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Macroscopic quantum objects cannot exist if P ≠ NP?

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Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#41

Post by JulianMorrison »

trhway wrote: post #36
JulianMorrison wrote: post #33

Earlier quoted context omitted.

Box closed: two cats, one scientist. Box opened: two cats, two scientists, each sees one cat. Entangling yourself with the superposition pulls you into it.

>Entangling yourself with the superposition pulls you into it. following that logic and taking cat as the observer, Mr.Cat PhD, the superposition is that doubles the number of cats (and PhD's :). Yet it works in the other direction - entangling a cat (a macro-object with macro-state) with superposition had already destroyed the superposition well before box is opened. >> it can't see the superposition because it is i…

The cat is pulled into the superposition by interacting with the results of the detector and the poison vial. There are two cats from the "outside", but from each cat's perspective it sees only a single "random" outcome. Superpositions aren't destroyed - you are subsumed within them.

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#42

Post by scott_s »

IanCal wrote: post #39
raverbashing wrote: post #6

I'm not buying it 1 - P=NP is a mathematical problem. It has nothing to do with Physics. Physics has to do with Mathematics but one should be very careful when extrapolating (range, constraints, etc). 2 - Nature has no problem whatsoever solving complicated equations. Our mathematical models are the ones who suffer to model simple everyday stuff in Physics. Turbulence and Navier-Stokes equations, electromagnetic prop…

With 2, are you saying there are situations in nature that can solve NP-hard problems in polynomial time? Because if so, we could just use those to solve our hard problems and therefore P=NP. P=NP is not just statement about difficult problems or big equations, it's a very particular class of problems.

There are situations in nature where our models are NP-hard. Whether or not this is the same as saying that nature itself performs those computations is, I think, tied into the question of whether or not our Universe is a simulation.

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#43

Post by trhway »

denim_chicken wrote: post #22
raverbashing wrote: post #6

I'm not buying it 1 - P=NP is a mathematical problem. It has nothing to do with Physics. Physics has to do with Mathematics but one should be very careful when extrapolating (range, constraints, etc). 2 - Nature has no problem whatsoever solving complicated equations. Our mathematical models are the ones who suffer to model simple everyday stuff in Physics. Turbulence and Navier-Stokes equations, electromagnetic prop…

There is no evidence that nature can globally solve NP-hard problems. At best, nature finds locally optimum solutions to these problems.

>There is no evidence that nature can globally solve NP-hard problems.

There is no evidence that nature has NP-hard problems. All the nature is built on local interactions - thus the finite speed of any interactions in the nature.

Note: the only example of non-local optimization (specifically maximizing entropy over time-space existence path of a living object vs. that would be an entropy change associated with the equivalent amount of non-living matter in similar environment) is the life itself.

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#44

Post by PeterisP »

Strilanc wrote: post #24

I hope Scott Aaronson blogs about this article, because it espouses several of the wrong-facts he complains about and then cites him . - Limitations on computers within physics are not limitations on physics itself . Analogously, you can simulate system so simple that a computer can't be made in them without your computer unmaking itself. Relevant: xkcd.com/505 - We do understand why we don't observe superpositions.…

An interesting point is that limitations on math (i.e., things that would be true regardless of the details of the physical world) would put limitations on any physics simulations - including hypothetical physics simulations done by someone outside of our universe with potentially different physical limitations.

So the point of the article is something like - if phenomenon-X can't be simulated by anyone, no matter how good their computers become; and if our universe is a simulation (which is a possibility), then our universe won't contain phenomenon-X.

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#45

Post by mikeash »

SnacksOnAPlane wrote: post #27
tomp wrote: post #16

Wait what? What this article is arguing is totally absurd - just because we can't model certain physical objects, they cannot exist?! That's like saying that since we can't model three gravitational objects interacting (i.e. the numerical solutions diverge, therefore to properly model the system, we would require increasing amounts of memory and time), therefore they cannot exist. I'm not saying that the physical cla…

I'm a simulationist. I believe that the universe we're experiencing is a simulation made by a far-advanced civilization. So in my reality, if something can't be modeled, it can't exist. Not saying that this is the truth, just the way I choose to understand things.

What says that the universe containing our simulation is unable to solve NP problems in polynomial time?

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#46

Post by baddox »

raverbashing wrote: post #6

I'm not buying it 1 - P=NP is a mathematical problem. It has nothing to do with Physics. Physics has to do with Mathematics but one should be very careful when extrapolating (range, constraints, etc). 2 - Nature has no problem whatsoever solving complicated equations. Our mathematical models are the ones who suffer to model simple everyday stuff in Physics. Turbulence and Navier-Stokes equations, electromagnetic prop…

> 1 - P=NP is a mathematical problem. It has nothing to do with Physics.

I don't know if I accept that, although it's unclear what exact definitions you're using for those terms. P=NP makes very real claims about the abilities of real physical objects like Turing machines. It's obviously about math as well, but I don't see how that precludes it from being about physical qualities of physical systems.

> 2 - Nature has no problem whatsoever solving complicated equations.

Solving some complicated equations, no doubt. But I'm not aware of any evidence suggesting that nature can easily solve all complicated equations.

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#47

Post by tomp »

SnacksOnAPlane wrote: post #27
tomp wrote: post #16

Wait what? What this article is arguing is totally absurd - just because we can't model certain physical objects, they cannot exist?! That's like saying that since we can't model three gravitational objects interacting (i.e. the numerical solutions diverge, therefore to properly model the system, we would require increasing amounts of memory and time), therefore they cannot exist. I'm not saying that the physical cla…

I'm a simulationist. I believe that the universe we're experiencing is a simulation made by a far-advanced civilization. So in my reality, if something can't be modeled, it can't exist. Not saying that this is the truth, just the way I choose to understand things.

Still, until your belief is able to make physical predictions more accurate than other physical theories, it's just that - a belief, which has absolutely no physical validity.

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#48

Post by mdxn »

SnacksOnAPlane wrote: post #27
tomp wrote: post #16

Wait what? What this article is arguing is totally absurd - just because we can't model certain physical objects, they cannot exist?! That's like saying that since we can't model three gravitational objects interacting (i.e. the numerical solutions diverge, therefore to properly model the system, we would require increasing amounts of memory and time), therefore they cannot exist. I'm not saying that the physical cla…

I'm a simulationist. I believe that the universe we're experiencing is a simulation made by a far-advanced civilization. So in my reality, if something can't be modeled, it can't exist. Not saying that this is the truth, just the way I choose to understand things.

I think you would have to be assuming that the far-advanced civilization's simulator has the same complexity as the models of computation we can construct. I think that's a huge leap to make. We might not be able to model something due to issues with, let's say, Turing decidability. Unlike us, the advanced civilization's might be able to because their constructable models of computation are strictly more powerful.

Re: Macroscopic quantum objects cannot exist if P ≠ NP?

#49

Post by trhway »

JulianMorrison wrote: post #41
trhway wrote: post #36

Earlier quoted context omitted.

>Entangling yourself with the superposition pulls you into it. following that logic and taking cat as the observer, Mr.Cat PhD, the superposition is that doubles the number of cats (and PhD's :). Yet it works in the other direction - entangling a cat (a macro-object with macro-state) with superposition had already destroyed the superposition well before box is opened. >> it can't see the superposition because it is i…

The cat is pulled into the superposition by interacting with the results of the detector and the poison vial. There are two cats from the "outside", but from each cat's perspective it sees only a single "random" outcome. Superpositions aren't destroyed - you are subsumed within them.

>There are two cats from the "outside", but from each cat's perspective it sees only a single "random" outcome.

in a given Universe there is only one cat. A human observer just doesn't know what the state of the cat in his Universe. The cat knows.

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