What is the origin of the electric charge? In order to explain mass we had to postulate the existence of a quantum field (Higgs field), and we say that elementary particles get their mass by interacting with this field.   But where does electric charge come from? Is electric charge the result of particles interacting with some field or is it just a property of some fields (e.g. electron field)?
Baryons have charges that are the result of a polynomial calculation of their building blocks (quarks)'s fractional charges. But what gives these quarks electric charges? What interactions do they have with photons? And what about leptons, like muons and electrons? How do they get their -1 charge? And then, how do positrons and anti-muons get +1 charge? Same goes for quarks: how does up-antiquarks get -2/3 charge? Or I may want to formulate my question this way:  How does any elementary particle interact with the EM-Force to get an electric charge?
How can I define a mathematical function as a LaTeX macro? Active login not recognized on Super User There is a way to add custom split normal use Python API? I can't find a way to achieve custom split normal effect. I want to use python (mesh normal/hard edge or soft edge) data collected from Maya then write to Blender mesh.    How to do it using the following Python API and how?  bpy.data.meshes[objName].normals_split_custom_set_from_vertices  bmesh module Are "pushforward" and "pullback by zero section" of diffrentials isomorphic in elliptic curves? Let S be a scheme, $p:E\rightarrow S$ be an elliptic curve with zero section $e:S\rightarrow E$. My question is: Are $p_*(\Omega_{E/S}^1)$ and $e^*(\Omega_{E/S}^1)$ isomorphic? I think it's right because I saw both definitions in different notes and they seem to represent the same thing. Thank you! Align cell height of the tabularx rows The following latex code prints rows one at a time. However all the cells of the rows don't come out aligned. How can I fix it.   \documentclass{beamer}     \usepackage{tabularx}    \begin{document}  \begin{frame}{}  \begin{tabularx}{3.50in}{lXX}           \hline           &amp; Observation &amp; Conclusion \\           \hline             \uncover&lt;2-&gt;{1.} &amp; \uncover&lt;2-&gt;{Observation 1 } &amp; \uncover&lt;2-&gt;{Conclusion 1} \\   \uncover&lt;3-&gt;{2.} &amp; \uncover&lt;3-&gt;{Observation 2} &amp; \uncover&lt;3-&gt;{Conclusion 2} \\           \end{tabularx}      \end{frame}   \end{document}   The output looks as follows :    As we can see cells in first column do not align with the rest of the rows. Will appreciate any input as to how to fix this. The number of (non-equal) forests on the vertex set V = {1, 2, ...,n} that contains exactly 2 connected components is given by The number of (non-equal) forests on the vertex set V = {1, 2, ...,n} that contains exactly 2 connected components is given by $\sum_{k=1}^{n-1} {n-1 \choose k-1} k^{k-2} (n-k)^{n-k-2}$.  I am unsure how to approach this question. Could someone guide me through the proof? If G is a spanning tree and it is disconnected then I know it is a spanning forest. Also, I know by Cayley's thm that there are $n^{n-2}$ nonequal tree on a vertex set V = {1, 2, ...,n} which is where i'm assuming the $k^{k-2}$ comes from but I do not understand where the rest of it is coming from. Schengen Visa Refusal: Justification for the purpose and conditions of the intended stay was not reliable Schengen refusal formulae can be difficult to understand sometimes.  Sometimes an applicant receives a refusal with:       Justification for the purpose and conditions of the intended stay was not reliable.     often accompanied by:       Your intention to leave the territory of the Member States before the expiry of the visa applied for could not be ascertained.   What is meant by this refusal reason?  What are they trying to say? How can I create a product key for my C# application? How can I create a product key for my C# Application? I need to create a product (or license) key that I update annually.  Additionally I need to create one for trial versions.  Related: the (surely simplistic) model of a bipolar junction transistor one is taught in foundational physics course appears to be symmetric. - So, what is the difference between the collector and the emitter of a real BJT? If the transistor were symmetric one would not make this distinction...  Also:   Do BJTs have a 0.6V voltage drop like diodes? Are BJTs conductive in both directions, i.e. E-C and C-E?   Many thanks. The difference between "have a lunch" and "have lunch" Is there any difference between     I am not having a lunch tomorrow.   and     I am not having lunch tomorrow.   This is a follow up question of : . My two main questions:  Are all URLs that include your User Id tracked?  Can the visitors who use the tracked URLs have Stack Exchange accounts?   Specifically: Recently the ability to earn badges for sharing links to posts on Stack Exchange sites . I'd like to know when and how this tracking works. It's clear that if you go to a question, and make use of the link button, you will get a URL with your User ID that will be tracked if a visitor uses it to get to SO. For example, let's use  as an example. It's regular URL is:  https://stackoverflow.com/questions/309300/defend-php-convince-me-it-isnt-horrible  If you go to that page and use &quot;save link as&quot; in the link section of the question you will be given a tracked url with your User ID:  https://stackoverflow.com/q/309300/[USER ID]  My question is, are there other URLs that would be tracked? All of the following URLs take you to the Question / Answer, but are they tracked? For example what if I just tack my User ID onto the long url?  https://stackoverflow.com/questions/309300/defend-php-convince-me-it-isnt-horrible/[USER ID]  What if I add my User ID to an answer URL?  https://stackoverflow.com/questions/309300/defend-php-convince-me-it-isnt-horrible/309622#309622/[USER ID]  or even  https://stackoverflow.com/q/309622/[USER ID]   Is there a way to know that a URL is being tracked? Is there some sort of format to follow? Are the only tracked URLs the ones provided in the Question links? Finally, does this sentence from the blog post mean that visitors cannot have an account?  Also, the tracked IPs must originate from outside our existing network. Is normality testing 'essentially useless'? In League of Legends, there are a number of effects which revive a champion upon death.  The item  is the most well-known and widely used of these.  I was wondering, however, whether its effect would come before or after other revive effects?  I have two examples.  First, Zilean's ultimate  will provide a champion with a Guardian Angel -like buff for a limited time.  If a champion has this buff in addition to a Guardian Angel, which effect will happen first?  Second, Anivia's passive  allows her to come back to life if her egg is not destroyed after she is killed.  If she has a Guardian Angel, will her passive be triggered before or after it? How does this compare to  and ?  It seems like in one case it is more beneficial to have Guardian Angel's precedence be greater, and in the other it is more beneficial to have it be less.  In the first scenario, if the Guardian Angel was triggered first, then Zilean would have a good chance of simply wasting his ultimate.  On the other hand, if it is triggered after these revival effects, then Anivia could not get the full benefit of her passive.  Is there a set order of precedence, or does each revival effect have their own unique "priority level" that is explicitly detailed for each ability? How to auto-start unprivileged lxc containers? On Ubuntu 14.04, I have created an unprivileged container that I can manually start and stop.  But I would like this to start and stop along with the system.  I have added the following to the container's configuration:  lxc.start.auto = 1 lxc.start.delay = 5   However, the system scripts don't seem to pick unprivileged containers.  There is  related to this on linuxcontainers.org, but the solution seems to be restricted to root user.  Is there a clean way to do this for a non-root user (with root user's consent)? Stuck in a loop at login prompt after changing shell to zsh Windows 8 upgrade Recovery Disk I have upgraded to Windows 8 from Win 7. I want to create a recovery disk for Windows 8, just in case something goes wrong. I didn't find the option of creating it from the control panel.  How do I create a Recovery CD/DVD? I am trying to convince my friend that the integral of $0$ is $C$, where $C$ is an arbitrary constant. He can't seem to grasp this concept. Can you guys help me out here? He keeps saying it is $0$. So,  Each of my polygons is a separate object. Their default normals point like this:   But their orientation or local axes are like so:   How can I make their local axes to be like so, but automatically?   I guess particles might be one solution for this exact case (if you emit new objects on top of the existing ones) but let's say the original objects are triangles and I wouldn't want to change their shape and pointing direction at all, only their local orientation axes, would that be possible?  Cheers! proof that topologist sine curve is not locally connected I know that this question has been asked before, but it is still not clear to me why the topologist sine curve is not locally connected.     The topologist's sine curve: Let $S$ denote the following subset of the plane. $$S = \{ (x, \sin(1/x)) \mid 0 &lt; x \le 1\}.$$ The set $\bar{S}$ is called the topologist's sine curve, which equals the union of $S$ and the vertical interval $0 \times [-1,1]$.   My attempt was:  Fix a point $p = (0, t)$ where $t &gt; 0$, and consider a neighborhood $N = B(p,\delta)\cap\bar S$, where $B(p,\delta)$ denotes a ball centered at $p$ with radius $\delta$.  Then, I want to show that every open subset of $N$ is disconnected, so there can't be connected neighborhood of $p$ contained in $N$.  But, I am having a trouble with establishing that every open subset of $N$ is disconnected.  How can I prove the claim? When does System.gc() do something?