منابع مشابه
The Keel–mori Theorem via Stacks
Let X be an Artin stack (always assumed to have quasi-compact and separated diagonal over SpecZ; cf. [2, §1.3]). A coarse moduli space for X is a map π : X → X to an algebraic space such that (i) π is initial among maps from X to algebraic spaces (note that the category of maps from X to an algebraic space is discrete), and (ii) for every algebraically closed field k the map [X (k)]→ X(k) is bi...
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We prove that the Cox ring of the projectivization P(E) of a rank two toric vector bundle E , over a toric variety X, is a finitely generated k-algebra. As a consequence, P(E) is a Mori dream space if the toric variety X is projective and simplicial.
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Let X be a smooth Mori dream space of dimension ≥ 4. We show that, if X satisfies a suitable GIT condition which we call small unstable locus, then every smooth ample divisor Y of X is also a Mori dream space. Moreover, the restriction map identifies the Néron-Severi spaces of X and Y , and under this identification every Mori chamber of Y is a union of some Mori chambers of X , and the nef con...
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The contact map of a protein fold is a graph that represents the patterns of contacts in the fold. It is known that the contact map can be decomposed into stacks and queues. RNA secondary structures are special stacks in which the degree of each vertex is at most one and each arc has length of at least two. Waterman and Smith derived a formula for the number of RNA secondary structures of lengt...
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Recent results in geometric invariant theory (GIT) for non-reductive linear algebraic group actions allow us to stratify quotient stacks of the form [X/H ], where X is a projective scheme and H is a linear algebraic group with internally graded unipotent radical acting linearly onX , in such a way that each stratum [S/H ] has a geometric quotient S/H . This leads to stratifications of moduli st...
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ژورنال
عنوان ژورنال: Mathematische Zeitschrift
سال: 2015
ISSN: 0025-5874,1432-1823
DOI: 10.1007/s00209-015-1472-1