49,781 research outputs found
Chirality in Liquid Crystals: from Microscopic Origins to Macroscopic Structure
Molecular chirality leads to a wonderful variety of equilibrium structures,
from the simple cholesteric phase to the twist-grain-boundary phases, and it is
responsible for interesting and technologically important materials like
ferroelectric liquid crystals. This paper will review some recent advances in
our understanding of the connection between the chiral geometry of individual
molecules and the important phenomenological parameters that determine
macroscopic chiral structure. It will then consider chiral structure in
columnar systems and propose a new equilibrium phase consisting of a regular
lattice of twisted ropes.Comment: 20 pages with 6 epsf figure
Strong eigenfunction correlations near the Anderson localization transition
We study overlap of two different eigenfunctions as compared with
self-overlap in the framework of an infinite-dimensional version of the
disordered tight-binding model. Despite a very sparse structure of the
eigenstates in the vicinity of Anderson transition their mutual overlap is
still found to be of the same order as self-overlap as long as energy
separation is smaller than a critical value. The latter fact explains
robustness of the Wigner-Dyson level statistics everywhere in the phase of
extended states. The same picture is expected to hold for usual d-dimensional
conductors, ensuring the form of the level repulsion at critical
point.Comment: 4 pages, RevTe
A two component jet model for the X-ray afterglow flat segment in short GRB 051221A
In the double neutron star merger or neutron star-black hole merger model for
short GRBs, the outflow launched might be mildly magnetized and neutron rich.
The magnetized neutron-rich outflow will be accelerated by the magnetic and
thermal pressure and may form a two component jet finally, as suggested by
Vlahakis, Peng & K\"{o}nigl (2003). We show in this work that such a two
component jet model could well reproduce the multi-wavelength afterglow
lightcurves, in particular the X-ray flat segment, of short GRB 051221A. In
this model, the central engine need not to be active much longer than the
prompt ray emission.Comment: 11 pages, 2 figure; Accepted for publication by ApJ
Rapid collapse of spin waves in non-uniform phases of the second Landau level
The spin degree of freedom in quantum phases of the second Landau level is
probed by resonant light scattering. The long wavelength spin wave, which
monitors the degree of spin polarization, is at the Zeeman energy in the fully
spin-polarized state at =3. At lower filling factors the intensity of the
Zeeman mode collapses indicating loss of polarization. A novel continuum of
low-lying excitations emerges that dominates near =8/3 and =5/2.
Resonant Rayleigh scattering reveals that quantum fluids for break up
into robust domain structures. While the state at =5/2 is considered to be
fully polarized, these results reveal unprecedented roles for spin degrees of
freedom.Comment: 4 pages, 5 figure
Spitzer 70 Micron Source Counts in GOODS-North
We present ultradeep Spitzer 70 μm observations of GOODS-North (Great Observatories Origins Deep Survey). For the first time, the turnover in the 70 μm Euclidean-normalized differential source counts is observed. We derive source counts down to a flux density of 1.2 mJy. From the measured source counts and fluctuation analysis, we estimate a power-law approximation of the faint 70 μm source counts of dN/dS ∝ S^−1.6, consistent with that observed for the faint 24 μm sources. An extrapolation of the 70 μm source counts to zero flux density implies a total extragalactic background light (EBL) of 7.4 ± 1.9 nW m^−2 sr^−1. The source counts above 1.2 mJy account for about 60% of the estimated EBL. From fluctuation analysis, we derive a photometric confusion level of σc = 0.30 ± 0.15 mJy (q = 5) for the Spitzer 70 μm band
Spontaneous Relaxation of a Charge Qubit under Electrical Measurement
In this work we first derive a generalized conditional master equation for
quantum measurement by a mesoscopic detector, then study the readout
characteristics of qubit measurement where a number of new features are found.
The work would in particular highlight the qubit spontaneous relaxation effect
induced by the measurement itself rather than an external thermal bath.Comment: 4 pages, 2 figures; an error in Eq.(8) is correcte
Symmetric multiparty-controlled teleportation of an arbitrary two-particle entanglement
We present a way for symmetric multiparty-controlled teleportation of an
arbitrary two-particle entangled state based on Bell-basis measurements by
using two Greenberger-Horne-Zeilinger states, i.e., a sender transmits an
arbitrary two-particle entangled state to a distant receiver, an arbitrary one
of the agents via the control of the others in a network. It will be
shown that the outcomes in the cases that is odd or it is even are
different in principle as the receiver has to perform a controlled-not
operation on his particles for reconstructing the original arbitrary entangled
state in addition to some local unitary operations in the former. Also we
discuss the applications of this controlled teleporation for quantum secret
sharing of classical and quantum information. As all the instances can be used
to carry useful information, its efficiency for qubits approaches the maximal
value.Comment: 9 pages, 3 figures; the revised version published in Physical Review
A 72, 022338 (2005). The detail for setting up a GHZ-state quantum channel is
adde
NMR Search for the Spin Nematic State in LaFeAsO Single Crystal
We report a 75-As single crystal NMR investigation of LaFeAsO, the parent
phase of a pnictide high Tc superconductor. We demonstrate that spin dynamics
develop a strong two-fold anisotropy within each orthorhombic domain below the
tetragonal-orthorhombic structural phase transition at T[TO]~156 K. This
intermediate state with a dynamical breaking of the rotational symmetry freezes
progressively into a spin density wave (SDW) below T[SDW]~142 K. Our findings
are consistent with the presence of a spin nematic state below T[TO] with an
incipient magnetic order.Comment: Revised manuscript accepted for publication in Phys. Rev. Let
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