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Elizabeth Gasparim

Publications and source records attributed to Elizabeth Gasparim.

At least 37 records · Page 2Linked to original sources

20 open questions about deformations of compactifiable manifolds

Deformation theory of complex manifolds is a classical subject with recent new advances in the noncompact case using both algebraic and analytic methods. In this note, we recall some concepts of the existing theory and introduce new notions of deformations for manifolds with boundary, for compactifiable manifolds, and for $q$-concave spaces. We highlight some of the possible applications and give a list of open questions which we intend as a guide for further research in this rich and beautiful subject.

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Curvature Grafted by Instantons

We show that an instanton with high charge can provoke the creation of extra curvature on the space that holds it. Geometrically, this corresponds to a new surgery operation, which we name grafting. Curvature around a sphere increases by grafting when the charge of an instanton decays.

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Morse functions and Real Lagrangian Thimbles on Adjoint Orbits

We compare Lagrangian thimbles for the potential of a Landau-Ginzburg model to the Morse theory of its real part. We explore Landau-Ginzburg models defined using Lie theory, constructing their real Lagrangian thimbles explicitly and comparing them to the stable and unstable manifolds of the real gradient flow.

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Infinitesimally Tight Lagrangian Orbits

We describe isotropic orbits for the restricted action of a subgroup of a Lie group acting on a symplectic manifold by Hamiltonian symplectomorphisms and admitting an Ad*-equivariant moment map. We obtain examples of Lagrangian orbits of complex flag manifolds, of cotangent bundles of orthogonal Lie groups, and of products of flags. We introduce the notion of infinitesimally tight and study the intersection theory of such Lagrangian orbits, giving many examples.

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Deformations of Noncompact Calabi-Yau threefolds

We describe deformations of the noncompact Calabi-Yau threefolds $W_k = \mbox{Tot}(\mathcal{O}_{\mathbb{P}^1}(-k) \oplus \mathcal{O}_{\mathbb{P}^1}(k-2))$ for $k=1,2,3$, as well as their moduli of holomorphic vector bundles of rank $2$. Deformations are computed concretely by calculations of $H^1(W_k, TW_k)$. Information about the moduli of vector bundles is obtained by analysing bundles that are extensions of line bundles. We show that for each $k=1,2,3$ the associated structures are qualitatively different, and we also comment on their difference from the analogous structures for the simpler noncompact twofolds $\mbox{Tot}(\mathcal{O}_{\mathbb{P}^1}(-k))$ which had been studied previously by the authors. We describe deformations of the noncompact Calabi-Yau threefolds $W_k = \textrm{Tot}(\mathcal{O}_{\mathbb{P}^1}(-k) \oplus \mathcal{O}_{\mathbb{P}^1}(k-2))$ for $k=1,2,3$. We compute deformations concretely by calculations of $\textrm{H}^1(W_k, TW_k)$ via Čech cohomology. We show that for each $k=1,2,3$ the associated structures are qualitatively different, and we also comment on their difference from the analogous structures of simpler noncompact twofolds $\textrm{Tot}(\mathcal{O}_{\mathbb{P}^1}(-k))$.

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Classical deformations of noncompact surfaces and their moduli of instantons

We describe semiuniversal deformation spaces for the noncompact surfaces $Z_k := \operatorname{Tot} (\mathcal O_{\mathbb P^1} (-k))$ and prove that any nontrivial deformation $Z_k (τ)$ of $Z_k$ is affine. It is known that the moduli spaces of instantons of charge $j$ on $Z_k$ are quasi-projective varieties of dimension $2j-k-2$. In contrast, our results imply that the moduli spaces of instantons on any nontrivial deformation $Z_k (τ)$ are empty.

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A Lie theoretical construction of a Landau-Ginzburg model without projective mirrors

We describe the Fukaya-Seidel category of a Landau-Ginzburg model LG(2) for the semisimple adjoint orbit of sl(2,C). We prove that this category is equivalent to a full triangulated subcategory of the category of coherent sheaves on the second Hirzebruch surface. We show that no projective variety can be mirror to LG(2), and that this remains so after compactification.

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Compactifications of Adjoint Orbits and their Hodge Diamonds

A recent theorem of [GGSM1] showed that adjoint orbits of semisimple Lie algebras have the structure of symplectic Lefschetz fibrations. We investigate the behaviour of their fibrewise compactifications. Expressing adjoint orbits and fibres as affine varieties in their Lie algebra, we compactify them to projective varieties via homogenisation of the defining ideals. We find that their Hodge diamonds vary wildly according to the choice of homogenisation, and that extensions of the potential to the compactification must acquire degenerate singularities.

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Self-Duality for Landau--Ginzburg models

P. Clarke describes mirror symmetry as a duality between Landau--Ginzburg models, so that the dual of an LG model is another LG model. We describe examples in which the underlying space is a total space of a vector bundle on the projective line, and we show that self-duality occurs in precisely two cases: the cotangent bundle and the resolved conifold.

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Hodge Diamonds and Adjoint Orbits

We present a Macaulay2 package that produces compactifications of adjoint orbits and of the fibres of symplectic Lefschetz fibrations on them. We use Macaulay2 functions to calculate the corresponding Hodge diamonds, which then reveal topological information about the Lefschetz fibrations.

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Isomorphisms of Moduli Spaces

We give infinitely many new isomorphisms between moduli spaces of bundles on local surfaces and on local Calabi--Yau threefolds.

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BPS state counting on singular varieties

We define new partition functions for theories with targets on toric singularities via products of old partition functions on crepant resolutions. We compute explicit examples and show that the new partition functions turn out to be homogeneous on MacMahon factors.

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Moduli Stacks of Bundles on Local Surfaces

We give an explicit groupoid presentation of certain stacks of vector bundles on formal neighborhoods of rational curves inside algebraic surfaces. The presentation involves a Möbius type action of an automorphism group on a space of extensions.

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Sheaves on singular varieties

We prove existence of reflexive sheaves on singular surfaces and threefolds with prescribed numerical invariants and study their moduli.

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Vector bundles near negative curves: moduli and local Euler characteristic

We study moduli spaces of vector bundles on a two-dimensional neighbourhood $Z_k$ of an irreducible curve $\ell = CP^1$ with $\ell^2 = -k$ and give an explicit construction of these moduli as stratified spaces. We give sharp bounds for the local holomorphic Euler characteristic of bundles on $Z_k$ and prove existence of families of bundles with prescribed numerical invariants. Our numerical calculations are performed using a Macaulay 2 algorithm, which is available for download at http://www.maths.ed.ac.uk/~s0571100/Instanton/ .

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