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 not deleted user 290

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

4 votes
Accepted

Computational trick used in QFT and the Jones Polynomial

I don't know what you mean by "composition as in $\pi_3(G)$" unless either $M$ is a $3$-sphere or $G$ is, in addition, assumed to be simply connected. If the latter, then $G$ is $2$-connected, and so …
Qiaochu Yuan's user avatar
5 votes

Observables and dimensional analysis

What we mean when we say that two quantities have different units is that if we change something about how we measure quantities, the two quantities will behave differently. For example, if one quanti …
Qiaochu Yuan's user avatar
32 votes

A soft introduction to physics for mathematicians who don't know the first thing about physics

Dolgachev has some lecture notes for an introduction to physics course he taught to math graduate students. Certainly it presumes mathematical maturity.
29 votes
3 answers
4k views

How can simple physical "proofs" of mathematical facts be made rigorous?

Mark Levi's The Mathematical Mechanic is a book of examples of how physical reasoning can be used to solve mathematical problems; another couple of examples is in this blog post at Concrete Nonsense. …
Qiaochu Yuan's user avatar
20 votes
6 answers
5k views

Can I derive the Boltzmann distribution by an invariance argument?

In statistical mechanics, the Boltzmann distribution gives the probability of a system being in state $i$ as $$\displaystyle \frac{e^{- \beta E_i}}{\sum_i e^{-\beta E_i}}$$ where $E_i$ is the energy …
Qiaochu Yuan's user avatar
2 votes

Is there a nice "synthetic" way for doing differential geometry on infinite dimensional vect...

Your first requirement suggests to me that you want to think of an infinite-dimensional vector space as an ind-object, namely the filtered colimit of its finite-dimensional subspaces. If so, one forma …
Qiaochu Yuan's user avatar
5 votes
Accepted

Spin structure for varieties, especially finite field

Let me work with arbitrary affine schemes $X = \text{Spec } k$. I believe there is a reasonable notion of a spin structure on a quadratic module $(V, q)$ over $k$, by which I mean a pair consisting of …
Qiaochu Yuan's user avatar
31 votes

Representation theory and elementary particles

You can understand this philosophy as a generalization of Noether's theorem. Let me only state Noether's theorem in the quantum case because it's actually easier to understand there than in the classi …
Qiaochu Yuan's user avatar
147 votes
43 answers
61k views

Where does a math person go to learn quantum mechanics?

My undergraduate advisor said something very interesting to me the other day; it was something like "not knowing quantum mechanics is like never having heard a symphony." I've been meaning to learn q …
21 votes
3 answers
2k views

What is Chern-Simons theory expected to assign to a point?

Let $G$ be a compact, connected, (simply connected?) Lie group and let $k \in H^4(BG, \mathbb{Z})$ be a cohomology class. Witten showed, at a physical level of rigor, that this data determines a $3$-d …
Qiaochu Yuan's user avatar
2 votes
Accepted

Symplectic structure on $Sym^kG^{\mathbb{C}} $

Such a thing doesn't exist. The symmetric square of the cotangent bundle of a real $n$-dimensional manifold has dimension $n + {n+1 \choose 2}$, which is in particular odd whenever $n \equiv 2 \bmod 4 …
Qiaochu Yuan's user avatar
12 votes

How much linear algebra can be done with graphs?

Well, unlike the determinant, the eigenvalues of an integer matrix aren't integers, so I don't know how much to expect here as far as a direct combinatorial interpretation of any kind. However, there …
Qiaochu Yuan's user avatar
2 votes
Accepted

What is the precise relationship between real Poisson algebras and commutative $C^*$ algebras?

Quantum mechanics is not just noncommutative probability; a commutative $C^{\ast}$-algebra alone corresponds via Gelfand duality to some (locally) compact Hausdorff space $X$, which is not equipped wi …
Qiaochu Yuan's user avatar
22 votes
Accepted

What is the relation between the sphere spectrum and supersymmetry?

Let's agree that whatever "supersymmetry" means it has something to do with working in the symmetric monoidal category of super vector spaces (e.g. we might want to consider Lie algebras or commutativ …
Qiaochu Yuan's user avatar