Skip to main content
Search type Search syntax
Tags [tag]
Exact "words here"
Author user:1234
user:me (yours)
Score score:3 (3+)
score:0 (none)
Answers answers:3 (3+)
answers:0 (none)
isaccepted:yes
hasaccepted:no
inquestion:1234
Views views:250
Code code:"if (foo != bar)"
Sections title:apples
body:"apples oranges"
URL url:"*.example.com"
Saves in:saves
Status closed:yes
duplicate:no
migrated:no
wiki:no
Types is:question
is:answer
Exclude -[tag]
-apples
For more details on advanced search visit our help page
Results tagged with
Search options answers only not deleted user 7410

Theory and applications of probability and stochastic processes: e.g. central limit theorems, large deviations, stochastic differential equations, models from statistical mechanics, queuing theory.

56 votes
Accepted

What is a cumulant really?

Cumulants have many other names depending on the context (statistics, quantum field theory, statistical mechanics,...): seminvariants, truncated correlation functions, connected correlation functions, …
Abdelmalek Abdesselam's user avatar
45 votes

What are the big problems in probability theory?

Maybe the no1 problem of probability is to make rigorous what one finds in just about any textbook in statistical mechanics. In other words it is to put the predictions of Wilson's renormalization gro …
33 votes

Integration of a function over 7-sphere

The result is $$ I(k)=\frac{2\pi^4\ \Gamma\left(\frac{k}{2}+1\right)\Gamma\left(\frac{k}{2}+2\right)}{\Gamma(k+4)}\ , $$ which can be simplified a bit more using the Legendre Duplication Formula. More …
Abdelmalek Abdesselam's user avatar
31 votes

Why is Quantum Field Theory so topological?

The framing of your question is a bit ambiguous and perhaps there are two different questions here depending on the context and interpretation. One could approach your question from the point of view …
Abdelmalek Abdesselam's user avatar
30 votes

What mathematical treatment is there on the renormalization group flow in a space of Lagrang...

Dec 2017 edit: I just put a hopefully useful detailed complement to this post on https://physics.stackexchange.com/questions/372306/wilsonian-definition-of-renormalizability The answer to your ques …
Abdelmalek Abdesselam's user avatar
30 votes

A roadmap to Hairer's theory for taming infinities

Let me comment on points 4) and 5). The problem with infinities in QFT or traditional equilibrium statistical field theory is related to the one addressed by Martin's theory but there are some differe …
Abdelmalek Abdesselam's user avatar
26 votes

Central limit theorem via maximal entropy

There is a book on the subject: "Information Theory and The Central Limit Theorem" by Oliver Johnson. The article by Anshelevich mentioned by Yemon considers the operator $T$ acting on probability den …
Abdelmalek Abdesselam's user avatar
21 votes

Determinant of the random matrix $X^2+Y^2$

This is easy to do using a graphical calculus for contractions of old-fashioned tensors. See this recent article for an example of application of such techniques and hopefully useful references. Here …
Abdelmalek Abdesselam's user avatar
18 votes

Why is conformal invariance only possible for massless theories?

It's not clear from the post if you are talking about classical or quantum field theories. In QFT, conformal invariance implies scale invariance. If the theory has a mass $m$ then, as John explained, …
Abdelmalek Abdesselam's user avatar
16 votes

Positivity of certain Fourier transform

I think the result goes back to Polya, see "Some theorems on stable processes" by Blumenthal and Getoor. Another reference is Paul Lévy "Sur une application de la dérivée d’ordre non entier au calcul …
Abdelmalek Abdesselam's user avatar
13 votes

Gaussian distributions as fixed points in Some distribution space

Indeed, as J.C. said this has to do with the renormalization group (RG) which in the present context is a transformation $\mu\rightarrow \mu\ast\mu$ followed by rescaling by $\sqrt{2}$ to keep the var …
Abdelmalek Abdesselam's user avatar
10 votes

Free Boson Correlator $ \langle X(z)X(w) \rangle =- \ln |z - w| $

My answer Wiener measure and Bochner Minlos can help defining a free massless real scalar field as a random element of $S_0'(\mathbb{R}^2)$. Namely, take the Schwartz space of rapidly decaying test fu …
Abdelmalek Abdesselam's user avatar
9 votes

Wiener measure and Bochner Minlos

Yes. Wiener measure can be arrived at using the Bochner-Minlos Theorem in at least two ways. One can consider the bilinear form on $S(\mathbb{R})$ $$ C(f,g)=\int_{\mathbb{R}}\ \overline{\widehat{f} …
Abdelmalek Abdesselam's user avatar
9 votes
Accepted

No kernel of the form $\lvert x - y\rvert^{-1}$ on tempered distributions?

Yes it is possible. Let $K\in S'(\mathbb{R}^2)$ be the distribution acting on test functions $f(x,y)$ by $$ K(f)=\int_{|x-y|\ge 1} \frac{f(x,y)}{|x-y|}\ dx\ dy \ + \int_{|x-y|< 1} \frac{f(x,y)-f(x,x)} …
Abdelmalek Abdesselam's user avatar
8 votes
Accepted

How do you know that you have succeeded-Constructive Quantum Field Theory and Lagrangian

The axioms don't tell you what theory you constructed. For that you need to go beyond the construction of correlation functions of the elementary field $\phi$ (the basic chapter on renormalization in …
Abdelmalek Abdesselam's user avatar

15 30 50 per page