755 research outputs found
Vlasov simulation in multiple spatial dimensions
A long-standing challenge encountered in modeling plasma dynamics is
achieving practical Vlasov equation simulation in multiple spatial dimensions
over large length and time scales. While direct multi-dimension Vlasov
simulation methods using adaptive mesh methods [J. W. Banks et al., Physics of
Plasmas 18, no. 5 (2011): 052102; B. I. Cohen et al., November 10, 2010,
http://meetings.aps.org/link/BAPS.2010.DPP.NP9.142] have recently shown
promising results, in this paper we present an alternative, the Vlasov Multi
Dimensional (VMD) model, that is specifically designed to take advantage of
solution properties in regimes when plasma waves are confined to a narrow cone,
as may be the case for stimulated Raman scatter in large optic f# laser beams.
Perpendicular grid spacing large compared to a Debye length is then possible
without instability, enabling an order 10 decrease in required computational
resources compared to standard particle in cell (PIC) methods in 2D, with
another reduction of that order in 3D. Further advantage compared to PIC
methods accrues in regimes where particle noise is an issue. VMD and PIC
results in a 2D model of localized Langmuir waves are in qualitative agreement
Spacecraft Observations And Analytic Theory Of Crescent-Shaped Electron Distributions In Asymmetric Magnetic Reconnection
Supported by a kinetic simulation, we derive an exclusion energy parameter providing a lower kinetic energy bound for an electron to cross from one inflow region to the other during magnetic reconnection. As by a Maxwell Demon, only high energy electrons are permitted to cross the inner reconnection region, setting the electron distribution function observed along the low density side separatrix during asymmetric reconnection. The analytic model accounts for the two distinct flavors of crescent-shaped electron distributions observed by spacecraft in a thin boundary layer along the low density separatrix. Egedal, J; Le, A; Daughton, W; Wetherton, B; Cassak, P A; Chen, L -J; Lavraud, B; Trobert, R B; Dorelli, J; Gershman, D J; Avanov, L
A correspondence of modular forms and applications to values of L-series
An interpretation of the Rogers–Zudilin approach to the Boyd conjectures is established. This is based on a correspondence of modular forms which is of independent interest. We use the reinterpretation for two applications to values of L-series and values of their derivatives
The Force Balance of Electrons During Kinetic Anti-parallel Magnetic Reconnection
Fully kinetic simulations are applied to the study of 2D anti-parallel
reconnection, elucidating the dynamics by which the electron fluid maintains
force balance within both the electron diffusion region (EDR) and the ion
diffusion region (IDR). Inside the IDR, magnetic field-aligned electron
pressure anisotropy ( develops upstream of the
EDR. Compared to previous investigations, the use of modern computer facilities
allows for simulations at the natural proton to electron mass ratio
. In this high--limit the electron dynamics changes
qualitatively, as the electron inflow to the EDR is enhanced and mainly driven
by the anisotropic pressure. Using a coordinate system with the -direction
aligned with the reconnecting magnetic field and the -direction aligned with
the central current layer, it is well-known that for the much studied 2D
laminar anti-parallel and symmetric scenario the reconnection electric field at
the -line must be balanced by the and
off-diagonal electron pressure stress
components. We find that the electron anisotropy upstream of the EDR imposes
large values of within the EDR, and along the
direction of the reconnection -line this stress cancels with the stress of a
previously determined theoretical form for . The
electron frozen-in law is instead broken by pressure tensor gradients related
to the direct heating of the electrons by the reconnection electric field. The
reconnection rate is free to adjust to the value imposed externally by the
plasma dynamics at larger scales.Comment: Submitted to Physics of Plasmas, 11 October 202
Spacecraft observations and analytic theory of crescent-shaped electron distributions in asymmetric magnetic reconnection
Supported by a kinetic simulation, we derive an exclusion energy parameter
providing a lower kinetic energy bound for an electron to cross
from one inflow region to the other during magnetic reconnection. As by a
Maxwell Demon, only high energy electrons are permitted to cross the inner
reconnection region, setting the electron distribution function observed along
the low density side separatrix during asymmetric reconnection. The analytic
model accounts for the two distinct flavors of crescent-shaped electron
distributions observed by spacecraft in a thin boundary layer along the low
density separatrix.Comment: 6 pages, 3 figure
Standard Model with Cosmologically Broken Quantum Scale Invariance
We argue that scale invariance is not anomalous in quantum field theory,
provided it is broken cosmologically. We consider a locally scale invariant
extension of the Standard Model of particle physics and argue that it fits both
the particle and cosmological observations. The model is scale invariant both
classically and quantum mechanically. The scale invariance is broken
cosmologically producing all the dimensionful parameters. The cosmological
constant or dark energy is a prediction of the theory and can be calculated
systematically order by order in perturbation theory. It is expected to be
finite at all orders. The model does not suffer from the hierarchy problem due
to absence of scalar particles, including the Higgs, from the physical
spectrum.Comment: 13 pages, no figures significant revisions, no change in results or
conclusion
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