Subtracting compact binary foreground sources to reveal primordial gravitational-wave backgrounds

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**holes**leaving only about 0.013\% (respectively, 0.00075\%) unresolved; in contrast, as many as 25\% (respectively, 7.7\%) of binary neutron star sources remain unresolved. Consequently, the binary

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**hole**population will likely not limit observation of primordial backgrounds but the binary neutron star population will limit the sensitivity of 3G detectors to $\Omega_{\rm GW} \sim 10^{-11}$ at 10 Hz (respectively, $\Omega_{\rm GW} \sim 3\times 10^{-12}$).

7/10 relevant

arXiv

Communication through quantum fields near a **black** **hole**

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**hole**-orbiting null geodesics as well as of the timelike contributions that arise because the strong Huygens principle does not hold on the Schwarzschild background. Expand abstract.

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**hole**-orbiting null geodesics as well as of the timelike contributions that arise because the strong Huygens principle does not hold on the Schwarzschild background. We find, in particular, that the non-direct-null and timelike contributions, which do not possess an analog on Minkowski spacetime, can dominate over the direct null contributions. We cover the cases of both geodesic and accelerated and accelerated emitters. Technically, we apply tools previously designed for the study of wave propagation in curved spacetimes to a relativistic quantum information communication setup, first for generic spacetimes, and then for the case of Schwarzschild spacetime in particular.

7/10 relevant

arXiv

Geodesic motion around a supersymmetric AdS5 **black** **hole**

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**hole**is studied. The equations of motion are derived and solved in terms of the Weierstrass $\wp$, $\sigma$ and $\zeta$ functions. Effective potentials and parametric diagrams are used to analyze and characterize timelike, lightlike and spacelike particle motion and a list of possible orbit types is given. Furthermore, various plots of orbits are presented.

7/10 relevant

arXiv

Greybody factor and sparsity of Hawking radiation from a charged
spherical **black** **hole** with scalar hair

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**hole**with a scalar hair. Expand abstract.

**black**hole, only the information regarding the mass and charge of the

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**hole**is available to an external observer. However, there are numerous counterexamples to the 'no-hair' conjecture. In this work, we consider a particular counter-example to the 'no-hair' conjecture in (3+1) dimensions, namely, a static spherically symmetric charged

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**hole**with a scalar hair. We provide semi-analytic bounds on the greybody factors and study the sparsity of Hawking radiation of mass-less uncharged scalar fields. Our results show that the scalar and electric charges contribute oppositely to the greybody factors and the sparsity of the Hawking radiation cascade.

9/10 relevant

arXiv

Joule-Thomson Expansion of Regular Bardeen AdS **Black** **Hole** Surrounded by
Static Anisotropic Quintessence Field

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**hole**characterized by its mass $M$, the nonlinear parameter $g$, the quintessence field parameter $a$ in anti-de sitter spacetime with a static quintessence matter field. We also show that the relative pressure anisotropy, equation of state and the pressure depends on radial coordinate, reflecting the required anisotropy for Bardeen

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**hole**in the quintessence background. Next, we analyze the Joule-Thompson ($JT$) expansion of the

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**hole**spacetime. Treating the cosmological constant as thermodynamic pressure $P$ and its conjugate quantity as thermodynamic volume $V$ we derive the equation of state connecting Hawking temperature and various

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**hole**parameters. We study the $JT$ expansion in the regular Bardeen AdS

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**holes**in the quintessence background through the analysis of inversion temperature and isenthalpic curves. We derive the $JT$ coefficient $\mu$, and use them to plot the inversion and isenthalpic curves. We discuss the effect of quintessence parameter $a$ and $\omega_q$ on the $JT$ coefficient and inversion temperature, especially with the case of $\omega_q=-1$ and $\omega_q=-\frac{1}{3}$. Our analysis shows that quintessence dark energy affects the inversion point $(T_i,P_i)$ .

10/10 relevant

arXiv

Growth of Supermassive **Black** **Hole** Seeds in ETG Star-Forming Progenitors:
Multiple Merging of Stellar Compact Remnants via Gaseous Dynamical Friction
and Gravitational Wave Emission

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**hole**(BH) seeds in the star-forming progenitors of local early-type galaxies (ETGs) at $z\gtrsim 1$. This envisages the migration and merging of stellar compact remnants (neutron stars and stellar-mass BHs) via gaseous dynamical friction toward the central high-density regions of such galaxies. We show that, under reasonable assumptions and initial conditions, the process can build up central BH masses of order $10^4-10^6\, M_\odot$ within some $10^7$ yr, so effectively providing heavy seeds before standard disk (Eddington-like) accretion takes over to become the dominant process for further BH growth. Remarkably, such a mechanism may provide an explanation, alternative to super-Eddington accretion rates, for the buildup of billion solar masses BHs in quasar hosts at $z\gtrsim 7$, when the age of the Universe $\lesssim 0.8$ Gyr constitutes a demanding constraint; moreover, in more common ETG progenitors at redshift $z\sim 2-6$ it can concur with disk accretion to build such large BH masses even at moderate Eddington ratios $\lesssim 0.3$ within the short star-formation duration $\lesssim$ Gyr of these systems. Finally, we investigate the perspectives to detect the merger events between the migrating stellar remnants and the accumulating central supermassive BH via gravitational wave emission with future ground and space-based detectors such as the Einstein Telescope (ET) and the Laser Interferometer Space Antenna (LISA).

7/10 relevant

arXiv

On Regular **Black** **Holes** at Finite Temperature

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**holes**are determined. Expand abstract.

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**holes**at finite temperature. Using the Teleparalelism Equivalent to General Relativity (TEGR) the gravitational Stefan-Boltzmann law and the gravitational Casimir effect at zero and finite temperature are calculated. In addition, the first law of thermodynamics is considered. Then the gravitational entropy and the temperature of the event horizon of a class of regular

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**holes**are determined.

10/10 relevant

arXiv

Distinguishing Brans-Dicke-Kerr type naked singularities and **black** **holes**
with their thin disk electromagnetic radiation properties

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**holes**and naked singularities also represents a major challenge. One possible way of differentiating naked singularities from

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**holes**is through the comparative study of thin accretion disks properties around these different types of compact objects. In the present paper we continue the comparative investigation of accretion disk properties around axially-symmetric rotating geometries in Brans-Dicke theory in the presence of a massless scalar field. The solution of the field equations contains the Kerr metric as a particular case, and, depending on the numerical values of the model parameter $\gamma$, has also solutions corresponding to non-trivial

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**holes**and naked singularities, respectively. Due to the differences in the exterior geometries between

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**holes**and Brans-Dicke-Kerr naked singularities, the thermodynamic and electromagnetic properties of the disks (energy flux, temperature distribution and equilibrium radiation spectrum) are different for these two classes of compact objects, consequently giving clear observational signatures that could discriminate between

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**holes**and naked singularities.

10/10 relevant

arXiv

Broadband X-ray analysis of 1E 1740.7-2942: constraints on spin,
inclination and a tentative **black** **hole** mass

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**hole**in a high-mass X-ray binary system. Although extensively studied in X-rays, many aspects about the underlying nature of the system are still unknown. For example, X-ray data analyses of 1E 1740.7-2942 up to date have not yet unveiled the signature of a reflection component, whose modelling could be used to estimate parameters such as the spin of the

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**hole**and inclination of the disc. We report here on the determination of these parameters from the analysis of the reflection component present in a public \textit{NuSTAR} observation which hasn't been subject to any previous study. We include \textit{XMM-Newton} and \textit{INTEGRAL} data to build a combined spectrum, enabling a joint analysis of both the disc and comptonisation components. Results point to a relatively high inclination disc $\gtrsim$ 50$^{\circ}$ (3 $\sigma$) and a near-maximum speed rotating

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**hole**. The former is in agreement with a previous radio study and the latter is reported here for the first time. Lastly, we follow the methodology of recent efforts to weight

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**holes**with only X-ray spectra and find results that suggest a

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**hole**mass of about 5 M$_\odot$ for 1E 1740.7-2942.

9/10 relevant

arXiv

On the equipartition theorem and **black** **holes** nongaussian entropies

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**hole**thermodynamics. Expand abstract.

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**hole**thermodynamics. Namely, we have different equipartition expressions for distinct statistics. To this end, four different mathematical expressions for the entropy have been selected to demonstrate our objective. Furthermore, a possible phase transition is observed in the heat capacity behavior of the Tsallis and Cirto entropy model.

9/10 relevant

arXiv