There are a number of Stack Exchange sister sites. I have a hard time signing up with them. I'm presented with three options:   Sign up using Google Sign up using Facebook Sign up using Stack Exchange   I have a Stack Exchange ID, so that's what I want to use.  On filling in my existing name, email, and password (confirmed), I am presented with the puzzling message:     We already have an account with that email address.   If the email is correct, try recovering your account.   Huh? Of course I have an account with that email address. That's what I'm trying to use!  I'm using the right email, the right password. Why do I have to enter any of that? I'm logged into three SE sites right now! Why do I have to type my password twice, and above all, why do I have to "recover my account", which I never lost?  My workaround has been to "recover my account". That means changing my password with all of my existing SE accounts.
For most OpenID options, it doesn't much matter if you pick the "Sign up" versus the "Log in" tab on the sign in page.  Whether you have an account on the site or not, it just does the right thing. Not so if you are using the Stack Exchange OpenID service:    (Bonus bug: the reCAPTCHA box is a bit too wide for the expanded "Sign up using Stack Exchange" container.)  Since we already have collected an email and password (well, two copies of the password), could we not check to see if they match and automagically log the user into their SE OpenID?  If not, the error needs to be reworded somehow to explain that while the email might have been used to create a Stack Exchange OpenID, that doesn't mean they can't log in with that OpenID to create an account.  Counterintuitively, they need to use the  even if they've never had an account there before.  The  link adds to the confusion since it sends an email that leads off with:     Someone requested an account recovery on The Workplace Stack Exchange for jericson@stackexchange.com, but we don't have an account on this site that matches this email address.   (For people with accounts on other sites and/or Stack Exchange OpenIDs, this paragraph is followed by other instructions that would probably work if followed. By that time I imagine many users are at wit's end.)  To simplify: If a user already has a Stack Exchange OpenID (likely because they have an account on another site) they should be able to use the  to sign up for an account or there should be clear instructions on what to do next if they fail.
I want to buy some stock photos like the ones below. What is this design called?  I don't even know how to start searching... Arc length parameterization lying on a sphere Insert Login IP Ranges using apex in salesforce Is it possible to insert to Login IP ranges via apex? Helpful flags not getting updated after getting 'close question' privilege How can I unload Oracle database tables into a csv files? I need to retrieve certain data from an Oracle 11g release 1 database and provide it as one or more CSV files. The data resides in multiple tables and/or views. All this should work via the command line. What would be the best approach to this? $ ls -l /tmp/test/my\ dir/ total 0   I was wondering why the following ways to run the above command fail or succeed?  $ abc='ls -l "/tmp/test/my dir"'  $ $abc ls: cannot access '"/tmp/test/my': No such file or directory ls: cannot access 'dir"': No such file or directory  $ "$abc" bash: ls -l "/tmp/test/my dir": No such file or directory  $ bash -c $abc 'my dir'  $ bash -c "$abc" total 0  $ eval $abc total 0  $ eval "$abc" total 0 How do I show that $x^4-10x^2+1$ is irreducible over $\mathbb{Q}$? Someone says I should use the rational root test, but I don't exactly know how that applies. Thanks for any input. Finding the remainder of $\overbrace{11\ldots1}^{123 \text{ times}}$ divided by $271$ Related post   In Peskin and Schroeder's QFT p28, the authors tried to show causality is preserved in scalar field theory.  Consider commutator $$ [ \phi(x), \phi(y) ] = D(x-y) - D(y-x) \tag{2.53} $$ where $D(x-y)$ is the two-point correlation function,  $$D(x-y):= \langle 0 | \phi(x) \phi(y) | 0 \rangle  = \int \frac{d^3 p}{ (2\pi)^3} \frac{1}{ 2E_{\mathbf{p}}} e^{-ip(x-y)}\tag{2.50}$$  P&amp;S argued that each term in the right-hand-side of (2.53) is Lorentz invariant, since $$\int \frac{d^3p }{ (2\pi)^3} \frac{1}{2E_{\mathbf{p}}} = \int \frac{ d^4 p }{ (2\pi)^4} (2\pi) \delta(p^2-m^2)|_{p^0&gt;0} \tag{2.40}$$ is Lorentz invariant.  Since there exists a continuous Lorentz transformation in the spacelike interval $(x-y)^2&lt;0 $ such that $(x-y) \rightarrow - (x-y) $ and $D(y-x)=D(x-y)$, (2.53) equals zero in the spacelike interval. In timelike interval, since such continuous Lorentz transformation does not exist, (2.53) is non-zero in general.  My question is, consider a non-continuous Lorentz transmation in the timelike interval, $PT$, namely time reversal times parity transformation. I can also let  $(x-y) \rightarrow - (x-y) $. Why (2.53) in the timelike interval is non-zero?  I guess $PT$ will let (2.40) go to $p^0&lt;0$ branch. But I am not sure if it breaks the Lorentz invariant of (2.40) and (2.50). root folder access via gui I'm new to linux and the terminal. As I learn how to use the terminal to navigate through directories, I like to use the gui file explorer to mirror my terminal navigation. The icons and file extension info in the gui file explorer help me figure out what everything is. However, I can't access the root folder via the gui, I can only access it via the terminal. Is there a way to enable access to the root folder outside of the terminal? Given Ohm's law, how can current increase if voltage increases, given fixed resistance? According to Ohm's law, $V=IR$ (voltage equals current times resistance).  So if the voltage increases, then the current increases provided that the resistance remains constant.  I know that Voltage or potential difference means work done per unit positive charge in bringing that charge from one point to another.  So according to Ohm's law, if the work done per unit charge increases then current will increase. How can this be true? Point out my mistakes. Do full frame sensors gather more light than crop sensors? Lots of people say that full frame sensors receive more light than cropped sensors. I have never found a proof of this claim so I tried to do the computation by myself, and proved the contrary! Could you tell me if I am wrong ?  We want to compare the same frame with the same depth of field. I'm not concerned by the quantity of photons by photosite, which is unrelated to sensor size but to the density of pixels. I have neglected effects like vignetting or angle effect on the edge of the micro-lens array. Here is my simple reasoning :  If you want the same  α~2arctan(size/2f) with a full-frame sensor and a crop sensor with crop ratio c, you have to multiply the focal length by approximately c. Now, in order to maintain the , the f-number N have to be divided by c. If we measure the "amount of light" with the well defined  Ev provided by the same frame of the same scene (so the  is fixed), we have Ev ~ f/N.  Putting all together, Ev_crop = Ev_ff x c², so the cropped sensor receive more light than the full frame sensor !  For those who are interested in the price of two equivalent systems, one with a FF+50mm+135mm and the other with Crop+35mm+85mm, see this . "Each person's car" vs. "each persons' car" Which of the following is correct?        Each person's car has four wheels.   Each persons' car has four wheels. I rent a VPS that uses a SSD of 10GB (Debian 7) and I upgraded yesterday to their "second tier" plan that uses a 20GB disk. However, the "one-click-upgrade" process didn't work as I expected and what they did was to move my data to a bigger drive without actually extending the partitions. So now I have 10GB of unallocated space.  I do run around 5 websites on this VPS with mail accounts and all that jazz and I'm very scared to mess up anything so I called their support and they offered to do the job for me for 80 EUR that I find unacceptable since I thought it was included when doing the upgrade. Their older offers from last year used to be just a one click job but the excuse is that "SSD's are different, so it's up to the user".  Anyway, how can I actually do that without screwing things up and is it possible to do that on a "live" system?  I know a couple of commands so here it goes what I could find:  root@vpsxxxxxx:~# df -h Filesystem      Size  Used Avail Use% Mounted on rootfs          9.9G  7.6G  1.8G  81% / udev             10M     0   10M   0% /dev tmpfs           388M  200K  388M   1% /run /dev/vda1       9.9G  7.6G  1.8G  81% / tmpfs           5.0M     0  5.0M   0% /run/lock tmpfs           775M     0  775M   0% /run/shm /dev/vda1       9.9G  7.6G  1.8G  81% /var/www/clients/client2/web2/log /dev/vda1       9.9G  7.6G  1.8G  81% /var/www/clients/client1/web3/log /dev/vda1       9.9G  7.6G  1.8G  81% /var/www/clients/client3/web5/log /dev/vda1       9.9G  7.6G  1.8G  81% /var/www/clients/client5/web7/log /dev/vda1       9.9G  7.6G  1.8G  81% /var/www/clients/client4/web6/log  root@vpsxxxxxx:~# fdisk -l  Disk /dev/vda: 21.5 GB, 21474836480 bytes 4 heads, 32 sectors/track, 327680 cylinders, total 41943040 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x00000000     Device Boot      Start         End      Blocks   Id  System /dev/vda1   *        2048    41943039    20970496   83  Linux  root@vpsxxxxxx:~# sfdisk -l  Disk /dev/vda: 41610 cylinders, 16 heads, 63 sectors/track Warning: The partition table looks like it was made   for C/H/S=*/4/32 (instead of 41610/16/63). For this listing I'll assume that geometry. Units = cylinders of 65536 bytes, blocks of 1024 bytes, counting from 0     Device Boot Start     End   #cyls    #blocks   Id  System /dev/vda1   *     16  327679  327664   20970496   83  Linux /dev/vda2          0       -       0          0    0  Empty /dev/vda3          0       -       0          0    0  Empty /dev/vda4          0       -       0          0    0  Empty How do I rollback a TFS check-in? I'd like to rollback a change I made recently in TFS. In Subversion, this was pretty straightforward.  However, it seems to be an incredible headache in TFS: Option 1: Get Prior Version  Manually get prior version of each file Check out for edit Fail - the checkout (in VS2008) forces me to get the latest version  Option 2: Get TFS Power Tools  Download Team Foundation Power Tools Issue rollback command from cmd line Fail - it won't work if there are any other pending changes  Option 3: Manually Undo Changes  manually undo my changes, then commit a new changeset  Question How do I rollback to a previous changeset in TFS? Sitemaps - one per subdomain or one for the base domain? I have more than 5 subdomains on a project, say developer, www, staff and some more, what is the best practice in creating sitemaps?   All subdomains that share a same sitemap at base domain (example.com/sitemap.xml) ? or different sitemaps for different subdomains?(developer.example.com/sitemap.xml and www.example.com/sitemap.xml)   Since the subdomains are several parts of the main application, what are the pros and cons of each, and what should I consider while choosing the one over the other? (one sitemap per subdomain or one for the whole site) How can I prove that if $n$ is even then $n^2$ is even and if $n$ is odd then $n^2$ is odd? Why can't we see light travelling from point A to B? Let's say we have a cloud of dust which is a lightyear across and someone shoots a beam of light from point A to B , why it is not possible for an observer far far away to see the light while it travels through the cloud at the speed of light? Headers and font in KOMA-script I am setting up the layout for my bachelor thesis using scrbook as basis for a self-made documentclass with twosided print. I want a header containing the current part number and name on the outer side (left on even pages, right on odd pages), the current chapter number and name on the center of the head and the same for section on the inner side. I found this example in the KOMA-Script documentation:  \usepackage{scrlayer-scrpage} \pagestyle{scrheadings} \automark[chapter]{chapter} \automark*[section]{}   It puts the chapter on the outer side on even pages and the section on the outer side on odd pages. Sadly, I was not able to modify this to fit my needs because I do not really understand the way KOMA-Script works here. If a part starts but there is still no chapter in it, the place for the chapter shall remain empty (same for chapter and section). Can anyone help?  Furthermore, I would like to change all fonts that KOMA-Script changes (e.g. toc, section, chapter...) back to the default computer modern as I do not like the font KOMA-Script uses here. Is there a better way than changing all the fonts manually like this:  \addtokomafont{section}{\fontfamily{cmr}\selectfont} Calculate the Factor Group $(\mathbb{Z}_4 \times \mathbb{Z}_6)/\langle(0,2)\rangle$