Volume 102, Nº 6 (2025)

Within the framework of entropic cosmology, several variants of the model of the Universe evolution based on the Friedman-Robertson-Walker (FRW) equation system are considered, reconstructed taking into account a new modification of the Kaniadakis entropy at the cosmological horizon. The modification is carried out by replacing the Bekenstein-Hocking entropy in the dual expression of the Kaniadakis entropy (in which all states have the same probability) by the Barrow entropy associated with the transformation of the horizon of the Universe surface due to quantum-gravitational effects. As a result, various cosmological scenarios of the accelerated expansion of the Universe on the basis of the reconstructed FRW equations containing an additional force term depending on two free parameters of the model are obtained: the deformation parameter of the Kaniadakis entropy, which is responsible for taking into account the peculiarities of space-time, due to the long-range nature of gravitation, and the deformation parameter of the Barrow entropy, which is responsible for the fractal structure of the cosmological horizon surface, associated with the action of gravitational-quantum effects. The presence of two free parameters allows us to obtain new variants of driving forces in the FRW equations, which cause a deviation from the ‘standard’ Bekenstein-Hawking holographic model and thus lead to a more accurate approximation to reality. The proposed approach meets the known requirements for thermodynamic modelling of the dynamical evolution of the Universe without involving the concept of hypothetical dark energy and based on the use of anti-gravity entropic forces. The obtained results show that the proposed entropic formalism can open additional opportunities for deeper insight into the nature of space-time and fractal properties of the Universe horizon.

The slope of the late giants sequence in some two-colour diagrams differs significantly from the slope of other sequences and from the slope of the interstellar reddening lines. This circumstance makes M giants an indispensable source of data on both stellar parameters and interstellar extinction. The aim of the present study is to find suitable two-colour diagrams for the parameterisation of M-giants and to develop a parameterisation technique from the observed photometry. The work results in a tool for determining the intrinsic colour, spectral type and interstellar extinction parameters for the WBVR and ugriz photometric systems. The work is partially based on a talk presented at the Modern Stellar Astronomy 2024 conference.

For the effective application of the radio astronomical method for measuring the gain of large antennas, the problems of discrepancies in the flux densities of the main calibration radio sources (supernova remnants Cassiopeia A and Taurus A and the radio galaxy Cygnus A) according to data from different catalogues are analyzed, as well as taking into account their angular sizes and structure. A comparison of the data on the characteristics of these radio sources obtained at the Nizhny Novgorod Research Institute and other radio astronomical observatories over several decades is carried out.

This paper describes the design and technical features of the Rayleigh laser guide star (LGS) system as a reference source of an adaptive optical system developed for use on the Zeiss-2000 telescope of the Terskol Peak Astronomical Observatory (coordinates 43°16’34”, 42°29’57”). Experiments were performed on the Zeiss-2000 telescope to test the developed system. As a result, a signal was received from the LGS sufficient for the operation of the wavefront sensor. The presented numerical estimates of the effectiveness of adaptive correction from the Rayleigh LGS show that in the future, the use of an adaptive optical system on this telescope will significantly improve the quality of the generated image by increasing the Strehl ratio by at least ten times.