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Non-commutative rings and algebras, non-associative algebras, universal algebra and lattice theory, linear algebra, semigroups. For questions specific to commutative algebra (that is, rings that are assumed both associative and commutative), rather use the tag ac.commutative-algebra.

4 votes
1 answer
87 views

Lie algebra with finitely generated envelope

If a Lie algebra $\mathfrak g$ is finitely generated, its enveloing algebra $U\mathfrak g$ is finitely generated as an associative algebra. In fact, taking the enveloping algebra of the surjection $\m …
Qwert Otto's user avatar
5 votes
1 answer
242 views

Infinite-dimensional, non-unital Frobenius algebras

A Frobenius algebra is a tuple $(A,\mu,\delta,\eta,\varepsilon)$, where $A$ is a vector space over some field, $(A,\mu,\eta)$ a unital associative algebra, and $(A,\delta,\varepsilon)$ a counital coas …
Qwert Otto's user avatar
2 votes
Accepted

Infinite-dimensional, non-unital Frobenius algebras

It is studied under the name "nearly Frobenius algebras" in this paper. In Example 3.3, the algebra $\mathbb{C}[[x,x^{-1}]]$ of Laurent series can be endowed with (countably) many unital but not co-un …
Qwert Otto's user avatar
4 votes
2 answers
391 views

Units of the group algebra of a free group

Let $K$ be a field of characteristic zero and $F_n$ be a free group of rank $n$. What is known about the group of units $K[F_n]^\times$? In the case of $n=1$, there are only trivial units: $K[F_1]^\ti …
Qwert Otto's user avatar
5 votes
0 answers
299 views

Connections in non-commutative geometry

Let $K$ be a field, $A$ a unital associative $K$-algebra and $M$ a left $A$-module. A connection on $M$ is a $K$-linear map $\nabla:M\to \Omega^1A\otimes_AM$ which satisfies the Leibniz rule. Accordin …
Qwert Otto's user avatar
9 votes
1 answer
232 views

Formal smoothness of path algebras and connections

Let $k$ be a field of characteristic zero and $A = kQ$ the path algebra associated with a quiver $Q$. The algebra $A$ is said to be formally smooth over $k$ if $$ \Omega^1_kA = \operatorname{Ker}(\mat …
Qwert Otto's user avatar
3 votes
1 answer
417 views

Is Malcev completion an embedding?

The Malcev completion of an abstract group $G$ over a field $k$ of characteristic zero is defined by $$\hat G = \mathbb{G}(\widehat{k[G]}) ,$$ the group-like part of the completed (by the augmentation …
Qwert Otto's user avatar
7 votes
0 answers
280 views

Lie algebra cohomology of the space of vector fields

For a (closed and oriented) manifold $M$, the first Lie algebra cohomology $H^1(\mathrm{Vect}(M),C^\infty(M))$ of the space of vector fields with coefficients in smooth functions is isomorphic to $H^1 …
Qwert Otto's user avatar
3 votes
0 answers
100 views

Pairing on a Koszul dual pair

Let $A$ be a graded quadratic algebra over a field $k$, and suppose that it admits the Koszul dual $A^!$. I want to know if there is a natural pairing $A\otimes A^!\to k$ or something similar to this. …
Qwert Otto's user avatar
5 votes
0 answers
205 views

Cohomology of representation varieties and the Hochschild cohomology

Let $k$ be a field, $A$ a $k$-algebra, and $V$ a $k$-vector space. Then we can consider the representation varieties of $A$ on $V$: $\mathrm{Hom}_{k\textrm{-alg}}(A, \mathfrak{gl}(V))$ and $\mathrm{Ho …
Qwert Otto's user avatar
3 votes
0 answers
125 views

Trace map on Ext group

Let $R$ be a (possibly non-commutative) unital ring and $M$ be a perfect left $R$-module. Then, we have the trace map $$ \operatorname{Tr}\colon \mathrm{Hom}_R(M,M)\to R/[R,R]\,. $$ According to the a …
Qwert Otto's user avatar
5 votes
0 answers
123 views

Lie algebra cohomology of formal non-commutative vector fields

Let $k$ be a field of characteristic $0$ and $A=k\langle\langle x_1,\dotsc,x_n\rangle\rangle$ be a free completed associative algebra. The space of continuous derivations $\mathrm{Der}(A)$ is isomorph …
Qwert Otto's user avatar