arXiv subjects

G. G. Adamian

Publications and source records attributed to G. G. Adamian.

At least 19 recordsLinked to original sources

arXiv2026

A Question of Shape: New Mechanism Governing Superheavy Nuclei Survival

We demonstrate that hot superheavy nuclei do not retain spherical shapes, as traditionally assumed, but instead equilibrate in deformed, often oblate or triaxial, configurations at finite excitation energy. This behavior arises from a mechanism analogous to the Jahn-Teller effect: spherical systems exhibit high single-particle degeneracy near the Fermi surface, causing their shell corrections to damp out significantly faster with temperature than those of deformed shapes. Using a finite-temperature framework, we reveal a thermally induced inversion of the potential-energy landscape in the Z = 118-120 region, where deformed minima become energetically favored at U = 30-50 MeV. This shape inversion fundamentally alters the competition between neutron evaporation and fission. We derive a deformation-dependent correction to the survival probability, revealing a systematic bias in estimates based on spherical ground-state properties. Our results identify a finite-temperature structural effect that calls for a revision of current models of superheavy-nucleus synthesis and decay.

nucl-th↗

arXiv2025

Dependence of angular momentum of fission fragments on total kinetic energy in spontaneous fission of $^{252}$Cf

A weak dependence of the angular momentum of $^{144}$Ba fragments, produced in the spontaneous fission of $^{252}$Cf, on the total kinetic energy (TKE) was recently observed \cite{Giha2025}. To investigate this phenomenon, we propose a model describing the evolution of the fissioning nucleus toward scission. The model assumes that after tunneling through the fission barrier, the nucleus can be represented by a superposition of dinuclear systems (DNS). We calculate main fission observables, including mass, TKE, and neutron multiplicity distributions, and compare them with experimental data. The angular motion in the DNS is treated quantum-mechanically, yielding the angular momentum distribution of DNS nuclei at scission configurations leading to $^{144}$Ba fragments. Within this framework, we successfully reproduce and explain the experimentally observed dependence of the average angular momentum of $^{144}$Ba on TKE.

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arXiv2024

Self-oscillating open quantum systems

Evolution of occupation number is studied for a bosonic oscillator (with one and two degrees of freedom) linearly fully coupled to fermionic and bosonic heat baths. The lack of equilibrium in this oscillator is discussed in the light of the creation of an energy source. The connection of such a system with known nonlinear self-oscillating systems is shown.

quant-ph↗

arXiv2024

Quantum-mechanical description of angular motion of fission fragments at scission

The quantum-mechanical description of the collective angular motion in a system of two touching fission fragments is proposed. The main peculiarities of excitation spectrum and the structure of the wave functions are investigated. As found, the angular motion approximately corresponds to independent vibrations of fragments around the pole-to-pole configuration. The model allows us to explain the experimentally observed lack of correlation between the angular momenta of fission fragments. Additionally the correlation between angular momentum and fragment mass is primarily linked to the change of fragments deformation. The saw-tooth behavior of angular momentum distribution with respect to the fragment mass is well explained.

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arXiv2024

Entropies, level-density parameters, and fission probabilities along the triaxially- and axially-symmetric fission paths in $^{296}$Lv

We employ a statistical approach to investigate the influence of axial asymmetry on the nuclear level density and entropy along the fission pathways of a superheavy nucleus, explicitly focusing on the $^{296}$Lv isotope. These pathways are determined within multidimensional deformation spaces. Our analysis reveals a significant impact of triaxiality on entropy. Additionally, suppressing shell effects can alter the fission scenario depending on the available excitation energy. We derive the deformation-dependent level density parameter, which plays a crucial role in estimating the survival probability of a superheavy nucleus. Furthermore, we utilize a set of master equations to obtain the time-dependent fission probabilities and calculate the ratio of decay probabilities for both axial and triaxial paths.

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arXiv2023

Multi-step particle emission probabilities in superheavy nuclei at moderate excitation energies

The probabilities of $xn$-, $pxn$-, and $αxn$-evaporation channels in excited superheavy nuclei were evaluated using the Monte Carlo method. The calculations utilized microscopically determined nuclear level densities and were compared with results obtained from the phenomenological Jackson formula. Effective temperatures derived from the microscopic approach were incorporated into the Jackson formula for different evaporation channels at low and moderate excitation energies. Additionally, an analytical formula was introduced to estimate the average kinetic energy of emitted particles in multi-step processes.

nucl-th↗

arXiv2021

Application of Regge-theory to astronomical objects

Using the model based on the Regge-like laws, new analytical formulas are obtained for the moment of inertia, the rotation frequency, and the radius of astronomical non-exotic objects (planets, stars, galaxies, and clusters of galaxies). The rotation frequency and moment of inertia of neutron star and the observable Universe are estimated. The estimates of the average numbers of stars and galaxies in the observable Universe are given. The Darwin instability effect in the binary systems (di-planets, di-stars, and di-galaxies) is also analyzed.

physics.class-ph↗

arXiv2021

New type of self-oscillating systems

The time evolution of occupation number is studied for a bosonic oscillator (with one and two degrees of freedom) linearly fully coupled to fermionic and bosonic heat baths. The absence of equilibrium in this oscillator is discussed as a tool to create a dynamical non-stationary memory storage. The connection between such a system and the well-known nonlinear self-oscillating systems is demonstrated.

quant-ph↗

arXiv2021

The decline rate of the production cross-section of superheavy nuclei with $Z=114-117$ at high excitation energies

The production cross sections of superheavy nuclei with charge numbers $114-117$ are predicted in the $(5-9)n$-evaporation channels of the $^{48}$Ca-induced complete fusion reactions for future experiments. The estimates of synthesis capabilities are based on a uniform and consistent set of input nuclear data provided by the multidimensional macroscopic-microscopic approach. The contributions of various factors to the final production cross section are discussed. As shown, the specific interplay between survival and fusion probabilities unexpectedly leads to a relatively slow decline of the total cross-sections with increasing excitation energy. This effect is supported by a favorable arrangement of fission barriers protecting the compound nucleus against splitting concerning energetic thresholds for the emission of successive neutrons. In particular, the probabilities of the formation of superheavy nuclei in the $5n$-, $6n$-, and in some cases even in $7n$-evaporation channels are still promising. This may offer a new opportunity for the future synthesis of unknown neutron-deficient superheavy isotopes.

nucl-th↗

arXiv2021

Applicability of the absence of equilibrium in quantum system fully coupled to several fermionic and bosonic heat baths

The time evolution of occupation number is studied for fermionic or bosonic oscillator linearly fully coupled to several fermionic and bosonic heat baths. The influence of characteristics of thermal reservoirs of different statistics on the non-stationary population probability is analyzed at large times. Applications of the absence of equilibrium in such systems for creating a dynamic (nonstationary) memory storage are discussed.

quant-ph↗

arXiv2020

On the evolution of compact binary black holes

Based on the consideration of potential energy of the di-black-hole as a function of mass asymmetry (transfer) collective coordinate, the possibility of matter transfer between the black holes in a binary system is investigated. The sensitivity of the calculated results is studied to the value of the total mass of binary system. The conditions for the merger of two black holes are analyzed in the context of gravitational wave emission.

astro-ph.GA↗

arXiv2020

Non-Markovian modeling of Fermi-Bose systems coupled to one or several Fermi-Bose thermal baths

A method is proposed to describe Fermi or Bose systems coupled to one or several heat baths composed of fermions and/or bosons. The method, called Coupled Equations of Motion method, properly includes non-Markovian effects. The approach is exact in the Full-Coupling approximation when only bosonic particles are present in the system and baths. The approach provides an approximate treatment when fermions are present either in the system and/or in one or several environments. The new approach has the advantage to properly respect the Pauli exclusion principle for fermions during the evolution. We illustrate the approach for the single Fermi or Bose two-level system coupled to one or two heat-baths assuming different types of quantum statistics (Fermion or Bosons) for them. The cases of Fermi system coupled to fermion or boson heat baths or a mixture of both are analyzed in details. With the future goal to treat Fermi systems formed of increasing number of two-level systems (Qubits), we discuss possible simplifications that could be made in the equations of motion and their limits of validity in terms of the system--baths coupling or of the initial heat baths temperatures.

quant-ph↗

arXiv2020

Possibilities of direct production of superheavy nuclei with Z=112--118 in different evaporation channels

The production cross sections of heaviest isotopes of superheavy nuclei with charge numbers 112--118 are predicted in the $xn$--, $pxn$--, and $αxn$--evaporation channels of the $^{48}$Ca-induced complete fusion reactions for future experiments. The estimates of synthesis capabilities are based on a uniform and consistent set of input nuclear data. Nuclear masses, deformations, shell corrections, fission barriers, and decay energies are calculated within the macroscopic-microscopic approach for even-even, odd-Z, and odd-N nuclei. For odd systems, the blocking procedure is used. To find, the ground states via minimization and saddle points using Immersion Water flow technique, multidimensional deformation spaces, containing non-axially are used. As shown, current calculations based on a new set of mass and barriers, agree very well with experimentally known cross-sections, especially in the $3n$--evaporation channel. The dependencies of these predictions on the mass/fission barriers tables and fusion models are discussed. A way is shown to produce directly unknown superheavy isotopes in the $1n$-- or $2n$--evaporation channels. The synthesis of new superheavy isotopes unattainable in reactions with emission of neutrons is proposed in the promising channels with emission of protons ($σ_{pxn} \simeq 10-200$ fb) and alphas ($σ_{αxn} \simeq 5-500$ fb).

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arXiv2020

Extended quantum diffusion approach to reactions of astrophysical interests

The quantum diffusion approach is extended to low energy fusion (capture) reactions of light- and medium-mass nuclei. The dependence of the friction parameter on bombarding energy is taken into account. A simple analytic expression is obtained for the capture probability at extreme sub-barrier energies. The calculated cross-sections are in a good agreement with the experimental data. The fusion excitation functions calculated within the quantum diffusion and WKB approaches are compared and presented in the astrophysical $S$-factor representation.

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arXiv2019

On the Darwin instability effect in binary systems

The Darwin instability effect in the binary systems (planets, stars, and galaxies) is analyzed within the model based on the Regge-like laws. New analytical formulas are presented for the relative distance between components of the binary and orbital rotation period of the binary.

astro-ph.SR↗

arXiv2019

Origin of the orbital period change in contact binary stars

The evolution of contact binary star systems in mass asymmetry (transfer) coordinate is considered. The orbital period changes is explained by an evolution in mass asymmetry towards the symmetry (symmetrization of binary system). It is predicted that a decreasing and an increasing orbital periods are related, respectively, with the non-overlapping and overlapping stage of the binary star during its symmetrization. A huge amount of energy $ΔU\approx 10^{41}$ J is converted from the potential energy into internal energy of the stars during the symmetrization. As shown, the merger of stars in the binary systems, including KIC 9832227, is energetically an unfavorable process. The sensitivity of the calculated results to the values of total mass and orbital angular momentum is analyzed.

astro-ph.SR↗

arXiv2019

Close Binary Galaxies: Application to Source of Energy and Expansion in Universe

Applying the microscopic nuclear physics ideas for fusion reactions to macroscopic galactic systems, we study the evolution of the compact binary galaxy in mass asymmetry (transfer) coordinate. The conditions for the formation of stable symmetric binary galaxy are analyzed. The role of symmetrization of asymmetric binary galaxy in the transformation of gravitational energy into internal energy of galaxies accompanied by the release of a large amount of energy during the symmetrization process is revealed.

astro-ph.GA↗

arXiv2019

Derivation of general Maxwell type equations for open quantum systems

Using equations of motion with the anisotropic dissipative term for quantum particle and quantum-mechanical commutation rules, the general Maxwell-type differential equations are derived. The direct modifications of the well-known Maxwell equations due to the medium effects (openness of the system) are discussed.

physics.class-ph↗