Related papers: MACHO Messages from the Big Bang
A substantial part of the dark matter of the Universe could be in the form of compact objects (MACHOs), detectable through gravitational microlensing effects as they pass through the line of sight to background light sources. So far, most…
We propose that the massive compact halo objects (MACHOs) observed in the recent microlensing experiments with an apparent best fit mass of about $0.5 M_{\odot}$ are objects made out of ``mirror'' baryonic matter rather than familiar…
Recent results from gravitational microlensing experiments, such as MACHO, indicate that a substantial fraction of the Galactic dark matter (DM) is in compact form, with a typical mass in the range ~0.05 - 1 Mo. This mass range favours the…
Primordial black holes (PBHs) are considered viable candidates for dark matter and the seeds of supermassive black holes (SMBHs), with their fruitful physical influences providing significant insights into the conditions of the early…
Observations by the MACHO collaboration suggest that a significant proportion of the galactic halo dark matter is in the form of compact objects with typical masses $M\sim 0.5M_{\odot}$. One of the current mysteries is the nature and origin…
We propose a simple model in which the cosmological dark matter consists of particles whose mass increases with the scale factor of the universe. The particle mass is generated by the expectation value of a scalar field which does not have…
We present the basics of microlensing and give an overview of the results obtained so far. We also describe a scenario in which dark clusters of MACHOs (Massive Astrophysical Compact Halo Objects) and cold molecular clouds (mainly of $H_2$)…
The expansion history of the Universe is calculated using a simple model in which the entire rest mass energy of a massive particle is distributed throughout the set of Machian strings connecting it to all the other particles in the…
Cosmological models in which dark matter consists of cold elementary particles predict that the dark halo population should extend to masses many orders of magnitude below those at which galaxies can form. Here we report a cosmological…
Recent observations of microlensing events in the Large Magellanic Cloud suggest that a sizable fraction of the galactic halo is in the form of Massive Astrophysical Compact Halo Objects (MACHOs). Although the average MACHO mass is…
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…
Motivated by inflation, the theory of big-bang nucleosynthesis and the quest for a deeper understanding of the fundamental forces and particles, a very successful paradigm for the development of structure in the Universe has evolved. It…
Primordial Black Holes (PBH) with masses of order $10-30 M_\odot$ have been proposed as a possible explanation of the gravitational waves emission events recently discovered by the LIGO observatory. If true, then PBHs would constitute a…
Evidence of neutron stars with deconfined quark-matter cores suggest a new pathway for the evolution of black holes. New theories about the cores of neutron stars support the idea that quarkonium is likely to grow there as the neutron star…
We investigate the possibility that present-day galactic haloes contain a population of massive black holes (MBHs) that form by hierarchical merging of the black hole remnants of the first stars. Some of the MBHs may be large enough or…
Considering the fact that the present universe might have been formed out of a system of ficticious self-gravitating particles, fermionic in nature, each of mass $m$, we are able to obtain a compact expression for the radius $R_0$ of the…
Many inflation theories predict that the primordial power spectrum is scale invariant. The amplitude of the power spectrum can be constrained by different observations such as the cosmic microwave background (CMB), Lyman-$\alpha$,…
If MACHOs are black holes of mass about 0.5 solar mass, they must have been formed in the early universe when the temperature was about 1 GeV. We estimate that in this case in our galaxy's halo out to about 50kpc there exist about half…
Observations of high-redshift quasars indicate that super massive black holes (SMBHs) with masses greater than ${\sim}10^9~M_\odot$ were assembled within the first billion years after the Big Bang. It is unclear how such massive black holes…
Primordial black holes (PBHs) could provide the dark matter in various mass windows below $10^2 M_{\odot}$ and those of $30 M_{\odot}$ might explain the LIGO events. PBHs much larger than this might have important consequences even if they…