Reconstructions of f(P) gravity from (m,n) type ordinary and entropy-corrected holographic and Pilgrim dark energy models

Modified gravity models are popular among cosmologists, as they can describe the cosmological evolution quite efficiently. Reconstruction of newly introduced [Formula: see text] gravity, with the help of ordinary, power-law entropy corrected and logarithmic entropy-corrected versions of Holographic dark energy (HDE) and Pilgrim dark energy (PDE) models have been studied in this work. For such reconstruction, we have considered the power-law scale factor [Formula: see text]. Further, the classical stabilities (the squared speed of sound method) of such reconstructions and their implications on the nature of the equation of state (EoS) parameters and deceleration parameter with respect to red-shift have also been examined. Finally, we have computed the age of the universe for reconstructed models.

Thermal production of sexaquarks in heavy-ion collisions

We present new results on the thermal production yield of a hypothetical state made of six quarks [Formula: see text] assuming its production in heavy-ion collisions at the CERN Large Hadron Collider (LHC). A state with this quark content and mass low enough to be stable against decay in timescales of the order of the age of the Universe has been hypothesized by one of us (G. Farrar) and has been discussed as a possible dark matter candidate. In this work, we address for the first time the thermal production rate that can be expected for this state in heavy-ion collisions at colliders. For this estimate we use a thermal model which has been shown to describe accurately the production of hadrons and nuclei in heavy-ion collisions at LHC energy. This estimate is of great relevance for sexaquark searches at colliders as well as for its consideration as a dark matter candidate and for the composition of neutron stars.

Implications of quantum gravity for dark matter

In this essay, we show that quantum gravity and the spin-statistics theorem have very interesting consequences for dark matter candidates. Quantum gravity can lead to fifth force type interactions that lead to a lower bound on the masses of bosonic candidates. In the case of fermions, the spin-statistics theorem leads to a lower bound on fermion masses. For both bosonic and fermionic dark matter candidates, quantum gravity leads to a decay of dark matter particles. A comparison of their lifetime with the age of the universe leads to an upper bound on their masses. For singlet scalar dark matter fields, we find [Formula: see text].

A BL Lacertae object at a cosmic age of 800 Myr

BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs), known as blazars, are low- and high-luminosity radio-loud Active Galactic Nuclei (AGNs) with relativistic jets pointed towards Earth (1). Evolving from FSRQs (2,3), BL Lac objects host ~109 Msun supermassive black holes (SMBHs, where Msun is the mass of the Sun) and reside preferentially in giant elliptical galaxies of stellar masses 1011-1012Msun (4-7). The known BL Lacs are relatively nearby objects found below redshift 3.6 (3,8,9). Here, we report the discovery of a BL Lac object, FIRST J233153.20+112952.11 (hereafter J2331+11), at a redshift of 6.57 corresponding to an age of the Universe of ~800 Myr. As the typical BL Lac, J2331+11 is a compact radio source with the flat power-law radio continuum, no emission lines in its near-infrared spectrum, and significant variability. The optical-to-radio continuum of J2331+11 is entirely dominated by the synchrotron emission of a relativistic jet. J2331+11 provides evidence for the shorter formation timescale of massive SMBHs with jets and bulge-dominated galaxies than that expected from the Eddington-limited growth of SMBHs and hierarchical galaxy formation. The rapid formation of BL Lacs at early cosmic epochs should have taken place in the densest regions of the early Universe.

Analytical Solution to FRW Metric with Variable Speed of Light

<p>According to the principle of general covariance, the laws of physics are the same in all reference frames. The controversial theory of the Varying Speed of Light (VSL) contradicts the principle of general covariance. Fortunately the VLS theory explains some crucial issues in cosmology such as Lorentz variance, biometric theories, locally Lorentz variance, cosmological constant problem, horizon<em> </em>and flatness<em> </em>problems. Also, recent astronomical observations from quasar show that the fine structural constant depends on redshift and therefore, varies with cosmological time. In other to harness this fascinating and published knowledge, two models where used in this work. 1. Cosmology with variables c; here the Friedmann-Robertson-Walker (FRW) is used in the Einstein field equation with variable c and Λ terms to obtain the scale factor, which shows the continuous exponential expansion of the universe. 2. Variation of the speed of light as a function of the scale factor of the universe; here we obtained: a good approximation to estimate the current age of the universe. The scale factor of the universe depends its content given by the equation of state parameter ω. We obtained the deceleration parameter in terms of the Hubble parameter. We arrived at a conclusion that the universe was decelerating at ω = 1, accelerating at ω = 1/3 and the Hubble parameter diverges at the beginning and end of the universe.</p>

The Expansion Dance of Alpha Centauri

Using Alpha Centauri as an example, it will be investigated how two-mass systems rotating around their barycenter evolve with the age of the universe. It is calculated how change the masses, the periods, the distance and the gravitational value. As the universe ages, both mases fall, the gravitational value increases quadratically, all system periods increase, and the distance between the two objects increases with the periods. The eccentric dance of the two stars expands accordingly.