Hasil untuk "gr-qc"

Steffen Biermann, Sebastian Erne, Cisco Gooding et al.

Faizuddin Ahmed

A hypothetical energy quantization condition is imposed in [1] (Francisco A. Cruz Neto {\it et al.}, arXiv : 1910.11701 [gr-qc]) in order to show consistent of the result with those in [2] but fail or unable to show consistency with those in [3].

Ivo Terek

A. Zanwar, A. Aggarwal

Burmester GR, Kremer JM, Bosch FV den, Kivitz A, Bessette L, Li Y, Zhou Y, Othman AA, Pangan AL, Camp HS. (Charité– Universitätsmedizin, Berlin, Germany; Albany Medical College, Albany, NY, USA; VIB-UGent Center for Inflammation Research, Department of Internal Medicine, Ghent University, and Department of Rheumatology, Ghent University Hospital, Ghent, Belgium; Altoona Center for Clinical Research, Duncansville, PA, USA; Laval University, Quebec, QC, Canada; and AbbVie Inc, North Chicago, IL, USA.) Safety and efficacy of upadacitinib in patients with rheumatoid arthritis and inadequate response to conventional synthetic disease-modifying antirheumatic drugs (SELECT-NEXT): A randomised, double-blind, placebocontrolled phase 3 trial. Lancet 2018;391:2503–12

V. Paromov

A. Svidzinsky, R. Hilborn

In a recent paper "Tests of general relativity with GW170817" (arXiv:1811.00364 [gr-qc]) the authors claimed overwhelming evidence in favor of tensor gravitational wave (GW) polarization over vector by analyzing GW signals measured by the LIGO-Virgo network. Here we show that the measured LIGO-Livingston signal is substantially reduced at certain frequency intervals which can be attributed to noise filtering. We found that if these regions are excluded from the analysis then data are consistent with vector GW polarization and not with tensor. We show that if the signal accumulation method is applied over the entire detector bandwidth, including the regions in which the signal is depleted by noise subtraction, the result underestimates the LIGO-Livingston signal amplitude. That smaller amplitude then leads to an erroneous conclusion that favors tensor polarization over vector polarization for the GW.

M. Bojowald

A. Övgün

N. Koutsias, G. Pezzatti, A. Madoui et al.

B. Hardy

R. Edwards

RezekiAyu Citra Utama

C. Macchi

E. Livine, Daniel R. Terno

Abstract In the framework of loop quantum gravity (LQG), we generalize previous boundary state counting for black hole entropy [E.R. Livine, D.R. Terno, Quantum black holes: Entropy and entanglement on the horizon, Nucl. Phys. B 741 (2006) 131, gr-qc/0508085 ] to a full bulk state counting. After suitable gauge fixing, we show how to compute the bulk entropy of a bounded region of space (the “black hole”) with fixed boundary conditions. This allows to study in detail the relationship between the entropy and the boundary area and to identify a holographic regime for LQG where the leading order of the entropy scales with the area. In this regime we can fine tune the factor between entropy and area without changing the Immirzi parameter.

P. Boonserm, M. Visser

In two previous articles [Phys. Rev. D71 (2005) 124307 (gr-qc/0503007) and Phys. Rev. D76 (2006) 0440241 (gr-qc/0607001)] we have discussed several "algorithmic" techniques that permit one (in a purely mechanical way) to generate large classes of general-relativistic static perfect fluid spheres. Working in Schwarzschild curvature coordinates, we used these algorithmic ideas to prove several "solution-generating theorems" of varying levels of complexity. In the present article we consider the situation in other coordinate systems. In particular, in general diagonal coordinates we shall generalize our previous theorems, in isotropic coordinates we shall encounter a variant of the so-called "Buchdahl transformation," and in other coordinate systems (such as Gaussian polar coordinates, Synge isothermal coordinates, and Buchdahl coordinates) we shall find a number of more complex "Buchdahl-like transformations" and "solution-generating theorems" that may be used to investigate and classify the general-relativistic static perfect fluid sphere. Finally, by returning to general diagonal coordinates and making a suitable ansatz for the functional form of the metric components, we place the Buchdahl transformation in its most general possible setting.

Y. Ng, Y. Ng, H. Dam

Abstract A recent paper (gr-qc/9909017) criticizes our work on the structure of spacetime foam. Its authors argue that the quantum uncertainty limit for the position of the quantum clock in a gedanken timing experiment, obtained by Wigner and used by us, is based on unrealistic assumptions. Here we point out some flaws in their argument. We also discuss their other comments and some other issues related to our work, including a simple connection to the holographic principle. We see no reason to change our cautious optimism on the detectability of spacetime foam with future refinements of modern gravitational-wave interferometers like LIGO/VIRGO and LISA.

M. Kuchiev, V. Flambaum

The absorption cross section for scalar particle impact on a Schwarzschild black hole is found. The process is dominated by two physical phenomena. One of them is the well-known greybody factor that arises from the energy-dependent potential barrier outside the horizon that filters the incoming and outgoing waves. The other is related to the reflection of particles on the horizon (M.Yu. Kuchiev, gr-qc/0310008, [19,20]). This latter effect strongly diminishes the cross section for low energies, forcing it to vanish in the infrared limit. It is argued that this is a general property, the absorption cross section vanishes in the infrared limit for scattering of particles of arbitrary spin.

M. Salti, A. Havare

This paper has been removed by arXiv administrators because it plagiarizes gr-qc/0011027, gr-qc/0205028, and gr-qc/0303034.