共查询到20条相似文献，搜索用时 31 毫秒
1.
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
2.
Toshihiro Kawaguchi Masahiro Kawasaki Tsutomu Takayama Masahide Yamaguchi Jun'ichi Yokoyama 《Monthly notices of the Royal Astronomical Society》2008,388(3):1426-1432
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. 相似文献
3.
Kourosh Nozari 《Astrophysics and Space Science》2012,341(2):421-427
We study the relation between the existence of the logarithmic prefactor and spacetime dimensionality in black hole entropy relation by a detailed study of a TeV-scale black hole entropy. In a model universe with large extra dimensions and within the Generalized Uncertainty Principle (GUP) framework, we show that probability of black hole production in the Large Hadronic Collider (LHC) decreases for sufficiently large values of the GUP parameter. In this regard, even observation of micro-black holes may be suppressed at TeV energy scale. We determine also the GUP parameter in an extra dimensional scenario by comparing black hole entropy calculated within the GUP and loop quantum gravity frameworks. 相似文献
4.
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
5.
We study a black hole in an expanding Universe during the radiation-dominated stage. In particular, such a black hole may be of the primordial origin. In the case when the black hole radius is much smaller than the cosmological horizon, we found a self-consistent solution for the metric and the matter distribution and its velocity far from the black hole. At distances much smaller than the cosmological horizon our solution coincides with the previously obtained solution for quasi-stationary accretion. Our results can be applied, in particular, for the formation of dark matter density spikes around primordial black holes, and for the evolution of dark matter clumps during the radiation-dominated stage. 相似文献
6.
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
7.
V. B. Petkov E. V. Bugaev P. A. Klimai M. V. Andreev V. I. Volchenko G. V. Volchenko A. N. Gaponenko Zh. Sh. Guliev I. M. Dzaparova D. V. Smirnov A. V. Sergeev A. B. Chernyaev A. F. Yanin 《Astronomy Letters》2008,34(8):509-514
Temporal and energy characteristics of the very-high-energy gamma-ray bursts from evaporating primordial black holes have been calculated by assuming that the photospheric and chromospheric effects are negligible. The technique of searching for such bursts on shower arrays is described. We show that the burst time profile and the array dead time should be taken into account to interpret experimental data. Based on data from the Andyrchy array of the Baksan Neutrino Observatory (Institute for Nuclear Research, Russian Academy of Sciences), we have obtained an upper limit on the number density of evaporating primordial black holes in a local region of space with a scale size of ～10?3 pc. Comparison with the results of previous experiments is made. 相似文献
8.
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
9.
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
10.
11.
We consider the possibility of low-mass primordial black holes being formed in terms of the inflationary theory of the early Universe. We found a condition on the reheating temperature under which the relic remnants of primordial black holes had been formed by now. These relic remnants may account for a part of the dark matter in our Universe. 相似文献
12.
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
13.
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
14.
A Bianchi type-I cosmological model in the presence of a magnetic flux along a cosmological string is considered. The first
objective of this study is to investigate Einstein equations using a tractable assumption usually accepted in the literature.
Quantum effects of the present cosmological model are examined in the framework of loop quantum cosmology. Finally we draw
a parallel between the classical and quantum approaches. 相似文献
15.
Using simple path integral, Feynman propagator method and the relation between conformal timeη and scale factor Τ, we investigate the non-conformal quantum fluctuations (of expansion and shear) and axisymmetric singularity
case in radiation dominated anisotropic cosmology. We show that near the classical singularity the quantum fluctuations tend
to diverge.
Since the December 1998 issue of this journal was delayed, we were able to include this paper in this issue. 相似文献
16.
The maximal entropy and the final parameters of the expansive-creative evolution phase of the ultrastable Universe can be determined from model properties of the expansive nondecelerative Universe.The possibility of existence of primordial black holes with temperature of the Universe follows from the initial entropy of the Universe. This fact throws new light on the problem of dark matter. 相似文献
17.
In this study, we explore a particular type Hawking radiation which ends with zero temperature and entropy. The appropriate black holes for this purpose are the linear dilaton black holes. In addition to the black hole choice, a recent formalism in which the Parikh-Wilczek’s tunneling formalism amalgamated with quantum corrections to all orders in ? is considered. The adjustment of the coefficients of the quantum corrections plays a crucial role on this particular Hawking radiation. The obtained tunneling rate indicates that the radiation is not pure thermal anymore, and hence correlations of outgoing quanta are capable of carrying away information encoded within them. Finally, we show in detail that when the linear dilaton black hole completely evaporates through such a particular radiation, entropy of the radiation becomes identical with the entropy of the black hole, which corresponds to “no information loss”. 相似文献
18.
In recent years, the thermodynamic properties of black holes are topics of interests. We investigate the thermodynamic properties like surface gravity and Hawking temperature on event horizon of regular black holes viz. Hayward Class and asymptotically AdS (Anti-de Sitter) black holes. We also analyze the thermodynamic volume and naive geometric volume of asymptotically AdS black holes and show that the entropy of these black holes is simply the ratio of the naive geometric volume to thermodynamic volume. We plot the different graphs and interpret them physically. We derive the ‘cosmic-Censorship-Inequality’ for both type of black holes. Moreover, we calculate the thermal heat capacity of aforesaid black holes and study their stabilities in different regimes. Finally, we compute the logarithmic correction to the entropy for both the black holes considering the quantum fluctuations around the thermal equilibrium and study the corresponding thermodynamics. 相似文献
19.
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
20.