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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?

#11

Post by bcbrown »

An interesting assertion. I don't think it's valid to object that this is just about hard-to-solve equations. As I understand the article, this is the argument:

1) It's not possible to directly observe a macroscopic quantum object. This is because the act of observation collapses the wave function.

2) It's possible in theory to describe macroscopic quantum objects in the solutions to Schrodinger's equation

3) That solution for macroscopic systems is NP-hard

4) A physical theory that can neither be observed nor modeled is "nothing more than [a] nontestable empty [abstraction]"

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

#12

Post by raverbashing »

jjgreen wrote: post #2

The Navier-Stokes equations are also hard to solve, that does not stop fluids from obeying them.

I agree

For those who never saw the Navier-Stokes equation: http://en.wikipedia.org/wiki/Navier_Stokes#Derivation_and_de...

That's it. It looks simple but it involves Tensor math.

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

#13

Post by swombat »

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…

Unless, of course, our entire reality is running on a very powerful, but not infinitely powerful computer, and the Great Programmers in the Sky decided to cheat by putting in a hack that cuts off quantum behaviour at a larger scale...

Unlikely, but cute...

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

#14

Post by pndmnm »

Interesting and semi-related: http://www.opticsinfobase.org/oe/abstract.cfm?id=140598

Essentially, solving the traveling salesman problem in quadratic time using photon interference -- however, since the photons scale up as N^N, the Schwarzschild radius of the effect means it's not observable in less than exponential time.

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

#16

Post by tomp »

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 claim is wrong - I'm just saying that the explanation in the article is severely lacking/logically inconsistent.

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

#17

Post by bcbrown »

dllthomas wrote: post #7

"Nobody knows why we don’t observe these kinds of strange superpositions in the macroscopic world." Yeah, why can't we observe processes that rely on lack of observation?

We can observe processes that rely on lack of observation in the microscopic world. Look up the one-slit and two-slit experiments[0]. In the two-slit experiment, we don't observe which slit the photon takes, but we can observe the interference pattern on the screen.

The two-slit experiment works with photons, but not with bullets, or cars, or baseballs.

[0]: http://en.wikipedia.org/wiki/Two_slit_experiment

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

#18

Post by bcbrown »

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…

If something can neither be modeled nor observed, in what sense does it exist?

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

#19

Post by yid »

bcbrown wrote: post #18
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…

If something can neither be modeled nor observed, in what sense does it exist?

What does modeling have to do with observability?

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

#20

Post by cstross »

swombat wrote: post #13
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…

Unless, of course, our entire reality is running on a very powerful, but not infinitely powerful computer, and the Great Programmers in the Sky decided to cheat by putting in a hack that cuts off quantum behaviour at a larger scale... Unlikely, but cute...

Or

The granularity of the simulation of our reality is the Planck length. This constraint does not apply to the real, underlying, reality within which our simulation is embedded.

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