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The problem considered is the fitting of a many-body interaction potential to bulk crystal data. A parameterisation of the potential is assumed which is based on physical considerations. The free parameters are determined by using global optimization to perform a least squares fit, to a large number of crystal properties. This has been achieved for body centered cubic (bcc) materials. The approach...
The R-matrix method is used to calculate the total photoionization cross-sections from the ground 2s22p61Se and the first three excited 2s22p53p3,1Se states of Al IV, for photon energies ranging from the first ionization threshold to just above the second threshold of the residual ion Al V. The two lowest LS terms of Al V − 2s22p52P0, 2s2p62Se, 2s2p62Se, represented by sophisticated...
The mass attenuation coefficient (μm) of 662 keV gamma rays have been measured in the extended media of bakelite and perspex under different collimation conditions. The increase in attenuation coefficient is seen with increase in sample thickness as well as with collimator size due to the contribution of multiple scattered photons in the uncollided beam of 662 keV gamma rays.
Energy spectrum of ejected electrons in ionization of hydrogen atoms has been calculated following a multiple scattering theory of Das and Seal [15]. The results show peaks around two to three Rydbergs of energies of the ejected electrons, for incident electron energy of 250 eV and 500 eV, considered here, and for different combinations of the angular variables of the scattered and the ejected electrons,...
The spectra of the isotopes of xenon are analysed from the point of view of O(6) symmetry breaking. It is pointed out that the excitation energies of the states 0 3+ can be used in detecting breaking of the symmetry. The nature of symmetry breaking in 118Xe and 120Xe is indicated.
Transfer reactions 56Fe(12C, xN) have been investigated. Angular distributions of particles following elastic scattering, one neutron and one proton transfer reaction channels leading to low lying states in respective residual nuclei have been measured. These are analysed using the coupled reaction channel (CRC) formalism. Starting with a double folded real potential, the elastic scattering angular...
Effect of laser pulse in suppressing the dissociation of a molecule is shown. The time dependent Schrödinger is solved numerically for a molecule in an intense laser pulse whose uppermost state is connected to continuum.
The ground state microwave rotational spectrum of the C-gauche conformer of allyl isothiocyanate has been reinvestigated by extending the frequency range up to 37.0 GHz. A detailed centrifugal distortion analysis has been carried out with previously reported and newly assigned microwave rotational transition frequencies. The evaluated rotational and centrifugal distortion constants are presented.
Biswas and Soni [4] have surmised a semiclassical formula for Berry’s phase in terms of a generating function. We derive this formula apart from showing that it is not true in general and investigate its domain of validity. We also derive transformation formulae for Berry’s phase (Hannay’s angle) under general canonical transformations. A simpler proof for total angle invariance than hitherto available,...
Infrared-to-visible wave-length conversion in the Yb3+−Er3+ doped phosphors system has been described by a simple three level model based on two ions mechanism. The excitation in the range of 900–1000 nm of an IR-photon is first absorbed by Yb3+ ion as a sensitizer attributed to the resonant energy transition in Er3+ ion from 4I3/2 → 4S15/2 and 1F9/2 → 4I15/2, respectively for green and red...
Fokker-Planck type equations have been classified according to the groups of contact transformations to which they belong. It has been found that there are only five classes as in the case of groups of point transformations. We have also obtained the algebraic structures of the corresponding Lie algebras. However, there are isomorphies in their group properties. The corresponding basis sets of functionally...
The linear amplifier with the superposition of displaced Fock states (DFS’s) as an input field is discussed. The s-parameterized characteristic function (CF) of linear amplifier for the superposition of two DFS’s is considered. Several quantum statistical expectation values for the output of linear amplifier are evaluated once the time dependent CF has been computed. The Glauber secondorder coherence...
We obtain exact cosmological solutions of a higher derivative theory described by the Lagrangian L=R+2αR2 in the presence of interacting scalar field. The interacting scalar field potential required for a known evolution of the FRW universe in the framework of the theory is obtained using a technique different from the usual approach to solve the Einstein field equations. We follow here a technique...
Characteristic features of photoconductivity in AsxSb15Se85−x and AsxSb10Se90−x bulk glass systems have been measured and reported. Both a.c and d.c techniques have been employed for the measurements. The temperature dependence of photoconductivity has been analysed in terms of the ABFH model and both systems are found to exhibit type I photoconductivity. Photoconductivity shows a clear change...
In the Starobinsky inflationary model inflation is driven by quantum corrections to the vacuum Einstein equation. We reduce the Wheeler-DeWitt equation corresponding to the Starobinsky model to a Schrödinger form containing time. The Schrödinger equation is solved with a Gaussian ansatz. Using the prescription for the normalization constant of the wave function given in our previous work, we show...
In this review, we discuss various cosmological issues related to our Universe from a string theoretic perspective. We analyse the pre-big bang cosmological scenario which appears naturally in this context due to the existence of scale factor duality symmetry in string theory. We then discuss some of the attractive and problematic features of this scenario. Finally, we introduce a method which is...
In re-ionized models, the measurement of polarization of CMBR can be a good criterion to narrow down the parameter space for cosmological models. A Vishniac-type effect in second order polarization over arc minute scales has been calculated. It has been shown that while the effect is very small (∼10−2µK) for CDM models, it can be significant (∼0.3µK) for some isocurvature models.
We consider the geometrical properties of a distribution of matter evolving under gravitational clustering. Such a distribution can be studied using standard statistical indicators such as the correlation function as well as geometrical descriptors sensitive to ‘connectedness’ such as percolation analysis and Minkowski functionals. Applying these methods to N-body simulations and galaxy catalogues...
We have tried to understand the recent observations related to metallicity in Ly-α forest clouds in the framework of the two component model. The model consists of mini-halos having circular velocities smaller than ∼ 55 km s−1, with no star formation and galactic halos with higher circular velocities ≤ 250 km s−1, having clouds, star formation and consequent metal enrichment. We find that even if...
We have carried out a multi-fractal analysis of the distribution of galaxies in the three Northern slices of the Las Campanas redshift survey. In this analysis we have studied the scaling properties of the distribution of galaxies on length scales from 20 h−1 Mpc to 200 h−1 Mpc. Our main results are: (1) The distribution of galaxies exhibits a multi-fractal scaling behaviour over the scales 20 h−1...
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