Torsion, Chern-Simons Term and Diffeomorphism Invariance

In the $torsion \otimes curvature$ approach of gravity Chern-Simons modification has been considered here. It has been found that Chern-Simons contribution to the bianchi identity has become cancelled from that of the scalar field part. But "homogeneity and isotropy" consideration of present day cosmology is a consequence of the "strong equivalence principle" and vice-versa.Comment: 8 page

θ\theta-Term and Cosmological Constant from CJD Action

In the gravity without metric formalism of Capovilla, Jacobson and Dell, the topological $\theta$-term appears through a canonical transformation.The origin of this canonical transformation is probed here. It is shown here that when $\theta$-term appears cosmological $\lambda$-term also appears simultaneously.Comment: 5 page

Stochastic resonance and nonlinear response in a dissipative quantum two-state system

We study the dynamics of a dissipative two-level, system driven by a monochromatic ac field, starting from the usual spin-boson Hamiltonian. The quantum Langevin equations for the spin variables are obtained. The amplitude of the coherent oscillations in the average position of the particle is studied in the high temperature limit. The system exhibits quantum stochastic resonance in qualitative agreement with earlier numerical results.Comment: PRB April 1997, figures available on reques

Dirac spinors in Bianchi-I f(R)-cosmology with torsion

We study Dirac spinors in Bianchi type-I cosmological models, within the framework of torsional $f(R)$-gravity. We find four types of results: the resulting dynamic behavior of the universe depends on the particular choice of function $f(R)$; some $f(R)$ models do not isotropize and have no Einstein limit, so that they have no physical significance, whereas for other $f(R)$ models isotropization and Einsteinization occur, and so they are physically acceptable, suggesting that phenomenological arguments may select $f(R)$ models that are physically meaningful; the singularity problem can be avoided, due to the presence of torsion; the general conservation laws holding for $f(R)$-gravity with torsion ensure the preservation of the Hamiltonian constraint, so proving that the initial value problem is well-formulated for these models.Comment: 25 pages, 1 figur

Beyond the Horizon

Cosmic horizons arise in general relativity in the context of black holes and in certain cosmologies. Classically, regions beyond a horizon are inaccessible to causal observers. However, quantum mechanical correlations may exist across horizons that may influence local observations. For the case of de Sitter space, we show how a single particle excitation behind the horizon changes the density matrix governing local observables. As compared to the vacuum state, we calculate the change in the average energy and entropy per unit volume. This illustrates what may be a generic property allowing some features of spacetime beyond a horizon to be inferred.Comment: 9 pages, 1 figur

Phytochemical profiling and antioxidant activity of Leea macrophylla Roxb. ex Hornem.-in vitro study

Leea macrophylla Roxb. ex Hornem., a traditional medicinal plant reported remedies for diseases in rural India. However, proper justification and validation of their traditional practice are lacking. Hence this study was done to explore a comprehensive account of phytochemical profiling and antioxidant activities. The presence of phenols, tannins, alkaloids, saponins and flavonoinds was confirmed through phytochemical screening. After estimation of the phytochemical, we get 104.05 mg of GAE/g of phenol, 94.78 mg of GAE/g of tannins, 21.40 mg/g of alkaloids, 05.50 mg/g of saponins and 117.98 mg of QE/g of flavonoids. Its further analysis takes place through GC-MS, get 14 bioactive compounds, which have more than 1% peak area. They had already reported a good medication value in various remedies. The antioxidant test, through DPPH assay, shows, IC50 values of L. macrophylla is 51.31 µg/mL and gallic acid (taken as standard) have 39.91 µg/mL. By comparing with gallic acid, it can be concluded that Leea macrophylla also has a good antioxidant activity

Relation between Stochastic Resonance and Synchronization of Passages in a Double-Well System

We calculate, numerically, the residence times (and their distribution) of a Brownian particle in a two-well system under the action of a periodic, saw-tooth type, external field. We define hysteresis in the system. The hysteresis loop area is shown to be a good measure of synchronization of passages from one well to the other. We establish connection between this stochastic synchronization and stochastic resonance in the system.Comment: To appear in PRE May 1997, figures available on reques

Optical Upconversion Properties Of Tm2O3 / Yb2O3 Doped Lead Tellurite Glasses

The melt-quench process was used to create the lead-tellurite glasses codoped with lanthanides as thulium and ytterbium. Thermal characterization carried by differential scanning calorimetry. X-ray diffraction is studies to get the nature of sold sample. The UV-Visible-IR absorption spectra was carried in range of 300 nm to 1100 nm. There were four unique absorption peaks on the glass thulium –ytterbium doped glass. The frequency up-conversion (UC) fluorescence has been seen at room temperature by 975 nm excitation

Dispersionless motion in a driven periodic potential

Recently, dispersionless (coherent) motion of (noninteracting) massive Brownian particles, at intermediate time scales, was reported in a sinusoidal potential with a constant tilt. The coherent motion persists for a finite length of time before the motion becomes diffusive. We show that such coherent motion can be obtained repeatedly by applying an external zero-mean square-wave drive of appropriate period and amplitude, instead of a constant tilt. Thus, the cumulative duration of coherent motion of particles is prolonged. Moreover, by taking an appropriate combination of periods of the external field, one can postpone the beginning of the coherent motion and can even have coherent motion at a lower value of position dispersion than in the constant tilt case.Comment: 4 pages, 4 figure

Pregnancy and COVID-19: Lessons so far

Since COVID-19 is a new disease, we are still learning how it spreads, what the best prevention measures are and how it affects different groups of people including pregnant women (CDC 2020)