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30 votes
7 answers
5k views

Shuffle Hopf algebra: how to prove its properties in a slick way?

Let $k$ be a commutative ring with $1$, and let $V$ be a $k$-module. Let $TV$ be the $k$-module $\bigoplus\limits_{n\in\mathbb N}V^{\otimes n}$, where all tensor products are over $k$. We define a $k$...
darij grinberg's user avatar
21 votes
1 answer
2k views

On Tamarkin's proof of Etingof-Kazhdan quantization of Lie bialgebra

This question is motivated by the desire to understand better the interplay between Drinfeld associators, algebraic structures up to homotopy and related results. Recall that a Lie bialgebra is a Lie ...
Adrien's user avatar
  • 8,524
20 votes
1 answer
1k views

Are G_infinity algebras B_infinity? Vice versa?

What is the relationship between $G_\infty$ (homotopy Gerstenhaber) and $B_\infty$ algebras? In Getzler & Jones "Operads, homotopy algebra, and iterated integrals for double loop spaces" (a paper ...
Ian Shipman's user avatar
  • 1,038
14 votes
0 answers
792 views

Splitting of homomorphism from cactus group to permutation group

We all learned in kindergarten that the category of finite-dimensional (type I, say) $U_q(\mathfrak{g})$-modules is braided monoidal for $\mathfrak{g}$ a complex semisimple Lie algebra. This gives an ...
MTS's user avatar
  • 8,559
12 votes
1 answer
946 views

Compatibility of the KZ connection with operadic composition

In what sense is the Knizhnik-Zamolodchikov connection compatible with the operadic composition in the little discs operad and/or the operad of $\overline{M}_{0,n}$'s? Here are (some) details, ...
Pavol S.'s user avatar
  • 407
12 votes
0 answers
333 views

Does the $(\mathbb Z/2)$-graded isomorphism $E_n \cong E_{n+2}$ have any nice properties?

This question assumes everything is dg. Let's decide to work over the "field" $\mathbb Q[\mu,\mu^{-1}]$ where $\mu$ has homological degree $+2$. Then chain complexes are just $\mathbb Z/2$-graded. ...
Theo Johnson-Freyd's user avatar
11 votes
1 answer
356 views

What is the relation between 2-Gerstenhaber, CohFT, and Gerstenhaber geometrically?

Background. As we know from Fred Cohen's Thesis, taking homology of the little 2-discs operad $\mathcal{D}_2$ with coefficients in a field of characteristic zero produces the Gerstenhaber operad $\...
Nati's user avatar
  • 1,981
8 votes
1 answer
578 views

Transmutation versus operads

A while ago, I was reading Majid's book Foundations of quantum group theory, and Section 9.4 has a rather fascinating description of a Tannaka-Krein reconstruction result for quantum groups. In ...
S. Carnahan's user avatar
  • 45.7k
8 votes
1 answer
561 views

Identifying the little disk operad with parenthesized braids

Let $D_2$ be the topological operad of little disks. This operad can be modelled "combinatorially" in terms of an operad of groupoids called $\newcommand{\PaB}{\mathbf{PaB}}\PaB$, the operad of ...
Dan Petersen's user avatar
  • 40.2k
8 votes
0 answers
199 views

When are the categories of algebras over props (co)complete?

Suppose P is a (colored) prop in a closed symmetric monoidal locally presentable category C. Is the category Alg_P of algebras over P in C locally presentable? It seems that one can relatively easy ...
Dmitri Pavlov's user avatar
7 votes
0 answers
432 views

What is the endomorphism cooperad?

In Loday and Vallette's book on algebraic operads, they use the "Endomorphism cooperad $End^c_{s\mathbb{K}}$", where $s\mathbb{K}$ is the base field, shifted into (homological) degree one. This is an ...
Mark.Neuhaus's user avatar
  • 2,074
6 votes
1 answer
302 views

Knot Factorization Homology inputs

Following the paper by Ayala, Francis, and Tanaka: https://arxiv.org/pdf/1409.0848.pdf If we are talking about knots we are talking about framed 3-manifolds with a framed 1-dimensional sub-manifold ...
Matthew Levy's user avatar
6 votes
0 answers
353 views

Homotopy transfer of cyclic L-infinity algebras

Suppose $W$ is a cyclic $L_\infty$ algebra, i.e. $W$ has a non-degenerate, symmetric, invariant pairing $\langle\cdot,\cdot\rangle_W$. Let $V$ be a cochain complex, and suppose given the data of a ...
Eugene Rabinovich's user avatar
4 votes
1 answer
423 views

Formality of the little $n$-disks operad and deformation theory

In [Another proof of M. Kontsevich formality theorem], Tamarkin provides a proof of the formality of the differential graded Lie algebra controlling the deformation of a polynomial associative algebra....
thingsthatmighthavebeen's user avatar
4 votes
0 answers
205 views

Where is the Courant operad discussed?

Where is the Courant operad discussed? And hopefully defined precisely. By the Courant operad or rather a suitable generalization of operad to accommodate the inner product, the operad whose ...
Jim Stasheff's user avatar
  • 3,880
3 votes
1 answer
365 views

Brace algebra structure on the Hochschild complex of an associative algebra

As shown by Gerstenhaber and Voronov [Higher operations on the Hochschild complex], the Hochschild complex of an associative algebra is endowed with a natural structure of brace algebra. The first ...
thingsthatmighthavebeen's user avatar
3 votes
1 answer
277 views

What is the relation between cobar duality and Feynman transform

If $O$ is a cyclic operad, it can be regared as a modular operad $P$ with $P(g,n)=0$, for $g >0$. So we have cobar dual $BO$ and Feynman transform $FP$(with trivial cocycle). Is there any ...
Hao Yu's user avatar
  • 31
3 votes
1 answer
272 views

Embedding e_n -> e_m

Let $e_n$ be the operad of (say, rational) chains of the operad of little n-disks. Consider the natural embedding $e_n\to e_m$, where $n<m$ and $n,m>1$ induced by the embedding $\mathbb{R}^n\to \...
nikitamarkarian's user avatar
1 vote
0 answers
185 views

Exact sequence of L-infinity-algebras

We call a sequence of $L_\infty$-algebras (weak) maps $$0\to L\xrightarrow{f} M\xrightarrow{g} N\to 0$$ is exact if it is exact on the the underlying chain complexes level. Thought I don't know ...
Ma Ming's user avatar
  • 1,271