1,638 research outputs found
On subgroups in division rings of type
Let be a division ring with center . We say that is a {\em
division ring of type } if for every two elements the division
subring is a finite dimensional vector space over . In this paper
we investigate multiplicative subgroups in such a ring.Comment: 10 pages, 0 figure
Incompressible Quantum Liquids and New Conservation Laws
In this letter we investigate a class of Hamiltonians which, in addition to
the usual center-of-mass (CM) momentum conservation, also have center-of-mass
position conservation. We find that regardless of the particle statistics, the
energy spectrum is at least q-fold degenerate when the filling factor is ,
where and are coprime integers. Interestingly the simplest Hamiltonian
respecting this type of symmetry encapsulates two prominent examples of novel
states of matter, namely the fractional quantum Hall liquid and the quantum
dimer liquid. We discuss the relevance of this class of Hamiltonian to the
search for featureless Mott insulators.Comment: updated version, to be published by PR
Quasiparticle Heat Transport in BaKFeAs: Evidence for a k-dependent Superconducting Gap without Nodes
The thermal conductivity of the iron-arsenide superconductor
BaKFeAs ( 30 K) was measured in single crystals
at temperatures down to mK (/600) and in magnetic
fields up to T (/4). A negligible residual linear term
in as shows that there are no zero-energy quasiparticles
in the superconducting state. This rules out the existence of line and in-plane
point nodes in the superconducting gap, imposing strong constraints on the
symmetry of the order parameter. It excludes d-wave symmetry, drawing a clear
distinction between these superconductors and the high- cuprates. However,
the fact that a magnetic field much smaller than can induce a residual
linear term indicates that the gap must be very small on part of the Fermi
surface, whether from strong anisotropy or band dependence, or both
Walks on weighted networks
We investigate the dynamics of random walks on weighted networks. Assuming
that the edge's weight and the node's strength are used as local information by
a random walker, we study two kinds of walks, weight-dependent walk and
strength-dependent walk. Exact expressions for stationary distribution and
average return time are derived and confirmed by computer simulations. We
calculate the distribution of average return time and the mean-square
displacement for two walks on the BBV networks, and find that a
weight-dependent walker can arrive at a new territory more easily than a
strength-dependent one.Comment: 4 pages, 5 figures. minor modifications. Comments and suggestions are
favored by the author
Understanding entangled spins in QED
The stability of two entangled spins dressed by electrons is studied by
calculating the scattering phase shifts. The interaction between electrons is
interpreted by fully relativistic QED and the screening effect is described
phenomenologically in the Debye exponential form . Our results
show that if the (Einstein-Podolsky-Rosen-) EPR-type states are kept stable
under the interaction of QED, the spatial wave function must be
parity-dependent. The spin-singlet state and the polarized state along the z-axis\QTR{bf}{\}give rise to two
different kinds of phase shifts\QTR{bf}{.} Interestingly, the interaction
between electrons in the spin-singlet pair is found to be attractive. Such an
attraction could be very useful when we extract the entangled spins from
superconductors. A mechanism to filter the entangled spins is also discussed.Comment: 6 pages, 3 figures. changes adde
Entanglement in spin-one Heisenberg chains
By using the concept of negativity, we study entanglement in spin-one
Heisenberg chains. Both the bilinear chain and the bilinear-biquadratic chain
are considered. Due to the SU(2) symmetry, the negativity can be determined by
two correlators, which greatly facilitate the study of entanglement properties.
Analytical results of negativity are obtained in the bilinear model up to four
spins and the two-spin bilinear-biquadratic model, and numerical results of
negativity are presented. We determine the threshold temperature before which
the thermal state is doomed to be entangled.Comment: 7 pages and 4 figure
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