On polynomially integrable planar outer billiards and curves with symmetry property
We show that every polynomially integrable planar outer convex billiard is elliptic.
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arXiv subjects
Alexey Glutsyuk
Publications and source records attributed to Alexey Glutsyuk.
On constrictions of phase-lock areas in model of overdamped Josephson effect and transition matrix of double confluent Heun equation
We will discuss the model of the overdamped Josephson junction in superconductivity, which is given by a family of first order non-linear ordinary differential equations on two-torus depending on three parameters: a fixed parameter $ω$ (the frequency); a pair of variable parameters $(B,A)$ (abscissa and ordinate). It is important to study the rotation number of the system as a function $ρ=ρ(B,A)$ and to describe the phase-lock areas: its level sets $L_r=\{ρ=r\}$ with non-empty interiors. They were studied by V.M.Buchstaber, O.V.Karpov, S.I.Tertychnyi, who observed in 2010 that the phase-lock areas exist only for integer values of the rotation number. It is known that each phase-lock area is a garland of infinitely many bounded domains going to infinity in the vertical direction; each two subsequent domains are separated by one point called constriction (if it does not lie in the abscissa axis). There is a conjecture stating that all the constrictions of every phase-lock area $L_r$ lie in its axis $Λ_r=\{ B=rω\}$. Another conjecture states that for any two subsequent constrictions in $L_r$ with positive ordinates the interval between them also lies in $L_r$. In the present paper we give new results partially confirming both conjectures. The main result states that the intersection $L_r\capΛ_r$ contains an explicit infinite interval of the axis $Λ_r$ (conjecturally a connected component of the latter intersection). The proof is done by studying an equivalent family of systems of second order linear differential equations on the Riemann sphere. We obtain new results on the Stokes multipliers and the transition matrix between appropriate canonical solution bases of the linear system and deduce the main result on non-linear systems on two-torus.
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Total positivity, Grassmannian and modified Bessel functions
A rectangular matrix is called totally positive, if all its minors are positive. A point of a real Grassmanian manifold $G_{l,m}$ of $l$-dimensional subspaces in $\mathbb R^m$ is called strictly totally positive, if one can normalize its Plücker coordinates to make all of them positive. The totally positive matrices and the subsets of strictly totally positive points in Grassmanian manifolds arise in many domains of mathematics, mechanics and physics. F.R.Gantmacher and M.G.Krein considered totally positive matrices in the context of classical mechanics. Total positivity was used for construction of solutions of the Kadomtsev-Petviashvili (KP) partial differential equation by T.M.Malanyuk, M.Boiti, F.Pemperini, A.Pogrebkov, Y.Kodama, L.Williams. Different problems of mathematics, mechanics and physics led to constructions of totally positive matrices due to many mathematicians, including F.R. Gantmacher, M.G.Krein, I.J.Schoenberg, S.Karlin, A.E.Postnikov and ourselves. In our case totally positive matrices were constructed for solution of problems on model of the overdamped Josephson effect in superconductivity and double confluent Heun equations. In our previous paper we have proved that certain determinants formed by modified Bessel functions of the first kind are positive on the positive semi-axis. In the present paper we give a new result: a construction of multidimensional families of totally positive matrices formed by values of modified Bessel functions with non-negative integer indices. Their columns are numerated by the indices of the modified Bessel functions, and their rows are numerated by their arguments.
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A first integrability result for Miquel dynamics
Miquel dynamics is a discrete-time dynamical system on the space of square-grid circle patterns. For biperiodic circle patterns with both periods equal to two, we show that the dynamics corresponds to translation on an elliptic curve, thus providing the first integrability result for this dynamics. The main tool is a geometric interpretation of the addition law on the normalization of binodal quartic curves.
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On families of differential equations on two-torus with all phase-lock areas
We consider two-parametric families of non-autonomous ordinary differential equations on the two-torus with the coordinates $(x,t)$ of the type $\dot x=v(x)+A+Bf(t)$. We study its rotation number as a function of the parameters $(A,B)$. The {\it phase-lock areas} are those level sets of the rotation number function $ρ=ρ(A,B)$ that have non-empty interiors. V.M.Buchstaber, O.V.Karpov, S.I.Tertychnyi have studied the case, when $v(x)=\sin x$ in their joint paper. They have observed the quantization effect: for every smooth periodic function $f(t)$ the family of equations may have phase-lock areas only for integer rotation numbers. Another proof of this quantization statement was later obtained in a joint paper by Yu.S.Ilyashenko, D.A.Filimonov, D.A.Ryzhov. This implies the similar quantization effect for every $v(x)=a\sin(mx)+b\cos(mx)+c$ and rotation numbers that are multiples of $\frac 1m$. We show that for every other analytic vector field $v(x)$ (i.e., having at least two Fourier harmonics with non-zero non-opposite degrees and nonzero coefficients) there exists an analytic periodic function $f(t)$ such that the corresponding family of equations has phase-lock areas for all the rational values of the rotation number.
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On 4-reflective complex analytic planar billiards
The famous conjecture of V.Ya.Ivrii says that {\it 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 complex analytic counterexamples: billiards formed by four holomorphic curves in the projective plane that have open set of quadrilateral orbits. This extends the previous author's result classifying 4-reflective complex planar algebraic counterexamples. We provide applications to real planar billiards: classification of 4-reflective germs of real planar $C^4$-smooth pseudo-billiards; solutions of Tabachnikov's Commuting Billiard Conjecture and the 4-reflective case of Plakhov's Invisibility Conjecture (both in two dimensions; the boundary is required to be piecewise $C^4$-smooth). We provide a survey and a small technical result concerning higher number of complex reflections.
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On quadrilateral orbits in complex algebraic planar billiards
The famous conjecture of V.Ya.Ivrii (1978) says that {\it 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 complete classification of 4-reflective algebraic counterexamples: billiards formed by four complex algebraic curves in the projective plane that have open set of quadrilateral orbits.
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On odd-periodic orbits in complex planar billiards
The famous conjecture of V.Ya.Ivrii (1978) says that {\it 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 version of Ivrii's conjecture for odd-periodic orbits in planar billiards, with reflections from complex analytic curves. We prove positive answer in the following cases: 1) triangular orbits; 2) odd-periodic orbits in the case, when the mirrors are algebraic curves avoiding two special points at infinity, the so-called isotropic points. We provide immediate applications to the real piecewise-algebraic Ivrii's conjecture and to its analogue in the invisibility theory.
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On the adjacency quantization in the equation modelling the Josephson effect
We investigate two-parametric family of non-autonomous ordinary differential equations on the two-torus $$\dot x=\frac{dx}{dt}=ν\sin x + a + s \sin t, \ a,ν,s\in\rr; \ ν\neq0 \text {is fixed},$$ that model the Josephson effect from superconductivity. We study its rotation number as a function of parameters $(a,s)$ and its {\it Arnold tongues}: the level sets of the rotation number that have non-empty interior. Its Arnold tongues have many non-typical properties: they exist only for integer rotation numbers (V.M.Buchstaber, O.V.Karpov, S.I.Tertychnyi (2010); Yu.S.Ilyashenko, D.A.Ryzhov, D.A.Filimonov (2011)); their boundaries are given by pairs of analytic curves (V.M.Buchstaber, O.V.Karpov, S.I.Tertychnyi (2004, 2012)). Numerical experiments and theoretical investigations (V.M.Buchstaber, O.V.Karpov, S.I.Tertychnyi (2006); A.V.Klimenko and O.L.Romaskevich (2012)) show that each Arnold tongue forms an infinite chain of adjacent domains separated by adjacency points and going to infinity in asymptotically vertical direction. Recent numerical experiments had also shown that the adjacencies of each Arnold tongue have one and the same integer abscissa $a$ equal to the corresponding rotation number. We prove this fact for every fixed $ν$ with $|ν|\leq1$. In the general case we prove a weaker statement: the abscissa of each adjacency point is integer; it has the same sign, as the rotation number; its modulus is no greater than that of the rotation number. The proof is based on the representation of the differential equations under consideration as projectivizations of complex linear differential equations on the Riemann sphere (V.M.Buchstaber, O.V.Karpov, S.I.Tertychnyi (2004); R.L.Foote (1998); Yu.S.Ilyashenko, D.A.Ryzhov, D.A.Filimonov (2011)), and the classical theory of complex linear equations.
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Instability of nondiscrete free subgroups in Lie groups
We study finitely-generated nondiscrete free subgroups in Lie groups. We address the following question first raised by Étienne Ghys: is it always possible to make arbitrarily small perturbation of the generators of the free subgroup in such a way that the new group formed by the perturbed generators be not free? In other words, is it possible to approximate generators of a free subgroup by elements satisfying a nontrivial relation? We prove that the answer to Ghys' question is positive and generalize this result to certain non-free subgroups. We also consider the question on the best approximation rate in terms of the minimal length of relation in the approximating group. We give an upper bound on the optimal approximation rate as $e^{-cl^κ}$, where $c>0$ is a constant, $l$ the minimal length of relation and $0.19<κ<0.2$.
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On density of horospheres in dynamical laminations
In 1985 D.Sullivan had introduced a dictionary between two domains of complex dynamics: iterations of rational functions on the Riemann sphere and Kleinian groups. The latters are discrete subgroups of the group of conformal automorphisms of the Riemann sphere. This dictionary motivated many remarkable results in both domains, starting from the famous Sullivan's no wandering domain theorem in the theory of iterations of rational functions. One of the principal objects used in the study of Kleinian groups is the hyperbolic 3- manifold associated to a Kleinian group, which is the quotient of its lifted action to the hyperbolic 3- space. M.Lyubich and Y.Minsky have suggested to extend Sullivan's dictionary by providing an analogous construction for iterations of rational functions. Namely, they have constructed a lamination by three-dimensional manifolds equipped with a continuous family with hyperbolic metrics on them (may be with singularities). The action of the rational mapping on the sphere lifts naturally up to homeomorphic action on the hyperbolic lamination that is isometric along the leaves. The action on the hyperbolic lamination admits a well-defined quotient called {\it the quotient hyperbolic lamination}. We study the arrangement of the horospheres in the quotient hyperbolic lamination. The main result says that if a rational function does not belong to a small list of exceptions (powers, Chebyshev and Lattès), then there are many dense horospheres, i.e., the horospheric lamination is topologically-transitive. We show that for "many" rational functions (hyperbolic or critically-nonrecurrent nonparabolic) the quotient horospheric lamination is minimal: each horosphere is dense.
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Stokes matrices of hypergeometric integrals
In this work we compute the Stokes matrices of the ordinary differential equation satisfied by the hypergeometric integrals associated to an arrangement of hyperplanes in generic position. This generalizes the computation done by Ramis and Duval for confluent hypergeometric functions, which correspond to the arrangement of two points on the line. The proof is based on an explicit description of a base of canonical solutions as integrals on the cones of the arrangement, and combinatorial relations between integrals on cones and on domains.
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Simple proofs of uniformization theorems
The measurable Riemann mapping theorem proved by Morrey and in some particular cases by Ahlfors, Lavrentiev and Vekua, says that any measurable almost complex structure on $\rd$ ($S^2$) with bounded dilatation is integrable: there is a quasiconformal homeomorphism of $\rd$ ($S^2$) onto $\cc$ ($\bc$) transforming the given almost complex structure to the standard one. We give an elementary proof of this theorem that is done as follows. Firstly we prove its double-periodic version: each $\ci$ almost complex structures on the two-torus can be transformed by a diffeomorphism to the standard complex structure on appropriate complex torus. The proof is based on the homotopy method for the Beltrami equation on $\td$ with parameter. (As a by-product, we present a simple proof of the Poincaré-Köbe theorem saying that each simply-connected Riemann surface is conformally equivalent to either $\bar{\cc}$, or $\cc$, or the unit disc.) Afterwards the general case is treated by $\ci$ double-periodic approximation and simple normality arguments (involving Grötzsch inequality) following the classical scheme.
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Upper bounds of topology of complex polynomials in two variables
The paper deals with a complex polynomial $H$ in two variables having - a generic highest homogeneous part (without multiple zero lines), - nonconstant lower terms. In particular, under these conditions the polynomial $H$ has at least two distinct critical values. We prove quantitative versions of this statement. Supposing $H$ appropriately normalized (by affine coordinate changes in the image and in the source) we prove upper bounds for the following quantities: - the sum of the coefficients of the lower terms; - the minimal size of a bidisc containing all the nontrivial topology of a given level curve $S_t=\{ H=t\}$; - the minimal lengths of representatives of cycles in $H_1(S_t,\zz)$ vanishing along appropriate paths from $t$ to the critical values of $H$; - the intersection indices of the latter cycles. All these results (expect for the latter bound) are used in my joint work with Yu.S.Ilyashenko "Restricted version of the Hilbert 16-th problem" (available on the arxiv). In the latter paper we obtain an explicit upper bound of the number of zeros for a wide class of Abelian integrals.
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On the monodromy group of confluenting linear equations
We consider a linear analytic ordinary differential equation with complex time having a nonresonant irregular singular point. We study it as a limit of a generic family of equations with confluenting Fuchsian singularities. In 1984 V.I.Arnold asked the following question: is it true that some operators from the monodromy group of the perturbed (Fuchsian) equation tend to Stokes operators of the nonperturbed irregular equation? Another version of this question was also independently proposed by J.-P.Ramis in 1988. We consider the case of Poincaré rank 1 only. We show (in dimension two) that generically no monodromy operator tends to a Stokes operator; on the other hand, in any dimension commutators of appropriate noninteger powers of the monodromy operators around singular points tend to Stokes operators.
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