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

13 votes
0 answers
336 views

A modified Heisenberg uncertainty relation

Let $\psi\colon\mathbb R\to\mathbb C$, and set $$ F[\psi]:=\pi\ \frac{\displaystyle\int_{\mathbb R} |x|\;|\psi(x)|^2\,\mathrm dx}{\displaystyle\int_{\mathbb R}|\psi(x)|^2\,\mathrm dx}\frac{\displaysty …
AccidentalFourierTransform's user avatar
4 votes
0 answers
248 views

Chern-Simons and framing dependence$.$

I posted this question to physics.SE last week (cf. here), but it got not attention. I hope it is not too trivial to post it here. According to ref.1, the correlation functions of a Chern-Simons theo …
AccidentalFourierTransform's user avatar
6 votes

Maxwell equations as Euler-Lagrange equation without electromagnetic potential

Here is a very simple Lagrangian that yields the Maxwell equations upon variation, taken from this post (also by me) on physics.SE. The trick is to introduce Lagrange multipliers. Let \begin{equation} …
AccidentalFourierTransform's user avatar
20 votes
Accepted

What do physicists mean by a topological quantum gravity theory

Physicists here. The input for a physical theory is always some topological space and some structure (such as a metric) that depends on the specific context. The dynamics are invariant under the isome …
AccidentalFourierTransform's user avatar
5 votes

Non-commutativity of the d'alambert operator acting on the covariant derivative of a scalar ...

Use $$ [\nabla_\mu,\nabla_\nu]V^\rho=R_{\mu\nu}{}^{\rho\sigma} V_\sigma $$ to conclude that $$ \begin{aligned} {}[\nabla^\nu\nabla_\nu,\nabla_\mu]\phi&\overset{ \mathrm A}=\nabla^\nu[\nabla_\nu,\nabla …
AccidentalFourierTransform's user avatar
9 votes

Why is conformal invariance only possible for massless theories?

Note that the Schrödinger action, say in flat space-time, $$ S=\int\mathrm dx\ \psi^*\left(i\frac{\mathrm d}{\mathrm dt}+\frac{1}{2m}\nabla^2\right)\psi $$ has a length scale (mass) $m$, and yet it is …
AccidentalFourierTransform's user avatar
5 votes
0 answers
124 views

Modular $S$-matrix for an extended affine Lie algebra

This is a refinement of this old question of mine. In order to find an answer, I've been working my way through q-alg/9511026, which contains all the information I need. In this paper, the authors as …
AccidentalFourierTransform's user avatar
3 votes
Accepted

Graph of a Lie super algebra

See §15 in Dictionary on Lie Superalgebras, by L. Frappat, A. Sciarrino, P. Sorba. They define the Dynkin diagram of basic Lie superalgebras (i.e., those with an even nondegenerate invariant bilinear …
AccidentalFourierTransform's user avatar
4 votes
0 answers
137 views

Langlands dual and integrable representations

Assume I successfully classified the integrable representations of a certain semi-simple Lie group $G$. Given this information, what do I know about the integrable representations of $G^\vee$, the Lan …
AccidentalFourierTransform's user avatar
4 votes
0 answers
298 views

What is known about the projective representations of $\mathrm{SO}(n_1,n_2)$?

He${}$llo MO. Let $\mathrm{O}(n_1,n_2)$ be the pseudo-orthogonal group. I am interested in its (continuous, not necessarily unitary, finite-dimensional) irreducible projective representations, for ar …
AccidentalFourierTransform's user avatar