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21.
We reveal unifying thermodynamic aspects of so different phenomena as the cosmological electron-positron annihilation, the evaporation of primordial black holes with a narrow mass range, and the "deflationary" transition from an initial de Sitter phase to a subsequent standard Friedmann–Lemaître–Robertson–Walker (FLRW) behavior. 相似文献
22.
C. Sivaram 《General Relativity and Gravitation》2001,33(2):175-181
Thermal Hawking emission from black holes is a remarkable consequence of the unification of quantum physics and gravitation. Black holes of a few solar masses are the only ones which can form in the present universe. However, having temperatures million times smaller than the ambient cosmic background radiation they cannot evaporate. Primordial black holes of M 1014g would evaporate over a Hubble age and considerable ongoing effort is on to detect such explosions. I point out, however, that at the early universe epochs when such black holes form, the ambient radiation temperature considerably exceeds their corresponding Hawking temperature. This results in rapid continual accretion (absorption) of ambient radiation by these holes. Consequently by the end of the radiation era their masses grow much greater so that their lifetimes (scaling as M3) would now be enormously greater than the Hubble age implying undetectably small emission. 相似文献
23.
Nils M. Bezares-Roder Hemwati Nandan Heinz Dehnen 《International Journal of Theoretical Physics》2007,46(10):2429-2436
The exact static and spherically symmetric solutions of the vacuum field equations for a Higgs Scalar-Tensor theory (HSTT)
are derived in Schwarzschild coordinates. It is shown that in general there exists no Schwarzschild horizon and that the fields
are only singular (as naked singularity) at the center (i.e. for the case of a point-particle). However, the Schwarzschild
solution as in usual general relativity (GR) is obtained for the vanishing limit of Higgs field excitations. 相似文献
24.
Abhay Ashtekar 《Pramana》2007,69(1):77-92
Basic features of dynamical black holes in full, non-linear general relativity are summarized in a pedagogical fashion. Qualitative
properties of the evolution of various horizons follow directly from the celebrated Raychaudhuri equation.
相似文献
25.
We report time-resolved transient spectral hole burning of Verneuil-grown 20 ppm and ca. 0.6 ppm ruby (Al2O3:Cr3+) in zero field and low magnetic fields B∥c at 4 K. The hole-burning spectroscopy of the 20 ppm sample implies relatively rapid cross relaxation in the 4A2 ground state on the ∼1 ms timescale both in zero field and in low magnetic fields, B∥c, up to 0.2 T. In the 0.6 ppm sample, side-hole to anti-hole conversion is observed both in zero field and in low magnetic fields. This conversion is caused by population storage in 4A2 ground state levels. Spin-lattice relaxation, on the 200 ms timescale, is directly observed from the time dependence of the resonant hole and anti holes in B∥c, consistent with a very low cross-relaxation rate. However, in zero field cross relaxation in the 4A2 ground state is still a significant relaxation mechanism for the 0.6 ppm sample resulting in hole decay in ∼50 ms. 相似文献
26.
《Comptes Rendus Physique》2013,14(4):352-365
The first generation of ground-based interferometric gravitational wave detectors, LIGO, GEO, and Virgo, have operated and taken data at their design sensitivities over the last few years. The data has been examined for the presence of gravitational wave signals. Presented here is a comprehensive review of the most significant results. The network of detectors is currently being upgraded and extended, providing a large likelihood for observations. These future prospects will also be discussed. 相似文献
27.
28.
New statistical ensembles of classical extreme black holes are introduced. Each ensemble is proven to represent a non extreme, finite temperature black hole. This mean or average black hole is surrounded by a mean electromagnetic field and a so-called apparent matter, which is the large scale trace of the averaged upon small scale fluctuations of the gravitational and electromagnetic fields. However, the total mass and the total charge of space-time is not modified by the averaging. 相似文献
29.
Alexis Larrafiaga 《理论物理通讯》2008,50(12):1341-1344
In this paper we study the first law of thermodynamics for the (2+1)-dimensional rotating charged BTZ black hole considering a pair of thermodynamical systems constructed with the two horizons of this solution. We show that these two systems are similar to the right and left movers of string theory and that the temperature associated with the black hole is the harmonic mean of the temperatures associated with these two systems. 相似文献
30.
Malcolm R. Davidson 《Transport in Porous Media》1987,2(2):165-176
An asymptotic, one-dimensional Green-Ampt model is derived for infiltration into a soil whose surface is impermeable except for regularly spaced vertical cracks, and infiltration into a cylindrical soil column whose top surface is also impermeable except for a central hole. The model is valid at times when the wetting front has become horizontal and corresponds to one-dimensional infiltration initiated from a plane lying above or below the soil surface, depending on the crack spacing/depth ratio (or column radius/hole depth ratio). When applicable, asymptotic Green-Ampt solutions are shown to agree well, in selected cases, with corresponding finite difference solutions of the saturated-unsaturated flow equations. 相似文献