1,024 research outputs found

    Classical and quantum algorithms for scaling problems

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    This thesis is concerned with scaling problems, which have a plethora of connections to different areas of mathematics, physics and computer science. Although many structural aspects of these problems are understood by now, we only know how to solve them efficiently in special cases.We give new algorithms for non-commutative scaling problems with complexity guarantees that match the prior state of the art. To this end, we extend the well-known (self-concordance based) interior-point method (IPM) framework to Riemannian manifolds, motivated by its success in the commutative setting. Moreover, the IPM framework does not obviously suffer from the same obstructions to efficiency as previous methods. It also yields the first high-precision algorithms for other natural geometric problems in non-positive curvature.For the (commutative) problems of matrix scaling and balancing, we show that quantum algorithms can outperform the (already very efficient) state-of-the-art classical algorithms. Their time complexity can be sublinear in the input size; in certain parameter regimes they are also optimal, whereas in others we show no quantum speedup over the classical methods is possible. Along the way, we provide improvements over the long-standing state of the art for searching for all marked elements in a list, and computing the sum of a list of numbers.We identify a new application in the context of tensor networks for quantum many-body physics. We define a computable canonical form for uniform projected entangled pair states (as the solution to a scaling problem), circumventing previously known undecidability results. We also show, by characterizing the invariant polynomials, that the canonical form is determined by evaluating the tensor network contractions on networks of bounded size

    On the Global Topology of Moduli Spaces of Riemannian Metrics with Holonomy Sp(n)\operatorname{Sp}(n)

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    We discuss aspects of the global topology of moduli spaces of hyperkähler metrics. If the second Betti number is larger than 44, we show that each connected component of these moduli spaces is not contractible. Moreover, in certain cases, we show that the components are simply connected and determine the second rational homotopy group. By that, we prove that the rank of the second homotopy group is bounded from below by the number of orbits of MBM-classes in the integral cohomology. \\ An explicit description of the moduli space of these hyperkähler metrics in terms of Torelli theorems will be given. We also provide such a description for the moduli space of Einstein metrics on the Enriques manifold. For the Enriques manifold, we also give an example of a desingularization process similar to the Kummer construction of Ricci-flat metrics on a Kummer K3K3 surface.\\ We will use these theorems to provide topological statements for moduli spaces of Ricci-flat and Einstein metrics in any dimension larger than 33. For a compact simply connected manifold NN we show that the moduli space of Ricci flat metrics on N×TkN\times T^k splits homeomorphically into a product of the moduli space of Ricci flat metrics on NN and the moduli of sectional curvature flat metrics on the torus TkT^k

    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    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

    Quantum ergodicity on the Bruhat-Tits building for PGL(3,F)\text{PGL}(3, F) in the Benjamini-Schramm limit

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    We study eigenfunctions of the spherical Hecke algebra acting on L2(Γn\G/K)L^2(\Gamma_n \backslash G / K) where G=PGL(3,F)G = \text{PGL}(3, F) with FF a non-archimedean local field of characteristic zero, K=PGL(3,O)K = \text{PGL}(3, \mathcal{O}) with O\mathcal{O} the ring of integers of FF, and (Γn)(\Gamma_n) is a sequence of cocompact torsionfree lattices. We prove a form of equidistribution on average for eigenfunctions whose spectral parameters lie in the tempered spectrum when the associated sequence of quotients of the Bruhat-Tits building Benjamini-Schramm converges to the building itself.Comment: 111 pages, 25 figures, 2 table

    Perfectoid covers of abelian varieties and the weight-monodromy conjecture

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    Deligne's weight-monodromy conjecture gives control over the poles of local factors of L-functions of varieties at places of bad reduction. His proof in characteristic p was a step in his proof of the generalized Weil conjectures. Scholze developed the theory of perfectoid spaces to transfer Deligne's proof to characteristic 0, proving the conjecture for complete intersections in toric varieties. Building on Scholze's techniques, we prove the weight-monodromy conjecture for complete intersections in abelian varieties

    Algebraic Structure of Topological and Conformal Field Theories

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    Quantum field theories (QFTs) are geometric and analytic in nature. With enough symmetry, some QFTs may admit partial or fully algebraic descriptions. Topological and conformal field theories are prime examples of such QFTs. In this thesis, the algebraic structure of 2+1D Topological Quantum Field Theories (TQFTs) and associated Conformal Field Theories (CFTs) is studied. The line operators of 2 + 1D TQFTs and their correlation functions are captured by an algebraic structure called a Modular Tensor Category (MTC). A basic property of line operators is their operator product expansion. This is captured by the fusion rules of the MTC. We study the existence and consequences of special fusion rules where two line operators fuse to give a unique outcome. There is a natural action of a Galois group on MTCs which allows us to jump between points in the space of TQFTs. We study how the physical properties of a TQFT like its symmetries and gapped boundaries transform under Galois action. We also study how Galois action interacts with other algebraic operations on the space of TQFTs like gauging and anyon condensation. Moreover, we show that TQFTs which are invariant under Galois action are very special. Such Galois invariant TQFTs can be constructed from gauging symmetries of certain simple abelian TQFTs. TQFTs also admit gapless boundaries. In particular, 1+1D Rational CFTs (RCFTs) and 2+1D TQFTs are closely related. Given a chiral algebra, the consistent partition functions of an RCFT are classified by surface operators in the bulk 2 + 1D TQFT. On the other hand, Narain RCFTs can be constructed from quantum error-correcting codes (QECCs). We give a general map from Narain RCFTs to QECCs. We explore the role of topological line operators of the RCFT in this construction and use this map to give a quantum code theoretic interpretation of orbifolding

    Chern classes of linear submanifolds with application to spaces of k-differentials and ball quotients

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    We provide formulas for the Chern classes of linear submanifolds of the moduli spaces of Abelian differentials and hence for their Euler characteristic. This includes as special case the moduli spaces of k-differentials, for which we set up the full intersection theory package and implement it in the sage-program diffstrata. As an application, we give an algebraic proof of the theorems of Deligne-Mostow and Thurston that suitable compactifications of moduli spaces of k-differentials on the 5-punctured projective line with weights satisfying the INT-condition are quotients of the complex two-ball

    Computation and Physics in Algebraic Geometry

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    Physics provides new, tantalizing problems that we solve by developing and implementing innovative and effective geometric tools in nonlinear algebra. The techniques we employ also rely on numerical and symbolic computations performed with computer algebra. First, we study solutions to the Kadomtsev-Petviashvili equation that arise from singular curves. The Kadomtsev-Petviashvili equation is a partial differential equation describing nonlinear wave motion whose solutions can be built from an algebraic curve. Such a surprising connection established by Krichever and Shiota also led to an entirely new point of view on a classical problem in algebraic geometry known as the Schottky problem. To explore the connection with curves with at worst nodal singularities, we define the Hirota variety, which parameterizes KP solutions arising from such curves. Studying the geometry of the Hirota variety provides a new approach to the Schottky problem. We investigate it for irreducible rational nodal curves, giving a partial solution to the weak Schottky problem in this case. Second, we formulate questions from scattering amplitudes in a broader context using very affine varieties and D-module theory. The interplay between geometry and combinatorics in particle physics indeed suggests an underlying, coherent mathematical structure behind the study of particle interactions. In this thesis, we gain a better understanding of mathematical objects, such as moduli spaces of point configurations and generalized Euler integrals, for which particle physics provides concrete, non-trivial examples, and we prove some conjectures stated in the physics literature. Finally, we study linear spaces of symmetric matrices, addressing questions motivated by algebraic statistics, optimization, and enumerative geometry. This includes giving explicit formulas for the maximum likelihood degree and studying tangency problems for quadric surfaces in projective space from the point of view of real algebraic geometry

    Augmentation varieties and disk potentials

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    We elaborate on a suggestion of Aganagic-Ekholm-Ng-Vafa, that in order for Lagrangian fillings such as the Harvey-Lawson filling to define augmentations of Chekanov-Eliashberg differential graded algebras, one should count configurations of holomorphic disks connected by gradient trajectories. We propose a definition of the Chekanov-Eliashberg dga in higher dimensions which includes as generators both Reeb chords and the space of chains on the Legendrian, similar to the definition of immersed Lagrangian Floer theory whose generators are chains on the Lagrangian as well as self-intersection points. We prove that for connected Legendrian covers of monotone Lagrangian tori, the augmentation variety in this model is equal to the image of the zero level set of the disk potential, as suggested by Dimitroglou-Rizell-Golovko. In particular, we show that Legendrian lifts of Vianna's exotic tori are not Legendrian isotopic, as conjectured in Dimitroglou-Rizell-Golovko. Using related ideas, we show that the Legendrian lift of the Clifford torus admits no exact fillings, extending the results of Dimitroglou-Rizell and Treumann-Zaslow in dimension two. We consider certain disconnected Legendrians, and show, similar to another suggestion of Aganagic-Ekholm-Ng-Vafa, that the components of the augmentation variety correspond to certain partitions and each component is defined by a (not necessarily exact) Lagrangian filling. An adaptation of the theory of holomorphic quilts shows that the cobordism maps associated to bounding chains are independent of all choices up to chain homotopy.Comment: 157 page
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