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 $\sim$ 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 A≈A\approx80 nuclei and low energy proton reactions

Relativistic Mean Field calculations have been performed for a number of nuclei in mass $A\approx$80 region. Ground state binding energy, charge radius and charge density values have been compared with experiment. Optical potential have been generated folding the nuclear density with the microscopic nuclear interaction DDM3Y. S-factors for low energy ($p,\gamma$) and ($p,n$) 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

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

κ\kappa-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 $\kappa$-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 $\epsilon$, 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 $\epsilon$ 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