620 research outputs found
Distinguishing multi-partite states by local measurements
We analyze the distinguishability norm on the states of a multi-partite
system, defined by local measurements. Concretely, we show that the norm
associated to a tensor product of sufficiently symmetric measurements is
essentially equivalent to a multi-partite generalisation of the non-commutative
2-norm (aka Hilbert-Schmidt norm): in comparing the two, the constants of
domination depend only on the number of parties but not on the Hilbert spaces
dimensions.
We discuss implications of this result on the corresponding norms for the
class of all measurements implementable by local operations and classical
communication (LOCC), and in particular on the leading order optimality of
multi-party data hiding schemes.Comment: 18 pages, 6 figures, 1 unreferenced referenc
Hydrodynamic Approach to Vortex Lifetime in Trapped Bose Condensates
We study a vortex in a two-dimensional, harmonically trapped Bose-Einstein
condensate at zero temperature. Through a variational calculation using a trial
condensate wave function and a nonlinear Schroedinger Lagrangian, we obtain the
effective potential experienced by a vortex at an arbitrary position in the
condensate, and find that an off-center vortex will move in a circular
trajectory around the trap center. We find the frequency of this precession to
be smaller than the elementary excitation frequencies in the cloud.
We also study the radiation of sound from a moving vortex in an infinite,
uniform system, and discuss the validity of this as an approximation for the
trapped case. Furthermore, we estimate the lifetime of a vortex due to
imperfections in the trapping potential.Comment: 10 pages, 1 eps figure, submitted to PRA, adjustments in response to
referee, one refernce adde
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Black Thunder Coal Mine and Los Alamos National Laboratory experimental study of seismic energy generated by large scale mine blasting
In an attempt to better understand the impact that large mining shots will have on verifying compliance with the international, worldwide, Comprehensive Test Ban Treaty (CTBT, no nuclear explosion tests), a series of seismic and videographic experiments has been conducted during the past two years at the Black Thunder Coal Mine. Personnel from the mine and Los Alamos National Laboratory have cooperated closely to design and perform experiments to produce results with mutual benefit to both organizations. This paper summarizes the activities, highlighting the unique results of each. Topics which were covered in these experiments include: (1) synthesis of seismic, videographic, acoustic, and computer modeling data to improve understanding of shot performance and phenomenology; (2) development of computer generated visualizations of observed blasting techniques; (3) documentation of azimuthal variations in radiation of seismic energy from overburden casting shots; (4) identification of, as yet unexplained, out of sequence, simultaneous detonation in some shots using seismic and videographic techniques; (5) comparison of local (0.1 to 15 kilometer range) and regional (100 to 2,000 kilometer range) seismic measurements leading to determine of the relationship between local and regional seismic amplitude to explosive yield for overburden cast, coal bulking and single fired explosions; and (6) determination of the types of mining shots triggering the prototype International Monitoring System for the CTBT
Non BPS noncommutative vortices
We construct exact vortex solutions to the equations of motion of the Abelian
Higgs model defined in non commutative space, analyzing in detail the
properties of these solutions beyond the BPS point. We show that our solutions
behave as smooth deformations of vortices in ordinary space time except for
parity symmetry breaking effects induced by the non commutative parameter
.Comment: 17 pages, 5 figure
Comments on Noncommutative Sigma Models
We review the derivation of a noncommutative version of the nonlinear sigma
model on \CPn and it's soliton solutions for finite emphasizing the
similarities it bears to the GMS scalar field theory. It is also shown that
unlike the scalar theory, some care needs to be taken in defining the
topological charge of BPS solitons of the theory due to nonvanishing surface
terms in the energy functional. Finally it is shown that, like its commutative
analogue, the noncommutative \CPn-model also exhibits a non-BPS sector.
Unlike the commutative case however, there are some surprises in the
noncommutative case that merit further study.Comment: 22 pages, 4 figures, LaTeX (JHEP3), Minor changes, Discussion
expanded and references adde
Disorder Effects in Two-Dimensional d-wave Superconductors
Influence of weak nonmagnetic impurities on the single-particle density of
states of two-dimensional electron systems with a conical
spectrum is studied. We use a nonperturbative approach, based on replica trick
with subsequent mapping of the effective action onto a one-dimensional model of
interacting fermions, the latter being treated by Abelian and non-Abelian
bosonization methods. It is shown that, in a d-wave superconductor, the density
of states, averaged over randomness, follows a nontrivial power-law behavior
near the Fermi energy: . The exponent
is calculated for several types of disorder. We demonstrate that the
property is a direct consequence of a {\it continuous} symmetry
of the effective fermionic model, whose breakdown is forbidden in two
dimensions. As a counter example, we consider another model with a conical
spectrum - a two-dimensional orbital antiferromagnet, where static disorder
leads to a finite due to breakdown of a {\it discrete}
(particle-hole) symmetry.Comment: 24 pages, 3 figures upon request, RevTe
Transmogrifying Fuzzy Vortices
We show that the construction of vortex solitons of the noncommutative
Abelian-Higgs model can be extended to a critically coupled gauged linear sigma
model with Fayet-Illiopolous D-terms. Like its commutative counterpart, this
fuzzy linear sigma model has a rich spectrum of BPS solutions. We offer an
explicit construction of the degree static semilocal vortex and study in
some detail the infinite coupling limit in which it descends to a degree
\C\Pk^{N} instanton. This relation between the fuzzy vortex and
noncommutative lump is used to suggest an interpretation of the noncommutative
sigma model soliton as tilted D-strings stretched between an NS5-brane and a
stack of D3-branes in type IIB superstring theory.Comment: 21 pages, 4 figures, LaTeX(JHEP3
Tachyon Condensation of D2/D4-Brane System in Noncommutative Gauge Theory
In this paper we construct the 2+1 effective theory of the light states in
D2/D4-brane system in the context of noncommutative Yang-Mills theory. This
effective theory is noncommutative and tachyonic, however, it is not taking the
form of an Abelian Higgs model as naively expected. We solve the classical
solutions of the effective theory which are nicely corresponding to different
states during the tachyon condensation process of the dissolution of D2-brane
into D4-brane. We also find that if the expected stable self-dual D0/D4
configuration as the unit-winding vortex exists, it would be highly calibrated
in the effective theory and be out of the reach of the analytic solutions.Comment: 16 pages, no figure, Latex, uses JHEP.cls; revised version, more
classical solutions added, some arguments improved in secion 4, typos
corrected; 3rd version, more clarifications on classical solutions in section
4; 4th version, more careful analysis on classical soution
Effect of Hund coupling in the one-dimensional SU(4) Hubbard model
The one-dimensional SU(4) Hubbard model perturbed by Hund coupling is
studied, away from half-filling, by means of renormalization group and
bosonization methods. A spectral gap is always present in the spin-orbital
sector irrespective of the magnitude of the Coulomb repulsion. We further
distinguish between two qualitatively different regimes. At small Hund
coupling, we find that the symmetry of the system is dynamically enlarged to
SU(4) at low energy with the result of {\it coherent} spin-orbital excitations.
When the charge sector is not gapped, a superconducting instability is shown to
exist. At large Hund coupling, the symmetry is no longer enlarged to SU(4) and
the excitations in the spin sector become {\it incoherent}. Furthermore, the
superconductivity can be suppressed in favor of the conventional charge density
wave state.Comment: 10 pages, 1 figur
Scalar Solitons on the Fuzzy Sphere
We study scalar solitons on the fuzzy sphere at arbitrary radius and
noncommutativity. We prove that no solitons exist if the radius is below a
certain value. Solitons do exist for radii above a critical value which depends
on the noncommutativity parameter. We construct a family of soliton solutions
which are stable and which converge to solitons on the Moyal plane in an
appropriate limit. These solutions are rotationally symmetric about an axis and
have no allowed deformations. Solitons that describe multiple lumps on the
fuzzy sphere can also be constructed but they are not stable.Comment: 24 pages, 2 figures, typo corrected and stylistic changes. v3:
reference adde
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