Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Universal families of extensions of coherent systems   We prove a result of cohomology and base change for families of coherent
systems over a curve. We use that in order to prove the existence of
(non-split, non-degenerate) universal families of extensions for families of
coherent systems (in the spirit of the paper "Universal families of extensions"
by H. Lange). Such results will be applied in subsequent papers in order to
describe the wallcrossing for some moduli spaces of coherent systems.

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The categories of this paper are: astro-ph
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: cs
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The categories of this paper are: ao-sci
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The categories of this paper are: q-alg
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: comp-gas
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys