46,050 research outputs found
Baryon states with open charm in the extended local hidden gauge approach
In this paper we examine the interaction of and states,
together with their coupled channels, by using an extension of the local hidden
gauge formalism from the light meson sector, which is based on heavy quark spin
symmetry. The scheme is based on the use of the impulse approximation at the
quark level, with the heavy quarks acting as spectators, which occurs for the
dominant terms where there is the exchange of a light meson. The pion exchange
and the Weinberg-Tomozawa interactions are generalized and with this dynamics
we look for states generated from the interaction, with a unitary coupled
channels approach that mixes the pseudoscalar-baryon and vector-baryon states.
We find two states with nearly zero width which are associated to the
and . The lower state, with ,
couples to and , and the second one, with , to . In addition to these two states, we find four more states with
, one of them nearly degenerate in two states of .
Furthermore we find three states in , two of them degenerate in .Comment: v3: version to appear in Eur.Phys.J.
Description of as a system with the fixed center approximation
We study the system with an aim to describe the
resonance. The chiral unitary approach has achieved success in a description of
systems of the light hadron sector. With this method, the system in
the isospin sector , is found to be a dominant component of the resonance. Therefore, by regarding the system as a cluster,
the resonance, we evaluate the system applying the
fixed center approximation to the Faddeev equations. We construct the
unitarized amplitude using the chiral unitary approach. As a result, we find a
peak in the three-body amplitude around 1739 MeV and a width of about 227 MeV.
The effect of the width of and is also discussed. We
associate this peak to the which has a mass of MeV
and a width of MeV
Spatially Distributed Stochastic Systems: equation-free and equation-assisted preconditioned computation
Spatially distributed problems are often approximately modelled in terms of
partial differential equations (PDEs) for appropriate coarse-grained quantities
(e.g. concentrations). The derivation of accurate such PDEs starting from finer
scale, atomistic models, and using suitable averaging, is often a challenging
task; approximate PDEs are typically obtained through mathematical closure
procedures (e.g. mean-field approximations). In this paper, we show how such
approximate macroscopic PDEs can be exploited in constructing preconditioners
to accelerate stochastic simulations for spatially distributed particle-based
process models. We illustrate how such preconditioning can improve the
convergence of equation-free coarse-grained methods based on coarse
timesteppers. Our model problem is a stochastic reaction-diffusion model
capable of exhibiting Turing instabilities.Comment: 8 pages, 6 figures, submitted to Journal of Chemical Physic
Spin-dependent transport in a quasiballistic quantum wire
We describe the transport properties of a 5 m long one-dimensional (1D)
quantum wire. Reduction of conductance plateaux due to the introduction of
weakly disorder scattering are observed. In an in-plane magnetic field, we
observe spin-splitting of the reduced conductance steps. Our experimental
results provide evidence that deviation from conductance quantisation is very
small for electrons with spin parallel and is about 1/3 for electrons with spin
anti-parallel. Moreover, in a high in-plane magnetic field, a spin-polarised 1D
channel shows a plateau-like structure close to which
strengthens with {\em increasing} temperatures. It is suggested that these
results arise from the combination of disorder and the electron-electron
interactions in the 1D electron gas.Comment: 4 pages, 5 figures, latex to be published in Phys. Rev. B (15/3/2000
Recommended from our members
The effects of economic transformation upon selected high school vocational education programs in Southern California
Deterministic Quantum Key Distribution Using Gaussian-Modulated Squeezed States
A continuous variable ping-pong scheme, which is utilized to generate
deterministically private key, is proposed. The proposed scheme is implemented
physically by using Gaussian-modulated squeezed states. The deterministic way,
i.e., no basis reconciliation between two parties, leads a two-times efficiency
comparing to the standard quantum key distribution schemes. Especially, the
separate control mode does not need in the proposed scheme so that it is
simpler and more available than previous ping-pong schemes. The attacker may be
detected easily through the fidelity of the transmitted signal, and may not be
successful in the beam splitter attack strategy.Comment: 7 pages, 4figure
- …