/* Copyright (C) 2004 Viktor T. Toth <http://www.vttoth.com/>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of
 * the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be
 * useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 * Classification of the Taub-Nut plane vacuum space
 *
 */

if get('ctensor,'version)=false then load(ctensor);
("Computing the Petrov classification of the Taub-Nut plane vacuum")$
("We use frames")$
cframe_flag:true;
("We set up the metric by hand")$
ct_coords:[t,x,y,z];
(lfg:ident(4),lfg[1,1]:-1,lfg);
fri:matrix(
[  -z^(-1/4)/sqrt(2),0,0,%i*z^(-1/4)/sqrt(2)],
[%i*z^(-1/4)/sqrt(2),0,0,  -z^(-1/4)/sqrt(2)],
[0,-sqrt(z)/sqrt(2), sqrt(z)/sqrt(2),0],
[0,-sqrt(z)/sqrt(2),-sqrt(z)/sqrt(2),0]
);
cmetric(false);
ug:invert(lg)$
nptetrad(false);
weyl(false);
psi(false);
("And obtain the Petrov class")$
petrov();

/* End of demo -- comment line needed by MAXIMA to resume demo menu */