119 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
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
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
Chiral Anomaly and Spin Gap in One-Dimensional Interacting Fermions
Semiclassical approach has been developed for the one-dimensional interacting
fermion systems. Starting from the incommensurate spin density wave (SDW) mean
field state for the repulsive Hubbard model in 1D, the non-Abelian bosonized
Lagrangian describing the spin-charge separation is obtained. The Berry phase
term is derived from the chiral anomaly, and we obtain the massless
Tomonaga-Luttinger liquid in the single chain case while the spin gap opens in
the double-chain system. This approach offers a new method to identify the
strong-coupling fixed point, and its relation to the Abelian bosonization
formalism is discussed on the spin gap state. The generalization to higher
dimensions is also discussed.Comment: Revised and enlarged version. 16 pages in REVTE
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
Ultracold Gases of Ytterbium: Ferromagnetism and Mott States in an SU(6) Fermi System
It is argued that ultracold quantum degenerate gas of ytterbium Yb
atoms having nuclear spin exhibits an enlarged SU symmetry.
Within the Landau Fermi liquid theory, stability criteria against Fermi liquid
(Pomeranchuk) instabilities in the spin channel are considered. Focusing on the
SU generalizations of ferromagnetism, it is shown within mean-field
theory that the transition from the paramagnet to the itinerant ferromagnet is
generically first order. On symmetry grounds, general SU itinerant
ferromagnetic ground states and their topological excitations are also
discussed. These SU ferromagnets can become stable by increasing the
scattering length using optical methods or in an optical lattice. However, in
an optical lattice at current experimental temperatures, Mott states with
different filling are expected to coexist in the same trap, as obtained from a
calculation based on the SU Hubbard model.Comment: 4+ pages, 1 figure; v2: Improved discussion of the SU(6)
symmetry-breaking patterns; v3: added further discussion on the order of the
transition. Added Reference
Topological Dislocations and Mixed State of Charge Density Waves
We discuss the possibility of the ``mixed state'' in incommensurate charge
density waves with three-dimensional order. It is shown that the mixed state
can be created by applying an electric field perpendicular to the chains. This
state consists of topological dislocations induced by the external field and is
therefore similar to the mixed states of superfluids (type-II superconductor or
liquid Helium II). However, the peculiar coupling of charge density waves with
the electric field strongly modifies the nature of the mixed state compared to
the conventional superfluids. The field and temperature dependence of the
properties of the mixed state are studied, and some experimental aspects are
discussed.Comment: 10 pages, Revtex format, no figures, to appear in Phys. Rev. Let
Dynamics of waves in 1D electron systems: Density oscillations driven by population inversion
We explore dynamics of a density pulse induced by a local quench in a
one-dimensional electron system. The spectral curvature leads to an "overturn"
(population inversion) of the wave. We show that beyond this time the density
profile develops strong oscillations with a period much larger than the Fermi
wave length. The effect is studied first for the case of free fermions by means
of direct quantum simulations and via semiclassical analysis of the evolution
of Wigner function. We demonstrate then that the period of oscillations is
correctly reproduced by a hydrodynamic theory with an appropriate dispersive
term. Finally, we explore the effect of different types of electron-electron
interaction on the phenomenon. We show that sufficiently strong interaction
[ where is the fermionic mass and the relevant spatial
scale] determines the dominant dispersive term in the hydrodynamic equations.
Hydrodynamic theory reveals crucial dependence of the density evolution on the
relative sign of the interaction and the density perturbation.Comment: 20 pages, 13 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
Stochastic Quantization of Scalar Fields in Einstein and Rindler Spacetime
We consider the stochastic quantization method for scalar fields defined in a
curved manifold and also in a flat space-time with event horizon. The two-point
function associated to a massive self-interacting scalar field is evaluated, up
to the first order level in the coupling constant, for the case of an Einstein
and also a Rindler Euclidean metric, respectively. Its value for the asymptotic
limit of the Markov parameter is exhibited. The divergences therein are taken
care of by employing a covariant stochastic regularization
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