17,064 research outputs found
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
Response to sub-threshold stimulus is enhanced by spatially heterogeneous activity
Sub-threshold stimuli cannot initiate excitations in active media, but
surprisingly as we show in this paper, they can alter the time-evolution of
spatially heterogeneous activity by modifying the recovery dynamics. This
results in significant reduction of waveback velocity which may lead to spatial
coherence, terminating all activity in the medium including spatiotemporal
chaos. We analytically derive model-independent conditions for which such
behavior can be observed.Comment: 5 pages, 5 figure
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
Seeing a c-theorem with holography
There is no known model in holography exhibiting a -theorem where the
central charges of the dual CFT are distinct. We examine a holographic model of
RG flows in a framework where the bulk gravity theory contains higher curvature
terms. The latter allows us to distinguish the flow of the central charges
and in the dual field theories in four dimensions. One finds that the flow
of is naturally monotonic but that of is not. Extending the analysis of
holographic RG flows to higher dimensions, we are led to formulate a novel
c-theorem in arbitrary dimensions for a universal coefficient appearing in the
entanglement entropy of the fixed point CFT's.Comment: 5 pages, 1 figure, v2: minor change
Prediction of the asymmetry in decay
Of all decays, the decay
has the smallest observed branching ratio as it takes place primarily via the
suppressed -exchange diagram. The asymmetry for this mode is yet to be
measured experimentally. By exploiting the relationship among the decay
amplitudes of decays (using isospin and topological
amplitudes) we are able to relate the asymmetries and branching ratios by
a simple expression. This enables us to predict the asymmetry in
. While the predicted central values of
are outside the physically allowed region, they are currently associated with
large uncertainties owing to the large errors in the measurements of the branching ratio (), the other asymmetries
(of ) and (of ). With a precise determination of , and
, one can use our analytical result to predict with a
reduced error and compare it with the experimental measurement when it becomes
available. The correlation between and is an interesting
aspect that can be probed in ongoing and future particle physics experiments
such as LHCb and Belle II.Comment: 21 pages, 6 figures, accepted for publication in JHE
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