1,331 research outputs found
Polyfluorene as a model system for space-charge-limited conduction
Ethyl-hexyl substituted polyfluorene (PF) with its high level of molecular
disorder can be described very well by one-carrier space-charge-limited
conduction for a discrete set of trap levels with energy 0.5 eV above
the valence band edge. Sweeping the bias above the trap-filling limit in the
as-is polymer generates a new set of exponential traps, which is clearly seen
in the density of states calculations. The trapped charges in the new set of
traps have very long lifetimes and can be detrapped by photoexcitation. Thermal
cycling the PF film to a crystalline phase prevents creation of additional
traps at higher voltages.Comment: 13 pages, 4 figures. Physical Review B (accepted, 2007
Relativistic Mean Field in 80 nuclei and low energy proton reactions
Relativistic Mean Field calculations have been performed for a number of
nuclei in mass 80 region. Ground state binding energy, charge radius
and charge density values have been compared with experiment. Optical potential
have been generated folding the nuclear density with the microscopic nuclear
interaction DDM3Y. S-factors for low energy () and () reactions
have been calculated and compared with experiment.Comment: To appear in Physical Review
Seiberg-Witten map and Galilean symmetry violation in a non-commutative planar system
An effective U(1) gauge invariant theory is constructed for a non-commutative
Schrodinger field coupled to a background U(1)_{\star} gauge field in
2+1-dimensions using first order Seiberg-Witten map. We show that this
effective theory can be cast in the form of usual Schrodinger action with
interaction terms of noncommutative origin provided the gauge field is of
``background'' type with constant magnetic field. The Galilean symmetry is
investigated and a violation is found in the boost sector. We also consider the
problem of Hall conductivity in this framework.Comment: REVTeX, 4 pages, Title changed, Paper shortened, Appendix removed, A
new section on Galilean symmetry adde
Ground states and excited states of hypernuclei in Relativistic Mean Field approach
Hypernuclei have been studied within the framework of Relativistic Mean Field
theory. The force FSU Gold has been extended to include hyperons. The effective
hyperon-nucleon and nucleon-nucleon interactions have been obtained by fitting
experimental energies in a number of hypernuclei over a wide range of mass.
Calculations successfully describe various features including hyperon
separation energy and single particle spectra of single-\Lambda hypernuclei
throughout the periodic table. We also extend this formalism to double-\Lambda
hypernuclei.Comment: 16 pages,3 figure
Stanja kontinuuma u jezgrama kalcija i nikla bogatim neutronima
The effect of the resonant continuum on Ca and Ni nuclei near the neutron drip line has been investigated. The relativistic mean-field equations are solved using scattering-like conditions for the positive energy states. Pairing is implemented through a zero range interaction and the BCS equations are solved including the resonant states. We find that our calculation can reproduce the values for binding energy, radius, two-neutron separation energy, etc. in most cases. The nuclei 70,72Ca show a sudden increase in the tail of the density distribution as the 3s1/2 state, being very weakly bound and having no centrifugal barrier, extends outside the nucleus radius to a large distance creating a neutron halo. Ni isotopes do not show any neutron halo. Appearance of new magic number and disappearance of the old ones in neutron-rich isotopes lead to dramatic difference in the drip line for even- and odd-mass nuclei in the two chains.Istražujemo učinak rezonantnog kontinuuma u jezgrama Ca i Ni blizu granice bijega. Riješili smo relativističke jednadžbe za srednje polje primjenom uvjeta za raspršenje za stanja pozitivne energije. Sparivanje se uvodi međudjelovanjem nultog dosega a BCS jednadžbe smo riješili uključujući rezonantna stanja. Naši računi mogu u većini slučajeva dati vrijednosti za energiju vezanja, polumjer, dvoneutronsku energiju odvajanja, itd. Jezgre 70,72Ca pokazuju nagao porast repa raspodjele gustoće kako se, zbog slabog vezanja i izostanka centrifugalne barijere, stanje 3s1/2 proširuje daleko izvan polumjera jezgre, stvarajući neutronski halo. Izotopi nikla ne pokazuju neutronski halo. Pojava magičnih brojeva i nestanak ranijih u izotopima bogatim neutronima vodi do dramatičnih promjena linije bijega u parnim i neparnim jezgrama oba niza
-Minkowski and Snyder algebra from reparametrisation symmetry
Following our earlier work \cite{sunandan1, sunandan2}, we derive
noncommuting phase-space structures which are combinations of both the
-Minkowski and Snyder algebra by exploiting the reparametrisation
symmetry of the recently proposed Lagrangian for a point particle \cite{subir}
satisfying the exact Doubly Special Relativity dispersion relation in the
Magueijo-Smolin framework.Comment: Accepted in Euro Physics Letter
Lie algebraic noncommuting structures from reparametrisation symmetry
We extend our earlier work of revealing both space-space and space-time
noncommuting structures in various models in particle mechanics exhibiting
reparametrisation symmetry. We show explicitly (in contrast to the earlier
results in our paper \cite{sg}) that for some special choices of the
reparametrisation parameter , one can obtain space-space noncommuting
structures which are Lie-algebraic in form even in the case of the relativistic
free particle. The connection of these structures with the existing models in
the literature is also briefly discussed. Further, there exists some values of
for which the noncommutativity in the space-space sector can be made
to vanish. As a matter of internal consistency of our approach, we also study
the angular momentum algebra in details.Comment: 9 pages Latex, some references adde
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