930 research outputs found
Theory of non-stationary activated rate processes : nonexponential relaxation kinetics
We have explored a simple microscopic model to simulate a thermally activated
rate process where the associated bath which comprises a set of relaxing modes
is not in an equilibrium state. The model captures some of the essential
features of non-Markovian Langevin dynamics with a fluctuating barrier. Making
use of the Fokker-Planck description we calculate the barrier dynamics in the
steady state and non-stationary regimes. The Kramers-Grote-Hynes reactive
frequency has been computed in closed form in the steady state to illustrate
the strong dependence of the dynamic coupling of the system with the relaxing
modes. The influence of nonequilibrium excitation of the bath modes and its
relaxation on the kinetics of activation of the system mode is demonstrated. We
derive the dressed time-dependent Kramers rate in the nonstationary regime in
closed analytical form which exhibits strong non-exponential relaxation
kinetics of the reaction co-ordinate. The feature can be identified as a
typical non-Markovian dynamical effect.Comment: Plain Latex, no figure, 31 pages, to appear in J. Chem. Phy
Lie algebraic noncommuting structures from reparametrisation symmetry
We extend our earlier work of revealing both space-space and space-time
noncommuting structures in various models in particle mechanics exhibiting
reparametrisation symmetry. We show explicitly (in contrast to the earlier
results in our paper \cite{sg}) that for some special choices of the
reparametrisation parameter , one can obtain space-space noncommuting
structures which are Lie-algebraic in form even in the case of the relativistic
free particle. The connection of these structures with the existing models in
the literature is also briefly discussed. Further, there exists some values of
for which the noncommutativity in the space-space sector can be made
to vanish. As a matter of internal consistency of our approach, we also study
the angular momentum algebra in details.Comment: 9 pages Latex, some references adde
Permittivity enhancement of aluminum oxide thin films with the addition of silver nanoparticles
doi:10.1063/1.2425010Multilayer reactive electron-beam evaporation of thin aluminum oxide layers with embedded silver nanoparticles (Ag-nps) has been used to create a dielectric thin film with an enhanced permittivity. The results show a frequency dependent increase of the dielectric constant κ. Overall stack κ of the control sample was found to be 7.7-7.4 in the 1 kHz-1 MHz range. This is in comparison with κ = 16.7-13.0 over the same frequency range in the sample with Ag-nps. Capacitance-voltage and conductance-voltage measurements indicate the presence of charge capture resulting from the Ag-nps. The authors attribute this dielectric constant enhancement to dipole and space charge polarization mechanisms.The authors thank M. Othman for ellipsometry measurements. They are also grateful for the funding provided by the National Science Foundation Grant No. ECS0223
Some fixed point theorems in partial metric spaces
Here we prove two fixed point theorems on partial metric space, which was defined by S. Matthews [8] in 1994. In the literature one can find fixed point theorems proved on such spaces by using Picard iteration schemes. Here our main ingredient is Cantor intersection type results.The first author is being supported by University Grants Commission’s (Regional office, Kolkata) Minor Research Project (letter no. F.PSW-032/11-12(ERO), dated 08.08.11) for this work.Publisher's Versio
Microscopic calculation of proton capture reactions in mass 60-80 region and its astrophysical implications
Microscopic optical potentials obtained by folding the DDM3Y interaction with
the densities from Relativistic Mean Field approach have been utilized to
evaluate S-factors of low-energy reactions in mass 60-80 region
and to compare with experiments. The Lagrangian density FSU Gold has been
employed. Astrophysical rates for important proton capture reactions have been
calculated to study the behaviour of rapid proton nucleosynthesis for waiting
point nuclei with mass less than A=80
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