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Mathematical methods in classical mechanics, classical and quantum field theory, quantum mechanics, statistical mechanics, condensed matter, nuclear and atomic physics.

6 votes
5 answers
563 views

What happens to the solutions of a fourth-order boundary-value problem as you turn off the f...

Background Lagrangian mechanics on $\mathbb R^n$ is usually defined by picking a Lagrangian function $L: {\rm T}\mathbb R^n \to \mathbb R$, where ${\rm T}\mathbb R^n = \mathbb R^{2n}$ is the tangent …
Theo Johnson-Freyd's user avatar
10 votes
3 answers
728 views

What happens to Newtonian systems as the mass vanishes?

This question is closely related to another one I asked recently, and may be thought of as a warm-up to that one. Consider $\mathbb R^n$ with its usual metric, and pick a one-form $b$ and a function …
Theo Johnson-Freyd's user avatar
2 votes
2 answers
1k views

Is the Hessian of Hamilton's function positive-definite?

Background Consider an electron with mass $1$ moving in $\mathbb R^n$ in under the influence of a static electromagnetic field. Up to identifying vector fields with differential forms, Maxwell's equ …
Theo Johnson-Freyd's user avatar
7 votes
4 answers
638 views

Explicit bounds for the asymptotics of oscillatory integrals

Recall the following theorem (c.f. LC Evans, M Zworski, "Lectures on semiclassical analysis", Theorem 3.15, depending on the version): Theorem: Let $\varphi: \mathbb R^n \to \mathbb R$ be smooth and …
Theo Johnson-Freyd's user avatar
34 votes
4 answers
2k views

How is tropicalization like taking the classical limit?

There is a folk — I can't call it a theorem — "fact" that the mathematical relationship between Complex and Tropical geometry is analogous to the physical relationship between Quantum and Classical me …
Theo Johnson-Freyd's user avatar
8 votes
2 answers
543 views

Where can I learn about (the asymptotics of) Toeplitz operators?

Toeplitz operators provide a natural language with which to do geometric quantization. I don't want to really understand them, and I don't need them in full generality. I'm looking for some referenc …
Theo Johnson-Freyd's user avatar
7 votes
1 answer
500 views

Is the space of nondegenerate classical paths connected?

I have a fairly specific question. My intuition says the answer is "yes", but there is a natural generalizations in which I take out all the "physics", and then I think the answer is "no". Edit num …
Theo Johnson-Freyd's user avatar
2 votes
1 answer
538 views

What kind of uniqueness can I conclude for solutions to a simple functional equation?

I'm going to ask a very vague question, and then give specifics for the version I particularly care about. I'm interested in answers at all levels of vagueness. At the most vague version, I am in th …
Theo Johnson-Freyd's user avatar
6 votes
1 answer
408 views

Is there a theory of differential equations for smooth correspondences?

This question is very closely related to another one I just asked. The general question is to what extent there is a theory of differential equations for smooth correspondences (between a smooth mani …
Theo Johnson-Freyd's user avatar
6 votes
3 answers
449 views

Do there exist small neighborhoods in a classical mechanical system without pairs of focal p...

The question I will ask makes sense in much more generality, but I will leave the translation to the experts, since I'm only looking for a special case (and it would not surprise me if the answer does …
Theo Johnson-Freyd's user avatar
13 votes
1 answer
1k views

Which functions are Wiener-integrable?

I'm looking for either a few precise mathematical statements about Wiener integrals, or a reference where I can find them. Background The Wiener integral is an analytic tool to define certain "integ …
Theo Johnson-Freyd's user avatar
7 votes
1 answer
285 views

What are braided vertex algebras?

The notion of vertex algebra, like any reasonable algebraic notion, makes sense inside any (sufficiently linear) symmetric monoidal category. The standard pictures of the operator product, however, su …
Theo Johnson-Freyd's user avatar
37 votes
6 answers
4k views

Examples of applications of the Borel-Weil-Bott theorem?

In "Quantum field theory and the Jones polynomial" (Comm. Math. Phys. 1989 vol. 121 (3) pp. 351-399), Witten writes: A representation Ri of a group G should be seen as a quantum object. This repr …
Theo Johnson-Freyd's user avatar
24 votes
1 answer
589 views

Has the $E_8$-based generating function for squares numbers been proven?

In his 2004 paper Conformal Field Theory and Torsion Elements of the Bloch Group, Nahm explains a physical argument due to Kadem, Klassen, McCoy, and Melzer for the following remarkable identity. Let …
Theo Johnson-Freyd's user avatar
11 votes
1 answer
491 views

Is there a version of supersymmetry for homogeneous spaces?

The notion of "supersymmetry" that I am aware of proceeds as follows. One fixes a spacetime $\mathbb R^n$ and signature; I will write $\mathrm{SO}(n)$ for the corresponding group of orthogonal transf …
Theo Johnson-Freyd's user avatar

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