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

4 votes
1 answer
227 views

Computational trick used in QFT and the Jones Polynomial

Given a compact, simple Lie group $G$, and a compact, oriented three manifold $M$, we can consider the following smooth homotopy groups: $(C^\infty(M;G)/{\sim},\cdot )$: Here, $\sim$ is smooth …
David Roberts's user avatar
1 vote
0 answers
83 views

Characterization of the Subspace of Quasifree States of the CAR Algebra

Consider $\mathfrak U(\mathfrak H)$, the CAR algebra over a separable Hilbert space $\mathfrak H$. The states $E_{\mathfrak U}$ over this algebra are defined to be positive linear functionals of norm …
David Roberts's user avatar
2 votes
1 answer
272 views

Hessians on Kahler Manifolds

This is primarily a linear algebra question, but for motivation I want to state this question in its natural, global context. Whenever we have a non-relativistic quantum field theory (renormalized, o …
David Roberts's user avatar
2 votes
0 answers
79 views

Algebraic machinery for boundary conditions: may spectral data be "lifted" via the Toeplitz ...

Let $\tilde{\mathcal H}$ be a Hilbert space, and let $L(\tilde{\mathcal H})$ denote the corresponding space of linear operators. By fixing a basis, we can, via Fourier transform, identify an important …
David Roberts's user avatar
3 votes
1 answer
125 views

Classification of $2k$-vectors modulo orthogonal transformations

Consider the following chain $\{A_1,A_2,A_3,\cdots,A_{n}\}$ of orbit spaces of even-rank anti-symmetric tensors, where $$A_k:=\frac{\Lambda^{2k}(\mathbb{R}^{2n})}{e_{i_1}\wedge \cdots \wedge e_{i_{2k} …
David Roberts's user avatar
4 votes
1 answer
314 views

Spurious length-scale cutoff emerges in propagator defined in Costello's "Renormalization an...

In page 9 of the introductory chaper of Renormalization and Effective Field Theory (the introductory chapter is available free here), Kevin Costello defines a propagator $P$ for the Laplace operator $ …
David Roberts's user avatar
3 votes
Accepted

Why does the Bogolyubov transformation work? - In language of Clifford Algebras?

There is an elegant formulation of the Bogolyubov transformation in terms of Clifford algebras. Note that a quadratic Hamiltonian (noted by a hat), is a hermitian element of the representation of a Cl …
David Roberts's user avatar
4 votes
1 answer
503 views

Why does the Bogolyubov transformation work? - In language of Clifford Algebras?

Letting the standard Clifford algebra of dimension $2k$ be denoted by $Cl_{2k}$, let's denote the corresponding complex Clifford algebra via $$\mathbb{C}l_{2k}\equiv Cl_{2k}\otimes_{\mathbb{R}}\mathbb …
David Roberts's user avatar