Recent content by dreynaud

> Yes I agree. > Yes. The point is that the two guys live in the same geometry. GR establishes relation between geometry and material content; so the two guys sould also agree on this content on the basis of GR. > I precisely wanted to know if someone had read something on this question, but...

The article you've suggested is very interesting. However I think that the question remains : The vacuum is first set rlativelty to a "reference observer" such that : "This vacuum state has been fixed by requiring that a reference observer freely falling from innity detects no radiation". Then...

Thanks for your answer. I'm going to read the article you cite. I quickly add somme comments : - That a free falling observer doesn't experience any thermal radiation is a well based property discussed by Hawking in early 70s articles and Unruh, also explained by Kip Thorne in his book (that I...

It is known since Hawking that an observer "a rest" at some far distance of a black hole sees a thermal radiation emitted by the black hole. The mass of the black hole diminishes while it emmits the thermal flow of particles. For a free falling observer there is no thermal radiation. So, for...

Yes I know some things about decoherence. In the idealized case where density matrix is diagonal (after infinite time in the decoherence theory if I'm not wrong), the out state could then be written in term of field operators acting on the vaccum. So can we say that the field is collapsing ...

Note however, that as you showed, a finite Hilbert space is not realist. But whatever: If one accepts your argument (the properies you mentioned for the operator P are reasonable, your argument is ok on mathematical gounds, so I think it should be !), it then shows that probability operator...

In QM we have the postulate of measure giving rise to the notion of wave function collapse throught measurement. Is there an analog description of collapse in QFT (even an effective one) ? And what is then collapsing ? The field ? What would that mean ? I'm interested for references on the...

Yes. But why not : consider the two states of a two slits experiment. It forms a 2 dimensionnal hilbert space; It can also be written as a vector in the infinite-dimensional space of the eigenvector of the position operator for ex. (I hope I have understood your point).

Ok, we agree. There is an observable (operator) for X and not for the probability (this is simply contemplation of the theory). I'm perfectly ready to accept this, but I wanted to understand the reason that conduct to this. It seems that there exists in QM 2 "kinds" of 'measurable' quantity...

Ok we don't agree... Means in the 1960's ? I've got an old book of Louis de Broglie (who was at first a science historian) published in 1941 that says exactly what I said : the main motivation to go beyound Bohr's model was the prediction of the intensities I mentioned. Bohr's model (which is...

Yes I know. But the first success of the Quantum mechanics was to be able to predict the observed intensity of atoms' spetral rays whick is a direct chek of the probability of transitions. So probabilities are observed I think, not only calculated. Could we say that probabilities are not...

Good remark : so the operator should depends on something. Say a probability of transition. My point is that we effectively measure probabilities (of whatever is measurable, position, energy, momentum, transition...), so it should be an observable. no ?

Is probability a quantum observable ? I'd like to obtain an observable operator (self-adjoint, hermitian) with correct eignevalues (the probability). Have anyone heard of such an operator in QM ? And what about QFT ? Why is there no such operator in classical textbook ?

About "Decoherence" I said previously that Serge Reynaud participated to the experiment probing decoherence. I made a mistake : It was in fact Serge Haroche. Please see the article reporting the experience of observing "real-time" decoherence ...

Well, you have two questions : 1/ Are there any experiments showing that a wave function can collapse with an observer not present ? There are no reported experiment where there is no observer. The question itself is not consistent. (This sounds like a philosophical question about the status...