Formation of intermediate-mass black holes as primordial black holes in the inflationary cosmology with running spectral index

Formation of primordial black holes (PBHs) on astrophysical mass scales is a natural consequence of inflationary cosmology, if the primordial perturbation spectrum has a large and negative running of the spectral index as observationally suggested today because double inflation is required to explain it and fluctuations on some astrophysical scales are enhanced in the field-oscillation regime in between. It is argued that PBHs thus produced can serve as intermediate-mass black holes (IMBHs), which act as the observed ultraluminous X-ray sources (ULXs) by choosing appropriate values of the model parameters in their natural ranges. Our scenario can be observationally tested in near future because the mass of PBHs is uniquely determined once we specify the values of the amplitude of the curvature perturbation, spectral index and its running on large scales.     

New Estimates of the Merger Rate of Primordial Black Holes with Allowance for Clustering Dark Matter

Astronomy Letters - The merger rate of primordial black holes (PBHs) is numerically estimated by taking into account the gravitational interaction of PBHs with clustering cold dark matter (DM). The...     

Milagro limits and HAWC sensitivity for the rate-density of evaporating Primordial Black Holes

Primordial Black Holes (PBHs) are gravitationally collapsed objects that may have been created by density fluctuations in the early universe and could have arbitrarily small masses down to the Planck scale. Hawking showed that due to quantum effects, a black hole has a temperature inversely proportional to its mass and will emit all species of fundamental particles thermally. PBHs with initial masses of ∼5.0 × 10¹⁴ g should be expiring in the present epoch with bursts of high-energy particles, including gamma radiation in the GeV–TeV energy range. The Milagro high energy observatory, which operated from 2000 to 2008, is sensitive to the high end of the PBH evaporation gamma-ray spectrum. Due to its large field-of-view, more than 90% duty cycle and sensitivity up to 100 TeV gamma rays, the Milagro observatory is well suited to perform a search for PBH bursts. Based on a search on the Milagro data, we report new PBH burst rate density upper limits over a range of PBH observation times. In addition, we report the sensitivity of the Milagro successor, the High Altitude Water Cherenkov (HAWC) observatory, to PBH evaporation events.     

Evolution of Primordial Black Holes in Loop Quantum Cosmology

In this work, we study the evolution of primordial black holes within the context of loop quantum cosmology. First we calculate the scale factor and energy density of the Universe for different cosmic era and then taking these as inputs, we study evolution of primordial black holes. From our estimation it is found that accretion of radiation does not affect evolution of primordial black holes in loop quantum cosmology. We also conclude that due to slow variation of scale factor, the upper bound on initial mass fraction of presently evaporating PBHs are much greater in loop quantum cosmology than the standard case.     

Primordial black holes

Primordial black holes(PBHs) are a profound signature of primordial cosmological structures and provide a theoretical tool to study nontrivial physics of the early Universe.The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum,or effects of PBH evaporation,are shown to restrict a wide range of particle physics models,predicting an enhancement of the ultraviolet part of the spectrum of density perturbations,early dust-like stages,first order phase transitions and stages of superheavy metastable particle dominance in the early Universe.The mechanism of closed wall contraction can lead,in the inflationary Universe,to a new approach to galaxy formation,involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.     

Primordial black holes

Primordial black holes (PBHs) are a profound signature of primordial cos-mological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum, or effects of PBH evaporation, are shown to re-strict a wide range of particle physics models, predicting an enhancement of the ul-traviolet part of the spectrum of density perturbations, early dust-like stages, first or-der phase transitions and stages of superheavy metastable particle dominance in the early Universe. The mechanism of closed wall contraction can lead, in the inflation-ary Universe, to a new approach to galaxy formation, involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.     

The search for GRB from primordial black hole evaporation

The search for high energy ray bursts (GRBs) from primordial black holes (PBHs) has continued for the past 20 years. We discuss a very interesting group of GRBs of very short time duration and an increasing hard spectrum from the published BATSE catalog. We point out that the trend, i.e. anti-correlation of hardness ratio vs. GRB duration, would be expected if some of the short GRBs came from black holes evaporation. We discuss the possibility that the onset of the quark-gluon plasma can give rise to such GRB from PBH evaporation.     

Cosmic ray antiprotons from nearby cosmic accelerators

The antiproton flux measured by PAMELA experiment might have originated from Galactic sources of cosmic rays. These antiprotons are expected to be produced in the interactions of cosmic ray protons and nuclei with cold protons. Gamma rays are also produced in similar interactions inside some of the cosmic accelerators. We consider a few nearby supernova remnants observed by Fermi LAT. Many of them are associated with molecular clouds. Gamma rays have been detected from these sources which most likely originate in decay of neutral pions produced in hadronic interactions. The observed gamma ray fluxes from these SNRs are used to find out their contributions to the observed diffuse cosmic ray antiproton flux near the earth.     

GRBs on probation: Testing the UHE CR paradigm with IceCube

Gamma ray burst (GRB) fireballs provide one of very few astrophysical environments where one can contemplate the acceleration of cosmic rays to energies that exceed 10²⁰ eV. The assumption that GRBs are the sources of the observed cosmic rays generates a calculable flux of neutrinos produced when the protons interact with fireball photons. With data taken during construction IceCube has already reached a sensitivity to observe neutrinos produced in temporal coincidence with individual GRBs provided that they are the sources of the observed extra-galactic cosmic rays. We here point out that the GRB origin of cosmic rays is also challenged by the IceCube upper limit on a possible diffuse flux of cosmic neutrinos which should not be exceeded by the flux produced by all GRB over Hubble time. Our alternative approach has the advantage of directly relating the diffuse flux produced by all GRBs to measurements of the cosmic ray flux. It also generates both the neutrino flux produced by the sources and the associated cosmogenic neutrino flux in a synergetic way.     

On the mechanisms producing the backscattered and the trapped electrons along auroral field lines

The production mechanisms of backscattered electrons and trapped electrons along auroral field lines are examined. The backscattered electrons are produced not only by electron-neutral collisions, but also by electrostatic turbulence predominantly in the ion-cyclotron and ion-acoustic modes. The trapped electrons can only be produced by electron wave turbulence, most likely in the whistler and upper hybrid modes known as the auroral hiss.     

A Hall MHD model to study energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity

Energetic charged particles, which are often observed in solar active regions, may be also produced in interplanetary space due to the decoupling of ions and electrons in plasma. The Hall term in general Ohm's law is generally thought to be responsible for the decoupling of electrons and ions in plasma during magnetic reconnection. In this paper, a Hall MHD model is developed to study energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity. Two energetic charged particle events are used to test this model. It is concluded that the Hall effect does not only play the important role in the process of magnetic reconnection, but also in energetic charged particle events produced during fluctuations in the interplanetary magnetic field intensity.     

Plasma clouds in Saturn's rings

The expansion and ionization of vapor produced by impacts of meteorites on Saturn's rings is described. There is an “impact plasma” produced in the initial collision, and a “secondary plasma” produced by subsequent ionization of the neutral gas ejecta. The dynamics of these plasma clouds, their size, density, and life time are calculated. It is suggested that large clouds, produced by meter-sized meteorites (or a collection of such clouds produced, e.g., by the impact of a swarm of meteorites) may lead to the formation of spokes by the mechanism discussed in Goertz, C. K., and Morfill, G. E. (Icarus53, 219–229, 1983).     

An analytic model for upper atmosphere densities based upon Jacchia's 1970 models

An analytic model is presented which gives upper atmospheric densities as a function of the exospheric temperature and the altitude. The densities produced are identical to those produced by Jacchia's 1970 models (1970) for altitudes between 90 and 125 km and closely approximate Jacchia's values for altitudes greater than 125 km.     

PeV gamma rays from interactions of ultra high energy cosmic rays in the Milky Way

The PeV gamma ray background produced in the interactions of ultra high energy cosmic rays with the ambient matter and radiations during their propagation in the Milky Way has been calculated in this paper. If the primary ultra high energy cosmic rays are produced from Galactic point sources then those point sources are also emitting PeV gamma rays. We discuss that the detection of galactocentric PeV gamma rays in the future would be a signature of the presence of EeV cosmic accelerators in the Milky Way.     

Model dependence of transonic properties of accretion flows around black holes

We analytically study how the behaviour of accretion flows changes when the flow model is varied. We study the transonic properties of the conical flow, a flow of constant height and a flow in vertical equilibrium, and show that all these models are basically identical, provided that the polytropic constant is suitably changed from one model to another. We show that this behaviour is extendible even when standing shocks are produced in the flow. The parameter space where shocks are produced remains roughly identical in all these models when the same transformation among the polytropic indices is used. We present applications of these findings.     

Helium formation in a class of radiative cosmological models

Helium formation is studied in a class of exact radiation-filled cosmological models in which the space-time geometry is represented by the Friedmann-Robertson-Walker metric and the source of the gravitational field is a non-co-moving imperfect fluid. Using the methods described by Barrow (1984) we find it possible to calculate the predicted helium-4 abundance in the class of radiative models analytically in terms of the results in the corresponding standard model. It is found that different amounts of helium-4 are produced at different space-time locations in the models. It is also found that while there is less helium-4 produced than in the standard model, the models give rise to predictions for the primordial helium-4 abundance within the observed range. In view of current estimates for the pre-galactic helium abundance and the predictions obtained from the standard model, models in which less helium is produced are of particular interest. The techniques employed in the calculation are discussed, and the assumptions and approximations that have been made are described in some detail.     

Patterns of fracture and tidal stresses on Europa

the hypothesis that lineaments on Europa are fractures produced by tidal distortion and planetary volume change is examined by comparing the orientations of dark bands, triple bands, and cuspate ridges to fracture patterns predicted for tidal distortion due to orbital recession and orbital eccentricity. If short, reticulate dark band nnear the anti-Jove point are tension cracks which formed in response to tidal distortion, they could only have been produced by orbital eccentricity. Long, arcuate dark band and triple bands peripheral to the anti-Jove point orientations which suggest that they are strike-slip faults which formed in response to orbital recession. If cuspate ridges are compressional features, their orientations and distribution suggest that they formed in response to combined orbital recession and a decrease in planetary volume. Stresses due to orbital eccentricit could have produced tension cracks near the anti-Jove point only if tensile failure occurred either prior to the accumulation of orbital recession stresses or after they had relaxed. Surface fracturing, if a consequence of tidal deformation, places important constraints on the orbital evolution of Europa.     

Impacts as sources of the exosphere on Mercury

Chemical processes associated with meteoroid bombardment of Mercury are considered. Meteoroid impacts lead to production of metal atoms as well as metal oxides and hydroxides in the planetary exosphere. By using quenching theory, the abundances of the main Na-, K-, Ca-, Fe-, Al-, Mg-, Si-, and Ti-containing species delivered to the exosphere during meteoroid impacts were estimated. Based on a correlation between the solar photo rates and the molecular constants of atmospheric diatomic molecules, photolysis lifetimes of metal oxides and SiO are estimated. Meteoroid impacts lead to the formation of hot metal atoms (0.2-0.4 eV) produced directly during impacts and of very hot metal atoms (1-2 eV) produced by the subsequent photolysis of oxides and hydroxides in the exosphere of Mercury. The concentrations of impact-produced atoms of the main elements in the exosphere are estimated relative to the observed concentrations of Ca, assumed to be produced mostly by ion sputtering. Condensation of dust grains can significantly reduce the concentrations of impact-produced atoms in the exosphere. Na, K, and Fe atoms are delivered to the exosphere directly by impacts while Ca, Al, Mg, Si, and Ti atoms are produced by the photolysis of their oxides and hydroxides. The chemistry of volatile elements such as H, S, C, and N during meteoroid bombardment is also considered. Our conclusions about the temperature and the concentrations of impact-produced atoms in the exosphere of Mercury may be checked by the Messenger spacecraft in the near future and by BepiColombo spacecraft some years later.     

Excess Xenon-128 in meteorites

Using known compositions of primordial and spallation xenon components in several meteorites, the neutron produced Xe¹²⁸ⁿ has been resolved. For obtaining the value for spallation produced (Xe¹²⁸/Xe¹³⁰)_c, the meteorites with low iodine content and high spallation contribution are considered. Using these data, the neutron densities in several meteorites due to cosmic-ray exposure are calculated and their significance is qualitatively discussed.     

Further studies of directional E-layer currents

Previous work showed that thin ionized layers in the ionospheric E-region conduct electric current only towards the magnetic equator, if the layers are formed by wind-shears associated with “corkscrew” tidal winds. The present paper extends this work and considers also the shears produced by height-independent winds and fields near the “transition” between collision-dominated and magnetically-dominated ion motion; the layers thus produced carry current in the poleward direction.