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## Open problems on billiards and geometric optics

Arnold Mathematical Journal. 2022. Vol. 8. P. 411-422.

This is a collection of problems composed by some participants of the workshop “Differential Geometry, Billiards, and Geometric Optics” that took place at CIRM on October 4–8, 2021.

Glutsyuk A., / Cornell University. Series "Working papers by Cornell University". 2021. No. 2104.01362.

Reflection in strictly convex bounded planar billiard acts on the space of oriented lines and preserves a standard area form. A caustic is a curve C whose tangent lines are reflected by the billiard to lines tangent to C. The famous Birkhoff conjecture states that the only strictly convex billiards with a foliation by closed ...

Added: November 4, 2021

Glutsyuk A., Journal of Fixed Point Theory and Applications 2022 Vol. 24 No. 2 Article 35

For a given closed convex planar curve γ with smooth boundary and a given p>0, the string construction yields a family of curves Γp for which γ is a caustic. The action of the reflection Tp on the tangent lines to γ≃S1 induces its action on the tangency points: a circle diffeomorphism Tp:γ→γ. We say ...

Added: November 4, 2021

Glutsyuk A., / Cornell University. Series "Working papers by Cornell University". 2019.

For a given closed convex planar curve γ with smooth boundary and a given p>0, the string construction yields a family of curves Γp for which γ is a caustic. The action of the reflection Tp on the tangent lines to γ≃S1 induces its action on the tangency points: a circle diffeomorphism p:γ→γ. We say ...

Added: November 12, 2019

Hutsalyuk A., Liashyk A., Pakuliak S. Z. et al., Nuclear Physics B 2018 Vol. 926 P. 256-278

We study quantum integrable models solvable by the nested algebraic Bethe ansatz and possessing gl(m|n)-invariant R-matrix. We compute the norm of the Hamiltonian eigenstates. Using the notion of a generalized model we show that the square of the norm obeys a number of properties that uniquely fix it. We also show that a Jacobian of the system ...

Added: September 13, 2018

Glutsyuk A., / Cornell University. Series arXiv "math". 2021.

Reflections from hypersurfaces act by symplectomorphisms on the space of oriented lines with respect to the canonical symplectic form. We consider an arbitrary infinitely-smooth hypersurface in Euclidean space that is either a global strictly convex closed hypersurface, or a germ of hypersurface. We deal with the pseudogroup generated by compositional ratios of reflections from it ...

Added: October 19, 2020

Gontsov R. R., V.A. Poberezhnyi, Helminck G. F., Russian Mathematical Surveys 2011 Vol. 66 No. 1 P. 63-105

This article concerns deformations of meromorphic linear differential systems. Problems relating to their existence and classification are reviewed, and the global and local behaviour of solutions to deformation equations in a neighbourhood of their singular set is analysed. Certain classical results established for isomonodromic deformations of Fuchsian systems are generalized to the case of integrable ...

Added: September 27, 2013

Poberezhny V. A., / ИТЭФ. Series "Препринты ИТЭФ". 2013. No. 18/13.

We review the modern theory of isomonodromic deformations, considering linear systems of
differential equations. On that background we illustrate the natural relations between
such phenomena as integrability, isomonodromy and Painlev\'{e} property. The recent
advances in the theory of isomonodromic deformations we present show perfect agreement to
that approach. ...

Added: March 31, 2014

Skripchenko A., Troubetzkoy S., Annales de l'Institut Fourier 2015 Vol. 65 No. 5 P. 1881-1896

We study the billiard on a square billiard table with a one-sided vertical mirror.
We associate trajectories of these billiards with double rotations and study orbit behavior and questions of complexit ...

Added: March 2, 2016

Glutsyuk A., Doklady Mathematics 2018 Vol. 98 No. 6 P. 382-385

The algebraic version of the Birkhoff conjecture is solved completely for billiards with a piecewise
$C^2$-smooth boundary on surfaces of constant curvature: Euclidean plane, sphere, and Lobachevsky plane. Namely, we obtain a complete classification of billiards for which the billiard geodesic flow has a nontrivial
first integral depending polynomially on the velocity. According to this classification, every ...

Added: August 25, 2018

Hutsalyuk A., Liashyk A, Pakuliak S. Z. et al., Nuclear Physics B 2017 Vol. 923 P. 277-311

We study scalar products of Bethe vectors in the models solvable by the nested algebraic Bethe ansatz and described by superalgebra. Using coproduct properties of the Bethe vectors we obtain a sum formula for their scalar products. This formula describes the scalar product in terms of a sum over partitions of Bethe parameters. We also obtain recursions for ...

Added: October 26, 2017

Hutsalyuk A., Liashyk A., Pakuliak S. Z. et al., Russian Mathematical Surveys 2017 Vol. 72 No. 1 P. 33-99

Bethe vectors are found for quantum integrable models associated with the supersymmetric Yangians in terms of the current generators of the Yangian double . The method of projections onto intersections of different types of Borel subalgebras of this infinite-dimensional algebra is used to construct the Bethe vectors. Calculation of these projections makes it possible to express the ...

Added: October 26, 2017

Glutsyuk A., Shustin E., Mathematische Annalen 2018 Vol. 372 P. 1481-1501

We show that every polynomially integrable planar outer convex billiard is elliptic. We also
prove an extension of this statement to non-convex billiards. ...

Added: June 29, 2018

Glutsyuk A., Ergodic Theory and Dynamical Systems 2023

Reflection in a strictly convex bounded planar billiard acts on the space of oriented lines and preserves a standard area form. A caustic is a curve C whose tangent lines are reflected by the billiard to lines tangent to C. The famous Birkhoff conjecture states that the only strictly convex billiards with a foliation by ...

Added: December 29, 2023

A.V.Zabrodin, Zotov A. V., Liashyk A. et al., Theoretical and Mathematical Physics 2017 Vol. 192 No. 2 P. 1141-1153

We discuss the correspondence between models solved by the Bethe ansatz and classical integrable systems of the Calogero type. We illustrate the correspondence by the simplest example of the inhomogeneous asymmetric six-vertex model parameterized by trigonometric(hyperbolic) functions. ...

Added: October 26, 2017

Golikova L., Зинина С. Х., Известия высших учебных заведений. Прикладная нелинейная динамика 2021 Т. 29 № 6 С. 851-862

It is known from the 1939 work of A. G. Mayer that rough transformations of the circle are limited to the
diffeomorphisms of Morse – Smale. A topological conjugacy class of orientation-preserving diffeomorphism is entirely determined by its rotation number and the number of its periodic orbits, while for orientation-changing diffeomorphism the topological invariant will be ...

Added: December 3, 2021

V. A. Poberezhny, Journal of Mathematical Sciences 2013 Vol. 195 No. 4 P. 533-540

We consider systems of linear differential equations discussing some classical and modern results in the Riemann problem, isomonodromic deformations, and other related topics. Against this background, we illustrate the relations between such phenomena as the integrability, the isomonodromy, and the Painlevé property. The recent advances in the theory of isomonodromic deformations presented show perfect agreement ...

Added: February 14, 2014

Glutsyuk A., Israel Journal of Mathematics 2023 Vol. 258 No. 1 P. 137-184

Reflections from hypersurfaces act by symplectomorphisms on the space of oriented lines with respect to the canonical symplectic form. We consider an arbitrary infinitely-smooth hypersurface in Euclidean space that is either a global strictly convex closed hypersurface, or a germ of hypersurface. We deal with the pseudogroup generated by compositional ratios of reflections from it ...

Added: November 4, 2021

Hutsalyuk A., Liashyk A., Pakuliak S. Z. et al., SciPost Physic (Нидерланды) 2018 Vol. 4 No. 006 P. 1-30

We obtain recursion formulas for the Bethe vectors of models with periodic boundary conditions solvable by the nested algebraic Bethe ansatz and based on the quantum affine algebra U_q(gl_n). We also present a sum formula for their scalar products. This formula describes the scalar product in terms of a sum over partitions of the Bethe parameters, ...

Added: September 13, 2018

Glutsyuk A., / Cornell University. Series math "arxiv.org". 2014. No. 1405.5990.

The famous conjecture of V.Ya.Ivrii says that
in every billiard with infinitely-smooth boundary in a Euclidean space
the set of periodic orbits has measure zero. In the present paper we study its
complex analytic version for quadrilateral
orbits in two dimensions, with reflections from holomorphic curves.
We present the complete classification of 4-reflective analytic
counterexamples: billiards formed by four holomorphic ...

Added: September 4, 2014

Sinelshchikov D., Physics Letters A 2020 Vol. 384 No. 26 Article 126655

In this work we consider a family of nonlinear oscillators that is cubic with respect to the first derivative. Particular members of this family of equations often appear in numerous applications. We solve the linearization problem for this family of equations, where as equivalence transformations we use generalized nonlocal transformations. We explicitly find correlations on ...

Added: June 21, 2020

Glutsyuk A., Moscow Mathematical Journal 2014 Vol. 14 No. 2 P. 239-289

The famous conjecture of V.Ya. Ivrii (1978) says that in every billiard with infinitely-smooth boundary in a Euclidean space the set of periodic orbits has measure zero. In the present paper we study the complex algebraic version of Ivrii’s conjecture for quadrilateral orbits in two dimensions, with reflections from complex algebraic curves. We present the ...

Added: September 4, 2014

Glutsyuk A., Journal of Geometric Analysis 2017 Vol. 27 No. 1 P. 183-238

The famous conjecture of Ivrii (Funct Anal Appl 14(2):98–106, 1980) says that in every billiard with infinitely-smooth boundary in a Euclidean space the set of periodic orbits has measure zero. In the present paper we study its complex analytic version for quadrilateral orbits in two dimensions, with reflections from holomorphic curves. We present the complete ...

Added: November 2, 2016

Burov A. A., Квант 2014 № 2 С. 20-21

Задача Ф2323. Решение. ...

Added: December 1, 2014

D. A. Baranov, Kosolapov E. S., O. V. Pochinka, Siberian Mathematical Journal 2023 Vol. 64 No. 4 P. 807-818

It is known that Morse–Smale diffeomorphisms with two hyperbolic periodic orbits exist
only on the sphere and they are all topologically conjugate to each other. However, if we allow three
orbits to exist then the range of manifolds admitting them widens considerably. In particular, the
surfaces of arbitrary genus admit such orientation-preserving diffeomorphisms. In this article we find
a ...

Added: July 19, 2023