67,877 research outputs found
Non-equilibrium tube length fluctuations of entangled polymers
We investigate the nonequilibrium tube length fluctuations during the
relaxation of an initially stretched, entangled polymer chain. The
time-dependent variance of the tube length follows in the early-time
regime a simple universal power law originating in the
diffusive motion of the polymer segments. The amplitude is calculated
analytically both from standard reptation theory and from an exactly solvable
lattice gas model for reptation and its dependence on the initial and
equilibrium tube length respectively is discussed. The non-universality
suggests the measurement of the fluctuations (e.g. using flourescence
microscopy) as a test for reptation models.Comment: 12 pages, 2 figures. Minor typos correcte
Effects of extended impurity perturbation in d-wave superconductor
We describe the effects of electronic perturbation distributed on nearest
neighbor sites to the impurity center in a planar \textit{d}-wave
superconductor, in approximation of circular Fermi surface. Alike the behavior
previously reported for point-like perturbation and square Fermi surface, the
quasiparticle density of states can display a resonance
inside the gap (and very weak features from low symmetry representations of
non-local perturbation) and asymptotically vanishes at as
. The local suppression of SC order parameter
in this model is found to be somewhat weaker than for an equivalent point-like
(non-magnetic) perturbation and much weaker than for a spin-dependent
(extended) perturbation.Comment: 7 pages, 5 figures, some minor typos and the curves in Fig. 5
correcte
Noise-Free Measurement of Harmonic Oscillators with Instantaneous Interactions
We present a method of measuring the quantum state of a harmonic oscillator
through instantaneous probe-system selective interactions of the
Jaynes-Cummings type. We prove that this scheme is robust to general
decoherence mechanisms, allowing the possibility of measuring fast-decaying
systems in the weak-coupling regime. This method could be applied to different
setups: motional states of trapped ions, microwave fields in cavity/circuit
QED, and even intra-cavity optical fields.Comment: 4 pages, no figure, published in Physical Review Letter
Improvements on analytic modelling of stellar spots
In this work we present the solution of the stellar spot problem using the
Kelvin-Stokes theorem. Our result is applicable for any given location and
dimension of the spots on the stellar surface. We present explicitely the
result up to the second degree in the limb darkening law. This technique can be
used to calculate very efficiently mutual photometric effects produced by
eclipsing bodies occulting stellar spots and to construct complex spot shapes.Comment: Resubmitted to MNRAS after accounting for minor comments of second
review, 9 pages, 5 figures, software available at
http://eduscisoft.com/KSINT
Cavity-aided quantum parameter estimation in a bosonic double-well Josephson junction
We describe an apparatus designed to make non-demolition measurements on a
Bose-Einstein condensate (BEC) trapped in a double-well optical cavity. This
apparatus contains, as well as the bosonic gas and the trap, an optical cavity.
We show how the interaction between the light and the atoms, under appropriate
conditions, can allow for a weakly disturbing yet highly precise measurement of
the population imbalance between the two wells and its variance. We show that
the setting is well suited for the implementation of quantum-limited estimation
strategies for the inference of the key parameters defining the evolution of
the atomic system and based on measurements performed on the cavity field. This
would enable {\it de facto} Hamiltonian diagnosis via a highly controllable
quantum probe.Comment: 8 pages, 5 figures, RevTeX4; Accepted for publication in Phys. Rev.
Ultracold dipolar gases - a challenge for experiments and theory
We present a review of recent results concerning the physics of ultracold
trapped dipolar gases. In particular, we discuss the Bose-Einstein condensation
for dipolar Bose gases and the BCS transition for dipolar Fermi gases. In both
cases we stress the dominant role of the trap geometry in determining the
properties of the system. We present also results concerning bosonic dipolar
gases in optical lattices and the possibility of obtaining variety of different
quantum phases in such case. Finally, we analyze various possible routes
towards achieving ultracold dipolar gases.Comment: This paper is based on the lecture given by M. Lewenstein at the
Nobel Symposium ''Coherence and Condensation in Quantum Systems'',
Gothesburg, 4-7.12.200
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