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作者：Muro, Fernando; Schwede, Stefan; Strickland, Neil
作者单位：University of Barcelona; University of Bonn; University of Sheffield
摘要：We exhibit examples of triangulated categories which are neither the stable category of a Frobenius category nor a full triangulated subcategory of the homotopy category of a stable model category. Even more drastically, our examples do not admit any non-trivial exact functors to or from these algebraic respectively topological triangulated categories.
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作者：Arakawa, Tomoyuki
作者单位：Nara Womens University
摘要：We study the representation theory of the W- algebra W-k((g) over bar) associated with a simple Lie algebra (g) over bar at level k. We show that the - reduction functor is exact and sends an irreducible module to zero or an irreducible module at any level k epsilon C. Moreover, we show that the character of each irreducible highest weight representation ofW(k)((g) over bar) is completely determined by that of the corresponding irreducible highest weight representation of affine Lie algebra g ...
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作者：Alexeev, Valery; Hacon, Christopher; Kawamata, Yujiro
作者单位：University System of Georgia; University of Georgia; Utah System of Higher Education; University of Utah; University of Tokyo
摘要：We prove that any sequence of 4-dimensional log flips that begins with a klt pair (X,D) such that -(K-X +D) is numerically equivalent to an effective divisor, terminates. This implies termination of flips that begin with a log Fano pair and termination of flips in a relative birational setting. We also prove termination of directed flips with big K-X +D. As a consequence, we prove existence of minimal models of 4-dimensional dlt pairs of general type, existence of 5-dimensional log flips, and ...
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作者：Kerr, Matt; Lewis, James D.
作者单位：University of Chicago; University of Alberta
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作者：Oh, Byeong-Kweon
作者单位：Sejong University
摘要：A positive definite integral quadratic form f is called n-regular if f represents every quadratic form of rank n that is represented by the genus of f. In this paper, we show that for any integer n greater than or equal to 27, every n-regular (even) form f is (even) n-universal, that is, f represents all (even, respectively) positive definite integral quadratic forms of rank n. As an application, we show that the minimal rank of n-regular forms has an exponential lower bound for n as it increa...
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作者：Popa, Sorin
作者单位：University of California System; University of California Los Angeles
摘要：We prove that if a countable discrete group Gamma is w- rigid, i. e. it contains an infinite normal subgroup H with the relative property (T) (e.g. Gamma = SL(2, Z) x Z(2), or Gamma = H x H' with H an infinite Kazhdan group and H' arbitrary), and V is a closed subgroup of the group of unitaries of a finite separable von Neumann algebra (e.g. V countable discrete, or separable compact), then any V- valued measurable cocycle for a measure preserving action Gamma curved right arrow X of Gamma on ...
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作者：Heath-Brown, D. R.
作者单位：University of Oxford
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作者：Dat, J.-F.
作者单位：Universite Paris 13
摘要：Non abelian Lubin-Tate theory studies the cohomology of some moduli spaces for p-divisible groups, the broadest definition of which is due to Rapoport-Zink, aiming both at providing explicit realizations of local Langlands functoriality and at studying bad reduction of Shimura varieties. In this paper we consider the most famous examples ; the so-called Drinfeld and Lubin-Tate towers. In the Lubin-Tate case, Harris and Taylor proved that the supercuspidal part of the cohomology realizes both t...
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作者：Jarvis, Tyler J.; Kaufmann, Ralph; Kimura, Takashi
作者单位：Brigham Young University; University of Connecticut; Boston University
摘要：We construct two new G-equivariant rings: K(X, G), called the stringy K-theory of the G-variety X, and H (X,G), called the stringy cohomology of the G-variety X, for any smooth, projective variety X with an action of a finite group G. For a smooth Deligne-Mumford stack, we also construct a new ring K-orb(X) called the full orbifold K-theory of X. We show that for a global quotient X = [X/G], the ring of G-invariants K-orb(X) of K (X, G) is a subalgebra of K-orb([X/G]) and is linearly isomorphi...
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作者：Kassabov, Martin
作者单位：Cornell University
摘要：We construct explicit generating sets S-n and S-n of the alternating and the symmetric groups, which turn the Cayley graphs C(Alt(n), S-n) and C(Sym( n), S-n) into a family of bounded degree expanders for all n.
