Recent content by maddy

I presume you're replying to jjiimmy101's original question on top? :rolleyes:

Someone argued that a zero vector has direction. Isn't this so ridiculous? As far as I know a zero vector is just a point. How can a point have directions?

This may be a stupid question but hopefully someone can clarify. Can spin networks describe a unit volume that is "sphere-like"? Lee Smolin's SciAm article "Atoms of Space and Time" seems to be describing unit volume and area in spin networks in terms of polygonal structures e.g. pyramids...

What exactly is 2D quantum gravity? Is it just a simplification of 3D quantum gravity i.e. to get results easier?

Are moduli in stringscape like metrics in general relativity because both determine the shape and size of spaces?

From http://arxiv.org/abs/hep-th/0203101, the number of degrees of freedom = ln of the dimension of the Hilbert space = number of bits of information, and if entropy = S, then e^S = number of independent quantum states compatible with macroscopic parameters => entropy is a measure of our...

Can I ask a related question here? Unruh's Law says that an observer will detect particles only at an accelerating state n temperature of surroundings proportional to acceleration. I thought particles and anti-particles annihilate and recreate in space constantly? Does that mean they are...

Can you give some further elaboration on what this means?

May I ask how the other particle (call it particle B) "picks" the opposite state? Is it just a matter of us assigning the opposite state to it after we measure the spin of particle A? Sorry, I'm being ignorant here.

How does LQG get rid of cosmological singularities in homogeneous models for e.g. Bianchi V? Any good references to papers? Is the Belinskii-Khalatnikov-Lifschitz scenario mostly used in analyzing quantum gravity solutions for cosmological singularities? Thanks for any help (am just a...

Try these:- 1) Manifolds at and beyond the limit of metrisability at arXiv:math.GT/9911249 2) http://www.math.auckland.ac.nz/~gauld/research/ (the file is labelled metrisability.pdf) both by David Gauld at University of Auckland Department of Mathematics. A mathematical physics prof...

Oops, didn't know that the Maurer-Cartan machinery does the trick. Some discussions on Maurer-Cartan forms at SPR :redface: Any other recommendations for an excellent book on Lie algebras that's not too hard for a physics student? (sorry if veering out of topic here)

Mmm, as far as I learnt, exterior calculus applies only to functions and forms to generate forms of higher rank. An arbitrary tensor is a product of an arbitrary number of forms and vectors. We use another type of calculus for tensors i.e. Lie derivatives, covariant derivatives. (I stand corrected)

Was trying to follow the construction by way of complex transformations of the Schwartzschild metric (in advanced Eddington-Finkelstein coordinates) through the null tetrad formalism in Ray D'Inverno's Introducing Einstein's Relativity. The result is supposed to be the Boyer-Lindquist form of...

Oops, sorry, yes, I made a lethal careless mistake! The equation I was referring to is d\omega^\mu=D^\mu_{\alpha\beta} \omega^\alpha \wedge \omega^\beta. (which at a glance, I saw the right-hand side wrongly as the wedge product of d\omega^\alpha and d\omega^\beta) Ok, so the above...