Eugene Gutkin
We introduce the concepts of rotation numbers and rotation vectors for billiard maps. Our approach is based on the birkhoff ergodic theorem. We anticipate that it will be useful, in particular, for the purpose of establishing the non-ergodicity of billiard in certain domains.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
继续探索
We present a game inspired by research on the possible number of billiard ball collisions in the whole Euclidean space. One player tries to place $n$ static "balls" with zero radius (i.e., points) in a way that will minimize the total number of possible collisions caused by the cue ball. The other player tries to find initial conditions for the cue ball to maximize the number of collisions. The value of the game is $\sqrt{n}$ (up to constants). The lower bound is based on the Erdős-Szekeres Theorem. The upper bound may be considered a generalization of the Erdős-Szekeres Theorem.
Recently were introduced physical billiards where a moving particle is a hard sphere rather than a point as in standard mathematical billiards. It has been shown that in the same billiard tables the physical billiards may have totally different dynamics than mathematical billiards. This difference appears if the boundary of a billiard table has visible singularities (internal corners if the billiard table is two-dimensional), i.e. the particle may collide with these singular points. Here, we consider the collision of a hard ball with a visible singular point and demonstrate that the motion of …
We give a new upper bound $K_+$ on the number of totally elastic collisions of $n$ hard spheres with equal radii and equal masses in $R^d$. Our bound satisfies $\log K_+ \leq c(d) n \log n$.
We consider a billiard in the plane with periodic configuration of convex scatterers. This system is recurrent, in the sense that almost every orbit comes back arbitrarily close to the initial point. In this paper we study the time needed to get back in an r-ball about the initial point, in the phase space and also for the position, in the limit when r->0. We establish the existence of an almost sure convergence rate, and prove a convergence in distribution for the rescaled return times.
Lyapunov Exponents for Open Billiards in the Exterior of Balls
针对 $\R^3$ 中满足无食条件且球心共面、半径相对间距较小的至少三个球外开放台球流，证明其非游荡集上任意 Gibbs 测度的两个正 Lyapunov 指数严格不同。
We consider systems of "pinned balls," i.e., balls that have fixed positions and pseudo-velocities. Pseudo-velocities change according to the same rules as those for velocities of totally elastic collisions between moving balls. The times of collisions for different pairs of pinned balls are chosen in an exogenous way. We give an explicit upper bound for the maximum number of pseudo-collisions for a system of $n$ pinned balls in a $d$-dimensional space, in terms of $n$, $d$ and the locations of ball centers. As a first step, we study foldings, i.e., mappings that formalize the idea of folding …
We consider systems of "pinned balls," i.e., balls that have fixed positions and pseudo-velocities. Pseudo-velocities change according to the same rules as those for velocities of totally elastic collisions between moving balls. The times of possible pseudo-collisions for different pairs of pinned balls are chosen in an exogenous way. We give an explicit upper bound for the maximum number of pseudo-collisions for a system of $n$ pinned balls in a $d$-dimensional space. The proof is based on analysis of foldings, i.e., mappings that formalize the idea of folding a piece of paper along a crease.…
What Do Bouncing Balls Tell Us About the Universe? A Journey into Billiard Systems
本文以台球系统为研究对象，探讨其在经典（如台球桌）和量子（如电子尺度）场景下的表现，分析不同桌形引发的规则周期性或混沌行为，揭示该简单系统对理解经典与量子尺度自然行为的基础价值。
The winning rule of billiards is to drive the billiard ball on the table into the designated holes. We try to study the trajectory of the billiard ball, so that we can predict the direction of the ball. For rational slopes, we got cutting sequence by setting up the square torus. We simplified cutting sequence using shearing and flipping and we obtain the transformation between trajectory slope and cutting sequence. For irrational slopes, we look at some properties of Sturmian sequence, which help us distinguish between cutting sequence and Sturmian sequence. In conclusion, in the case of diffe…
We establish a connection between capillary floating in neutral equilibrium and the billiard ball problem. This allows us to reduce the question of floating in neutral equilibrium at any orientation with a prescribed contact angle for infinite homogeneous cylinders to a question about billiard caustics for their orthogonal cross-sections. We solve the billiard problem. As an application, we characterize the possible contact angles and exhibit an infinite family of real analytic non-round cylinders that float in neutral equilibrium at any orientation with constant contact angles.
We investigate the rotation sets of open billiards in $\mathbb{R}^N$ for the natural observable related to a starting point of a given billiard trajectory. We prove that the general rotation set is convex and the set of all convex combinations of rotation vectors of periodic trajectory $P_ϕ$ is dense in it. We provide a constructive proof which illustrates that the set $P_ϕ$ is dense in the pointwise rotation set, and the closure of the pointwise rotation set is convex. We also consider a class of billiards consisting of three obstacles and construct a sequence in the symbol space such that it…
In this paper, we discuss rotation number on the invariant curve of a one parameter family of outer billiard tables. Given a convex polygon $η$, we can construct an outer billiard table $T$ by cutting out a fixed area from the interior of $η$. $T$ is piece-wise hyperbolic and the polygon $η$ is an invariant curve of $T$ under the billiard map $ϕ$. We will show that, if $β$ is a periodic point under the outer billiard map with rational rotation number $τ= p / q$, then the $n$th iteration of the billiard map is not the local identity at $β$. This proves that the rotation number $τ$ as a function…
Computing Periodic Billiard Orbits in $L^p$ Balls via Newton's Method and Smale's $α$-Criterion
本研究提出一种结合牛顿法与Smale α准则的计算方法，可高效寻找并严格验证$L^p$球中的周期台球轨道，实验发现了远超伯克霍夫定理保证数量的轨道及相关结构规律。
For billiards with $N$ obstacles on a torus, we study the behavior of specific kind of its trajectories, \emph{the so called admissible trajectories}. Using the methods developed in \cite{1}, we prove that the \emph{admissible rotation set} is convex, and the periodic trajectories of admissible type are dense in the admissible rotation set. In addition, we show that the admissible rotation set is a proper subset of the general rotation set.
First integrals of dense hard-ball gases
本文针对Kozlov提出的台球系统动量多项式型首次积分的两个问题展开研究，明确了有界多面体台球积分的位置独立性，以及矩形箱硬球气体在碰撞图连通时首次积分与总动能多项式的关系。
This work results from our attempts to solve Boltzmann-Sinai's hypothesis about the ergodicity of hard ball gases. A crucial element in the studies of the dynamics of hard balls is the analysis of special hypersurfaces in the phase space consisting of degenerate trajectories (which lack complete hyperbolicity). We prove that if a flow-invariant hypersurface $J$ in the phase space of a semi-dispersing billiard has a negative Lyapunov function, then the volume of the forward image of $J$ grows at least linearly in time. Our proof is independent of the solution of the Boltzmann-Sinai hypothesis, …
Rotating rod and ball
该研究针对平面上匀速旋转无限长杆与弹性碰撞小球的力学系统，证明了给定初值时运动的存在唯一性，划分出5种运动类型，并明确了碰撞间隔与碰撞点间距的渐近行为。
Star-shaped trajectories of certain billiards around a triangle
本研究在Beltrami-Klein模型框架下，基于已有研究考察双曲平面中三角形外台球映射旋转数为2/5的情况，给出充分条件并证明其对大等腰三角形的必要性，最后提出相关猜想。
Traditionally, rotation numbers for toroidal billiard flows are defined as the limiting vectors of average displacements per time on trajectory segments. Naturally, these creatures are living in the (commutative) vector space $\real^n$, if the toroidal billiard is given on the flat $n$-torus. The billard trajectories, being curves, oftentimes getting very close to closed loops, quite naturally define elements of the fundamental group of the billiard table. The simplest non-trivial fundamental group obtained this way belongs to the classical Sinai billiard, i.e., the billiard flow on the 2-toru…
We compare the results of our earlier paper on the floating in neutral equilibrium at arbitrary orientation in the sense of Finn-Young with the literature on its counterpart in the sense of Archimedes. We add a few remarks of personal and social-historical character.
We consider a strictly convex billiard table with $C^2$ boundary, with the dynamics subjected to random perturbations. Each time the billiard ball hits the boundary its reflection angle has a random perturbation. The perturbation distribution corresponds to the physical situation where either the scale of the surface irregularities is smaller than but comparable to the diameter of the reflected object, or the billiard ball is not perfectly rigid. We prove that for a large class of such perturbations the resulting Markov chain is uniformly ergodic, although this is not true in general.
In Galperin billiards, two balls colliding with a hard wall form an analog calculator for the digits of the number $π$. This classical, one-dimensional three-body system (counting the hard wall) calculates the digits of $π$ in a base determined by the ratio of the masses of the two particles. This base can be any integer, but it can also be an irrational number, or even the base can be $π$ itself. This article reviews previous results for Galperin billiards and then pushes these results farther. We provide a complete explicit solution for the balls' positions and velocities as a function of th…
Pinned Billiard Balls Simulation (WXML Autumn 2023 report)
本研究通过大量模拟探究两种固定台球构型的动力学特性，验证了半空间构型下能量长期集中于边界、平坦环面构型下速度分量为独立同分布正态且碰撞方向速度分量不相关的结论。
Non-Birkhoff periodic orbits in symmetric billiards
本文研究了对称平面弹奏器中非Birkhoff周期轨道的存在性，并给出了其存在条件及计算方法。
Elliptic non-degeneracy and spectral rigidity of classical billiards
该研究证明椭球上经典型Liouville台球桌的台球映射在椭圆不动点处非退化，并由此推导出一个谱刚性结果。
On the existence of periodic invariant curves for analytic families of twist maps and billiards
本文证明环面扭转映射解析族中给定旋转数的周期不变曲线要么对所有参数值存在，要么至多存在于离散子集中，并将此结论推广并应用于台球的有理焦散线模型。
Traditionally, rotation numbers for toroidal billiard flows are defined as the limiting vectors of average displacements per time on trajectory segments. The billard trajectories, being curves, oftentimes getting very close to closed loops, quite naturally define elements of the fundamental group of the billiard table. The simplest non-trivial fundamental group obtained this way belongs to the classical Sinai billiard, i.e., the billiard flow on the 2-torus with a single, convex obstacle removed. This fundamental group is known to be the group $\textbf{F}_2$ freely generated by two elements, w…
This article is concerned with the study of Mather's β-function associated to Birkhoff billiards. This function corresponds to the minimal average action of orbits with a prescribed rotation number and, from a different perspective, it can be related to the maximal perimeter of periodic orbits with a given rotation number, the so-called Marked length spectrum. After having recalled its main properties and its relevance to the study of the billiard dynamics, we stress its connections to some intriguing open questions: Birkhoff conjecture and the isospectral rigidity of convex billiards. Both th…
Nonholonomic billiards and bounded motion in cylinders
本文提出非守恒弹跳系统作为非滑动弹跳系统的近似方法，通过数值案例研究探讨其在圆柱体内弹跳动力学中的应用。
In this paper we study the homotopical rotation vectors and the homotopical rotation sets for the billiard flow on the unit flat torus with three, mutually intersecting and mutually orthogonal cylindrical scatterers removed from it. The natural habitat for these objects is the infinite cone erected upon the Cantor set $\text{Ends}(\textbf{F}_3)$ of all "ends" of the hyperbolic group $\textbf{F}_3=π_1(\mathbf{Q})$. An element of $\text{Ends}(\textbf{F}_3)$ describes the direction in (the Cayley graph of) the group $\textbf{F}_3$ in which the considered trajectory escapes to infinity, whereas th…
We study the homotopical rotation vectors and the homotopical rotation sets for the billiard flow on the unit flat torus with two, disjoint and orthogonal cylindrical scatterers removed from it. The natural habitat for these objects is the infinite cone erected upon the Cantor set $\text{Ends}(G)$ of all "ends" of the hyperbolic group $G=π_1(\mathbf{Q})$. An element of $\text{Ends}(G)$ describes the direction in (the Cayley graph of) the group $G$ in which the considered trajectory escapes to infinity, whereas the height function $s$ ($s\ge 0$) of the cone gives us the average speed at which t…
We investigate the rotation sets of billiards on the $m$-dimensional torus with one small convex obstacle and in the square with one small convex obstacle. In the first case the displacement function, whose averages we consider, measures the change of the position of a point in the universal covering of the torus (that is, in the Euclidean space), in the second case it measures the rotation around the obstacle. A substantial part of the rotation set has usual strong properties of rotation sets.
A periodic orbit on a frictionless billiard table is a piecewise linear path of a billiard ball that begins and ends at the same point with the same angle of incidence. The period of a primitive periodic orbit is the number of times the ball strikes a side of the table as it traverses its trajectory exactly once. In this paper we find and classify the periodic orbits on a billiard table in the shape of a 120-isosceles triangle, a 60-rhombus, a 60-90-120-kite, and a 30-right triangle. In each case, we use the edge tessellation (also known as tiling) of the plane generated by the figure to unfol…
We consider billiard ball motion in a convex domain of a constant curvature surface influenced by the constant magnetic field. We prove that if the billiard map is totally integrable then the boundary curve is necessarily a circle. This result is a manifestation of the so-called Hopf rigidity phenomenon which was recently obtained for classical billiards on constant curvature surfaces.
Chaoticity of generic analytic convex billiards
研究揭示了一般解析强凸弹跳系统在混沌性方面的特性，证明了对于任意有理数p/q∈Q∩(0,1)，最大周期轨道的稳定和不稳定流形交点均为横截的，表明系统具有最大混沌性。
Billiards with singular invariant curves
研究台球映射中旋转数为1/2的不变曲线正则性，通过修改经典弦构造，构造出具有可控奇点的严格凸光滑台球及定宽台球扰动，使其具有奇异不变曲线。
Given a domain or, more generally, a Riemannian manifold with boundary, a billiard is the motion of a particle when the field of force is absent. Trajectories of such a motion are geodesics inside the domain; and the particle reflects from the boundary making the angle of incidence equal the angle of reflection. The billiard motion can happen to be a closed (or periodic) one when the billiard ball rebounds k times and then gets to the initial position with the same speed vector as in the beginning. The study of closed billiard trajectories is due to George Birkhoff who in 1927 proved a lower e…
Crossing Numbers of Billiard Curves in the Multidimensional Box via Translation Surfaces
本文研究两两可公度边长的 $n$ 维长方体中沿 $(1,\ldots,1)$ 方向运动的台球曲线，利用代数与数论方法将其交点数对应到约束满足问题的赋值数，证明任一点交点数为 $0$ 或 $2$ 的幂。
Periodic orbits for square and rectangular billiards
本文研究方形与矩形数学台球，分类其周期轨道，证明碰撞数必为偶数，并将轨道类别数联系到 Euler 函数，同时分析给定碰撞数的构造及终止于角点的奇异轨迹。
Asymptotic Homotopical Complexity of an Infinite Sequence of Dispersing $2D$ Billiards
研究了一类发散型二维台球无穷序列的大尺度混沌拓扑结构，获得了旋转集的有效径向边界、容许旋转集的紧致性与稠密性，以及拓扑熵和度量熵的精确渐近估计。
Dan Reznik found, by computer experimentation, a number of conserved quantities associated with periodic billiard trajectories in ellipses. We prove some of his observations using a non-standard generating function for the billiard ball map. In this way, we also obtain some identities valid for all smooth convex billiard tables.
In this paper we are interested in the motion of a ball inside a billiard table bounded by a particular smooth curve. This table belongs to a family of billiards which can all be drawn by a common process: the so-called gardener's string construction. The classical elliptical billiard is, of course, the foremost member of this family. So it should come as no surprise that our hexagonal string billiard shares many basic properties with the latter, but, on the other hand, also exhibits some essential differences with it. We have gathered numerical evidence against the Birkhoff-Poritsky conjectur…
For a given rotation number we compute the Hausdorff dimension of the set of well approximable numbers. We use this result and an inhomogeneous version of Jarnik's theorem to show strong recurrence properties of the billiard flow in certain polygons
We analyse the process of energy exchanges generated by the elastic collisions between a point-particle, confined to a two-dimensional cell with convex boundaries, and a `piston', i.e. a line-segment, which moves back and forth along a one-dimensional interval partially intersecting the cell. This model can be considered as the elementary building block of a spatially extended high-dimensional billiard modeling heat transport in a class of hybrid materials exhibiting the kinetics of gases and spatial structure of solids. Using heuristic arguments and numerical analysis, we argue that, in a reg…
We show that for a fixed curve $K$ and for a family of variables curves $L$, the number of $n$-Poncelet pairs is $\frac{e (n)}{2}$, where $e(n)$ is the number of natural numbers $m$ smaller than $n$ and which satisfies mcd $ (m,n)=1$. The curvee $K$ do not have to be part of the family. In order to show this result we consider an associated billiard transformation and a twist map which preserves area. We use Aubry-Mather theory and the rotation number of invariant curves to obtain our main result. In the last section we estimate the derivative of the rotation number of a general twist map usin…
Symmetry Reduction and Rotation Numbers for Poncelet maps
本文研究Poncelet映射的对称性约化，证明其与椭圆台球映射共轭并继承连续对称性，利用Jacobi椭圆函数给出旋转数显式表达，揭示其单调性，并为Poncelet porism提供显式参数条件。
Locally Maximizing orbits for multi-dimensional Twist maps and Birkhoff billiards
本文研究多维辛扭转映射（特别是Birkhoff台球映射）的局部极大化轨道，提出几何准则并证明该映射的两个生成函数具有相同的局部极大化轨道类。
Kustaanheimo-Stiefel Transformation, Birkhoff-Waldvogel Transformation and Integrable Mechanical Billiards
本文研究Kustaanheimo-Stiefel变换与Birkhoff-Waldvogel变换在三维开普勒台球中的应用，揭示可积反射壁的旋转不变性，并建立Levi-Civita平面理论证明双中心台球的可积性。
We construct semi-infinite billiard domains which reverse the direction of most incoming particles. We prove that almost all particles will leave the open billiard domain after a finite number of reflections. Moreover, with high probability the exit velocity is exactly opposite to the entrance velocity, and the particle's exit point is arbitrarily close to its initial position. The method is based on asymptotic analysis of statistics of entrance times to a small interval for irrational circle rotations. The rescaled entrance times have a limiting distribution in a limit when the number of iter…
In this paper we prove the Birkhoff-Poritsky conjecture for centrally-symmetric $C^2$-smooth convex planar billiards. We assume that the domain $\mathcal A$ between the invariant curve of $4$-periodic orbits and the boundary of the phase cylinder is foliated by $C^0$-invariant curves. Under this assumption we prove that the billiard curve is an ellipse. For the original Birkhoff-Poritsky formulation we show that if a neighborhood of the boundary of billiard domain has a $C^1$-smooth foliation by convex caustics of rotation numbers in the interval (0; 1/4] then the boundary curve is an ellipse.…
A comprehensive study of periodic trajectories of billiards within ellipsoids in $d$-dimensional Euclidean space is presented. The novelty of the approach is based on a relationship established between periodic billiard trajectories and extremal polynomials on the systems of $d$ intervals on the real line. By leveraging deep, but yet not widely known results of the Krein-Levin-Nudelman theory of generalized Chebyshev polynomials, fundamental properties of billiard dynamics are proven for any $d$, viz., that the sequences of winding numbers are monotonic. By employing the potential theory we pr…
扫码添加微信好友，提出您的宝贵建议 👇
💡 备注请填写：网站反馈
发表机构由 AI 从论文文本抽取，如发现错误，欢迎反馈修正建议。