On the final state of spherical gravitational collapse

Following our recent finding [1] that, for the final state of continued spherical gravitational collapse of sufficiently massive bodies, the final gravitational mass of the fluidM _? → 0, we show that for a physical fluid the eventual value of 2M_?/R_? → 1 rather than 2M_?/R_?2M_?/R_? < 1 (the speed of light c = 1 and the gravitational constantG = 1), indicating the approach to a zero-mass black hole. We also point out that, as the final state is approached, the curvature components tend to blow up; also the proper radial distancel and the proper time (measured along a radial worldline) Τ → ∞, indicating that actually the singularity is never attained. We also identify that the final state may correspond to the local 3-speed attaining eitherV = 0 orV → c, even though invariant circumference contraction speedU =dR/dΤ → 0. Nonetheless, at a finite observation epoch, such Eternally Collapsing Objects (ECOs) may have a local speed of collapseV?c and the lab frame speed of collapse may be negligible because of high surface gravitational redshift. However, if quantum back reaction in the strong gravity regime would cause a phase transition of the form pressurep = - ρ, where ρ is the density of the collapsing fluid, it may be possible to have static Ultra Compact Objects (ûCOs) of arbitrary high mass [2]. While supposed Black Holes have no intrinsic magnetic field, ECOs or UCOs are likely to possess strong intrinsic magnetic fields, and we point out that there are already some tentative evidence for existence of such intrinsic magnetic fields in some Black Hole Candidates [3,4]. For the benefit of the readers who may not have gone through Paper I, we also include here the summary of the same. It clearly shows that the central result of Paper I can be derived even without knowing the meaning of the nomenclatureV or without imposing any of property ofV such as whetherV < 1 or not. In addition, we consolidate the same result from other physical considerations too.     

Neutrinos from CNO cycle at the present epoch of the solar neutrino research

The CNO cycle contributes only a small fraction to the energy generated in the Sun but there’s still no experimental data on exactly how small this contribution is. After the results of Borexino experiment the CNO neutrinos it is the last missing chain to compose the total picture of the energy generation of the Sun. To get precision in the evaluation of the flux of pp-neutrinos one needs to measure the flux of CNO neutrinos. Then it will be possible to address the question on the presence of still unknown (hidden) sources of solar energy and/or on the presence of sterile neutrinos. The future experimental program to measure the effect from CNO neutrinos is discussed.     

On gravitational radiation and the energy flux of matter

A suitable derivative of Einstein's equations in the framework of the teleparallel equivalent of general relativity (TEGR) yields a continuity equation for the gravitational energy‐momentum. In particular, the time derivative of the total gravitational energy is given by the sum of the total fluxes of gravitational and matter fields energy. We carry out a detailed analysis of the continuity equation in the context of Bondi and Vaidya's metrics. In the former space‐time the flux of gravitational energy is given by the well known expression in terms of the square of the news function. It is known that the energy definition in the realm of the TEGR yields the ADM (Arnowitt‐Deser‐Misner) energy for appropriate boundary conditions. Here we show that the same energy definition also describes the Bondi energy. The analysis of the continuity equation in Vaidya's space‐time shows that the variation of the total gravitational energy is determined by the energy flux of matter only.     

Weighing Neutrinos in f(R) Gravity in Light of BICEP2

We constrain the neutrino mass in f(R) gravity using the latest observations from the Planck, BAO and BICEP2 data. We find that the measurement on the B-modes can break the degeneracy between the massive neutrinos and the f(R) gravity. We find a non-zero value of the Compton wavelengths B0 at a 68% confidence level for the f(R) model in the presence of massive neutrinos when the BICEP2 data is used. Furthermore, the tension on the tensor-to-scalar ratios between the measured values from Plank and BICEP2 is significantly reconciled in our model.     

分仓颗粒布居分聚现象的通量模型

置于以窗口连接的分隔仓中振动驱动的颗粒气体会出现颗粒在两仓中布居分聚现象,被形象地称为麦克斯韦妖现象.通量模型的建立是理解麦克斯韦妖现象的关键问题.Eggers以颗粒气体动力学为基础得出了简化的理论模型.该模型可以很好地得到分仓中颗粒的布居分聚现象,然而似乎无法用于预测两种颗粒在分仓体系中的布居振荡现象.通过实验研究,测量了颗粒气体的流通量曲线,改进了Eggers模型.改进的模型可以很好地得到两种颗粒在分仓体系中的布居振荡现象. 关键词： 颗粒气体 耗散 通量模型     

Weighing Neutrinos in f(R) Gravity in Light of BICEP2

We constrain the neutrino mass in f(R) gravity using the latest observations from the Planck, BAO and BICEP2 data. We find that the measurement on the B-modes can break the degeneracy between the massive neutrinos and the f(R) gravity. We find a non-zero value of the Compton wavelengths B₀ at a 68% confidence level for the f(R) model in the presence of massive neutrinos when the BICEP2 data is used. Furthermore, the tension on the tensor-to-scalar ratios between the measured values from Plank and BICEP2 is significantly reconciled in our model.     

Gravitational collapse of dissipative fluid as a source of gravitational waves

Gravitational collapse of cylindrical anisotropic fluid has been considered in analogy with the work of Misner and Sharp. Using Darmois matching conditions, the interior cylindrical dissipative fluid (in the form of shear viscosity and heat flux) is matched to an exterior vacuum Einstein–Rosen space–time. It is found that on the bounding 3-surface the radial pressure of the anisotropic perfect fluid is linearly related to the shear viscosity and the heat flux of the dissipative fluid on the boundary. This non-zero radial pressure on the bounding surface may be considered as the source of gravitational waves outside the collapsing matter distribution.     

Incompressibility of strange matter

Strange stars (ReSS) calculated from a realistic equation of state (EOS), that incorporate chiral symmetry restoration as well as deconfinement at high density [Phys. Lett. B 438 (1998) 123; Phys. Lett. B 447 (1999) 352, Addendum; Phys. Lett. B 467 (1999) 303, Erratum; Indian J. Phys. B 73 (1999) 377] show compact objects in the mass radius curve. We compare our calculations of incompressibility for this EOS with that of nuclear matter. One of the nuclear matter EOS has a continuous transition to ud-matter at about five times normal density. Another nuclear matter EOS incorporates density dependent coupling constants. From a look at the consequent velocity of sound, it is found that the transition to ud-matter seems necessary.     

Detection of Supernova Neutrinos on the Earth for Large θ_(13)

Supernova （SN） neutrinos detected on the Earth are subject to the shock wave effects, the Mikheyev- Smirnov-Wolfenstein （MSW） effects, the neutrino collective effects and the Earth matter effects. Considering the recent experimental result about the large mixing angle 013 （-8.8°） provided by the Daya Bay Collaboration and applying the available knowledge for the neutrino conversion probability in the high resonance region of SN, PH , which is in the form of hypergeometric function in the case of large 813, we deduce the expression of PH taking into account the shock wave effects. It is found that PH is not zero in a certain range of time due to the shock wave effects. After considering all the four physical effects and scanning relevant parameters, we calculate the event numbers of SN neutrinos for the ＂Garehing＂ distribution of neutrino energy spectrum. From the numerical results, it is found that the behaviors of neutrino event numbers detected on the Earth depend on the neutrino mass hierarchy and neutrino spectrum parameters including the dimensionless pinching parameter βa （where a refers to neutrino flavor）, the average energy 〈Ea〉, and the SN neutrino luminosities La. Finally, we give the ranges of SN neutrino event numbers that will be detected at the Daya Bay experiment.     

Bose-Einstein condensation of anti-kaons and neutron star twins

We investigate the role of Bose-Einstein condensation (BEC) of anti-kaons on the equation of state (EoS) and other properties of compact stars. In the framework of relativistic mean field model we determine the EoS for β-stable hyperon matter and compare it to the situation when anti-kaons condense in the system. We observe that anti-kaon condensates soften the EoS, thereby lowering the maximum mass of the stars. We also demonstrate that the presence of antikaon condensates in the high density core of compact stars may lead to a new mass sequence beyond white dwarf and neutron stars. The limiting mass of the new sequence stars is nearly equal to that of neutron star branch though they have distinctly different radii and compositions. They are called neutron star twins.     

Challenging the paradigm of singularity excision in gravitational collapse

A paradigm deeply rooted in modern numerical relativity calculations prescribes the removal of those regions of the computational domain where a physical singularity may develop. We here challenge this paradigm by performing three-dimensional simulations of the collapse of uniformly rotating stars to black holes without excision. We show that this choice, combined with suitable gauge conditions and the use of minute numerical dissipation, improves dramatically the long-term stability of the evolutions. In turn, this allows for the calculation of the waveforms well beyond what was previously possible, providing information on the black-hole ringing and setting a new mark on the present knowledge of the gravitational-wave emission from the stellar collapse to a rotating black hole.     

Analysis of a charged unidirectional perfect fluid gravitational collapse in cylindrical spacetime

The gravitational collapse of charged imperfect fluids (including the presence of strings) models the structural evolution of the Universe. The dynamics of a charged cylindrically symmetric spacetime investigates the effects of charge on the rate of gravitational collapse. In this respect, the Einstein–Maxwell equations are formed and solved to obtain the values of the dynamical parameters of the fluid including density, pressure and electric field. These parameters are graphically presented. It was concluded that the string tension effects all the physical parameters of the fluid. Moreover, the density and electric field intensity increases while the fluid’s pressure decreases near the time of singularity formation.     

The structure of naked singularity in self-similar gravitational collapse: II

Generalizing the results of Joshi and Dwivedi inComm. Math. Phys. 146, 333 (1992), it is pointed out that strong curvature naked singularities could occur in the self-similar gravitational collapse of any form of matter satisfying the weak energy condition for the positivity of mass-energy density.     

Reconstruction of heat flux profile on the HL-2A divertor plate with a three-dimensional analysis model

A three-dimensional analysis model based on the finite element method (FEM) is developed, which can derive the evolution and distribution characteristics of heat flux deposited on the divertor plate from the surface temperature measured by infrared thermography diagnostics. The numerical simulations of surface heating due to localized power bursts and the power deposition calculations demonstrate that this analysis can provide accurate results and useful information about localized hot spots compared with the normal one- and two-dimensional calculations. In this paper, the details of this three-dimensional analysis are presented, and some results in ohmic heating and electron cyclotron resonant heating (ECRH) discharge on HL-2A are given.     

Neutrinos in dense quark matter and cooling of compact stars

We discuss that observational constraints on neutrino cooling processes may restrict the spectrum of quark matter phases admissible for compact star interiors.     

Dirac Neutrinos in the Seesaw Mechanism: Violation of the Number of Dirac Neutrinos

Physics of Atomic Nuclei - The seesaw mechanism, which explains the smallness of the neutrino masses by the involvement of high Majorana masses, leads to particles of the same Majorana nature and...