Recent content by Brage

Well consider that every state of every particle in the universe is already corrolated with every other state of every other particle in the universe. Then a local interaction is not an isolated event, but an event that gains you knowledge about which state of the universe you belong to. So its...

They use the same christoffel symbol, in image1 they have employed two different definitions for the covariant derivative and used substitution, it is not a definition for the Christoffel symbol. That being said, if you look at how they contract the raised index with the christoffel symbol in...

Oh of course I was using ##d(-t)=-dt##. Cheers for that!

Well ##T\partial_t |\psi>=\partial_{-t}T|\psi>## so then ##T\partial_t |\psi>=-\partial_{t}T|\psi>## correct?

I think there is quite a common misconception about the "splitting of universes". From Everett own work we referes to an object not being described by the wave funciton as a superposition of states, but rather that the object IS the superposition of all its states. That is to say each state is...

Hi, I have been trying to get my head around the effect of a time reversed hamiltonian ##H^B(t)=H(-t)=T^{-1}H^F T ## on a state ket ##|\psi>##, where ##H^F=H## is the regular hamiltonian for the system (energy associated with forward time translation) and ##H^B=H(-t)## is the time reversed...

I think the context they meant that they don't have any "speed" is to say that it is not that they are receeding further away from us THROUGH space, but rather that the amount of space between us and the clusters is increasing. Therefore photons traveling through this space get "streched"...

Yeah of course, I only assumed he was referring to the case of general relativity due to where the tread is placed and that he seems to be considering the contracted second Bianchi Identity from his orignial post.

Rasing an index is contracting this index with one of the inverse of the metric tensor. As the covariant derivative commutes with the metric it is more usual to write ##\nabla^{\mu}R_{\rho\mu}## as ##\nabla_{\mu}R^{\mu}_{\rho}##, but as the metric commutes with the covariant derivative...

ok yes I understand what you mean then!

Yes but the theory predicting observables does not mean observers are central to the theory, although I suppose you could argue in Everetts case any particle will itself be an observer. Cheers

If you are looking for an intuitive understanding of superposition you could always consider the vibration of some sting (like in a guitar) which can be represented as a sum of different weighted harmonics of the string. This could then be described as the vibration is a superposition of...

I am not too sure of this. As we are on the subject of many worlds, Hughe Everett's work (many worlds theorem) describes definite outcomes (wave function collapse) in terms of corrolation of states and as such no oberver is needed, and different observations would just be different corrolations...

I think it is not quite right to say that vacuum fluctuations are not physically real (which is what it seems to me you are saying), as a lot of effects are very precisely described by them. Take for instance Hawking radiation and the lambda shift (which was not predicted by the Dirac equation)...

I am not sure what you mean but if you look for example at the Einstein-Hilbert Wikipedia page you can get a definition for the stress-energy tensor in terms of the variation of the lagrangian matter density w.r.t your metric.