451 research outputs found
Geometric Phase: a Diagnostic Tool for Entanglement
Using a kinematic approach we show that the non-adiabatic, non-cyclic,
geometric phase corresponding to the radiation emitted by a three level cascade
system provides a sensitive diagnostic tool for determining the entanglement
properties of the two modes of radiation. The nonunitary, noncyclic path in the
state space may be realized through the same control parameters which control
the purity/mixedness and entanglement. We show analytically that the geometric
phase is related to concurrence in certain region of the parameter space. We
further show that the rate of change of the geometric phase reveals its
resilience to fluctuations only for pure Bell type states. Lastly, the
derivative of the geometric phase carries information on both purity/mixedness
and entanglement/separability.Comment: 13 pages 6 figure
A note on the geometric phase in adiabatic approximation
The adiabatic theorem shows that the instantaneous eigenstate is a good
approximation of the exact solution for a quantum system in adiabatic
evolution. One may therefore expect that the geometric phase calculated by
using the eigenstate should be also a good approximation of exact geometric
phase. However, we find that the former phase may differ appreciably from the
latter if the evolution time is large enough.Comment: 11 pages, no figure, modified and Journal-ref adde
Aharonov-Anandan phase in Lipkin-Meskov-Glick model
In the system of several interacting spins, geometric phases have been
researched intensively.However, the studies are mainly focused on the adiabatic
case (Berry phase), so it is necessary for us to study the non-adiabatic
counterpart (Aharonov and Anandan phase). In this paper, we analyze both the
non-degenerate and degenerate geometric phase of Lipkin-Meskov-Glick type
model, which has many application in Bose-Einstein condensates and entanglement
theory. Furthermore, in order to calculate degenerate geometric phases, the
Floquet theorem and decomposition of operator are generalized. And the general
formula is achieved
Relation between geometric phases of entangled bi-partite systems and their subsystems
This paper focuses on the geometric phase of entangled states of bi-partite
systems under bi-local unitary evolution. We investigate the relation between
the geometric phase of the system and those of the subsystems. It is shown that
(1) the geometric phase of cyclic entangled states with non-degenerate
eigenvalues can always be decomposed into a sum of weighted non-modular pure
state phases pertaining to the separable components of the Schmidt
decomposition, though the same cannot be said in the non-cyclic case, and (2)
the geometric phase of the mixed state of one subsystem is generally different
from that of the entangled state even by keeping the other subsystem fixed, but
the two phases are the same when the evolution operator satisfies conditions
where each component in the Schmidt decomposition is parallel transported
Entanglement, Bell Inequalities and Decoherence in Particle Physics
We demonstrate the relevance of entanglement, Bell inequalities and
decoherence in particle physics. In particular, we study in detail the features
of the ``strange'' system as an example of entangled
meson--antimeson systems. The analogies and differences to entangled spin--1/2
or photon systems are worked, the effects of a unitary time evolution of the
meson system is demonstrated explicitly. After an introduction we present
several types of Bell inequalities and show a remarkable connection to CP
violation. We investigate the stability of entangled quantum systems pursuing
the question how possible decoherence might arise due to the interaction of the
system with its ``environment''. The decoherence is strikingly connected to the
entanglement loss of common entanglement measures. Finally, some outlook of the
field is presented.Comment: Lectures given at Quantum Coherence in Matter: from Quarks to Solids,
42. Internationale Universit\"atswochen f\"ur Theoretische Physik,
Schladming, Austria, Feb. 28 -- March 6, 2004, submitted to Lecture Notes in
Physics, Springer Verlag, 45 page
Reversed anisotropies and thermal contraction of FCC (110) surfaces
The observed anisotropies of surface vibrations for unreconstructed FCC metal
(110) surfaces are often reversed from the "common sense" expectation. The
source of these reversals is investigated by performing ab initio density
functional theory calculations to obtain the surface force constant tensors for
Ag(110), Cu(110) and Al(110). The most striking result is a large enhancement
in the coupling between the first and third layers of the relaxed surface,
which strongly reduces the amplitude of out-of-plane vibrations of atoms in the
first layer. This also provides a simple explanation for the thermal
contraction of interlayer distances. Both the anisotropies and the thermal
contraction arise primarily as a result of the bond topology, with all three
(110) surfaces showing similar behavior.Comment: 13 pages, in revtex format, plus 1 postscript figur
Recent glitches detected in the Crab pulsar
From 2000 to 2010, monitoring of radio emission from the Crab pulsar at
Xinjiang Observatory detected a total of nine glitches. The occurrence of
glitches appears to be a random process as described by previous researches. A
persistent change in pulse frequency and pulse frequency derivative after each
glitch was found. There is no obvious correlation between glitch sizes and the
time since last glitch. For these glitches and
span two orders of magnitude. The pulsar suffered the
largest frequency jump ever seen on MJD 53067.1. The size of the glitch is
6.8 Hz, 3.5 times that of the glitch occured in
1989 glitch, with a very large permanent changes in frequency and pulse
frequency derivative and followed by a decay with time constant 21 days.
The braking index presents significant changes. We attribute this variation to
a varying particle wind strength which may be caused by glitch activities. We
discuss the properties of detected glitches in Crab pulsar and compare them
with glitches in the Vela pulsar.Comment: Accepted for publication in Astrophysics & Space Scienc
Spatial and temporal modulation of cell instructive cues in a filamentous supramolecular biomaterial
Supramolecular materials provide unique opportunities to mimic both the structure and mechanics of the biopolymer networks that compose the extracellular matrix. However, strategies to modify their filamentous structures in space and time in 3D cell culture to study cell behavior as encountered in development and disease are lacking. We herein disclose a multicomponent squaramide-based supramolecular material whose mechanics and bioactivity can be controlled by light through co-assembly of a 1,2-dithiolane (DT) monomer that forms disulfide cross-links. Remarkably, increases in storage modulus from âŒ200 Pa to >10 kPa after stepwise photo-cross-linking can be realized without an initiator while retaining colorlessness and clarity. Moreover, viscoelasticity and plasticity of the supramolecular networks decrease upon photo-irradiation, reducing cellular protrusion formation and motility when performed at the onset of cell culture. When applied during 3D cell culture, force-mediated manipulation is impeded and cells move primarily along earlier formed channels in the materials. Additionally, we show photopatterning of peptide cues in 3D using either a photomask or direct laser writing. We demonstrate that these squaramide-based filamentous materials can be applied to the development of synthetic and biomimetic 3D in vitro cell and disease models, where their secondary cross-linking enables mechanical heterogeneity and shaping at multiple length scales.Toxicolog
Partial Wave Analysis of
BES data on are presented. The
contribution peaks strongly near threshold. It is fitted with a
broad resonance with mass MeV, width MeV. A broad resonance peaking at 2020 MeV is also required
with width MeV. There is further evidence for a component
peaking at 2.55 GeV. The non- contribution is close to phase
space; it peaks at 2.6 GeV and is very different from .Comment: 15 pages, 6 figures, 1 table, Submitted to PL
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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