3,736 research outputs found
Heat fluctuations for harmonic oscillators
Heat fluctuations of a harmonic oscillator in contact with a thermostat and
driven out of equilibrium by an external deterministic force are studied
experimentally and theoretically within the context of Fluctuation Theorems. We
consider the case of a periodic forcing of the oscillator, and we calculate the
analytic probability density function of heat fluctuations. The limit of large
time is discussed and we show that heat fluctuations satisfy the conventional
fluctuation theorem, even if a different fluctuation relation exists for this
quantity. Experimental results are also given for a transient state.Comment: Submitted to Europhysics Letter
Scaling of Information in Turbulence
We propose a new perspective on Turbulence using Information Theory. We
compute the entropy rate of a turbulent velocity signal and we particularly
focus on its dependence on the scale. We first report how the entropy rate is
able to describe the distribution of information amongst scales, and how one
can use it to isolate the injection, inertial and dissipative ranges, in
perfect agreement with the Batchelor model and with a fBM model. In a second
stage, we design a conditioning procedure in order to finely probe the
asymmetries in the statistics that are responsible for the energy cascade. Our
approach is very generic and can be applied to any multiscale complex system.Comment: in Europhysics Letters, 201
Hypergeometric solutions to Schr\"odinger equations for the quantum Painlev\'e equations
We consider Schr\"odinger equations for the quantum Painlev\'e equations. We
present hypergeometric solutions of the Schr\"odinger equations for the quantum
Painlev\'e equations, as particular solutions. We also give a representation
theoretic correspondence between Hamiltonians of the Schr\"odinger equations
for the quantum Painlev\'e equations and those of the KZ equation or the
confluent KZ equations.Comment: 17 pages; Journal of Mathematical Physics (Vol.52, Issue 8) 201
Transmission of matter wave solitons through nonlinear traps and barriers
The transmissions of matter wave solitons through linear and nonlinear
inhomogeneities induced by the spatial variations of the trap and the
scattering length in Bose-Einstein condensates are investigated. New phenomena,
such as the enhanced transmission of a soliton through a linear trap by a
modulation of the scattering length, are exhibited. The theory is based on the
perturbed Inverse Scattering Transform for solitons, and we show that radiation
effects are important. Numerical simulations of the Gross-Pitaevskii equation
confirm the theoretical predictions.Comment: 6 pages, 4 figure
A two-way interactive broadband satellite architecture to break the digital divide barrier
September 24-26, 2007, Turin, Ital
TV-Centric technologies to provide remote areas with two-way satellite broadband access
October 1-2, 2007, Rome, Italy TV-Centric Technologies To Provide Remote Areas With Two-Way Satellite Broadband Acces
Work fluctuation theorems for harmonic oscillators
The work fluctuations of an oscillator in contact with a thermostat and
driven out of equilibrium by an external force are studied experimentally and
theoretically within the context of Fluctuation Theorems (FTs). The oscillator
dynamics is modeled by a second order Langevin equation. Both the transient and
stationary state fluctuation theorems hold and the finite time corrections are
very different from those of a first order Langevin equation. The periodic
forcing of the oscillator is also studied; it presents new and unexpected short
time convergences. Analytical expressions are given in all cases
Parental CoâConstruction of 5â to 13âYearâOlds\u27 Global SelfâEsteem Through Reminiscing About Past Events
The current study explored parental processes associated with children\u27s global selfâesteem development. Eighty 5â to 13âyearâolds and one of their parents provided qualitative and quantitative data through questionnaires, openâended questions, and a laboratoryâbased reminiscing task. Parents who included more explanations of emotions when writing about the lowest points in their lives were more likely to discuss explanations of emotions experienced in negative past events with their child, which was associated with child attachment security. Attachment was associated with concurrent selfâesteem, which predicted relative increases in selfâesteem 16 months later, on average. Finally, parent support also predicted residual increases in selfâesteem. Findings extend prior research by including younger ages and uncovering a process by which two theoretically relevant parenting behaviors impact selfâesteem development
On spectral scaling laws for incompressible anisotropic MHD turbulence
A heuristic model is given for anisotropic magnetohydrodynamics (MHD)
turbulence in the presence of a uniform external magnetic field B_0 {\bf {\hat
e}_{\pa}}. The model is valid for both moderate and strong and is able
to describe both the strong and weak wave turbulence regimes as well as the
transition between them. The main ingredient of the model is the assumption of
constant ratio at all scales between \add{the} linear wave period and \add{the}
nonlinear turnover timescale. Contrary to the model of critical balance
introduced by Goldreich and Sridhar [P. Goldreich and S. Sridhar, ApJ {\bf
438}, 763 (1995)], it is not assumed in addition that this ratio be equal to
unity at all scales which allows us to use the Iroshnikov-Kraichnan
phenomenology. It is then possible to recover the widely observed anisotropic
scaling law \kpa \propto \kpe^{2/3} between parallel and perpendicular
wavenumbers (with reference to B_0 {\bf {\hat e}_{\pa}}) and to obtain the
universal prediction, , for the total energy spectrum
E(\kpe,\kpa) \sim \kpe^{-\alpha} \kpa^{-\beta}. In particular, with such a
prediction the weak Alfv\'en wave turbulence constant-flux solution is
recovered and, for the first time, a possible explanation to its precursor
found numerically by Galtier et al [S. Galtier et al., J. Plasma Phys. {\bf
63}, 447 (2000)] is given
- âŠ