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Topological quantum field theory.

3 votes
0 answers
91 views

Explicit examples of 4-cocycles over finite 2-groups

By a (finite) 2-group $X$, I mean a finite group $G$, a finite abelian group $A$, an action of $G$ on $\operatorname{Aut}(A)$, as well as a 3-cocycle $\alpha\in H^3(BG, A)$. They are also equivalent t …
Andi Bauer's user avatar
  • 3,001
4 votes
0 answers
321 views

CFT as an axiomatic field theory

I'm trying to understand CFT from a purely axiomatic-field-theoretical perspective. That is, there is a vector space $V$ associated to the circle, and an element of $V^{\otimes n}$ associated to every …
Andi Bauer's user avatar
  • 3,001
3 votes
2 answers
203 views

Classification of crossed $G$-algebras

Added later: As Viktor Ostrik points out in a comment, what I'm looking for is a classification of so-called crossed $G$-algebras corresponding to homotopy TQFTs with homotopy target space $K(G, 1)$ a …
Andi Bauer's user avatar
  • 3,001
6 votes
3 answers
347 views

Original reference for generators and relations of 2-dimensional TQFT

What is the original reference where it was first proven that the generators and relations of the 2-dimensional cobordism category are those of commutative Frobenius algebras? I've seen this article b …
Andi Bauer's user avatar
  • 3,001
7 votes
0 answers
181 views

What are the generators and relations of the conformal cobordism category?

According to a definition by Segal, a $2$-dimensional CFT is a symmetric monoidal functor from the category of oriented conformal cobordisms to the cateogry of projective complex vectorspaces. Coming …
Andi Bauer's user avatar
  • 3,001
5 votes
2 answers
379 views

Are there examples of finite-dimensional complex non-semisimple non-commutative symmetric Fr...

Are there any examples of finite-dimensional complex non-semisimple non-commutative symmetric Frobenius algebras? Or can one show that none exist? I went through this list of all complex associative a …
Andi Bauer's user avatar
  • 3,001
7 votes
0 answers
115 views

Are there attempts to numerically finding algebraic structures over finite-dimensional vecto...

By "algebraic structure" I mean a finite set of linear operators between tensor products of copies of one (or more) finite-dimensional (complex or real) vector spaces, fulfilling a set of axioms with …
Andi Bauer's user avatar
  • 3,001
4 votes
0 answers
262 views

Classification of special symmetric Frobenius algebras over real vector spaces

Is there a general classification of special symmetric Frobenius algebras over real vector spaces? I know that $n\times n$ matrix algebras, the quaternions, the complex numbers, the trivial algebra, a …
Andi Bauer's user avatar
  • 3,001
9 votes
1 answer
411 views

Generators and relations for the 2-dimensional unoriented cobordism category

It is very well known in the field of TQFT that the 2-dimensional oriented cobordism category is generated by the disk and the pair of pants (each going in both directions), subject to a finite set of …
Andi Bauer's user avatar
  • 3,001
11 votes
2 answers
610 views

What are the topological phases of quantum Hall systems?

(Fractional) quantum Hall systems are $2+1$-dimensional models which are said to possess topological order. One (maybe even complete) set of invariants of topological phases in $2+1$ dimensions is giv …
Andi Bauer's user avatar
  • 3,001
5 votes
0 answers
237 views

Does Dijkgraaf-Witten theory have a time-reversal symmetry?

By having a time-reversal symmetry I mean that there is a local anti-unitary symmetry (representing the non-trivial element of $Z_2$) of the state-sum construction (or, if you want, of the associated …
Andi Bauer's user avatar
  • 3,001
11 votes
1 answer
667 views

Importance of the principal bundle in Chern-Simons theory

This is a very basic beginners question about Chern-Simons theory. The configurations that we sum over to get the partition function are given by a Lie-algebra valued 1-form $A$ on a topological 3-man …
Andi Bauer's user avatar
  • 3,001
21 votes
1 answer
1k views

Fully extended TQFT and lattice models

I often read that fully extended TQFTs are supposed to classify topological phases of matter. So I would like to understand the formal nature of fully extended TQFTs on a more direct physical level (w …
Andi Bauer's user avatar
  • 3,001
8 votes
2 answers
425 views

How do I calculate the modular fusion category from a given Lie algebra and level in Chern-S...

In Chern-Simons theory, one has modular fusion categories that are labelled by a Lie algebra and a "level", e.g. $SU(2)_2$ ("$SU(2)$ level $2$"). Physically this modular fusion category describes the …
Andi Bauer's user avatar
  • 3,001
8 votes
0 answers
302 views

Why are Levin-Wen/Turaev-Viro models said to be non-chiral?

I'd like to bring together the following two notions of "non-chiral": On the abstract algebraic side, a modular fusion category describing the anyon content of some physical system is said to be non- …
Andi Bauer's user avatar
  • 3,001

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