Results 101 to 110 of about 93,496 (268)
On the stack of 0‐dimensional coherent sheaves: Motivic aspects
Bulletin of the London Mathematical Society, Volume 57, Issue 6, Page 1607-1649, June 2025.Abstract Let X$X$ be a variety. In this survey, we study (decompositions of) the motivic class, in the Grothendieck ring of stacks, of the stack Cohn(X)$\mathcal {C}\hspace{-2.5pt}{o}\hspace{-1.99997pt}{h}^n(X)$ of 0‐dimensional coherent sheaves of length n$n$ on X$X$. To do so, we review the construction of the support map Cohn(X)→Symn(X)$\mathcal {C}\
Barbara Fantechi, Andrea T. Ricolfi
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Parabolic subgroups in characteristics 2 and 3
Journal of the London Mathematical Society, Volume 111, Issue 6, June 2025.Abstract This text brings to an end the classification of non‐reduced parabolic subgroups in positive characteristic, especially 2 and 3: they are all obtained as intersections of parabolics having maximal reduced part. We prove this result and deduce a few geometric consequences on rational projective homogeneous varieties.
Matilde Maccan
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Profinite rigidity for free‐by‐cyclic groups with centre
Journal of the London Mathematical Society, Volume 111, Issue 6, June 2025.Abstract A free‐by‐cyclic group FN⋊ϕZ$F_N\rtimes _\phi \mathbb {Z}$ has non‐trivial centre if and only if [ϕ]$[\phi]$ has finite order in Out(FN)${\rm {Out}}(F_N)$. We establish a profinite rigidity result for such groups: if Γ1$\Gamma _1$ is a free‐by‐cyclic group with non‐trivial centre and Γ2$\Gamma _2$ is a finitely generated free‐by‐cyclic group ...
Martin R. Bridson, Paweł Piwek
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A Mackey-functor theoretic interpretation of biset functors
Advances in Mathematics, 2016 In this article, we consider a formulation of biset functors using the 2-category of finite sets with variable finite group actions. We introduce a 2-category $\mathbb{S}$, on which a biset functor can be regarded as a special kind of Mackey functors. This gives an analog of Dress' definition of a Mackey functor, in the context of biset functors.
Hiroyuki Nakaoka, Hiroyuki Nakaoka
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The quadratic Fock functor [PDF]
Journal of Mathematical Physics, 2010 We construct the quadratic analog of the boson Fock functor. While in the first order (linear) case all contractions on the 1-particle space can be second quantized, the semigroup of contractions that admit a quadratic second quantization is much smaller due to the nonlinearity.
Luigi Accardi, Ameur Dhahri
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On maximal proper subgroups of field automorphism groups
, 2009 Let $G$ be the automorphism group of an extension $F|k$ of algebraically closed fields of characteristic zero and of transcendence degree $n$, $1\le n\le\infty$. In this paper we (i) construct some maximal closed non-open subgroups $G_v$, and some (all,
Rovinsky, M.
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Journal of the London Mathematical Society, Volume 111, Issue 6, June 2025.Abstract We investigate the question of when a given homogeneous ideal is a limit of saturated ones. We provide cohomological necessary criteria for this to hold and apply them to a range of examples. In small cases, we characterise the limits. We also supply a number of auxiliary results on the classical and multigraded Hilbert schemes, for example ...
Joachim Jelisiejew, Tomasz Mańdziuk
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Inducing native Mackey functors to biset functors [PDF]
Journal of Pure and Applied Algebra, 2015 In this paper, we describe the induction functor from the category of native Mackey functors to the category of biset functors for a finite group $G$ over an algebraically closed field $k$ of characteristic zero. We prove two applications of this description.
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, 2008 Plato's ideas and Aristotle's real types from the classical age, Nominalism and Realism of the mediaeval period and Whitehead's modern view of the world as pro- cess all come together in the formal representation by category theory of exactness in ...
Heather, Michael, Rossiter, Nick
core
Homotopical commutative rings and bispans
Journal of the London Mathematical Society, Volume 111, Issue 6, June 2025.Abstract We prove that commutative semirings in a cartesian closed presentable ∞$\infty$‐category, as defined by Groth, Gepner, and Nikolaus, are equivalent to product‐preserving functors from the (2,1)‐category of bispans of finite sets. In other words, we identify the latter as the Lawvere theory for commutative semirings in the ∞$\infty$‐categorical
Bastiaan Cnossen +3 more
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