8,460 research outputs found
Optimal Control of Quantum Dynamics : A New Theoretical Approach
A New theoretical formalism for the optimal quantum control has been
presented. The approach stems from the consideration of describing the
time-dependent quantum system in terms of the real physical observables, viz.,
the probability density rho(x,t) and the quantum current j(x,t) which is well
documented in the Bohm's hydrodynamical formulation of quantum mechanics. The
approach has been applied for manipulating the vibrational motion of HBr in its
ground electronic state under an external electric field.Comment: 4 figure
Snow cover, snowmelt and runoff in the Himalayan River basins
Not withstanding the seasonal vagaries of both rainfall amount and snowcover extent, the Himalayan rivers retain their basic perennial character. However, it is the component of snowmelt yield that accounts for some 60 to 70 percent of the total annual flow volumes from Hamilayan watersheds. On this large hydropotential predominantly depends the temporal performance of hydropower generation and major irrigation projects. The large scale effects of Himalayan snowcover on the hydrologic responses of a few selected catchments in western Himalayas was studied. The antecedent effects of snowcover area on long and short term meltwater yields can best be analyzed by developing appropriate hydrologic models forecasting the pattern of snowmelt as a function of variations in snowcover area. It is hoped that these models would be of practical value in the management of water resources. The predictability of meltwater for the entire snowmelt season was studied, as was the concurrent flow variation in adjacent watersheds, and their hydrologic significance. And the applicability of the Snowmelt-Runoff Model for real time forecast of daily discharges during the major part of the snowmelt season is examined
Thermodynamic Geometry of the Born-Infeld-anti-de Sitter black holes
Thermodynamic geometry is applied to the Born-Infeld-anti-de Sitter black
hole (BIAdS) in the four dimensions, which is a nonlinear generalization of the
Reissner-Norstr\"Aom-AdS black hole (RNAdS). We compute the Weinhold as well as
the Ruppeiner scalar curvature and find that the singular points are not the
same with the ones obtained using the heat capacity. Legendre-invariant metric
proposed by Quevedo and the metric obtained by using the free energy as the
thermodynamic potential are obtained and the corresponding scalar curvatures
diverge at the Davies points.Comment: Latex,19 pages,14 figure
Giant magneto-impedance in Ag-doped La0.7Sr0.3MnO3
The resistive and reactive parts of the magneto-impedance of sintered
ferromagnetic samples of La0.7Sr0.3-xAgxMnO3 (x = 0.05, 0.25) have been
measured at room temperature (<Tc) over frequency interval 1KHz to 15MHz and in
presence of magnetic field up to 4KOe. The field dependence of relative change
in resistance is small in KHz region but increases strongly for higher
frequency of excitation. The maximum value of relative change in resistance at
H =4KOe was found to be around 70% at 15MHz frequency.On the contrary the
corresponding change in reactance has less frequency sensitivity and the
maximum occurs at 1MHz frequency. The magneto-impedance is negative for all
frequencies. The 'normalized magneto-impedance' as defined by
[Z(H)-Z(0)]/[Z(0)-Z(4K)] when plotted against scaled field H/H1/2 is found to
be frequency independent ; H1/2 is the field where 'normalized
magneto-impedance' is reduced to half its maximum. A phenomenological formula
for magneto-impedance Z (H) in ferromagnetic material is proposed based on Pade
approximant. The formula for Z (H) predicts the scaled behavior of 'normalized
magneto-impedance'.Comment: 26 pages,9 figure
Coherent Optimal Control of Multiphoton Molecular Excitation
We give a framework for molecular multiphoton excitation process induced by
an optimally designed electric field. The molecule is initially prepared in a
coherent superposition state of two of its eigenfunctions. The relative phase
of the two superposed eigenfunctions has been shown to control the optimally
designed electric field which triggers the multiphoton excitation in the
molecule. This brings forth flexibility in desiging the optimal field in the
laboratory by suitably tuning the molecular phase and hence by choosing the
most favorable interfering routes that the system follows to reach the target.
We follow the quantum fluid dynamical formulation for desiging the electric
field with application to HBr molecule.Comment: 5 figure
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