@DanielSank I keep missing you... I have a question, how do I determine the timescale of the Lindblad Equation in the problem? like in my plot, in the time axis, how do I figure out the units, like if it is femtoseconds or picseconds for example? I wasn't sure to ask it on Physics.SE because i thought maybe it was too trivial of a question or it was to broad...
also, can anybody help me understand Christoffel symbols and covariant derivatives?
where is @ACuriousMind ? I bet he could help...@0celo7 could you help?
@TanMath basically taking the partial derivative of a tensor does not give you a tensor, so you need the partial derivative plus some correction term to make it a tensor and the correction is he Christoffel connection term
@BernardMeurer I realized that innocent, hypen-looking thing in my .tex file was something more sinister when it started rendering as cthulhu-speak in my pdf.
The directional derivative is an operator $\nabla _v$ associated to a vector $v$ that is basically the gradient dotted with $v$
now you can differentiate all sorts of stuff easily
user54412
@BernardMeurer I think I'll change my vimrc to do something when it sees anything outside \x00-\x7f -- maybe I can get it flash red and set off alarm bells.
@TanMath Let $\pi:E\to M$ be a vector bundle with fiber $V$, $\mathrm{dim}\,M=d,\mathrm{dim}\,V=n$. Then a connection is a map $D:\Gamma(TM)\times\Gamma (E)\to \Gamma(E), (V,\sigma)\mapsto D_V\sigma$ with the following properties: (i) $D$ is tensorial in $V$, (ii) $D$ is $\mathbb R$-linear in $\sigma$, (iii) product rule $D_V(f\sigma)= V(f)\sigma+fD_V\sigma,f\in C^\infty(M)$. Let $x\in M$ and let $U$ be a chart domain for $M$ and thus for $E$. Thus we have coordinate vector fields ...
$\partial_1,\dotsc,\partial_d$ on $U$ and using $E|_U\cong U\times V$ we get a basis $\mu_1,\dotsc,\mu_n$ of sections of $E|_U$.
We then define the Christoffel symbols by $D_{\partial_i}\mu_j=\Gamma^k{}_{ij}\mu_k$.
Let $\mu\in\Gamma(E)$. Then, locally, $\mu=a^k\mu_k$ and $$D_{\partial_i}\mu=D_{\partial_i}(a^k\mu_k)=\partial_i(a^k)\mu_k+a^k\Gamma^{l}{}_{ik}\mu_l=(\partial_i a^k+\Gamma^{k}{}_{il}a^l)\mu_k$$
@BernardMeurer 1. physical constants + mass and charge 2. there's lots of physical constants 3. you set them equal to get rid of pesky shit in your equations
@DeNiSkA You can't change the type of a variable per-se you can cast one variable into another one by doing something like this int i = 10;float foo = (float) i;`
So we're casting the variable i of type int into the variable foo of type float
@DanielSank your latest meta post has zero "feedback" by anyone other than me outside of votes. and you say people "care"? there is not much sign of that in meta so far after 2 posts, and significant pushback by EP. have participated substantially on meta in other SEs and this latest experience is not uncommon for me, nor do think it is atypical of metas in general... :|
@DanielSank think there is a big difference between feedback & criticism. this "project" is in very early/ "embryonic" stage and its not fair/ realistic to ask more of it than is feasible/ practical & so far there are very few volunteers etc. lets keep this all in perspective; there is no record of any invited guests anywhere on any SE afaik...
@DanielSank we have different ideas of what constitutes "increments" eh?
Hey I'm the scheduled guest for the june 14th Physics AMA and I was told to maybe make a little presentation and asks for any questions for the AMA people might have, so here it is.
So I am Samuel Lereah, got a Master degree in particle physics from the university of Nantes. My master thesis was...
Hey I'm the scheduled guest for the june 14th Physics AMA and I was told to maybe make a little presentation and asks for any questions for the AMA people might have, so here it is.
So I am Samuel Lereah, got a Master degree in particle physics from the university of Nantes. My master thesis was...
When you work with Heavy quark effective field theories, why do you calculate loops diagrams without traces and gamma matrices? Look here arxiv.org/abs/hep-ph/0307297 pag. 18 for example
This for sure, you neglect the gamma matrices in the numerator, and this is ok. But the trace? There is no constant term arising from this approssimation?
@dmckee Green is too friendly. Red. Grading has to be done in dark, ominous red.
@FrancescoS Read page 17 and 18. They a) write the HQET Lagrangian without the $\gamma$ to begin with and b) explicitly say that the $\gamma$ is replaced by $v$.
and, well, only germans have ¨ characters on their keyboards, it does not mean those characters are not easily accessible with a couple of keystrokes ;-P