Merging binary black holes formed through chemically homogeneous evolution in short-period stellar binaries

We explore a newly proposed channel to create binary black holes of stellar origin. This scenario applies to massive, tight binaries where mixing induced by rotation and tides transports the products of hydrogen burning throughout the stellar envelopes. This slowly enriches the entire star with helium, preventing the build-up of an internal chemical gradient. The stars remain compact as they evolve nearly chemically homogeneously, eventually forming two black holes, which, we estimate, typically merge 4--11 Gyr after formation. Like other proposed channels, this evolutionary pathway suffers from significant theoretical uncertainties, but could be constrained in the near future by data from advanced ground-based gravitational-wave detectors. We perform Monte Carlo simulations of the expected merger rate over cosmic time to explore the implications and uncertainties. Our default model for this channel yields a local binary black hole merger rate of about $10$ Gpc$^{-3}$ yr$^{-1}$ at redshift $z=0$, peaking at twice this rate at $z=0.5$. This means that this channel is competitive, in terms of expected rates, with the conventional formation scenarios that involve a common-envelope phase during isolated binary evolution or dynamical interaction in a dense cluster. The events from this channel may be distinguished by the preference for nearly equal-mass components and high masses, with typical total masses between 50 and 110 $\textrm{M}_\odot$. Unlike the conventional isolated binary evolution scenario that involves shrinkage of the orbit during a common-envelope phase, short time delays are unlikely for this channel, implying that we do not expect mergers at high redshift.Comment: Minor update to match the version published in MNRAS; 15 pages 10 figure

Azimuth laying system Patent

Inertial gimbal alignment system for spacecraft guidanc

Studies of waveform requirements for intermediate mass-ratio coalescence searches with advanced detectors

The coalescence of a stellar-mass compact object into an intermediate-mass black hole (intermediate mass-ratio coalescence; IMRAC) is an important astrophysical source for ground-based gravitational-wave interferometers in the so-called advanced configuration. However, the ability to carry out effective matched-filter based searches for these systems is limited by the lack of reliable waveforms. Here we consider binaries in which the intermediate-mass black hole has mass in the range 24 - 200 solar masses with a stellar-mass companion having masses in the range 1.4 - 18.5 solar masses. In addition, we constrain the mass ratios, q, of the binaries to be in the range 1/140 < q < 1/10 and we restrict our study to the case of circular binaries with non-spinning components. We investigate the relative contribution to the signal-to-noise ratio (SNR) of the three different phases of the coalescence: inspiral, merger and ringdown. We show that merger and ringdown contribute to a substantial fraction of the total SNR over a large portion of the mass parameter space, although in a limited portion the SNR is dominated by the inspiral phase. We further identify three regions in the IMRAC mass-space in which: (i) inspiral-only searches could be performed with losses in detection rates L in the range 10% < L < 27%, (ii) searches based on inspiral-only templates lead to a loss in detection rates in the range 27% < L < 50%$, and (iii) templates that include merger and ringdown are essential to prevent losses in detection rates greater than 50%. We investigate the effectiveness with which the inspiral-only portion of the IMRAC waveform space is covered by comparing several existing waveform families in this regime. Our results reinforce the importance of extensive numerical relativity simulations of IMRACs and the need for further studies of suitable approximation schemes in this mass range.Comment: 10 pages, 3 figure

Nonclassicality of a photon-subtracted Gaussian field

Published versio

Characteristics and processing of fps-16/ jimsphere raw radar data

Error analysis of fps-16/jimsphere raw radar dat

On Influence of Intensive Stationary Electromagnetic Field on the Behavior of Fermionic Systems

Exact solutions of Schroedinger and Pauli equations for charged particles in an external stationary electromagnetic field of an arbitrary configuration are constructed. Green functions of scalar and spinor particles are calculated in this field. The corresponding equations for complex energy of particles bounded by short range potential are deduced. Boundary condition typical for delta - potential is not used in the treatment. Explicit analytical expressions are given for the shift and width of a quasistationary level for different configurations of the external field. The critical value of electric field in which the idea of quasistationary level becomes meaningless is calculated. It is shown that the common view on the stabilizing role of magnetic field concerns only scalar particles.Comment: 15 pages, no figures, LaTeX2

Selecting digital filters for application to detailed wind profiles

Selecting digital filters for application to detailed wind profiles - table

Capability of the FPS-16 radar/jimsphere system for direct measurement of vertical air motions

Capability and procedure for direct measurement of vertical air currents using FPS-16 radar/ jimsphere syste

Spin Squeezing with Coherent Light via Entanglement Swapping

We analyze theoretically a scheme that produces spin squeezing via the continuous swapping of atom-photon entanglement into atom-atom entanglement, and propose an explicit experimental system where the necessary atom-field coupling can be realized. This scheme is found to be robust against perturbations due to other atom-field coupling channels.Comment: 6 pages, 10 figure

Transverse angular momentum of photons

We develop the quantum theory of transverse angular momentum of light beams. The theory applies to paraxial and quasi-paraxial photon beams in vacuum, and reproduces the known results for classical beams when applied to coherent states of the field. Both the Poynting vector, alias the linear momentum, and the angular momentum quantum operators of a light beam are calculated including contributions from first-order transverse derivatives. This permits a correct description of the energy flow in the beam and the natural emergence of both the spin and the angular momentum of the photons. We show that for collimated beams of light, orbital angular momentum operators do not satisfy the standard commutation rules. Finally, we discuss the application of our theory to some concrete cases.Comment: 10 pages, 2 figure