3,662 research outputs found
Hadronic components of EAS by rigorous saddle point method in the energy range between 10(5) and 10(8) GeV
The study of hadronic components in the high energy range between 10 to the 5 and 10 to the 8 Gev exhibits by far the strongest mass sensitivity since the primary energy spectrum as discussed by Linsley and measured by many air shower experimental groups indicates a change of slope from -1.7 to 2.0 in this energy range. This change of slope may be due to several reasons such as a genuine spectral feature of astrophysical origin, a confinement effect of galactic component or a rather rapid change of mass, a problem which we have attempted to study here in detail
Effect of spin-orbit interaction on the critical temperature of an ideal Bose gas
We consider Bose-Einstein condensation of an ideal bose gas with an equal
mixture of `Rashba' and `Dresselhaus' spin-orbit interactions and study its
effect on the critical temperature.
In uniform bose gas a `cusp' and a sharp drop in the critical temperature
occurs due to the change in the density of states at a critical Raman coupling
where the degeneracy of the ground states is lifted. Relative drop in the
critical temperature depends on the diluteness of the gas as well as on the
spin-orbit coupling strength. In the presence of a harmonic trap, the cusp in
the critical temperature smoothened out and a minimum appears. Both the drop in
the critical temperature and lifting of `quasi-degeneracy' of the ground states
exhibit crossover phenomena which is controlled by the trap frequency. By
considering a 'Dicke' like model we extend our calculation to bosons with large
spin and observe a similar minimum in the critical temperature near the
critical Raman frequency, which becomes deeper for larger spin. Finally in the
limit of infinite spin, the critical temperature vanishes at the critical
frequency, which is a manifestation of Dicke type quantum phase transition.Comment: 9 pages, 6 figure
Fragmentation of Positronium (Ps) in collision with Li ion
Fragmentation of ground state ortho Positronium (Ps) in collision with Li ion
(Li+) is studied in the framework of post collisional Coulomb distorted eikonal
approximation (CDEA) for the target elastic case . The present model takes
account of the two center effect on the ejected e which is crucial for a proper
description of the projectile ionization involving an ionic target. Both the
fully differential (TDCS) and the doubly differential (DDCS) cross sections
(energy spectra) are investigated at intermediate and high incident energies. A
broad distinct Electron loss peak (ELP) centered around v_e ~ v_p is noted in
the e energy spectrum in contrast to the sharp ELP for a heavy projectile. Two
salient features are noted in the present study: i) the shift of the e DDCS
peak (summed over e+ angles) towards higher ejection energy with respect to
half the residual energy of the system, ii) comparison of the e& e+ energy
spectra reflect a strong e - e+ asymmetry with respect to the ratio v_e/v_p =1
>. Both these features could be attributed to the post collisional two center
effect on the e due to its parent nucleus (e+) and the screened target ion .
Two different wave functions of the Li ion are chosen in order to test the
sensitivity of the present results with respect to the choice of the wave
function.Comment: 19 pages, 7 figure
Scattering states of a particle, with position-dependent mass, in a symmetric heterojunction
The study of a particle with position-dependent effective mass (pdem), within
a double heterojunction is extended into the complex domain --- when the region
within the heterojunctions is described by a non Hermitian
symmetric potential. After obtaining the exact analytical solutions, the
reflection and transmission coefficients are calculated, and plotted as a
function of the energy. It is observed that at least two of the characteristic
features of non Hermitian symmetric systems --- viz., left / right
asymmetry and anomalous behaviour at spectral singularity, are preserved even
in the presence of pdem. The possibility of charge conservation is also
discussed.Comment: 12 pages, including 6 figures; Journal of Physics A : Math. Theor.
(2012
SWKB Quantization Rules for Bound States in Quantum Wells
In a recent paper by Gomes and Adhikari (J.Phys B30 5987(1997)) a matrix
formulation of the Bohr-Sommerfield quantization rule has been applied to the
study of bound states in one dimension quantum wells. Here we study these
potentials in the frame work of supersymmetric WKB (SWKB) quantization
approximation and find that SWKB quantization rule is superior to the modified
Bohr-Sommerfield or WKB rules as it exactly reproduces the eigenenergies.Comment: 8 page
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