74 research outputs found
Observational limits on the rate of radiation-driven binary black hole capture events
No full text© 2022 American Physical Society. Dense astrophysical environments like globular clusters and galactic nuclei can host hyperbolic encounters of black holes which can lead to gravitational-wave driven capture. There are several astrophysical models which predict a fraction of binary black hole mergers to come from these radiation-driven capture scenarios. In this paper, we present the sensitivity of a search toward gravitational-wave driven capture events for O3, the third observing run of LIGO and Virgo. We use capture waveforms produced by numerical relativity simulations covering four different mass ratios and at least two different values of initial angular momentum per mass ratio. We employed the most generic search for short-duration transients in O3 to evaluate the search sensitivity in this parameter space for a wide range in total mass in terms of visible spacetime volume. From the visible spacetime volume we determine for the first time the merger rate upper limit of such systems. The most stringent estimate of rate upper limits at 90% confidence is 0.2 Gpc-3 yr-1 for an equal mass 200 M⊙ binary. Furthermore, in recent studies the event GW190521 has been suggested to be a capture event. With this interpretation of GW190521, we find the merger rate of similar events to be 0.47 Gpc-3 yr-1.11Nsciescopu
Cohomological X-independence for Higgs bundles and Gopakumar–Vafa invariants
No full textThe aim of this paper is two-fold. Firstly, we prove Toda’s X-independence conjecture for Gopakumar–Vafa invariants of arbitrary local curves. Secondly, following Davison’s work, we introduce the BPS cohomology for moduli spaces of Higgs bundles of rank r and Euler characteristic X which are not necessary coprime, and show that it does not depend on X. This result extends the Hausel–Thaddeus conjecture on the X-independence of E-polynomials proved by Mellit, Groechenig–Wyss–Ziegler and Yu in two ways: We obtain an isomorphism of mixed Hodge modules on the Hitchin base rather than an equality of E-polynomials, and we do not need the coprime assumption. The proof of these results is based on a description of the moduli stack of one-dimensional coherent sheaves on a local curve as a global critical locus which is obtained in the companion paper by the first author and Naruki Masuda
Gravitational wave phasing for spinning compact binaries in inspiraling eccentric orbits
No full text
Learning approach among health sciences students in a medical college in Nepal: a cross-sectional study
No full textAji Gopakumar,1 Susirith Mendis,2 Jayakumary Muttappallymyalil,3 Jayadevan Sreedharan3 1Department of General Education, 2Continuing Medical Education, Continuing Professional Development and Center for Continuing Education and Community Outreach, 3Department of Community Medicine, Gulf Medical University, Ajman, United Arab Emirates Shah et al aimed to explore the learning approaches among medical, dental, and nursing students which were considered useful to transform the students to become better learners. While the generic objective of the study is appreciated, we have some concerns regarding the methodology and statistical analysis of the study. View the original paper by Author and colleagues. 
Instantaneous third post-Newtonian accurate expressions for the radiated energy and angular momentum during hyperbolic encounters of non-spinning compact objects
No full textWe compute the third post-Newtonian (3PN) accurate instantaneous contributions to the radiated gravitational wave (GW) energy and angular momentum arising from the hyperbolic passages of non-spinning compact objects. The present computations employ 3PN-accurate instantaneous contributions to the far-zone energy and angular momentum fluxes and the 3PN-accurate Keplerian type parametric solution for compact binaries in hyperbolic orbits
Third order post-Newtonian gravitational radiation from two-body scattering: Instantaneous energy and angular momentum radiation
No full textWe compute the third post-Newtonian (3PN) accurate instantaneous contributions to the radiated gravitational wave energy and angular momentum arising from the hyperbolic passages of nonspinning compact objects. The present computations employ 3PN-accurate instantaneous contributions to the far-zone energy and angular momentum fluxes and the 3PN-accurate Keplerian type parametric solution for compact binaries in hyperbolic orbits
Solving post-Newtonian accurate Kepler equation
No full textInternational audienceWe provide an elegant way of solving analytically the third post-Newtonian (3PN) accurate Kepler equation, associated with the 3PN-accurate generalized quasi-Keplerian parametrization for compact binaries in eccentric orbits. An additional analytic solution is presented to check the correctness of our compact solution and we perform comparisons between our PN-accurate analytic solution and a very accurate numerical solution of the PN-accurate Kepler equation. We adapt our approach to compute crucial 3PN-accurate inputs that will be required to compute analytically both the time and frequency domain ready-to-use amplitude-corrected PN-accurate search templates for compact binaries in inspiralling eccentric orbits
Memory Effect from Spinning Unbound Binaries
No full textWe present a recently developed prescription to obtain ready-to-use gravitational wave (GW) polarization states for spinning compact binaries on hyperbolic orbits. We include leading order spin-orbit interactions, invoking 1.5PN-accurate quasi-Keplerian parametrization for the radial part of the orbital dynamics. We also include radiation reaction effects on h + and h × during the interaction. In the GW signals from spinning binaries there is evidence of the memory effect in both polarizations, in contrast to the non-spinning case, where only the cross polarizations exhibits non-vanishing amplitudes at infinite time. We also compute 1PN-accurate GW polarization states for non-spinning compact binaries in unbound orbits in a fully parametric way, and compare them with existing waveforms
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