Recent content by haushofer

I like Zwiebach's QM book. Especially its coverage of linear algebra is nice.

I just bumped into this short note "Newtonian Gravity with a Retarded Potential", http://kirkmcd.princeton.edu/examples/retarded.pdf but haven't read it myself yet. It writes down the potential a la Lienard Wiechert and derives the resulting force from it. I'm not sure exactly how this...

I guess one should dive into post Newtonian expansions for this, but that's not my expertise; my world is (was) strictly Newtonian :P

I suspect that most people see it as a useful device to establish e.g. holography. To paraphrase my supervisor (an author in the list above): "I think SUSY will play a role akin to complex numbers in the sciences as a useful tool to do calculations". As someone who published about...

Thanks. You just shattered my worldview.

Welcome! Feel free to start new threads :)

There is a general-relativistic generalization of it due to Bekenstein, see https://en.wikipedia.org/wiki/Tensor%E2%80%93vector%E2%80%93scalar_gravity or https://pure.rug.nl/ws/portalfiles/portal/14540886/MONDtheory.pdf but it needs additional fields.

Euler hid them in his closet.

Ok, thanks, I'll have another look and compare it with the usual derivation involving invariants.

Thanks! But why ##\delta t_i \to 0##? This result of redshift also holds if we increase the time between two signals, right? What happens if the second light signal is send out/absorbed billions of years later such that ##\delta t_i = \mathcal{O}(10^9 \ yr)##?

Indeed. Bell turned metaphysics into physics. That's why I never understand physicists who claim the ontology of QM is a fruitless exercise because "they are all empirically indistinguishable". As a collegue of Bell put it (paraphrased): "Bell's theorem was not a victory of intellect, but of...

You don't need group theory; you just need a bit of tensor analysis. What I did in that section is just assume there is such an invariant Galilean interval, and apply the Galilei-transformations to both the supposed metric (components) and its inverse (components) and solve. If you've followed...

Dear all, I have a rather basic question about an equation in David Tong's lecture notes on cosmology; see http://www.damtp.cam.ac.uk/user/tong/cosmo.html My question is about eqn. 1.19 (page 14), in which the cosmological redshift is derived. It's not about the physics, but about some basic...

Just a quick reply: in https://research.rug.nl/en/publications/newton-cartan-gravity-revisited section 2.8 I treat the Galilean "spacetime interval". Maybe that helps.

As Peter points out, the "standard approach" (afaik) is to treat GR as the gauge theory of the Poincaré algebra (i.e. the algebra describing the full isometry group of the vacuum) and impose constraints. These constraints eliminate unwanting transformations (the local translations) directly, and...