A simplified picture for Pi electrons in conjugated polymers : from PPP Hamiltonian to an effective molecular crystal approachAn excitonic method proper to study conjugated oligomers and polymers is described and its applicability tested on the ground state and first excited states of trans-polyacetylene, taken as a model.…S. Pleutin, J. L. Fave·Jul 9, 1998SaveLearn
Theory of exciton-exciton correlation in nonlinear optical responseWe present a systematic theory of Coulomb interaction effects in the nonlinear optical processes in semiconductors using a perturbation series in the exciting laser field. The third-order dynamical…Th. Oestreich, K. Schoenhammer, L. J. Sham·Jul 9, 1998SaveLearn
Magnetic fluctuations in coupled inequivalent Hubbard layers as a model for Y2Ba4Cu7O15We investigate, within the fluctuation-exchange approximation, a correlated-electron model for Y2Ba4Cu7O15 represented by two inequivalent Hubbard layers coupled by an interlayer hopping t.…G. Hildebrand, E. Arrigoni, J. Schmalian et al.·Jul 9, 1998SaveLearn
Integrability and Quantum Chaos in Spin Glass ShardsWe study spin glass clusters ("shards") in a random transverse magnetic field, and determine the regime where quantum chaos and random matrix level statistics emerge from the integrable…B. Georgeot, D. L. Shepelyansky·Jul 8, 1998SaveLearn
Dynamics versus replicas in the random field Ising modelIn a previous article we have shown, within the replica formalism, that the conventional picture of the random field Ising model breaks down, by the effect of singularities in the interactions…E. Brézin, C. De Dominicis·Jul 8, 1998SaveLearn
Longitudinal Force on a Moving PotentialWe show a formal result of the longitudinal force acting on a moving potential. The potential can be velocity-dependent, which appears in various interesting physical systems, such as electrons in…Jian-Ming Tang, D. J. Thouless·Jul 8, 1998SaveLearn
Phase Transition in the Number Partitioning ProblemNumber partitioning is an NP-complete problem of combinatorial optimization. A statistical mechanics analysis reveals the existence of a phase transition that separates the easy from the hard to…Stephan Mertens·Jul 6, 1998SaveLearn
Long-time dynamics of de Gennes' model for reptationDiffusion of a polymer in a gel is studied within the framework of de Gennes' model for reptation. Our results for the scaling of the diffusion coefficient D and the longest relaxation time tau…G. T. Barkema, H. M. Krenzlin·Jul 6, 1998SaveLearn
Studies of Bacterial Branching Growth using Reaction-Diffusion Models for Colonial DevelopmentVarious bacterial strains exhibit colonial branching patterns during growth on poor substrates. These patterns reflect bacterial cooperative self-organization and cybernetic processes of…Ido Golding, Yonathan Kozlovsky, Inon Cohen et al.·Jul 6, 1998SaveLearn
Dynamic exchange-correlation potentials for the electron gas in dimensionality D=3 and D=2Recent progress in the formulation of a fully dynamical local approximation to time-dependent Density Functional Theory appeals to the longitudinal and transverse components of the exchange and…R. Nifosi', S. Conti, M. P. Tosi·Jul 6, 1998SaveLearn
Collapse transitions of a periodic hydrophilic hydrophobic chainWe study a single self avoiding hydrophilic hydrophobic polymer chain, through Monte Carlo lattice simulations. The affinity of monomer i for water is characterized by a (scalar) charge λi,…E. Orlandini, T. Garel·Jul 6, 1998SaveLearn
Correlation Functions of the Ising Model with Multisite Interaction on the Husimi LatticeWe consider a general spin-1/2 Ising model with multisite interaction on the Husimi lattice with the coordination number q and derive an analytical expression of correlation functions for stable…N. S. Ananikian, R. G. Ghulghazaryan, N. Sh. Izmailian·Jul 6, 1998SaveLearn
Temperature dependence of the normal-state Hall coefficient of a quasi-one-dimensional metalWe develop a systematic theory of the Hall effect in Q1D conductors in both weak and strong magnetic fields for a model where the electron relaxation time varies over the Fermi surface. At high…Victor M. Yakovenko, Anatoley T. Zheleznyak·Jul 3, 1998SaveLearn
Finite Temperature Path Integral Method for Fermions and Bosons: a Grand Canonical ApproachThe calculation of the density matrix for fermions and bosons in the Grand Canonical Ensemble allows an efficient way for the inclusion of fermionic and bosonic statistics at all temperatures. It is…M. Skorobogatiy, J. Joannopoulos·Jul 3, 1998SaveLearn
Phase separation in systems with absorbing statesWe study the problem of phase separation in systems with a positive definite order parameter, and in particular, in systems with absorbing states. Owing to the presence of a single minimum in the…M. A. Munoz, U. Marini Bettolo Marconi, R. Cafiero·Jul 3, 1998SaveLearn
Dephasing at Low TemperaturesWe discuss the significance and the calculation of dephasing at low temperatures. The particle is moving diffusively due to a static disorder configuration, while the interference between classical…Doron Cohen, Yoseph Imry·Jul 2, 1998SaveLearn
Friction Coefficient and Berry Phase for a Topological Singularity in a SuperfluidThe coexistence of the universal transverse force and the non-universal friction force on a topological singularity in a superfluid is shown here. Based on the BCS type microscopic theory, we…X. -M. Zhu, P. Ao·Jul 2, 1998SaveLearn
Dynamics and Thermodynamics of the Bose-Hubbard modelWe report results from a systematic analytic strong-coupling expansion of the Bose-Hubbard model in one and two spatial dimensions. We obtain numerically exact results for the dispersion of single…N. Elstner, H. Monien·Jul 2, 1998SaveLearn
Time-Resolved Studies of Stick-Slip Friction in Sheared Granular LayersSensitive and fast force measurements are performed on sheared granular layers undergoing stick-slip motion, along with simultaneous imaging. A full study has been done for spherical particles with a…S. Nasuno, A. Kudrolli, A. Bak et al.·Jul 1, 1998SaveLearn
Semiclassical Corrections to a Static Bose-Einstein Condensate at Zero TemperatureIn the mean-field approximation, a trapped Bose-Einstein condensate at zero temperature is described by the Gross-Pitaevskii equation for the condensate, or equivalently, by the hydrodynamic…Jens O. Andersen, Eric Braaten·Jun 30, 1998SaveLearn
Wave Function of the Largest Skyrmion on a SphereIt has been clarified that charged excitation known as a skyrmion exists around the ferromagnetic ground state at the Landau level filling factor ν=1/q, where q is an odd integer. An infinite…Daijiro Yoshioka·Jun 30, 1998SaveLearn
Equation of state near the endpoint of the critical lineWe discuss first order transitions for systems in the Ising universality class. The critical long distance physics near the endpoint of the critical line is explicitly connected to microscopic…S. Seide, C. Wetterich·Jun 30, 1998SaveLearn
Current responses and voltage fluctuations in Josephson-junction systemsWe consider arrays of Josephson junctions as well as single junctions in both the classical and quantum-mechanical regimes, and examine the generalized (frequency-dependent) resistance, which…Mahn-Soo Choi, M. Y. Choi, Sung-Ik Lee·Jun 30, 1998SaveLearn
Spatial coherence and density correlations of trapped Bose gasesWe study first and second order coherence of trapped dilute Bose gases using appropriate correlation functions. Special attention is given to the discussion of second order or density correlations.…M. Naraschewski, R. J. Glauber·Jun 29, 1998SaveLearn
Optical Constants and Functions of Corundum Single Crystals in the Vacuum Ultraviolat RegionOptical reflection spectra of corundum single crystals grown by HOC and Verneil methods are investigated before and after irradiated by electrons and neutrons using synchrotron radiation polarization…V. V. Harutunyan, T. S. Hakobyan, A. S. Hovhannesian et al.·Jun 29, 1998SaveLearn