1,001 research outputs found
Torsion, Chern-Simons Term and Diffeomorphism Invariance
In the 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
Two-Well System under Large Amplitude Periodic Forcing: Stochastic Synchronization, Stochastic Resonance and Stability
We study the residence time distributions and explore the possibility of
observing stochastic resonance and synchonization of passages in a two-well
system driven by a periodic forcing of amplitude larger than a marginal value
beyond which one of the two wells become unstable and diasppear. We define and
calculate hysteresis loop in the system, the area of which measures the degree
of synchronization between the residence time statistics and the input signal,
as a function of input noise strength. We analyse the noise induced stability
obtained in such a deterministically overall unstable system and within this
context discuss the above two phenomena.Comment: Mod. Phys. Lett. B 1997, in print, figures available on reques
AC driven thermal ratchets
We consider the motion of a overdamped Brownian particle in periodic
asymmetric potential with space dependent friction coefficient. In the presence
of external time periodic forcing, the system shows multiple current reversals
on varying the amplitude of the external forcing and the temperature of the
thermal bath. In the adiabatic regime we find a single reversal of current as a
function of noise strength which can only be accounted due to the presence of
space dependent friction coefficient. For very large forcing term, the current
does not go to zero, instead it asymptotically tends to a limiting value
depending on the phase shift between the potential and the friction. This fact
plays an important role in obtaining multiple current reversals.Comment: 4 pages, latex/revtex, 4 eps figures. Proceedings of CMDAYS2K, held
at Guru Ghasidas University, Bilaspur, Chattisgarh, India, Aug 29-31, 2
Removals of heavy metals frombed sediment of Brahmani river
The presence of heavy metals in river water, which is regular in mechanical and urban ranges including mining commercial ventures, represents a destructive impact to human wellbeing and nature's domain. There is a high probability of pollution of both surface and river water because of the release of heavy metal polluted wastewater. Evacuation of such heavy metals has been an examination center to plan a productive medicine framework. Some late innovations that address this issue are prone to be extremely unreasonable. Anyway here we are attempting to evacuate these heavy metals specifically from river water. Before removals these heavy and harmful metals we are first determining the physical characteristics of the bed sediment for each site. This will give us the ideas about the differences in physical characteristics for the different sites of the same river as well as the particle sizes distributions in the bed sediment. Removals of heavy metals can be done using many methods. Many of those are very expensive. One of the simplest methods to remove these metals is Adsorption method. These metals can be directly adsorbed by using proper adsorbent. For different metals adsorbent may be different, but in some cases two or more metals can be adsorbed by same adsorbent. For different pH the efficiency of adsorption is different but we are removing these metals directly from river bed sediment, so all the experiment are done in natural pH
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
Mobility and stochastic resonance in spatially inhomogeneous system
The mobility of an overdamped particle, in a periodic potential tilted by a
constant external field and moving in a medium with periodic friction
coefficient is examined. When the potential and the friction coefficient have
the same periodicity but have a phase difference, the mobility shows many
interesting features as a function of the applied force, the temperature, etc.
The mobility shows stochastic resonance even for constant applied force, an
issue of much recent interest. The mobility also exhibits a resonance like
phenomenon as a function of the field strength and noise induced slowing down
of the particle in an appropriate parameter regime.Comment: 14 pages, 12 figures. Submitted to Phys. Rev.
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
- …