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

12 votes
Accepted

Question on Lorentzian geometry

The signature convention $(−,+,\cdots,+)$ is more commonly used in General Relativity and Lorentzian geometry because of the desire among their practicioners to make a closer parallel to Riemannian ge …
Pedro Lauridsen Ribeiro's user avatar
26 votes

Who says understanding physics helps mathematicians? (A reference request) [Take the word "w...

Quoting the first two paragraphs of V. I. Arnol'd, On teaching mathematics, Uspekhi Mat. Nauk 53 (1998) 229-234, translated to English in Russian Math. Surveys 53 (1998) 229-236 (a transcription may a …
1 vote

Distinguishable under manifold topology but indistinguishable under the Alexandrov topology

What you seem (to me) to be asking is under which conditions on a Lorentzian manifold its Alexandrov topology not even $T_0$. If that is the case, then it is easy to see that if $(M,g)$ is not chronol …
Pedro Lauridsen Ribeiro's user avatar
5 votes
Accepted

Wick product of free fields and wave front sets in the sense of Lars Hörmander

The answer to both questions is no. This is due to two facts: The Klein-Gordon two-point distribution $\omega_2(x,y)=\langle\Omega,\phi(x)\phi(y)\Omega\rangle$ in $\mathbb{R}^4$, where $\Omega_1=\Ome …
Pedro Lauridsen Ribeiro's user avatar
26 votes
Accepted

Hilbert's sixth problem and QFT description

The reason is that there is no mathematically rigorous construction of any interacting quantum field theory in four space-time dimensions to this date. Because of that, one has not been able so far to …
Pedro Lauridsen Ribeiro's user avatar
21 votes
Accepted

QFT and mathematical rigor

As Abdelmalek Abdesselam pointed in his comment to the OP, the axiomatic approach to QFT is rather concerned with answering the question "what is a quantum field?". This is stated right at the Preface …
Pedro Lauridsen Ribeiro's user avatar
16 votes
Accepted

Rigorous construction of fermionic field theory?

There is the construction of the C${}^*\!$-algebra of canonical anticommutation relations (CAR's), which is actually somewhat easier than the construction of free bosonic fields: given any complex pre …
Pedro Lauridsen Ribeiro's user avatar
9 votes
Accepted

Initial conditions in the Klein-Gordon equation

One must remark that derivatives in Sobolev spaces are usually taken in the sense of distributions: given $k\in\mathbb{N}_0=\{0,1,2,\ldots\}$, $H^k(\mathbb{R}^n)$ is the space of tempered distribution …
Pedro Lauridsen Ribeiro's user avatar
8 votes

Topology on Minkowski space $\mathbb{R}^{4}$ and Lorentz invariant measure

Judging by your notation, I reckon you are getting the background for your questions from the Appendix to Section IX.8 of the book by M. Reed and B. Simon, Methods of Modern Mathematical Physics II: F …
Pedro Lauridsen Ribeiro's user avatar
12 votes

Why does Riesz's Representation Theorem apply in quantum mechanics?

$\DeclareMathOperator\Ann{Ann}\DeclareMathOperator\Tr{Tr}$My answer is somewhat complementary to Nik Weaver's, and admitedly more focused on Question 2 since I have nothing more to add to the latter r …
Pedro Lauridsen Ribeiro's user avatar
8 votes
Accepted

Hamilton equations for Classical Field Theory

There is a fundamental misunderstanding in your translation of Hamilton's formalism to classical field theory, which pertains to the proper identification of dynamical variables. In classical mechanic …
Pedro Lauridsen Ribeiro's user avatar
4 votes

Quantum fields and infinite tensor products

The "infinite tensor product" picture may be useful as a sort of concrete image of the state space of a quantum field theory, but in practice is rarely used because of the technical difficulties it br …
Pedro Lauridsen Ribeiro's user avatar
4 votes

Reference request for a treatment of Schwinger–Dyson equations

In the formulation of QFT using formal functional integrals, as mentioned by Igor in his answer, the Schwinger-Dyson equation becomes an infinite-dimensional differential equation for the partition fu …
Pedro Lauridsen Ribeiro's user avatar
3 votes
Accepted

$C^*$ algebras and states

If you want a criterion which is not tautological, that is, beyond the very definition of equivalence of *-representations, there are (at least) two situations where there is a criterion for equivalen …
Pedro Lauridsen Ribeiro's user avatar
2 votes
Accepted

Second-order term of the Fedosov quantised product

Indeed neither Fedosov's book nor his original paper (A Simple Geometrical Construction of Deformation Quantization, J. Diff. Geom. 40 (1993) 213-238) have an explicit formula for the second order ter …
Pedro Lauridsen Ribeiro's user avatar

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