167 research outputs found
Accurate Modelling of Left-Handed Metamaterials Using Finite-Difference Time-Domain Method with Spatial Averaging at the Boundaries
The accuracy of finite-difference time-domain (FDTD) modelling of left-handed
metamaterials (LHMs) is dramatically improved by using an averaging technique
along the boundaries of LHM slabs. The material frequency dispersion of LHMs is
taken into account using auxiliary differential equation (ADE) based dispersive
FDTD methods. The dispersive FDTD method with averaged permittivity along the
material boundaries is implemented for a two-dimensional (2-D) transverse
electric (TE) case. A mismatch between analytical and numerical material
parameters (e.g. permittivity and permeability) introduced by the time
discretisation in FDTD is demonstrated. The expression of numerical
permittivity is formulated and it is suggested to use corrected permittivity in
FDTD simulations in order to model LHM slabs with their desired parameters. The
influence of switching time of source on the oscillation of field intensity is
analysed. It is shown that there exists an optimum value which leads to fast
convergence in simulations.Comment: 17 pages, 7 figures, submitted to Journal of Optics A Nanometa
special issu
Development and irradiation test of lost alpha detection system for ITER
We developed a lost alpha detection system to use in burning plasma experiments. The scintillators of Ag:ZnS and polycrystalline Ce:YAG were designed for a high-temperature environment, and the optical transmission line was designed to transmit from the scintillator to the port plug. The required optical components of lenses and mirrors were irradiated using the fission reactor with the initial result that there was no clear change after the irradiation with a neutron flux of 9.6×1017?nm?2?s?1 for 48 h. We propose a diagnostic of alpha particle loss, so-called alpha particle induced gamma ray spectroscopy. The initial laboratory test has been carried out by the use of the Ce doped Lu2SiO5 scintillator detector and an Am?Be source to detect the 4.44 MeV high energy gamma ray due to the 9Be(α,nγ)12C reaction
Phase diagrams in the Hadron-PNJL model
The two-Equation of State (Two-EoS) model is used to describe the
hadron-quark phase transition in dense-hot matter formed in heavy-ion
collisions. The non-linear Walecka model is used to describe the hadronic
phase. For the quark phase, the Nambu--Jona-Lasinio model coupled to
Polyakov-Loop fields (PNJL) is used to include both the chiral and
(de)confinement dynamics. The phase diagrams are derived from the Gibbs
conditions and compared with the results obtained in the Hadron-NJL model
without confinement. As in the Hadron-NJL case a first order transition is
observed, but with a Critical-End-Point at much higher temperature, consequence
of the confinement mechanism that reduces the degrees of freedom of the quark
matter in proximity of the phase transition. Particular attention is devoted to
the phase transition in isospin asymmetric matter. Interesting isospin effects
are found at high baryon density and reduced temperatures, in fact common also
to other quark models, like MIT-Bag and NJL model. Some possible observation
signals are suggested to probe in Heavy-Ion Collision (HIC) experiments at
intermediate energies.Comment: 11 pages, 10 figures (revtex4
Eight-quark interactions as a chiral thermometer
A NJL Lagrangian extended to six and eight quark interactions is applied to
study temperature effects (SU(3) flavor limit, massless case), and (realistic
massive case). The transition temperature can be considerably reduced as
compared to the standard approach, in accordance with recent lattice
calculations. The mesonic spectra built on the spontaneously broken vacuum
induced by the 't Hooft interaction strength, as opposed to the commonly
considered case driven by the four-quark coupling, undergoes a rapid crossover
to the unbroken phase, with a slope and at a temperature which is regulated by
the strength of the OZI violating eight-quark interactions. This strength can
be adjusted in consonance with the four-quark coupling and leaves the spectra
unchanged, except for the sigma meson mass, which decreases. A first order
transition behavior is also a possible solution within the present approach.Comment: 4 pages, 4 figures, prepared for the proceedings of Quark Matter 2008
- 20th International Conference on Ultra-Relativistic Nucleus Nucleus
Collisions, February 4-10, Jaipur (India
Equation of state in the PNJL model with the entanglement interaction
The equation of state and the phase diagram in two-flavor QCD are
investigated by the Polyakov-loop extended Nambu--Jona-Lasinio (PNJL) model
with an entanglement vertex between the chiral condensate and the
Polyakov-loop. The entanglement-PNJL (EPNJL) model reproduces LQCD data at zero
and finite chemical potential better than the PNJL model. Hadronic degrees of
freedom are taken into account by the free-hadron-gas (FHG) model with the
volume-exclusion effect due to the hadron generation. The EPNJL+FHG model
improves agreement of the EPNJL model with LQCD data particularly at small
temperature. The quarkyonic phase survives, even if the correlation between the
chiral condensate and the Polyakov loop is strong and hadron degrees of freedom
are taken into account. However, the location of the quarkyonic phase is
sensitive to the strength of the volume exclusion.Comment: 9 pages, 7 figure
Effect of Dynamical SU(2) Gluons to the Gap Equation of Nambu--Jona-Lasinio Model in Constant Background Magnetic Field
In order to estimate the effect of dynamical gluons to chiral condensate, the
gap equation of SU(2) gauged Nambu--Jona-Lasinio model, under a constant
background magnetic field, is investigated up to the two-loop order in 2+1 and
3+1 dimensions. We set up a general formulation allowing both cases of electric
as well as magnetic background field. We rely on the proper time method to
maintain gauge invariance. In 3+1 dimensions chiral symmetry breaking
(SB) is enhanced by gluons even in zero background magnetic field and
becomes much striking as the background field grows larger. In 2+1 dimensions
gluons also enhance SB but whose dependence on the background field is
not simple: dynamical mass is not a monotone function of background field for a
fixed four-fermi coupling.Comment: 20 pages, 5 figure
New Gauge Invariant Formulation of the Chern-Simons Gauge Theory
A new gauge invariant formulation of the relativistic scalar field
interacting with Chern-Simons gauge fields is considered. This formulation is
consistent with the gauge fixed formulation. Furthermore we find that canonical
(Noether) Poincar\'e generators are not gauge invariant even on the constraints
surface and do not satisfy the (classical) Poincar\'e algebra. It is the
improved generators, constructed from the symmetric energy-momentum tensor,
which are (manifestly) gauge invariant and obey the classical Poincar\'e
algebra.Comment: Shortened, to appear as Papid Communication-PRD/Nov/9
- …