
Computational solution to quantum foundational problems - frisco
http://arxiv.org/abs/1403.7686
======
wolfgke
Scott Aaronson has commented on the paper; he considers it as garbage:

>
> [http://www.scottaaronson.com/blog/?p=1767#comment-103591](http://www.scottaaronson.com/blog/?p=1767#comment-103591)

Also look at the update at the beginning of
[http://www.scottaaronson.com/blog/?p=1767](http://www.scottaaronson.com/blog/?p=1767)

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madlag
Does somebody know of good papers about potential links between computation
complexity and why we do not observe large scale quantum behaviours ? As a
basic computer guy, I have always suspected that the large computer that is
running our universe does not have the resources to handle quantum
entanglement on a large number of particules, and has to fallback to some
classical approximation to be able to run the full simulation in real time ;-)

~~~
kremlin
why would it have to run it in 'real time'? what's the difference between this
universe being simulated by a very slow computer in the super-verse, vs being
simulated by a very fast computer in the super-verse? for us, I'd argue
there's no difference at all.

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maxerickson
Not always a fan of linking xkcd, but:

[http://xkcd.com/505/](http://xkcd.com/505/)

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chm
If someone's interested in a hard problem: design a density functional that's
exact with regards to strong correlation and you have my respect.

~~~
selimthegrim
It's instructive to remember at this point that Feynman used to call the
exchange-correlation energy "the stupidity energy" out of frustration. Many
Bothans died to give us PBE and B3LYP (at least it seems like it)

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chm
I actually never read that quote before, thanks. I'm a 1st year M. Sc. student
in a theoretical chemistry group. Although most members in the group do DFT, I
don't. My knowledge of the literature extends to some Perdew, Yang, HK and KS.

~~~
selimthegrim
What do you do then? H-F? In any case, do not just stick to DFT. I can't
emphasize enough how essential a book like Negele and Orland is to make
yourself useful in dealing with strongly correlated systems -- running codes
on these things is going to fail badly in terms of results deliverables useful
to experimentalists or for further theory unless you can do some model
building yourself. Way too many of these groups turn out people whose only
skill is running ABINIT or VASP or QUANTUM-ESPRESSO or maybe writing some
multi-threaded FORTRAN if they're lucky (shudder). Endeavor to make contact
with developments in modern condensed matter theory (it doesn't have to be
holography or AdS or anything that hardcore, just get used to the idea of a
field as something other than what a plow goes into)

~~~
chm
The project I was assigned requires only Hückel level theory, for the moment.
I'm concerned with molecular electronics, specifically trying to use CAPs
(complex absorbing potentials) to model conduction through aromatic molecules.

Thanks for the recommendation. The group I'm in is definitely focused on
method development. Calculations are mostly done on atoms and diatomic
molecules to benchmark the functionals.

~~~
selimthegrim
You may want to have a look at some of Jorge Hirsch's papers on complex
aromatics and ring currents. The guy is a bit of crackpot on
superconductivity, but what he says on aromatics might be of interest to you.

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gus_massa
I´ll repeat one of my comments in a previous submittion of the same paper:

There are some experiments where it’s easy to see quantum effects in “big”
things. There are experiments that show explicitly the wave behavior of helium
atoms (they have like 2 electrons and 12 quarks, and a lot of gluons, they are
not a single particle)
[http://en.wikipedia.org/wiki/Helium_atom_scattering](http://en.wikipedia.org/wiki/Helium_atom_scattering)
. I think there are bigger examples, but I should google a little to find
them.

Also, the superconductivity and superfluity effects are due to quantum
mechanics effects (a lot of properties of solids only can be explained
correctly using quantum mechanics, but they are not so evident).

There is more hand waving that a proof here. Obligatory Xkcd:
[http://xkcd.com/1240/](http://xkcd.com/1240/)

~~~
troymc
Don't forget the obligatory Wikipedia article:
[https://en.wikipedia.org/wiki/Macroscopic_quantum_phenomena](https://en.wikipedia.org/wiki/Macroscopic_quantum_phenomena)

