17,441 research outputs found
Ubiquitous diffraction resonances in positronium formation from fullerenes
Due to the dominant electron capture by positrons from the molecular wall and
the spatial dephasing across the wall-width, a powerful diffraction effect
universally underlies the positronium (Ps) formation from fullerenes. This
results into trains of resonances in the Ps formation cross section as a
function of the positron beam energy, producing uniform structures in recoil
momenta in analogy with classical single-slit diffraction fringes in the
configuration space. The prediction opens a hitherto unknown avenue of Ps
spectroscopy with nanomaterials.Comment: 6 pages, 3 figures, submitte
Hamiltonian Formulation of Quantum Hall Skyrmions with Hopf Term
We study the nonrelativistic nonlinear sigma model with Hopf term in this
paper. This is an important issue beacuse of its relation to the currently
interesting studies in skyrmions in quantum Hall systems. We perform the
Hamiltonian analysis of this system in variables. When the coefficient
of the Hopf term becomes zero we get the Landau-Lifshitz description of the
ferromagnets. The addition of Hopf term dramatically alters the Hamiltonian
analysis. The spin algebra is modified giving a new structure and
interpretation to the system. We point out momentum and angular momentum
generators and new features they bring in to the system.Comment: 16pages, Latex file, typos correcte
The effect of Pressure in Higher Dimensional Quasi-Spherical Gravitational Collapse
We study gravitational collapse in higher dimensional quasi-spherical
Szekeres space-time for matter with anisotropic pressure. Both local and global
visibility of central curvature singularity has been studied and it is found
that with proper choice of initial data it is possible to show the validity of
CCC for six and higher dimensions. Also the role of pressure in the collapsing
process has been discussed.Comment: 11 pages, 6 figures, RevTeX styl
model with Hopf interaction: the quantum theory
The model with Hopf interaction is quantised following the
Batalin-Tyutin (BT) prescription. In this scheme, extra BT fields are
introduced which allow for the existence of only commuting first-class
constraints. Explicit expression for the quantum correction to the expectation
value of the energy density and angular momentum in the physical sector of this
model is derived. The result shows, in the particular operator ordering that we
have chosen to work with, that the quantum effect has a divergent contribution
of in the energy expectation value. But, interestingly
the Hopf term, though topological in nature, can have a finite contribution to energy density in the homotopically nontrivial
topological sector. The angular momentum operator, however, is found to have no
quantum correction, indicating the absence of any fractional spin even at this
quantum level. Finally, the extended Lagrangian incorporating the BT auxiliary
fields is computed in the conventional framework of BRST formalism exploiting
Faddeev-Popov technique of path integral method.Comment: LaTeX, 28 pages, no figures, typos corrected, journal ref. give
Optical Signatures of Spin-Orbit Interaction Effects in a Parabolic Quantum Dot
We demonstrate here that the dipole-allowed optical absorption spectrum of a
parabolic quantum dot subjected to an external magnetic field reflects the
inter-electron interaction effects when the spin-orbit interaction is also
taken into account. We have investigated the energy spectra and the
dipole-allowed transition energies for up to four interacting electrons
parabolically confined, and have uncovered several novel features in those
spectra that are solely due to the SO interaction.Comment: 4 pages, 3 figure
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