12,511 research outputs found
A note on the metallization of compressed liquid hydrogen
We examine the molecular-atomic transition in liquid hydrogen as it relates
to metallization. Pair potentials are obtained from first principles molecular
dynamics and compared with potentials derived from quadratic response. The
results provide insight into the nature of covalent bonding under extreme
conditions. Based on this analysis, we construct a schematic
dissociation-metallization phase diagram and suggest experimental approaches
that should significantly reduce the pressures necessary for the realization of
the elusive metallic phase of hydrogen.Comment: 11 pages, 4 figure
Classical planar algebraic curves realizable by quadratic polynomial differential systems
In this paper we show planar quadratic polynomial differentialsystems exhibiting as solutions some famous planar invariant algebraic curves. Also we put particular attention to the Darboux integrability of these differential systems.The author is partially supported by a MINECO grant number MTM2014-53703-P and an AGAUR grant number 2014SGR1204.
†The author is partially supported by a FEDER-MINECO grant MTM2016-77278-P, a MINECO grant MTM2013-40998-P, and an AGAUR grant number 2014SGR-56
Runaway of Line-Driven Winds Towards Critical and Overloaded solutions
Line-driven winds from hot stars and accretion disks are thought to adopt a
unique, critical solution which corresponds to maximum mass loss rate and a
particular velocity law. We show that in the presence of negative velocity
gradients, radiative-acoustic (Abbott) waves can drive shallow wind solutions
towards larger velocities and mass loss rates. Perturbations introduced
downstream from the wind critical point lead to convergence towards the
critical solution. By contrast, low-lying perturbations cause evolution towards
a mass-overloaded solution, developing a broad deceleration region in the wind.
Such a wind differs fundamentally from the critical solution. For sufficiently
deep-seated perturbations, overloaded solutions become time-dependent and
develop shocks and shells.Comment: Latex, 2 postscript figures Astrophysical Journal Letters, in pres
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