5,327 research outputs found
Competing superfluid and density-wave ground-states of fermionic mixtures with mass imbalance in optical lattices
We study the effect of mass imbalance on the phase diagram of a two-component
fermionic mixture with attractive interactions in optical lattices. Using
static and dynamical mean-field theories, we show that the pure superfluid
phase is stable for all couplings when the mass imbalance is smaller than a
limiting value. For larger imbalance, phase separation between a superfluid and
a charge-density wave takes place when the coupling exceeds a critical
strength. The harmonic trap induces a spatial segregation of the two phases,
with a rapid variation of the density at the boundary.Comment: e.g.:4 pages, 3 figure
On Kernel Formulas and Dispersionless Hirota Equations
We rederive dispersionless Hirota equations of the dispersionless Toda
hierarchy from the method of kernel formula provided by Carroll and Kodama. We
then apply the method to derive dispersionless Hirota equations of the extended
dispersionless BKP(EdBKP) hierarchy proposed by Takasaki. Moreover, we verify
associativity equations (WDVV equations) in the EdBKP hierarchy from
dispersionless Hirota equations and give a realization of associative algebra
with structure constants expressed in terms of residue formula.Comment: 30 pages, minor corrections, references adde
Design of multivariable feedback control systems via spectral assignment using reduced-order models and reduced-order observers
The feasibility of using reduced order models and reduced order observers with eigenvalue/eigenvector assignment procedures is investigated. A review of spectral assignment synthesis procedures is presented. Then, a reduced order model which retains essential system characteristics is formulated. A constant state feedback matrix which assigns desired closed loop eigenvalues and approximates specified closed loop eigenvectors is calculated for the reduced order model. It is shown that the eigenvalue and eigenvector assignments made in the reduced order system are retained when the feedback matrix is implemented about the full order system. In addition, those modes and associated eigenvectors which are not included in the reduced order model remain unchanged in the closed loop full order system. The fulll state feedback design is then implemented by using a reduced order observer. It is shown that the eigenvalue and eigenvector assignments of the closed loop full order system remain unchanged when a reduced order observer is used. The design procedure is illustrated by an actual design problem
Design of multivariable feedback control systems via spectral assignment using reduced-order models and reduced-order observers
The feasibility of using reduced order models and reduced order observers with eigenvalue/eigenvector assignment procedures is investigated. A review of spectral assignment synthesis procedures is presented. Then, a reduced order model which retains essential system characteristics is formulated. A constant state feedback matrix which assigns desired closed loop eigenvalues and approximates specified closed loop eigenvectors is calculated for the reduced order model. It is shown that the eigenvalue and eigenvector assignments made in the reduced order system are retained when the feedback matrix is implemented about the full order system. In addition, those modes and associated eigenvectors which are not included in the reduced order model remain unchanged in the closed loop full order system. The full state feedback design is then implemented by using a reduced order observer. It is shown that the eigenvalue and eigenvector assignments of the closed loop full order system rmain unchanged when a reduced order observer is used. The design procedure is illustrated by an actual design problem
Experimental studies of equilibrium vortex properties in a Bose-condensed gas
We characterize several equilibrium vortex effects in a rotating
Bose-Einstein condensate. Specifically we attempt precision measurements of
vortex lattice spacing and the vortex core size over a range of condensate
densities and rotation rates. These measurements are supplemented by numerical
simulations, and both experimental and numerical data are compared to theory
predictions of Sheehy and Radzihovsky [17] (cond-mat/0402637) and Baym and
Pethick [25] (cond-mat/0308325). Finally, we study the effect of the
centrifugal weakening of the trapping spring constants on the critical
temperature for quantum degeneracy and the effects of finite temperature on
vortex contrast.Comment: Fixed minor notational inconsistencies in figures. 12 pages, 8
figure
Magneto-Infrared Spectroscopic Study of Ultrathin BiTe Single Crystals
Ultrathin BiTe single crystals laid on Scotch tape are
investigated by Fourier transform infrared spectroscopy at K and in a
magnetic field up to T. The magneto-transmittance spectra of the Bi%
Te/tape composite are analyzed as a two-layer system and the optical
conductivity of BiTe at different magnetic fields are extracted. We
find that magnetic field modifies the optical conductivity in the following
ways: (1) Field-induced transfer of the optical weight from the lower frequency
regime (cm) to the higher frequency regime (cm) due
to the redistribution of charge carriers across the Fermi surface. (2) Evolving
of a Fano-resonance-like spectral feature from an anti-resonance to a resonance
with increasing magnetic field. Such behavior can be attributed to the
electron-phonon interactions between the optical phonon mode and
the continuum of electronic transitions. (3) Cyclotron resonance resulting from
the inter-valence band Landau level transitions, which can be described by the
electrodynamics of massive Dirac holes
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