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"Quiver" is the word used for "directed graph" in some parts of representation theory. The main reason to use the term quiver is to indicate an interest in considering representations of the quiver.

23 votes
Accepted

Why are coherent sheaves on $\Bbb P^1$ derived equivalent to representations of the Kronecke...

This shouldn't be surprising, though: path algebras of quivers have global dimension one, so you shouldn't expect their derived categories to agree with derived categories of sheaves on higher-dimensional …
Hugh Thomas's user avatar
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8 votes

Quiver representations

Edited to add: oh, another thing: for Dynkin quivers, there is a way to construct any indecomposable by applying a sequence of "reflection functors" starting from a simple indecomposable, but the sequence …
Hugh Thomas's user avatar
  • 6,327
7 votes

The Fukaya category of a simple singularity (reference request)

This sounds wrong to me. I think $D^b(Q)$ should be replaced by the derived category of finite length modules over the corresponding preprojective algebra of affine type. Homological mirror symmetry …
Hugh Thomas's user avatar
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7 votes

ubiquity, importance of path algebras

For me, path algebras of quivers have provided a lovely setting in which to learn about homological algebra, because the objects involved are simple enough that you can understand them quite concretely …
Hugh Thomas's user avatar
  • 6,327
6 votes

How is the free modular lattice on 3 generators related to 8-dimensional space?

Edited to be more of an answer. But, unfortunately, to be quite wrong. I apologize for having been borne away by my enthusiasm. The picture of the free modular lattice above shows thirty elements. …
Hugh Thomas's user avatar
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6 votes
1 answer
200 views

Closures of orbits in the space of representations of a quiver

Let $Q$ be a quiver, and let $d=(d_i)$ be a dimension vector. We can consider Rep($Q,d$), the affine space consisting of representations of $Q$ with dimension vector $d$. The general linear $GL(d)= \p …
Hugh Thomas's user avatar
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6 votes

Do morphisms of finitely-decomposable Quiver representations map indecomposables nicely?

There is another way to relate representations of $Q$ to representations of $Q'$: reflection functors. These are quite easy to describe combinatorially. One downside is that the way they work is by …
Hugh Thomas's user avatar
  • 6,327
6 votes

Quiver representations of type $D_n$ mutation class

The quiver given in the question has five simple modules, six which correspond to a single arrow, and the remaining representations have support as follows: 123, 124, 125, 235, 345, 1235, 12235 (note …
Hugh Thomas's user avatar
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5 votes

What's an illustrative example of a tame algebra?

For other tame quivers with no relations over an algebraically closed ground field, the situation is slightly worse: the natural indexing set for the representations whose dimension vector is the null …
Hugh Thomas's user avatar
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5 votes
0 answers
363 views

Kac's theorem for quiver representations over an arbitrary ground field

Let $Q$ be a quiver without loops (cycles of length 1). Kac proved that if $K$ is algebraically closed, the dimension vectors of indecomposable representations of $Q$ over $K$ are exactly the positiv …
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4 votes
Accepted

Why Jacobson, but not the left (right) maximals individually?

Dag has already answered the case where the quiver is finite and acyclic, and given a conjecture in the case that cycles are allowed. I will prove his conjecture. Suppose we have an element $x$ of …
Hugh Thomas's user avatar
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4 votes
Accepted

Finding exceptional regular representations of $\tilde{D}_4$ efficiently

The AR quiver of the regular representations of an affine quiver consists of infinitely many "tubes". A tube of rank $r$ has $r$ modules on what you call the border. Let me number them $B_1, B_2, \dot …
Hugh Thomas's user avatar
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4 votes

Dimension of preprojective algebra of Dynkin type

As a module over $kQ$, a finite-type preprojective algebra is a direct sum of each of the indecomposable $kQ$-modules once. Thus, the total dimension is the sum over all positive roots of the height …
Hugh Thomas's user avatar
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3 votes
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Closures of orbits in the space of representations of a quiver

There is an example in section 3.4 of Riedtmann's paper "Degenerations for representations of quivers with relations", Ann. sci. Éc. Norm. Sup. v. 19 (1986), 275-301. …
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3 votes
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Intuition for the Euler form in a finitary category

This answer perhaps says things that are all obvious to the OP. $\textrm{Ext}^i(A,B)$ is a vector space over the ground field, so its cardinality is $q^d$ where $d$ is the dimension of the vector sp …
Hugh Thomas's user avatar
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