7,128 research outputs found
A critical review of charged particle astronomy at Saturn: The evidence for co-orbiting material in the inner satellite system
The charged particle observations from Pioneer and Voyager at Saturn were reassessed with a view towards providing limits on the amount of unseen dust and debris that may exist in the Saturnian system. Such estimates are crucial for planning the Cassini tour of Saturn. The data from Pioneer 11 and Voyager were reviewed, intercompared, and correlated with model predictions to set limits on the matter distribution
Dynamics of particle production by strong electric fields in non-Abelian plasmas
We develop methods for computing the dynamics of fermion pair production by
strong color electric fields using the semi-classical Boltzmann-Vlasov
equation. We present numerical results for a model with SU(2) symmetry in (1+1)
dimension.Comment: 10 pages, 8 figure
Environmental Impact Specification for Direct Space Weathering of Kuiper Belt and Oort Cloud Objects
The Direct Space Weathering Project of NASA's Outer Planets Research Program addresses specification of the plasma and energetic particle environments for irradiation and surface chemical processing of icy bodies in the outer solar system and the local interstellar medium. Knowledge of the radiation environments is being expanded by ongoing penetration of the twin Voyager spacecraft into the heliosheath boundary region of the outer heliosphere and expected emergence within the next decade into the very local interstellar medium. The Voyager measurements are being supplemented by remote sensing from Earth orbit of energetic neutral atom emission from this boundary region by NASA's Interstellar Boundary Explorer (IBEX). Although the Voyagers long ago passed the region of the Classical Kuiper Belt, the New Horizons spacecraft will encounter Pluto in 2015 and thereafter explore one or more KBOs, meanwhile providing updated measurements of the heliospheric radiation environment in this region. Modeling of ion transport within the heliosphere allows specification of time-integrated irradiation effects while the combination of Voyager and IBEX data supports projection of the in-situ measurements into interstellar space beyond the heliosheath. Transformation of model ion flux distributions into surface sputtering and volume ionization profiles provides a multi-layer perspective for space weathering impact on the affected icy bodies and may account for some aspects of color and compositional diversity. Other important related factors may include surface erosion and gardening by meteoritic impacts and surface renewal by cryovolcanism. Chemical products of space weathering may contribute to energy resources for the latter
Casimir dependence of transverse distribution of pairs produced from a strong constant chromo-electric background field
The transverse distribution of gluon and quark-antiquark pairs produced from
a strong constant chromo-electric field depends on two gauge invariant
quantities, and , as shown earlier in
[G.C. Nayak and P. van Nieuwenhuizen, Phys. Rev. D 71, 125001 (2005)] for
gluons and in [G.C. Nayak, Phys. Rev. D 72, 125010 (2005)] for quarks. Here, we
discuss the explicit dependence of the distribution on the second Casimir
invariant, C_2, and show the dependence is at most a 15% effect.Comment: 5 fig
The Citizen Initiative Petition to Amend State Constitutions: A Concept Whose Time Has Passed, or a Vigorous Component of Participatory Democracy at the State Level?
Leading-Order Auxiliary Field Theory of the Bose-Hubbard Model
We discuss the phase diagram of the Bose-Hubbard (BH) model in the
leading-order auxiliary field (LOAF) theory. LOAF is a conserving
non-perturbative approximation that treats on equal footing the normal and
anomalous density condensates. The mean-field solutions in LOAF correspond to
first-order and second-order phase transition solutions with two critical
temperatures corresponding to a vanishing Bose-Einstein condensate, , and
a vanishing diatom condensate, . The \emph{second-order} phase
transition solution predicts the correct order of the transition in continuum
Bose gases. For either solution, the superfluid state is tied to the presence
of the diatom condensate related to the anomalous density in the system. In
ultracold Bose atomic gases confined on a three-dimensional lattice, the
critical temperature exhibits a quantum phase transition, where
goes to zero at a finite coupling. The BH phase diagram in LOAF features a line
of first-order transitions ending in a critical point beyond which the
transition is second order while approaching the quantum phase transition. We
identify a region where a diatom condensate is expected for temperatures higher
than and less than , the critical temperature of the non-interacting
system. The LOAF phase diagram for the BH model compares qualitatively well
with existing experimental data and results of \emph{ab initio} Monte Carlo
simulations.Comment: 10 pages, 6 figure
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