Violation of Universal Lower Bound for the Shear Viscosity to Entropy Density Ratio in Dark Energy Dominated Accretion

The universal lower bound of the ratio of shear viscosity to entropy density is suggested by the string theory and gauge duality for any matter. We examined the ratio of shear viscosity to entropy density for viscous accretion flow towards a central gravitating object in the presence of dark energy. The ratio appears close to the universal lower bound for certain optically thin, hot accretion flows as they are embedded by strong magnetic field. Dark energy is a kind of exotic matter which has negative pressure. So dark energy creates repulsive force between the accreting particles, which indicates that shear viscosity of the flow becomes very low. Dark energy as accreting fluid has very high entropy density. The ratio should reach near to the lowest value for dark energy accretion. We wish to study what happens to the shear viscosity to entropy density ratio for viscous dark energy accretion flow.Comment: 9 pages, 12 figure

Fate of an Accretion Disc around a Black Hole when both the Viscosity and Dark Energy is Effecting

This paper deals with the viscous accretion flow of modified Chaplygin gas towards a black hole as the central gravitating object. Modified Chaplygin gas is a particular type of dark energy model which mimics of radiation era to phantom era depending on the different values of its parameters. We compare the drak energy accretion with the flow of adiabatic gas. An accretion disc flow around a black hole is an example of a transonic flow. To make the model, we consider three components of Navier Stokes' equation, the equation of continuity and the modified Chaplygin gas's equation of state. As a transonic flow passes through the sonic point, the velocity gradient being apparently singular there, gives rise to two flow branches : one infalling, the accretion and the other outgoing, the wind. We show that the wind curve is stronger and wind speed reaches to that of light at a finite distance from the black hole when dark energy is considered. Besides, if we increase the viscosity, accretion disc is being shortened. This two process acting together deviates much from adiabatic accretion case. It shows a weakening process for the accretion procedure by the works of viscous system influenced angular momentum transport and the repulsive force of the modified Chaplygin gas together.Comment: 12 pages, 18 figure

Zitterbewegung of a heavy hole in presence of spin-orbit interactions

We study the $zitterbewegung$ of a heavy hole in presence of both cubic Rashba and cubic Dresselhaus spin-orbit interactions. On contrary to the electronic case, $zitterbewegung$ does not vanish for equal strength of Rashba and Dresselhaus spin-orbit interaction. This non-vanishing of $zitterbewegung$ is associated with the Berry phase. Due to the presence of the spin-orbit coupling the spin associated with the heavy hole precesses about an effective magnetic field. This spin precession produces a transverse spin-orbit force which also generates an electric voltage associated with $zitterbewegung$. We have estimated the magnitude of this voltage for a possible experimental detection of $zitterbewegung$.Comment: 6 pages, 3 figure

Embedding Ultra slow-roll in Warm Inflation

Slow-roll of the inflaton field defines the standard dynamics of the inflationary epoch. However, the inflationary system deviates from slow-roll when it encounters an extremely flat region of the inflaton potential, and enters a phase dubbed Ultra slow roll. In this article, we explore the possibility of realizing an Ultra slow-roll phase in a particularly interesting inflationary scenario, called Warm Inflation. In the Warm inflationary scenario a thermalized, sub-dominant radiation bath coexists with the inflaton energy density as an effect of dissipative dynamics. We show in this article that though the background dynamics indicate Ultra slow-roll when the potential becomes extremely flat, in Warm Inflation models, where the dissipation coefficient is a sole function of the temperature of the radiation bath, the system fails to maintain the thermal equilibrium as soon as it enters the Ultra slow-roll phase. As thermal equilibrium is a key feature of Warm Inflation, and as it is not yet known how to deal with Warm Inflation without thermal equilibrium, we could not analyze such systems any further in this article. However, we demonstrate that brief periods of Ultra slow-roll phase, which smoothly ends into standard slow-roll, can be accommodated in WI models where the dissipation coefficient is not only a function of the temperature of the radiation bath but also depends on the amplitude of the inflaton field. We theoretically determine the criteria of successfully embedding Ultra slow-roll in WI while the system remain in thermal equilibrium, and also demonstrate numerically that such short Ultra slow-roll phases can indeed be embedded in specific Warm Inflation models which comply with the theoretically determined criteria.Comment: 10 pages, double column, 10 figure

Impact of Physical Education Curriculum on Academic Achievement of Higher Secondary School Students in India

In the present study, the researchers were mainly interested in investigating the impact of PE curriculum on the academic achievements of the Higher Secondary (HS) level (10+2) students belonging to two different educational boards in India i.e., West Bengal Council of Higher Secondary Education (WBCHSE) and Central Board of Secondary Education (CBSE). On the basis of simple randomization, one hundred eighty (N=180) HS level boys were selected from four schools (two schools from each board) as participants for the present study. Among 180 students, 120 students [60 from each educational board, WBCHSE acted as experimental Group-I (EGWB–I); CBSE acted as experimental Group-II (EGCB–II)] were so selected that they had PE as a compulsory subject and rest, 60 students [30 from each educational board, simultaneously acted as Control Group (CGWB+CB)] had either computer science or painting as a compulsory subject in place of PE. The students of EGWB–I & EGCB–II underwent two different PE curriculums as training interventions over an academic year (11 months). But the CGWB+CB did not receive any PE curriculum as a training intervention. The student’s academic achievement was measured by obtained marks in two common subjects (Bengali and English) for both boards. It was standardized through T-score and finally, composite T-score were calculated for all the subjects to draw statistical inference on academic achievement. Statistical inference on academic achievement among the groups in baseline and post-test were drawn through ANCOVA followed by Tukey's LSD post-hoc test. Significance was tested at p<.05 level. Both EGWB–I & EGCB–II showed a significant difference compared to the CGWB+CB in academic achievement. But no significant difference was observed between EGWB–I & EGCB–II. The academic achievement of the students having PE as a subject improved significantly compared to the students having no PE as a compulsory subject in both boards. But the PE curriculum in both boards was found to be equally effective for developing students' academic achievement

C(naphthyl)-H Bond Activation by Rhodium: Isolation, Characterization and TD-DFT Study of the Cyclometallates

The C1(naphthyl)-H, C2(naphthyl)-H, C3(naphthyl)-H and C8(naphthyl)-H bonds of the naphthyl group present in a group of naphthylazo-2\u27-hydroxyarenes (H 2L) have been activated by [Rh(PPh 3) 3Cl] in a toluene medium. Here the cyclometallation is accompanied by metal centered oxidation [Rh(i)?Rh(iii)]. All the resulting cyclometallates [Rh(PPh 3) 2(L)Cl] (2-5) have been isolated in a pure form. The characterization of the cyclometallates [Rh(PPh 3) 2(L)Cl] have been done on the basis of spectral (IR, UV-vis, and FAB mass) data. The structures of the representative cyclometallates 2a, 3a, 4a, 4b and 5b have been determined by X-ray diffraction. In all the cyclometallates, rhodium(iii) is coordinated to naphthylazo-2\u27-hydroxyarenes via terdentate C(naphthyl), N(diazene), O(phenolato/ naphtholato) donor centers & one chloride ion in a plane along with two axial trans PPh 3 molecules. Intermolecular association in the solid state is observed due to C-H...p and p...p interactions. Compounds show an oxidative response within 0.93 to 1.11 V (vs. SCE) and a reductive response at ~ -1.0 V (vs. SCE). Both the responses are based on the coordinated diazene function and are irreversible in nature, indicating limited stability of the oxidized and reduced species. The electronic structures of selected cyclometallates have been calculated using a TD-DFT model and the simulated spectra are consistent with the observed spectra of those cyclometallates

Schottky Barrier MOSFET Enabled Ultra-Low Power Real-Time Neuron for Neuromorphic Computing

Energy-efficient real-time synapses and neurons are essential to enable large-scale neuromorphic computing. In this paper, we propose and demonstrate the Schottky-Barrier MOSFET-based ultra-low power voltage-controlled current source to enable real-time neurons for neuromorphic computing. Schottky-Barrier MOSFET is fabricated on a Silicon-on-insulator platform with polycrystalline Silicon as the channel and Nickel/Platinum as the source/drain. The Poly-Si and Nickel make the back-to-back Schottky junction enabling ultra-low ON current required for energy-efficient neurons