733 research outputs found
Addendum to "Classical and Quantum Evolutions of the de Sitter and the anti-de Sitter Universes in 2+1 dimensions"
The previous discussion \cite{ezawa} on reducing the phase space of the first
order Einstein gravity in 2+1 dimensions is reconsidered. We construct a \lq\lq
correct" physical phase space in the case of positive cosmological constant,
taking into account the geometrical feature of SO(3,1) connections. A
parametrization which unifies the two sectors of the physical phase space is
also given.Comment: Latex 8 pages (Crucial and essential changes have been made.
Phase Transition in \nu=2 Bilayer Quantum Hall State
The Hall-plateau width and the activation energy were measured in the bilayer
quantum Hall state at filling factor \nu=2, 1 and 2/3, by changing the total
electron density and the density ratio in the two quantum wells. Their behavior
are remarkably different from one to another. The \nu=1 state is found stable
over all measured range of the density difference, while the \nu=2/3$ state is
stable only around the balanced point. The \nu=2 state, on the other hand,
shows a phase transition between these two types of the states as the electron
density is changed.Comment: 5 pages including figures, RevTe
Conical Singular Solutions in (2+1)-Dimensional Gravity Employing the ADM Canonical Formalism
Topological solutions in the (2+1)-dimensional Einstein theory of gravity are
studied within the ADM canonical formalism. It is found that a conical
singularity appears in the closed de Sitter universe solution as a topological
defect in the case of the Einstein theory with a cosmological constant. Quantum
effects on the conical singularity are studied using the de Broglie-Bohm
interpretation. Finite quantum tunneling effects are obtained for the closed de
Sitter universe, while no quantum effects are obtained for an open universe.Comment: 15 pages, 3 figure
Collective modes of CP(3) Skyrmion crystals in quantum Hall ferromagnets
The two-dimensional electron gas in a bilayer quantum Hall system can sustain
an interlayer coherence at filling factor nu=1 even in the absence of tunneling
between the layers. This system has low-energy charged excitations which may
carry textures in real spin or pseudospin. Away from filling factor nu =1 a
finite density of these is present in the ground state of the 2DEG and forms a
crystal. Depending on the relative size of the various energy scales, such as
tunneling (Delta_SAS), Zeeman coupling (Delta_Z) or electrical bias (Delta_b),
these textured crystal states can involve spin, pseudospin, or both
intertwined. In this article, we present a comprehensive numerical study of the
collective excitations of these textured crystals using the GRPA. For the pure
spin case, at finite Zeeman coupling the state is a Skyrmion crystal with a
gapless phonon mode, and a separate Goldstone mode that arises from a broken
U(1) symmetry. At zero Zeeman coupling, we demonstrate that the constituent
Skyrmions break up, and the resulting state is a meron crystal with 4 gapless
modes. In contrast, a pure pseudospin Skyrme crystal at finite tunneling has
only the phonon mode. For Delta_SAS=0, the state evolves into a meron crystal
and supports an extra gapless U(1) mode in addition to the phonon. For a CP(3)
Skyrmion crystal, we find a U(1) gapless mode in the presence of the
symmetry-breaking fields. In addition, a second mode with a very small gap is
present in the spectrum.Comment: 16 pages and 12 eps figure
The Study of Goldstone Modes in =2 Bilayer Quantum Hall Systems
At the filling factor =2, the bilayer quantum Hall system has three
phases, the spin-ferromagnet phase, the spin singlet phase and the canted
antiferromagnet (CAF) phase, depending on the relative strength between the
Zeeman energy and interlayer tunneling energy. We present a systematic method
to derive the effective Hamiltonian for the Goldstone modes in these three
phases. We then investigate the dispersion relations and the coherence lengths
of the Goldstone modes. To explore a possible emergence of the interlayer phase
coherence, we analyze the dispersion relations in the zero tunneling energy
limit. We find one gapless mode with the linear dispersion relation in the CAF
phase.Comment: 13 pages, no figures. One reference is added. Typos correcte
Only hybrid anyons can exist in broken symmetry phase of nonrelativistic Chern-Simons theory
We present two examples of parity-invariant Chern-Simons-Higgs
models with spontaneously broken symmetry. The models possess topological
vortex excitations. It is argued that the smallest possible flux quanta are
composites of one quantum of each type . These hybrid anyons will
dominate the statistical properties near the ground state. We analyse their
statistical interactions and find out that unlike in the case of Jackiw-Pi
solitons there is short range magnetic interaction which can lead to formation
of bound states of hybrid anyons. In addition to mutual interactions they
possess internal structure which can lead upon quantisation to discrete
spectrum of energy levels.Comment: 10 pages in plain Latex (one argument added, version accepted for
publication in Phys.Rev.D(Rapid Communications)
Einstein-Infeld-Hoffman method and soliton dynamics in a parity noninvariant system
We consider slow motion of a pointlike topological defect (vortex) in the
nonlinear Schrodinger equation minimally coupled to Chern-Simons gauge field
and subject to external uniform magnetic field. It turns out that a formal
expansion of fields in powers of defect velocity yields only the trivial static
solution. To obtain a nontrivial solution one has to treat velocities and
accelerations as being of the same order. We assume that acceleration is a
linear form of velocity. The field equations linearized in velocity uniquely
determine the linear relation. It turns out that the only nontrivial solution
is the cyclotron motion of the vortex together with the whole condensate. This
solution is a perturbative approximation to the center of mass motion known
from the theory of magnetic translations.Comment: 6 pages in Latex; shortened version to appear in Phys.Rev.
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