15,894 research outputs found
Hamiltonian formulation of SL(3) Ur-KdV equation
We give a unified view of the relation between the KdV, the mKdV, and
the Ur-KdV equations through the Fr\'{e}chet derivatives and their inverses.
For this we introduce a new procedure of obtaining the Ur-KdV equation, where
we require that it has no non-local operators. We extend this method to the
KdV equation, i.e., Boussinesq(Bsq) equation and obtain the hamiltonian
structure of Ur-Bsq equationin a simple form. In particular, we explicitly
construct the hamiltonian operator of the Ur-Bsq system which defines the
poisson structure of the system, through the Fr\'{e}chet derivative and its
inverse.Comment: 12 pages, KHTP-93-03 SNUTP-93-2
Behavior of tachyon in string cosmology based on gauged WZW model
We investigate a string theoretic cosmological model in the context of the
gauged Wess-Zumino-Witten model. Our model is based on a product of non-compact
coset space and a spectator flat space; . We
extend the formerly studied semiclassical consideration with infinite Kac-Moody
level to a finite one. In this case, the tachyon field appears in the
effective action, and we solve the Einstein equation to determine the behavior
of tachyon as a function of time. We find that tachyon field dominates over
dilaton field in early times. In particular, we consider the energy conditions
of the matter fields consisting of the dilaton and the tachyon which affect the
initial singularity. We find that not only the strong energy but also the null
energy condition is violated.Comment: 10 figure
Solutions of Conformal Turbulence on a Half Plane
Exact solutions of conformal turbulence restricted on a upper half plane are
obtained. We show that the inertial range of homogeneous and isotropic
turbulence with constant enstrophy flux develops in a distant region from the
boundary. Thus in the presence of an anisotropic boundary, these exact
solutions of turbulence generalize Kolmogorov's solution consistently and
differ from the Polyakov's bulk case which requires a fine tunning of
coefficients. The simplest solution in our case is given by the minimal model
of and moreover we find a fixed point of solutions when
become large.Comment: 10pages, KHTP-93-07, SNUCTP-93-3
Molecular Dynamics Simulation of Ga Penetration along Grain Boundaries in Al: a Dislocation Climb Mechanism
Many systems where a liquid metal is in contact with a polycrystalline solid
exhibit deep liquid grooves where the grain boundary meets the solid-liquid
interface. For example, liquid Ga quickly penetrates deep into grain boundaries
in Al, leading to intergranular fracture under very small stresses. We report
on a series of molecular dynamics simulations of liquid Ga in contact with an
Al bicrystal. We identify the mechanism for liquid metal embrittlement, develop
a new model for it, and show that is in excellent agreement with both
simulation and experimental data
QED corrections to isospin-related decay rates of charged and neutral B mesons
We estimate the isospin-violating QED radiative corrections to the
charged-to-neutral ratios of the decay rates for B^+ and B^0 in non-leptonic B
meson decays. In particular, these corrections are potentially important for
precision measurement of the charged-to-neutral production ratio of B meson in
e^+e^- annihilation. We calculate explicitly the QED corrections to the ratios
of two different types of decay rates \Gamma(B^+ \to J/\psi K^+)/\Gamma(B^0 \to
J/\psi K^0) and \Gamma(B^+ \to D^+_S \bar{D^0})/\Gamma(B^0 \to D^+_S D^-)
taking into account the form factors of the mesons based on the vector meson
dominance model, and compare them with the results obtained for the point-like
mesons.Comment: 7 pages, 9 eps figure
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