124,061 research outputs found
Novel quantum phases of dipolar Bose gases in optical lattices
We investigate the quantum phases of polarized dipolar Bosons loaded into a
two-dimensional square and three-dimensional cubic optical lattices. We show
that the long-range and anisotropic nature of the dipole-dipole interaction
induces a rich variety of quantum phases, including the supersolid and striped
supersolid phases in 2D lattices, and the layered supersolid phase in 3D
lattices.Comment: 4 pages, 4 figure
Quantum Thermalization With Couplings
We study the role of the system-bath coupling for the generalized canonical
thermalization [S. Popescu, et al., Nature Physics 2,754(2006) and S. Goldstein
et al., Phys. Rev. Lett. 96, 050403(2006)] that reduces almost all the pure
states of the "universe" [formed by a system S plus its surrounding heat bath
] to a canonical equilibrium state of S. We present an exactly solvable, but
universal model for this kinematic thermalization with an explicit
consideration about the energy shell deformation due to the interaction between
S and B. By calculating the state numbers of the "universe" and its subsystems
S and B in various deformed energy shells, it is found that, for the
overwhelming majority of the "universe" states (they are entangled at least),
the diagonal canonical typicality remains robust with respect to finite
interactions between S and B. Particularly, the kinematic decoherence is
utilized here to account for the vanishing of the off-diagonal elements of the
reduced density matrix of S. It is pointed out that the non-vanishing
off-diagonal elements due to the finiteness of bath and the stronger
system-bath interaction might offer more novelties of the quantum
thermalization.Comment: 4 pages, 2 figure
Decay of Loschmidt Echo Enhanced by Quantum Criticality
We study the transition of a quantum system from a pure state to a mixed
one, which is induced by the quantum criticality of the surrounding system
coupled to it. To characterize this transition quantitatively, we carefully
examine the behavior of the Loschmidt echo (LE) of modelled as an Ising
model in a transverse field, which behaves as a measuring apparatus in quantum
measurement. It is found that the quantum critical behavior of strongly
affects its capability of enhancing the decay of LE: near the critical value of
the transverse field entailing the happening of quantum phase transition, the
off-diagonal elements of the reduced density matrix describing vanish
sharply.Comment: 4 pages, 3 figure
Contact law and impact responses of laminated composites
Static identation tests were performed to determine the law of contact between a steel ball and glass/epoxy and graphite/epoxy laminated composites. For both composites the power law with an index of 1.5 was found to be adequate for the loading curve. Substantial permanent deformations were noted after the unloading. A high order beam finite element was used to compute the dynamic contact force and response of the laminated composite subjected to the impact of an elastic sphere. This program can be used with either the classical Hertzian contact law or the measured contact law. A simple method is introduced for estimating the contact force and contact duration in elastic impacts
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