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! $Header$
#include "cctk.h"
#undef DEBUG
module ricci4
implicit none
private
public calc_4connections
public calc_4connectionderivs
public calc_4ricci
public calc_4riemann
public calc_4weyl
contains
subroutine calc_4connections (gu, dg, gamma)
CCTK_REAL, intent(in) :: gu(4,4), dg(4,4,4)
CCTK_REAL, intent(out) :: gamma(4,4,4)
integer :: i,j,k,l
! Gamma^i_jk = 1/2 g^il (g_lj,k + g_lk,j - g_jk,l)
do i=1,4
do j=1,4
do k=1,4
gamma(i,j,k) = 0
do l=1,4
gamma(i,j,k) = gamma(i,j,k) + 0.5d0 * gu(i,l) &
* (dg(l,j,k) + dg(l,k,j) - dg(j,k,l))
end do
end do
end do
end do
end subroutine calc_4connections
subroutine calc_4connectionderivs (gu, dgg, dgu, ddgg, dgamma)
CCTK_REAL, intent(in) :: gu(4,4), dgg(4,4,4), dgu(4,4,4), ddgg(4,4,4,4)
CCTK_REAL, intent(out) :: dgamma(4,4,4,4)
integer :: i,j,k,l,m
! Gamma^i_jk,l = 1/2 g^im,l (g_mj,k + g_mk,j - g_jk,m)
! + 1/2 g^im (g_mj,kl + g_mk,jl - g_jk,ml)
do i=1,4
do j=1,4
do k=1,4
do l=1,4
dgamma(i,j,k,l) = 0
do m=1,4
dgamma(i,j,k,l) = dgamma(i,j,k,l) &
+ 0.5d0 * dgu(i,m,l) * (dgg(m,j,k) + dgg(m,k,j) - dgg(j,k,m)) &
+ 0.5d0 * gu(i,m) * (ddgg(m,j,k,l) + ddgg(m,k,j,l) - ddgg(j,k,m,l))
end do
end do
end do
end do
end do
end subroutine calc_4connectionderivs
subroutine calc_4ricci (gamma, dgamma, ri)
CCTK_REAL, intent(in) :: gamma(4,4,4), dgamma(4,4,4,4)
CCTK_REAL, intent(out) :: ri(4,4)
#ifdef DEBUG
CCTK_REAL :: nrm, cnt
#endif
integer :: i,j,k,l
! R_ij = Gamma^k_ij,k - Gamma^k_ik,j
! + Gamma^k_lk Gamma^l_ij - Gamma^k_lj Gamma^l_ki
do i=1,4
do j=1,4
ri(i,j) = 0
do k=1,4
ri(i,j) = ri(i,j) + dgamma(k,i,j,k) - dgamma(k,i,k,j)
do l=1,4
ri(i,j) = ri(i,j) + gamma(k,l,k) * gamma(l,i,j) &
& - gamma(k,l,j) * gamma(l,k,i)
end do
end do
end do
end do
#ifdef DEBUG
! check symmetries
nrm = 0
cnt = 0
do i=1,4
do j=1,4
nrm = nrm + (ri(i,j) - ri(j,i))**2
cnt = cnt + ri(i,j)**2
end do
end do
if (nrm > 1.0e-12 * cnt) call CCTK_WARN (0, "4-Ricci tensor is not symmetric")
#endif
end subroutine calc_4ricci
subroutine calc_4riemann (gg, gamma, dgamma, rm)
CCTK_REAL, intent(in) :: gg(4,4), gamma(4,4,4), dgamma(4,4,4,4)
CCTK_REAL, intent(out) :: rm(4,4,4,4)
CCTK_REAL :: rmu(4,4,4,4)
#ifdef DEBUG
CCTK_REAL :: nrm, cnt
#endif
integer :: i,j,k,l,m
! R^i_jkl = Gamma^i_jl,k - Gamma^i_jk,l
! + Gamma^m_jl Gamma^i_mk - Gamma^m_jk Gamma^i_ml
! (Wald, 3.4, eqn. (3.4.4), p. 48)
do i=1,4
do j=1,4
do k=1,4
do l=1,4
rmu(i,j,k,l) = dgamma(i,j,l,k) - dgamma(i,j,k,l)
do m=1,4
rmu(i,j,k,l) = rmu(i,j,k,l) &
+ gamma(m,j,l) * gamma(i,m,k) &
- gamma(m,j,k) * gamma(i,m,l)
end do
end do
end do
end do
end do
do i=1,4
do j=1,4
do k=1,4
do l=1,4
rm(i,j,k,l) = 0
do m=1,4
rm(i,j,k,l) = rm(i,j,k,l) + gg(i,m) * rmu(m,j,k,l)
end do
end do
end do
end do
end do
#ifdef DEBUG
! check symmetries
nrm = 0
cnt = 0
do i=1,4
do j=1,4
do k=1,4
do l=1,4
nrm = nrm + (rm(i,j,k,l) + rm(i,j,l,k))**2
nrm = nrm + (rm(i,j,k,l) - rm(k,l,i,j))**2
nrm = nrm + (rm(i,j,k,l) + rm(j,i,k,l))**2
nrm = nrm + (rm(i,j,k,l) + rm(j,k,i,l) + rm(k,i,j,l))**2
cnt = cnt + rm(i,j,k,l)**2
end do
end do
end do
end do
if (nrm > 1.0e-12 * cnt) call CCTK_WARN (0, "4-Riemann tensor is not symmetric")
#endif
end subroutine calc_4riemann
subroutine calc_4weyl (gg, rm, ri, rsc, we)
CCTK_REAL, parameter :: one=1, half=one/2, third=one/3
CCTK_REAL, intent(in) :: gg(4,4), rm(4,4,4,4), ri(4,4), rsc
CCTK_REAL, intent(out) :: we(4,4,4,4)
#ifdef DEBUG
CCTK_REAL :: nrm, cnt
#endif
integer :: i,j,k,l
! R_ijkl = C_ijkl + 2/(n-2) (g_i[k R_l]j - g_j[k R_l]i)
! - 2/(n-1)(n-2) R g_i[k g_l]j
! (Wald, 3.2, eqn. (3.2.28), p. 40)
do i=1,4
do j=1,4
do k=1,4
do l=1,4
we(i,j,k,l) = rm(i,j,k,l) &
- ( (gg(i,k) * ri(l,j) - gg(i,l) * ri(k,j)) &
& - (gg(j,k) * ri(l,i) - gg(j,l) * ri(k,i))) &
+ third * rsc * (gg(i,k) * gg(l,j) - gg(i,l) * gg(k,j))
end do
end do
end do
end do
#ifdef DEBUG
! check symmetries
nrm = 0
cnt = 0
do i=1,4
do j=1,4
do k=1,4
do l=1,4
nrm = nrm + (we(i,j,k,l) + we(i,j,l,k))**2
nrm = nrm + (we(i,j,k,l) - we(k,l,i,j))**2
nrm = nrm + (we(i,j,k,l) + we(j,i,k,l))**2
nrm = nrm + (we(i,j,k,l) + we(j,k,i,l) + we(k,i,j,l))**2
cnt = cnt + we(i,j,k,l)**2
end do
end do
end do
end do
if (nrm > 1.0e-12 * cnt) call CCTK_WARN (0, "4-Weyl tensor is not symmetric")
#endif
end subroutine calc_4weyl
end module ricci4
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