Additional books in Tolkien's Legendarium
In what order should Tolkien's writings on Middle-earth be read?
Tensors are mathematical objects that are needed in physics to define certain quantities. I have a couple of questions regarding them that need to be clarified:   Are matrices and second rank tensors the same thing? If the answer to 1 is yes, then can we think of a 3rd rank tensor as an ordered set of numbers in 3D lattice (just in the same way as we can think of a matrix as an ordered set of numbers in 2D lattice)? Why is 8 so special? I have been reading about multi-dimensional numbers, and found out that it's been proven that the Octonions are the composition algebra of the largest dimension. I was wondering why, despite having infinitely many different dimensions of numbers, the only composition algebras are of 1, 2, 4, and 8 dimensions. What's so special about 8? I'm trying to use the eVis plugin in QGIS 3.16.3 to display geotagged photos (as I have in the past without difficulty), but the plugin has totally disappeared. Not only can't I find it as an icon or under the Database menu, but it doesn't appear in the list of plugins (and yes, I am looking in the complete list of all plugins!). Has it been moved somewhere I haven't come across or is it a bug? Run a shell script as another user that has no password I would like to run a script from the main ubuntu shell as a different user that has no password.  I have full sudo privileges, so I tried this:  sudo su -c "Your command right here" -s /bin/sh otheruser   Then I have to enter my password, but I am not sure if that script is now really running under that user.  How can I confirm that the script is really running under that user now? Is there a continuous function such that $\int_0^{\infty} f(x)dx$ converges, yet $\lim_{x\rightarrow \infty}f(x) \ne 0$? I'm planning on re-watching the currently-released 5 Marvel films prior to seeing The Avengers.  Have Marvel released any sort of official viewing order?  Captain America: The First Avenger seems like the hardest one for me to place in order with the rest.  It takes place prior to the other films, but has the greatest number of references to the other films.  So should it be watched first, or last?  The rest of them are relatively clear, as they're chronological in the order they're released, with the possible exception of The Incredible Hulk and Iron Man 2 happening at the same time. How to rename a group of files with what looks like a Windows file path in their names I got a bunch of files with the filename messed up. All the file names have the same beginning which appear to be windows file directories. The problem is there are 700+ files and I really don't want go through and manually rename all of them. These are examples of the file names (Note: None of these have file directories):  G:some\really\long\file\path\then\the\name1.jpg G:some\really\long\file\path\then\the\name2.png G:some\really\long\file\path\then\the\filename.txt G:some\really\long\file\path\then\the\file_name.mov ...   The important take away is that each file has G:some\really\long\file\path\then\the\ before the file name that I would like.   So I would want the above files to look like:  name1.jpg name2.png filename.txt file_name.mov   I've tried the rename command and was not successful. I am still new with Linux and really am not sure on how to go about it or really what to google. Any help would be appreciated. How can I make a special file that executes code when read from Most files on a Linux system are normal files, i.e. they are saved on disk and reading from them just reads from a specified chunk of memory on the disk.  How can I make something that behaves like a file in terms of being able to read from it as one would a normal file, but is actually returning programmatically generated data instead?  As a concrete example, a file that downloads the current google.com and returns it, such that cat ~/myspecialfile would output the contents of google.com to stdout? At the end of the game, how are medals awarded?   As a secondary, what is the relation between bronze silver and gold medals, and how much experience do they reward? I'm a teacher and will ask my students to either bring their laptops with Ubuntu installed with an specific list of packages preinstalled or bring a USB Drive or External Hard Drive with Ubuntu and the packages preinstalled.  For those who are going to bring the USB are two posibilities:   Install with the Ubuntu's "Startup disk creator" program, and telling it to reserve some space for persistence. Boot with a LiveCD and Install Ubuntu in the USB drive.   Then, in either case, boot with that media and install the packages.  So, for my purpose or any other purpose:   What is the best choice and why? Do we have another option? full explanation please. What if the answers of a historical locked question become obsolete? My understanding is that a question is historically locked because the information in it is too valuable for the question to be deleted.   But if the "valuable information" becomes obsolete, what happens then?  We cannot modify the question content, or the answers for a historically locked question, right? The text of the  spell reads:      A flickering flame appears in your hand. The flame remains there for the duration and harms neither you nor your equipment. The flame sheds bright light in a 10-foot radius and dim light for an additional 10 feet. The spell ends if you dismiss it as an action or if you cast it again.   Emphasis mine. The druid in our party asked our DM if he is able to cast produce flame in a dark cave, then opt not to attack with it, and wield a shield and sword. The goal is to continue emitting light, since he doesn't have the light spell. He claims that since the flame does not harm his equipment, he is able to hold a shield or sword with the fiery hand with no problem.  Is this okay to do RAW, or are we missing something?  This is specifically not asking about casting spells with a sword in hand. He wants to draw his weapon after casting and holding the flames.  Related, but not the same question: , , . What EXACTLY happens when I ask to delete my account? I have meticulously read through similar questions, answers and their comments but I still do not understand how the deletion is done. From what I understand I email the customer service and then they do what exactly?     1) They disable my account so that I can no longer use it?      2) They reassign all of my questions and answers to some other   account? To which one?      3) They delete all my questions and answers so that they go away from   public view?   What is the flexibility (if it exists) of the deletion procedure? Is it possible to erase the traces of my former association with the site. Can I request any of the following be done?     4) All of my questions and answers be deleted from public view?      5) Some of my questions and answers be deleted? If yes what criteria?      6) Can I have all of my contributions be assigned to some other   account which runs as sort of a "collective account" and already has   tons of content so that it doesn't happen like my contributions just   move to some other url but still stay grouped under that location and   therefore that location can be discovered as representing my account?      7) Can I have my contributions dispersed through several "collective   accounts?      8) Can my current public name be removed from any comments to my posts   so that my posts cannot be identified later as once belonging to me?   Please be polite with me. I wouldn't have asked if I have found the answer in the other questions. The other questions are also old and it is not clear what the situation is as per 05/2012.  UPDATE (for those interested):  I asked the Stackoverflow team about the procedure. Apparently none of the points 2-8 I asked above are possible, only 1 will take place. The link to my user page from my contributions is going to be removed and replaced with non-clickable text of an anonymized user name like "user1234". Whether this number is the same as my current user_id is not clear. That's all the information I got.  I'm going now to rename myself to "Anonymous" then request the account deletion. Those interested in the procedure will witness the exact result on this page.  Farewell. Why is my toilet bubbling? Last night while my washing machine and sink in the master bath was running, my master toilet started having air bubbles come up.  Then this morning while I was showering I heard bubbles again, and the shower was draining very slowly.  After the bubbles occurred my toilet in the master bath and powder room completely drained of water in the bowl and tank.  What is happening? Spacing problem at List of Figures valueOf() vs. toString() in Javascript PHP replacing special characters like à->a, è->e Hamiltonian Cycle Problem At the moment I'm trying to prove the statement:     $K_n$ is an edge disjoint union of Hamiltonian cycles when $n$ is odd.   ($K_n$ is the complete graph with $n$ vertices)  So far, I think I've come up with a proof. We know the total number of edges in $K_n$ is $n(n-1)/2$ (or $n \choose 2$) and we can split our graph into individual Hamiltonian cycles of degree 2.   We also know that for n vertices all having degree 2, there must consequently be $n$ edges. Thus we write $n(n-1)/2 = n + n + ... n$ (here I'm just splitting $K_n$'s edges into some number of distinct Hamiltonian paths) and the deduction that $n$ must be odd follows easily.  However, the assumption I made - that we can always split $K_n$ into Hamiltonian paths of degree 2 if $K_n$ can be written as a disjoint union described above - I'm having trouble proving. I've only relied on trying different values for $n$ trials and it hasn't faltered yet. So, I'm asking:     If it is true, how do you prove that if $K_n$ can be split into distinct Hamiltonian cycles, it can be split in such a way that each Hamiltonian cycle is of degree 2? Limit memory usage for a single Linux process I'm running pdftoppm to convert a user-provided PDF into a 300DPI image.  This works great, except if the user provides an PDF with a very large page size.  pdftoppm will allocate enough memory to hold a 300DPI image of that size in memory, which for a 100 inch square page is 100*300 * 100*300 * 4 bytes per pixel = 3.5GB.  A malicious user could just give me a silly-large PDF and cause all kinds of problems.  So what I'd like to do is put some kind of hard limit on memory usage for a child process I'm about to run--just have the process die if it tries to allocate more than, say, 500MB of memory.  Is that possible?  I don't think ulimit can be used for this, but is there a one-process equivalent? How can I dynamically unload a javascript file?