749 research outputs found
Accurate inspiral-merger-ringdown gravitational waveforms for non-spinning black-hole binaries including the effect of subdominant modes
We present an analytical waveform family describing gravitational waves (GWs)
from the inspiral, merger and ringdown of non-spinning black-hole binaries
including the effect of several non-quadrupole modes [( apart from ].
We first construct spin-weighted spherical harmonics modes of hybrid waveforms
by matching numerical-relativity simulations (with mass ratio )
describing the late inspiral, merger and ringdown of the binary with
post-Newtonian/effective-one-body waveforms describing the early inspiral. An
analytical waveform family is constructed in frequency domain by modeling the
Fourier transform of the hybrid waveforms making use of analytical functions
inspired by perturbative calculations. The resulting highly accurate,
ready-to-use waveforms are highly faithful (unfaithfulness ) for observation of GWs from non-spinning black hole binaries and are
extremely inexpensive to generate.Comment: 10 pages, 5 figure
Testing the no-hair nature of binary black holes using the consistency of multipolar gravitational radiation
Gravitational-wave (GW) observations of binary black holes offer the best probes of the relativistic, strong-field regime of gravity. Gravitational radiation in the leading order is quadrupolar. However, nonquadrupole (higher order) modes make appreciable contribution to the radiation from binary black holes with large mass ratios and misaligned spins. The multipolar structure of the radiation is fully determined by the intrinsic parameters (masses and spin angular momenta of the companion black holes) of a binary in quasicircular orbit. Following our previous work [S. Dhanpal, A. Ghosh, A. K. Mehta, P. Ajith, and B. S. Sathyaprakash, Phys. Rev. D 99, 104056 (2019).], we develop multiple ways of testing the consistency of the observed GW signal with the expected multipolar structure of radiation from binary black holes in general relativity. We call this a no-hair test of binary black holes as this is similar to testing the no-hair theorem for isolated black holes through mutual consistency of the quasinormal mode spectrum. We use Bayesian inference on simulated GW signals that are consistent/inconsistent with binary black holes in general relativity to demonstrate the power of the proposed tests. We also make estimate systematic errors arising as a result of neglecting companion spins
Testing the no-hair nature of binary black holes using the consistency of multipolar gravitational radiation
Gravitational-wave (GW) observations of binary black holes offer the best probes of the relativistic, strong-field regime of gravity. Gravitational radiation in the leading order is quadrupolar. However, nonquadrupole (higher order) modes make appreciable contribution to the radiation from binary black holes with large mass ratios and misaligned spins. The multipolar structure of the radiation is fully determined by the intrinsic parameters (masses and spin angular momenta of the companion black holes) of a binary in quasicircular orbit. Following our previous work [S. Dhanpal, A. Ghosh, A. K. Mehta, P. Ajith, and B. S. Sathyaprakash, Phys. Rev. D 99, 104056 (2019).], we develop multiple ways of testing the consistency of the observed GW signal with the expected multipolar structure of radiation from binary black holes in general relativity. We call this a no-hair test of binary black holes as this is similar to testing the no-hair theorem for isolated black holes through mutual consistency of the quasinormal mode spectrum. We use Bayesian inference on simulated GW signals that are consistent/inconsistent with binary black holes in general relativity to demonstrate the power of the proposed tests. We also make estimate systematic errors arising as a result of neglecting companion spins
Testing the no-hair nature of binary black holes using the consistency of multipolar gravitational radiation
Gravitational-wave (GW) observations of binary black holes offer the best probes of the relativistic, strong-field regime of gravity. Gravitational radiation in the leading order is quadrupolar. However, nonquadrupole (higher order) modes make appreciable contribution to the radiation from binary black holes with large mass ratios and misaligned spins. The multipolar structure of the radiation is fully determined by the intrinsic parameters (masses and spin angular momenta of the companion black holes) of a binary in quasicircular orbit. Following our previous work [S. Dhanpal, A. Ghosh, A. K. Mehta, P. Ajith, and B. S. Sathyaprakash, Phys. Rev. D 99, 104056 (2019).], we develop multiple ways of testing the consistency of the observed GW signal with the expected multipolar structure of radiation from binary black holes in general relativity. We call this a no-hair test of binary black holes as this is similar to testing the no-hair theorem for isolated black holes through mutual consistency of the quasinormal mode spectrum. We use Bayesian inference on simulated GW signals that are consistent/inconsistent with binary black holes in general relativity to demonstrate the power of the proposed tests. We also make estimate systematic errors arising as a result of neglecting companion spins
New binary black hole mergers in the LIGO-Virgo O3b data
We report the detection of 5 new candidate binary black hole (BBH) merger
signals in the publicly released data from the second half of the third
observing run (O3b) of advanced LIGO and advanced Virgo. The LIGO-Virgo-KAGRA
(LVK) collaboration reported 35 compact binary coalescences (CBCs) in their
analysis of the O3b data [1], with 30 BBH mergers having coincidence in the
Hanford and Livingston detectors. We confirm 17 of these for a total of 22
detections in our analysis of the Hanford-Livingston coincident O3b data. We
identify candidates using a search pipeline employing aligned-spin
quadrupole-only waveforms. Our pipeline is similar to the one used in our O3a
coincident analysis [2], except for a few improvements in the veto procedure
and the ranking statistic, and we continue to use an astrophysical probability
of one half as our detection threshold, following the approach of the LVK
catalogs. Most of the new candidates reported in this work are placed in the
upper and lower-mass gap of the black hole (BH) mass distribution. One BBH
event also shows a sign of spin-orbit precession with negatively aligned spins.
We also identify a possible neutron star-black hole (NSBH) merger. We expect
these events to help inform the black hole mass and spin distributions inferred
in a full population analysis.Comment: 16 pages, 12 figure
A new approach to template banks of gravitational waves with higher harmonics: reducing matched-filtering cost by over an order of magnitude
Searches for gravitational wave events use models, or templates, for the
signals of interest. The templates used in current searches in the
LIGO-Virgo-Kagra (LVK) data model the dominant quadrupole mode
of the signals, and omit sub-dominant higher-order modes (HM) such as
, , which are predicted by general relativity. Hence,
these searches could lose sensitivity to black hole mergers in interesting
parts of parameter space, such as systems with high-masses and asymmetric mass
ratios. We develop a new strategy to include HM in template banks that exploits
the natural connection between the modes. We use a combination of
post-Newtonian formulae and machine learning tools to model aligned-spin
, waveforms corresponding to a given waveform. Each of
these modes can be individually filtered against the data to yield separate
timeseries of signal-to-noise ratios (SNR), which can be combined in a
relatively inexpensive way to marginalize over extrinsic parameters of the
signals. This leads to a HM search pipeline whose matched-filtering cost is
just that of a quadrupole-only search (in contrast to being
, as in previously proposed HM search methods). Our
method is effectual and is generally applicable for template banks constructed
with either stochastic or geometric placement techniques. Additionally, we
discuss compression of -only geometric-placement template banks using
machine learning algorithms.Comment: 12+2 pages, 7+1 figures. The template bank described here will be
publicly available at
https://github.com/JayWadekar/GW_higher_harmonics_searc
Use of thiopurines in inflammatory bowel disease : an update
Inflammatory bowel disease (IBD), once considered a disease of the Western hemisphere, has emerged as a global disease. As the disease prevalence is on a steady rise, management of IBD has come under the spotlight. 5-Aminosalicylates, corticosteroids, immunosuppressive agents and biologics are the backbone of treatment of IBD. With the advent of biologics and small molecules, the need for surgery and hospitalization has decreased. However, economic viability and acceptability is an important determinant of local prescription patterns. Nearly one-third of the patients in West receive biologics as the first/initial therapy. The scenario is different in developing countries where biologics are used only in a small proportion of patients with IBD. Increased risk of reactivation of tuberculosis and high cost of the therapy are limitations to their use. Thiopurines hence become critical for optimal management of patients with IBD in these regions. However, approximately one-third of patients are intolerant or develop adverse effects with their use. This has led to suboptimal use of thiopurines in clinical practice. This review article discusses the clinical aspects of thiopurine use in patients with IBD with the aim of optimizing their use to full therapeutic potential.Peer reviewe
Physics Potential of the ICAL detector at the India-based Neutrino Observatory (INO)
The upcoming 50 kt magnetized iron calorimeter (ICAL) detector at the
India-based Neutrino Observatory (INO) is designed to study the atmospheric
neutrinos and antineutrinos separately over a wide range of energies and path
lengths. The primary focus of this experiment is to explore the Earth matter
effects by observing the energy and zenith angle dependence of the atmospheric
neutrinos in the multi-GeV range. This study will be crucial to address some of
the outstanding issues in neutrino oscillation physics, including the
fundamental issue of neutrino mass hierarchy. In this document, we present the
physics potential of the detector as obtained from realistic detector
simulations. We describe the simulation framework, the neutrino interactions in
the detector, and the expected response of the detector to particles traversing
it. The ICAL detector can determine the energy and direction of the muons to a
high precision, and in addition, its sensitivity to multi-GeV hadrons increases
its physics reach substantially. Its charge identification capability, and
hence its ability to distinguish neutrinos from antineutrinos, makes it an
efficient detector for determining the neutrino mass hierarchy. In this report,
we outline the analyses carried out for the determination of neutrino mass
hierarchy and precision measurements of atmospheric neutrino mixing parameters
at ICAL, and give the expected physics reach of the detector with 10 years of
runtime. We also explore the potential of ICAL for probing new physics
scenarios like CPT violation and the presence of magnetic monopoles.Comment: 139 pages, Physics White Paper of the ICAL (INO) Collaboration,
Contents identical with the version published in Pramana - J. Physic
Laying the foundation of the effective-one-body waveform models SEOBNRv5: improved accuracy and efficiency for spinning non-precessing binary black holes
We present SEOBNRv5HM, a more accurate and faster inspiral-merger-ringdown
gravitational waveform model for quasi-circular, spinning, nonprecessing binary
black holes within the effective-one-body (EOB) formalism. Compared to its
predecessor, SEOBNRv4HM, the waveform model i) incorporates recent high-order
post- Newtonian results in the inspiral, with improved resummations, ii)
includes the gravitational modes (l, |m|) = (3, 2), (4, 3), in addition to the
(2, 2), (3, 3), (2, 1), (4, 4), (5, 5) modes already implemented in SEOBNRv4HM,
iii) is calibrated to larger mass-ratios and spins using a catalog of 442
numerical-relativity (NR) simulations and 13 additional waveforms from
black-hole perturbation theory, iv) incorporates information from second-order
gravitational self-force (2GSF) in the nonspinning modes and radiation-reaction
force. Computing the unfaithfulness against NR simulations, we find that for
the dominant (2, 2) mode the maximum unfaithfulness in the total mass range
is below for 90% of the cases (38% for
SEOBNRv4HM). When including all modes up to l = 5 we find 98% (49%) of the
cases with unfaithfulness below , while these numbers reduce
to 88% (5%) when using SEOBNRv4HM. Furthermore, the model shows improved
agreement with NR in other dynamical quantities (e.g., the angular momentum
flux and binding energy), providing a powerful check of its physical
robustness. We implemented the waveform model in a high-performance Python
package (pySEOBNR), which leads to evaluation times faster than SEOBNRv4HM by a
factor 10 to 50, depending on the configuration, and provides the flexibility
to easily include spin-precession and eccentric effects, thus making it the
starting point for a new generation of EOBNR waveform models (SEOBNRv5) to be
employed for upcoming observing runs of the LIGO-Virgo-KAGRA detectors
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