
Lost Causes of Theoretical Physics (2003) - scottlocklin
https://web.archive.org/web/20160209122140/http://www.mth.kcl.ac.uk/~streater/lostcauses.html
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evanb
There has been an enormous resurrection of the analytic bootstrap. Grep, for
example,
[https://www.icts.res.in/program/NUMSTRINGS2018/talks](https://www.icts.res.in/program/NUMSTRINGS2018/talks)
for bootstrap. The difference is the realization that the bootstrap equations
can be solved numerically and can be thought of as a way to test whether
certain conformal theories exist at all, rather than as a way to take you from
hardly-any-input-at-all to a complete description of the theory.

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soVeryTired
Can anyone explain Feynman path intergrals to a non-physicist? I'm guessing
there's a bit more to it than defining a measure on C[0, T] and lebesgue
integrating.

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qwerty456127
I'm not a physicist but as far as I know the key concept of the Everett
interpretation is that you can think of universe states as of vectors and
perform mathematical operations on them. IMHO giving up the ability to think
this way would be a tragic loss. Many other parts of the list would make a
huge pity to forget too.

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zakk
> Rigorous Feynman Path Integrals

It depends on how rigorous you want the treatment to be.

The whole machinery of Feynman diagrams is derived from Path Integrals and
Wick's Theorem, so they are rigorous, at least as rigorous as standard
perturbation theory using operatorial quantum mechanics.

A mathematical physicist won't be amused, though, that's correct. But I
wouldn't say that Path Integrals are less rigorous than the average technique
used in Theoretical Physics, and particularly in many-body theory.

~~~
evanb
There's been a lot of progress nonperturbatively defining quantum mechanics
and quantum field theory using resurgence lately. See, for example, the very
recent [https://arxiv.org/abs/1802.10441](https://arxiv.org/abs/1802.10441)

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dandare
Does it say Mach Principle is incorrect? That is good, as a non physicist I
could never wrap my head around the distant stars influencing anything.

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akvadrako
The distant stars are important because they make space flat. Remember that
general relativity says mass bends space, or more accurately is the same thing
as space.

So if _all_ the mass was nearby, space would bend inward around the current
point and it would fold in on itself - the universe would be like the inside
of a sphere.

Because the mass is distributed evenly at the largest scales, it instead
continues flatly in all directions.

~~~
posterboy
> the universe would be like the inside of a sphere.

The surface of which is "flat"? The interior surface, if that's the right
word. Like living on the Event Horizon of a black hole. So we don't and hardly
can know what's outside or inside or on the outside or inside.

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carlob
> Aspect, Dalibrand and Roger (1982)

Aspect, Dalibard and Roger (1982)

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rubidium
Grad school physics was/is your background I assume. I had the same thought
when reading.

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carlob
Yep, I was a graduate student in physics, but not at all in that field. The
reason why I recognize Dalibard's name even misspelled is because I was a
student in the same institution and I used to know several of his grad
students.

Little bit of trivia: he was 23 or 24 when he wrote that paper…

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hliyan
Not a physicist, but isn't "Bohmian Mechanics" (1) what's also known as "Pilot
Wave Theory", which is now gaining experimental support (2) ?

 _Clarke 's First Law: "When a distinguished but elderly scientist states that
something is possible, he is almost certainly right. When he states that
something is impossible, he is very probably wrong."_

1\.
[https://en.wikipedia.org/wiki/De_Broglie–Bohm_theory](https://en.wikipedia.org/wiki/De_Broglie–Bohm_theory)

2\. [https://www.quantamagazine.org/pilot-wave-theory-gains-
exper...](https://www.quantamagazine.org/pilot-wave-theory-gains-experimental-
support-20160516/)

~~~
whatshisface
Pilot waves, multiverse and Copenhagen are fundamentally ineligible for
experimental support, at least with respect to each other. They lead to the
same numbers, meaning than an experiment that agrees with one will also agree
with the others. It's something like trying to tell the difference between
2x=2y and x+2=y+2.

The "support" in the article is really just a physical system that obeys (as a
macroscopic approximation) something like pilot waves: "just like the
universe" if pilot waves are right, and "just like those silly nonlocalists"
if pilot waves aren't.

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John_KZ
While the current formulation details of the pilot wave theory doesn't allow
for new predictions, a better formulated one will. I strongly believe we'll
see the breakthrough in the coming 10-15 years. Quantum mechanics are
statistic predictions and it's about time we treat them as such.

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naasking
> While the current formulation details of the pilot wave theory doesn't allow
> for new predictions

Actually pilot wave theories do have new predictions, namely quantum non-
equilibrium. We just have no idea if we can actually design an experiment for
it.

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sgillen
The many worlds interpretation is just that, and INTERPRETATION, not a
predictive theory. The article seems really upset by that, but is it any
reason to label it a lost cause? I guess you can’t really study it or preform
experiments on it but that shouldn’t be any suprise for any interpretation of
quantum mechanics.

I might be missing something here...

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zombieprocesses
If a theory isn't predictive, it isn't falsifiable. If it isn't falsifiable,
then the theory isn't truly scientific.

This is a major issue/concern in advanced theoretical physics. Is it really
physics if you can't experiment or is it just mathematics?

The foundation of science is falsiability within the scientific method. It's
the core tenet.

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TheOtherHobbes
But you need to do a lot of speculative work before falsifiability becomes
possible. And that speculative work is going to involve groping around in the
dark being guided by mathematical logic (and a certain amount of politics,
fashion, and wishful thinking.)

Considering physics as if MWI could be true has the potential to lead to
mathematical elaboration and eventual falsifiability.

Considering physics as if there's no need to interpret QM because there's
nothing to interpret (because Copenhagen is the correct interpretation) is a
statement of faith, not rigour - because as a position, it's no more
falsifiable than MWI, or Bohm, or any of the other interpretations.

The point of mathematical physics is to generate _new_ falsifiable
predictions. It's still science, it's just embryonic proto-knowledge - which
is why it's called research, not teaching.

