72 citations · 386 across the 30 of their papers we have counts for
30 papers
Isochronous bifurcations in a two-parameter twist map
Michele Mugnaine, Bruno B. Leal, Alfredo M. Ozorio de Almeida +2
Isochronous islands in phase space emerge in twist Hamiltonian systems as a response to multiple resonant perturbations. According to the Poincaré-Birkhoff theorem, the number of i…
Phase space geometry of general quantum energy transitions
Alfredo M. Ozorio de Almeida
The mixed density operator for coarsegrained eigenlevels of a static Hamiltonian is represented in phase space by the spectral Wigner function, which has its peak on the correspond…
Semiclassical approximation of the Wigner function for the canonical ensemble
Marcos Gil de Oliveira, Alfredo Miguel Ozorio de Almeida
The Weyl-Wigner representation of quantum mechanics allows one to map the density operator in a function in phase space - the Wigner function - which acts like a probability distri…
Isochronous island bifurcations driven by resonant magnetic perturbations in Tokamaks
B. B. Leal, I. L. Caldas, M. C. de Sousa +2
Recent evidences show that heteroclinic bifurcations in magnetic islands may be caused by the amplitude variation of resonant magnetic perturbations in tokamaks. To investigate the…
Exact Markovian evolution of quantum systems with several degrees of freedom : Phase space representations
Aldo R. Fernandes Neto, Alfredo M. Ozorio de Almeida, Olivier Brodier
The exact solution of the Lindblad equation with a quadratic Hamiltonian and linear coupling operators was derived within the chord representation, that is, for the Fourier transfo…
The quantum canonical ensemble in phase space
Alfredo M. Ozorio de Almeida, Gert-Ludwig Ingold, Olivier Brodier
The density operator for a quantum system in thermal equilibrium with its environment depends on Planck's constant, as well as the temperature. At high temperatures, the Weyl repre…
Distinguishing quantum features in classical propagation
Kelvin Titimbo, Gabriel M. Lando, Alfredo M. Ozorio de Almeida
The strictly classical propagation of an initial Wigner function, referred to as TWA or LSC-IVR, is considered to provide approximate averages, despite not being a true Wigner func…
Representation of superoperators in double phase space
Marcos Saraceno, Alfredo M. Ozorio de Almeida
Operators in quantum mechanics - either observables, density or evolution operators, unitary or not - can be represented by c-numbers in operator bases. The position and momentum b…
Negativity witness for the quantum ergodic conjecture
Alfredo M. Ozorio de Almeida
For an ergodic system, the time average of a classical observable coincides with that obtained via the Liouville probability density, a delta-function on the energy shell. Reinterp…
Metaplectic sheets and caustic traversals in the Weyl representation
Alfredo M. Ozorio de Almeida, Gert-Ludwig Ingold
The quantum Hamiltonian generates in time a family of evolution operators. Continuity of this family holds within any choice of representation and, in particular, for the Weyl prop…
Alternate islands of multiple isochronous chains in wave-particle interactions
M. C. de Sousa, I. L. Caldas, A. M. Ozorio de Almeida +2
We analyze the dynamics of a relativistic particle moving in a uniform magnetic field and perturbed by a standing electrostatic wave. We show that a pulsed wave produces an infinit…
Semiclassical theory for small displacements
Eduardo Zambrano, Alfredo M. Ozorio de Almeida
Characteristic functions contain complete information about all the moments of a classical distribution and the same holds for the Fourier transform of the Wigner function: a quant…
Complex WKB Evolution of Markovian Open Systems
O. Brodier, A. M. Ozorio de Almeida
We derive a semiclassical approximation for the evolution generated by the Lindblad equation as a generalization of complex WKB theory. Linear coupling to the environment is assume…
Uniform approximation for the overlap caustic of a quantum state with its translations
Eduardo Zambrano, Alfredo M Ozorio de Almeida
The semiclassical Wigner function for a Bohr-quantized energy eigenstate is known to have a caustic along the corresponding classical closed phase space curve in the case of a sing…
Semiclassical Evolution of Dissipative Markovian Systems
A. M. Ozorio de Almeida, P. de M. Rios, O. Brodier
A semiclassical approximation for an evolving density operator, driven by a "closed" hamiltonian operator and "open" markovian Lindblad operators, is obtained. The theory is based…
Quantum Baker Maps for Spiraling Chaotic Motion
Pedro R. del Santoro, Raul O. Vallejos, Alfredo M. Ozorio de Almeida
We define a coupling of two baker maps through a pi/2 rotation both in position and in momentum. The classical trajectories thus exhibit spiraling, or loxodromic motion, which is o…
Periodic orbit bifurcations and scattering time delay fluctuations
J. P. Keating, A. M. Ozorio de Almeida, S. D. Prado +2
We study fluctuations of the Wigner time delay for open (scattering) systems which exhibit mixed dynamics in the classical limit. It is shown that in the semiclassical limit the ti…
On resumming periodic orbits in the spectra of integrable systems
Alfredo M. Ozorio de Almeida, Caio H. Lewenkopf, Steven Tomsovic
Spectral determinants have proven to be valuable tools for resumming the periodic orbits in the Gutzwiller trace formula of chaotic systems. We investigate these tools in the conte…
A variational principle for actions on symmetric symplectic spaces
Pedro de M. Rios, A. Ozorio de Almeida
We present a definition of generating functions of canonical relations, which are real functions on symmetric symplectic spaces, discussing some conditions for the presence of caus…
On the propagation of semiclassical Wigner functions
Pedro P. de M. Rios, A. M. Ozorio de Almeida
We establish the difference between the propagation of semiclassical Wigner functions and classical Liouville propagation. First we re-discuss the semiclassical limit for the propa…
Hyperbolic Scar Patterns in Phase Space
Alejandro M. F. Rivas, Alfredo M. Ozorio de Almeida
We develop a semiclassical approximation for the spectral Wigner and Husimi functions in the neighbourhood of a classically unstable periodic orbit of chaotic two dimensional maps.…
Scars of the Wigner function
Fabricio Toscano, Marcus A. M. de Aguiar, Alfredo M. Ozorio de Almeida
We propose a picture of Wigner function scars as a sequence of concentric rings along a two-dimensional surface inside a periodic orbit. This is verified for a two-dimensional plan…
Decomposition of Resonant Scatterers by Surfaces of Section
Raul O. Vallejos, Alfredo M. Ozorio de Almeida
Scattering on the energy shell is viewed here as the relation between the bound states of the Hamiltonian, restricted to sections on leads that are asymptotically independent, far…
Poincare's Recurrence Theorem and the Unitarity of the S matrix
Alfredo M. Ozorio de Almeida, Raul O. Vallejos
A scattering process can be described by suitably closing the system and considering the first return map from the entrance onto itself. This scattering map may be singular and dis…