202 research outputs found
Elastic model scale and material for underwater structure of cross-sea bridge
With the bridge construction gradually from inland to coast and offshore, underwater structure of cross-sea bridge can encounter more complex hydrodynamic action. When elastic model is used to simulate the hydrodynamic response of underwater structure, the model scale and model material is the first problem must be solved. Based on principle of similitude, elastic model should meet the geometric similarity, kinematic similarity and mechanical similarity. Formula derivation gives the scale conditions for elastic model are as follows, geometric scale (Lr) equals elastic modulus scale (Er) and density scale (??r) equals 1. Then, how to find a material with same density and the elastic modulus is 1/ Lr of prototype is the key to make a model
Lightest scalars as chiral partners of the Nambu--Goldstone bosons
We review the spectrum of lightest scalar resonances recently determined
using dispersion techniques. The conceptual difference between the pole mass
and the bare mass (or the line--shape mass) is stressed. The nature of the
lightest scalars are discussed and we argue, without relying on any model
details, that the , , and may
be understood as chiral partners of the Nambu--Goldstone bosons in the linear
realization of chiral symmetry. But there remains some difficulties in
understanding the role of in this picture.Comment: Invited talk given by Zheng at QCD06, Montpellier, France, July 3--7,
200
An improved study of the kappa resonance and the non-exotic wave scatterings up to GeV of LASS data
We point out that the dispersion relation for the left hand cut integral
presented in one of our previous paper (Nucl. Phys. {\bf A}733(2004)235) is
actually free of subtraction constant, even for unequal mass elastic
scatterings. A new fit to the LASS data~\cite{Aston} is performed and firm
evidence for the existence of pole is found. The correct use of
analyticity also put strong constraints on threshold parameters -- which are
found to be in good agreement with those obtained from chiral theories. We also
determined the pole parameters of on the second sheet, and
reconfirm the existence of on the third sheet. We stress that the
LASS data do not require them to have the twin pole structure of a typical
Breit--Wigner resonance.Comment: 14 pages + 4 postscript figures; discussions largely expanded;
references added; version to appear in NPA; title changed in the journa
extension of the large-- partial wave dispersion relations
Continuing our previous work(JHEP 0706:030,2007), large-- techniques and
partial wave dispersion relations are used to discuss scattering
amplitudes. We get a set of predictions for low-energy chiral
perturbation theory couplings. They are provided in terms of the masses and
decay widths of scalar and vector mesons.Comment: 7 page
Pion-nucleon elastic scattering amplitude within covariant baryon chiral perturbation theory up to level
The calculation on pion-nucleon elastic scattering amplitude in EOMS
scheme within covariant baryon chiral perturbation theory is reviewed.
Numerical fits to partial wave amplitudes up to GeV and 1.20
GeV are performed and the results are compared with previous studies.Comment: Talk given by D. L. Yao at QCD2012, July 2- 7, Montpellier, Franc
The Constraints of Unitary on Scattering Dispersion Relations
A new dispersion relation for the partial wave scattering matrix
is set up. Using the dispersion relation we generalize the single channel
unitarity condition, , to the entire complex plane, which is
equivalent to the generalized unitarity condition in quantum mechanics. The
pole positions of the resonance and the resonance are
estimated based on the theoretical relations we obtained. The central value of
the pole position is MeV, MeV, obtained after including the the constraint of the Adler zero
condition.Comment: 10 pages with 4 figures, revised version to appear in Phys. Lett.
The resonance in s wave scatterings
A new unitarization approach incorporated with chiral symmetry is established
and applied to study the elastic scatterings. We demonstrate that the
resonance exists, if the scattering length parameter in the I=1/2, J=0
channel does not deviate much from its value predicted by chiral perturbation
theory. The mass and width of the resonance is found to be
, , obtained by fitting the
LASS data up to 1430MeV. Better determination to the pole parameters is
possible if the chiral predictions on scattering lengths are taken into
account.Comment: Minor corrections made on discussions and typos. 1 ref. added version
to appear in Nuclear Physics
Ambiversion of X(3872)
An analysis including most recent Belle data on X(3872) is performed, using
coupled channel Flatt\'e formula. A third sheet pole close to but
\textit{below} threshold is found, besides the bound state/virtual
state pole discussed in previous literature. The co-existence of two poles near
the threshold indicates that the X(3872) may be of ordinary state origin, distorted by strong coupled channel effects. The
latter manifests itself as a molecular bound state (or a virtual state).Comment: Slightly revised version accepted for publication in Physics Letter
Application of the finite-temperature Lanczos method for the evaluation of magnetocaloric properties of large magnetic molecules
We discuss the magnetocaloric properties of gadolinium containing magnetic
molecules which potentially could be used for sub-Kelvin cooling. We show that
a degeneracy of a singlet ground state could be advantageous in order to
support adiabatic processes to low temperatures and simultaneously minimize
disturbing dipolar interactions. Since the Hilbert spaces of such spin systems
assume very large dimensions we evaluate the necessary thermodynamic
observables by means of the Finite-Temperature Lanczos Method.Comment: 7 pages, 10 figures, invited for the special issue of EPJB on "New
trends in magnetism and magnetic materials
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