7,374 research outputs found
Curvature corrections in DGP brane cosmology
We consider a DGP inspired brane scenario where the action on the brane is
augmented by a function of the Ricci scalar, . The cosmological
implications that such a scenario entails are examined for and shown to
be consistent with a universe expanding with power-law acceleration. It is
shown that two classes of solutions exist for the usual FRW metric and small
Hubble radii. When the Hubble radius becomes larger, we either have a
transition to a fully 5D regime or to a self-inflationary solution which
produces a late accelerated expansion such that the radius becomes a function
of .Comment: 11 pages, 2 figure
Some photometer results obtained on the NASA 1969 Airborne Auroral Expedition
The spectral features measured by a photometer onboard the Convair 990 Galileo, during the Auroral Expedition are given in tables. The measurements given cover flights 3 to 15
Operational parameters for the superconducting cavity maser
Tests of the superconducting cavity maser (SCM) ultra-stable frequency source have been made for the first time using a hydrogen maser for a frequency reference. In addition to characterizing the frequency stability, the sensitivity of the output frequency to several crucial parameters was determined for various operating conditions. Based on this determination, the refrigeration and thermal control systems of the SCM were modified. Subsequent tests showed substantially improved performance, especially at the longest averaging times
Gravity induced over a smooth soliton
I consider gravity induced over a smooth (finite thickness) soliton. Graviton
kinetic term is coupled to bulk scalar that develops solitonic vacuum
expectation value. Couplings of Kaluza-Klein modes to soliton-localized matter
are suppressed, giving rise to crossover distance between
4D and 5D behavior. This system can be viewed as a finite thickness brane
regularization of the model of Dvali, Gabadadze and Porrati.Comment: 12 pages, 2 figure
Development of a breadboard model correlation interferometer for the carbon monoxide pollution experiment
The breadboard model of the correlation interferometer for the Carbon Monoxide Pollution Experiment has been designed, fabricated, and tested. Laboratory, long-path, and atmospheric tests which were performed show the technique to be a feasible method for obtaining a global carbon monoxide map and a vertical carbon monoxide profile and similar information is readily obtainable for methane as well. In addition, the technique is readily applicable to other trace gases by minor instrumental changes. As shown by the results and the conclusions, it has been determined that CO and CH4 data can be obtained with an accuracy of 10% using this technique on the spectral region around 2.3 microns
Application of quasi-Monte Carlo methods to PDEs with random coefficients -- an overview and tutorial
This article provides a high-level overview of some recent works on the
application of quasi-Monte Carlo (QMC) methods to PDEs with random
coefficients. It is based on an in-depth survey of a similar title by the same
authors, with an accompanying software package which is also briefly discussed
here. Embedded in this article is a step-by-step tutorial of the required
analysis for the setting known as the uniform case with first order QMC rules.
The aim of this article is to provide an easy entry point for QMC experts
wanting to start research in this direction and for PDE analysts and
practitioners wanting to tap into contemporary QMC theory and methods.Comment: arXiv admin note: text overlap with arXiv:1606.0661
Graviton Mass or Cosmological Constant?
To describe a massive graviton in 4D Minkowski space-time one introduces a
quadratic term in the Lagrangian. This term, however, can lead to a
readjustment or instability of the background instead of describing a massive
graviton on flat space. We show that for all local Lorentz-invariant mass terms
Minkowski space is unstable. We start with the Pauli-Fierz (PF) term that is
the only local mass term with no ghosts in the linearized approximation. We
show that nonlinear completions of the PF Lagrangian give rise to instability
of Minkowski space. We continue with the mass terms that are not of a PF type.
Although these models are known to have ghosts in the linearized
approximations, nonlinear interactions can lead to background change due to
which the ghosts are eliminated. In the latter case, however, the graviton
perturbations on the new background are not massive. We argue that a consistent
theory of a massive graviton on flat space can be formulated in theories with
extra dimensions. They require an infinite number of fields or non-local
description from a 4D point of view.Comment: 16 pages; references and comments adde
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