24,622 research outputs found
N-person differential games. Part 1: Duality-finite element methods
The duality approach, which is motivated by computational needs and is done by introducing N + 1 Language multipliers is addressed. For N-person linear quadratic games, the primal min-max problem is shown to be equivalent to the dual min-max problem
Controllable Persistent Atom Current of Bose-Einstein Condensates in an Optical Lattice Ring
In this paper the macroscopic quantum states of Bose-Einstein condensates in
optical lattices is studied by solving the periodic Gross-Pitaevskii equation
in one-dimensional geometry. It is shown that an exact solution seen to be a
travelling wave of excited macroscopic quantum states resultes in a persistent
atom current which can be controlled by adjusting of the barrier height of the
optical periodic potential. A critical condition to generate the travelling
wave is demonstrated and we moreover propose a practical experiment to realize
the persistent atom current in a toroidal atom waveguide.Comment: 9 pages, 1 figure
Phase diagram of two-species Bose-Einstein condensates in an optical lattice
The exact macroscopic wave functions of two-species Bose-Einstein condensates
in an optical lattice beyond the tight-binding approximation are studied by
solving the coupled nonlinear Schrodinger equations. The phase diagram for
superfluid and insulator phases of the condensates is determined analytically
according to the macroscopic wave functions of the condensates, which are seen
to be traveling matter waves.Comment: 13 pages, 2 figure
Fermi-liquid ground state in n-type copper-oxide superconductor Pr0.91Ce0.09LaCuO4-y
We report nuclear magnetic resonance studies on the low-doped n-type
copper-oxide Pr_{0.91}LaCe_{0.09}CuO_{4-y} (T_c=24 K) in the superconducting
state and in the normal state uncovered by the application of a strong magnetic
field. We find that when the superconductivity is removed, the underlying
ground state is the Fermi liquid state. This result is at variance with that
inferred from previous thermal conductivity measurement and contrast with that
in p-type copper-oxides with a similar doping level where high-T_c
superconductivity sets in within the pseudogap phase. The data in the
superconducting state are consistent with the line-nodes gap model.Comment: version to appear in Phys. Rev. Let
Multiple Superconducting Gaps, Anisotropic Spin Fluctuations and Spin-Orbit Coupling in Iron-Pnictides
This article reviews the NMR and NQR studies on iron-based high-temperature
superconductors by the IOP/Okayama group. It was found that the electron pairs
in the superconducting state are in the spin-singlet state with multiple
fully-opened energy gaps. The antiferromagnetic spin fluctuations in the normal
state are found to be closely correlated with the superconductivity. Also the
antiferromagnetic spin fluctuations are anisotropic in the spin space, which is
different from the case in copper oxide superconductors. This anisotropy
originates from the spin-orbit coupling and is an important reflection of the
multiple-bands nature of this new class of superconductors.Comment: 20 pages, 16 figure
Hydration-induced anisotropic spin fluctuations in Na_{x}CoO_{2}\cdot1.3H_{2}O superconductor
We report ^{59}Co NMR studies in single crystals of cobalt oxide
superconductor Na_{0.42}CoO_{2}\cdot1.3H_{2}O (T_c=4.25K) and its parent
compound Na_{0.42}CoO_{2}. We find that both the magnitude and the temperature
(T) dependence of the Knight shifts are identical in the two compounds above
T_c. The spin-lattice relaxation rate (1/T_1) is also identical above T_0
\sim60 K for both compounds. Below T_0, the unhydrated sample is found to be a
non-correlated metal that well conforms to Fermi liquid theory, while spin
fluctuations develop in the superconductor. These results indicate that water
intercalation does not change the density of states but its primary role is to
bring about spin fluctuations. Our result shows that, in the hydrated
superconducting compound, the in-plane spin fluctuation around finite wave
vector is much stronger than that along the c-axis, which indicates that the
spin correlation is quasi-two-dimensional.Comment: 4 pages, 5 figure
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