45,082 research outputs found
Scaling laws of resistive magnetohydrodynamic reconnection in the high-Lundquist-number, plasmoid-unstable regime
The Sweet-Parker layer in a system that exceeds a critical value of the
Lundquist number () is unstable to the plasmoid instability. In this paper,
a numerical scaling study has been done with an island coalescing system driven
by a low level of random noise. In the early stage, a primary Sweet-Parker
layer forms between the two coalescing islands. The primary Sweet-Parker layer
breaks into multiple plasmoids and even thinner current sheets through multiple
levels of cascading if the Lundquist number is greater than a critical value
. As a result of the plasmoid instability, the system
realizes a fast nonlinear reconnection rate that is nearly independent of ,
and is only weakly dependent on the level of noise. The number of plasmoids in
the linear regime is found to scales as , as predicted by an earlier
asymptotic analysis (Loureiro \emph{et al.}, Phys. Plasmas \textbf{14}, 100703
(2007)). In the nonlinear regime, the number of plasmoids follows a steeper
scaling, and is proportional to . The thickness and length of current sheets
are found to scale as , and the local current densities of current
sheets scale as . Heuristic arguments are given in support of theses
scaling relations.Comment: Submitted to Phys. Plasma
Higgs Boson in RG running Inflationary Cosmology
An intriguing hypothesis is that gravity may be non-perturbatively
renormalizable via the notion of asymptotic safety. We show that the Higgs
sector of the SM minimally coupled to asymptotically safe gravity can generate
the observed near scale-invariant spectrum of the Cosmic Microwave Background
through the curvaton mechanism. The resulting primordial power spectrum places
an upper bound on the Higgs mass, which for finely tuned values of the curvaton
parameters, is compatible with the recently released Large Hadron Collider
data.Comment: 7 pages, no figur
Regio- and Stereoselective Ruthenium Catalyzed Hydrovinylation of 1,3-Dienes: Application to the Generation of a 20S-Steroidal Sidechain
The addition of ethylene to 1,3-dienes and 1-vinylcycloalkenes, catalyzed by two ruthenium complexes, proceeds in a regioselective fashion to afford 3-methyl-1,4-dienes as products. For a steroidal-based 1-vinylcycloalkene, the addition is stereospecific, giving a product with a 20(S) configuration
Thermodynamic properties of a dipolar Fermi gas
Based on the semi-classical theory, we investigate the thermodynamic
properties of a dipolar Fermi gas. Through a self-consistent procedure, we
numerically obtain the phase space distribution function at finite temperature.
We show that the deformations in both momentum and real space becomes smaller
and smaller as one increases the temperature. For homogeneous case, we also
calculate pressure, entropy, and heat capacity. In particular, at low
temperature limit and in weak interaction regime, we obtain an analytic
expression for the entropy, which agrees qualitatively with our numerical
result. The stability of a trapped gas at finite temperature is also explored
Spontaneous spin textures in dipolar spinor condensates
We have mapped out a detailed phase diagram that shows the ground state
structure of a spin-1 condensate with magnetic dipole-dipole interactions. We
show that the interplay between the dipolar and the spin-exchange interactions
induces a rich variety of quantum phases that exhibit spontaneous magnetic
ordering in the form of intricate spin textures.Comment: 4.1 pages, 4 figure
Multi-vortex dynamics in junctions of charge density waves
Ground state reconstruction by creation of topological defects in junctions
of CDWs is a convenient playground for modern efforts of field-effect
transformations in strongly correlated materials with spontaneous symmetry
breakings. Being transient, this effect contributes also to another new science
of pump-induced phase transitions. We present a dynamical model for behavior of
the CDW in restricted geometries of junctions under an applied voltage or a
passing current. The model takes into account multiple interacting fields: the
amplitude and the phase of the CDW complex order parameter, distributions of
the electric field, the density and the current of various normal carriers. A
particular challenge was to monitor the local conservation of the condensed and
the normal charge densities. That was done easily invoking the chiral
invariance and the associated anomaly, but prize is an unconventional
Ginsburg-Landau type theory which is not analytic with respect to the order
parameter. The numerical modeling poses unusual difficulties but still can
demonstrate that vortices are nucleated at the junction boundary when the
voltage across, or the current through, exceed a threshold.Comment: To be published in proceedings of the conference SUPERSTRIPES-2014,
A. Bianconi ed., J. Supercond. Nov. Mag., (2015
Analytic Model Of Electron Self-Injection In A Plasma Wakefield Accelerator In The Strongly Nonlinear Bubble Regime
Self-injection of background electrons in plasma wakefield accelerators in the highly nonlinear bubble regime is analyzed using particle-in-cell and semi-analytic modeling. It is shown that the return current in the bubble sheath layer is crucial for accurate determination of the trapped particle trajectories.Physic
Highly Cooperative Tetrametallic Ruthenium-μ-Oxo-μ-Hydroxo Catalyst for the Alcohol Oxidation Reaction
The tetrametallic ruthenium-oxo-hydroxo-hydride complex {[(PCy3)(CO)RuH]4(μ4-O)(μ3-OH)(μ2-OH)} (1) was synthesized in two steps from the monomeric complex (PCy3)(CO)RuHCl (2). The tetrameric complex 1 was found to be a highly effective catalyst for the transfer dehydrogenation of alcohols. Complex 1 showed a different catalytic activity pattern toward primary and secondary benzyl alcohols, as indicated by the Hammett correlation for the oxidation reaction of p-X-C6H4CH2OH (ρ = −0.45) and p-X-C6H4CH(OH)CH3 (ρ = +0.22) (X = OMe, CH3, H, Cl, CF3). Both a sigmoidal curve from the plot of initial rate vs [PhCH(OH)CH3] (K0.5 = 0.34 M; Hill coefficient, n = 4.2 ± 0.1) and the phosphine inhibition kinetics revealed the highly cooperative nature of the complex for the oxidation of secondary alcohols
Using Simple Neural Networks to Correct Errors in Optical Data Transmission.
We have demonstrated the applicability of
neural-network-based systems to the problem
of reducing the effects of signal distortion,
and shown that such a system has the potential
to reduce the bit-error-rate in the digitized
version of the analogue electrical signal
derived from an optical data stream by a
substantial margin over existing techniques
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