Condensed Matter
We show that the quantum fluctuations associated with the Bogoliubov quasiparticle vacuum can be strongly concentrated inside dark solitons in a trapped Bose Einstein condensate. We identify a finite number of anomalous modes that are…
By inelastic scattering of polarized neutrons near the (200)-Bragg reflection, the susceptibilities and linewidths of the spin waves and the longitudinal spin fluctuations were determined separately. By aligning the momentum transfers q…
We study the alpha = J_2/J_1-dependence of the magnetization process in the J_1-J_2 model on a square lattice with frustrating couplings J_2 along the diagonals. Perturbation expansions around alpha=J_2/J_1=0 and 1/alpha=0$ yield an…
We report on very low temperature (27 mK) Mossbauer absorption spectra on Gd 155 in the Heisenberg frustrated antiferromagnets Gd2 Sn2 O7 (GdSn) and Gd2 Ti2 O7. We show that electronic fluctuations of correlated Gd3+ moments are present…
We have studied the electronic structure of the spin-gapped system CsV$_2$O$_5$ by means of an ab initio calculation. Our analysis and a re-examination of the susceptibility data indicate that the behavior of this system is much closer to…
A mechanical electroscope based on a change in the resonant frequency of a cantilever one micron in size in the presence of charge has recently been fabricated. We derive the decoherence rate of a charge superposition during measurement…
We use the mean-field approximation to simplify the master equation for sympathetic cooling of Bosons. For the mean single-particle occupation numbers, this approach yields the same equations as the factorization assumption introduced in an…
A novel approach to analyzing time series generated by complex systems, such as markets, is presented. The basic idea of the approach is the {\it Law of Self-Similar Evolution}, according to which any complex system develops self-similarly.…
We have measured electrical transport across epitaxial, nanometer-sized metal-semiconductor interfaces by contacting CoSi2-islands grown on Si(111) with an STM-tip. The conductance per unit area was found to increase with decreasing diode…
We apply the Green's function based full-potential screened Korringa-Kohn-Rostoker method in conjunction with the local density approximation to study the surface energies of the noble and the fcc transition and $sp$ metals. The orientation…
Sea-Displacement Operators for fermions are defined in terms of the Fermi fields in a one-component Fermi system. The main conclusions of this article fully corroborate the conjectures made in our earlier works and provide a mathematically…
We calculate the conductance variation of several metallic carbon nanotubes as their end is being dipped into a liquid metal electrode, where experiments have shown an achievable conductance close to 1 quantum of conductance. The calculated…
A general principle is advanced allowing the classification of nonunique solutions to nonlinear evolution equations, corresponding to different spatio-temporal patterns. This is done by defining the probability distribution of patterns,…
We have measured the mass diffusion coefficient D of 3He in superfluid 4He at temperatures lower than were previously possible. The experimental technique utilizes scintillation light produced when neutron react with 3He nuclei, and allows…
A highly efficient Monte Carlo method for the calculation of the density of states of classical spin systems is presented. As an application, we investigate the density of states Omega_N(E,M) of two- and three-dimensional Ising models with…
We analyze greying of the dark soliton in a Bose-Einstein condensate in the limit of weak interaction between atoms. The condensate initially prepared in the excited dark soliton state is loosing atoms because of spontaneous quantum…
We estimate the amount of temperature-dependent squeezing and entanglement in the collective excitations of trapped Bose-Einstein condensates. We also demonstrate an alternative method of temperature measurement for temperatures much less…
We formulate a method to study two-body correlations in a condensate of N identical bosons. We use the adiabatic hyperspheric approach and assume a Faddeev like decomposition of the wave function. We derive for a fixed hyperradius an…
The framework of the Perturbed Static Path Approximation (PSPA) is used to calculate the partition function of a finite Fermi system from a Hamiltonian with a separable two body interaction. Therein, the collective degree of freedom is…
In this article we study the effect of a delta-interaction on a polymerized membrane of arbitrary internal dimension D. Depending on the dimensionality of membrane and embedding space, different physical scenarios are observed. We emphasize…