Global dynamics and asymmetric fractal dimension in a nontwist circle map R. Simile Baroni, R. Egydio de Carvalho, Carlos E. P. Abreu, R. O. Medrano-T Chaos, 2025 We consider the standard nontwist map with strong dissipation that leads the system to a 1D circular map with a quadratic sinusoidal oscillation and two control parameters. The 2D Lyapunov and isoperiodic diagrams reveal a complex interplay between domains of periodicity embedded in regions dominated by quasiperiodic and chaotic behaviors. Arnold tongues and shrimp-like, among other sets of periodicities, compose this rich dynamical scenario in the parameter space. Cobwebs and bifurcation diagrams help reveal the behavior of attractors, including multistability, period-doubling, pitchfork bifurcations, as well as boundary, merging, and interior crises that influence the structures of periodicity. Furthermore, we bring to light the global organization of shrimp-like structures by carrying out a new concept of orbits, the extreme orbits, and announce that the fractal dimension, believed to be universal in the parameter space for decades, has its symmetry breaking in the vicinity of shrimp-like cascades.
Shearless and periodic attractors in the dissipative Labyrinthic map L. F. B. Souza, R. Egydio de Carvalho, R. L. Viana, I. L. Caldas Chaos, 2024 The Labyrinthic map is a two-dimensional area-preserving map that features a robust transport barrier known as the shearless curve. In this study, we explore a dissipative version of this map, examining how dissipation affects the shearless curve and leads to the emergence of quasi-periodic or chaotic attractors, referred to as shearless attractors. We present a route to chaos of the shearless attractor known as the Curry–Yorke route. To investigate the multi-stability of the system, we employ basin entropy and boundary basin entropy analyses to characterize diverse scenarios. Additionally, we numerically investigate the dynamic periodic structures known as “shrimps” and “Arnold tongues” by varying the parameters of the system.
Lagrangian descriptors: The shearless curve and the shearless attractor R. Simile Baroni, R. Egydio de Carvalho Physical Review E, 2024 Hamiltonian systems with a nonmonotonic frequency profile are called nontwist. One of the key properties of such systems, depending on adjustable parameters, is the presence of a robust transport barrier in the phase space called the shearless curve, which becomes the equally robust shearless attractor when dissipation is introduced. We consider the standard nontwist map with and without dissipation. We derive analytical expressions for the Lagrangian descriptor (LD) for the unperturbed map and show how they are related to the rotation number profile. We show how the LDs can reconstruct finite segments of the invariant manifolds for the perturbed map. In the conservative case, we demonstrate how the LDs distinguish the chaotic seas from regular structures. The LDs also provide a remarkable tool to identify when the shearless curve is destroyed: we present a fractal boundary, in the parameter space, for the existence or not of the shearless torus. In the dissipative case, we show how the LDs can be used to localize point attractors and the shearless attractor and distinguish their basins of attraction.
Lagrangian descriptor and escape time as tools to investigate the dynamics of laser-driven polar molecules M. D. Forlevesi, R. Egydio de Carvalho, Emanuel F. de Lima Physical Review E, 2023 We consider the nonlinear dynamics of a diatomic polar molecule under a linearly polarized laser field. We assume a model in which the molecule dipole is coupled with a time-dependent electric field. This system presents a bound energy region where the atoms are bound, and a free-energy region where the atoms are dissociated. Due to the nonalignment between the dipole axis and the laser direction, and the time dependence of the external field, this system presents two and a half degrees of freedom, namely the vibrational degree, the rotation degree, and the time. To investigate the system dynamics, instead of using the Poincaré surface-of-section technique, we propose the use of the Lagrangian descriptor associated with the escape times. The Lagrangian descriptor is a quantity that reveals complex structures in the phase space, whereas the escape times are the time span in which a trajectory is initially in the bound region before escaping to the unbound region. The combination of these two quantities allows us to distinguish between real stability regions from other complex structures, including stickiness regions, and a different formation, which we call escape islands. With the help of these tools, we find that for high-field amplitudes the inclusion of rotation leads to an increase of the stability regions, which implies a decrease of the dissociation in comparison with the one-dimensional case.
Robust tori-like Lagrangian coherent structures Luis C. de Oliveira, Caroline G.L. Martins, M. Roberto, I.L. Caldas, R. Egydio de Carvalho Physica A Statistical Mechanics and Its Applications, 2012
Tunneling among rotation tori R. Egydio de Carvalho, G.M. Favaro Physica A Statistical Mechanics and Its Applications, 2009
Dissipation as a mechanism of energy gain R. Egydio de Carvalho, C. Vieira Abud, F. Caetano Souza Physical Review E Statistical Nonlinear and Soft Matter Physics, 2008
Fermi acceleration on the annular billiard R. Egydio de Carvalho, F. Caetano Souza, Edson D. Leonel Physical Review E Statistical Nonlinear and Soft Matter Physics, 2006