Hawking’s radiation in non-stationary rotating de Sitter background

Hawking’s radiation effect of Klein-Gordon scalar field, Dirac particles and Maxwell’s electromagnetic field in the non-stationary rotating de Sitter cosmological space-time is investigated by using a method of generalized tortoise co-ordinates transformation. The locations and the temperatures of the cosmological horizons of the non-stationary rotating de Sitter model are derived. It is found that the locations and the temperatures of the rotating cosmological model depend not only on the time but also on the angle. The stress-energy regularization techniques are applied to the two dimensional analog of the de Sitter metrics and the calculated stress-energy tensor contains the thermal radiation effect.     

New tortoise coordinate transformation and Hawking’s radiation in de Sitter space

Hawking’s radiation effect of Klein-Gordon equation, Dirac particles and Maxwell’s electromagnetic fields in the non-stationary rotating de Sitter cosmological space-time is investigated by using a new method of generalized tortoise coordinate transformation. It is found that the new transformation produces constant additional terms in the expressions of the surface gravities and the Hawking’s temperatures. If the constant terms are set to zero, then the surface gravities and Hawking’s temperatures will be equal to those obtained from the old generalized tortoise coordinate transformations. This shows that the new transformations are more reasonable. The Fermionic spectrum of Dirac particles displays a new spin-rotation coupling effect.     

Hawking non-thermal and thermal radiations of Reissner Nordström anti-de Sitter black hole by Hamilton-Jacobi method

We have investigated Hawking non-thermal and purely thermal Radiations of Reissner Nordström anti-de Sitter (RNAdS) black hole by massive particles tunneling method. The spacetime background has taken as dynamical, incorporate the self-gravitation effect of the emitted particles the imaginary part of the action has derived from Hamilton-Jacobi equation. We have supposed that energy and angular momentum are conserved and have shown that the non-thermal and thermal tunneling rates are related to the change of Bekenstein-Hawking entropy and the derived emission spectrum deviates from the pure thermal spectrum. The results for RNAdS black hole is also in the same manner with Parikh and Wilczek’s opinion and explored the new result for Hawking radiation of RNAdS black hole.     

Nernst theorem and Hawking radiation from a Reissner-Nordstrom black hole

The thermal character of inner horizon in a Reissner-Nordstrom black hole is studied via Hamilton-Jacobi method. There is “Hawking absorption” as a quantum effect near the inner horizon, and a negative temperature of the inner horizon was attained by choosing an observer outside the black hole. Using a redefined entropy of the black hole, we give a new expression of Bekenstein-Smarr formula. The redefined entropy satisfies Nernst Theorem, so it can be regarded as Planck absolute entropy of the Reissner-Nordstrom black hole.     

Apparent horizon and event horizon thermodynamics of?a?Vaidya?black hole using Damour-Ruffini method

Using Damour-Ruffini method, Hawking radiation from the apparent horizon of a Vaidya black hole is calculated. The thermodynamics can be built successfully on the apparent horizon. In the meantime, when a time-dependent perturbation is given to the apparent horizon, the first law of thermodynamics can also be constructed successfully at a new supersurface near the apparent horizon. The expressions of the characteristic position and temperature are consistent with the previous results. It is concluded that the thermodynamics should be constructed on the apparent horizon exactly while the event horizon thermodynamics is just one of the perturbations near the apparent horizon. These conclusions can be regarded as providing some new evidences for our previous viewpoint.     

Quasinormal modes and Hawking radiation of a Reissner-Nordström black hole surrounded by quintessence

We investigate quasinormal modes (QNMs) and Hawking radiation of a Reissner-Nordström black hole surrounded by quintessence. The Wentzel-Kramers-Brillouin (WKB) method is used to evaluate the QNMs and the rate of radiation. The results show that due to the interaction of the quintessence with the background metric, the QNMs of the black hole damp more slowly when increasing the density of quintessence and the black hole radiates at slower rate.     

Phase transition in the Reissner–Nordström black hole

The thermodynamics of the Reissner–Nordström black hole at the charge-to-mass ratio of \(\sqrt{3}/2\) is studied. We show that there exists infinite discontinuity not only in the heat capacity but also in the electromagnetic potential and hence in the Gibbs free energy. Despite the existence of an infinite discontinuity in the heat capacity, it is shown that there exists no phase transition in the Reissner–Nordström black hole. The discontinuity may be merely an artefact of the change in the slope of the |Q| vs. M curve when the charge-to-mass ratio crosses \(\sqrt{3}/2\). This may signify that the horizon temperature is not a well-behaved thermodynamic parameter in the black hole thermodynamics.     

Entanglement entropy of acoustic black hole in Bose–Einstein condensate

We study the entanglement entropy associated to the phonons generated via the Hawking mechanism of acoustic black holes in a Bose–Einsten condensate. The lowest energy allowed for the radiated phonons is found to be a function of space coordinate. Based this, we calculate the entanglement entropy, which contains three parts: a leading term, which is a constant of value 1/6, a logarithmic correction term and some series terms. We discuss the convergence of the series terms.     

Hot plasma waves in Veselago medium around Reissner-Nordström black hole

We investigate the general relativistic magnetohydronadynamic (GRMHD) equations for hot plasmas in a Veselago medium around the Reissner-Nordström (RN) black hole. Using the 3+1 formalisms of spacetime, we write the GRMHD equations and perturb them linearly. These are then Fourier analyzed for the magnetized and nonmagnetized plasmas in rotating and nonrotating backgrounds. We derive dispersion relations and analyze the wave properties by the graphs of wave vector, refractive index and change in refractive. The results confirm the presence of Veselago medium for rotating magnetized/nonmagnetized and nonrotating nonmagnetized plasmas.     

Thermodynamics of phantom energy in the presence of a Reissner-Nordström black hole

In this paper, we study the validity of the generalized second law (GSL) in phantom dominated universe in the presence of a Reissner-Nordström (RN) black hole. Our study is independent of the origin of the phantom like behavior of the considered universe. We also discuss the GSL in the neighborhood of transition from quintessence to phantom regime. We show that for a constant equation of state parameter, the GSL may be satisfied provided that the temperature is proportional to de Sitter temperature. It is shown that in models with (only) a transition from quintessence to phantom regime the generalized second law does not hold in the transition epoch. Next we show that if the phantom energy has a chemical potential, then the GSL will hold if the mass of black hole is above from a critical value.     

Study of space debris burning in Earth’s atmosphere via television meteor monitoring

The observations on ground-based facilities miss multitudes of small fragments of space debris. However, the intrusion of fine particles into the atmosphere and their subsequent burning can be observed along with the usual meteor phenomena. Since the solar system meteoric body velocities at the entry into the atmosphere are over 11.2 km/s, and the velocity of the space debris objects does not exceed 11.2 km/s, the selection of meteors by velocity is a reliable criterion for separating these bodies. The paper describes a method of selecting the space debris fragments using a technique of television meteor monitoring. The technique was adapted on the material of real television observations on the FAVOR wide-field monitoring camera with high temporal resolution, conducted in 2006 in the Arkhyz station of the Institute for Precision Instrumentation (North Caucasus).     

The Vega project: A space mission to Venus and Halley’s comet

The launch of the Soviet space probes Vega 1 and Vega 2 to explore Venus, including its atmosphere, and flyby Halley??s comet, a rare guest in the inner Solar System, added a vivid page to the history of space exploration. This paper is dedicated to Designer General Vyacheslav M. Kovtunenko.     

On accounting for temperature and pressure in determining the Rayleigh scattering in the earth’s atmosphere

We calculated the variations of Rayleigh optical depth with changes of pressure and temperature for three observation sites: Simferopol (φ = 44°57′N, λ = 34°8′E, h = 265 m above sea level), Nauchny (φ = 44°43′N, λ = 34°3′E, h = 583 m), and Ai-Petry meteorological station (φ = 44°24′N, λ = 34°6′E, h = 1180 m).     

High altitude haze: Influence of monomer particles on Titan’s temperature profile

The present study investigates the role of high altitude monomer particles in the energy balance of Titan’s upper atmosphere above an assumed low and high aggregate formation altitude of 385 km and 535 km. A ‘single particle approach’ was applied, where the starting point is the energy balance of an individual aerosol. In our analysis 0.01–0.06 μm radius aerosol particles were chosen for the proposed monomer formation regions. These particles absorb solar radiation, emit in the infrared, and are energetically linked to the surrounding gas by thermal conduction. To compute the monomer particle heating effect, the aerosols are assumed to radiate directly to space. We found that high altitude monomers may affect the profile of Titan’s thermosphere from 2 to 20 K depending on the formation altitude of fluffy non-spherical aggregates, the monomer size and distribution. The actual Titan temperature profile in this altitude range including all heating effects will be measured by the HASI instrument during the descent of the Huygens probe.     

Does black hole spin play a key role in the FSRQ/BL Lac dichotomy?

Blazars are characterized by large intensity and spectral variations across the electromagnetic spectrum It is believed that jets emerging from them are almost aligned with the line-of-sight. The majority of identified extragalactic sources in γ-ray catalogs of EGRET and Fermi are blazars. Observationally,blazars can be divided into two classes: flat spectrum radio quasars(FSRQs) and BL Lacs. BL Lacs usually exhibit lower γ-ray luminosity and harder power law spectra at γ-ray energies than FSRQs. We attempt to explain the high energy properties of FSRQs and BL Lacs from Fermi γ-ray space telescope observations. It was argued previously that the difference in accretion rates is mainly responsible for the large mismatch in observed luminosity in γ-ray. However, when intrinsic luminosities are derived by correcting for beaming effects, this difference in γ-ray luminosity between the two classes is significantly reduced. In order to explain this difference in intrinsic luminosities, we propose that spin plays an important role in the luminosity distribution dichotomy of BL Lacs and FSRQs. As the outflow power of a blazar increases with increasing spin of a central black hole, we suggest that the spin plays a crucial role in making BL Lac sources low luminous and slow rotators compared to FSRQ sources.     

Enigmatic aspects of entropy inside the black hole: what do falling comoving observers see?

In a recent paper it was suggested that inclusion of mutual gravitational interactions can give a possible scenario for reversing gravitation collapse and averting a singular phase. We extend this idea to the still unsolved problem of matter collapsing beyond black hole event horizons. For a comoving observer there is no change in entropy as he goes through the horizon. Matter collapses to a minimum radius, and then can re-expand with the same entropy. It is shown that phase space inside a collapsing black hole is also invariant.     

Benford’s Distribution in Extrasolar World: Do the Exoplanets Follow Benford’s Distribution?

In many real life situations, it is observed that the first digits (i.e., 1,2,…,9) of a numerical data-set, which is expressed using decimal system, do not follow a uniform distribution. In fact, the probability of occurrence of these digits decreases in an almost exponential fashion starting from 30.1 % for 1 to 4.6 % for 9. Specifically, smaller numbers are favoured by nature in accordance with a logarithmic distribution law, which is referred to as Benford’s law. The existence and applicability of this empirical law have been extensively studied by physicists, accountants, computer scientists, mathematicians, statisticians, etc., and it has been observed that a large number of data-sets related to diverse problems follow this distribution. However, except two recent works related to astronomy, applicability of Benford’s law has not been tested for extrasolar objects. Motivated by this fact, this paper investigates the existence of Benford’s distribution in the extrasolar world using Kepler data for exoplanets. The quantitative investigations have revealed the presence of Benford’s distribution in various physical properties of these exoplanets. Further, some specific comments have been made on the possible generalizations of the obtained results, its potential applications in analysing the data-set of candidate exoplanets.     

Photoabsorption in Ganymede’s atmosphere

In the framework of future space missions to Ganymede, a pre-study of this satellite is a necessary step to constrain instrument performances according to the mission objectives. This work aims at characterizing the impact of the solar UV flux on Ganymede’s atmosphere and especially at deriving some key physical parameters that are measurable by an orbiter. Another objective is to test several models for reconstructing the solar flux in the Extreme-UV (EUV) in order to give recommendations for future space missions.Using a Beer–Lambert approach, we compute the primary production of excited and ionized states due to photoabsorption, neglecting the secondary production that is due to photoelectron impacts as well as to precipitated suprathermal electrons. Ions sputtered from the surface are also neglected. Computations are performed at the equator and close to the pole, in the same conditions as during the Galileo flyby. From the excitations, we compute the radiative relaxation leading to the atmospheric emissions. We also propose a simple chemical model to retrieve the stationary electron density. There are two main results: (i) the modelled electron density and the one measured by Galileo are in good agreement. The main atmospheric visible emission is the atomic oxygen red line at 630 nm, both in equatorial and in polar conditions, in spite of the different atmospheric compositions. This emission is measurable from space, especially for limb viewing conditions. The OH emission (continuum between 260 and 410 nm) is also probably measurable from space. (ii) The input EUV solar flux may be directly measured or reconstructed from only two passbands solar observing diodes with no degradation of the modelled response of the Ganymede’s atmosphere. With respect to these results, there are two main conclusions: (i) future missions to Ganymede should include the measurement of the red line as well as the measurement of OH emissions in order to constrain the atmospheric model. (ii) None of the common solar proxies satisfactorily describes the level of variability of the solar EUV irradiance. For future atmospheric planetary space missions, it would be more appropriate to derive the EUV flux from a small radiometer rather than from a full-fledged spectrometer.