Quantum Mechanics Prior To The Big Bang

[Dryson]

Are we able to apply Quantum Mechanics to a Universe Prior to the Big Bang? Or would such mechanics require an entirely new set of formulas?

 

[StevieTNZ]

Would a universe even exist prior to the Big Bang? (Maybe so in a Many-World's interpretation of QM, but not sure.)

 

[phinds]

Are we able to apply Quantum Mechanics to a Universe Prior to the Big Bang? Or would such mechanics require an entirely new set of formulas?

Since there is no testable theory that posits a time before the big bang, you can pretty much make up whatever answer you like, since it can't be tested. Of course, it isn't physics, but ...

 

[atyy]

At present, we don't even know if we can apply quantum mechanics very near the big bang, because our current theory of quantum gravity fails when the spacetime curvature is very high. You can ask in the BTSM forum about the LQC bounce if you like.

 

[Dryson]

quantum gravity fails when the spacetime curvature is very high

How does Quantum Gravity fail when spacetime curvature is very high? It sounds to me like a plane that is flying straight up and then stalls.

 

[atyy]

quantum gravity fails when the spacetime curvature is very high

How does Quantum Gravity fail when spacetime curvature is very high? It sounds to me like a plane that is flying straight up and then stalls.

The failure is pretty much the same as that of quantum electrodynamics. For quantum gravity and quantum electrodynamics to make sense, as we currently understand them, we need to do something equivalent to putting the theory in a large but finite box, and finely discretizing the theory. We only do experiments at very low energies and long wavelengths compared to the discretization, so the discretization doesn't matter, and the theories make good predictions. However, since the theories are discretized, this means they don't make sense if we probe very finely, ie. if we can probe very high energies or high curvatures.

 

[bhobba]

Are we able to apply Quantum Mechanics to a Universe Prior to the Big Bang? Or would such mechanics require an entirely new set of formulas?

Sure we can - see for example eternal inflation, and the bit on quantum fluctuations of the inflation field:
http://en.wikipedia.org/wiki/Eternal_inflation#Quantum_fluctuations_of_the_inflation_field

Thanks
Bill

 

[bhobba]

How does Quantum Gravity fail when spacetime curvature is very high? It sounds to me like a plane that is flying straight up and then stalls.

Its because of the infinities that plague Quantum Field Theory in general.

To tame those something called Effective Field Theory is required - at least that's the modern view the great physicist Wilson got a Nobel prize for sorting out - its an outgrowth of trying to understand what is called renormalisation. That paradigm is the best way to view quantum gravity:
http://arxiv.org/abs/1209.3511

Thanks
Bill