Leonid Ryvkin

The purpose of this paper is to present a fully algebraic formalism for the construction and reduction of $L_\infty$-algebras of observables inspired by multisymplectic geometry, using Gerstenhaber algebras, BV-modules, and the constraint triple formalism. In the "geometric case", we reconstruct and conceptually explain the recent results of arXiv:...

We give a survey of Darboux type theorems in multisymplectic geometry. These theorems establish when a closed differential form of a certain type admits a constant-coefficient expression in some local coordinate system. Beyond the classical cases of symplectic and volume forms, 0-deformability (i.e. constancy of linear type) is typically not automa...

slides handout for a research talk titled “Constraint Algebras of Multisymplectic Observables” presented at the 19th International Young Researchers Workshop on Geometry, Dynamics and Field Theory. It outlines the transition from traditional symplectic reduction to multisymplectic geometry, discussing the formulation of constraint triples, higher o...

We give and intrinsic characterization of multisymplectic manifolds that have the linear type of density-valued symplectic forms in each tangent space, prove Darboux-type theorems for these forms and investigate their symmetries.

We construct the universal central extension of the Lie algebra of exact divergence-free vector fields, proving a conjecture by Claude Roger from 1995. The proof relies on the analysis of a Leibniz algebra that underlies these vector fields. As an application, we construct the universal central extension of the (infinite-dimensional) Lie group of e...

These lecture notes attempt to invite the reader towards the theory of singular foliations, both smooth and holomorphic. In addition to a systematic review of the foundations, and an attempt to put in order examples and several elementary constructions, we detail several recent tools developed for non-commutative geometry, in particular the holonom...

We develop a reduction scheme for the L ∞-algebra of observables on a premul-tisymplectic manifold (M, ω) in the presence of a compatible Lie algebra action g ↷ M and subset N ⊆ M. This reproduces in the symplectic setting the Poisson algebra of observables on the Marsden-Weinstein-Meyer symplectic reduced space, whenever the reduced space exists,...

We use a suitable ``fat point'' to differentiate a Lie $n$-groupoid. The result of the procedure gives us a presheaf of positively graded manifolds. We further prove that this presheaf is representible by the tangent complex of the Lie $n$-groupoid.

We introduce a novel symplectic reduction scheme for $C^\infty(M,\omega)$ that extends in a straightforward manner to the multisymplectic setting. Specifically, we exhibit a reduction of the $L_\infty$-algebra of observables on a premultisymplectic manifold $(M,\omega)$ in the presence of a compatible Lie algebra action $\mathfrak{g}\curvearrowrigh...

We introduce the holonomy of a singular leaf L of a singular foliation as a sequence of group morphisms from πn(L)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\pi _n...

We discuss the notion of basic cohomology for Dirac structures and, more generally, Lie algebroids. We then use this notion to characterize the obstruction to a variational formulation of Dirac dynamics.

We construct an $L_\infty$-algebra on the truncated canonical homology complex of a symplectic manifold, which naturally projects to the universal central extension of the Lie algebra of Hamiltonian vector fields.

An important result for regular foliations is their formal semi-local triviality near simply connected leaves. We extend this result to singular foliations for all 2-connected leaves and a wide class of 1- connected leaves by proving a semi-local Levi-Malcev theorem for the semi-simple part of their holonomy Lie algebroid.

We compare existence and equivariance phenomena for weak moment maps and homotopy moment maps in multisymplectic geometry.

We introduce the holonomy of a singular leaf $L$ of a singular foliation as a sequence of group morphisms from $\pi_n(L)$ to the $\pi_{n-1}$ of the universal Lie $\infty$-algebroid of the transverse foliation of $L$. We include these morphisms in a long exact sequence, thus relating them to the holonomy groupoid of Androulidakis and Skandalis and t...

We give a geometric description of the obstruction to the existence of homotopy comoment maps in multisymplectic geometry. We apply this description to determine the existence of comoments for multisymplectic compact group actions on spheres and provide explicit constructions for some of these comoments.

We give a geometric description of the obstruction to the existence of comoments in multisymplectic geometry. We apply this description to determine the existence of comoments for multisymplectic compact group actions on spheres and provide explicit constructions for some of these comoments. MSC-classification (2010): 53D05, 53D20, 54H15, 57S15, 5...

In this article we study multisymplectic geometry, i.e., the geometry of manifolds with a non-degenerate, closed differential form. First we describe the transition from Lagrangian to Hamiltonian classical field theories, and then we reformulate the latter in multisymplectic terms. Furthermore, we investigate basic questions on normal forms of mult...

In this article we study multisymplectic geometry, i.e., the geometry of manifolds with a non-degenerate, closed differential form. First we describe the transition from Lagrangian to Hamiltonian classical field theories, and then we reformulate the latter in multisymplectic terms. Furthermore, we investigate basic questions on normal forms of mult...

Given a vector field on a manifold M, we define a globally conserved quantity to be a differential form whose Lie derivative is exact. Integrals of conserved quantities over suitable submanifolds are constant under time evolution, the Kelvin circulation theorem being a well-known special case. More generally, conserved quantities are well-behaved u...

Given a vector field on a manifold M, we define a globally conserved quantity to be a differential form whose Lie derivative is exact. Integrals of conserved quantities over suitable submanifolds are constant under time evolution, the Kelvin circulation theorem being a well-known special case. More generally, conserved quantities are well-behaved u...

In this note we complete the calculation of the number of $GL(\mathbb R^n)$-orbits on $\Lambda^k(\mathbb R^n)^*$, by treating the cases $(n,k)= (7,4)$ and $(8,5)$ not covered in the literature. We also calculate the number of of non-degenerate and stable orbits, as they are of special interest to multisymplectic and special geometry.

The Darboux theorem in symplectic geometry implies that any two points in a connected symplectic manifold have neighbourhoods symplectomorphic to each other. The impossibility of such a theorem in the more general multisymplectic framework appears to be, at least, folkloristic, but no explicit counterexample seems to exist in the literature. In thi...

Having constructed a notion of observables for n-plectic manifolds we will now try to generalize the notions of Hamiltonian group action and co-moment maps.

Let K denote here a fixed ground field of characteristic 0. All vector spaces, linear maps and tensor products will be defined with respect to/taken over this field, unless we explicitly state otherwise. A good overview of the subject of L∞-algebras is provided in the n-lab ([12]).

Throughout this and the next chapter we fix ℝ as our ground field.

Leonid Ryvkin gives a motivated and self-sustained introduction to n-plectic geometry with a special focus on symmetries. The relevant algebraic structures from scratch are developed. The author generalizes known symplectic notions, notably observables and symmetries, to the n-plectic case, culminating in solving the existence question for co-momen...

Given a multisymplectic manifold $(M,\omega)$ and a Lie algebra $\frak{g}$ acting on it by infinitesimal symmetries, Fregier-Rogers-Zambon define a homotopy (co-)moment as an $L_{\infty}$-algebra-homomorphism from $\frak{g}$ to the observable algebra $L(M,\omega)$ associated to $(M,\omega)$, in analogy with and generalizing the notion of a co-momen...