Is Weyl transformation part of diffeomorphism? Does a gravitational anomaly capture also the anomaly due to Weyl transformation?
Conformal transformation/ Weyl scaling are they two different things? Confused!
A special bijection between $\mathbb{R}\times \mathbb{R}$ and $\mathbb{R}$ Materials for learning TikZ Expanding a parent  to the height of its children I have a page structure similar to this:  &lt;body&gt;   &lt;div id="parent"&gt;     &lt;div id="childRightCol"&gt;       /*Content*/     &lt;/div&gt;     &lt;div id="childLeftCol"&gt;       /*Content*/     &lt;/div&gt;   &lt;/div&gt; &lt;/body&gt;   I would like for the parent div to expand in height when the inner div's height increases.  Edit: One problem is that if the width of the child content expands past the width of the browser window, my current CSS puts a horizontal scrollbar on the parent div.  I would like the scrollbar to be at the page level. Currently my parent div is set to overflow: auto;  Can you please help me with the CSS for this? Object has no method 'live' - jQuery Reading/Writing a MS Word file in PHP Is it possible to read and write Word (2003 and 2007) files in PHP without using a COM object? I know that I can:  $file = fopen('c:\file.doc', 'w+'); fwrite($file, $text); fclose();   but Word will read it as an HTML file not a native .doc file. A week ago I  people on this site what mathematical background was needed for understanding Quantum Physics, and most of you mentioned Linear Algebra, so I decided to conduct a self-study of Linear Algebra. Of course, I'm just 1 week in, but I have some questions.    How is this going to be applicable to quantum physics? I have learned about matrices (addition, subtraction, multiplication and inversion) and about how to solve multiple equations with 3 unknowns using matrices, and now I am starting to learn about vectors. I am just 1 week in, so this is probably not even the tip of the iceberg, but I want to know how this is going to help me.  Also, say I master Linear Algebra in general in half a year (I'm in high school but I'm extremely fast with maths), what other 'types' of math would I need to self-study before being able to understand rudimentary quantum physics mathematically? What is the name of the operation $v^T H v$? To find out how something is called is the one thing I don't know how to use Google for.  If I have a vector $v$ and a symmetric matrix $H$, then the operation $v^T H v$ gives me some sort of projection of the matrix $H$ on the vector $v$. For example if $H$ is the Hessian, the operation gives me the second derivative in the direction of $v$.  What is the name of this operation? Effects of continuing after a total party wipe? I've had a couple of encounters so far where I stumbled into enemies that were higher level than expected and gotten wiped out. At the game over screen, I chose the option "Continue". After doing so, I didn't notice any negative consequences. I was plopped back just a few metres from the area I died, and was free to continue on as if nothing had happened. Am I missing something? Is there some negative effect from a party wipe? How can I adjust Cycles material displacement amount? Formula for the $n$th term of $1, 2, 2, 3, 3, 3, 4, 4 ,4, 4, 5, ...$ Must $k$-subalgebra of $k[x]$ be finitely generated? I know the usage of     This is a new car.   This is singular.     These are some books for you.   These is plural.  Shall we use   There exists some people who agree with me. There exist some people who agree with me.   Which one is the correct usage and why? In $\mathbb{Z}/(n)$, does $(a) = (b)$ imply that $a$ and $b$ are associates? [Update: Based on the hints provided by @zcn and @whacka, I believe I have found a solution. See my answer below.]  Below, $R$ is a commutative ring with $1$.  In John J. Watkins' Topics in Commutative Ring Theory, the author observes that if $a$ and $b$ are associates in $R$, then they generate the same ideal: $(a) = (b)$. This is clearly true, because $a = ub$ and $b = va$ for some units $u$ and $v$, and so $a \in (b)$ and $b \in (a)$, whence $(a) \subset (b)$ and $(b) \subset (a)$. Indeed, we didn't even require $u$ and $v$ to be units to reach this conclusion.  The author then claims that if $R$ is not a domain, then the converse may not be true: we may have $(a) = (b)$ even if $a$ and $b$ are not associates. As a "counterexample" he gives $R = \mathbb{Z}/(6)$, with $a = 2 + (6)$ and $b = 4 + (6)$. Clearly these elements generate the same ideal: $(a) = (b) = \{0, 2 + (6), 4 + (6)\}$. The author asserts that $a$ and $b$ are not associates, but this is false: $5 + (6)$ is a unit, and $(2 + (6))(5 + (6)) = 4 + (6)$, so $a$ and $b$ actually are associates.  I figured that the author botched the example but that surely the basic fact must be true: if $R = \mathbb{Z}/(n)$ then there may be nonassociates $a,b \in R$ with $(a) = (b)$. However, I was not able to find a counterexample and eventually resorted to writing a computer program and found that there are no counterexamples in $\mathbb{Z}/(n)$ for $n \leq 100$.  So now I'm starting to think that there is no counterexample in $\mathbb{Z}/(n)$ at all, but I have not yet been able to prove this.  My questions:   If I am correct that $(a) = (b)$ in $\mathbb{Z}/(n)$ implies that $a$ and $b$ are associates, I would appreciate a nudge in the right direction toward a proof. (But if the proof is elementary, please give only a hint, not a solution :-) I'll post my solution once I have one. In either case, could you please point me to a genuine counterexample? If there is one in $\mathbb{Z}/(n)$ for some $n$, that would be ideal (no pun intended), otherwise a counterexample in any commutative ring with $1$ would be great. How to get a normal application menu in the top- or titlebar in Gnome Do I need quote marks when I quote myself? "404. That’s an error." when viewing from Google cache My site is getting 404. That’s an error. message when I click on cached from Google search results.  This is the error message from Google:  That’s an error.   The requested URL /search?q=cache:8kxLAgFrhZQJ:www.mysite.com.....&amp;cd=8&amp;hl=en&amp;ct=clnk&amp;gl=uk was not found on this server. That’s all we know.  What I did before I was getting this error is that about 10 days ago, I moved my hosting from Ixwebhosting to Gearhost (cloud based). I also added 301 redirect from non www to www.  I have no idea why I am getting this error. Please advise what might be the reason if there is a solution for it.  All of my pages are indexed by Google though. Flag Question Link After 3k Rep I noticed from a question about flagging vs closing (forgive me, I cannot find the link, please post it if you know it), that flags are CONVERTED into close votes for questions automatically. Can somebody confirm this?  If confirmed, I was wondering why the link (again, for questions only) is simply not removed to avoid confusion? I'm trying to compute the shadow of 3D objects on the ground. To do this I'm assuming parallel rays from Sun origin.   Let's assume the Sun direction is given by azimuth $\varphi$ and elevation $\theta$ angles. So the direction unit vector is retrieved as:  $$ \hat{\mathbf{s}} = \mathbf{R}_y\left(\theta\right)\mathbf{R}_z\left(\varphi\right)\hat{\boldsymbol{\imath}}$$  where $\mathbf{R}_{x/y/z}$ are the rotation matrices along the $x, y, z$ axes given by, for example, Euler-Rodrigues equation, and $\hat{\boldsymbol{\imath}}$ is the unit vector along $x$-axis.  A point on a ray-line has the equation:  \begin{equation} \mathbf{r} = \mathbf{r}_p + \lambda\hat{\mathbf{s}}  \tag{1} \end{equation}  being $\mathbf{r}_p$ a point on that line.  A point on a general plane is given by the equation:  \begin{equation} \left(\mathbf{r} - \mathbf{r_0}\right)\cdot \hat{\mathbf{n}} = 0 \tag{2} \end{equation}  being $\mathbf{r}_0$ a point on the plane and $\hat{\mathbf{n}}$ the unit vector normal to that plane.   Ensuring the validity of both equations (1) and (2) allows to compute the $\lambda$ multiplier and retrieve the position vector of the projected point (writing $\tilde{\mathbf{r}} = \mathbf{r_p} - \mathbf{r_o}$)  \begin{gather} \lambda = - \left(\frac{\tilde{\mathbf{r}}\cdot \hat{\mathbf{n}}} {\hat{\mathbf{s}}\cdot\hat{\mathbf{n}}}\right) \\ \mathbf{r}_\text{proj} = \mathbf{r}_p - \left(\frac{\tilde{\mathbf{r}}\cdot \hat{\mathbf{n}}} {\hat{\mathbf{s}}\cdot\hat{\mathbf{n}}}\right)\hat{\mathbf{s}} \tag{3} \end{gather}  Applying eq. (3) to all the vertices of a mesh $\left\{\mathbf{r}_{p_i}\right\}$ .   A problem can be noted: $\hat{\mathbf{s}}\cdot \hat{\mathbf{n}}$ can be zero (e.g. Sun is horizontal, i.e. the ray is ortogonal to the normal of plane).   Are there some conceptual mistakes in my reasoning? Is there a way to rewrite the operation as a linear operator applied to the set of vertices position vectors?   $$ \left[\mathbf{A}\right]\left\{\mathbf{r}_{p_i}\right\} = \mathbf{r}_\text{proj}$$ In C, what is the difference between using ++i and i++, and which should be used in the incrementation block of a for loop? How to suppress Terminated message after killing in bash?