Primordial Black Hole Research Papers (original) (raw)

2009

This thesis begins with a study of the origin of cosmological fluctuations with special attention to those cases in which the non-Gaussian correlation functions are large. The analysis shows that perturbations from an almost massless auxiliary field generically produce large values of the non-linear parameter f_NL. The effects of including non-Gaussian correlation functions in the statistics of cosmological structure are explored by constructing a non-Gaussian probability distribution function (PDF). Such PDF is derived for the comoving curvature perturbation from first principles in the context of quantum field theory, with n-point correlation functions as the only input. The non-Gaussian PDF is then used to explore two important problems in the physics of primordial black holes (PBHs): First, to compute non-Gaussian corrections to the number of PBHs generated from the primordial curvature fluctuations. The second application concerns new cosmological observables. The formation of PBHs is known to depend on two main physical characteristics: the strength of the gravitational field produced by the initial curvature inhomogeneity and the pressure gradient at the edge of the curvature configuration. We account for the probability of finding these configurations by using two parameters: The amplitude of the inhomogeneity and its second radial derivative, evaluated at the centre of the configuration. The implications of the derived probability for the fraction of mass in the universe in the form of PBHs are discussed.

2007, Classical and Quantum Gravity

We calculate the quantum radiation power of black holes which are asymptotic to the Einsteinde Sitter universe at spatial and null infinities. We consider two limiting mass accretion scenarios, no accretion and significant accretion. We find that the radiation power strongly depends on not only the asymptotic condition but also the mass accretion scenario. For the no accretion case, we consider the Einstein-Straus solution, where a black hole of constant mass resides in the dust Friedmann universe. We find negative cosmological correction besides the expected redshift factor. This is given in terms of the cubic root of ratio in size of the black hole to the cosmological horizon, so that it is currently of order 10 −5 (M/10 6 M⊙) 1/3 (t/14 Gyr) −1/3 but could have been significant at the formation epoch of primordial black holes. Due to the cosmological effects, this black hole has not settled down to an equilibrium state. This cosmological correction may be interpreted in an analogy with the radiation from a moving mirror in a flat spacetime. For the significant accretion case, we consider the Sultana-Dyer solution, where a black hole tends to increase its mass in proportion to the cosmological scale factor. In this model, we find that the radiation power is apparently the same as the Hawking radiation from the Schwarzschild black hole of which mass is that of the growing mass at each moment. Hence, the energy loss rate decreases and tends to vanish as time proceeds. Consequently, the energy loss due to evaporation is insignificant compared to huge mass accretion onto the black hole. Based on this model, we propose a definition of quasi-equilibrium temperature for general conformal stationary black holes.

2003

The principle of nuclear democracy is invoked to prove the formation of stable quantized gravitational bound states of primordial black holes called Holeums. The latter come in four varieties: ordinary Holeums H, Black Holeums BH, Hyper Holeums HH and the massless Lux Holeums LH.These Holeums are invisible because the gravitational radiation emitted by their quantum transitions is undetectable now. The

Physics Letters B 733 (2014) pp. 270-275

In this article we provide a new closed relationship between the cosmic abundance of primordial gravitational waves and primordial black holes originated from initial inflationary perturbations for a generic model of inflation where inflation occurs below the Planck scale. We have obtained a strict bound on the current abundance of primordial black holes from the Planck measurements, 9.99712times10−3<OmegaPBHh2<9.99736times10−39.99712\times 10^{-3}<\Omega_{PBH}h^{2}< 9.99736\times 10^{-3}9.99712times10−3<OmegaPBHh2<9.99736times10−3.

1999, Nuclear Physics B

During the preheating era after inflation, resonant amplification of quantum field fluctuations takes place. Recently it has become clear that this must be accompanied by resonant amplification of scalar metric fluctuations, since the two are united by Einstein's equations. Furthermore, this "metric preheating" enhances particle production, and leads to gravitational rescattering effects even at linear order. In multi-field models with strong preheating (q ≫ 1), metric perturbations are driven nonlinear, with the strongest amplification typically on super-Hubble scales (k → 0). This amplification is causal, being due to the super-Hubble coherence of the inflaton condensate, and is accompanied by resonant growth of entropy perturbations. The amplification invalidates the use of the linearized Einstein field equations, irrespective of the amount of fine-tuning of the initial conditions. This has serious implications on all scales -from large-angle cosmic microwave background (CMB) anisotropies to primordial black holes. We investigate the (q, k) parameter space in a two-field model, and introduce the time to nonlinearity, t nl , as the timescale for the breakdown of the linearized Einstein equations. t nl is a robust indicator of resonance behavior, showing the fine structure in q and k that one expects from a quasi-Floquet system, and we argue that t nl is a suitable generalization of the static Floquet index in an expanding universe. Backreaction effects are expected to shut down the linear resonances, but cannot remove the existing amplification, which threatens the viability of strong preheating when confronted with the CMB. Mode-mode coupling and turbulence tend to re-establish scale-invariance, but this process is limited by causality and for small k the primordial scale invariance of the spectrum may be destroyed. We discuss ways to escape the above conclusions, including secondary phases of inflation and preheating solely to fermions. The exclusion principle constrains the amplification of metric perturbations significantly. Finally we rank known classes of inflation from strongest (chaotic and strongly coupled hybrid inflation) to weakest (hidden sector, warm inflation), in terms of the distortion of the primordial spectrum due to these resonances in preheating. PACS: 98.80.Cq, 04.62.+v,05.70.Fh, hep-ph/9901319 (v3). Nuclear Physics B, in press † The most powerful use of this idea was in the Misner "chaotic cosmology" program whereby it was hoped that arbitrary initial anisotropy and inhomogeneity might be smoothed out by particle production .

2007, Eprint Arxiv 0708 3875

This paper explores the consequences of non-Gaussian cosmological perturbations for the formation of primordial black holes (PBHs). A non-Gaussian probability distribution function (PDF) of curvature perturbations is presented with an explicit contribution from the three-point correlation function to linear order. The consequences of this non-Gaussian PDF for the large perturbations that form PBHs are then studied. Using the observational limits for the non-Gaussian parameter fNLf_{NL}fNL, new bounds to the mean amplitude of curvature perturbations are derived in the range of scales relevant for PBH formation.

2009, Monthly Notices of the Royal Astronomical Society

If the cosmological dark matter has a component made of small primordial black holes, they may have a significant impact on the physics of the first stars and on the subsequent formation of massive black holes. Primordial black holes would be adiabatically contracted into these stars and then would sink to the stellar center by dynamical friction, creating a larger black hole which may quickly swallow the whole star. If these primordial black holes are heavier than ∼ 10 22 g, the first stars would likely live only for a very short time and would not contribute much to the reionization of the universe. They would instead become 10 − 10 3 M⊙ black holes which (depending on subsequent accretion) could serve as seeds for the super-massive black holes seen at high redshifts as well as those inside galaxies today.

Although Dark Matter (DM) apparently pervades the universe, it is rarely considered in the context of the formation of the Solar System and other planetary systems. However, a relatively small but non-negligible fraction of the mass of any such systems would consist of DM gravitationally captured during the collapse of the proto-planetary Nebula, subject to the very general assumption that DM particles have an individual mass << than the mass of the Earth. This process, much more efficient than the previously considered post-formation captures by three-body interactions (1, 2), would apply to both microscopic DM, such as axions or Weakly Interacting Massive Particles (WIMPs), and macroscopic DM candidates such as Compact Ultra-Dense Objects (CUDOs) and Primordial Black Holes (PBH). "Primordial capture" occurs from the gravitational potential changes during the collapse of the proto-planetary nebula. Planetary systems result from the gravitational collapse of cold molecular clouds as the gas becomes gravitationally unstable, collapses, and fragments, with stellar systems forming out of the condensed fragments. Although free ranging DM particles would be minimally influenced by gas pressure changes directly, they of course would

2010, Classical and Quantum Gravity

This review addresses the issue of whether there are physically realistic self-similar solutions in which a primordial black hole is attached to an exact or asymptotically Friedmann model for an equation of state of the form p = (γ − 1)ρc 2 . In the positive pressure case (1 < γ < 2), there is no such solution when the black hole is attached to an exact Friedmann background via a sonic point. However, it has been claimed that there is a one-parameter family of asymptotically Friedmann black hole solutions providing the ratio of the black hole size to the cosmological horizon size is in a narrow range above some critical value. There are also "universal" black holes in which the black hole has an apparent horizon but no event horizon. It turns out that both these types of solution are only asymptotically quasi-Friedmann, because they contain a solid angle deficit at large distances, but they are not necessarily excluded observationally. Such solutions may also exist in the 2/3 ≤ γ <≤ 1 case, although this has not been demonstrated explicitly. In the stiff case (γ = 2), there is no self-similar solution in an exact background unless the matter turns into null dust before entering the event horizon, which is a contrived and probably unphysical situation. However, there may be asymptotically quasi-Friedmann solutions without a sonic point which contain universal black holes. In the negative pressure case (0 < γ < 2/3), corresponding to a dark-energy-dominated universe, there is a one-parameter family of black hole solutions which are properly asymptotically Friedmann (in the sense that there is no angle deficit) and such solutions may arise naturally in the inflationary scenario. The ratio of the black hole size to the cosmological horizon size must now be below some critical value, so the range is more extended than in the positive pressure case and one needs less fine-tuning. If one tries to make a black hole which is larger than this, one finds a self-similar solution which connects two asymptotic regions, one being exactly Friedmann and the other asymptotically quasi-Friedmann. This might be regarded as a cosmological wormhole solution providing one defines a wormhole throat quasi-locally in terms of a non-vanishing minimal area on a spacelike hypersurface. The possibility of self-similar black holes in phantom fluids (γ < 0), where the black hole shrinks as the big rip singularity is approached, or tachyonic fluids (γ > 2) remains unclear. We also consider the possibility of self-similar black hole solutions in a universe dominated by a scalar field. If the field is massless, the situation resembles the stiff fluid case, so any black hole solution is again contrived, although there may still be universal black hole solutions. The situation is less clear if the scalar field is rolling down a potential and therefore massive, as in the quintessence scenario. Although no explicit asymptotically Friedmann black hole solutions of this kind are known, they are not excluded and comparison with the 0 < γ < 2/3 perfect fluid case suggests that they should exist if the black hole is not too large. This implies that a black hole might grow as fast as the cosmological horizon in a quintessence-dominated universe in some circumstances, supporting the proposal that accretion onto primordial black holes may have played a role in the production of the supermassive black holes in galactic nuclei.

2011, Modern Physics Letters A

Some quantum-cosmic scaling relations indicate that the MOND acceleration parameter a0 could be a fundamental quantity ruling the self-gravitating structures, ranging from stars and globular clusters up to superclusters of galaxies and the whole observed universe. We discuss such coincidence relations starting from the Dirac quantization condition ruling the masses of primordial black holes.

2006, … of Cosmology and …

Stephen Hawking's prediction that black holes should radiate like black bodies has several important consequences, including the possibility of the detection of small (∼10 15 g) black holes created in the very early universe. The detection of such primordial black holes (PBHs) would be an important discovery, not only confirming Hawking's theory, but also providing valuable insights into the history of the early universe. A search through 5.5 years of archival data from the Whipple Atmospheric Cerenkov Telescope is made for TeV gamma-ray bursts on 1, 3, and 5 s timescales. On the basis of a null result from this direct search for PBH evaporations, an upper limit of 1.08 × 10 6 pc −3 yr −1 (99% CL) is set on the PBH evaporation rate in the local region of the galaxy, assuming the Standard Model of particle physics. This is more than a factor of two better than the previous limit at this energy range and includes longer timescales than have previously been explored. Comparison of this result with previous limits on the fraction of the critical density comprised by PBHs, Ω pbh , depends strongly on assumptions made about PBH clustering; in models predicting strong PBH clustering, the limit in this work could be as many as ten orders of magnitude more stringently than those set by diffuse MeV gamma-ray observations.

1999

Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch ∼ 10 −33 sec to ∼ 5 × 10 −9 sec. In this paper we use Barrow et al's ansatz to model blackhole evaporation in which the modified Hawking temperature goes to zero in the limit of the blackhole attaining a relic state with mass ∼ m pl. Both single mass PBH case as well as the case in which blackhole masses are distributed in the range 8 × 10 2-3 × 10 5 gm have been considered in our analysis. Blackholes with mass larger than ∼ 10 5 gm appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X −X emissions, averting the baryon number wash-out due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass m is given by ∼ ǫζ(m/1 gm) −1 , where ǫ and ζ are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For ǫ larger than ∼ 10 −4 , the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs.

2010

Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye.

2011, Modern Physics Letters A

2007, Physics Letters B

We show that if photon possesses a tiny but non-vanishing mass the universe cannot be electrically neutral. Cosmological electric asymmetry could be generated either at an early stage by different evaporation rates of primordial black holes with respect to positively and negatively charged particles or by predominant capture of protons in comparison to electrons by heavy galactic black holes in contemporary universe. An impact of this phenomenon on the generation of large scale magnetic fields and on the universe acceleration is considered.

2009, ACM Transactions on Reconfigurable Technology and Systems

Array-based, direct-sampling radio telescopes have computational and communication requirements unsuited to conventional computer and cluster architectures. Synchronization must be strictly maintained across a large number of parallel data streams, from A/D conversion, through operations such as beamforming, to dataset recording. FPGAs supporting multigigabit serial I/O are ideally suited to this application. We describe a recently-constructed radio telescope called ETA having all-sky observing capability for detecting low frequency pulses from transient events such as gamma ray bursts and primordial black hole explosions. Signals from 24 dipole antennas are processed by a tiered arrangement of 28 commercial FPGA boards and 4 PCs with FPGAbased data acquisition cards, connected with custom I/O adapter boards supporting InfiniBand and LVDS physical links. ETA is designed for unattended operation, allowing configuration and recording to be controlled remotely.

2010, Acta Astronautica

Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye.

1999, Physics Letters B

General relativistic effects in the form of metric perturbations are usually neglected in the preheating era that follows inflation. We argue that in realistic multi-field models these effects are in fact crucial, and the fully coupled system of metric and quantum field fluctuations needs to be considered. Metric perturbations are resonantly amplified, breaking the scale-invariance of the primordial spectrum, and in turn stimulate scalar field resonances via gravitational rescattering. This non-gravitationally dominated nonlinear growth of gravitational fluctuations may have significant effects on the Doppler peaks in the cosmic background radiation, primordial black hole formation, gravitational waves and nonthermal symmetry restoration.

1993, Physical Review D

The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f , the fraction of cosmic string loops which collapse to form black holes, and µ, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction on the parameters f and µ is due to the energy density in 100M eV photons radiated by the black holes. We also find that inert black hole remnants cannot serve as the dark matter. If earlier, crude estimates of f are reliable, our results severely restrict µ, and therefore limit the viability of the cosmic string large-scale structure scenario.

1997, Physical Review D

We explore the role of non-Gaussian fluctuations in primordial black hole (PBH) formation and show that the standard Gaussian assumption, used in all PBH formation papers to date, is not justified. Since large spikes in power are usually associated with flat regions of the inflaton potential, quantum fluctuations become more important in the field dynamics, leading to mode-mode coupling and non-Gaussian statistics. Moreover, PBH production requires several sigma (rare) fluctuations in order to prevent premature matter dominance of the universe, so we are necessarily concerned with distribution tails, where any intrinsic skewness will be especially important. We quantify this argument by using the stochastic slow-roll equation and a relatively simple analytic method to obtain the final distribution of fluctuations. We work out several examples with toy models that produce PBH's, and test the results with numerical simulations. Our examples show that the naive Gaussian assumption can result in errors of many orders of magnitude. For models with spikes in power, our calculations give sharp cut-offs in the probability of large positive fluctuations, meaning that Gaussian distributions would vastly over-produce PBH's. The standard results that link inflationproduced power spectra and PBH number densities must then be reconsidered, since they rely quite heavily on the Gaussian assumption. We point out that since the probability distributions depend strongly on the nature of the potential, it is impossible to obtain results for general models. However, calculating the distribution of fluctuations for any specific model seems to be relatively straightforward, at least in the single inflaton case.

2006, Journal of Cosmology and Astroparticle Physics

The mass spectrum of the primordial black holes formed by density perturbation in the radiationdominated era of the Randall-Sundrum type-2 cosmology is given. The spectrum coincides with standard four-dimensional one on large scales but the deviation is apparent on smaller scales. The mass spectrum is initially softer than standard four-dimensional one, while after accretion during the earliest era it becomes harder than that. We also show expected extragalactic diffuse photon background spectra varying the initial perturbation power-law power spectrum and give constraints on the blue spectra and/or the reheating temperature. The most recent observations on the small scale density perturbation from WMAP, SDSS and Lyman-α Forest are used. What we get are interpreted as constraints on the smaller-scale inflation on the brane connected to the larger one at the scale of Lyman-α Forest. If we set the bulk curvature radius to be 0.1 mm and assume the reheating temperature is higher than 10 6 GeV, the scalar spectral index from the smaller scale inflation is constrained to be n 1.3. Typically, the constraints are tighter than the standard four-dimensional one, which is also revised by us using the most recent observations.

2005, Physical Review D

We use data from the second science run of the LIGO gravitational-wave detectors to search for the gravitational waves from primordial black hole (PBH) binary coalescence with component masses in the range 0.2--$1.0 M_\odot$. The analysis requires a signal to be found in the data from both LIGO observatories, according to a set of coincidence criteria. No inspiral signals were found. Assuming a spherical halo with core radius 5 kpc extending to 50 kpc containing non-spinning black holes with masses in the range 0.2--$1.0 M_\odot$, we place an observational upper limit on the rate of PBH coalescence of 63 per year per Milky Way halo (MWH) with 90% confidence.

2008

Model of supermassive black holes formation inside the clusters of primordial black holes is developed. Namely, it is supposed, that some mass fraction of the universe ~10^-3 is composed of the compact clusters of primordial (relic) black holes, produced during phase transitions in the early universe. These clusters are the centers of dark matter condensation. We model the formation of protogalaxies with masses about 2*10^8M_sun at the redshift z=15. These induced protogalaxies contain central black holes with mass ~10^5M_sun and look like dwarf spheroidal galaxies with central density spike. The subsequent merging of induced protogalaxies and ordinary dark matter haloes corresponds to the standard hierarchical clustering scenario of large-scale structure formation. The coalescence of primordial black holes results in formation of supermassive black holes in the galactic centers. As a result, the observed correlation between the masses of central black holes and velocity dispersion in the galactic bulges is reproduced.

2004

We describe the model of protogalaxy formation around the cluster of primordial black holes with a minimum extension of standard cosmological model. Namely, it is supposed, that a mass fraction of the universe ~10^-3 is composed of the compact clusters of primordial (relict) black holes produced during the phase transitions in the early universe. These clusters are the centers of the dark matter (DM) condensations. As a result the protogalaxies with a mass 2x10^8Msun form at the redshift z=15. These induced protogalaxies contain the central black holes of mass ~10^5Msun and look like the dwarf spheroidal galaxies with a central density spike. Subsequent merging of the induced protogalaxies and ordinary DM haloes leads to the standard scenario of the large scale structure formation. Black holes merging gives the nowadays supermassive black holes and reproduces the observed correlations between their masses and velocity dispersions in the bulges.

2005, Physical Review D

We provide a simple but robust argument that primordial black hole (PBH) production generically does not exceed astrophysical bounds during the resonant preheating phase after inflation. This conclusion is supported by fully nonlinear lattice simulations of various models in two and three dimensions which include rescattering but neglect metric perturbations. We examine the degree to which preheating amplifies density perturbations at the Hubble scale and show that at the end of the parametric resonance, power spectra are universal, with no memory of the power spectrum at the end of inflation. In addition we show how the probability distribution of density perturbations changes from exponential on very small scales to Gaussian when smoothed over the Hubble scale -the crucial length for studies of primordial black hole formation -hence justifying the standard assumption of Gaussianity.

2009

In this small review we present the actual state the knowledge about weighting black holes. Black holes can be found in stellar binary systems in our Galaxy and in other nearby galaxies, in globular clusters, which we can see in our and nearby galaxies, and in centres of all well-developed galaxies. Range of values of their masses is wide and cover about ten orders of magnitude (not taking into account the hypothetic primordial black holes). Establishing the presence of black holes, and in particular the measurement of their mass is one on the key issues for many branches of astronomy, from stellar evolution to cosmology.

2002, Physical Review D

In cosmological models with a varying gravitational constant, it is not clear whether primordial black holes preserve the value of G at their formation epoch. We investigate this question by using the Tolman-Bondi model to study the evolution of a background scalar field when a black hole forms from the collapse of dust in a flat Friedmann universe. Providing the back reaction of the scalar field on the metric can be neglected, we find that the value of the scalar field at the event horizon very quickly assumes the background cosmological value. This suggests that there is very little gravitational memory.

2006, Journal of Cosmology and Astroparticle Physics

2003, Physical Review D

A cosmological model in which primordial black holes (PBHs) are present in the cosmic fluid at some instant t = t 0 is investigated. The time t 0 is naturally identified with the end of the inflationary period. The PBHs are assumed to be nonrelativistic in the comoving fluid, to have the same mass, and may be subject to evaporation for t > t 0 . Our present work is related to an earlier paper of Zimdahl and Pavón [Phys. Rev. D 58, 103506 (1998)], but in contradistinction to these authors we assume that the (negative) production rate of the PBHs is zero. This assumption appears to us to be more simple and more physical. Consequences of the formalism are worked out. In particular, the four-divergence of the entropy four-vector in combination with the second law in thermodynamics show in a clear way how the the case of PBH evaporation corresponds to a production of entropy. Accretion of radiation onto the black holes is neglected. We consider both a model where two different sub-fluids interact, and a model involving one single fluid only. In the latter case an effective bulk viscosity naturally appears in the formalism.

2003, Journal of High Energy Physics

We consider astrophysics of large black holes localized on the brane in the infinite Randall-Sundrum model. Using their description in terms of a conformal field theory (CFT) coupled to gravity, deduced in Ref.

2005, Physical Review D

We investigate cosmic-ray antiprotons emitted from the galactic primordial black holes in the Randall-Sundrum type-2 braneworld. The recent results of the BESS antiproton observation implies the existence of exotic primary sub-GeV antiprotons, one of whose most probable origin is PBHs in Our Galaxy. We show that the magnitude of antiproton flux from PBHs in the RS braneworld is proportional to negative power of the AdS radius, and immediately find that a large extra-dimension can relax upper-limits on the abundance of the galactic PBHs. If actually there are more PBHs than the known upper-limit obtained in the pure 4D case, they set a lower bound on the size of the extra dimension above at least 10 20 times 4D Planck-length to avoid inconsistency. On completion of the numerical studies, we show that these constraints on the AdS radius is comparable to those obtained from the diffuse photon background by some of the authors in the previous paper. Moreover, in the low accretion-rate case, only antiprotons can constrain the braneworld. We show that we will detect signatures of the braneworld as a difference between the flux of the antiprotons predicted in 4D and 5D by future observations in sub-GeV region with a few percent precision.

1997

We review recent progress in the study of varying constants and attempts to explain the observed values of the fundamental physical constants. We describe the variation of GGG in Newtonian and relativistic scalar-tensor gravity theories. We highlight the behaviour of the isotropic Friedmann solutions and consider some striking features of primordial black hole formation and evaporation if GGG varies. We discuss attempts to explain the values of the constants and show how we can incorporate the simultaneou s variations of several 'constants' exactly by using higher-dimensional unified theories. Finally, we describe some new observational limits on possible space or time variations of the fine structure constant.

2004

We propose the model of first quasars formation around the cluster of primordial black holes (PBHs). It is supposed, that mass fraction of the universe ∼ 10 −3 is composed of the compact clusters of PBHs, produced during the phase transitions in the early universe. The clusters of PBHs become the centers of dark matter condensation. As a result, the galaxies with massive central black holes are formed. In the process of galaxies formation the central black holes are growing due to accretion. This accretion is acompaned by the early quasar activity.

1999, Physical Review D

Incorporating a realistic model for accretion of ultra-relativistic particles by primordial blackholes (PBHs), we study the evolution of an Einstein-de Sitter universe consisting of PBHs embedded in a thermal bath from the epoch sim10−33\sim 10^{-33}sim10−33 sec to sim5times10−9\sim 5\times 10^{-9}sim5times10−9 sec. In this paper we use Barrow et al's ansatz to model blackhole evaporation in which the modified Hawking temperature goes to zero in the limit of the blackhole attaining a relic state with mass simmpl\sim m_{pl}simmpl. Both single mass PBH case as well as the case in which blackhole masses are distributed in the range 8times102−3times1058\times 10^2 - 3\times 10^58times102−3times105 gm have been considered in our analysis. Blackholes with mass larger than sim105\sim 10^5sim105 gm appear to survive beyond the electroweak phase transition and, therefore, successfully manage to create baryon excess via X−barXX-\bar XX−barX emissions, averting the baryon number wash-out due to sphalerons. In this scenario, we find that the contribution to the baryon-to-entropy ratio by PBHs of initial mass mmm is given by simepsilonzeta(m/1gm)−1\sim \epsilon \zeta (m/1 {gm})^{-1}simepsilonzeta(m/1gm)−1, where epsilon\epsilonepsilon and zeta\zetazeta are the CP-violating parameter and the initial mass fraction of the PBHs, respectively. For epsilon\epsilon epsilon larger than sim10−4\sim 10^{-4}sim10−4, the observed matter-antimatter asymmetry in the universe can be attributed to the evaporation of PBHs.

2002, Physical Review D

We investigate spherically symmetric self-similar solutions in Brans-Dicke theory. Assuming a perfect fluid with the equation of state p = (γ − 1)µ (1 ≤ γ < 2), we show that there are no nontrivial solutions which approach asymptotically to the flat Friedmann-Robertson-Walker spacetime if the energy density is positive. This result suggests that primordial black holes in Brans-Dicke theory cannot grow at the same rate as the size of the cosmological particle horizon.

2011

We study the possibility of reheating the universe through the evaporation of primordial black holes created at the end of inflation. This is shown to allow for the unification of inflation with dark matter or dark energy, or both, under the dynamics of a single scalar field. We determine the necessary conditions to recover the standard big bang by the time of nucleosynthesis after reheating through black holes.

1999, Astronomy & Astrophysics

The capture of cold dark matter species, and especially primordial black holes, during the formation of gravitationally bound objects is analyzed. It is shown that the best conditions for an efficient gravitational capture were at the epoch preceding the galaxy formation, when the first astrophysical objects with masses of the order of Jeans mass 10(5-10^6 Msun) were forming. Black hole

1998, Physics Letters B

Recently, a new framework for solving the hierarchy problem was proposed which does not rely on low energy supersymmetry or technicolor. The fundamental Planck mass is at a TeV and the observed weakness of gravity at long distances is due the existence of new sub-millimeter spatial dimensions. In this letter, we study how the properties of black holes are altered in these theories. Small black holes-with Schwarzschild radii smaller than the size of the new spatial Ž . dimensions-are quite different. They are bigger, colder, and longer-lived than a usual 3 q 1 -dimensional black hole of the same mass. Furthermore, they primarily decay into harmless bulk graviton modes rather than standard-model degrees of freedom. We discuss the interplay of our scenario with the holographic principle. Our results also have implications for the Ž . bounds on the spectrum of primordial black holes PBHs derived from the photo-dissociation of primordial nucleosynthesis products, distortion of the diffuse gamma-ray spectrum, overclosure of the universe, gravitational lensing, as well as the phenomenology of black hole production. For example, the bound on the spectral index of the primordial spectrum of density perturbations is relaxed from 1.25 to 1.45-1.60 depending on the epoch of the PBH formation. In these scenarios PBHs provide interesting dark matter candidates; for 6 extra dimensions MACHO candidates with mass ; 0.1 M can arise. ( For 2 or 3 extra dimensions PBHs with mass ; 10 4 M can occur and may act as both dark matter and seeds for early ( galaxy and QSO formation. q 1998 Published by Elsevier Science B.V. All rights reserved. ) mensional theory M , p l M 2 ; R n M nq 2 , 1 Ž . p l )

2006

2010

Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye.

2011, Modern Physics Letters A

Starting from a quantization relation for primordial black holes, it is shown that quantum fluctuations can play a fundamental role in determining the effective scales of self-gravitating astrophysical systems. Furthermore the Eddington-Weinberg relation between the current scale of the observed universe to the Planck constant (the natural action unit) is naturally derived. Finally, such an approach allows to recover the current value of the cosmological constant.

2011, Modern Physics Letters A

In this work, we study the evolution of Primordial Black Holes within the context of Loop Quantum Gravity. 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 gravity even though a larger number of primordial black holes may form in early universe in comparison with Einstein's or scalar-tensor theories.

2008, Physical Review D

We report on a search for gravitational waves from the coalescence of compact binaries during the third and fourth LIGO science runs. The search focused on gravitational waves generated during the inspiral phase of the binary evolution. In our analysis, we considered three categories of compact binary systems, ordered by mass: (i) primordial black hole binaries with masses in the range 0.35M⊙ < m1, m2 < 1.0M⊙, (ii) binary

2003, Astronomical & Astrophysical Transactions

We argue that the observed correlations between central black-hole masses M BH and Galactic bulge velocity dispersions σe in the form M BH ∝ σ4 c may witness the pre-Galactic origin of massive black holes. Primordial black holes would be the centres for growing protogalaxies which experienced multiple mergers with ordinary galaxies. This process is accompanied by the merging of black holes in the galactic nuclei.

2008, Physical Review D

2003, Astronomy & Astrophysics

In most cosmological models, primordial black holes (PBHs) should have formed in the early Universe. Their Hawking evaporation into particles could eventually lead to the formation of antideuterium nuclei. This paper is devoted to a first computation of this antideuteron flux. The production of these antinuclei is studied with a simple coalescence scheme, and their propagation in the Galaxy is treated with a well-constrained diffusion model. We compare the resulting primary flux to the secondary background, due to the spallation of protons on the interstellar matter. Antideuterons are shown to be a very sensitive probe for primordial black holes in our Galaxy. The next generation of experiments should allow investigators to significantly improve the current upper limit, nor even provide the first evidence of the existence of evaporating black holes.