Date: Mon, 16 Mar 1998 09:09:21 -0600
Subject: Numerical Astrophysics Tokyo, brief report


Dear NumeRels.

I attended the conference "Numerical Astrophysics 98" at Tokyo,
last week. Here is a brief report of what you might be interested in.

T. Nakamura : A way to 3D NR - coalescing binary NSs
invited talk.
Full 3D NR effort was introduced. Recently 180 degree rotation of NS
binary was done. The main reasons to stop evolution are CPU time and
the treatment of surface of NSs. He uses gamma=2 polytropic EOS.
They plan to apply Yabe's CIP method (comment later) to this problem.

K. Oohara : Elliptic equations in NR
His poster is of boundary conditions of momentum constraint eqs.,
which are explained in Progress. Theo. Phys. Suppl., and which I
applied in my initial data thorn.  In private discussion, he says that
he doubts Wilson-Mathews's results are come from this boundary
treatment. He himself had an experience of BH collapse from NS
binary with simple BC (but it was when he has still a small bug
in hydro part.)

M. Shibata : Stability of coalescing binary stars against
             gravitational collapse: hydrodynamical simulations
contributed talk.
Full PN evolution simulation. After confirming the unstable branch
of NS evolves collapsing phase, try the similar calculation with
Wilson-Mathews, but could not find the evidence to form BH from
stable NS binary. He uses sophisticated BC than Wilson-Mathews's.

S. Shapiro : BHs and GWs: spacetime engineering
invited talk.
No new results. EH formation from clouds and toroidal BH formation
were shown. Basically, the same talk at Chandra's simposium Dec/96
at Chicago.

M. Ruffert : coalescing NSs: gamma-ray bursts and GWs
invited talk.
His Newtonian binary NS simulations were shown. New parts were
different mass binary, inspiral/headon, with nested grid.
Temperature of stars are not yet sufficient to explain emitted
gamma-ray luminocity.

------------------------------------------------------------------
Takeshi Yabe (Tokyo Institute of Tech.) : A dream to solve all
   phases of matter together with the CIP method.
invited talk.
He presented his CIP (cubic interpolate) method for hydrodynamics.
The basic idea is to make derivative of the fundamental equations
(apply proper artificial viscosity from the theoretical consitency)
and take gradients of normal variables as fundamental variables.
Then it enables to treat shocks with few grids without AMR. This
technique was developped few years ago and become popular in Japan.
"All phases" in title means solid, liquid and gas. I am collecting
references. I will report more details when I came back St.Louis.
There is no application to GR yet. It might be interesting
to try plane-symmetric wave collisions with this method in GR.


------------------------------------------------------------------
other comments:

1) AMR became standard in all fields such as cosmology, MHD, protostars,
clouds, ...
2) The latest largest SPH is by H. Couchman (Tronto) with 10^9 particles.
But no physics discussion.
3) Most talks were with videos. This proceedings will provide with
CD-rom. Each contributers limit is 640KB.


Ciao.

Hisaaki SHINKAI
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