68,115 research outputs found
Dusty plasma cavities: probe-induced and natural
A comprehensive exploration of regional dust evacuation in complex plasma
crystals is presented. Voids created in 3D crystals on the International Space
Station have provided a rich foundation for experiments, but cavities in dust
crystals formed in ground-based experiments have not received as much
attention. Inside a modified GEC RF cell, a powered vertical probe was used to
clear the central area of a dust crystal, producing a cavity with high
cylindrical symmetry. Cavities generated by three mechanisms are examined.
First, repulsion of micrometer-sized particles by a negatively charged probe is
investigated. A model of this effect developed for a DC plasma is modified and
applied to explain new experimental data in RF plasma. Second, the formation of
natural cavities is surveyed; a radial ion drag proposed to occur due to a
curved sheath is considered in conjunction with thermophoresis and a flattened
confinement potential above the center of the electrode. Finally, cavity
formation unexpectedly occurs upon increasing the probe potential above the
plasma floating potential. The cavities produced by these methods appear
similar, but each are shown to be facilitated by fundamentally different
processes.Comment: 10 pages, 12 figure
Linearizability with Ownership Transfer
Linearizability is a commonly accepted notion of correctness for libraries of
concurrent algorithms. Unfortunately, it assumes a complete isolation between a
library and its client, with interactions limited to passing values of a given
data type. This is inappropriate for common programming languages, where
libraries and their clients can communicate via the heap, transferring the
ownership of data structures, and can even run in a shared address space
without any memory protection. In this paper, we present the first definition
of linearizability that lifts this limitation and establish an Abstraction
Theorem: while proving a property of a client of a concurrent library, we can
soundly replace the library by its abstract implementation related to the
original one by our generalisation of linearizability. This allows abstracting
from the details of the library implementation while reasoning about the
client. We also prove that linearizability with ownership transfer can be
derived from the classical one if the library does not access some of data
structures transferred to it by the client
Analytical solution of generalized Burton--Cabrera--Frank equations for growth and post--growth equilibration on vicinal surfaces
We investigate growth on vicinal surfaces by molecular beam epitaxy making
use of a generalized Burton--Cabrera--Frank model. Our primary aim is to
propose and implement a novel analytical program based on a perturbative
solution of the non--linear equations describing the coupled adatom and dimer
kinetics. These equations are considered as originating from a fully
microscopic description that allows the step boundary conditions to be directly
formulated in terms of the sticking coefficients at each step. As an example,
we study the importance of diffusion barriers for adatoms hopping down
descending steps (Schwoebel effect) during growth and post-growth equilibration
of the surface.Comment: 16 pages, REVTeX 3.0, IC-DDV-94-00
A Bootstrapping Approach for Generating Maximally Path-Entangled Photon States
We propose a bootstrapping approach to generation of maximally path-entangled
states of photons, so called ``NOON states''. Strong atom-light interaction of
cavity QED can be employed to generate NOON states with about 100 photons;
which can then be used to boost the existing experimental Kerr nonlinearities
based on quantum coherence effects to facilitate NOON generation with
arbitrarily large number of photons all within the current experimental state
of the art technology. We also offer an alternative scheme that uses an
atom-cavity dispersive interaction to obtain sufficiently high
Kerr-nonlinearity necessary for arbitrary NOON generation
Entanglement of remote atomic qubits
We report observations of entanglement of two remote atomic qubits, achieved
by generating an entangled state of an atomic qubit and a single photon at Site
A, transmitting the photon to Site B in an adjacent laboratory through an
optical fiber, and converting the photon into an atomic qubit. Entanglement of
the two remote atomic qubits is inferred by performing, locally, quantum state
transfer of each of the atomic qubits onto a photonic qubit and subsequent
measurement of polarization correlations in violation of the Bell inequality
|S| <2. We experimentally determine S =2.16 +/- 0.03. Entanglement of two
remote atomic qubits, each qubit consisting of two independent spin wave
excitations, and reversible, coherent transfer of entanglement between matter
and light, represent important advances in quantum information science.Comment: 5 pages, 3 figure
Recommended from our members
Analysis of rolling bearing power loss models for twin screw oil injected compressor
The mechanical losses inside a screw compressor limit the performance of the compressor in terms of efficiency. These losses arise due to relative motion between elements inside the screw compressor. The estimation of mechanical losses predicted in the literature is around 10-15% of the total shaft power. One of the elements which contribute significantly to these losses is rolling element bearings. There are numerous mathematical models available which predict power losses in the rolling bearings. The objective of this paper is to study different models to predict power loss for rolling bearings and to predict the power losses for the bearings used for oil injected, twin screw compressor. A comparison between different power loss models for different operating conditions of compressor is also presented in this paper and results of analysis are compared with available experimental observations. The analysis helps to determine suitable power loss model for different operating conditions and more realistic predictions of the power losses. This allows designers for more accurate estimation of the performance of screw compressors
Field behavior of an Ising model with aperiodic interactions
We derive exact renormalization-group recursion relations for an Ising model,
in the presence of external fields, with ferromagnetic nearest-neighbor
interactions on Migdal-Kadanoff hierarchical lattices. We consider layered
distributions of aperiodic exchange interactions, according to a class of
two-letter substitutional sequences. For irrelevant geometric fluctuations, the
recursion relations in parameter space display a nontrivial uniform fixed point
of hyperbolic character that governs the universal critical behavior. For
relevant fluctuations, in agreement with previous work, this fixed point
becomes fully unstable, and there appears a two-cycle attractor associated with
a new critical universality class.Comment: 9 pages, 1 figure (included). Accepted for publication in Int. J.
Mod. Phys.
Symmetric photon-photon coupling by atoms with Zeeman-split sublevels
We propose a simple scheme for highly efficient nonlinear interaction between
two weak optical fields. The scheme is based on the attainment of
electromagnetically induced transparency simultaneously for both fields via
transitions between magnetically split F=1 atomic sublevels, in the presence of
two driving fields. Thereby, equal slow group velocities and symmetric
cross-coupling of the weak fields over long distances are achieved. By simply
tuning the fields, this scheme can either yield giant cross-phase modulation or
ultrasensitive two-photon switching.Comment: Modified scheme, 4 pages, 1 figur
- …