11,175 research outputs found
How hole defects modify vortex dynamics in ferromagnetic nanodisks
Defects introduced in ferromagnetic nanodisks may deeply affect the structure
and dynamics of stable vortex-like magnetization. Here, analytical techniques
are used for studying, among other dynamical aspects, how a small cylindrical
cavity modify the oscillatory modes of the vortex. For instance, we have
realized that if the vortex is nucleated out from the hole its gyrotropic
frequencies are shifted below. Modifications become even more pronounced when
the vortex core is partially or completely captured by the hole. In these
cases, the gyrovector can be partially or completely suppressed, so that the
associated frequencies increase considerably, say, from some times to several
powers. Possible relevance of our results for understanding other aspects of
vortex dynamics in the presence of cavities and/or structural defects are also
discussed.Comment: 9 pages, 4 page
Two-species fermion mixtures with population imbalance
We analyze the phase diagram of uniform superfluidity for two-species fermion
mixtures from the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensation
(BEC) limit as a function of the scattering parameter and population imbalance.
We find at zero temperature that the phase diagram of population imbalance
versus scattering parameter is asymmetric for unequal masses, having a larger
stability region for uniform superfluidity when the lighter fermions are in
excess. In addition, we find topological quantum phase transitions associated
with the disappearance or appearance of momentum space regions of zero
quasiparticle energies. Lastly, near the critical temperature, we derive the
Ginzburg-Landau equation, and show that it describes a dilute mixture of
composite bosons and unpaired fermions in the BEC limit.Comment: 4 pages with 3 figures, accepted version to PR
Single observable concurrence measurement without simultaneous copies
We present a protocol that allows us to obtain the concurrence of any two
qubit pure state by performing a minimal and optimal tomography of one of the
subsystems through measuring a single observable of an ancillary four
dimensional qudit. An implementation for a system of trapped ions is also
proposed, which can be achieved with present day experimental techniques.Comment: 4 pages, 1 figur
The mechanism of action of antimicrobial peptides : lipid vesicles vs. bacteria
Copyright © 2012 Melo and Castanho. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits use, distribution
and reproduction in other forums, provided the original authors and source are credited and subject to any copyright notices concerning any third-party graphics etc.The authors acknowledge the European FP7-PEOPLE-2009-IEF-254559 grant to Manuel N. Melo and the Fundação para a Ciência e a Tecnologia (Portugal) project PTDC/QUI-BIQ/112929/2009
F-wave versus P-wave Superconductivity in Organic Conductors
Current experimental results suggest that some organic quasi-one-dimensional
superconductors exhibit triplet pairing symmetry. Thus, we discuss several
potential triplet order parameters for the superconducting state of these
systems within the functional integral formulation. We compare weak spin-orbit
coupling , , and symmetries via several thermodynamic
quantities. For each symmetry, we analyse the temperature dependences of the
order parameter, condensation energy, specific heat, and superfluid density
tensor.Comment: 5 pages, 4 figure
Simbiose micorrízica em plantas forrageiras.
Esse projeto teve como objetivos: verificar a condição micorrízica em plantas forrageiras nas condições do semi-árido, avaliar a eficiência de fungos micorrízicos arbusculares em promover o crescimento vegetal e o teor nutricional de plantas de Cajanus cajan var. Petrolina, passível de utilização na alimentação animal, e conhecer o potencial dessas forragens em incrementar a propagação desses fungos no solo
The exponent of the non-abelian tensor square and related constructions of -groups
Let be a finite -group. In this paper we obtain bounds for the
exponent of the non-abelian tensor square and of , which
is a certain extension of by . In particular, we
bound in terms of and when admits
some specific normal subgroup . We also establish bounds for in terms of and either the nilpotency class or the coclass of the
group , improving some existing bounds
Exactly Solvable Models of Interacting Spin-s Particles in one-dimension
We consider the exact solution of a many-body problem of spin- particles
interacting through an arbitrary U(1) invariant factorizable -matrix. The
solution is based on a unified formulation of the quantum inverse scattering
method for an arbitrary -dimensional monodromy matrix. The respective
eigenstates are shown to be given in terms of creation fields by a general
new recurrence relation. This allows us to derive the spectrum and the
respective Bethe ansatz equations.Comment: 10 pages, plain late
- …