5,522 research outputs found
A brief review of Regge calculus in classical numerical relativity
We briefly review past applications of Regge calculus in classical numerical
relativity, and then outline a programme for the future development of the
field. We briefly describe the success of lattice gravity in constructing
initial data for the head-on collision of equal mass black holes, and discuss
recent results on the efficacy of Regge calculus in the continuum limit.Comment: 2 pages, submitted to the Proceedings of the IX Marcel Grossmann
Meeting, Rome, July 2-8, 200
Advanced techniques and technology for efficient data storage, access, and transfer
Advanced techniques for efficiently representing most forms of data are being implemented in practical hardware and software form through the joint efforts of three NASA centers. These techniques adapt to local statistical variations to continually provide near optimum code efficiency when representing data without error. Demonstrated in several earlier space applications, these techniques are the basis of initial NASA data compression standards specifications. Since the techniques clearly apply to most NASA science data, NASA invested in the development of both hardware and software implementations for general use. This investment includes high-speed single-chip very large scale integration (VLSI) coding and decoding modules as well as machine-transferrable software routines. The hardware chips were tested in the laboratory at data rates as high as 700 Mbits/s. A coding module's definition includes a predictive preprocessing stage and a powerful adaptive coding stage. The function of the preprocessor is to optimally process incoming data into a standard form data source that the second stage can handle.The built-in preprocessor of the VLSI coder chips is ideal for high-speed sampled data applications such as imaging and high-quality audio, but additionally, the second stage adaptive coder can be used separately with any source that can be externally preprocessed into the 'standard form'. This generic functionality assures that the applicability of these techniques and their recent high-speed implementations should be equally broad outside of NASA
Time in Quantum Geometrodynamics
We revisit the issue of time in quantum geometrodynamics and suggest a
quantization procedure on the space of true dynamic variables. This procedure
separates the issue of quantization from enforcing the constraints caused by
the general covariance symmetries. The resulting theory, unlike the standard
approach, takes into account the states that are off shell with respect to the
constraints, and thus avoids the problems of time. In this approach, quantum
geometrodynamics, general covariance, and the interpretation of time emerge
together as parts of the solution of the total problem of geometrodynamic
evolution.Comment: 17 pages, 0 figures, formatted with LaTex, IJMP-A in pres
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