1,281 research outputs found
Hall response of interacting bosonic atoms in strong gauge fields: from condensed to FQH states
Interacting bosonic atoms under strong gauge fields undergo a series of phase
transitions that take the cloud from a simple Bose-Einstein condensate all the
way to a family of fractional-quantum-Hall-type states [M. Popp, B. Paredes,
and J. I. Cirac, Phys. Rev. A 70, 053612 (2004)]. In this work we demonstrate
that the Hall response of the atoms can be used to locate the phase transitions
and characterize the ground state of the many-body state. Moreover, the same
response function reveals within some regions of the parameter space, the
structure of the spectrum and the allowed transitions to excited states. We
verify numerically these ideas using exact diagonalization for a small number
of atoms, and provide an experimental protocol to implement the gauge fields
and probe the linear response using a periodically driven optical lattice.
Finally, we discuss our theoretical results in relation to recent experiments
with condensates in artificial magnetic fields [ L. J. LeBlanc, K.
Jimenez-Garcia, R. A. Williams, M. C. Beeler, A. R. Perry, W. D. Phillips, and
I. B. Spielman, Proc. Natl. Acad. Sci. USA 109, 10811 (2012)] and we analyze
the role played by vortex states in the Hall response.Comment: 10 pages, 7 figure
Dipole-Mode Vector Solitons
We find a new type of optical vector soliton that originates from trapping of
a dipole mode by a soliton-induced waveguide. These solitons, which appear as a
consequence of the vector nature of the two component system, are more stable
than the previously found optical vortex-mode solitons and represent a new type
of extremely robust nonlinear vector structure.Comment: Four pages with five eps figure
Lyashko-Looijenga morphisms and submaximal factorisations of a Coxeter element
When W is a finite reflection group, the noncrossing partition lattice NCP_W
of type W is a rich combinatorial object, extending the notion of noncrossing
partitions of an n-gon. A formula (for which the only known proofs are
case-by-case) expresses the number of multichains of a given length in NCP_W as
a generalised Fuss-Catalan number, depending on the invariant degrees of W. We
describe how to understand some specifications of this formula in a case-free
way, using an interpretation of the chains of NCP_W as fibers of a
Lyashko-Looijenga covering (LL), constructed from the geometry of the
discriminant hypersurface of W. We study algebraically the map LL, describing
the factorisations of its discriminant and its Jacobian. As byproducts, we
generalise a formula stated by K. Saito for real reflection groups, and we
deduce new enumeration formulas for certain factorisations of a Coxeter element
of W.Comment: 18 pages. Version 2 : corrected typos and improved presentation.
Version 3 : corrected typos, added illustrated example. To appear in Journal
of Algebraic Combinatoric
On Rank Problems for Planar Webs and Projective Structures
We present old and recent results on rank problems and linearizability of
geodesic planar webs.Comment: 31 pages; LaTeX; corrected the abstract and Introduction; added
reference
Construction of exact solutions by spatial traslations in inhomogeneous Nonlinear Schrodinger equations. Applications to Bose-Einstein condensation
In this paper we study a general nonlinear Schr\"odinger equation with a time
dependent harmonic potential. Despite the lack of traslational invariance we
find a symmetry trasformation which, up from any solution, produces infinitely
many others which are centered on classical trajectories. The results presented
here imply that, not only the center of mass of the wave-packet satisfies the
Ehrenfest theorem and is decoupled from the dynamics of the wave-packet, but
also the shape of the solution is independent of the behaviour of the center of
the wave. Our findings have implications on the dynamics of Bose-Einstein
condensates in magnetic trapsComment: Submitted to Phys. Re
Matrix Product Density Operators: Simulation of finite-T and dissipative systems
We show how to simulate numerically both the evolution of 1D quantum systems
under dissipation as well as in thermal equilibrium. The method applies to both
finite and inhomogeneous systems and it is based on two ideas: (a) a
representation for density operators which extends that of matrix product
states to mixed states; (b) an algorithm to approximate the evolution (in real
or imaginary time) of such states which is variational (and thus optimal) in
nature.Comment: See also M. Zwolak et al. cond-mat/040644
Rosemary distillation residues reduce lipid oxidation, increase alpha-tocopherol content and improve fatty acid profile of lamb meat
The experiment studied the effects of rosemary distillation residues (RR) intake on lamb meat quality, oxidative stability and fatty acid (FA) profile. Barbarine lambs of Control group were fed 600 g of hay, which was substituted by 600 g of pellets containing 60 and 87% of RR for RR60 and RR87 groups; all animals received 600 g of concentrate. Meat protein and fat content was similar for 3 treatments. Lipid oxidation was strongly reduced with RR diets. Both RR diets resulted in a higher a- tocopherol content in muscle. The metmyoglobin and deoxymyoglobin percentages were similar for all groups; however oxymyoglobin was higher for RR groups. The saturated (SFA) and unsaturated FAs (UFA) were unaffected by the diets. However, the PUFA, n-6 and n-3 were higher for RR groups. In conclusion, rosemary residues resulted in higher vitamin E content, so it enhanced the oxidative status and improved the fatty acid profile of lamb meat
Topological phase transitions between chiral and helical spin textures in a lattice with spin-orbit coupling and a magnetic field
We consider the combined effects of large spin-orbit couplings and a
perpendicular magnetic field in a 2D honeycomb fermionic lattice. This system
provides an elegant setup to generate versatile spin textures propagating along
the edge of a sample. The spin-orbit coupling is shown to induce topological
phase transitions between a helical quantum spin Hall phase and a chiral
spin-imbalanced quantum Hall state. Besides, we find that the spin orientation
of a single topological edge state can be tuned by a Rashba spin-orbit
coupling, opening an interesting route towards quantum spin manipulation. We
discuss the possible realization of our results using cold atoms trapped in
optical lattices, where large synthetic magnetic fields and spin-orbit
couplings can be engineered and finely tuned. In particular, this system would
lead to the observation of a time-reversal-symmetry-broken quantum spin Hall
phase.Comment: 8 pages, 3 figures, Accepted in Europhys. Lett. (Dec 2011
Molecular Dynamics Simulation of Solvent-Polymer Interdiffusion. I. Fickian diffusion
The interdiffusion of a solvent into a polymer melt has been studied using
large scale molecular dynamics and Monte Carlo simulation techniques. The
solvent concentration profile and weight gain by the polymer have been measured
as a function of time. The weight gain is found to scale as t^{1/2}, which is
expected for Fickian type of diffusion. The concentration profiles are fit very
well assuming Fick's second law with a constant diffusivity. The diffusivity
found from fitting Fick's second law is found to be independent of time and
equal to the self diffusion constant in the dilute solvent limit. We separately
calculated the diffusivity as a function of concentration using the Darken
equation and found that the diffusivity is essentially constant for the
concentration range relevant for interdiffusion.Comment: 17 pages and 7 figure
Fast high fidelity quantum non-demolition qubit readout via a non-perturbative cross-Kerr coupling
Qubit readout is an indispensable element of any quantum information
processor. In this work, we experimentally demonstrate a non-perturbative
cross-Kerr coupling between a transmon and a polariton mode which enables an
improved quantum non-demolition (QND) readout for superconducting qubits. The
new mechanism uses the same experimental techniques as the standard QND qubit
readout in the dispersive approximation, but due to its non-perturbative
nature, it maximizes the speed, the single-shot fidelity and the QND properties
of the readout. In addition, it minimizes the effect of unwanted decay channels
such as the Purcell effect. We observed a single-shot readout fidelity of 97.4%
for short 50 ns pulses, and we quantified a QND-ness of 99% for long
measurement pulses with repeated single-shot readouts
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