arXiv subjects

P. Longo

Publications and source records attributed to P. Longo.

3 recordsLinked to original sources

arXiv2015

Probing few-excitation eigenstates of interacting atoms on a lattice by observing their collective light emission in the far field

The collective emission from a one-dimensional chain of interacting two-level atoms coupled to a common electromagnetic reservoir is investigated. We derive the system's dissipative few-excitation eigenstates, and analyze their static properties, including the collective dipole moments and branching ratios between different eigenstates. Next, we study the dynamics, and characterize the light emitted or scattered by such a system via different far-field observables. Throughout the analysis, we consider spontaneous emission from an excited state as well as two different pump field setups, and contrast the two extreme cases of non-interacting and strongly interacting atoms. For the latter case, the two-excitation submanifold contains a two-body bound state, and we find that the two cases lead to different dynamics and far-field signatures. Finally we exploit these signatures to characterize the wavefunctions of the collective eigenstates. For this, we identify a direct relation between the collective branching ratio and the momentum distribution of the collective eigenstates' wavefunction. This provides a method to proof the existence of certain collective eigenstates and to access their wave function without the need to individually address and/or manipulate single atoms.

quant-ph↗

arXiv2006

Emission of gravitational waves from binary systems in the galactic center and diffraction by star clusters

Binary systems of compact objects are strong emitters of gravitational waves whose amplitude depends on the binary orbital parameters as the component mass, the orbital semi-major axis and eccentricity. Here, in addition to the famous Hulse-Taylor binary system, we have studied the possibility to detect the gravitational wave signal emitted by binary systems at the center of our galaxy. In particular, recent infrared observation of the galactic center have revealed the existence of a cluster of stars each of which appears to orbit the central black hole in $SgrA^*$. For the stars labelled as S2 and S14, we have studied the emitted spectrum of gravitational wave and compare it with the sensitivity threshold of space-based interferometers like Lisa and Astrod. Furthermore, following recent observations, we have considered the possibility that $SgrA^*$ is actually a binary system of massive black holes and calculated the emission spectrum as a function of the system parameters. The diffraction pattern of gravitational waves emitted by a binary system by a cluster of stars has been also analyzed. We remark that this is only a preliminary-theoretical work than can acquire more interest in view of the next-coming gravitational wave astronomy era.

astro-ph↗

arXiv2006

Gravitational wave scintillation by a stellar cluster

The diffraction effects on gravitational waves propagating through a stellar cluster are analyzed in the relevant approximation of Fresnel diffraction limit. We find that a gravitational wave scintillation effect - similar to the radio source scintillation effect - comes out naturally, implying that the gravitational wave intensity changes in a characteristic way as the observer moves.

astro-ph↗