265,672 research outputs found
Classification of Multipartite Entanglement via Negativity Fonts
Partial transposition of state operator is a well known tool to detect
quantum correlations between two parts of a composite system. In this letter,
the global partial transpose (GPT) is linked to conceptually multipartite
underlying structures in a state - the negativity fonts. If K-way negativity
fonts with non zero determinants exist, then selective partial transposition of
a pure state, involving K of the N qubits (K leq N) yields an operator with
negative eigevalues, identifying K-body correlations in the state. Expansion of
GPT interms of K-way partially transposed (KPT) operators reveals the nature of
intricate intrinsic correlations in the state. Classification criteria for
multipartite entangled states, based on underlying structure of global partial
transpose of canonical state, are proposed. Number of N-partite entanglement
types for an N qubit system is found to be 2^{N-1}-N+2, while the number of
major entanglement classes is 2^{N-1}-1. Major classes for three and four qubit
states are listed. Subclasses are determined by the number and type of
negativity fonts in canonical state.Comment: 5 pages, No figures, Corrected typo
Domain Wall and Periodic Solutions of Coupled phi4 Models in an External Field
Coupled double well (phi4) one-dimensional potentials abound in both
condensed matter physics and field theory. Here we provide an exhaustive set of
exact periodic solutions of a coupled model in an external field in
terms of elliptic functions (domain wall arrays) and obtain single domain wall
solutions in specific limits. We also calculate the energy and interaction
between solitons for various solutions. Both topological and nontopological
(e.g. some pulse-like solutions in the presence of a conjugate field) domain
walls are obtained. We relate some of these solutions to the recently observed
magnetic domain walls in certain multiferroic materials and also in the field
theory context wherever possible. Discrete analogs of these coupled models,
relevant for structural transitions on a lattice, are also considered.Comment: 35 pages, no figures (J. Math. Phys. 2006
factorization of exclusive processes
We prove factorization theorem in perturbative QCD (PQCD) for exclusive
processes by considering and . The relevant form factors are expressed as the convolution of hard
amplitudes with two-parton meson wave functions in the impact parameter
space, being conjugate to the parton transverse momenta . The point is
that on-shell valence partons carry longitudinal momenta initially, and acquire
through collinear gluon exchanges. The -dependent two-parton wave
functions with an appropriate path for the Wilson links are gauge-invariant.
The hard amplitudes, defined as the difference between the parton-level
diagrams of on-shell external particles and their collinear approximation, are
also gauge-invariant. We compare the predictions for two-body nonleptonic
meson decays derived from factorization (the PQCD approach) and from
collinear factorization (the QCD factorization approach).Comment: 11 pages, REVTEX, 5 figure
Time lag between prompt optical emission and gamma-rays in GRBs
The prompt optical emission contemporaneous with the -rays from
-ray bursts (GRBs) carries important information on the central engine
and explosion mechanism. We study the time lag between prompt optical emission
and -rays in GRB 990123 and GRB 041219a, which are the only two GRBs
had been detected at optical wavelengths during the ascending burst phase.
Assuming profiles of prompt optical light curves are the same as the prompt
-rays, we simulate optical light curves with different time lags and
compare them with the observed optical flux. Then the best fit time lag and its
error are determined by chi-squared values. We find that time lags between
prompt optical emission and -rays in GRB host galaxy rest-frames are
consistent in the two GRBs, which is s for GRB 990123 and s
for GRB 041219a. This result is consistent with a common origin of prompt
optical and -ray emissions in the two GRBs. Based on synchrotron
cooling model, we also derive the parameters for the two GRBs.Comment: 4 pages, 3 figures; accepted for publication in A&
Study of 0- phase transition in hybrid superconductor-InSb nanowire quantum dot devices
Hybrid superconductor-semiconducting nanowire devices provide an ideal
platform to investigating novel intragap bound states, such as the Andreev
bound states (ABSs), Yu-Shiba-Rusinov (YSR) states, and the Majorana bound
states. The competition between Kondo correlations and superconductivity in
Josephson quantum dot (QD) devices results in two different ground states and
the occurrence of a 0- quantum phase transition. Here we report on
transport measurements on hybrid superconductor-InSb nanowire QD devices with
different device geometries. We demonstrate a realization of continuous
gate-tunable ABSs with both 0-type levels and -type levels. This allow us
to manipulate the transition between 0 and junction and explore charge
transport and spectrum in the vicinity of the quantum phase transition regime.
Furthermore, we find a coexistence of 0-type ABS and -type ABS in the same
charge state. By measuring temperature and magnetic field evolution of the
ABSs, the different natures of the two sets of ABSs are verified, being
consistent with the scenario of phase transition between the singlet and
doublet ground state. Our study provides insights into Andreev transport
properties of hybrid superconductor-QD devices and sheds light on the crossover
behavior of the subgap spectrum in the vicinity of 0- transition
Event anisotropy in 4.2A GeV/c C+C collisions
The directed and elliptic flow of protons and negative pions in 4.2A GeV/c
C+C collisions is studied using the Fourier analysis of azimuthal
distributions. It is found that the protons exhibit pronounced directed flow,
while the flow of pions is either non existent or too weak to be detected
experimentally. Also, it is found that in the entire rapidity interval the
elliptic flow is very small if not zero. These results are confirmed by the
Quark-Gluon-String Model (QGSM) and the relativistic transport model (ART 1.0),
except that these models predict very weak antiflow of pions. The more detailed
comparison with the QGSM suggests that the decay of resonances and rescattering
of secondaries dominantly determine the proton and negative pion flow at this
energy.Comment: 7 pages, 3 figures, TeX file changed from double to single-spacin
Temperature dependence of thermal conductivity in 1D nonlinear lattices
We examine the temperature dependence of thermal conductivity of one
dimensional nonlinear (anharmonic) lattices with and without on-site potential.
It is found from computer simulation that the heat conductivity depends on
temperature via the strength of nonlinearity. Based on this correlation, we
make a conjecture in the effective phonon theory that the mean-free-path of the
effective phonon is inversely proportional to the strength of nonlinearity. We
demonstrate analytically and numerically that the temperature behavior of the
heat conductivity is not universal for 1D harmonic lattices
with a small nonlinear perturbation. The computer simulations of temperature
dependence of heat conductivity in general 1D nonlinear lattices are in good
agreements with our theoretic predictions. Possible experimental test is
discussed.Comment: 6 pages and 2 figures. Accepted for publication in Europhys. Let
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