arXiv subjects

Rashid G. Nazmitdinov

Publications and source records attributed to Rashid G. Nazmitdinov.

12 recordsLinked to original sources

arXiv2015

Origin of masses in the Early Universe

New model is suggested, where the Casimir mechanism is the source of masses and conformal symmetry breaking at the Planck epoch in the beginning of the Universe. The mechanism is the Casimir energy and associated condensate, which are resulted from the vacuum postulate and normal ordering of the conformal invariant Hamiltonian with respect to the quantum elementary field operators. It is shown that the Casimir top-quark condensate specifies the value of the Higgs particle mass without involving the Higgs tachyon mass, which is put equal to zero. The Casimir mechanism yields another value of the coupling constant for the self-interaction of scalar field than the standard model does.

gr-qc↗

arXiv2006

Wobbling excitations in 156Dy and 162Yb

We study in the cranked Nilsson plus random phase approximation low-lying quadrupole excitations of positive parity and negative signature in 156Dy and 162Yb at high spins. Special attention is paid to a consistent description of wobbling excitations and their identification among excited states. A good agreement between available experimental data and the results of calculations is obtained. We found that in 156Dy the lowest odd spin gamma-vibrational states transform to the wobbling excitations after the backbending, associated with the transition from axially-symmetric to nonaxial shapes. Similar results are predicted for 162Yb. The analysis of electromagnetic transitions, related to the wobbling excitations, determines uniquely the sign of the gamma-deformation in 156Dy and 162Yb after the transition point.

nucl-th↗

arXiv2005

Interplay between Zeeman interaction and spin-orbit coupling in a two-dimensional semiconductor system

We analyse the interplay between Dresselhaus, Bychkov-Rashba, and Zeeman interactions in a two-dimensional semiconductor quantum system under the action of a magnetic field. When a vertical magnetic field is considered, we predict that the interplay results in an effective cyclotron frequency that depends on a spin-dependent contribution. For in-plane magnetic fields, we found that the interplay induces an anisotropic effective gyromagnetic factor that depends on the orientation of the applied field as well as on the orientation of the electron momentum.

cond-mat.mes-hall↗

arXiv2004

Wobbling excitations and tilted rotation in 163-Lu

Using a microscopic self-consistent model, we analyse wobbling excitations built upon the rotational band in $^{163}$Lu, which is identified with a rotation of a triaxial, strongly deformed shape. We find that the presence of pairing correlations substantially affects the energy of the wobbling excitations. Our calculations predict an onset of a tilted rotation at a critical rotational frequency where the energy of the wobbling excitations approaches zero.

nucl-th↗

arXiv2004

Roto-vibrational spectrum and Wigner crystallization in two-electron parabolic quantum dots

We provide a quantitative determination of the crystallization onset for two electrons in a parabolic two-dimensional confinement. This system is shown to be well described by a roto-vibrational model, Wigner crystallization occurring when the rotational motion gets decoupled from the vibrational one. The Wigner molecule thus formed is characterized by its moment of inertia and by the corresponding sequence of rotational excited states. The role of a vertical magnetic field is also considered. Additional support to the analysis is given by the Hartree-Fock phase diagram for the ground state and by the random-phase approximation for the moment of inertia and vibron excitations.

cond-mat.mes-hall↗

arXiv2003

Symmetry breaking and the random-phase approximation in small quantum dots

The random-phase approximation has been used to compute the properties of parabolic two-dimensional quantum dots beyond the mean-field approximation. Special emphasis is put on the ground state correlation energy, the symmetry restoration and the role of the spurious modes within the random-phase approximation. A systematics with the Coulombic interaction strength is presented for the 2-electron dot, while for the 6- and 12-electron dots selected cases are discussed. The validity of the random-phase approximation is assessed by comparison with available exact results.

cond-mat.mes-hall↗

arXiv2001

Oscillations in the photocurrent from quantum dots: Geometric information from reciprocal spectra

We demonstrate that the current of photoelectrons from a quantum dot exhibits oscillations as a function of the photon energy owing to the predominant ionization from the dot boundary. In the Fourier reciprocal space of the photoelectron wave vector these oscillations reveal frequencies connected to the confinement range. We attribute the oscillation in the recent photocurrent measurements by Fry et al. (PRL 84, 733 (2000)) to this phenomenon. Angle-resolved and angle-integrated experiments with the focus on directly imaging the confining potential are suggested.

cond-mat.mes-hall↗

arXiv2000

Nonaxial octupole deformations in light N=Z nuclei at high spins

High spin states of ^{32}S$ and ^{56}Ni are investigated by means of the cranking Hartree-Fock method with the Gogny interaction without imposing a restriction on the axial reflection symmetry. It was found that a non-axial octupole deformation of the Y_{31} type becomes important in the yrast states of ^{32}S. A similar effect is predicted for the nucleus ^{56}Ni.

nucl-th↗

arXiv1995

Nuclear Shell Structure and Chaotic Dynamics in Hexadecapole Deformation

The effect of an axially symmetric hexadecapole term is investigated in a strongly deformed quadrupole potential. While the system is nonintegrable and shows significant chaotic behaviour classically, the quantum mechanical treatment not only produces a general smoothing effect with regard to chaos but even yields a pronounced shell structure at certain hexadecapole strength parameter values for oblate and prolate deformation.

nucl-th↗

arXiv1994

Shell Structures and Chaos in Deformed Nuclei and Large Metallic Clusters

A reflection-asymmetric deformed oscillator potential is analysed from the classical and quantum mechanical point of view. The connection between occurrence of shell structures and classical periodic orbits is studied using the ''removal of resonances method'' in a classical analysis. In this approximation, the effective single particle potential becomes separable and the frequencies of the classical trajectories are easily determined. It turns out that the winding numbers calculated in this way are in good agreement with the ones found from the corresponding quantum mechanical spectrum using the particle number dependence of the fluctuating part of the total energy. When the octupole term is switched on it is found that prolate shapes are stable against chaos whereas spherical and oblate cases become chaotic. An attempt is made to explain this difference in the quantum mechanical context by looking at the distribution of exceptional points which results from the matrix structure of the respective Hamiltonians. In a similar way we analyse the modified Nilsson model and discuss its consequences for nuclei and metallic clusters.

nucl-th↗

arXiv1994

Periodic Orbits and Shell Structure in Octupole Deformed Potentials

The effect of an octupole term in a quadrupole deformed single particle potential is studied from the classical and quantum mechanical view point. Whereas the problem is nonintegrable, the quantum mechanical spectrum nevertheless shows some shell structure in the superdeformed prolate case for particular, yet fairly large octupole strengths; for spherical or oblate deformation the shell structure disappears. This result is associated with classical periodic orbits which are found by employing the removal of resonances method; this approximation method allows determination of the shape of the orbit and of the approximate octupole coupling strength for which it occurs. The validity of the method is confirmed by solving numerically the classical equations of motion. The quantum mechanical shell structure is analysed using the particle number dependence of the fluctuating part of the total energy. In accordance with the classical result this dependence turns out to be very similar for a superdeformed prolate potential plus octupole term and a hyperdeformed prolate potential without octupole term. In this way the shell structure is explained at least for some few hundred levels. The Fourier transform of the level density further corroborates these findings.

nucl-th↗

arXiv1994

Chaos in Axially Symmetric Potentials with Octupole Deformation

Classical and quantum mechanical results are reported for the single particle motion in a harmonic oscillator potential which is characterized by a quadrupole deformation and an additional octupole deformation. The chaotic character of the motion is srongly dependent on the quadrupole deformation in that for a prolate deformation virtually no chaos is discernible while for the oblate case the motion shows strong chaos when the octupole term is turned on.

nucl-th↗