101,414 research outputs found
Spin-one bosons in low dimensional Mott insulating states
We analyze the strong coupling limit of spin-one bosons in low dimensional
Mott insulating states. In 1D lattices, for an odd number of bosons per site
(), the ground state is a dimerized valence bond crystal state with a
two-fold degeneracy; the low lying elementary spin excitations carry spin one.
For an even number of bosons per site, the ground state is a nondegenerate spin
singlet Mott state. We also argue that in a square lattice in a quantum
disordered limit the ground states should be dimerized valence bond crystals
for an odd integer . Finally, we briefly report results for non-integer
numbers of bosons per site in one-dimensional lattices.Comment: 5 pages; discussions on non-integer case have been shortene
Energy and centrality dependence of particle multiplicity in heavy ion collisions from = 20 to 2760 GeV
The centrality dependence of midrapidity charged-particle multiplicities at a
nucleon-nucleon center-of-mass energy of 2.76 TeV from CMS are compared to
PHOBOS data at 200 and 19.6 GeV. The results are first fitted with a
two-component model which parameterizes the separate contributions of nucleon
participants and nucleon-nucleon collisions. A more direct comparison involves
ratios of multiplicity densities per participant pair between the different
collision energies. The results support and extend earlier indications that the
influences of centrality and collision energy on midrapidity charged-particle
multiplicities are to a large degree independent.Comment: 5 pages, 2 figures, 1 table, Replaced with published version, v3 has
fixed typ
Instability analysis procedure for 3-level multi-bearing rotor-foundation systems
A procedure for the instability analysis of a three-level multispan rotor systems is described. This procedure is based on a distributed mass elastic representation of the rotor system in several eight-coefficient bearings. Each bearing is supported from an elastic foundation on damped, elastic pedestals. The foundation is represented as a general distributed mass elastic structure on discrete supports, which may have different stiffness and damping properties in the horizontal and vertical directions. This system model is suited to studies of instability threshold conditions for multirotor turbomachines on either massive or flexible foundations. The instability conditions is found by obtaining the eigenvalues of the system determinant, which is obtained by the transfer matrix method from the three-level system model. The stability determinant is solved for the lowest rotational speed at which the system damping becomes zero in the complex eigenvalue, and for the whirl frequency corresponding to the natural frequency of the unstable mode. An efficient algorithm for achieving this is described. Application of this procedure to a rigid rotor in two damped-elastic bearings and flexible supports is described. A second example discusses a flexible rotor with four damped-elastic bearings. The third case compares the stability of a six-bearing 300 Mw turbine generator unit, using two different bearing types. These applications validate the computer program and various aspects of the analysis
Magnetization plateaus for spin-one bosons in optical lattices: Stern-Gerlach experiments with strongly correlated atoms
We consider insulating states of spin-one bosons in optical lattices in the
presence of a weak magnetic field. For the states with more than one atom per
lattice site we find a series of quantum phase transitions between states with
fixed magnetization and a canted nematic phase. In the presence of a global
confining potential, this unusual phase diagram leads to several novel
phenomena, including formation of magnetization plateaus. We discuss how these
effects can be observed using spatially resolved density measurements.Comment: 4 pages 5 figure
Localization of Macroscopic Object Induced by the Factorization of Internal Adiabatic Motion
To account for the phenomenon of quantum decoherence of a macroscopic object,
such as the localization and disappearance of interference, we invoke the
adiabatic quantum entanglement between its collective states(such as that of
the center-of-mass (C.M)) and its inner states based on our recent
investigation. Under the adiabatic limit that motion of C.M dose not excite the
transition of inner states, it is shown that the wave function of the
macroscopic object can be written as an entangled state with correlation
between adiabatic inner states and quasi-classical motion configurations of the
C.M. Since the adiabatic inner states are factorized with respect to each parts
composing the macroscopic object, this adiabatic separation can induce the
quantum decoherence. This observation thus provides us with a possible solution
to the Schroedinger cat paradoxComment: Revtex4,23 pages,1figur
Helioseismic Ring Analysis of CME Source Regions
We apply the ring diagram technique to source regions of halo coronal mass
ejections (CMEs) to study changes in acoustic mode parameters before, during,
and after the onset of CMEs. We find that CME regions associated with a low
value of magnetic flux have line widths smaller than the quiet regions implying
a longer life-time for the oscillation modes. We suggest that this criterion
may be used to forecast the active regions which may trigger CMEs.Comment: Accepted for publication in J. Astrophys. Astr. Also available at
http://www2.nso.edu/staff/sushant/paper.htm
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