Saturday, November 24, 2012

Some more philosophical reflection on Relativity and Quantum Theory

     I'm reading a book on quantum stuff that said the the EPR paper said we have to choose between "realism"(that there are a definite states determining quantum objects prior to measurements) and "separability"(that states of separated points cannot instantly affect one another).  The book said that most scientists reject realism.  It seems to me that we are forced to reject both of them.  This is so obvious to me I don't see how anyone can think differently.  What am I missing?  The states of an entangled system exist in probability functions until they are collapsed by some measurement(that ends realism), the measurement of one side of an entangled pair changes the probabilities for the other side(this defeats separation). 
     Einstein was clearly convinced that quantum theory violated separability, which upset his field theory notions, and then spent the last decades of his life trying to rescue separability and failing.  It seems an interesting historical accident that quantum field theory arises from making quantum theory obey special relativity(Dirac Equation).  If Einstein had not derived the field equations for GENERAL relativity later on, would the current theory of gravity be entirely a quantum one? Is Einstein's General Relativity in some way a block?  Well, the problem is that General Relativity has too many confirming observations to be dismissed(time and length contraction, bending light, black holes, lensing, and the list goes on and on) as a framework.  So there is now no logical way to get around it. 
      But if Einstein had only done special relativity, what would physicists make of gravity now?  Would they be puzzled by the fact that gravity doesn't fit in with quantum theory?  Or would someone else have come up with General Relativity as a generalization of special relativity?

Friday, November 16, 2012

The Poincare Group

     The Poincare Group is the group that leaves invariant the interval in Minkowski spacetime.  It is the 'semidirect' product of translations in R^3 and 'boosts' written in terms of Lorentz transformations.  In quantum field theory we have to have our Lagrangian satisfy the symmetries given by this group if we're going to satisfy Special Relativity. 
     It's interesting to think about how we have to satisfy Special Relativity in a theory that includes entanglement. 

Strange Underlinings

I evidently pushed a button so that some of the phrases I typed are underlined and connected to advertisements.   Well, anyone can do anything they want on my blog, but I hope they are comfortable with what I write on it.  I mean, you know, like Chik-Fila or however you spell, it should know that I think homosexuality is a good thing, probably better than heterosexuality since homosexual activity doesn't run the risk of unwanted pregnancy.  Actually, wasn't there a movie where Arnold Schwarzenegger got pregnant?