B Big Crunch, Big Bang and information loss

[kimbyd]

Well now that that is cleared up.

If I were to go back to the big bang (just a moment after) when the state of the universe at that point is essentially calculable (say at some super hot point that is yet too hot for matter to exist yet) and assign a value to how much information was contained in this universe at that moment, then move forward in time until precipitation of matter occurred, and assign a value then to the quantity of information in the universe at that moment, and compared the two, what would I see? Would I see an increase in the information, a decrease, or would it have remained the same.

Depends a bit upon what you mean by information.

If by information you mean the full configuration of the wavefunction of the universe, then as long as the laws of physics are unitary the two points in time necessarily contain the exact same amount of information. This means that if you had the full state at the early time, you could calculate the late time knowing the laws of physics. If you had the full state at the late time, you could calculate the early time.

Intuitively I feel that the information in the system is maintained and doesn't increase or decrease, even with the change in state, but I can't prove that. Where do I turn to prove or disprove this?

It comes down to whether or not the laws of physics are unitary.

 

[BernieM]

Depends a bit upon what you mean by information.

If by information you mean the full configuration of the wavefunction of the universe, then as long as the laws of physics are unitary the two points in time necessarily contain the exact same amount of information. This means that if you had the full state at the early time, you could calculate the late time knowing the laws of physics. If you had the full state at the late time, you could calculate the early time.It comes down to whether or not the laws of physics are unitary.

By information, I mean all the relevant data and conditions regarding a particle that would provide me a clear enough picture that I could solve that particles prior or subsequent motion, action, interaction, and nature with certainty.

I'm guessing that proving if the laws of physics are unitary, or not, is probably not going to be able to be determined in this thread, nor by anyone in the near future, right?

 

[kimbyd]

By information, I mean all the relevant data and conditions regarding a particle that would provide me a clear enough picture that I could solve that particles prior or subsequent motion, action, interaction, and nature with certainty.

Yes, that's more or less the definition I assumed.

I'm guessing that proving if the laws of physics are unitary, or not, is probably not going to be able to be determined in this thread, nor by anyone in the near future, right?

Correct. Unitarity is currently unknown, though many physicists suggest the fundamental laws must be unitary to have a sensible notion of causality. I gave an overview of what current physical laws are/aren't unitary in post #13 of this thread.

 

[jerromyjon]

I'd say way back when all the forces were unified would be the most likely bet at having a coherent picture of things, after gravity separated you get into what we have now, spin foams and such to deal with...

 

[BernieM]

I think I have the answer I asked for, thank you everyone.

 

[PeterKinnon]

"What I am trying to get at is if there really is any new information being generated in the universe, or if the entire cycle of the universe, including a potential future big crunch or big whimper wasn't already predetermined at the moment the big bang came into existence or 'occured.'"

So were the works of Shakespeare predetermined at the "big bang"?

The notion that information simply "crystallizes out" as the universe evolves is seductive but our observation that much of the machinery of nature is essentially probabilistic really rules it out.

Furthermore we can safely assert that information is not conserved since simply burning a CD destroys the all extrinsic information impressed upon in as well as most of the intrinsic information inherent in its molecular structure.Reference https://www.physicsforums.com/threads/big-crunch-big-bang-and-information-loss.919985/

 

[PeterDonis]

we can safely assert that information is not conserved since simply burning a CD destroys the all extrinsic information impressed upon in as well as most of the intrinsic information inherent in its molecular structure.

No, it doesn't. It just transfers the information to a different physical form. In principle, if quantum unitarity is correct, you could take the combustion products, analyze them, and compute all of the bits of information in the CD.