144,957 research outputs found
Mott states under the influence of fermion-boson conversion: invasion of superfluidity
I study the influence of fermion-boson conversion near Feshbach resonances on
Mott states of Cooper pairs and demonstrate possible invasion of superfluidity.
The quantum dynamics of Fermi-Bose gases is studied using both an effective
coupled quantum rotor Hamiltonian and a coupled XXZ
XXZ spin Hamiltonian. I also point out two distinct branches of
collective modes in superfluid states, one of which involves anti-symmetric
phase oscillations in fermionic and bosonic channels and is {\em always} gapped
because of fermion-boson conversion.Comment: 5 pages; typos correcte
Exact solvability in contemporary physics
We review the theory for exactly solving quantum Hamiltonian systems through
the algebraic Bethe ansatz. We also demonstrate how this theory applies to
current studies in Bose-Einstein condensation and metallic grains which are of
nanoscale size.Comment: 23 pages, no figures, to appear in ``Classical and Quantum Nonlinear
Integrable Systems'' ed. A. Kund
Solution space heterogeneity of the random K-satisfiability problem: Theory and simulations
The random K-satisfiability (K-SAT) problem is an important problem for
studying typical-case complexity of NP-complete combinatorial satisfaction; it
is also a representative model of finite-connectivity spin-glasses. In this
paper we review our recent efforts on the solution space fine structures of the
random K-SAT problem. A heterogeneity transition is predicted to occur in the
solution space as the constraint density alpha reaches a critical value
alpha_cm. This transition marks the emergency of exponentially many solution
communities in the solution space. After the heterogeneity transition the
solution space is still ergodic until alpha reaches a larger threshold value
alpha_d, at which the solution communities disconnect from each other to become
different solution clusters (ergodicity-breaking). The existence of solution
communities in the solution space is confirmed by numerical simulations of
solution space random walking, and the effect of solution space heterogeneity
on a stochastic local search algorithm SEQSAT, which performs a random walk of
single-spin flips, is investigated. The relevance of this work to glassy
dynamics studies is briefly mentioned.Comment: 11 pages, 4 figures. Final version as will appear in Journal of
Physics: Conference Series (Proceedings of the International Workshop on
Statistical-Mechanical Informatics, March 7-10, 2010, Kyoto, Japan
The two-pseudoscalar-meson decay of with twist-3 corrections
The decays of are discussed
within the standard and modified hard scattering approach when including the
contributions from twist-3 distribution amplitudes and wave functions of the
light pseudoscalar meson. A model for twist-2 and twist-3 distribution
amplitudes and wave functions of the pion and kaon with BHL prescription are
proposed as the solution to the end-point singularities. The results show that
the contributions from twist-3 parts are actually not power suppressed
comparing with the leading-twist contribution. After including the effects from
the transverse momentum of light meson valence-quark state and Sudakov factors,
the decay widths of the into pions or kaons are comparable with the
their experimental data.Comment: 31 pages, 5 figures, 3 table
Dihadron fragmentation functions for large invariant mass
Using perturbative Quantum Chromodynamics, we compute dihadron fragmentation
functions for a large invariant mass of the dihadron pair. The main focus is on
the interference fragmentation function H_1^{\open}, which plays an important
role in spin physics of the nucleon. Our calculation also reveals that
H_1^{\open} and the Collins fragmentation function have a closely related
underlying dynamics. By considering semi-inclusive deep-inelastic scattering,
we further show that collinear factorization in terms of dihadron fragmentation
functions, and collinear factorization in terms of single hadron fragmentation
functions provide the same result in the region of intermediate invariant mass.Comment: 4 pages; issue with layout fixe
Superconductivity of lanthanum revisited: enhanced critical temperature in the clean limit
The thickness dependence of the superconducting energy gap
of double hexagonally close packed (dhcp) lanthanum islands grown on W(110) is
studied by scanning tunneling spectroscopy, from the bulk to the thin film
limit. Superconductivity is suppressed by the boundary conditions for the
superconducting wavefunction at the surface and W/La interface, leading to a
linear decrease of the critical temperature as a function of the inverse
film thickness. For thick, bulk-like films, and are
40% larger as compared to literature values of dhcp La measured by other
techniques. This finding is reconciled by examining the effects of surface
contamination as probed by modifications of the surface state, suggesting that
the large originates in the superior purity of the samples investigated
here.Comment: 14 pages, 7 figure
Quantum phase transition of Bose-Einstein condensates on a ring nonlinear lattice
We study the phase transitions in a one dimensional Bose-Einstein condensate
on a ring whose atomic scattering length is modulated periodically along the
ring. By using a modified Bogoliubov method to treat such a nonlinear lattice
in the mean field approximation, we find that the phase transitions are of
different orders when the modulation period is 2 and greater than 2. We further
perform a full quantum mechanical treatment based on the time-evolving block
decimation algorithm which confirms the mean field results and reveals
interesting quantum behavior of the system. Our studies yield important
knowledge of competing mechanisms behind the phase transitions and the quantum
nature of this system.Comment: 12 pages, 7 figure
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