Pramana最新文献

This paper explores the statistical measure features of digital phase transfer among multilevel atoms, such as alkali metals with hyperfine structures. The excitation fields constitute a train of probe pulses and a single drive field. We have provided two schemes for the mechanism of excitation dynamics. In the first scheme, the pulses are frequency swept across the upper hyperfine splitting of the excited atomic states. In the second scheme, the pulses are tuned to the upper hyperfine level with a high angular momentum, allowing strong absorption of pulses. The phases of the propagating pulses are rectangular shapes with well-separated boundaries, especially in the second scheme. We address the notion of phase entropy to study the influence of sweeping on the statistics of the generated phases and select definite phases with desired features. The estimated phase entropy exposes local maximum entropy and minimum entropy. In the second scheme, we have extended the pulses in time. Therefore, the phase distributions are rich. The features of the digital distributions of rectangular phases have not been obtained manually. We have addressed math criteria to distinguish the digital phase’s features across propagation. Randomness tests and randomness generation have been evaluated on the time-dependent discrete phase sequences. We expect the proposed generation and transmission of randomised discrete phases to be used in quantum applications.

Compound nucleus (CN) formation probability ((P_{textrm{CN}})) is essential for synthesising superheavy elements (SHEs), understanding nuclear reactions, predicting reaction outcomes and designing efficient experiments. High (P_{textrm{CN}}) indicates a greater likelihood of successful fusion, aiding in the study of nuclear stability and structure. An empirical formula for (P_{textrm{CN}}) has been proposed, incorporating new parameters such as effective fissility ((chi _{textrm{eff}})) and zeta parameter ((zeta )), along with excitation energy and fusion barrier height. The fitted function shows greater systematic behaviour for ((E^*-V_B)chi _{textrm{eff}}) and (zeta ^{0.02}). (P_{textrm{CN}}) values obtained align well with the experimental data, predicting outcomes for both successful and unsuccessful fusion reactions. Notably, larger (P_{textrm{CN}}) values are seen for (phantom {a}^{45}hbox {Sc}{+}^{249}hbox {Cf}) and (phantom {a}^{50}hbox {Ti}{+}^{249}hbox {Bk}) for (Z=119) and 120, respectively. Analysis identifies (phantom {a}^{80}hbox {Se}{+}^{210}hbox {At}) and (phantom {a}^{55}hbox {Mn}{+}^{241}hbox {Pu}) as potential reactions for synthesising the SHE ((Z=119)), with Mn projectiles showing higher (P_{textrm{CN}}) than Se projectiles due to lower (zeta ) and deformation effects. Hence, (phantom {a}^{55}hbox {Mn}{+}^{241}hbox {Pu}) is more promising than (phantom {a}^{80}hbox {Se}{+}^{210}hbox {At}) for this purpose. The present work is useful for focussing experimental efforts and increasing the efficiency of SHE research by focussing on reactions with higher CN formation probability.

The dynamical solutions of two quantised harmonic modes coupled through the angular momentum are used to study the photon antibunching (PA) and the amplitude squared squeezing (ASS) of the input coherent radiation field interacting with the said coupled two oscillators. The analytical closed-form expressions for the PA and the ASS are exhibited. The complicated nature of the exact analytical solutions are on the way of extracting good physics. Therefore, the parametric estimates for the ASS and the PA are exhibited. A small algebra shows that the coupling parameter is of two parts. One of the two parts is responsible for the quantum optical properties of the input radiation field. Interestingly, the PA is obtained even when both the harmonic modes are in vacuum. It substantiates the fact that the coupling parameter induces nonlinearity and hence the photons are generated out of the vacuum. The data chosen for the symbolic calculations are theoretical in nature. Of course, these data are quite consistent with those of the theoretical developments. Apart from the academic interests of the present investigation, it is possible to plan a real experiment to verify the analytical results.

A complex negative-order Ablowitz–Kaup–Newell–Segur (AKNS) equation, which has potential utility in characterising the propagation of femtosecond pulses through erbium-doped fibre, is studied in this paper. The complex negative order AKNS equation’s ((n, N-n))-fold extended Darboux transformation (DT) is established by considering its recognised (2times 2) matrix Lax pair. The equation’s soliton and breather solutions can be obtained by utilising the resulting DT. By asymptotic analysis, we are able to illustrate and discuss the soliton’s elastic interaction graphically and to analyse some significant dynamic features, such as wave velocity, amplitude and energy. Meanwhile we also study the rogue wave and mixed breather-rogue wave interaction solutions. Finally, the numerical simulations of one- and two-soliton solutions are performed to analyse their dynamical structures. The implications and characteristics discussed in this work can be useful in understanding the propagation of optical pulses.

This study offers an analysis of the gravity-driven thermally stratified laminar nanoliquid flow past a permeable stretching surface with vanishing flux of nanoparticles. Two-phase fluid model is used for the nanofluids. By the application of similarity transformations, the partial differential equations (PDEs) that govern the problem are converted to ordinary differential equations (ODEs) which are extremely nonlinear. By using the shooting technique and Runge–Kutta (R–K) method, those equations are numerically solved. Shear stress at the surface and rate of surface mass transfer decrease but rate of heat transport at the surface rises for the enhancement of mass transpiration parameter. Temperature and concentration of the nanofluid are found to fall, but the liquid’s velocity rises with the rising buoyancy parameter. Concentration of the nanofluid increases but velocity of the liquid and temperature diminish when the thermal stratification parameter increases.

The exact solution for the Einstein–Maxwell field equations is generated. The quadratic equation of state together with the Karmarkar condition are used to investigate the structure and properties of the relativistic stars. The Karmarkar condition provides the relationship between the two gravitational potentials. The process of combining the Karmarkar condition and an EoS has currently led to new realistic solutions. In generating the model, one of the gravitational potentials is specified on physical grounds. The generated model undergoes several physical tests to determine its validity and acceptability. Several realistic physical conditions are found to be satisfied. The model stability regarding the adiabatic index and equilibrium of the physical forces is satisfied. The mass–radius relationship and surface red-shift both increase monotonically and are within the acceptable range of a realistic model. Their parameter values are found to be compatible with observations. The gravitational potentials are continuous throughout the star’s interior, and the model’s energy conditions are also satisfied.

Non-Newtonian materials are suggested as lubricants to maintain the high performances of various mechanical and industrial processes. Viscoelastic fluids as lubricants improve the mechanical and thermal processes. The objective of the current analysis is to highlight the significance of power-law viscoelastic lubricant in the flow of Walters B nanofluid in a moving frame. The role of higher-order slip as an interfacial constraint is studied for the lubrication phenomenon. Walters B nanofluid flow is a stagnation point flow. The Buongiorno nanofluid model is used to study the Brownian motion and thermophoresis size-dependent effects. The analysis is further updated by incorporating the bioconvective phenomenon with suspension of microbes. After modelling the problem successfully, it is shown that problem involved higher-order velocity slip conditions for which numerical computations cannot be performed. In order to treat such problems, an updated semi-analytical scheme called the hybrid homotopy analysis method (HHAM) is employed. Key focus is on the physical aspect of parameters. Current results have applications in polymers, lubrications, thermal systems, chemical processes, extrusion systems, etc.

The (2 + 1)-dimensional Sawada–Kotera–Kadomtsev Petviashvili equation (SKKPe) is explored in this work. Wielding the Hopf–Cole transform, its Hirota bilinear form is developed. Then, the lump wave solutions of the bright-type and dark-type, and the breather wave solutions of the sin–cosh type are extracted by applying the Hirota bilinear method with symbolic computation by taking different test functions. Additionally, abundant travelling wave solutions like the bright wave, periodic wave and singular wave solutions are investigated by employing three effective approaches, namely the extend Wang’s direct mapping method II (EWDMM), Bernoulli sub-equation function method (BSEFM) and Kudryashov method (KM). The nonlinear physical characteristics of the attained solutions are displayed graphically using the 3D and 2D plots. To the best of the author's knowledge, the results presented in the article are entirely new and have not been presented elsewhere, which can augment the exact solutions of the considered equation and allow us to study its nonlinear dynamics better.

The Rossby mode (r-mode) perturbation in pulsars as a steady gravitational wave source has been explored. The effect of a rigid crust on viscous damping and dissipation rate in the boundary layer between the fluid core and the crust has been studied. The intensity of the emitted GWs in terms of the strain tensor amplitude has been estimated with the approximation of slow rotation using equation of state derived from the APR and Skyrme effective interactions with Brussels–Montreal parameter sets. The core of the neutron star has been considered to be (beta )-equilibrated nuclear matter containing neutrons, protons, electrons and muons, surrounded by a solid crust. Calculations have been made for critical frequencies, time evolution and rate of change of the spin frequencies across a broad spectrum of pulsar masses.