30,005 research outputs found
Response to "The invalidity of a Mach probe model" [Phys. Plasmas 9, 1832 (2002)]
Hutchinson gives a nice analysis of the (in)validity of Hudis and Lidsky’s unmagnetized Mach probe theory.(1) We agree with his main assertions, which are that (1) a one-dimensional model is incapable of properly describing unmagnetized ion collection by a Mach probe and (2) any experimental agreement with theories based on Hudis and Lidsky should not be interpreted as physical validation of their model
Clustering in Hilbert space of a quantum optimization problem
The solution space of many classical optimization problems breaks up into
clusters which are extensively distant from one another in the Hamming metric.
Here, we show that an analogous quantum clustering phenomenon takes place in
the ground state subspace of a certain quantum optimization problem. This
involves extending the notion of clustering to Hilbert space, where the
classical Hamming distance is not immediately useful. Quantum clusters
correspond to macroscopically distinct subspaces of the full quantum ground
state space which grow with the system size. We explicitly demonstrate that
such clusters arise in the solution space of random quantum satisfiability
(3-QSAT) at its satisfiability transition. We estimate both the number of these
clusters and their internal entropy. The former are given by the number of
hardcore dimer coverings of the core of the interaction graph, while the latter
is related to the underconstrained degrees of freedom not touched by the
dimers. We additionally provide new numerical evidence suggesting that the
3-QSAT satisfiability transition may coincide with the product satisfiability
transition, which would imply the absence of an intermediate entangled
satisfiable phase.Comment: 11 pages, 6 figure
Tendency of spherically imploding plasma liners formed by merging plasma jets to evolve toward spherical symmetry
Three dimensional hydrodynamic simulations have been performed using smoothed
particle hydrodynamics (SPH) in order to study the effects of discrete jets on
the processes of plasma liner formation, implosion on vacuum, and expansion.
The pressure history of the inner portion of the liner was qualitatively and
quantitatively similar from peak compression through the complete stagnation of
the liner among simulation results from two one dimensional
radiationhydrodynamic codes, 3D SPH with a uniform liner, and 3D SPH with 30
discrete plasma jets. Two dimensional slices of the pressure show that the
discrete jet SPH case evolves towards a profile that is almost
indistinguishable from the SPH case with a uniform liner, showing that
non-uniformities due to discrete jets are smeared out by late stages of the
implosion. Liner formation and implosion on vacuum was also shown to be robust
to Rayleigh-Taylor instability growth. Interparticle mixing for a liner
imploding on vacuum was investigated. The mixing rate was very small until
after peak compression for the 30 jet simulation.Comment: 28 pages, 16 figures, submitted to Physics of Plasmas (2012
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