

P=NP Problem Linked To The Quantum Nature Of The Universe - kentuckyfc
https://medium.com/the-physics-arxiv-blog/7ef5eea6fd7a

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danpalmer
I wonder then how this reconciles with the theories that the universe is in
fact being simulated in a computer.

It sounds like a crazy theory, and quite possibly is, but it's a thought
experiment, or at least an idea that I've seen physicists come back to time
and time again. Apparently it's a distinct possibility, and would actually fit
very well with a few recent discoveries about the nature of fundamental laws.
(Note I'm writing this from a layman's point of view, I know very little about
this subject.)

This discovery, if true, might imply that, if the universe is being simulated
in a computer, it might be a P≠NP might be a fundamental law of the meta-
universe, or a property of the computer itself, maybe even an optimisation,
and that over a certain size of object, it stops calculating quantum states.

This link might not exist, I might just be failing to understand the theories
involved, but I find it an interesting thing to think about nonetheless.

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robitor
I don't understand the connection made here, because calculating the quantum
state is NP-hard and is very time consuming, the object cannot exist in the
universe? How is that preventing the macroscopic system from existing? How
does the complexity class have anything to do with the real world?

For example, a shortest path problem in the real world does not have any use
for complexity theory: [http://www.johnmurray.io/log/2012/07/10/Real-World-
Shortest-...](http://www.johnmurray.io/log/2012/07/10/Real-World-Shortest-
Path.md)

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Houshalter
This strikes me as completely wrong. Who is to say there is an upper limit on
how big the computer running the universe can be, or that it has to be Turing
complete?

And why on Earth would that imply the laws of physics would work differently
at different scales. "Scale" is just an abstraction we use to make sense of
things, not a fundamental property of the universe (so far as I know.) If you
zoom out of Conway's game of life enough, everything looks completely
different as if it was operating by a different set of rules.

