6,050 research outputs found
Black holes and non-relativistic quantum systems
We describe black holes in d+3 dimensions, whose thermodynamic properties
correspond to those of a scale invariant non-relativistic d+1 dimensional
quantum system with dynamical exponent z=2. The gravitational model involves a
massive abelian vector field and a scalar field, in addition to the metric. The
energy per particle in the dual theory is , exactly as in a
non-interacting Fermi gas, while the ratio of shear viscosity to entropy
density is .Comment: 8 pages; v2: discussion modifie
Towards hydrodynamics without an entropy current
We present a generating functional which describes the equilibrium
thermodynamic response of a relativistic system to external sources. A
variational principle gives rise to constraints on the response parameters of
relativistic hydrodynamics without making use of an entropy current. Our method
reproduces and extends results available in the literature. It also provides a
technique for efficiently computing n-point zero-frequency hydrodynamic
correlation functions without the need to solve the equations of hydrodynamics.Comment: 4+epsilon pages, v2: comments and references adde
Interminiband Rabi oscillations in biased semiconductor superlattices
Carrier dynamics at energy level anticrossings in biased semiconductor
superlattices, was studied in the time domain by solving the time-dependent
Schroedinger equation. The resonant nature of interminiband Rabi oscillations
has been explicitly demonstrated to arise from interference of intrawell and
Bloch oscillations. We also report a simulation of direct Rabi oscillations
across three minibands, in the high field regime, due to interaction between
three strongly coupled minibands.Comment: 13 pages, 16 figure
Mercury's Weather-Beaten Surface: An Examination of the Relevant Processes Through Comparisons and Contrasts with the Moon and Asteroids
We examine global color properties of Mercury and their correlations to the predicted trends due to particle bombardment and thermal processing. Color ratio and spectral slope analyzes are interpreted relative to lunar and asteroid studies
Scaling and self-similarity in an unforced flow of inviscid fluid trapped inside a viscous fluid in a Hele-Shaw cell
We investigate quasi-two-dimensional relaxation, by surface tension, of a
long straight stripe of inviscid fluid trapped inside a viscous fluid in a
Hele-Shaw cell. Combining analytical and numerical solutions, we describe the
emergence of a self-similar dumbbell shape and find non-trivial dynamic
exponents that characterize scaling behavior of the dumbbell dimensions.Comment: 4 pages, 5 figures, to appear in PR
Interaction between ionic lattices and superconducting condensates
The interaction of the ionic lattice with the superconducting condensate is
treated in terms of the electrostatic force in superconductors. It is shown
that this force is similar but not identical to the force suggested by the
volume difference of the normal and superconducting states. The BCS theory
shows larger deviations than the two-fluid model.Comment: 6 pages no figure
Two and three electrons in a quantum dot: 1/|J| - expansion
We consider systems of two and three electrons in a two-dimensional parabolic
quantum dot. A magnetic field is applied perpendicularly to the electron plane
of motion. We show that the energy levels corresponding to states with high
angular momentum, J, and a low number of vibrational quanta may be
systematically computed as power series in 1/|J|. These states are relevant in
the high-B limit.Comment: LaTeX, 15 pages,6 postscript figure
Prediction and Simulator Verification of Roll/Lateral Adverse Aeroservoelastic RotorcraftâPilot Couplings
The involuntary interaction of a pilot with an aircraft can be described as pilot-assisted oscillations. Such
phenomena are usually only addressed late in the design process when they manifest themselves during ground/flight
testing. Methods to be able to predict such phenomena as early as possible are therefore useful. This work describes a
technique to predict the adverse aeroservoelastic rotorcraftâpilot couplings, specifically between a rotorcraftâs roll
motion and the resultant involuntary pilot lateral cyclic motion. By coupling linear vehicle aeroservoelastic models
and experimentally identified pilot biodynamic models, pilot-assisted oscillations and no-pilot-assisted oscillation
conditions have been numerically predicted for a soft-in-plane hingeless helicopter with a lightly damped regressive
leadâlag mode that strongly interacts with the roll modeat a frequency within the biodynamic band of the pilots. These
predictions have then been verified using real-time flight-simulation experiments. The absence of any similar adverse
couplings experienced while using only rigid-body models in the flight simulator verified that the observed
phenomena were indeed aeroelastic in nature. The excellent agreement between the numerical predictions and the
observed experimental results indicates that the techniques developed in this paper can be used to highlight the
proneness of new or existing designs to pilot-assisted oscillation
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