dingo_d
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 Feb 6 asked Warped AdS${}_3$ and symmetry breaking Feb 6 comment Changing vector basis in AdS$_3$ I should be able to change the basis with: $V^{\mu\prime}=V^\mu g_{\mu\nu} \frac{\partial x^\nu}{\partial x^{\nu\prime}} g^{\mu\prime \nu\prime}$, where primed are new coordinates ($\tau,\sigma,\phi$), and not primed are old ($x,y,u,v$), but I'm not getting a good result :\ Feb 5 comment Changing vector basis in AdS$_3$ I'll try this and see the result. Feb 5 comment Changing vector basis in AdS$_3$ I can make $\partial_\tau=\frac{\partial x}{\partial \tau}\partial_x+\frac{\partial y}{\partial \tau}\partial_y+\frac{\partial u}{\partial \tau}\partial_u+\frac{\partial v}{\partial \tau}\partial_v$, but that doesn't help much :\ Feb 4 comment Changing vector basis in AdS$_3$ I did this on paper, for which I get: $\partial_x=\frac{\partial \tau}{\partial x}\partial_\tau+\frac{\partial \sigma}{\partial x}\partial_\sigma+\frac{\partial \omega}{\partial x}\partial_\omega$, but I kinda got stuck there :S Should I express $\tau,\sigma,\omega$ in terms of $x,y,u,v$ then? Is that even possible? :\ Feb 4 asked Changing vector basis in AdS$_3$ Jan 25 comment Measuring background radiation The water in the nuclear power plants has boron in it that absorb neutrons if I recall correctly ;) Jan 13 comment Squashed 3-sphere? Yeah, that was what I was thinking. It's not really intuitive. I would expect something that was more standard 3 sphere metric looking... But thanks nonetheless :) Jan 13 comment Squashed 3-sphere? Oh, so that's where all the similarity with warped AdS${}_3$ comes from. Just a warped sphere in a sense... Jan 13 asked Squashed 3-sphere? Jan 10 accepted Different definition of SL(2,R) algebra? Jan 10 comment Different definition of SL(2,R) algebra? I was just reading something about structure constants and thought that that might be the answer! So it is only difference in the given representation after all. Jan 10 comment How do I correctly choose signs for a falling particle? Have you tried setting up a coordinate system? That should help... Jan 10 comment Different definition of SL(2,R) algebra? Sorry, forgot about that, corrected it now. Jan 10 asked Different definition of SL(2,R) algebra? Jan 7 comment Energy dispersion in graphene See this: en.wikipedia.org/wiki/Density_of_states It has basically all you need ;) Jan 6 answered Energy dispersion in graphene Jan 6 comment Energy dispersion in graphene If I'm not mistaken, there are two carbon atoms per primitive cell, and each has 3 nearest neighbors, so that should be correct. For DoS you need the expression: $g_{2d}(E)=\frac{1}{A}\sum_k\delta(E-E(k))$ if I recall correctly. Then you assume that you have a large volume and go to continuous limit, from sum to integral. Then it's just solving the integral (transform the integral from $k$ to $E$ to integrate and that should be it) Jan 6 comment Energy dispersion in graphene Well you need to draw the crystal structure of graphene, then you can find the unit cell, primitive cell, all the info about Bravais lattice. Then you can see the number of nearest neighbors. For DoS you can search the google density of states for graphene, and 4th pdf has about this. Also look your literature: Kittle, Ashcroft Mermin... graphene is really popular and there is a lot of info on it. Dec 28 comment Really nothing special when falling into a black hole? If I remember correctly the bigger the black hole is, the tidal forces that the body feels are weaker, and the smaller it is they are stronger, but in all reality if you are falling in the black hole you are doomed one way or another :D