move this file here from ../src/metrics/

since Mitica Vulcanov has explained to me that it doesn't work
(R(t) isn't known analytically)


git-svn-id: http://svn.einsteintoolkit.org/cactus/EinsteinInitialData/Exact/trunk@174 e296648e-0e4f-0410-bd07-d597d9acff87

1 files changed, 93 insertions, 0 deletions

diff --git a/archive/Robertson_Walker.F77 b/archive/Robertson_Walker.F77
new file mode 100644
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+++ b/archive/Robertson_Walker.F77
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+C Robertson-Walker universe 
+C See: J.N. Islam, An Introduction to 
+C Mathematical Cosmology, Cambridge, 1992
+C
+C Author : D. Vulcanov (Timisoara, Romania)
+C see ../../README for copyright & licensing info
+C
+C $Header$
+
+#include "cctk.h"
+#include "cctk_Parameters.h"
+
+
+      subroutine Exact__Robertson_Walker(
+     $     x, y, z, t,
+     $     gdtt, gdtx, gdty, gdtz, 
+     $     gdxx, gdyy, gdzz, gdxy, gdyz, gdzx,
+     $     gutt, gutx, guty, gutz, 
+     $     guxx, guyy, guzz, guxy, guyz, guzx,
+     $     psi, Tmunu_flag,
+     $     rama)
+
+      implicit none
+
+      DECLARE_CCTK_PARAMETERS
+      DECLARE_CCTK_FUNCTIONS      
+
+c input arguments
+      CCTK_REAL x, y, z, t
+
+c output arguments
+      CCTK_REAL gdtt, gdtx, gdty, gdtz, 
+     $       gdxx, gdyy, gdzz, gdxy, gdyz, gdzx,
+     $       gutt, gutx, guty, gutz, 
+     $       guxx, guyy, guzz, guxy, guyz, guzx
+      CCTK_REAL psi
+      LOGICAL   Tmunu_flag
+      CCTK_REAL rama
+
+c local static variables
+      logical firstcall
+      CCTK_REAL kapa
+      data firstcall /.true./
+      save firstcall, kapa
+
+c local variables
+      CCTK_REAL r2,x2,y2,z2,am,ag
+
+C This model may set the stress-energy tensor
+      Tmunu_flag = .true.
+
+      if (firstcall) then
+          kapa = Robertson_Walker__k
+          firstcall = .false.
+      end if
+
+      x2=x*x
+      y2=y*y
+      z2=z*z
+      r2 = x2+y2+z2
+
+      ag = kapa/(1.0D0-kapa*r2)    
+       
+      am = rama*rama
+       
+
+
+      gdtt = -1.0D0 
+      gdtx = 0.0D0 
+      gdty = 0.0D0
+      gdtz = 0.0D0
+      gdxx = am*(1.0D0 + ag*x2) 
+      gdyy = am*(1.0D0 + ag*y2)
+      gdzz = am*(1.0D0 + ag*z2)
+      gdxy = am*ag*x*y
+      gdyz = am*ag*y*z
+      gdzx = am*ag*z*x
+
+      gutt = -1.0D0
+      gutx = 0.0D0
+      guty = 0.0D0
+      gutz = 0.0D0
+      guxx = (1.0D0-kapa*x2)/am 
+      guyy = (1.0D0-kapa*y2)/am
+      guzz = (1.0D0-kapa*z2)/am
+      guxy = -kapa*x*y/am
+      guyz = -kapa*y*z/am
+      guzx = -kapa*z*x/am
+ 
+
+
+      return
+      end