No abstract

We consider further consequences of recently [1] revealed role of cosmological constant Λ as of a physical constant, along with the gravitational one to define the gravity i.e. the General Relativity and its low-energy limit. We now show how Λ-constant affects the basic relations involving the Planck units and leads to emergence of a new dimensionless quantity (constant) which can be given cosmological information content. Within Conformal Cyclic Cosmology this approach implies the possibility of rescaling of physical constants from one aeon to another; the rescaling has to satisfy a condition involving Λ and admitting group symmetry. The emerged dimensionless information constant enables to reduce the dynamics of the universe to an algorithm of discrete steps of information increase.

Recently, the Galactic center has been reported to be a source of very high energy (VHE) γ-rays by the CANGAROO, VERITAS, and HESS experiments. The energy spectra as measured by these experiments show substantial differences. In this Letter we present MAGIC observations of the Galactic center, resulting in the detection of a differential γ-ray flux consistent with a steady, hard-slope power law, described as dNγ/(dAdtdE)=(2.9+/-0.6)×10-12(E/TeV)-2.2+/-0.2 cm-2 s-1 TeV-1. The γ-ray source is centered at (R.A., decl.) = (17h45m20s, -29°2'). This result confirms the previous measurements by the HESS experiment and indicates a steady source of TeV γ-rays. We briefly describe the observational technique used and the procedure implemented for the data analysis, and we discuss the results in the perspective of different models proposed for the acceleration of the VHE γ-rays

The recent study of the strong gravitational lens ESO 325-G004 [1] leads to a new possibility for testing General Relativity and its extensions. Such gravity lens observational studies can be instrumental for establishing a limitation on the precision of testing General Relativity in the weak-field regime and on the two gravity constants (the Newtonian and cosmological ones) as described in [2]. Namely, we predict a critical value for the involved weak-field parameter γcr = 0.998 (for M = 1.5 10 11 M⊙ lens mass and r = 2 kpc light impact distance), which remarkably does not depend on any hypothetical variable but is determined only by well measured quantities. If the critical parameter γcr will be established at future observations, this will mark the first discrepancy with General Relativity of conventional weak-field Newtonian limit, directly linked to the nature of dark sector of the Universe.

The recently sharpened H 0 tension is argued not to be a result of data calibration or any other systematic feature, but an indication for the common nature of dark matter and dark energy. This conclusion is drawn within modified weak-field General Relativity where the accelerated expansion of the Universe and the dynamics of galaxy groups and clusters are described by the same parameter, the cosmological constant. The common nature of the dark sector hence will result in an intrinsic discrepancy/tension between the local and global determinations of the values of the Hubble constant.

No abstract

The Hubble tension is shown to be solvable, without any free parameter, conceptually and quantitatively, within the approach of modified weak-field General Relativity involving the cosmological constant Λ. That approach enables one to describe in a unified picture both the dynamics of dark matter containing galaxies and the accelerated expansion of the Universe, thus defining a local Hubble constant of a local flow and the global one. The data on the dark matter content of peculiar galaxy samples are shown to be compatible to that unified picture. Future more refined surveys of galaxy distribution, hierarchical dynamics and flows within the vicinity of the Local group and the Virgo supercluster can be decisive in revealing the possible common nature of the dark sector.

The active galactic nucleus BL Lac was observed with the GT-48 atmospheric Cherenkov detector of the Crimean Astrophysical Observatory from July 23-September 1, 1998, in order to search for ultrahighenergy gamma-ray (>1 TeV) emission. The object was in the field of view of the detector for more than 24 hours. The source was detected with a high level of confidence (7.2 σ ), with a flux equal to (2.1 ± 0.4) × 10 -11 photons cm -2 s -1 . © 2001 MAIK "Nauka/Interperiodica".