scholarly journals PRIMORDIAL BLACK HOLES, HAWKING RADIATION AND THE EARLY UNIVERSE

2005 ◽  
Vol 20 (21) ◽  
pp. 1573-1576 ◽  
Author(s):  
PAUL H. FRAMPTON ◽  
THOMAS W. KEPHART
Keyword(s):  
Black Holes ◽  
Early Universe ◽  
Hawking Radiation ◽  
Cold Dark Matter ◽  
Primordial Black Holes ◽  
Gamma Emission ◽  
High Concentration ◽  
Age Of The Universe ◽  
Speculative Hypothesis ◽  
The Universe

The 511 keV gamma emission from the galactic core may originate from a high concentration (~ 1022) of primordial black holes (PBHs) in the core, each of whose Hawking radiation includes ~ 1021 positrons per second. The PBHs we consider are taken as near the lightest with longevity greater than the age of the universe (mass ~ 1012 kg ; Schwarzschild radius ~ 1 fm ). These PBHs contribute only a small fraction of cold dark matter, Ω PBH ~ 10-8. This speculative hypothesis, if confirmed implies the simultaneous discovery of Hawking radiation and an early universe phase transition.

scholarly journals The Influence of Quarks and Gluons Jets Coming from Primordial Black Holes on the Reionization of the Universe

1997 ◽  
Vol 12 (23) ◽  
pp. 4167-4198 ◽  
Author(s):  
Marina Gibilisco
Keyword(s):  
Black Holes ◽  
Plasma Heating ◽  
Critical Mass ◽  
Photon Emission ◽  
Plasma Temperature ◽  
Primordial Black Holes ◽  
Quantum Evaporation ◽  
Cooling Effects ◽  
Age Of The Universe ◽  
The Universe

In a previous work, I discussed the effect of the primordial black holes (PBH's) quantum evaporation on the reionization of the Universe at small redshifts (z ≤ 60): in principle, the photons emitted during the evaporation of such objects could drive a new ionization for the Universe after the recombination epoch; this reionization process should happen during the last stages of the PBH's life, when they totally evaporate and emit a lot of massive and massless particles. The critical mass of a black hole whose lifetime is equal to the present age of the Universe is ~ 4.4 × 1014 h-0.3 g: thus, PBH's having a mass M ~ 1014 g are the ideal candidates to induce a reionization at small redshifts. While in my previous study, I considered an exact blackbody photon emission spectrum, here I will adopt a more realistic one, taking into account the quarks and gluons jets emission through the contribution of a known fragmentation function. When the BH temperature rises above the QCD confinement scale, ΛQCD, one should expect an important contribution from quarks and gluons emission in the form of jets. In this paper I also improved my analysis by considering without any approximation the cooling effects in the plasma temperature evolution; as a result, I obtained a satisfactory "late and sudden" reionization process, characterized by a very well controlled rise of the plasma temperature: the plasma heating is not so high to induce a strong distortion of the CBR spectrum, in agreement with the recent FIRAS upper limit on the comptonization parameter, yc < 2.5 × 10-5.

scholarly journals Primordial black holes and the origin of the matter–antimatter asymmetry

2019 ◽  
Vol 377 (2161) ◽  
pp. 20190091 ◽  
Author(s):  
Juan García-Bellido
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Cold Dark Matter ◽  
Hot Spot ◽  
Large Mass ◽  
New Physics ◽  
Primordial Black Holes ◽  
Far From Equilibrium ◽  
The Universe

We review here a new scenario of hot spot electroweak baryogenesis where the local energy released in the gravitational collapse to form primordial black holes (PBHs) at the quark-hadron (QCD) epoch drives over-the-barrier sphaleron transitions in a far from equilibrium environment with just the standard model CP violation. Baryons are efficiently produced in relativistic collisions around the black holes and soon redistribute to the rest of the universe, generating the observed matter–antimatter asymmetry well before primordial nucleosynthesis. Therefore, in this scenario there is a common origin of both the dark matter to baryon ratio and the photon to baryon ratio. Moreover, the sudden drop in radiation pressure of relativistic matter at H 0 / W ± / Z 0 decoupling, the QCD transition and e + e − annihilation enhances the probability of PBH formation, inducing a multi-modal broad mass distribution with characteristic peaks at 10 −6 , 1, 30 and 10 6   M ⊙ , rapidly falling at smaller and larger masses, which may explain the LIGO–Virgo black hole mergers as well as the OGLE-GAIA microlensing events, while constituting all of the cold dark matter today. We predict the future detection of binary black hole (BBH) mergers in LIGO with masses between 1 and 5  M ⊙ , as well as above 80  M ⊙ , with very large mass ratios. Next generation gravitational wave and microlensing experiments will be able to test this scenario thoroughly. This article is part of a discussion meeting issue ‘Topological avatars of new physics’.

scholarly journals Stellar mass primordial black holes as cold dark matter

2020 ◽  
Vol 496 (1) ◽  
pp. 60-66
Author(s):  
J L G Sobrinho ◽  
P Augusto
Keyword(s):  
Phase Transition ◽  
Black Holes ◽  
Dark Matter ◽  
Mass Spectrum ◽  
Cold Dark Matter ◽  
Stellar Mass ◽  
Density Fluctuations ◽  
Primordial Black Holes ◽  
Qcd Phase Transition ◽  
The Universe

ABSTRACT Primordial black holes (PBHs) might have formed in the early Universe due to the collapse of density fluctuations. PBHs may act as the sources for some of the gravitational waves recently observed. We explored the formation scenarios of PBHs of stellar mass, taking into account the possible influence of the QCD phase transition, for which we considered three different models: crossover model, bag model, and lattice fit model. For the fluctuations, we considered a running-tilt power-law spectrum; when these cross the ∼10−9–10−1 s Universe horizon they originate 0.05–500 M⊙ PBHs that could (i) provide a population of stellar mass PBHs similar to the ones present on the binaries associated with all-known gravitational wave sources and (ii) constitute a broad-mass spectrum accounting for ${\sim}76{{\ \rm per\ cent}}$ of all cold dark matter in the Universe.

scholarly journals Dynamic of the Accelerated Expansion of the Universe in the DGP Model

2011 ◽  
Vol 21 (3) ◽  
pp. 253 ◽  
Author(s):  
Vo Quoc Phong
Keyword(s):  
Experimental Data ◽  
Growth Rate ◽  
Cold Dark Matter ◽  
Growth Index ◽  
Cosmic Acceleration ◽  
Accelerated Expansion ◽  
Density Parameter ◽  
Type Ia ◽  
Age Of The Universe ◽  
The Universe

According to experimental data of SNe Ia (Supernovae type Ia), we will discuss in detial dynamics of the DGP model and introduce a simple parametrization of matter $\omega$, in order to analyze scenarios of the expanding universe and the evolution of the scale factor. We find that the dimensionless matter density parameter at the present epoch $\Omega^0_m=0.3$, the age of the universe $t_0= 12.48$ Gyr, $\frac{a}{a_0}=-2.4e^{\frac{-t}{25.56}}+2.45$. The next we study the linear growth of matter perturbations, and we assume a definition of the growth rate, $f \equiv \frac{dln\delta}{dlna}$. As many authors for many years, we have been using a good approximation to the growth rate $f \approx \Omega^{\gamma(z)}_m$, we also find that the best fit of the growth index, $\gamma(z)\approx 0.687 - \frac{40.67}{1 + e^{1.7. (4.48 + z)}}$, or $\gamma(z)= 0.667 + 0.033z$ when $z\ll1$. We also compare the age of the universe and the growth index with other models and experimental data. We can see that the DGP model describes the cosmic acceleration as well as other models that usually refers to dark energy and Cold Dark Matter (CDM).

scholarly journals Primordial black holes from the QCD epoch: linking dark matter, baryogenesis, and anthropic selection

2020 ◽  
Vol 501 (1) ◽  
pp. 1426-1439
Author(s):  
Bernard Carr ◽  
Sebastien Clesse ◽  
Juan García-Bellido
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Selection Effect ◽  
Mass Function ◽  
Baryon Asymmetry ◽  
Primordial Black Holes ◽  
Cosmological Horizon ◽  
Chandrasekhar Limit ◽  
The Universe ◽  
Characteristic Mass

ABSTRACT If primordial black holes (PBHs) formed at the quark-hadron epoch, their mass must be close to the Chandrasekhar limit, this also being the characteristic mass of stars. If they provide the dark matter (DM), the collapse fraction must be of order the cosmological baryon-to-photon ratio ∼10−9, which suggests a scenario in which a baryon asymmetry is produced efficiently in the outgoing shock around each PBH and then propagates to the rest of the Universe. We suggest that the temperature increase in the shock provides the ingredients for hotspot electroweak baryogenesis. This also explains why baryons and DM have comparable densities, the precise ratio depending on the size of the PBH relative to the cosmological horizon at formation. The observed value of the collapse fraction and baryon asymmetry depends on the amplitude of the curvature fluctuations that generate the PBHs and may be explained by an anthropic selection effect associated with the existence of galaxies. We propose a scenario in which the quantum fluctuations of a light stochastic spectator field during inflation generate large curvature fluctuations in some regions, with the stochasticity of this field providing the basis for the required selection. Finally, we identify several observational predictions of our scenario that should be testable within the next few years. In particular, the PBH mass function could extend to sufficiently high masses to explain the black hole coalescences observed by LIGO/Virgo.

scholarly journals Discovery of the first heavily obscured QSO candidate at z > 6 in a close galaxy pair

2019 ◽  
Vol 628 ◽  
pp. L6 ◽  
Author(s):  
F. Vito ◽  
W. N. Brandt ◽  
F. E. Bauer ◽  
R. Gilli ◽  
B. Luo ◽  
...  
Keyword(s):  
Black Holes ◽  
Early Universe ◽  
Column Density ◽  
Early Growth ◽  
Point Of View ◽  
X Ray ◽  
Confidence Levels ◽  
The Universe ◽  
Companion Galaxy

While theoretical arguments predict that most of the early growth of supermassive black holes (SMBHs) happened during heavily obscured phases of accretion, current methods used for selecting z >  6 quasars (QSOs) are strongly biased against obscured QSOs, thus considerably limiting our understanding of accreting SMBHs during the first gigayear of the Universe from an observational point of view. We report the Chandra discovery of the first heavily obscured QSO candidate in the early universe, hosted by a close (≈5 kpc) galaxy pair at z = 6.515. One of the members is an optically classified type-1 QSO, PSO167–13. The companion galaxy was first detected as a [C II] emitter by Atacama large millimeter array (ALMA). An X-ray source is significantly (P = 0.9996) detected by Chandra in the 2–5 keV band, with < 1.14 net counts in the 0.5–2 keV band, although the current positional uncertainty does not allow a conclusive association with either PSO167–13 or its companion galaxy. From X-ray photometry and hardness-ratio arguments, we estimated an obscuring column density of NH >  2 × 1024 cm−2 and NH >  6 × 1023 cm−2 at 68% and 90% confidence levels, respectively. Thus, regardless of which of the two galaxies is associated with the X-ray emission, this source is the first heavily obscured QSO candidate at z >  6.

scholarly journals Variation of the fundamental constants over the cosmological time: veracity of Dirac’s intriguing hypothesis

2016 ◽  
Vol 94 (1) ◽  
pp. 89-94 ◽  
Author(s):  
Cláudio Nassif ◽  
A.C. Amaro de Faria
Keyword(s):  
Fine Structure ◽  
Early Universe ◽  
Early Period ◽  
Planck Scale ◽  
Structure Constant ◽  
Energy Scale ◽  
Fine Structure Constant ◽  
Cosmological Time ◽  
Age Of The Universe ◽  
The Universe

We investigate how the universal constants, including the fine structure constant, have varied since the early universe close to the Planck energy scale (EP ∼ 1019 GeV) and, thus, how they have evolved over the cosmological time related to the temperature of the expanding universe. According to a previous paper (Nassif and Amaro de Faria, Jr. Phys. Rev. D, 86, 027703 (2012). doi:10.1103/PhysRevD.86.027703), we have shown that the speed of light was much higher close to the Planck scale. In the present work, we will go further, first by showing that both the Planck constant and the electron charge were also too large in the early universe. However, we conclude that the fine structure constant (α ≅ 1/137) has remained invariant with the age and temperature of the universe, which is in agreement with laboratory tests and some observational data. Furthermore, we will obtain the divergence of the electron (or proton) mass and also the gravitational constant (G) at the Planck scale. Thus, we will be able to verify the veracity of Dirac’s belief about the existence of “coincidences” between dimensionless ratios of subatomic and cosmological quantities, leading to a variation of G with time, that is, the ratio of the electrostatic to gravitational forces between an electron and a proton (∼1041) is roughly equal to the age of the universe divided by an elementary time constant, so that the strength of gravity, as determined by G, must vary inversely with time in the approximation of lower temperature or for times very far from the early period, to compensate for the time-variation of the Hubble parameter (H ∼ t−1). In short, we will show the validity of Dirac’s hypothesis only for times very far from the early period or T ≪ TP (∼1032 K).

scholarly journals PRE INFLATION MATTER ERA AND CMB ANOMALY

2012 ◽  
Vol 12 ◽  
pp. 390-399
Author(s):  
FABIO SCARDIGLI ◽  
CHRISTINE GRUBER ◽  
PISIN CHEN
Keyword(s):  
Black Holes ◽  
Power Spectrum ◽  
Observational Data ◽  
Early Universe ◽  
The Universe

We consider the production of primordial micro black holes (MBH) remnants in the early universe. These objects induce the universe to be in a matter-dominated era before the onset of inflation. Effects of such an epoch on the CMB power spectrum are discussed and computed both analytically and numerically. By comparison with the latest observational data from the WMAP collaboration, we find that our model appears to explain the quadrupole anomaly of the CMB power spectrum.

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