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A. Guerreiro

Publications and source records attributed to A. Guerreiro.

8 recordsLinked to original sources

Pressureless stationary solutions in a Newton-Yukawa gravity model

Non-minimally coupled curvature-matter gravity models are an interesting alternative to the Theory of General Relativity and to address the dark energy and dark matter cosmological problems. These models have complex field equations that prevent a full analytical study. Nonetheless, in a particular limit, the behavior of a matter distribution can, in these models, be described by a Schrödinger-Newton system. In nonlinear optics, the Schrödinger-Newton system can be used to tackle a wide variety of relevant situations and several numerical tools have been developed for this purpose. Interestingly, these methods can be adapted to study General Relativity problems as well as its extensions. In this work, we report the use of these numerical tools to study a particular non-minimal coupling model that introduces two new potentials, an attractive Yukawa potential and a repulsive potential proportional to the energy density. Using the imaginary-time propagation method we have shown that stationary solutions arise even at low energy density regimes.

gr-qc

Hight temperature generation of entangled light in parametrically excited micro and nano-ring ressonators for integrated optics

We propose a physical scheme to generate entangled light at high temperatures through the excitation of vacuum fluctuations of the electromagnetic field using periodic modulations of a refractive index of a ring resonator. We consider the processes of dissipation and decoherence resulting from the coupling of the system with an environment at finite temperature and show that the total amount of entanglement generated does not depend on the temperature, which only affects the time necessary for the system to produce such an amount of entanglement.

quant-ph

Using numerical methods from nonlocal optics to simulate the dynamics of N-body systems in alternative theories of gravity

The generalized Schrödinger-Newton system of equations with both local and nonlocal nonlinearities is widely used to describe light propagating in nonlinear media under the paraxial approximation. However, its use is not limited to optical systems and can be found to describe a plethora of different physical phenomena, for example, dark matter or alternative theories for gravity. Thus, the numerical solvers developed for studying light propagating under this model can be adapted to address these other phenomena. Indeed, in this work we report the development of a solver for the HiLight simulations platform based on GPGPU supercomputing and the required adaptations for this solver to be used to test the impact of new extensions of the Theory of General Relativity in the dynamics of the systems, in particular those based on theories with non-minimal coupling between curvature and matter. This approach in the study of these new models offers a quick way to validate them since their analytical analysis is difficult. The simulation module, its performance, and some preliminary tests are presented in this paper.

gr-qc

Slow-light dissipative solitons in an atomic medium assisted by an incoherent pumping field

This work models the propagation of an optical pulse in a 4-level atomic system in the electromagnetic induced transparency regime. By demonstrating that linear and nonlinear optical properties can be externally controlled and tailored by a continuous-wave control laser beam and an assisting incoherent pump field, it is shown how these media can provide an excellent framework to experimentally explore pulse dynamics in the presence of non-conservative terms, either gain or loss. Furthermore, we explore the existence of stable dissipative soliton solutions, testing the analytical results with computational simulations of both the effective (1+1)-dimensional model and the full Maxwell-Bloch system of equations.

physics.optics

Production of bright entangled photons from moving optical boundaries

We discuss a mechanism of generating two separable beams of light with high degree of entanglement in momentum using a fast and sharp optical boundary. Three regimes of light generation are identified depending on the number of resonant interactions between the optical perturbation and the electromagnetic field. The intensity of the process is discussed in terms of the relevant physical parameters: variation of refractive index and apparent velocity of the optical boundary. Our results suggest a different class of generation entangled light robust against thermal degradation by exciting zero point fluctuations using parametric resonant optical modulations.

quant-ph

Optomechanical entanglement between a movable mirror and a cavity field

We show how stationary entanglement between an optical cavity field mode and a macroscopic vibrating mirror can be generated by means of radiation pressure. We also show how the generated optomechanical entanglement can be quantified and we suggest an experimental readout-scheme to fully characterize the entangled state. Surprisingly, such optomechanical entanglement is shown to persist for environment temperatures above 20K using state-of-the-art experimental parameters.

quant-ph

Macroscopic thermal entanglement due to radiation pressure

Can entanglement and the quantum behavior in physical systems survive at arbitrary high temperatures? In this Letter we show that this is the case for a electromagnetic field mode in an optical cavity with a movable mirror in a thermal state. We also identify two different dynamical regimes of generation of entanglement separated by a critical coupling strength.

quant-ph

Dipolar radiation from spinning dust grains coupled to an electromagnetic wave

In this letter we investigate how the complex rotation and quivering motion of an elongated polarized dust grain in the presence of a monochromatic electromagnetic wave can originate dipolar emission with two distinct spectral components. We present a model for the emission of radiation by elongated polarized dust grains under the influence of both an external electromagnetic wave and a constant background magnetic field. The dust, exhibiting rotational motion at the external electromagnetic field frequency w0 as well as quivering motion at frequency W0, proportional to the em field amplitude, will radiate with frequencies that will depend on the external field wavelength and amplitude. The radiated spectra exibits a frequency around w0, and sidebands at w0+-W0 and w0+-2W0. Since the amplitude and the frequency of the background electromagnetic field are independent parameters, this model establishes a correlation between different spectral components of galactic dipolar emission, which may help to explain the correlation between a component of the Galactic microwave emission and the 100micons thermal emission from interstellar dust, that has been recently measured.

physics.plasm-ph