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Wild guessing from someone who has no background in physics: 1. Simulating QM-level events is NP-complete. 2.Assuming P=/=NP, a machine that simulates a volum
by yakult 11y ago
Wild guessing from someone who has no background in physics:
1. Simulating QM-level events is NP-complete.
2.Assuming P=/=NP, a machine that simulates a volume of size X in QM-correct terms must be exponentially larger than X.
3. This includes X itself.
4. Therefore, the universe is taking sweeping shortcuts that look like classical mechanics at large scale. These are not 'our' computational shortcuts, they're actually how things work at a fundamental level.
5. ...maybe if we build a big enough quantum computer we can overflow the universe's buffer.
- spacehome 11y agoYou're missing step 0, which is assuming that our universe is a simulation. Also, you're making a lot of assumptions about the laws of physics and what is computationally feasible in the universe that that computer is running in.
- yakult 11y agoI'm not assuming simulation. It's more of "if the universe can pack something that can predict the outcome of an NP-complete system (that is, the universe itself) in real-time into a relatively very tiny space, then either it's cheating or P=NP." As for the assumptions, I agree. Hence it's wild guessing.
- spacehome 11y agoThen I misunderstood originally. If you're not assuming the universe is simulated and is instead "fundamental" (whatever that means), then who are you to put limits on its processing power?' I think you have a level-confusion here - the universe isn't packing computational machinery into itself. Remember that space-time is a part of this universe. If something is computing our universe, it has to hold the representation of space-time, too. The computation machinery isn't in here with us.
- yakult 11y agoIf 'fundamental' stuff gets to break P=/= NP, then I don't see why we can't do it in a computer, if only by aping the design. But then P=NP and things get weird.
- spacehome 11y agoI'm not sure why you keep mentioning NP and P. A problem being exponential doesn't mean it can't be computed. Maybe the universe does the calculations the hard way.
- ingenter 11y ago> 5. ...maybe if we build a big enough quantum computer we can overflow the universe's buffer. Except black holes are a thing.
- yakult 11y agoDepends on how it's optimized. If a star gets sucked into a black hole but nobody sees it, does it truly make hawking radiation? (Next stop: solipsism.)
- eru 11y ago> 1. Simulating QM-level events is NP-complete. Unlikely. Check out "Can NP-complete problems be solved efficiently in the physical universe?" (http://www.scottaaronson.com/papers/npcomplete.pdf http://www.scottaaronson.com/papers/npcomplete.pdf) and "BQP and the Polynomial Hierarchy" (http://www.scottaaronson.com/papers/bqpph.pdf http://www.scottaaronson.com/papers/bqpph.pdf). There's, of course, also Wikipedia ( https://en.wikipedia.org/wiki/BQP https://en.wikipedia.org/wiki/BQP).
- FrankenPC 11y agoP=NP. We just can't read the meta-meta-rules surrounding QM yet.