Gravitational Waves from Coalescing Binary Sources

Coalescing binary systems (eg pulsars, neutron stars and black holes) are the most likely sources of gravitational radiation, yet to be detected on or near Earth, where the local gravitational field is negligible and the Poincar\'e symmetry rules. On the other hand, the general theory of gravitational waves emitted by axially symmetric rotating sources predicts the existence of a non-vanishing news function. The existence of such function implies that, for a distant observer, the asymptotic group of isometries, the BMS group, has a translational symmetry that depends on the orbit periodicity of the source, thus breaking the isotropy o the Poincar\'e translations. These results suggest the application of the asymptotic BMS-covariant wave equation to obtain a proper theoretical basis for the gravitational waves observations.Comment: 4 pages, awarded a honorable mention from the Gravity Research Foundation 201

Axial dependence of optical weak measurements in the critical region

The interference between optical beams of different polarizations plays a fundamental role in reproducing the optical analog of the electron spin weak measurement. The extraordinary point in optical weak measurements is represented by the possibility to estimate with great accuracy the Goos-Haenchen (GH) shift by measuring the distance between the peak of the outgoing beams for two opposite rotation angles of the polarizers located before and after the dielectric block. Starting from the numerical calculation of the GH shift, which clearly shows a frequency crossover for incidence near to the critical angle, we present a detailed study of the interference between s and p polarized waves in the critical region. This allows to determine in which conditions it is possible to avoid axial deformations and reproduce the GH curves. In view of a possible experimental implementation, we give the expected weak measurement curves for Gaussian lasers of different beam waist sizes propagating through borosilicate (BK7) and fused silica dielectric blocks.Comment: 16 pages, 7 figure

Roughness correction to the Casimir force : Beyond the Proximity Force Approximation

We calculate the roughness correction to the Casimir effect in the parallel plates geometry for metallic plates described by the plasma model. The calculation is perturbative in the roughness amplitude with arbitrary values for the plasma wavelength, the plate separation and the roughness correlation length. The correction is found to be always larger than the result obtained in the Proximity Force Approximation.Comment: 7 pages, 3 figures, v2 with minor change

Dynamical Casimir effect with cylindrical waveguides

I consider the quantum electromagnetic field in a coaxial cylindrical waveguide, such that the outer cylindrical surface has a time-dependent radius. The field propagates parallel to the axis, inside the annular region between the two cylindrical surfaces. When the mechanical frequency and the thickness of the annular region are small enough, only Transverse Electromagnetic (TEM) photons may be generated by the dynamical Casimir effect. The photon emission rate is calculated in this regime, and compared with the case of parallel plates in the limit of very short distances between the two cylindrical surfaces. The proximity force approximation holds for the transition matrix elements in this limit, but the emission rate scales quadratically with the mechanical frequency, as opposed to the cubic dependence for parallel plates.Comment: 6 page

Quantum radiation in a plane cavity with moving mirrors

We consider the electromagnetic vacuum field inside a perfect plane cavity with moving mirrors, in the nonrelativistic approximation. We show that low frequency photons are generated in pairs that satisfy simple properties associated to the plane geometry. We calculate the photon generation rates for each polarization as functions of the mechanical frequency by two independent methods: on one hand from the analysis of the boundary conditions for moving mirrors and with the aid of Green functions; and on the other hand by an effective Hamiltonian approach. The angular and frequency spectra are discrete, and emission rates for each allowed angular direction are obtained. We discuss the dependence of the generation rates on the cavity length and show that the effect is enhanced for short cavity lengths. We also compute the dissipative force on the moving mirrors and show that it is related to the total radiated energy as predicted by energy conservation.Comment: 17 pages, 1 figure, published in Physical Review

Police sexual coercion and its association with risky sex work and substance use behaviors among female sex workers in St. Petersburg and Orenburg, Russia.

BackgroundExtensive research documents that female sex workers (FSWs) in Russia are very vulnerable to abuses from police, including police sexual coercion. However, despite qualitative data suggesting abusive policing practices are more likely for FSWs contending with substance abuse issues and risky sex work contexts, there is a paucity of quantitative study evaluating these associations specifically in terms of police sexual coercion. Such research is needed to guide structural interventions to improve health and safety for FSWs in Russia and globally.ObjectiveThe purpose of this study is to assess the prevalence of police sexual coercion among FSWs from two Russian cities, St. Petersburg and Orenburg, and to determine whether riskier sex work behaviors and contexts and substance use behaviors, including both IDU and risky alcohol use, are associated with increased risk for sexual coercion from police.MethodFSWs in St. Petersburg and Orenburg were recruited via time-location and convenience sampling and completed structured surveys on demographics (age, education), sex work risks (e.g., violence during sex work) and substance use. Logistic regression analyses assessed associations of substance use and risky sex work with police sexual coercion, adjusting for demographics.ResultsParticipants (N=896) were aged 15 and older (94% were 20+ years). Most (69%) reported past year binge alcohol use, and 48% reported IDU the day before. Half (56%) reported 4+ clients per day. Rape during sex work ever was reported by 64%. Police sexual coercion in the past 12 months was reported by 38%. In the multivariate model, both current IDU (AOR=2.09, CI=1.45-3.02) and past year binge alcohol use (AOR=1.46, CI=1.03-2.07) were associated with police sexual coercion, as was selling sex on the street (not in venues) (AOR=7.81, CI=4.53-13.48) and rape during sex work (AOR=2.04, CI=1.43-2.92).ConclusionCurrent findings document the substantial role police sexual violence plays in the lives of FSWs in Russia. These findings also highlight heightened vulnerability to such violence among self-managed and substance abusing FSWs in this context. Structural interventions addressing police violence against FSWs may be useful to improve the health and safety of this population