Locating Boosted Kerr and Schwarzschild Apparent Horizons

We describe a finite-difference method for locating apparent horizons and illustrate its capabilities on boosted Kerr and Schwarzschild black holes. Our model spacetime is given by the Kerr-Schild metric. We apply a Lorentz boost to this spacetime metric and then carry out a 3+1 decomposition. The result is a slicing of Kerr/Schwarzschild in which the black hole is propagated and Lorentz contracted. We show that our method can locate distorted apparent horizons efficiently and accurately.Comment: Submitted to Physical Review D. 12 pages and 22 figure

Use of SMS texts for facilitating access to online alcohol interventions: a feasibility study

A41 Use of SMS texts for facilitating access to online alcohol interventions: a feasibility study In: Addiction Science & Clinical Practice 2017, 12(Suppl 1): A4

Problem of unstable pivots in the incomplete LU-conjugate gradient method

Incomplete LU and incomplete-Cholesky conjugate gradient methods are becoming widely used in both laser and magnetic fusion research. In my original presentation of these methods, the problem of what to do if a pivot (L/sub ii/U/sub ii/) becomes very small or zero was raised and only partially answered by the suggestion that it be arbitrarily set to some non-zero value. In what follows it will be shown precisely how small the pivot can become before it must be fixed and precisely what value it should be set to in order to minimize the error in LU. Numerical examples will be given to show that not only does this prescription improve incomplete LU-conjugate gradient methods , but exact LU decomposition carried out with this prescription for handling small pivots and followed by a few linear or conjugate gradient iterations can be much faster than the permutations of rows and columns usually employed to circumvent small pivot problems

Computer simulation of superthermal transport for laser fusion

The relativistic multigroup diffusion equations describing superthermal electron transport in laser fusion plasmas were derived in an earlier UCRL. A successful numerical scheme based on these equations which is now being used to model laser fusion experiments is described

Flux limiting nature`s own way -- A new method for numerical solution of the transport equation

The transport equation may be solved by expanding it in spherical harmonics, Y{sub lm}, and truncating the resultant infinite set of equations at some finite order L. This procedure leaves the (L + 1)th order moments which appear in the Lth order equation undetermined, and the standard procedure for obtaining a closed set of equations has been to set all the (L + 1)th order moments to zero. It has been shown here that this procedure actually violates the apriori knowledge that one is solving for the moments of a probability measure on the unit sphere. Using the theory of moments of a probability measure on the unit sphere. Using the theory of moments as discussed above, the (L + 1)th order moments can be chosen in accordance with apriori knowledge. The resultant truncated set of equations has properties much truer to the original transport equation than the usual set obtained by setting the (L + 1)th order moments to zero. In particular the truncated set of equations gets the solution of the transport equation exactly right in both the diffusion limit and the free streaming limit. Furthermore, this has been achieved by merely truncating the set of equations properly and not by any ad hoc changes in the basic equations as is the case in the approaches that use flux limiters

Interaction of relativistic electron beams with high Z plasmas

A set of relativistic multigroup diffusion equations was derived for the study of electron beam--target interactions. Included are transport, Coulomb collisions, electric and magnetic fields, bremsstrahlung, and hydrodynamic motion of the background plasma. LASNEX, the Laser-Fusion code, is being modified to include these equations and will be used for modeling electron beam fusion. (auth