1,605 research outputs found

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    Algebraic solutions of linear differential equations: an arithmetic approach

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    Given a linear differential equation with coefficients in Q(x)\mathbb{Q}(x), an important question is to know whether its full space of solutions consists of algebraic functions, or at least if one of its specific solutions is algebraic. After presenting motivating examples coming from various branches of mathematics, we advertise in an elementary way a beautiful local-global arithmetic approach to these questions, initiated by Grothendieck in the late sixties. This approach has deep ramifications and leads to the still unsolved Grothendieck-Katz pp-curvature conjecture.Comment: 47 page

    Equivariant toric geometry and Euler-Maclaurin formulae

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    We consider equivariant versions of the motivic Chern and Hirzebruch characteristic classes of a quasi-projective toric variety, and extend many known results from non-equivariant to the equivariant setting. The corresponding generalized equivariant Hirzebruch genus of a torus-invariant Cartier divisor is also calculated. Further global formulae for equivariant Hirzebruch classes are obtained in the simplicial context by using the Cox construction and the equivariant Lefschetz-Riemann-Roch theorem. Alternative proofs of all these results are given via localization at the torus fixed points in equivariant KK- and homology theories. In localized equivariant KK-theory, we prove a weighted version of a classical formula of Brion for a full-dimensional lattice polytope. We also generalize to the context of motivic Chern classes the Molien formula of Brion-Vergne. Similarly, we compute the localized Hirzebruch class, extending results of Brylinski-Zhang for the localized Todd class. We also elaborate on the relation between the equivariant toric geometry via the equivariant Hirzebruch-Riemann-Roch and Euler-Maclaurin type formulae for full-dimensional simple lattice polytopes. Our results provide generalizations to arbitrary coherent sheaf coefficients, and algebraic geometric proofs of (weighted versions of) the Euler-Maclaurin formulae of Cappell-Shaneson, Brion-Vergne, Guillemin, etc., via the equivariant Hirzebruch-Riemann-Roch formalism. Our approach, based on motivic characteristic classes, allows us to obtain such Euler-Maclaurin formulae also for (the interior of) a face, or for the polytope with several facets removed. We also prove such results in the weighted context, and for Minkovski summands of the given full-dimensional lattice polytope. Some of these results are extended to local Euler-Maclaurin formulas for the tangent cones at the vertices of the given lattice polytope.Comment: 93 pages, comments are very welcom

    Mirror symmetry for Dubrovin-Zhang Frobenius manifolds

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    Frobenius manifolds were formally defined by Boris Dubrovin in the early 1990s, and serve as a bridge between a priori very different fields of mathematics such as integrable systems theory, enumerative geometry, singularity theory, and mathematical physics. This thesis concerns, in particular, a specific class of Frobenius manifolds constructed on the orbit space of an extension of the affine Weyl group defined by Dubrovin together with Youjin Zhang. Here, we find Landau-Ginzburg superpotentials, or B-model mirrors, for these Frobenius structures by considering the characteristic equation for Lax operators of relativistic Toda chains as proposed by Andrea Brini. As a bonus, the results open up various applications in topology, integrable hierarchies, and Gromov-Witten theory, making interesting research questions in these areas more accessible. Some such applications are considered in this thesis. The form of the determinant of the Saito metric on discriminant strata is investigated, applications to the combinatorics of Lyashko-Looijenga maps are given, and investigations into the integrable systems theoretic and enumerative geometric applications are commenced

    Non-perturbative topological string theory on compact Calabi-Yau 3-folds

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    We obtain analytic and numerical results for the non-perturbative amplitudes of topological string theory on arbitrary, compact Calabi-Yau manifolds. Our approach is based on the theory of resurgence and extends previous special results to the more general case. In particular, we obtain explicit trans-series solutions of the holomorphic anomaly equations. Our results predict the all orders, large genus asymptotics of the topological string free energies, which we test in detail against high genus perturbative series obtained recently in the compact case. We also provide additional evidence that the Stokes constants appearing in the resurgent structure are closely related to integer BPS invariants.Comment: 85 pages, 16 figures, 15 table

    Enumerative invariants in self-dual categories. I. Motivic invariants

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    In this series of papers, we propose a theory of enumerative invariants counting self-dual objects in self-dual categories. Ordinary enumerative invariants in abelian categories can be seen as invariants for the structure group GL(n)\mathrm{GL} (n), and our theory is an extension of this to structure groups O(n)\mathrm{O} (n) and Sp(2n)\mathrm{Sp} (2n). Examples of our invariants include invariants counting principal orthogonal or symplectic bundles, and invariants counting self-dual quiver representations. In the present paper, we take the motivic approach, and define our invariants as elements in a ring of motives. One can also extract numerical invariants from these invariants. We prove wall-crossing formulae relating our invariants for different stability conditions. We also provide an explicit algorithm computing invariants for quiver representations, and we present some numerical results.Comment: 122 page

    A Unifying Framework for Differentially Private Sums under Continual Observation

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    We study the problem of maintaining a differentially private decaying sum under continual observation. We give a unifying framework and an efficient algorithm for this problem for \emph{any sufficiently smooth} function. Our algorithm is the first differentially private algorithm that does not have a multiplicative error for polynomially-decaying weights. Our algorithm improves on all prior works on differentially private decaying sums under continual observation and recovers exactly the additive error for the special case of continual counting from Henzinger et al. (SODA 2023) as a corollary. Our algorithm is a variant of the factorization mechanism whose error depends on the γ2\gamma_2 and γF\gamma_F norm of the underlying matrix. We give a constructive proof for an almost exact upper bound on the γ2\gamma_2 and γF\gamma_F norm and an almost tight lower bound on the γ2\gamma_2 norm for a large class of lower-triangular matrices. This is the first non-trivial lower bound for lower-triangular matrices whose non-zero entries are not all the same. It includes matrices for all continual decaying sums problems, resulting in an upper bound on the additive error of any differentially private decaying sums algorithm under continual observation. We also explore some implications of our result in discrepancy theory and operator algebra. Given the importance of the γ2\gamma_2 norm in computer science and the extensive work in mathematics, we believe our result will have further applications.Comment: 32 page

    Discrete signature varieties

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    Discrete signatures are invariants computed from time series that correspond to the discretised version of the signature of paths. We study the algebraic varieties arising from their images, the discrete signature variety. We introduce them and compute their dimension in many cases. From the analysis of a particular subclass of these varieties, we also derive a partial solution to the Chen-Chow theorem in an algebraically closed setting.Comment: 24 pages, one diagra

    Map enumeration on surfaces: from bijective techniques to asymptotic counting

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    L'objectiu principal del treball és l'enumeració de mapes a superfícies orientables amb l'ús majoritari de tècniques bijectives. Deduirem la fórmula exacta per mapes planars amb n arestes amb 3 mètodes diferents. Un d'ells explica en detall la relació que hi ha entre mapes i arbres planars, a més d'oferir una base per l'enumeració de mapes en gèneres majors. En aquestes superfícies, enumerarem asimptòticament els mapes a partir d'una intel·ligent bijecció entre mapes i mapes amb una sola cara, anomenats g-trees.El objetivo principal del trabajo es la enumeración de mapas en superficies orientables con el uso mayoritario de técnicas biyectivas. Deduciremos la fórmula exacta para mapas planos con n aristas con tres métodos diferentes. Uno de ellos explica en detalle la relación que hay entre mapas y árboles planos, a más de dar una base para la enumeración de mapas en superficies de género mayor. En dichas superficies, enumeraremos asintóticamente los mapas a partir de una biyección entre mapas y mapas con una sola cara, llamados g-trees.The main objective of this work is the enumeration of maps on orientable surfaces with the use of mostly bijective techniques. We are going to deduce the exact formula for planar maps with n edges by three different methods. One of them explains in detail the relation that planar maps and trees have, in addition to giving the foundations for the enumeration of maps in higher genus surfaces. In said surfaces, we are going to asymptotically enumerate maps via a clever bijection between maps and maps with one face, which are called g-trees

    Symmetric wide-matrix varieties and powers of GL-varieties

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