Does Our Universe Conform with the Existence of a Universal Maximum Energy-Density <i>p_max<sup style="margin-left:-30px;">uni</sup></i>

Recent astronomical observations of high redshift quasars, dark matter-dominated galaxies, mergers of neutron stars, glitch phenomena in pulsars, cosmic microwave background and experimental data from hadronic colliders do not rule out, but they even support the hypothesis that the energy-density in our universe most likely is upper-limited by pmaxuni which is predicted to lie between 2 to 3 the nuclear density p0. Quantum fluids in the cores of massive NSs with p ≈ pmaxuni each the maximum compressibility state, where they become insensitive to further compression by the embedding spacetime and undergo a phase transition into the purely incompressible gluon-quark superfluid state. A direct correspondence between the positive energy stored in the embedding spacetime and the degree of compressibility and superfluidity of the trapped matter is proposed. In this paper relevant observational signatures that support the maximum density hypothesis are reviewed, a possible origin of pmaxuni is proposed and finally the consequences of this scenario on the spacetime’s topology of the universe as well as on the mechanisms underlying the growth rate and power of the high redshift QSOs are discussed.

Statistical Mechanical Entropy of a （4 ＋ n）-Dimensional Static Spherically Symmetric Black Hole

Considering corrections to all orders in the Planck length on the quantum state density from the generalized uncertainty principle and using the quantum state density to all degrees of freedom including extra dimensions, we calculate the statistical entropy of the scalar field in the higher-dimensional static spherically symmetric black hole spacetime without any artificial cutoff. Calculation shows that the entropy is proportional to the horizon area. The coefficient of proportionality is 1/4 when the minimal length parameter is selected appropriately.

The clustering of QSOs and the dark matter halos that host them

The spatial clustering of QSOs is an important measurable quantity which can be used to infer the properties of dark matter halos that host them.We construct a simple QSO model to explain the linear bias of QSOs measured by recent observations and explore the properties of dark matter halos that host a QSO.We assume that major mergers of dark matter halos can lead to the triggering of QSO phenomena,and the evolution of luminosity for a QSO generally shows two accretion phases,i.e.,initially having a constant Eddington ratio due to the self-regulation of the accretion process when supply is sufcient,and then declining in rate with time as a power law due to either diminished supply or long term disk evolution.Using a Markov Chain Monte Carlo method,the model parameters are constrained by fitting the observationally determined QSO luminosity functions（LFs）in the hard X-ray and in the optical band simultaneously.Adopting the model parameters that best fit the QSO LFs,the linear bias of QSOs can be predicted and then compared with the observational measurements by accounting for various selection efects in diferent QSO surveys.We find that the latest measurements of the linear bias of QSOs from both the SDSS and BOSS QSO surveys can be well reproduced.The typical mass of SDSS QSOs at redshift 1.5

Primordial black holes

Primordial black holes （PBHs） are a profound signature of primordial cosmological structures and provide a theoretical tool to study nontrivial physics of the early Universe. The mechanisms of PBH formation are discussed and observational constraints on the PBH spectrum, or effects of PBH evaporation, are shown to restrict a wide range of particle physics models, predicting an enhancement of the ultraviolet part of the spectrum of density perturbations, early dust-like stages, first order phase transitions and stages of superheavy metastable particle dominance in the early Universe. The mechanism of closed wall contraction can lead, in the inflationary Universe, to a new approach to galaxy formation, involving primordial clouds of massive BHs created around the intermediate mass or supermassive BH and playing the role of galactic seeds.