308 research outputs found
Annihilation Diagrams in Two-Body Nonleptonic Decays of Charmed Mesons
In the pole-dominance model for the two-body nonleptonic decays of charmed
mesons and , it is shown that the
contributions of the intermediate pseudoscalar and the axial-vector meson poles
cancel each other in the annihilation diagrams in the chiral limit. In the same
limit, the annihilation diagrams for the decays vanish
independently.Comment: 9 pages (+ 3 figures available upon request), UR-1316, ER-40685-766,
IC/93/21
Superfluid to Mott insulator transition in the one-dimensional Bose-Hubbard model for arbitrary integer filling factors
We study the quantum phase transition between the superfluid and the Mott
insulator in the one-dimensional (1D) Bose-Hubbard model. Using the
time-evolving block decimation method, we numerically calculate the tunneling
splitting of two macroscopically distinct states with different winding
numbers. From the scaling of the tunneling splitting with respect to the system
size, we determine the critical point of the superfluid to Mott insulator
transition for arbitrary integer filling factors. We find that the critical
values versus the filling factor in 1D, 2D, and 3D are well approximated by a
simple analytical function. We also discuss the condition for determining the
transition point from a perspective of the instanton method.Comment: 6 pages, 6 figures, 2 table
Bulk and edge excitations of a Hall ferromagnet
In this article, we shall focus on the collective dynamics of the fermions in
a quantum Hall droplet. Specifically, we propose to look at the
quantum Hall ferromagnet. In this system, the electron spins are ordered in the
ground state due to the exchange part of the Coulomb interaction and the Pauli
exclusion principle. The low energy excitations are ferromagnetic magnons. In
order to obtain an effective Lagrangian for these magnons, we shall introduce
bosonic collective coordinates in the Hilbert space of many-fermion systems.
These collective coordinates describe a part of the fermionic Hilbert space.
Using this technique, we shall interpret the magnons as bosonic collective
excitations in the Hilbert space of the many-electron Hall system. Furthermore,
by considering a Hall droplet of finite extent, we shall also obtain the
effective Lagrangian governing the spin collective excitations at the edge of
the sample.Comment: 30 pages, plain TeX, no figure
A path integral derivation of -genus
The formula for the Hirzebruch -genus of complex manifolds is a
consequence of the Hirzebruch-Riemann-Roch formula. The classical index
formulae for Todd genus, Euler number, and Signature correspond to the case
when the complex variable 0, -1, and 1 respectively. Here we give a {\it
direct} derivation of this nice formula based on supersymmetric quantum
mechanics.Comment: 5 page
Quantum Hydrodynamics, Quantum Benjamin-Ono Equation, and Calogero Model
Collective field theory for Calogero model represents particles with
fractional statistics in terms of hydrodynamic modes -- density and velocity
fields. We show that the quantum hydrodynamics of this model can be written as
a single evolution equation on a real holomorphic Bose field -- quantum
integrable Benjamin-Ono equation. It renders tools of integrable systems to
studies of nonlinear dynamics of 1D quantum liquids.Comment: 5 pages, 1 figur
Accurate numerical verification of the instanton method for macroscopic quantum tunneling: dynamics of phase slips
Instanton methods, in which imaginary-time evolution gives the tunneling
rate, have been widely used for studying quantum tunneling in various contexts.
Nevertheless, how accurate instanton methods are for the problems of
macroscopic quantum tunneling (MQT) still remains unclear because of lack of
their direct comparison with exact time evolution of the many-body Schroedinger
equation. Here, we verify instanton methods applied to coherent MQT.
Specifically applying the quasi-exact numerical method of time-evolving block
decimation to the system of bosons in a ring lattice, we directly simulate the
real-time quantum dynamics of supercurrents, where a coherent oscillation
between two macroscopically distinct current states occurs due to MQT. The
tunneling rate extracted from the coherent oscillation is compared with that
given by the instanton method. We show that the error is within 10% when the
effective Planck's constant is sufficiently small. We also discuss phase slip
dynamics associated with the coherent oscillations.Comment: 19 pages, 14 figures, 1 tabl
Production of e+e- pairs in proton-deuteron capture to 3He
The process p+d \leftrightarrow 3He + \gamma* at intermediate energies is
described using a covariant and gauge-invariant model, and a realistic pd3He
vertex. Both photodisintegration of 3He and proton-deuteron capture with
production of e+e- pairs are studied, and results for cross sections and
response functions are presented. The effect of time-like formfactors on the
dilepton cross sections is investigated as well.Comment: 10 pages, 4 figures, Revtex, to be published in Physics Letters
Chern-Simons matrix model: coherent states and relation to Laughlin wavefunctions
Using a coherent state representation we derive many-body probability
distributions and wavefunctions for the Chern-Simons matrix model proposed by
Polychronakos and compare them to the Laughlin ones. We analyze two different
coherent state representations, corresponding to different choices for electron
coordinate bases. In both cases we find that the resulting probability
distributions do not quite agree with the Laughlin ones. There is agreement on
the long distance behavior, but the short distance behavior is different.Comment: 15 pages, LaTeX; one reference added, abstract and section 5
expanded, typos correcte
Soliton solutions of Calogero model in harmonic potential
A classical Calogero model in an external harmonic potential is known to be
integrable for any number of particles. We consider here reductions which play
a role of "soliton" solutions of the model. We obtain these solutions both for
the model with finite number of particles and in a hydrodynamic limit. In the
latter limit the model is described by hydrodynamic equations on continuous
density and velocity fields. Soliton solutions in this case are finite
dimensional reductions of the hydrodynamic model and describe the propagation
of lumps of density and velocity in the nontrivial background.Comment: 25 pages, 2 figure
Fluctuation effects of gauge fields in the slave-boson t-J model
We present a quantitative study of the charge-spin separation(CSS) phenomenon
in a U(1) gauge theory of the t-J model of high-Tc superconductures. We
calculate the critical temperature of confinement-deconfinement phase
transition below which the CSS takes place.Comment: Latex, 9 pages, 3 figure
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