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Jonathan Weitsman

Publications and source records attributed to Jonathan Weitsman.

At least 19 recordsLinked to original sources
arXiv2026

The Dual DG Category to Weinstein's symplectic "category" and applications to Geometric Quantization

In Weinstein's symplectic "category", objects are symplectic manifolds and morphisms are canonical relations, which may not be composable; it is therefore only morally a category. We construct a true differential graded category which is morally dual to Weinstein's "category". The objects in this category are prequantum systems, associated to integral symplectic manifolds. The morphisms are a complex of differential forms twisted by a prequantum line bundle. We also consider the cohomology category, which turns out to be an (ordinary) linear category. In each case, Weinstein's morphisms are associated with currents dual to the forms. For the differential graded category, these are isotropic, or if preferred Lagrangian, currents, twisted by a section of the prequantum line bundle; in the case of cohomology, these currents are supported on {\em integral} Lagrangian submanifolds, equipped with a global covariant constant section of the prequantum line bundle. We then apply our methods to quantization, and show that for Kahler manifolds, a quantization in this category is related to holomorphic quantization. Along the way we show that in the case of prequantum systems, the Lefschetz action of ${\mathfrak {sl}}(2,\R)$ on differential forms, studied by Brylinski, Mathieu, Guillemin, and Tseng-Yau in the symplectic case, is promoted to an action of the superalgebra ${\mathfrak {osp}}(1|2)$ on twisted differential forms, with ${\mathfrak {sl}}(2,\R)$ as the even subalgebra. A first application of this superalgebra action is the vanishing theorem which shows the cohomology category is supported in middle dimension.

math.SG↗
arXiv2026

Hilbert Polynomials of Calabi Yau Hypersurfaces in Toric Varieties and Lattice Points in Polytope Boundaries

We show that the Hilbert polynomial of a Calabi-Yau hypersurface $Z$ in a smooth toric variety $M$ associated to a convex polytope $\Delta$ is given by a lattice point count in the polytope boundary $\partial \Delta,$ just as the Hilbert polynomial of $M$ is known to be given by a lattice point count in the convex polytope $\Delta.$ Our main tool is a computation of the Euler class in $K$-theory of the normal line bundle to the hypersurface $Z,$ in terms of the Euler classes of the divisors corresponding to the facets of the moment polytope. We observe a remarkable parallel between our expression for the Euler class and the inclusion-exclusion principle in combinatorics. To obtain our result we combine these facts with the known relation between lattice point counts in the facets of $\Delta$ and the Hilbert polynomials of the smooth toric varieties corresponding to these facets.

math.AG↗
arXiv2025

Lattice points in polytope boundaries and formal geometric quantization of singular Calabi Yau hypersurfaces in toric varieties

We show that the number of lattice points in the boundary of a positive integer dilate of a Delzant integral polytope is a polynomial in the dilation parameter, analogous to the Ehrhart polynomial giving the number of lattice points in a lattice polytope. We give an explicit formula for this polynomial, analogous to the formula of Khovanskii-Pukhlikov for the Ehrhart polynomial. These counting polynomials satisfy a lacunarity principle, the vanishing of alternate coefficients, quite unlike the Ehrhart polynomial. We show that formal geometric quantization of singular Calabi Yau hypersurfaces in smooth toric varieties gives this polynomial, in analogy with the relation of the Khovanskii-Pukhlikov formula to the geometric quantization of toric varieties. The Atiyah-Singer theorem for the index of the Dirac operator gives a moral argument for the lacunarity of the counting polynomial. We conjecture that similar formulas should hold for arbitrary simple integral polytope boundaries.

math.CO↗
arXiv2024

Reflection Positivity and Chern-Simons Functional Integrals

We show that a mathematical version of the formal Chern-Simons functional integral of Witten for manifolds equipped with a reflection may be constructed in terms of a reflection positive functional, associated to the quadratic term in the Chern-Simons Lagrangian, on an algebra of functions on a Banach space ${\bf A}$ of connections on the underlying 3-manifold. This construction yields a Hilbert space associated to a surface preserved by the reflection. A version of the cubic Bosonic interaction term in the Chern-Simons Lagrangian gives a self-adjoint operator on this Hilbert space, and by exponentiation, a unitary one parameter subgroup of operators. The vacuum expectation value of this one parameter subgroup is combined with an additional term associated to the ghost fields and their interaction, and an appropriate weak limit gives a partition function for the quantum field theory. This construction is nonperturbative. The theory is finite and does not require renormalization, as may be expected from perturbation theory. It is natural to ask whether the resulting partition function is related to the manifold invariants of Witten and Reshetikhin-Turaev, or whether a more elaborate construction may be needed.

math-ph↗
arXiv2024

The Chern-Simons Functional Integral, Kauffman's Bracket Polynomial, and other link invariants

We study Chern-Simons Gauge Theory in axial gauge on ${\mathbb R}^3.$ This theory has a quadratic Lagrangian and therefore expectations can be computed nonperturbatively by explicit formulas, giving an (unbounded) linear functional on a space of polynomial functions in the gauge fields, as a mathematically well-defined avatar of the formal functional integral. We use differential-geometric methods to extend the definition of this linear functional to expectations of products of Wilson loops corresponding to oriented links in ${\mathbb R}^3,$ and derive skein relations for them. In the case $G=SU(2)$ we show that these skein relations are closely related to those of the Kauffman bracket polynomial, which is closely related to the Jones polynomial. We also study the case of groups of higher rank. We note that in the absence of a cubic term in the action, there is no quantization condition on the coupling $\lambda,$ which can be any complex number. This is in line with the fact that the Jones polynomial, in contrast to the manifold invariants of Witten and Reshetikhin-Turaev, is defined for any value of the coupling. The appearance of the parameter $e^{\frac1{2\lambda}}$ in the expectations and skein relations is also natural. Likewise, the extension of the theory to noncompact groups presents no difficulties. Finally we show how computations similar to ours, but for gauge fields in two dimensions, yield the Goldman bracket.

math.DG↗
arXiv2024

On deformation quantization of the space of connections on a two manifold and Chern Simons Gauge Theory

We use recent progress on Chern-Simons gauge theory in three dimensions [18] to give explicit, closed form formulas for the star product on some functions on the affine space ${\mathcal A}(\Sigma)$ of (smooth) connections on the trivialized principal $G$-bundle on a compact, oriented two manifold $\Sigma.$ These formulas give a close relation between knot invariants, such as the Kauffman bracket polynomial, and the Jones and HOMFLY polynomials, arising in Chern Simons gauge theory, and deformation quantization of ${\mathcal A}(\Sigma).$ This relation echoes the relation between the manifold invariants of Witten [20] and Reshetikhin-Turaev [16] and {\em geometric} quantization of this space (or its symplectic quotient by the action of the gauge group). In our case this relation arises from explicit algebraic formulas arising from the (mathematically well-defined) functional integrals of [18].

math.DG↗
arXiv2024

Darboux, Moser and Weinstein theorems for prequantum systems

We establish analogs of the Darboux, Moser and Weinstein theorems for prequantum systems. We show that two prequantum systems on a manifold with vanishing first cohomology, with symplectic forms defining the same cohomology class and homotopic to each other within that class, differ only by a symplectomorphism and a gauge transformation. As an application, we show that the Bohr-Sommerfeld quantization of prequantum system on a manifold with trivial first cohomology is independent of the choice of the connection.

math.SG↗
arXiv2023

The double Gelfand-Cetlin system, invariance of polarization, and the Peter-Weyl theorem

The bundle map $T^*\hspace{-2pt}\operatorname{U}(n)\longrightarrow\operatorname{U}(n)$ provides a real polarization of the cotangent bundle $T^*\hspace{-2pt}\operatorname{U}(n)$, and yields the geometric quantization $Q_1(T^*\hspace{-2pt}\operatorname{U}(n)) = L^2(\operatorname{U}(n))$. We use the Gelfand-Cetlin systems of Guillemin and Sternberg to show that $T^*\hspace{-2pt}\operatorname{U}(n)$ has a different real polarization with geometric quantization $Q_2(T^*\hspace{-2pt}\operatorname{U}(n))= \bigoplus_\alpha V_\alpha \otimes V_\alpha^*$, where the sum is over all dominant integral weights $\alpha$ of $\operatorname{U}(n)$. The Peter-Weyl theorem, which states that these two quantizations are isomorphic, may therefore be interpreted as an instance of ``invariance of polarization" in geometric quantization.

math.SG↗
arXiv2023

Abelianization and the Duistermaat-Heckman theorem

Fix a compact connected Lie group $G$ with Lie algebra $\mathfrak{g}$, as well as a strong Gelfand-Cetlin datum on $\mathfrak{g}^*$. Let us also fix a connected symplectic manifold $M$ endowed with an effective Hamiltonian $G$-action and proper moment map. We associate to such information a measure on $\mathbb{R}^{\mathrm{b}}$, where $\mathrm{b}=\frac{1}{2}(\dim G+\mathrm{rank}\hspace{2pt}G)$. We also express the Radon-Nikodym derivative of this measure in terms of the volumes of the symplectic quotients of $M$ by $G$, and thereby prove a non-abelian version of the Duistermaat-Heckman theorem.

math.SG↗
arXiv2022

Gelfand-Cetlin abelianizations of symplectic quotients

We show that generic symplectic quotients of a Hamiltonian $G$-space $M$ by the action of a compact connected Lie group $G$ are also symplectic quotients of the same manifold $M$ by a compact torus. The torus action in question arises from certain integrable systems on $\mathfrak{g}^*$, the dual of the Lie algebra of $G$. Examples of such integrable systems include the Gelfand-Cetlin systems of Guillemin-Sternberg in the case of unitary and special orthogonal groups, and certain integrable systems constructed for all compact connected Lie groups by Hoffman-Lane. Our abelianization result holds for smooth quotients, and more generally for quotients which are stratified symplectic spaces in the sense of Sjamaar-Lerman.

math.SG↗
arXiv2022

Bohr-Sommerfeld quantization of $b$-symplectic toric manifolds

We define the Bohr-Sommerfeld quantization via $T$-modules for a $b$-symplectic toric manifold and show that it coincides with the formal geometric quantization of [GMW18b]. In particular, we prove that its dimension is given by a signed count of the integral points in the moment polytope of the toric action on the manifold.

math.SG↗
arXiv2020

Towards a quantization of the double via the enhanced symplectic category

This paper considers the enhanced symplectic "category" for purposes of quantizing quasi-Hamiltonian $G$-spaces, where $G$ is a compact simple Lie group. Our starting point is the well-acknowledged analogy between the cotangent bundle $T^*G$ in Hamiltonian geometry and the internally fused double $D(G)=G\times G$ in quasi-Hamiltonian geometry. Guillemin and Sternberg consider the former, studing half-densities and phase functions on its so-called character Lagrangians $\Lambda_{\mathcal{O}}\subseteq T^*G$. Our quasi-Hamiltonian counterpart replaces these character Lagrangians with the universal centralizers $\Lambda_{\mathcal{C}}\longrightarrow\mathcal{C}$ of regular, $\frac{1}{k}$-integral conjugacy classes $\mathcal{C}\subseteq G$. We show each universal centralizer to be a "quasi-Hamiltonian Lagrangian" in $D(G)$, and to come equipped with a half-density and phase function. At the same time, we consider a Dehn twist-induced automorphism $R:D(G)\longrightarrow D(G)$ that lacks a natural Hamiltonian analogue. Each quasi-Hamiltonian Lagrangian $R(\Lambda_{\mathcal{C}})$ is shown to have a clean intersection with every $\Lambda_{\mathcal{C}'}$, and to come equipped with a half-density and phase function of its own. This leads us to consider the possibility of a well-behaved, quasi-Hamiltonian notion of the BKS pairing between $R(\Lambda_{\mathcal{C}})$ and $\Lambda_{\mathcal{C}'}$. We construct such a pairing and study its properties. This is facilitated by the nice geometric fearures of $R(\Lambda_{\mathcal{C}})\cap\Lambda_{\mathcal{C}'}$ and a reformulation of the classical BKS pairing. Our work is perhaps the first step towards a level-$k$ quantization of $D(G)$ via the enhanced symplectic "category".

math.SG↗
arXiv2018

Integrable systems on $Fl_n \times Fl_n \times Fl_n //SU(n)$ and $SU(n)$ tensor product multiplicities

We construct a densely defined torus action on the symplectic quotient of the product of three complete flag varieties. The closure of the image of the corresponding moment map is a convex polytope. The dimension of the geometric quantization of this space gives the structure constants of the representation ring of $SU(n)$, which we show is given by counting lattice points in the image of the moment map. Such lattice point formulas for the structure constants were given by Berenstein-Zelevinsky; our results show how such formulas arise geometrically as an example of `invariance of polarization', analogous to the description of the Gelfand-Cetlin polytopes by Guillemin-Sternberg. We outline applications to loop groups and to moduli spaces of vector bundles.

math.SG↗
arXiv2018

Relations in the cohomology ring of the moduli space of flat $SO(2n+1)$-connections on a Riemann surface

We consider the moduli space of flat $SO(2n+1)$-connections (up to gauge transformations) on a Riemann surface, with fixed holonomy around a marked point. There are natural line bundles over this moduli space; we construct geometric representatives for the Chern classes of these line bundles, and prove that the ring generated by these Chern classes vanishes below the dimension of the moduli space, generalising a conjecture of Newstead.

math.DG↗
arXiv2018

On geometric quantization of $b^m$-symplectic manifolds

We study the formal geometric quantization of $b^m$-symplectic manifolds equipped with Hamiltonian actions of a torus $T$ with nonzero leading modular weight. The resulting virtual $T$-modules are finite dimensional when $m$ is odd, as in [GMW2]; when $m$ is even, these virtual modules are not finite dimensional, and we compute the asymptotics of the representations for large weight.

math.SG↗
arXiv2017

Spectral curves for the triple reduced product of coadjoint orbits for SU(3)

We give an identification of the triple reduced product of three coadjoint orbits in SU(3) with a space of Hitchin pairs over a genus 0 curve with three punctures, where the residues of the Higgs field at the punctures are constrained to lie in fixed coadjoint orbits. Using spectral curves for the corresponding Hitchin system, we identify the moment map for a Hamiltonian circle action on the reduced product. Finally, we make use of results of Adams, Harnad, and Hurtubise to find Darboux coordinates and a differential equation for the Hamiltonian.

math.AG↗
arXiv2016

On geometric quantization of $b$-symplectic manifolds

We study a notion of pre-quantization for $b$-symplectic manifolds. We use it to construct a formal geometric quantization of $b$-symplectic manifolds equipped with Hamiltonian torus actions with nonzero modular weight. We show that these quantizations are finite dimensional $T$-modules.

math.SG↗