Lower limit on the entropy of black holes as inferred from gravitational wave observations

Black hole (BH) thermodynamics was established by Bekenstein and Hawking, who made abstract theoretical arguments about the second law of thermodynamics and quantum theory in curved spacetime respectively. Testing these ideas experimentally has, so far, been impractical because the putative flux of Hawking radiation from astrophysical BHs is too small to be distinguished from the rest of the hot environment. Here, it is proposed that the spectrum of emitted gravitational waves (GWs) after the merger of two BHs, in particular the spectrum of GW150914, can be used to infer a lower limit on the magnitude of the entropy of the post-merger BH. This lower bound is potentially significant as it could be of the same order as the Bekenstein-Hawking entropy. To infer this limit, we first assume that the result of the merger is an ultracompact object with an external geometry which is Schwarzschild or Kerr, but with an outer surface which is capable of reflecting in-falling GWs rather than fully absorbing them. If the absence of deviations from the predictions of general relativity in detected GW signals will be verified, we will then obtain a bound on the minimal redshift factor of GWs that emerge from the vicinity of the object's surface. This lack of deviations would also mean that the remnant of the merger has to have a strongly absorbing surface and must then be a BH for all practical purposes. We conclude that a relationship between the minimal redshift factor and the BH entropy, which was first proposed by 't Hooft, could then be used to set a lower bound on the entropy of the post-merger BH.Comment: Corrected error in estimation of current bounds on the entropy. Improved discussion of energy stored in echoes, V3 replaced to match published version, clarifications and explanations adde

Cosmic star formation history revealed by the AKARI, & Spatially-resolved spectroscopy of an E+A (Post-starburst) system

We reveal cosmic star-formation history obscured by dust using deep infrared observation with the AKARI. A continuous filter coverage in the mid-IR wavelength (2.4, 3.2, 4.1, 7, 9, 11, 15, 18, and 24um) by the AKARI satellite allows us to estimate restframe 8um and 12um luminosities without using a large extrapolation based on a SED fit, which was the largest uncertainty in previous work. We found that restframe 8um (0.38<z<2.2), 12um (0.15<z<1.16), and total infrared (TIR) luminosity functions (LFs) (0.2<z<1.6) constructed from the AKARI NEP deep data, show a continuous and strong evolution toward higher redshift. In terms of cosmic infrared luminosity density (Omega_IR), which was obtained by integrating analytic fits to the LFs, we found a good agreement with previous work at z<1.2, with Omega_IR propto (1+z)^4.4+-1.0. When we separate contributions to Omega_IR by LIRGs and ULIRGs, we found more IR luminous sources are increasingly more important at higher redshift. We found that the ULIRG (LIRG) contribution increases by a factor of 10 (1.8) from z=0.35 to z=1.4.Comment: To appear in "Hunting for the Dark: The Hidden Side of Galaxy Formation", Malta, 19-23 Oct. 2009, eds. V.P. Debattista & C.C. Popescu, AIP Conf. Se

Determination of Phosphorus in Low-Alloy Steels by Charged-Particle Activation Analysis

開始ページ、終了ページ: 冊子体のページ付

Determination of P, Cl, K and Ca in Several Control Serums by Alpha-Particle Activation Analysis Applying the New Internal Standard Method Coupled with the Standard Addition Method

開始ページ、終了ページ: 冊子体のページ付