We call internal-wave billiard the dynamical system of a point particle that moves freely inside a planar domain (the table) and is reflected by its boundary according to this nonstandard rule: the angles that the incident and reflected velocities form with a fixed direction (representing gravity) are the same. These systems are point particle approximations for the motion of internal gravity waves in closed containers, hence the name. For a class of tables similar to rectangular trapezoids, but with the slanted leg replaced by a general curve with downward concavity, we prove that the dynamics has only three asymptotic regimes: (1) there exist a global attractor and a global repellor, which are periodic and might coincide; (2) there exists a beam of periodic trajectories, whose boundary (if any) comprises an attractor and a repellor for all the other trajectories; (3) all trajectories are dense (that is, the system is minimal). Furthermore, in the prominent case where the table is an actual trapezoid, we study the sets in parameter space relative to the three regimes. We prove in particular that the set for (1) has positive measure (giving a rigorous proof of the existence of Arnol’d tongues for internal-wave billiards), whereas the sets for (2) and (3) are non-empty but have measure zero.

Lenci, M., Bonanno, C., Cristadoro, G. (2023). Internal-wave billiards in trapezoids and similar tables. NONLINEARITY, 36(2 (February 2023)), 1029-1052 [10.1088/1361-6544/ac98ef].

Internal-wave billiards in trapezoids and similar tables

Cristadoro, G
2023

Abstract

We call internal-wave billiard the dynamical system of a point particle that moves freely inside a planar domain (the table) and is reflected by its boundary according to this nonstandard rule: the angles that the incident and reflected velocities form with a fixed direction (representing gravity) are the same. These systems are point particle approximations for the motion of internal gravity waves in closed containers, hence the name. For a class of tables similar to rectangular trapezoids, but with the slanted leg replaced by a general curve with downward concavity, we prove that the dynamics has only three asymptotic regimes: (1) there exist a global attractor and a global repellor, which are periodic and might coincide; (2) there exists a beam of periodic trajectories, whose boundary (if any) comprises an attractor and a repellor for all the other trajectories; (3) all trajectories are dense (that is, the system is minimal). Furthermore, in the prominent case where the table is an actual trapezoid, we study the sets in parameter space relative to the three regimes. We prove in particular that the set for (1) has positive measure (giving a rigorous proof of the existence of Arnol’d tongues for internal-wave billiards), whereas the sets for (2) and (3) are non-empty but have measure zero.
Articolo in rivista - Articolo scientifico
37e10; 37e45; 37n10; 76b55; Arnol’d tongues; circle homeomorphisms; internal waves; wave attractors;
English
28-dic-2022
2023
36
2 (February 2023)
1029
1052
1029
none
Lenci, M., Bonanno, C., Cristadoro, G. (2023). Internal-wave billiards in trapezoids and similar tables. NONLINEARITY, 36(2 (February 2023)), 1029-1052 [10.1088/1361-6544/ac98ef].
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/395154
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