Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Beyond Degree Choosability   Let $G$ be a connected graph with maximum degree $\Delta$. Brooks' theorem
states that $G$ has a $\Delta$-coloring unless $G$ is a complete graph or an
odd cycle. A graph $G$ is \emph{degree-choosable} if $G$ can be properly
colored from its lists whenever each vertex $v$ gets a list of $d(v)$ colors.
In the context of list coloring, Brooks' theorem can be strengthened to the
following. Every connected graph $G$ is degree-choosable unless each block of
$G$ is a complete graph or an odd cycle; such a graph $G$ is a \emph{Gallai
tree}.
  This degree-choosability result was further strengthened to Alon--Tarsi
orientations; these are orientations of $G$ in which the number of spanning
Eulerian subgraphs with an even number of edges differs from the number with an
odd number of edges. A graph $G$ is \emph{degree-AT} if $G$ has an Alon--Tarsi
orientation in which each vertex has indegree at least 1. Alon and Tarsi showed
that if $G$ is degree-AT, then $G$ is also degree-choosable. Hladky, Kral, and
Schauz showed that a connected graph is degree-AT if and only if it is not a
Gallai tree. In this paper, we consider pairs $(G,x)$ where $G$ is a connected
graph and $x$ is some specified vertex in $V(G)$. We characterize pairs such
that $G$ has no Alon--Tarsi orientation in which each vertex has indegree at
least 1 and $x$ has indegree at least 2. When $G$ is 2-connected, the
characterization is simple to state.

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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: q-bio
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The categories of this paper are: bayes-an
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The categories of this paper are: dg-ga
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
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The categories of this paper are: supr-con
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The categories of this paper are: physics
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The categories of this paper are: acc-phys
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The categories of this paper are: q-alg
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The categories of this paper are: cond-mat
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex