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Anuradha Gupta

Publications and source records attributed to Anuradha Gupta.

At least 55 records · Page 3Linked to original sources

Product isometry of generalized weighted composition operator on general weighted Hardy space

We obtain necessary and sufficient conditions for the composition and weighted composition operator and product of composition operators to be isometry and unitary on $H_{E}(ξ).$ With the help of counter example we also prove that the product of two non isometric composition operator and weighted composition operator can be isometry on $H_{E}(ξ)$. We also completely characterize the boundedness of generalized weighted composition operators on $H_{E}(ξ).$

math.FA↗

A Horizon Study for Cosmic Explorer: Science, Observatories, and Community

This Horizon Study describes a next-generation ground-based gravitational-wave observatory: Cosmic Explorer. With ten times the sensitivity of Advanced LIGO, Cosmic Explorer will push gravitational-wave astronomy towards the edge of the observable universe ($z \sim 100$). The goals of this Horizon Study are to describe and evaluate design concepts for Cosmic Explorer; to plan for the United States' leadership in gravitational-wave astronomy; and to envisage the role of Cosmic Explorer in the international effort to build a "Third-Generation" (3G) observatory network that will make discoveries transformative across astronomy, physics, and cosmology.

astro-ph.IM↗

Remnant Black Hole Kicks and Implications for Hierarchical Mergers

When binary black holes merge in dense star clusters, their remnants can pair up with other black holes in the cluster, forming heavier and heavier black holes in a process called hierarchical merger. The most important condition for hierarchical merger to occur is that remnants formed by mergers are retained by the host star cluster. Using the publicly available gravitational-wave event database, we infer the magnitudes of kick velocities imparted to the remnant black holes due to anisotropic emission of gravitational waves and use that to quantify the retention probability of each event as a function of the escape speed of the star cluster. Among the second gravitational-wave transient catalog (GWTC-2) events, GW190814 provides the tightest constraint on the kick magnitude with ${\rm V_{kick}}=74_{-7}^{+10}$ km/s at the 90% credible level. We find that star clusters with escape speeds of 200 km/s can retain about 50% of the events in the GWTC-2. Using the escape speed distributions of nuclear star clusters and globular clusters, we find that $\sim 17$ (2) remnants of GWTC-2 may be retained by the host star cluster if all GWTC-2 events occurred in nuclear (globular) clusters. Our study demonstrates the importance of folding in kick velocity inferences in future studies of hierarchical mergers.

astro-ph.HE↗

Isometries of the product of composition operators on weighted Bergman space

In this paper the necessary and sufficient conditions for the product of composition operators to be isometry are obtained on weighted Bergman space. With the help of a counter example we also proved that unlike on $\mathcal{H}^2(\mathbb{D})$ and $\mathcal{A}_α^2(\mathbb{D}),$ the composition operator on $\mathcal{S}^2(\mathbb{D})$ induced by an analytic self map on $\mathbb{D}$ with fixed origin need not be of norm one. We have generalized the Schwartz's well known result on $\mathcal{A}_α^2(\mathbb{D})$ which characterizes the almost multiplicative operator on $\mathcal{H}^2(\mathbb{D}).$

math.FA↗

Tests of general relativity using multiband observations of intermediate mass binary black hole mergers

Observation of gravitational waves (GWs) in two different frequency bands is referred to as multiband GW astronomy. With the planned Laser Interferometric Space Antenna (LISA) operating in the $10^{-4}-0.1$ Hz range, and third generation (3G) ground-based detectors such as the Cosmic Explorer (CE) and Einstein Telescope (ET), operating in the $1$-$10^4$ Hz range, multiband GW astronomy could be a reality in about a decade. In this paper we present the potential of multiband observations of intermediate mass binary black holes (IMBBHs) of component masses ${\sim}10^2$-$10^3\,M_{\odot}$ to test general relativity (GR). We show that mutiband observations of IMBBHs would permit multiparameter tests of GR-tests where more than one post-Newtonian (PN) coefficient is simultaneously measured yielding more rigorous constraints on possible modifications to GR. We also find that the improvement due to multibanding can often be much larger than the best of the bounds from either of the two observatories. The origin of this result, as we shall demonstrate, can be traced to the lifting of degeneracies among the various parameters when the information from LISA and 3G are taken together. We obtain the best multiband bounds for an IMBBH with a total redshifted mass of $200\,M_{\odot}$ and a mass ratio of 2. For single-parameter tests, this system at 1 Gpc would allow us to constrain the deviations on all the PN coefficients to below $10\%$ and derive simultaneous bounds on the first seven PN coefficients to below $50\%$ (with low spins).

gr-qc↗

Dark Sirens to Resolve the Hubble-Lemaître Tension

The planned sensitivity upgrades to the LIGO and Virgo facilities could uniquely identify host galaxies of dark sirens-compact binary coalescences without any electromagnetic counterparts-within a redshift of z = 0.1. This is aided by the higher order spherical harmonic modes present in the gravitational-wave signal, which also improve distance estimation. In conjunction, sensitivity upgrades and higher modes will facilitate an accurate, independent measurement of the host galaxy's redshift in addition to the luminosity distance from the gravitational wave observation to infer the Hubble-Lemaître constant H0 to better than a few percent in five years. A possible Voyager upgrade or third generation facilities would further solidify the role of dark sirens for precision cosmology in the future.

astro-ph.CO↗

Multiparameter tests of general relativity using multiband gravitational-wave observations

In this Letter we show that multiband observations of stellar-mass binary black holes by the next generation of ground-based observatories (3G) and the space-based Laser Interferometer Space Antenna (LISA) would facilitate a comprehensive test of general relativity by simultaneously measuring all the post-Newtonian (PN) coefficients. Multiband observations would measure most of the known PN phasing coefficients to an accuracy below a few percent---two orders-of-magnitude better than the best bounds achievable from even `golden' binaries in the 3G or LISA bands. Such multiparameter bounds would play a pivotal role in constraining the parameter space of modified theories of gravity beyond general relativity.

gr-qc↗

Small Spins of Primordial Black Holes from Random Geometries: Bekenstein-Hawking Entropy and Gravitational Wave Observations

Black hole entropy is a robust prediction of quantum gravity with no established phenomenological consequences to date. We use the Bekenstein-Hawking entropy formula and general-relativistic statistical mechanics to determine the probability distribution of random geometries uniformly sampled in phase space. We show that this statistics (in the limit $\hbar\to 0$) is relevant to large curvature perturbations, resulting in a population of primordial black holes with zero natal spin. In principle, the identification of such a population at LIGO, Virgo, and future gravitational wave observatories could provide the first observational evidence for the statistical nature of black hole entropy.

gr-qc↗

Generalized Drazin-Meromorphic Invertible Operators and Browder's Type Theorems

In this paper we give necessary and sufficient conditions for a bounded linear operator $T$ to be generalized Drazin-Riesz invertible or generalized Drazin-meromorphic invertible. Also, we study generalized Browder's theorem and generalized a-Browder's theorem by means of set of interior points of various parts of spectrum of $T$.

math.FA↗

Black holes in the low mass gap: Implications for gravitational wave observations

Binary neutron-star mergers will predominantly produce black-hole remnants of mass $\sim 3-4\,M_{\odot}$, thus populating the putative \emph{low mass gap} between neutron stars and stellar-mass black holes. If these low-mass black holes are in dense astrophysical environments, mass segregation could lead to "second-generation" compact binaries merging within a Hubble time. In this paper, we investigate possible signatures of such low-mass compact binary mergers in gravitational-wave observations. We show that this unique population of objects, if present, will be uncovered by the third-generation gravitational-wave detectors, such as Cosmic Explorer and Einstein Telescope. Future joint measurements of chirp mass ${\cal M}$ and effective spin $χ_{\rm eff}$ could clarify the formation scenario of compact objects in the low mass gap. As a case study, we show that the recent detection of GW190425 (along with GW170817) favors a double Gaussian mass model for neutron stars, under the assumption that the primary in GW190425 is a black hole formed from a previous binary neutron star merger.

gr-qc↗

Inexact infinite products of weak quasi-contraction mappings in $b$-metric spaces

The influence of errors on the convergence of infinite products of weak quasi-contraction mappings in $b$-metric spaces is explored. An example demonstrating the necessity of convergence of the sequence of computational errors to zero is also provided. Moreover, we discuss weak ergodic theorems in the setting of $b$-metric spaces.

math.FA↗

Effect of orbital eccentricity on the dynamics of precessing compact binaries

We study precession dynamics of generic binary black holes in eccentric orbits using an effective potential based formalism derived in [M. Kesden et al., PRL {\bf 114}, 081103 (2015)]. This effective potential is used to classify binary black holes into three mutually exclusive spin morphologies. During the inspiral phase, binaries make transitions from one morphology to others. We evolve a population of binary black holes from an initial separation of $1000\mathbf{M}$ to a final separation of $10\mathbf{M}$ using post-Newtonian accurate evolution equations. We find that, given suitable initial conditions, a binary's eccentricity can follow one of three distinct evolutionary patterns: (i) eccentricity monotonically increasing until final separation, (ii) eccentricity rising after decaying to a minimum value, and (iii) eccentricity monotonically decreasing throughout the inspiral. The monotonic growth or growth after reaching a certain minimum of eccentricity is due to the effect of 2PN spin-spin coupling. Further, we investigate the morphology transitions in eccentric binaries and find that the probability of such binaries transiting from one to other is similar to those in circular orbits, implying that eccentricity plays a sub-dominant role in spin morphology evolution of a precessing binary black hole. We, hence, argue that the morphological classification of spin precession dynamics is a robust tool to constrain the formation channels of binaries with arbitrary eccentricity as well.

gr-qc↗

Calibrating the cosmic distance ladder using gravitational-wave observations

Type Ia supernovae (SNe Ia) are among preeminent distance ladders for precision cosmology due to their intrinsic brightness, which allows them to be observable at high redshifts. Their usefulness as unbiased estimators of absolute cosmological distances however depends on accurate understanding of their intrinsic brightness, or anchoring their distance scale. This knowledge is based on calibrating their distances with Cepheids. Gravitational waves from compact binary coalescences, being standard sirens, can be used to validate distances to SNe Ia, when both occur in the same galaxy or galaxy cluster. The current measurement of distances by the advanced LIGO and Virgo detector network suffers from large statistical errors ($\sim 50\%$). However, we find that using a third generation gravitational-wave detector network, standard sirens will allow us to measure distances with an accuracy of $\sim 0.1\%$-$3\%$ for sources within $\le300$ Mpc. These are much smaller than the dominant systematic error of $\sim 5\%$ due to radial peculiar velocity of host galaxies. Therefore, gravitational-wave observations could soon add a new cosmic distance ladder for an independent calibration of distances to SNe Ia.

astro-ph.CO↗

On coupled best proximity points and Ulam-Hyers stability

For two nonempty, closed, bounded and convex subsets $A$ and $B$ of a uniformly convex Banach space $X$ consider a mapping $T:(A \times B) \cup (B \times A) \rightarrow A \cup B$ satisfying $T(A,B) \subset B$ and $T(B, A) \subset A$. In this paper the existence of a coupled best proximity point is established when $T$ is considered to be a p-cyclic contraction mapping and a p-cyclic nonexpansive mapping. The Ulam-Hyers stability of the best proximity point problem is also studied.

math.FA↗

Quasi-Fredholm spectrum and compact perturbations

In this paper we explore some characteristics of the quasi-Fredholm resolvent set $ρ_{qf}(T)$ of an operator $T$ defined on an infinite dimensional Banach space $X$. Moreover, in the case of Hilbert space $H$, we study the stability of the SVEP and describe the operators for which the SVEP is preserved under compact perturbations using quasi-Fredholm spectrum and $ρ_{qf}(T)$.

math.SP↗