64,538 research outputs found

    The Singularity in Generic Gravitational Collapse Is Spacelike, Local, and Oscillatory

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    A longstanding conjecture by Belinskii, Khalatnikov, and Lifshitz that the singularity in generic gravitational collapse is spacelike, local, and oscillatory is explored analytically and numerically in spatially inhomogeneous cosmological spacetimes. With a convenient choice of variables, it can be seen analytically how nonlinear terms in Einstein's equations control the approach to the singularity and cause oscillatory behavior. The analytic picture requires the drastic assumption that each spatial point evolves toward the singularity as an independent spatially homogeneous universe. In every case, detailed numerical simulations of the full Einstein evolution equations support this assumption.Comment: 7 pages includes 4 figures. Uses Revtex and psfig. Received "honorable mention" in 1998 Gravity Research Foundation essay contest. Submitted to Mod. Phys. Lett.

    Harmonic coordinate method for simulating generic singularities

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    This paper presents both a numerical method for general relativity and an application of that method. The method involves the use of harmonic coordinates in a 3+1 code to evolve the Einstein equations with scalar field matter. In such coordinates, the terms in Einstein's equations with the highest number of derivatives take a form similar to that of the wave equation. The application is an exploration of the generic approach to the singularity for this type of matter. The preliminary results indicate that the dynamics as one approaches the singularity is locally the dynamics of the Kasner spacetimes.Comment: 5 pages, 4 figures, Revtex, discussion expanded, references adde

    New England 2020: A Forecast of Educational Attainment and its Implications for the Workforce of New England states.

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    This report examines the role for race and ethnicity in supporting New England's population grouth. The educational attainment throughout New England is assessed as the basis of a forecast of future levels of educational success, and the workforce capability. Finally, public policy opportunites are suggested that can improve economic outcomes during the expected decrease in population growth.education, graduation, minority, demographics, migration, workforce, degrees,

    The nature of gravitational singularities

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    The nature of gravitational singularities, long mysterious, has now become clear through a combination of mathematical and numerical analysis. As the singularity is approached, the time derivative terms in the field equations dominate, and the singularity behaves locally like a homogeneous oscillatory spacetime.Comment: received "honorable mention" in Gravity Research Foundation essay contes

    Hard exclusive photoproduction of Φ\Phi and J/ΨJ/\Psi mesons

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    We present predictions for differential cross sections for the reaction γpΦp\gamma p \to \Phi p and give an outlook to which extent our calculations may be generalized to the photoproduction of J/ΨJ/\Psi mesons. Our results are obtained within perturbative QCD treating the proton as a quark-diquark system.Comment: 4 pages, 1 figure, uses Elsevier style espcrc1.st

    Timelike Compton scattering: exclusive photoproduction of lepton pairs

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    We investigate the exclusive photoproduction of a heavy timelike photon which decays into a lepton pair, gamma p -> l+ l- p. This can be seen as the analog of deeply virtual Compton scattering, and we argue that the two processes are complementary for studying generalized parton distributions in the nucleon. In an unpolarized experiment the angular distribution of the leptons readily provides access to the real part of the Compton amplitude. We estimate the possible size of this effect in kinematics where the Compton process should be dominated by quark exchange.Comment: 31 pages, 17 figure
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