2,447 research outputs found
Transport Coefficients of the Yukawa One Component Plasma
We present equilibrium molecular-dynamics computations of the thermal
conductivity and the two viscosities of the Yukawa one-component plasma. The
simulations were performed within periodic boundary conditions and Ewald sums
were implemented for the potentials, the forces, and for all the currents which
enter the Kubo formulas. For large values of the screening parameter, our
estimates of the shear viscosity and the thermal conductivity are in good
agreement with the predictions of the Chapman-Enskog theory.Comment: 11 pages, 2 figure
Monte Carlo simulations of the screening potential of the Yukawa one-component plasma
A Monte Carlo scheme to sample the screening potential H(r) of Yukawa plasmas
notably at short distances is presented. This scheme is based on an importance
sampling technique. Comparisons with former results for the Coulombic
one-component plasma are given. Our Monte Carlo simulations yield an accurate
estimate of H(r) as well for short range and long range interparticle
distances.Comment: to be published in Journal of Physics A: Mathematical and Genera
Theory of Interaction of Memory Patterns in Layered Associative Networks
A synfire chain is a network that can generate repeated spike patterns with
millisecond precision. Although synfire chains with only one activity
propagation mode have been intensively analyzed with several neuron models,
those with several stable propagation modes have not been thoroughly
investigated. By using the leaky integrate-and-fire neuron model, we
constructed a layered associative network embedded with memory patterns. We
analyzed the network dynamics with the Fokker-Planck equation. First, we
addressed the stability of one memory pattern as a propagating spike volley. We
showed that memory patterns propagate as pulse packets. Second, we investigated
the activity when we activated two different memory patterns. Simultaneous
activation of two memory patterns with the same strength led the propagating
pattern to a mixed state. In contrast, when the activations had different
strengths, the pulse packet converged to a two-peak state. Finally, we studied
the effect of the preceding pulse packet on the following pulse packet. The
following pulse packet was modified from its original activated memory pattern,
and it converged to a two-peak state, mixed state or non-spike state depending
on the time interval
Nusselt number scaling in tokamak plasma turbulence
K. Takeda et al., Physics of Plasmas 12, 052309 (2005) https://doi.org/10.1063/1.189516
Ion energetics in collisionless sheaths of rf process plasmas
S. Hamaguchi, Physics of Fluids B: Plasma Physics 4, 2362 (1992) https://doi.org/10.1063/1.86020
Ponderomotive force and ion energy distributions in an rf sheath
The incident-ion energy distribution in a collisionless radio-frequency (rf) sheath is derived analytically for a general electric-field configuration in the high-frequency regime. The analysis is based on a two-time-scale asymptotic expansion of the ion equation of motion, where the ratio of the ion transit frequency tr to the rf frequency is assumed to be small. It is shown that the ponderomotive force due to the rf modulation of the electric field exerts a retarding effect on the ion motion, counteracting the dc-bias field. The results obtained here are applicable to rf-discharge-based process tools used in microelectronics fabrication, where the conditions of low collisionality and high rf frequency are usually satisfied. © 1992 The American Physical Society.S. Hamaguchi, R. T. Farouki, and M. Dalvie, Phys. Rev. Lett. 68, 44, 199
Across-wafer nonuniformity of long throw sputter deposition
A. A. Mayo et al., Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena 15, 1788 (1997) https://doi.org/10.1116/1.58952
Lepton Flavor Violation and Cosmological Constraints on R-parity Violation
In supersymmetric standard models R-parity violating couplings are severely
constrained, since otherwise they would erase the existing baryon asymmetry
before the electroweak transition. It is often claimed that this cosmological
constraint can be circumvented if the baryon number and one of the lepton
flavor numbers are sufficiently conserved in these R-parity violating
couplings, because B/3-L_i for each lepton flavor is separately conserved by
the sphaleron process. We discuss the effect of lepton flavor violation on the
B-L conservation, and show that even tiny slepton mixing angles \theta_{12}
\gsim {\cal O}(10^{-4}) and \theta_{23}, \theta_{13}\gsim {\cal O}(10^{-5})
will spoil the separate B/3-L_i conservation. In particular, if lepton flavor
violations are observed in experiments such as MEG and B-factories, it will
imply that all the R-parity violating couplings must be suppressed to avoid the
B-L erasure. We also discuss the implication for the decay of the lightest MSSM
particle at the LHC.Comment: 21 pages, 7 figures. v2: minor change
Sparse and Dense Encoding in Layered Associative Network of Spiking Neurons
A synfire chain is a simple neural network model which can propagate stable
synchronous spikes called a pulse packet and widely researched. However how
synfire chains coexist in one network remains to be elucidated. We have studied
the activity of a layered associative network of Leaky Integrate-and-Fire
neurons in which connection we embed memory patterns by the Hebbian Learning.
We analyzed their activity by the Fokker-Planck method. In our previous report,
when a half of neurons belongs to each memory pattern (memory pattern rate
), the temporal profiles of the network activity is split into
temporally clustered groups called sublattices under certain input conditions.
In this study, we show that when the network is sparsely connected (),
synchronous firings of the memory pattern are promoted. On the contrary, the
densely connected network () inhibit synchronous firings. The sparseness
and denseness also effect the basin of attraction and the storage capacity of
the embedded memory patterns. We show that the sparsely(densely) connected
networks enlarge(shrink) the basion of attraction and increase(decrease) the
storage capacity
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