Quasicoherent sheaves on projective schemes over F_1

Date Issued
2017-07Publisher Version
10.1016/j.jpaa.2017.07.001Author(s)
Lorscheid, Oliver
Szczesny, Matt
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https://hdl.handle.net/2144/27844Citation (published version)
Oliver Lorscheid, Matt Szczesny. June 2018. "Quasicoherent sheaves on projective schemes over." Journal of Pure and Applied Algebra, Volume 222, Issue 6, pp. 1337-1354Abstract
Given a graded monoid A with 1, one can construct a projective monoid scheme MProj(A) analogous to Proj(R) of a graded ring R. This paper is concerned with the study of quasicoherent sheaves on MProj(A), and we prove several basic results regarding these. We show that:
1. every quasicoherent sheaf F on MProj(A) can be constructed from a graded A-set in analogy with the construction of quasicoherent sheaves on from graded R-modules
2.
if F is coherent on MProj(A), then F(n) is globally generated for large enough n, and consequently, that F is a quotient of a finite direct sum of invertible sheaves
3.
if F is coherent on MProj(A), then gamma(MProj(A)) is finitely generated over A0 (and hence a finite set if A0 = {0, 1}).
The last part of the paper is devoted to classifying coherent sheaves on P_1 in terms of certain directed graphs and gluing data. The classification of these over F_1 is shown to be much richer and combinatorially interesting than in the case of ordinary P_1, and several new phenomena emerge.
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