8,221 research outputs found
Edge excitations and Topological orders in rotating Bose gases
The edge excitations and related topological orders of correlated states of a
fast rotating Bose gas are studied. Using exact diagonalization of small
systems, we compute the energies and number of edge excitations, as well as the
boson occupancy near the edge for various states. The chiral Luttinger-liquid
theory of Wen is found to be a good description of the edges of the bosonic
Laughlin and other states identified as members of the principal Jain sequence
for bosons. However, we find that in a harmonic trap the edge of the state
identified as the Moore-Read (Pfaffian) state shows a number of anomalies. An
experimental way of detecting these correlated states is also discussed.Comment: Results extended to larger systems. Improved presentatio
Study of the 2-d CP(N-1) models at \theta=0 and \pi
We present numerical results for 2-d CP(N-1) models at \theta=0 and \pi
obtained in the D-theory formulation. In this formulation we construct an
efficient cluster algorithm and we show numerical evidence for a first order
transition for CP(N-1\geq 2) models at \theta = \pi. By a finite size scaling
analysis, we also discuss the equivalence in the continuum limit of the
D-theory formulation of the 2-d CP(N-1) models and the usual lattice
definition.Comment: 3 pages, 2 figures. Talk presented at Lattice2004(spin), Fermilab,
June 21-26, 200
Multiplet Effects in the Quasiparticle Band Structure of the Anderson Model
In this paper, we examine the mean field electronic structure of the
Anderson lattice model in a slave boson approximation, which should
be useful in understanding the physics of correlated metals with more than one
f electron per site such as uranium-based heavy fermion superconductors. We
find that the multiplet structure of the ion acts to quench the crystal
field splitting in the quasiparticle electronic structure. This is consistent
with experimental observations in such metals as .Comment: 9 pages, revtex, 3 uuencoded postscript figures attached at en
Conductance oscillations in strongly correlated fractional quantum Hall line junctions
We present a detailed theory of transport through line junctions formed by
counterpropagating single-branch fractional-quantum-Hall edge channels having
different filling factors. Intriguing transport properties are exhibited when
strong Coulomb interactions between electrons from the two edges are present.
Such strongly correlated line junctions can be classified according to the
value of an effective line-junction filling factor n that is the inverse of an
even integer. Interactions turn out to affect transport most importantly for
n=1/2 and n=1/4. A particularly interesting case is n=1/4 corresponding to,
e.g., a junction of edge channels having filling factor 1 and 1/5,
respectively. We predict its differential tunneling conductance to oscillate as
a function of voltage. This behavior directly reflects the existence of novel
Majorana-fermion quasiparticle excitations in this type of line junction.
Experimental accessibility of such systems in current cleaved-edge overgrown
samples enables direct testing of our theoretical predictions.Comment: 2 figures, 10 pages, RevTex4, v2: added second figure for clarit
A Monte Carlo study of O(3) antiferromagnetic models in three dimensions
We study three antiferromagnetic formulations of the O(3) spin model in three
dimensions by means of Monte Carlo simulations: 1. a two parameter
model with nearest and next to nearest neighbors couplings in a cubic lattice;
2. a face centered cubic lattice with nearest neighbors interaction; 3. a cubic
lattice with a set of fully frustrating couplings. We discuss in all cases the
vacua properties and analyze the phase transitions. Using Finite Size Scaling
analysis we conclude that all phase transitions found are of first order.Comment: 24 pages, uuencoded gzipped postscript file. 13 figures include
Shape oscillation of a rotating Bose-Einstein condensate
We present a theoretical and experimental analysis of the transverse monopole
mode of a fast rotating Bose-Einstein condensate. The condensate's rotation
frequency is similar to the trapping frequency and the effective confinement is
only ensured by a weak quartic potential. We show that the non-harmonic
character of the potential has a clear influence on the mode frequency, thus
making the monopole mode a precise tool for the investigation of the fast
rotation regime
Degeneracies in the length spectra of metric graphs
The spectral theory of quantum graphs is related via an exact trace formula
with the spectrum of the lengths of periodic orbits (cycles) on the graphs. The
latter is a degenerate spectrum, and understanding its structure (i.e.,finding
out how many different lengths exist for periodic orbits with a given period
and the average number of periodic orbits with the same length) is necessary
for the systematic study of spectral fluctuations using the trace formula. This
is a combinatorial problem which we solve exactly for complete (fully
connected) graphs with arbitrary number of vertices.Comment: 13 pages, 7 figure
X-ray and UV observations of nova V598 Puppis between 147 and 255 days after outburst
Aims: The launch of Swift has allowed many more novae to be observed
regularly over the X-ray band. Such X-ray observations of novae can reveal
ejecta shocks and the nuclear burning white dwarf, allowing estimates to be
made of the ejecta velocity. Methods: We analyse XMM-Newton and Swift X-ray and
UV observations of the nova V598 Pup, which was initially discovered in the
XMM-Newton slew survey. These data were obtained between 147 and 255 days after
the nova outburst, and are compared with the earlier, brighter slew detection.
Results: The X-ray spectrum consists of a super-soft source, with the soft
emission becoming hotter and much fainter between days ~147 and ~172 after the
outburst, and a more slowly declining optically thin component, formed by
shocks with kT ~ 200-800 eV (corresponding to velocities of 400-800 km s^-1).
The main super-soft phase had a duration of less than 130 days. The Reflection
Grating Spectrometer data show evidence of emission lines consistent with
optically thin emission of kT ~100 eV and place a limit on the density of the
surrounding medium of log(n_e/cm^-3) < 10.4 at the 90 % level. The UV emission
is variable over short timescales and fades by at least one magnitude (at
lambda ~ 2246-2600 angstrom) between days 169 and 255.Comment: 6 pages, 5 figures, accepted for publication in A&
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