4,258 research outputs found
A Classical Treatment of Island Cosmology
Computing the perturbation spectrum in the recently proposed Island Cosmology
remains an open problem. In this paper we present a classical computation of
the perturbations generated in this scenario by assuming that the NEC-violating
field behaves as a classical phantom field. Using an exactly-solvable
potential, we show that the model generates a scale-invariant spectrum of
scalar perturbations, as well as a scale-invariant spectrum of gravitational
waves. The scalar perturbations can have sufficient amplitude to seed
cosmological structure, while the gravitational waves have a vastly diminished
amplitude.Comment: 8 pages, 1 figur
Nucleosynthesis in the early history of the solar system
Nucleosynthesis in early history of solar syste
Foreword
The Symposium entitled American Justice at a Crossroads: A Public and Private Crisis was held at Pepperdine University School of Law on April 15, 2010, under the joint sponsorship of the Straus Institute for Dispute Resolution, the Pepperdine Dispute Resolution Law Journal, and the International Institute for Conflict Prevention and Resolution (CPR). It brought together a distinguished group of speakers and panelists to discuss dissatisfaction with the American justice system caused by increased delays, rising litigation costs, and decreased access to justice; and creative ways being used to address these concerns
Prevalence, incidence and etiology of hyponatremia in elderly patients with fragility fractures
Peer reviewedPublisher PD
Entropic issues in contemporary cosmology
Penrose [1] has emphasized how the initial big bang singularity requires a
special low entropy state. We address how recent brane cosmological schemes
address this problem and whether they offer any apparent resolution. Pushing
the start time back to or utilizing maximally symmetric AdS spaces
simply exacerbates or transfers the problem.
Because the entropy of de Sitter space is , using the
present acceleration of the universe as a low energy )
inflationary stage, as in cyclic ekpyrotic models, produces a gravitational
heat death after one cycle. Only higher energy driven inflation, together with
a suitable, quantum gravity holography style, restriction on {\em ab initio}
degrees of freedom, gives a suitable low entropy initial state. We question the
suggestion that a high energy inflationary stage could be naturally reentered
by Poincare recurrence within a finite causal region of an accelerating
universe.
We further give a heuristic argument that so-called eternal inflation is not
consistent with the 2nd law of thermodynamics within a causal patch.Comment: brief discussion on Poincare recurrence include
The Maxwell–Vlasov equations in Euler–Poincaré form
Low's well-known action principle for the Maxwell–Vlasov equations of ideal plasma dynamics was originally expressed in terms of a mixture of Eulerian and Lagrangian variables. By imposing suitable constraints on the variations and analyzing invariance properties of the Lagrangian, as one does for the Euler equations for the rigid body and ideal fluids, we first transform this action principle into purely Eulerian variables. Hamilton's principle for the Eulerian description of Low's action principle then casts the Maxwell–Vlasov equations into Euler–Poincaré form for right invariant motion on the diffeomorphism group of position-velocity phase space, [openface R]6. Legendre transforming the Eulerian form of Low's action principle produces the Hamiltonian formulation of these equations in the Eulerian description. Since it arises from Euler–Poincaré equations, this Hamiltonian formulation can be written in terms of a Poisson structure that contains the Lie–Poisson bracket on the dual of a semidirect product Lie algebra. Because of degeneracies in the Lagrangian, the Legendre transform is dealt with using the Dirac theory of constraints. Another Maxwell–Vlasov Poisson structure is known, whose ingredients are the Lie–Poisson bracket on the dual of the Lie algebra of symplectomorphisms of phase space and the Born–Infeld brackets for the Maxwell field. We discuss the relationship between these two Hamiltonian formulations. We also discuss the general Kelvin–Noether theorem for Euler–Poincaré equations and its meaning in the plasma context
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