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7 votes

Can an algebra over an operad be described by generators and relations?

Yes, sure. You can take the free $\mathcal{O}$-algebra on your set of generators, and mod out by the $\mathcal{O}$-ideal generated by your relations. Then you get an algebra $A$ presented by generato …
Najib Idrissi's user avatar
6 votes
Accepted

An operad-like structure, is there a name for it?

Since operads have units, this is equivalent to giving composition maps $\circ_i : M(k) \otimes P(l) \to P(k+l-1)$ for $1 \le i \le k$ (simply put, $m \circ_i p = m(1,\dots,1,p,1,\dots,1)$ where $1$ is …
Najib Idrissi's user avatar
5 votes

Obstructions to $E_2$-algebra structure on $E_1$-algebra

But I think you can use a strategy similar to what is done in the paper The Intrinsic Formality of $E_n$-operads by Fresse and Willwacher. I'm not saying it's easy, but it's systematic. …
Najib Idrissi's user avatar
5 votes
Accepted

Poisson and homotopy Poisson operads

I'll use the standard notation that $\mathrm{Pois}_n$ is the usual $n$-Poisson operad. I'll assume that you mean $(\mathrm{Pois}_n)_\infty = \Omega(\mathrm{Pois}_n^¡)$. Then no, $(\mathrm{Pois}_n)_\in …
Najib Idrissi's user avatar
3 votes

Are $E_n$-operads not formal in characteristic not equal to zero?

on the arXiv last week (1807.11671) proving that $E_2$ is not formal over $\mathbb{F}_2$ as a non-symmetric operad (what he calls planar operad), i.e. you cannot find a zigzag of quasi-isomorphisms of operads
Najib Idrissi's user avatar
2 votes
Accepted

$H$-space structure on coloured algebras

This is the homotopy version of the following data: a collection of spaces $\{X_c\}_c$ for all colors $c$; units $e_c \in X_c$; multiplications $- \cdot_c - : X_d \times X_{d'} \to X_c$; satisfyin …
Najib Idrissi's user avatar
9 votes
Accepted

Free operad over a monoid object

Let me mention that this is related to this earlier question of mine (which is unanswered :-( ) and more generally to semi-direct products of operads by bialgebras. …
Najib Idrissi's user avatar
2 votes
Accepted

A model for the framed little disks operad $f{\cal D}_n$ with arity one *equal* to $SO(n)$?

Let me summarize the comments. You have several possibilities: [Ryan's comment] You can consider the sub-operad $fD'_n \subset fD_n$ such that $fD'_n(r) = fD_n(r)$ for $r \ge 2$, and $fD'_n(1) = SO( …
Najib Idrissi's user avatar
6 votes
Accepted

Operad structure on Kontsevich's admissible graphs

Inside an aerial vertex, you can insert a unicolored graph, of the kind found in Kontsevich's paper Operads and motives in deformation quantization. …
Najib Idrissi's user avatar
11 votes
Accepted

$k$-Disk algebras versus $E_k$ algebras

Wahl, Framed discs operads and Batalin-Vilkovisky algebras. Q. J. Math., 2003, 54, 213-231"). These two operads are not weakly equivalent, and their categories of algebras are different. … More generally, $\mathtt{D}_n(1)$ is contractible, whereas $\mathtt{fD}_n(1) \simeq \mathrm{SO}(n)$ is non-contractible, so the operads cannot be weakly equivalent. …
Najib Idrissi's user avatar
7 votes

Does every equivalence of operads in the category of small categories have a weak inverse?

Consider the equivalence $\mathsf{PaB} \to \mathsf{CoB}$ from the operad of parenthesized braids to the operad of colored braids (which are both operads in groupoids). … The point of these categorical equivalences is that they induce equivalences of simplicial operads after applying the classifying space functor, see the volume II of the book mentioned above. …
Najib Idrissi's user avatar
10 votes

Are there prominent examples of operads in schemes?

They give several examples, and the paper is a great motivation for why one would be interested in getting operads in schemes (because under good circumstances, they are formal). …
Najib Idrissi's user avatar
4 votes
Accepted

"Left Brace Module"

There is also Horel's paper Operads, Modules and Topological Field Theories. …
Najib Idrissi's user avatar
2 votes
Accepted

The table reduction morphism of operads from Barratt-Eccles to Surjection

As written in the paper that you cite, this construction originates from two papers of McClure–Smith, and a geometric interpretation of the table reduction morphism is given in: Clemens Berger and …
Najib Idrissi's user avatar
1 vote
Accepted

A differential graded Lie algebra with the Hochschild differential

Not in general, no. However $H^*(V,W)$ is a representation of the Lie algebra $H^*(V,V)$, by letting, for $f \in \hom(V^{\otimes m}, W)$ and $g \in \hom(V^{\otimes n}, V)$, $$f \circ g := \sum_{i=1}^m …
Najib Idrissi's user avatar

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