Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Moduli of unstable bundles of HN-length two with fixed algebra of
  endomorphisms   Let X be a smooth irreducible complex projective curve of genus g > 1. In
this paper, we give necessary and sufficient conditions for an unstable bundle
of HN-lenght 2 to have a particular algebra of endomorphisms. Then, fixing the
dimension of the algebra of endomorphisms we obtain a stratification of the
moduli scheme such that each strata is a coarse moduli space. A particular case
of interest is when the unstable bundles are simple. In that case the moduli
space is fine. Topological properties of those moduli spaces are described and
will depend on the generality of the curve X. Such results differ from the
corresponding results for the moduli space of stable bundles, where
non-emptiness, dimension etc. are independent of the curve.

19
The categories of this paper are: eess
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
33
The categories of this paper are: plasm-ph
12
The categories of this paper are: nucl-th
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
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The categories of this paper are: solv-int
7
The categories of this paper are: hep-th