Y are synonyms.  From : let alone ≈ not to mention  From :  let alone ≈ much less ≈ still less.  Are these all synonyms? What are the similarities and differences between each? Can you find all classes in a package using reflection? Is it possible to find all classes or interfaces in a given package? (Quickly looking at e.g. , it would seem like no.) When should you use generator expressions and when should you use list comprehensions in Python?  # Generator expression (x*2 for x in range(256))  # List comprehension [x*2 for x in range(256)] How to debug an unmet dependencies problem? How would you make a comma-separated string from a list of strings? Proof that if $s_n \leq t_n$ for $n \geq N$, then $\liminf_{n \rightarrow \infty} s_n \leq \liminf_{n \rightarrow \infty} t_n$ This is half of Theorem 3.19 from Baby Rudin. Rudin claims the proof is trivial. What I've come up with so far doesn't seem trivial, however, and is probably also wrong (my problem with it is pointed out below). This makes me wonder whether I'm overlooking some useful fact and/or using an unprofitable approach.  Theorem. If $s_n \leq t_n$ for $n \geq N$, where $N$ is fixed, then  $$ \liminf_{n \rightarrow \infty} s_n \leq \liminf_{n \rightarrow \infty} t_n. $$  Proof. Suppose that $s_n \leq t_n$ if $n \geq N$, but that  $$ \liminf_{n \rightarrow \infty} s_n &gt; \liminf_{n \rightarrow \infty} t_n. $$  Let $E_s$ denote the set of all subsequential limits of $\{s_n\}$, and let $E_t$ denote the set of all subsequential limits of $\{t_n\}$. Then  $$ \inf E_s &gt; \inf E_t. $$  This implies that there exists some $x \in E_t$ such that $\inf E_s &gt; x &gt; \inf E_t$, since otherwise $\inf E_t$ would not be the greatest lower bound of $E_t$. Hence some subsequence of $\{t_n\}$, say $\{t_{n_i}\}$, converges to $x &lt; \inf E_s$.  Lemma. (from Rudin) If $x &lt; \liminf_{n \rightarrow \infty} s_n$, then there exists an integer $N$ such that if $n \geq N$, then $s_n &gt; x$.   By the lemma, there exists an integer $N_0$ such that if $n \geq N_0$, then $s_n &gt; x$.   Now, let $\epsilon = \inf_{n \geq N_0} \{s_n - x\}$. This is where I think my proof breaks down. Can't $\epsilon$ be zero? Then, since $\{t_{n_i}\}$ converges to $x$, there exists an integer $N_1$ such that if $n_i \geq N_1$, then $|t_{n_i} - x| &lt; \epsilon$. But this means that, if $n_i \geq \max\{N, N_0, N_1\}$, we have both  $$ s_{n_i} &gt; t_{n_i}, $$  as well as $s_{n_i} \geq t_{n_i}$, a contradiction. If $k>0$ is a positive integer and $p$ is any prime, when is $\mathbb Z_p[\sqrt{k}] =\{a + b\sqrt k~|~a,b \in\mathbb Z_p\}$ a field. Why does (insert favorite search engine here) get better search results than SO, SF, or SU's own search function? I've lost count of the number of times I've either asked a question or been answering a question only to have it closed as an exact duplicate. But searching for the question turns up  a list of seemly unrelated results using the sites builtin search. Then if I switch to a general web search engine and limit its scope to just SO, SF or SU I find the question within the first two or three results.  Why is this?  I'm pretty sure this isn't an exact duplicate of another question though I did find some that were at least somewhat related (using google).  Update:  I also have gotten (somewhat) better results by simply typing a question and browsing the generated list of related questions. Still a search feature that doesn't return good results isn't going to be used by most people.  Common sense would suggest (though common sense isn't always the best indicator) that a targeted solution to a specific problem domain should be superior to a generalized solution. In most cases this appears to hold true. I  have had no luck getting the buffer tool to accept anything but degrees as units of measure.  I have found lots of stuff saying the layer needs to be reprojected and saved but it hasn't worked at all for me.   Is there a way I could create a buffer without using ftools or at least force the units to meters somehow?  As a workaround I converted meters to degrees (lat) and used that but the final product needs to be as close to reality as possible.  Things I've tried:   setting every unit option I could find to meters (where possible). setting everything to NAD83/Maryland (data is for Washington, DC) and saving it as such (as layers in ESRI shape files). reimporting the reprojected layers setting relevant layers to Google Mercator   The was tried followed by creating a buffer. Many were tried in combination. QGIS 1.7.3 Slackware64 current (qgis from SBo-13.37 repo, tried on multilib and plain 64it with same results) Can I travel to Australia in less than 2 weeks if I transfer my visa to my new passport? I transferred my visa to my new passport and it’s saying it takes 2 weeks to come, my flight is Sunday I arrive in Sydney Monday at night, I still have my old passport! If I bring that will they let me go into the country because my new one literally arrived two days ago! And the visa will be transferred in 2 weeks! Will I have to push my flight or will I be left? The Follow Questions and Answers feature is now live across the Network We are happy to announce that the  follow question and answer feature is now live across the Network, including Stack Overflow, all Stack Exchange sites, and all Meta sites. (International Stack Overflow sites will have it turned on in a day or two once we have translations all set.) You can follow any question or answer (that you did not author) by clicking on the [follow] button that is shown in the menu immediately below the post (alongside the [share] button):    After you have followed a post, you will get inbox notifications for all new answers (in the case where you followed a question), comments, edits, and notices. You will not receive notifications for any action that you performed. As was mentioned in the earlier post, we are not making changes at this point to the notifications received by a post owner, or due to @mentions. The initial release had been planned to only include question following. Thanks to many folks who chipped in over the past few weeks, we are happy to release both question and answer following at the same time. These are available in both the regular and mobile views. We are still planning on two more related releases:  Follows profile tab and question listing filter: A tab for follows will be added to your user profile activity page. Each user will be able to view this tab that will provide a listing of followed questions and answers, with standard sorts, and the ability to unfollow from the listing. Users (with the exception of moderators and authorized staff) will not be able to see this information about other users (nor will it be made public in the API, SEDE, or data dumps). We will be renaming the Favorites feature to Bookmarks. As we mentioned in the preview post, the feature will be the same as Favorites, with the name and icon updated to more accurately represent user expectations and usage. And you will be able to both &quot;bookmark&quot; and &quot;follow&quot; a question.  We hope that this new feature will allow you to have better access to the content that you care about and want to keep tabs on. Update (June 11, 2020): The user profile tab and the rename of Favorites to Bookmarks have been released. Excel automatic hyperlinks Computer doesn't boot up, shows PXE error and/or "operating system not found", "no bootable device", "insert boot media", or other similar error How do I get on a Minecraft PE server when it says 'invalid name'? I am having trouble getting onto a server in Minecraft PE on iOS. When I tap on the person's server it just says invalid name:    I have tried turning off and restarting the iPad, going to home screen and logging back into the server but I have had no luck and no change. Is there a reason why this is so?