共查询到20条相似文献，搜索用时 15 毫秒
1.
Aurlien Barrau 《Astroparticle Physics》2000,12(4):495
The origin of observed extremely high energy cosmic rays remains an astrophysical enigma. We show that a single evaporating primordial black hole should produce 8.5·1014 particles over a 1020 eV threshold. This emission results from direct production of fundamental constituents and from hadronization of quarks and gluons. The induced flux on the Earth is studied as a function of the local density of exploding black holes and compared with experimental data. The discovery potential of future detectors is finally reviewed. 相似文献
2.
Vilkovisky has claimed to have solved the black hole backreaction problem and finds that black holes lose only ten percent
of their mass to Hawking radiation before evaporation ceases. We examine the implications of this scenario for cold dark matter,
assuming that primordial black holes are created during the reheating period after inflation. The mass spectrum is expected
to be dominated by 10-gram black holes. Nucleosynthesis constraints and the requirement that the earth presently exist do
not come close to ruling out such black holes as dark matter candidates. They also evade the demand that the photon density
produced by evaporating primordial black holes does not exceed the present cosmic radiation background by a factor of about
one thousand. 相似文献
3.
D. Dwivedee B. Nayak M. Jamil L. P. Singh R. Myrzakulov 《Journal of Astrophysics and Astronomy》2014,35(1):97-106
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. 相似文献
4.
The possibility of identifying some of Galactic gamma-ray sources as clusters of primordial black holes is discussed. The known scenarios of supermassive black hole formation indicate the multiple formation of lower-mass black holes. Our analysis demonstrates that due to Hawking evaporation the cluster of black holes with masses about 1015 g could be observed as a gamma-ray source. The total mass of typical cluster is ∼10 M⊙. Detailed calculations have been performed on the basis of specific model of primordial black hole formation. 相似文献
5.
We consider a cosmological model in which part of the Universe, Ωh～10?5, is in the form of primordial black holes with masses of ～ 105 M ⊙. These primordial black holes were the centers for growing protogalaxies, which experienced multiple mergers with ordinary galaxies and with each other. The galaxy formation is accompanied by the merging and growth of central black holes in the galactic nuclei. We show that the recently discovered correlations between central black hole masses and galactic bulge parameters naturally arise in this scenario. 相似文献
6.
David B. Cline 《Astrophysics and Space Science》1995,231(1-2):393-397
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. 相似文献
7.
Yu. N. Eroshenko 《Astronomy Letters》2016,42(6):347-356
We show that density spikes begin to form from dark matter particles around primordial black holes immediately after their formation at the radiation-dominated cosmological stage. This stems from the fact that in the thermal velocity distribution of particles there are particles with low velocities that remain in finite orbits around black holes and are not involved in the cosmological expansion. The accumulation of such particles near black holes gives rise to density spikes. These spikes are considerably denser than those that are formed later by the mechanism of secondary accretion. The density spikes must be bright gamma-ray sources. Comparison of the calculated signal from particle annihilation with the Fermi-LAT data constrains the present-day cosmological density parameter for primordial black holes with masses M BH ≥ 10?8 M ⊙ from above by values from ΩBH ≤ 1 to ΩBH ≤ 10?8, depending on MBH. These constraints are several orders of magnitude more stringent than other known constraints. 相似文献
8.
The rate of gravitational wave bursts from the mergers of massive primordial black holes in clusters is calculated. Such clusters of black holes can be formed through phase transitions in the early Universe. The central black holes in clusters can serve as the embryos of supermassive black holes in galactic nuclei. The expected burst detection rate by the LISA gravitational wave detector is estimated. 相似文献
9.
Black holes are extremely dense and compact objects from which light cannot escape. There is an overall consensus that black holes exist and many astronomical objects are identified with black holes. White holes were understood as the exact time reversal of black holes, therefore they should continuously throw away material. It is accepted, however, that a persistent ejection of mass leads to gravitational pressure, the formation of a black hole and thus to the “death of while holes”. So far, no astronomical source has been successfully tagged a white hole. The only known white hole is the Big Bang which was instantaneous rather than continuous or long-lasting. We thus suggest that the emergence of a white hole, which we name a ‘Small Bang’, is spontaneous - all the matter is ejected at a single pulse. Thus, unlike black holes, white holes cannot be continuously observed rather their effect can only be detected around the event itself. γ-ray bursts are the most energetic explosions in the universe. Long γ-ray bursts were connected with supernova eruptions. There is a new group of γ-ray bursts, which are relatively close to Earth, but surprisingly lack any supernova emission. We propose identifying these bursts with white holes. White holes seem like the best explanation of γ-ray bursts that appear in voids. We also predict the detection of rare gigantic γ-ray bursts with energies much higher than typically observed. 相似文献
10.
The characteristics of gravitational bursts from active galactic nuclei, and globular clusters are obtained for three astrophysical situations:(i) scattering of stars by massive black holes residued at the centers of galaxies and globular clusters; (ii) the close encounters of stars in the nuclear regions of these objects; (iii) scattering of stars by black holes of stellar mass containing in the stellar population of galactic nuclei and clusters. The most effective source of gravitational bursts appears to be a scattering of stars by the massive central black holes which produces the bursts with dimensionless amplitudeh10–19–10–21 and frequencies from 10–1 to 10–5 Hz. The characteristics obtained correspond to the possiblities of a future gravitational-wave experiment with use of laser Doppler tracking of interplanetary spacecrafts. 相似文献
11.
We discuss a very peculiar subgroup of gamma-ray bursts among the BATSE sources. These bursts are very short (T90 ? 0.1 s), hard, and came predominantly from a restricted direction of the sky (close to the Galactic anti-center). We analyze their arrival times and possible correlations, as well as the profiles of individual bursts. We find no peculiarities in the arrival times of Very Short Bursts (VSBs) despite their highly non-uniform spatial distribution. There is no dependence in the burst shapes on location. Bursts coming both from the burst-enhancement Galactic Anticenter region and from all other directions show considerable dispersion in their rise and fall times. Significant fraction of VSBs have multiple peaks despite their extremely short duration. Burst time properties are most likely to be consistent with two origin mechanisms: either with binary NS–NS mergers with low total masses passing through a phase of hypermassive neutron star, or with evaporation of the primordial black holes in the scenario of no photosphere formation. 相似文献
12.
V. K. Oikonomou 《Astrophysics and Space Science》2014,352(2):925-935
In this paper we consider the implications that the effect gravitational memory would have on primordial black holes, within the theoretical context of F(R) related scalar-tensor theories. As we will demonstrate, under the assumption that the initial mass of the primordial black hole is such so that it evaporates today, this can potentially constrain the F(R) related theories of gravity. We study two scalar-tensor models and discuss the evolution of primordial black holes created at some initial time t f in the early universe. The results between the two models vary significantly which shows us that, if the effect of gravitational memory is considered valid, some of the scalar-tensor models and their corresponding F(R) theories must be further constrained. 相似文献
13.
V. I. Dokuchaev Yu. N. Eroshenko S. G. Rubin D. A. Samarchenko 《Astronomy Letters》2010,36(11):773-779
A model for the formation of supermassive primordial black holes in galactic nuclei with the simultaneous suppression of the
formation of intermediate-mass black holes is presented. A bimodal mass function for black holes formed through phase transitions
in a model with a “Mexican hat” potential has been found. The classical motion of the phase of a complex scalar field during
inflation has been taken into account. Possible observational manifestations of primordial black holes in galaxies and constraints
on their number are discussed. 相似文献
14.
在精确宇宙学的时代, 多信使、高精度、小尺度的宇宙学观测在帮助人们从更加深刻的层面理解宇宙极早期的同时, 也给基于线性近似和微扰展开宇宙学扰动理论带来了新的挑战. 近年来, 对原初引力波和原初黑洞的搜寻使得研究人员们对早期宇宙在小尺度上的非线性非微扰过程产生了浓厚的研究兴趣. 综述了在宇宙学小尺度上关于原初黑洞产生以及引力波研究取得的诸多进展, 重点关注了使用Mathieu方程的共振效应来研究小尺度功率谱放大以及诱导产生可观测的原初引力波的方法. 此外, 还尝试探讨了非高斯尾巴对原初黑洞形成的影响. 发现Mathieu方程所具备的共振效应可以提供一种有效的方法来刻画原初宇宙中小尺度的非微扰动力学过程, 从而能够更好地理解原初黑洞的形成以及相关的引力波产生机制. 同时, 非微扰的非高斯性在原初黑洞形成中可能会产生不可忽视的影响. 相似文献
15.
Pavel Voráček 《Astrophysics and Space Science》1981,74(2):497-499
In this paper two examples are given, showing that the existence of black holes in the Universe violates, in its consequences, the principle of causality. The solution presented is based on the idea that the primordial black holes have zero-mass-energy and consequently zero-radius of the event horizon. Despite the existence of the surface of last influence, gravitational collapse does not produce black holes during a finite time interval as measured by an external observer. The only singularity, possible to accept (if any), is the initial and final cosmological singularity. 相似文献
16.
Just forty years ago, Hawking wrote his famous paper on primordial black holes (PBH). There have been since innumerable discussions on the consequences of the existence of such exotic objects and ramifications of their properties. Here we suggest that PBH’s in an ever expanding universe (as implied by dark energy domination, especially of a cosmological constant) could be the ultimate repository for long lived living systems. PBH’s having solar surface temperatures would last 1032 years as a steady power source and should be considered in any discussion on exobiological life. 相似文献
17.
J. Lazio 《Astronomische Nachrichten》2008,329(3):330-333
Known classes of radio wavelength transients range from the nearby stellar flares and radio pulsars to the distant Universe γ‐ray burst afterglows. Hypothesized classes of radio transients include analogs of known objects, e.g., extrasolar planets emitting Jovian‐like radio bursts and giant‐pulse emitting pulsars in other galaxies, to the exotic, prompt emission from γ‐ray bursts, evaporating black holes, and transmitters from other civilizations. A number of instruments and facilities are either under construction or in early observational stages and are slated to become available in the next few years. With a combination of wide fields of view and wavelength agility, the detection and study of radio transients will improve immensely. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
18.
Merging rates for compact binaries (double neutron stars or black holes) are calculated based on modern concepts of binary star evolution. It is found that the first laser interferometers, with rms sensitivities of 10-21 at a frequency of 100 Hz, can detect 10-700 black holes and only 1 neutron star coalescences in a 1-year integration time. The implications of evolutionary effects for the cosmological origin of gamma ray bursts are also discussed. 相似文献
19.
S. O. Alexeyev A. Barrow G. Bowdole M. V. Sazhin O. S. Khovanskaya 《Astronomy Letters》2002,28(7):428-433
We present a simple model for the evaporation of primordial black holes at final stages with the formation of a relic remnant with a mass of 1–103 m P1. The model takes into account the conservation of energy and the impossibility of passing through the state with the minimum possible mass. These relic remnants may account for a substantial fraction of dark matter in the Universe. 相似文献
20.
Almost all galaxies have massive central black holes in their centers with masses typically ranging from ～105 to ～109 M⊙. However, the origin and evolution of these objects and their connection with the hosting galaxies are not completely understood yet. In this work we analyze the mass accretion rate of supermassive black holes (SMBH’s) and the mean Eddington ratio (MER) of type 1 AGN using data from the Sloan Sky Survey. For this purpose we improve the method for constructing the subsample of SMBH, taking into account the survey flux limit and the bias of the sample. It was observed that the mean bolometric luminosity of the active black holes can be represented by a function composed by a power law in mass and a like-Schechter function in redshift. Our results also show that both the mean Eddington ratio and the mass accretion rate are proportional to this function. 相似文献