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Vladimir Roubtsov

Publications and source records attributed to Vladimir Roubtsov.

8 recordsLinked to original sources
arXiv2026

Characteristic classes on a noncommutative background: a new approach

We introduce analogues of partial derivatives with respect to the generators of the enveloping algebras U(gl(N)) and their q-deformations, the so-called modified reflection equation algebras. Using these quantum partial derivatives, we introduce the corresponding differential algebras, define the quantum de Rham operator, and exhibit the Leibniz rule for its action. Our Leibniz rule differs from its classical analogue and stems from the construction of a quantum double. In the case of the algebra U(gl(N)), we present another form of the Leibniz rule that is more convenient for prolonging the differential calculus to certain extensions of this algebra. We then use analogues of the Cayley-Hamilton identity for the generating matrices of U(gl(N)) and of reflection equation algebras to construct projective modules over these algebras. For these projective modules, we introduce Grassmannian connections and define the corresponding Chern classes.

math.QA↗
arXiv2023

Moduli spaces of vector bundles on a curve and opers

Let $X$ be a compact connected Riemann surface of genus $g$, with $g\, \geq\,2$, and let $\xi$ be a holomorphic line bundle on $X$ with $\xi^{\otimes 2}\,=\, {\mathcal O}_X$. Fix a theta characteristic $\mathbb L$ on $X$. Let ${\mathcal M}_X(r,\xi)$ be the moduli space of stable vector bundles $E$ on $X$ of rank $r$ such that $\bigwedge^r E\,=\, \xi$ and $H^0(X,\, E\otimes{\mathbb L})\,=\, 0$. Consider the quotient of ${\mathcal M}_X(r,\xi)$ by the involution given by $E\, \longmapsto\, E^*$. We construct an algebraic morphism from this quotient to the moduli space of ${\rm SL}(r,{\mathbb C})$ opers on $X$. Since $\dim {\mathcal M}_X(r,\xi)$ coincides with the dimension of the moduli space of ${\rm SL}(r,{\mathbb C})$ opers, it is natural to ask about the injectivity and surjectivity of this map.

math.AG↗
arXiv2021

Vector bundles and connections on Riemann surfaces with projective structure

Let ${\mathcal B}_g(r)$ be the moduli space of triples of the form $(X,\, K^{1/2}_X,\, F)$, where $X$ is a compact connected Riemann surface of genus $g$, with $g\, \geq\, 2$, $K^{1/2}_X$ is a theta characteristic on $X$, and $F$ is a stable vector bundle on $X$ of rank $r$ and degree zero. We construct a $T^*{\mathcal B}_g(r)$--torsor ${\mathcal H}_g(r)$ over ${\mathcal B}_g(r)$. This generalizes on the one hand the torsor over the moduli space of stable vector bundles of rank $r$, on a fixed Riemann surface $Y$, given by the moduli space of holomorphic connections on the stable vector bundles of rank $r$ on $Y$, and on the other hand the torsor over the moduli space of Riemann surfaces given by the moduli space of Riemann surfaces with a projective structure. It is shown that ${\mathcal H}_g(r)$ has a holomorphic symplectic structure compatible with the $T^*{\mathcal B}_g(r)$--torsor structure. We also describe ${\mathcal H}_g(r)$ in terms of the second order matrix valued differential operators. It is shown that ${\mathcal H}_g(r)$ is identified with the $T^*{\mathcal B}_g(r)$--torsor given by the sheaf of holomorphic connections on the theta line bundle over ${\mathcal B}_g(r)$.

math.AG↗
arXiv2020

Poisson and Symplectic structures, Hamiltonian action, momentum and reduction

This manuscript is essentially a collection of lecture notes which were given by the first author at the Summer School Wisl-2019, Poland and written down by the second author. As the title suggests, the material covered here includes the Poisson and symplectic structures (Poisson manifolds, Poisson bi-vectors and Poisson brackets), group actions and orbits (infinitesimal action, stabilizers and adjoint representations), moment maps, Poisson and Hamiltonian actions. Finally, the phase space reduction is also discussed. The very last section introduces the Poisson-Lie structures along with some related notions. This text represents a brief review of a well-known material citing standard references for more details. The exposition is concise, but pedagogical. The Authors believe that it will be useful as an introductory exposition for students interested in this specific topic.

math.DG↗
arXiv2017

Noncommutative Painlev\'e equations and systems of Calogero type

All Painlev\'e equations can be written as a time-dependent Hamiltonian system, and as such they admit a natural generalization to the case of several particles with an interaction of Calogero type (rational, trigonometric or elliptic). Recently, these systems of interacting particles have been proved to be relevant in the study of $\beta$-models. An almost two decade old open question by Takasaki asks whether these multi-particle systems can be understood as isomonodromic equations, thus extending the Painlev\'e correspondence. In this paper we answer in the affirmative by displaying explicitly suitable isomonodromic Lax pair formulations. As an application of the isomonodromic representation we provide a construction based on discrete Schlesinger transforms, to produce solutions for these systems for special values of the coupling constants, starting from uncoupled ones; the method is illustrated for the case of the second Painlev\'e equation.

math-ph↗
arXiv2015

Monge-Ampère Structures and the Geometry of Incompressible Flows

We show how a symmetry reduction of the equations for incompressible hydrodynamics in three dimensions leads naturally to a Monge-Ampère structure, and Burgers'-type vortices are a canonical class of solutions associated with this structure. The mapping of such solutions, which are characterised by a linear dependence of the third component of the velocity on the coordinate defining the axis of rotation, to solutions of the incompressible equations in two dimensions is also shown to be an example of a symmetry reduction The Monge-Ampère structure for incompressible flow in two dimensions is shown to be hypersymplectic.

math-ph↗
arXiv2005

K"ahler Geometry and the Navier-Stokes Equations

We study the Navier-Stokes and Euler equations of incompressible hydrodynamics in two and three spatial dimensions and show how the constraint of incompressiblility leads to equations of Monge--Ampère type for the stream function, when the Laplacian of the pressure is known. In two dimensions a Kähler geometry is described, which is associated with the Monge--Ampère problem. This Kähler structure is then generalised to `two-and-a-half dimensional' flows, of which Burgers' vortex is one example. In three dimensions, we show how a generalized Calabi--Yau structure emerges in a special case.

nlin.SI↗