arXiv subjects

Ludmila M. Svirskaya

Publications and source records attributed to Ludmila M. Svirskaya.

4 recordsLinked to original sources

arXiv2026

Conductor-Insulator Crossover in the Steady-State Ultracold Plasmas

We present a theoretical model of the ionization-recombination balance in the ultracold Rydberg gas-plasma mixture, which is caused by the collective processes rather than by individual interparticle interactions. We consider the electron-ion system where each electron moves for the most part of its time in the effective centrifugal potential formed by the nearest ion and sometimes jumps to the neighboring potential wells due to the perturbations from remote particles. These perturbations are described by a thermal bath with the effective "virial" temperature. Then, the electron with a sufficiently high energy, which can escape from the local potential well, should be considered as free (conducting) one; while the electron with low energy, confined within the well, as forming the Rydberg atom. As follows from our calculations, there is a sharp crossover from the insulating phase (Rydberg gas) to the conducting one (plasma) with increase in the particle density, which somewhat resembles the Mott transition in condensed-matter physics. This model should be well relevant to the steady-state ultracold plasmas obtained in the most recent experiments and represents a promising direction for further research.

physics.plasm-ph↗

arXiv2026

Non-equilibrium classical recombination in the expanding ultracold plasmas

The efficiency of recombination is of crucial importance for the existence of ultracold plasmas (UCP), particularly, the ones formed in the magneto-optical traps. Unfortunately, the equilibrium thermodynamic treatment of the ionization-recombination processes is inappropriate for the evolving UCP clouds, while the straightforward kinetic simulation encounters the problem of huge difference in the spatial and temporal scales for free and bound motion of the electrons. As a result, only the "virtual" electron-ion pairs are usually reproduced in such modeling, and it is necessary to employ some heuristic criteria to identify them with the recombined atoms. It is the aim of this paper to present the first successful ab initio simulation of the non-equilibrium recombination in the evolving UCP plasmas. We employed a special algorithm, which is based on using the "scalable" reference frame, co-moving with the expanding substance. Then, the recombination events are identified by a series of sharp equidistant peaks in the kinetic and/or potential energies, which are caused by the captured electrons passing near the pericenters of their orbits; and this is confirmed by a detailed inspection of their trajectories. Thereby, we were able to trace the real - rather than "virtual" - electron-ion pairs, and the total efficiency of their formation was found to be about 20%, which is in agreement with the laboratory measurements.

physics.plasm-ph↗

arXiv2025

Estimating the Local Hubble Parameter from the Thermal Evolution of Earth and Mars

The problem of local (e.g., interplanetary) Hubble expansion is studied for a long time but remains a controversial subject till now; and of particular interest is a plausible value of the local Hubble parameter at the scale of the Solar system. Here, we tried to estimate the corresponding quantity by the analysis of surface temperatures on the Earth and Mars, which are formed by a competition between a variable luminosity of the Sun and increasing radii of the planetary orbits. Our work employs paleochemical and paleobiological data on the temperature of the ancient Earth, on the one hand, and geological data on the existence of an ocean of liquid water on the ancient Mars, on the other hand. As follows from our analysis, the martian data impose only a weak constraint on the admissible values of the Hubble parameter because of the unknown salinity - and, therefore, the freezing point - of the martian water. On the other hand, the terrestrial data turn out to be much more valuable, especially, for the Precambrian period, when temperature variation was sufficiently smooth and monotonic. For example, in the framework of standard LambdaCDM model with 70% of dark energy, contemporary value of the local Hubble parameter was found to be 70-90 km/s/Mpc under assumption that the Earth's surface temperature in the end of Precambrian equaled 45 C. This is in reasonable agreement both with the intergalactic data and with an independent estimate of the local Hubble parameter from tidal evolution of the Earth-Moon system.

astro-ph.EP↗

arXiv2025

On the Nature of Subharmonics of the Electron Emission from Ultracold Plasmas

One of the most interesting phenomena in the ultracold plasmas are multiple subharmonics of the electron emission observed after its irradiation by the monochromatic radiowaves. Unfortunately, the early interpretation of this phenomenon as the so-called Tonks-Dattner resonances (i.e., actually the standing Langmuir waves) encountered a number of serious obstacles, such as a lack of the adequate boundary conditions, an incorrect dependence on the electron temperature, and an insensitivity to the shape of the cloud. Here, we suggest an alternative interpretation based on the quasi-classical multiphoton ionization of the 'secondary' Rydberg atoms formed in the expanding and cooling plasma clouds. As follows from our numerical simulations, the efficiency of such ionization exhibits a series of well-expressed peaks. Moreover, this process is evidently irrelevant to the boundary conditions and global shape of the cloud. Therefore, this should be a viable alternative to the earlier idea of Tonks--Dattner resonances.

physics.plasm-ph↗