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作者：Wise, DT
作者单位：University of California System; University of California Berkeley
摘要：A subgroup M subset of G is almost malnormal provided that for each g epsilon G - M, the intersection M-g boolean AND M is finite. It is proven that the free product of two virtually free groups amalgamating a finitely generated almost malnormal subgroup, is residually finite. A consequence of a generalization of this result is that an acute-angled n-gon of finite groups is residually finite if n greater than or equal to 4. Another consequence is that if G acts properly discontinuously and coc...
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作者：Elliott, PDTA
作者单位：University of Colorado System; University of Colorado Boulder
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作者：Grove, K; Ziller, W
作者单位：University System of Maryland; University of Maryland College Park; University of Pennsylvania
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作者：Ball, K; Rivoal, T
作者单位：University of London; University College London; Universite de Caen Normandie
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作者：Manetti, M
作者单位：Sapienza University Rome
摘要：In this paper we show that the number of deformation types of complex structures on a fixed smooth oriented four-manifold can be arbitrarily large. The examples that we consider in this paper are locally simple abelian covers of rational surfaces. The proof involves the algebraic description of rational blowdowns, classical Brill-Noether theory and deformation theory of normal flat abelian covers.
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作者：Rapinchuk, AS; Segev, Y
作者单位：University of Virginia; Ben-Gurion University of the Negev
摘要：Let D be a finite dimensional division algebra and N a subgroup of finite index in DX. A valuation-like map on N is a homomorphism psi: N --> T from N to a (not necessarily abelian) linearly ordered group T satisfying N<-alpha + 1 subset of or equal to N<-alpha for some nonnegative alpha is an element of T such that N<-alpha not equal 0 where N<-alpha = {x is an element of N / psi (x) < -alpha}. We show that this implies the existence of a nontrivial valuation v of D with respect to which N is...
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作者：Ein, L; Lazarsfeld, R; Smith, KE
作者单位：University of Illinois System; University of Illinois Chicago; University of Illinois Chicago Hospital; University of Michigan System; University of Michigan
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作者：Köhler, K; Roessler, D
作者单位：University of Bonn; Universite Paris Cite
摘要：We consider arithmetic varieties endowed with an action of the group scheme of n-th roots of unity and we define equivariant arithmetic K-0-theory for these varieties. We use the equivariant analytic torsion to define direct image maps in this context and we prove a Riemann-Roch theorem for the natural transformation of equivariant arithmetic K-0-theory induced by the restriction to the fixed point scheme; this theorem can be viewed as an analog, in the context of Arakelov geometry, of the reg...
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作者：Minsky, YN
作者单位：State University of New York (SUNY) System; Stony Brook University
摘要：We show that a Kleinian surface group, or hyperbolic 3-manifold with a cusp-preserving homotopy-equivalence to a surface, has bounded geometry if and only if there is an upper bound on an associated collection of coefficients that depend only on its end invariants. Bounded geometry is a positive lower bound on the lengths of closed geodesics. When the Surface is a once-punctured torus, the coefficients coincide with the continued fraction coefficients associated to the ending laminations.
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作者：Madsen, I; Tillmann, U
作者单位：Aarhus University; University of Oxford
摘要：In [T2] it was shown that the classifying space of the stable mapping class groups after plus construction Z x B Gamma (+)(infinity) has an infinite loop space structure. This result and the tools developed in [BM] to analyse transfer maps, are used here to show the following splitting theorem. Let Sigma (infinity)(CP+infinity)(p)(Lambda) similar or equal to E(0)nu (...)nuE(p-2) be the Adams-splitting of the p-completed suspension spectrum of CP+infinity. Then for some infinite loop space W-p,...
