Narrow Results

This research focuses on studying the influence of the Hall current on the propagation and reflection of elastic waves in a non-local isotropic rotating solid. The dispersion relation is derived to determine the speed of propagation, revealing the presence of three coupled quasi-waves within the solid: coupled qP-wave, qT-wave and qSV-wave. The rotational motion and the Hall current introduce anisotropic characteristics to the medium, leading to the emergence of quasi-type waves. The rotation disrupts the isotropic nature of the solid, transforming it into an anisotropic medium. Consequently, the purely longitudinal and transverse waves are converted into quasi-longitudinal and quasi-transverse waves. The speed of the propagating waves is dependent on specific elastic parameters. By employing free boundary conditions, the mathematical calculation and graphical representation of wave amplitude ratios are determined. The influence of rotational frequency, non-locality, fractional order and Hall current parameters on the computed results is investigated. The conservation of energy validates the accuracy of the obtained results. Furthermore, it is observed that the previously reported results in the literature can be obtained as a special case when rotation and the Hall current are absent.

We implement Hartle's perturbation method to the computation of relativistic rigidly rotating neutron star models. The program has been written in SCILAB (© INRIA–ENPC), a matrix-oriented high-level programming language. The numerical method is described in very detail and is applied to many models in slow or fast rotation. We show that, although the method is perturbative, it gives accurate results for all practical purposes and it should prove an efficient tool for computing rapidly rotating pulsars.

We solve numerically in the complex plane all the differential equations involved in Hartle's perturbation method for computing general-relativistic polytropic models of rotating neutron stars. We give emphasis on computing quantities describing the geometry of models in rapid rotation. Compared to numerical results obtained by certain sophisticated iterative methods, we verify appreciable improvement of our results vs to those given by the classical Hartle's perturbative scheme.

We compute general-relativistic polytropic models of magnetized rotating neutron stars, assuming that magnetic field and rotation can be treated as decoupled perturbations acting on the nondistorted configuration. Concerning the magnetic field, we develop and apply a numerical method for solving the relativistic Grad–Shafranov equation as a nonhomogeneous Sturm–Liouville problem with nonstandard boundary conditions. We present significant geometrical and physical characteristics of six models, four of which are models of maximum mass. We find negative ellipticities owing to a magnetic field with both toroidal and poloidal components; thus the corresponding configurations have prolate shape. We also compute models of magnetized rotating neutron stars with almost spherical shape due to the counterbalancing of the rotational effect (tending to yield oblate configurations) and the magnetic effect (tending in turn to derive prolate configurations). In this work such models are simply called "equalizers." We emphasize on numerical results related to magnetars, i.e. ultramagnetized neutron stars with relatively long rotation periods.

The shapes of rotating drops of liquid bound by gravitation is a classical subject of study. Inspired by this classical theory, we have simulated numerically a related problem, the rotating rigid configurations of a finite number of point particles. Two particles at a distance $r$ have a long range attractive potential $-1∕r$ and a short range repulsive potential $1∕r^2$ preventing collapse. We take the angular momentum to be conserved, but not the energy.This system has a variable density, unlike the classical liquid drops. When the number of particles is small, it is more rigid than a liquid drop, implying that many different stable equilibrium configurations may exist with the same angular momentum but different energies. When the number of particles becomes large, our system should resemble a self-gravitating polytropic gas.We present here the results of a preliminary study with only 3, 4, and 5 particles. The methods used could be applied to the study of rotating molecules.

In order to simulate rigidly rotating polytropes, we have simulated systems of $N$ point particles, with $N$ up to 1800. Two particles at a distance $r$ interact by an attractive potential $-1∕r$ and a repulsive potential $1∕r^2$. The repulsion simulates the pressure in a polytropic gas of polytropic index $3∕2$. We take the total angular momentum $L$ to be conserved, but not the total energy $E$. The particles are stationary in the rotating coordinate system. The rotational energy is $L^2∕(2I)$ where $I$ is the moment of inertia. Configurations, where the energy $E$ has a local minimum, are stable. In the continuum limit $N\to \infty$, the particles become more and more tightly packed in a finite volume, with the interparticle distances decreasing as $N^{-1∕3}$. We argue that $N^{-1∕3}$ is a good parameter for describing the continuum limit. We argue further that the continuum limit is the polytropic gas of index $3∕2$. For example, the density profile of the nonrotating gas approaches that computed from the Lane–Emden equation describing the nonrotating polytropic gas. In the case of maximum rotation, the instability occurs by the loss of particles from the equator, which becomes a sharp edge, as predicted by Jeans in his study of rotating polytropes. We describe the minimum energy nonrotating configurations for a number of small values of $N$.

This paper focuses on studying thermal, elastic and coupled plasma waves, in the sense of a photo-thermal process transport within an infinite semiconductor medium. In order to study photo-thermal interactions in two-dimensional semiconducting materials, a new mathematical model based on the Moore–Gibson–Thompson equation (MGTE) is implemented. The MGTE model involving the Green–Naghdi model of type III as well as the heat transport equation proposed by Lord and Shulman. We consider the semi-conductor half-space is rotated at a uniform angular speed and magnetized. The analysis of the distribution of thermophysical fields has been extracted by a normal mode method, represented graphically and discussed. The results predicted by the new and improved model have been compared with the generalized and classic ones. In addition, all field quantities have been examined for effects of rotation, a lifetime of the photo-generated, and the applied magnetic field.

We elaborate two different methods for extracting from data the relative phase of two amplitudes of some sequential decays of baryons. We also relate this phase to a particular physical angle. Moreover, we suggest how to infer some time-reversal (TR) odd observables — in particular, asymmetries — from data. Last, we comment on the Standard Model (SM) predictions of such asymmetries, showing that most of the decays considered are quite suitable for revealing possible new physics (NP) contributions.

We study Dirac neutrinos propagating in rotating background matter. First we derive the Dirac equation for a single massive neutrino in the non-inertial frame, where matter is at rest. This equation is written in the effective curved spacetime corresponding to the co-rotating frame. We find the exact solution of the Dirac equation. The neutrino energy levels for ultrarelativistic particles are obtained. Then we discuss several neutrino mass eigenstates, with a nonzero mixing between them, interacting with rotating background matter. We derive the effective Schrödinger equation governing neutrino flavor oscillations in rotating matter. The new resonance condition for neutrino oscillations is obtained. We also examine the correction to the resonance condition caused by the matter rotation.

The rotation of astronomical objects may be of a cosmological origin due to the Universe's specific angular momentum estimates proving to exceed those for spiral galaxies. The problem is expected to be solved in the framework of quantum geometrodynamics.

The idea of a rank-one rotating mass matrix (R2M2) is reviewed detailing how it leads to ready explanations both for the fermion mass hierarchy and for the distinctive mixing patterns between up and down fermion states, which can be and have been tested against experiment and shown to be fully consistent with existing data. Further, R2M2 is seen to offer, as by-products: (i) a new solution to the strong CP problem in QCD by linking the theta-angle there to the Kobayashi–Maskawa CP-violating phase in the CKM matrix, and (ii) some novel predictions of possible anomalies in Higgs decay observable in principle at the LHC. A special effort is made to answer some questions raised.

We seek wormholes among rotating cylindrically symmetric configurations in general relativity. Exact wormhole solutions are presented with such sources of gravity as a massless scalar field, a cosmological constant, and a scalar field with an exponential potential. However, none of these solutions are asymptotically flat, which excludes the existence of wormhole entrances as local objects in our Universe. To overcome this difficulty, we try to build configurations with flat asymptotic regions using the cut-and-paste procedure: on both sides of the throat, a wormhole solution is matched to a properly chosen region of flat space-time at some surfaces ${\mathrm{\Sigma }}_{-}$ and ${\mathrm{\Sigma }}_{+}$. It is shown, however, that if the source of gravity in the throat region is a scalar field with an arbitrary potential, then one or both thin shells appearing on ${\mathrm{\Sigma }}_{-}$ and ${\mathrm{\Sigma }}_{+}$ inevitably violate the null energy condition. Thus, although rotating wormhole solutions are easily found without exotic matter, such matter is still necessary for obtaining asymptotic flatness.

Static and stationary cylindrically symmetric space-times in general relativity are considered, supported by distributions of cosmic strings stretched in the azimuthal ($\phi$), longitudinal ($z$) or radial ($x$) directions or and by pairs of mutually opposite radiation flows in any of these directions. For such systems, exact solutions are obtained and briefly discussed, except for radial strings (a stationary solution for them is not found); it is shown that static solutions with $z$- and $\phi$-directed radiation flows do not exist while for $z$-directed strings a solution is only possible with negative energy density. Almost all solutions under discussion contain singularities, and all stationary solutions have regions with closed timelike curves, hence, most probably, only their well-behaved regions admit application to real physical situations.

We analyze the relativistic quantum effects induced by the topology associated with a time-dislocation space–time and produced by the angular velocity associated with a rotating reference frame, on a scalar field. The parameters related to the torsion of the dislocation and to the angular velocity of the rotating reference frame impose lower and upper limits of the radial coordinate. At these limiting values of the radial coordinate, boundary conditions are assumed, in order to determine the energy levels. We show that in this scenario, two interesting physical phenomena arise, namely, the Sagnac-like and the Aharonov–Bohm-like effects.

We review the topic of quantized vortices in multicomponent Bose–Einstein condensates of dilute atomic gases, with an emphasis on the two-component condensates. First, we review the fundamental structure, stability and dynamics of a single vortex state in a slowly rotating two-component condensates. To understand recent experimental results, we use the coupled Gross–Pitaevskii equations and the generalized nonlinear sigma model. An axisymmetric vortex state, which was observed by the JILA group, can be regarded as a topologically trivial skyrmion in the pseudospin representation. The internal, coherent coupling between the two components breaks the axisymmetry of the vortex state, resulting in a stable vortex molecule (a meron pair). We also mention unconventional vortex states and monopole excitations in a spin-1 Bose–Einstein condensate. Next, we discuss a rich variety of vortex states realized in rapidly rotating two-component Bose–Einstein condensates. We introduce a phase diagram with axes of rotation frequency and the intercomponent coupling strength. This phase diagram reveals unconventional vortex states such as a square lattice, a double-core lattice, vortex stripes and vortex sheets, all of which are in an experimentally accessible parameter regime. The coherent coupling leads to an effective attractive interaction between two components, providing not only a promising candidate to tune the intercomponent interaction to study the rich vortex phases but also a new regime to explore vortex states consisting of vortex molecules characterized by anisotropic vorticity. A recent experiment by the JILA group vindicated the formation of a square vortex lattice in this system.

The idea of spontaneous symmetry breaking in many-body physics from personal perspective (Bose-gas, nuclear structure and a new approach of Generalized Density Matrix).

In the present paper, we have studied the propagation of axial symmetric cylindrical surface waves through rotating cylindrical bore in a micropolar porous medium of infinite extent possessing cubic symmetry. The frequency equation for surface wave propagation in the micropolar porous medium has been derived and liquid filled bore are derived. The effect of the rotation on phase velocity of surface wave has been studied in detail. Radius of bore and other material parameters for empty and liquid filled bore are derived. A particular case of interest has been deduced. Numerical results have been obtained and illustrated graphically to understand the behavior of phase velocity versus wave number of a wave. The results have indicated that the effect of rotation on phase velocity is highly pronounced. Comparisons are made in the absence of rotation.

This paper examines the effect of rotation on thermal instability under Hele-Shaw cell saturated by Casson nanofluid using both linear and nonlinear ways. The nanofluid model incorporates Brownian and thermophoresis diffusion. While conducting an analysis of nonlinear stability numerically using the truncated Fourier series method, analysis of linear stability is performed analytically using the normal mode methodology. The outcomes are all displayed graphically. The results demonstrate that the rotation has dual effect on Hele-Shaw parameter as well as Casson parameter, for higher value of rotation it has destabilizing effect and it stabilizing  the system for lower values of rotation. Lewis number and concentration Rayleigh number promote the onset of convective motion within the system. On the other hand, rotation stabilize the system. Understanding the behavior of heat and mass transportation, the concentration of nanoparticles and fluid phase, utilize the Nusselt number when Nusselt numbers are assessed as a function of time, it is found that the variation of the rotation, Hele-Shaw and Casson parameter has a major influence on the heat and mass transfer. Both steady and unsteady weakly nonlinear analyses are performed to understand the heat transport in the system. It is concluded that the Casson nanofluid parameter has both stabilizing and destabilizing impact depending upon the rate of rotation and therefore this work can be possibly utilized in both places, where heat removal and heat conservation are required.

The applications of swirling interfaces with heat and mass transfer are diverse and impactful, spanning industries from energy and manufacturing to healthcare and environmental protection. This study focuses on the stability of such interfaces where a viscous fluid interacts with a Rivlin–Ericksen (RE) viscoelastic fluid, undergoing heat and mass transfer. In this paper, the fluids are enclosed between two cylinders, one stationary and the other rotating. Mathematical equations are solved using potential flow theory. The interface stability is assessed using a normal mode procedure, leading to a second-order polynomial equation. The study finds that swirling flow reduces perturbation amplification, especially when heat and mass transfer occur simultaneously. However, the viscoelastic nature of the Rivlin–Ericksen fluid destabilizes the interface. Overall, this research provides valuable insights into complex fluid behavior with applications across industries.

This paper analyzes the thermoelastic dynamic behavior of simply supported viscoelastic nanobeams of fractional derivative type due to a dynamic strength load. The viscoelastic Kelvin–Voigt model with fractional derivative with Bernoulli–Euler beam theory is introduced. The generalized thermoelastic heat conduction model with a two-phase lag is also used. It is assumed that the beam is rotating at a uniform angular velocity and that the thermal conductivity varies linearly depending on the temperature. Due to a variable harmonic heat and retreating time-dependent load, the nanobeam is excited. The Laplace integral transformation technique is used as the solution method. The thermodynamic temperature, deflection function, bending moment, and displacement are numerically calculated. Results of fractional and integer viscoelastic material models are compared. In the studied system, the effect of the nonlocal parameter, viscosity and varying load on the solutions is shown, and the temperature-dependence of the thermal conductivity is analyzed.