Recent content by eendavid

I might be interested in a job as a patent attorney (so if I understood correctly, you first apply for trainee patent attorney). I guess what I'm asking is: should one try to get a basic gist of IP law before applying?

Supposing that you have zero knowledge of IP law, what are the skills people are looking for in an interview? Maybe more specific: as a theoretical physicist, with no industry experience, is analytic insight and experience with publishing articles sufficient to get in?

That's right.

OK, I am sorry for the confusion. You are obviously right that dt is orthogonal to the hypersurfaces. The lapse and shift vectors turn up from decomposing (\frac{\partial}{\partial t})^a = N n^a + N^a (not what I wrote earlier). From this, one can find the usual form for the metric in terms of...

While you can find 3 independent vectors satisfying this, they simply do not span the space tangent to your hypersurface. Since h_{\mu\nu}n^\mu is 0, this h really behaves as a 3x3 metric on the hypersurfaces.

Yes, note more precisely that n^ah_{ab}=0 (and itex]v^av^bh_{ab}=v^av^bg_{ab}[/itex]). So this is really what you see as the induced metric: it gives the correct inner product for vectors tangent to the hypersurfaces (and it's not a metric on the 4D space, since there it is degenerate). On...

I mean, GR is not globally Lorentz invariant. Maybe, if we want SO(3,1) in the story, I shoud rephrase what I said. Let us describe GR with tetrads, thus introducing a new SO(3,1)~ SU(2)xSU(2) degree of freedom. This freedom has to do with the choice of tetrads, not with what people talk about...

The SU(2) indices of the Ashtekar variables are the SO(3) freedom that the triads have in a 3+1 formulation of general relativity. These are not related to diffeomorphisms, which act on the space indices (well it's a bit more complicated, but that's the idea).

make that at least 2.

I am not familiar with beyond-gravity results (as far as I can tell, the drawback is that one has to put matter in by hand), so I'd only like to comment on different ambitions for quantum gravity. String theory (also string field theory) needs a background (not necessary Minkowski), and as such...

I don't know anything about this. I wonder though. A conformal mapping is a mapping that conserves angles, while you ask a mapping that bends some angles 90° to 45° (and that maps curve to a point). That's impossible, not?

I too was referring to quantum gravity. o:) Of course it is difficult to forecast how theories would have evolved without string theory. To me it seems reasonable that LQG would've had a faster grow. At the moment string booms (mid-90's) LQG did have some results (which were negligible compared...

String theory has gained a lot of interest (and money), partly because of this claim. Seen in this context the analogy with end-of-19th-century physics fails. One should not be surprised that proponents of other approaches have a mixed feeling about this, and see it as a retreat. I don't see...

In Rovelli's book there is mention of the 'noncommutativity of the geometry' (last section of 6.7), where is argued that the area operators of intersecting surfaces do not commute. To me, this seems to imply that NCG is necessary for LQG (rather than a promising approach). Am I missing something?

A gauge transformation is a transformation of the fields which doesn't change the physical observables. An example is adding a constant to the electrostatic potential. Demanding that such a (global) gauge symmetry exists as a local symmetry has given importants hints for theoretical physics...