19,386 research outputs found
On the nature of the lightest scalar resonances
We briefly review the recent progresses in the new unitarization approach
being developed by us. Especially we discuss the large
scatterings by making use of the partial wave matrix parametrization form.
We find that the pole may move to the negative real axis on the second
sheet of the complex plane, therefore it raises the interesting question
that this `' pole may be related to the in the linear
model.Comment: Talk presented by Zheng at ``Quark Confinement and Hadron
Spectroscopy VI'', 21--25 Sept. 2004, Cagliari, Italy. 3 pages with 2 figure
Surface Impedance and Bulk Band Geometric Phases in One-Dimensional Systems
Surface impedance is an important concept in classical wave systems such as
photonic crystals (PCs). For example, the condition of an interface state
formation in the interfacial region of two different one-dimensional PCs is
simply Z_SL +Z_SR=0, where Z_SL (Z_SR)is the surface impedance of the
semi-infinite PC on the left- (right-) hand side of the interface. Here, we
also show a rigorous relation between the surface impedance of a
one-dimensional PC and its bulk properties through the geometrical (Zak) phases
of the bulk bands, which can be used to determine the existence or
non-existence of interface states at the interface of the two PCs in a
particular band gap. Our results hold for any PCs with inversion symmetry,
independent of the frequency of the gap and the symmetry point where the gap
lies in the Brillouin Zone. Our results provide new insights on the
relationship between surface scattering properties, the bulk band properties
and the formation of interface states, which in turn can enable the design of
systems with interface states in a rational manner
Analyticity and the counting rule of matrix poles
By studying scattering amplitudes in the large limit, we
clarify the dependence of the matrix pole position. It is
demonstrated that analyticity and the counting rule exclude the existence
of matrix poles with . Especially the properties
of and with respect to the expansion are discussed.
We point out that in general tetra-quark resonances do not exist.Comment: This paper replaces hep-ph/0412175. The latter is withdraw
Excitation of nonlinear ion acoustic waves in CH plasmas
Excitation of nonlinear ion acoustic wave (IAW) by an external electric field
is demonstrated by Vlasov simulation. The frequency calculated by the
dispersion relation with no damping is verified much closer to the resonance
frequency of the small-amplitude nonlinear IAW than that calculated by the
linear dispersion relation. When the wave number increases,
the linear Landau damping of the fast mode (its phase velocity is greater than
any ion's thermal velocity) increases obviously in the region of in which the fast mode is weakly damped mode. As a result, the deviation
between the frequency calculated by the linear dispersion relation and that by
the dispersion relation with no damping becomes larger with
increasing. When is not large, such as , the nonlinear IAW can be excited by the driver with the linear frequency
of the modes. However, when is large, such as
, the linear frequency can not be applied to exciting the
nonlinear IAW, while the frequency calculated by the dispersion relation with
no damping can be applied to exciting the nonlinear IAW.Comment: 10 pages, 9 figures, Accepted by POP, Publication in August 1
Recent Developments In Computational Fracture Mechanics At Cardiff
The following most recent developments in computational fracture mechanics at Cardiff University are reviewed: hybrid crack element (HCE) which can give directly the stress intensity factor (SIF) as well as the coefficients of higher order terms in the plane linear elastic crack tip asymptotic field; extended finite element method (XFEM) which avoids using a mesh conforming with the crack as is the case with the traditional FEM and gives highly accurate crack tip fields; penalty function technique for handling point loads; and compressed sparse row (CSR) storage scheme for efficient implementation of the above techniques. Possible future improvements are also discussed
Is the meson a dynamically generated resonance? -- a lesson learned from the O(N) model and beyond
O(N) linear model is solvable in the large limit and hence
provides a useful theoretical laboratory to test various unitarization
approximations. We find that the large limit and the
limit do not commute. In order to get the correct large spectrum one has
to firstly take the large limit. We argue that the meson may
not be described as generated dynamically. On the contrary, it is most
appropriately described at the same level as the pions, i.e, both appear
explicitly in the effective lagrangian. Actually it is very likely the
meson responsible for the spontaneous chiral symmetry breaking in a lagrangian
with linearly realized chiral symmetry.Comment: 15 pages, 3 figurs; references added; discussions slightly modified;
revised version accepted by IJMP
Anti-Stokes scattering and Stokes scattering of stimulated Brillouin scattering cascade in high-intensity laser-plasmas interaction
The anti-Stokes scattering and Stokes scattering in stimulated Brillouin
scattering (SBS) cascade have been researched by the Vlasov-Maxwell simulation.
In the high-intensity laser-plasmas interaction, the stimulated anti-Stokes
Brillouin scattering (SABS) will occur after the second stage SBS rescattering.
The mechanism of SABS has been put forward to explain this phenomenon. And the
SABS will compete with the SBS rescattering to determine the total SBS
reflectivity. Thus, the SBS rescattering including the SABS is an important
saturation mechanism of SBS, and should be taken into account in the
high-intensity laser-plasmas interaction.Comment: 6 pages, 5 figure
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