10,365 research outputs found
The Complementarity of Eastern and Western Hemisphere Long-Baseline Neutrino Oscillation Experiments
We present a general formalism for extracting information on the fundamental
parameters associated with neutrino masses and mixings from two or more long
baseline neutrino oscillation experiments. This formalism is then applied to
the current most likely experiments using neutrino beams from the Japan Hadron
Facility (JHF) and Fermilab's NuMI beamline. Different combinations of muon
neutrino or muon anti-neutrino running are considered. To extract the type of
neutrino mass hierarchy we make use of the matter effect. Contrary to naive
expectation, we find that both beams using neutrinos is more suitable for
determining the hierarchy provided that the neutrino energy divided by baseline
() for NuMI is smaller than or equal to that of JHF. Whereas to determine
the small mixing angle, , and the CP or T violating phase
, one neutrino and the other anti-neutrino is most suitable. We make
extensive use of bi-probability diagrams for both understanding and extracting
the physics involved in such comparisons.Comment: 21 pages, Latex, 3 postscript figure
Reconstructing the Properties of Dark Energy using Standard Sirens
Future space-based gravity wave experiments such as the Big Bang Observatory
(BBO), with their excellent projected, one sigma angular resolution, will
measure the luminosity distance to a large number of gravity wave (GW) sources
to high precision, and the redshift of the single galaxies in the narrow solid
angles towards the sources will provide the redshifts of the gravity wave
sources. One sigma BBO beams contain the actual source only in 68 per cent
cases; the beams that do not contain the source may contain a spurious single
galaxy, leading to misidentification. To increase the probability of the source
falling within the beam, larger beams have to be considered, decreasing the
chances of finding single galaxies in the beams. Saini, Sethi and Sahni (2010)
argued, largely analytically, that identifying even a small number of GW source
galaxies furnishes a rough distance-redshift relation, which could be used to
further resolve sources that have multiple objects in the angular beam. In this
work we further develop this idea by introducing a self-calibrating iterative
scheme which works in conjunction with Monte-Carlo simulations to determine the
luminosity distance to GW sources with progressively greater accuracy. This
iterative scheme allows one to determine the equation of state of dark energy
to within an accuracy of a few percent for a gravity wave experiment possessing
a beam width an order of magnitude larger than BBO (and therefore having a far
poorer angular resolution). This is achieved with no prior information about
the nature of dark energy from other data sets such as SN Ia, BAO, CMB etc.Comment: 12 pages, 10 figures. Expanded discussion, additional references.
Main results unchanged. Matches published versio
Nonlinear theory for coalescing characteristics in multiphase Whitham modulation theory
The multiphase Whitham modulation equations with phases have
characteristics which may be of hyperbolic or elliptic type. In this paper a
nonlinear theory is developed for coalescence, where two characteristics change
from hyperbolic to elliptic via collision. Firstly, a linear theory develops
the structure of colliding characteristics involving the topological sign of
characteristics and multiple Jordan chains, and secondly a nonlinear modulation
theory is developed for transitions. The nonlinear theory shows that coalescing
characteristics morph the Whitham equations into an asymptotically valid
geometric form of the two-way Boussinesq equation. That is, coalescing
characteristics generate dispersion, nonlinearity and complex wave fields. For
illustration, the theory is applied to coalescing characteristics associated
with the modulation of two-phase travelling-wave solutions of coupled nonlinear
Schr\"odinger equations, highlighting how collisions can be identified and the
relevant dispersive dynamics constructed.Comment: 40 pages, 2 figure
Concurrent extensions to the FORTRAN language for parallel programming of computational fluid dynamics algorithms
Experiments were conducted at NASA Ames Research Center to define multi-tasking software requirements for multiple-instruction, multiple-data stream (MIMD) computer architectures. The focus was on specifying solutions for algorithms in the field of computational fluid dynamics (CFD). The program objectives were to allow researchers to produce usable parallel application software as soon as possible after acquiring MIMD computer equipment, to provide researchers with an easy-to-learn and easy-to-use parallel software language which could be implemented on several different MIMD machines, and to enable researchers to list preferred design specifications for future MIMD computer architectures. Analysis of CFD algorithms indicated that extensions of an existing programming language, adaptable to new computer architectures, provided the best solution to meeting program objectives. The CoFORTRAN Language was written in response to these objectives and to provide researchers a means to experiment with parallel software solutions to CFD algorithms on machines with parallel architectures
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