Recent content by gnl

how can we say something like a multi-verse theory is or is not "probable"? don't we lack a definition of "probability of existence of another universe"? I think it's more honest to say "does not seem right to me".

OK, I see. Sounds a bit "fantastic" to me, in the sense that I see no convincing reason to find this theory more acceptable than any other I can come up with to explain time travel. Where is evidence?

I do not really understand this predeterminism... but I would like to. It does not make any sense to me as I understand it now.

1. Let us assume parallel universes exist. The moment I kill my father I get diverted to a new universe. Question: since I can think of infinite variations, do infinitely many universes exist - one for every variation I can imagine like killing my mother instead or my mother and someone else at...

What can I say? Angels and ministers of Grace, defend us.

1. Causality: the order of time-like separated events is not reversible for any observer. Different approach: what if I travel back in time and kill my father as a child? nobody ever gives a satisfactory answer to this. 2. the existence of parallel universes is not supported by any kind of...

I still cannot avoid thinking of all the paradoxa. I think the REAL question is: is causality a physical law? Should it be? I think so. I also think that even small violations of causality can lead to disaster. In other words, I think it would be very useful to look for rigorous physical...

I see. However, if mathematical consistency and physical reality are non necessarily the same, I suppose time travel can still be exluded on the basis of its unphysical nature. After all, this is done with Goedel's solutions of GR equations that involve closed time-like curves, time travel...

It depends on the amount of time you have. Mind you, one can find also excellent notes on the web for free. One example: http://www.lorentz.leidenuniv.nl/vanbaal/FTcourse.html

I think it over-simplifies things, and in the end of the day you don´t learn much. With Peskin and Schroeder plus Bjorken and Drell and Bailin and Love you certainly don´t need it.

I agree with slyboy, but I also suggest the excellent textbook by Bailin and Love. Don´t waste your time on Mandl and Shaw. The classic Bjorken and Drell is also a good choice for many parts. I don´t think one should follow one book only, but pick things here and there... Good hunting!

I have always had the suspect that time-machines belonged to the realm of crackpot theories. They never give a satisfactory answer to the fundamental question of causality (I believe a non-causal theory to be totally meaningless).

Qft Quantum Field Theory. The quantised theory of fields.

I could not agree more! Sakurai is a text all physicists should read. The best on QM.

I suspect it also necessary for you to realize that there is a lot of classical field theory in QFT. Vector fields are a perfectly classical notion. Electric and magnetic fields are examples. In relativistic field theories, you get 4-vectors (this tells you how they transform under Lorentz...