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- g = ({
- {-Exp[2 α[r]], 0, 0, 0},
- {0, Exp[2 β[r]], 0, 0},
- {0, 0, r^2, 0},
- {0, 0, 0, r^2 Sin[θ]^2}
- }) ; T = ({
- {0, 0, 0, 0},
- {0, 0, 0, 0},
- {0, 0, 0, 0},
- {0, 0, 0, 0}
- }); var = {t, r, θ, ϕ};
- h = Inverse[g]; Print["Inverse Metric=" MatrixForm[h]];
- Print[Style[
- "Christoffel Symbol", {Bold, Underlined, Larger}]]; Γ[
- i_, j_, k_] :=
- Sum[1/2 h[[i,
- l]] (D[g[[k, l]], var[[j]]] + D[g[[j, l]], var[[k]]] -
- D[g[[k, j]], var[[l]]]), {l, 1, 4}]; i := 1; j := 1; k := 1;
- For[i = 1, i <= 4, i++,
- For[j = 1, j <= 4, j++,
- For[If[j < k, k = j], k <= 4, k++,
- If[Γ[i, j, k] =!= 0,
- Print[Subscript[Γ, var[[j]], var[[k]]]^var[[i]],
- "=", FullSimplify[Γ[i, j, k]]]]]]];
- Print[Style["Riemann Tensor", {Bold, Underlined, Larger}]];
- RiemannTensor[a_, b_, c_,
- d_] := (D[Γ[a, d, b],
- var[[c]]]) - (D[Γ[a, c, b],
- var[[d]]]) + Γ[a, c, 1] Γ[1, d,
- b] + Γ[a, c, 2] Γ[2, d,
- b] + Γ[a, c, 3] Γ[3, d,
- b] + Γ[a, c, 4] Γ[4, d,
- b] - Γ[a, d, 1] Γ[1, b,
- c] - Γ[a, d, 2] Γ[2, b,
- c] - Γ[a, d, 3] Γ[3, b,
- c] - Γ[a, d, 4] Γ[4, b,
- c]; a := 1; b := 1; c := 1; d := 1;
- For[a = 1, a <= 4, a++,
- For[b = 1, b <= 4, b++,
- For[c = 1, c <= 4, c++,
- For[If[c < d, d = c], d <= 4, d++,
- If[RiemannTensor[a, b, c, d] =!= 0,
- Print[Subscript[R^var[[a]], var[[b]], var[[c]], var[[d]]], "=",
- FullSimplify[RiemannTensor[a, b, c, d]]]]]]]];
- Print[Style["Ricci Tensor", {Bold, Underlined, Larger}]];
- RicciTensor[m_, n_] :=
- Sum[RiemannTensor[soma, m, soma, n], {soma, 1, 4}]; m := 1; n := 1
- For[m = 1, m <= 4, m++,
- For[If[m < n, n = m], n <= 4, n++,
- If[RicciTensor[m, n] =!= 0,
- Print[Subscript[R, var[[m]], var[[n]]], "=",
- FullSimplify[RicciTensor[m, n]]]]]];
- Clear[RicciTensor];
- Print[Style[
- "Calculating Ricci Tensor directly, without Riemann Tensor", {Bold,
- Underlined, Larger}]]; alpha := 1; beta := 1;
- RicciTensor[alpha_, beta_] :=
- Sum[D[Γ[rho, beta, alpha], var[[rho]]] -
- D[Γ[rho, rho, alpha],
- var[[beta]]] + Γ[rho, rho, lambda] Γ[
- lambda, beta, alpha] - Γ[rho, beta,
- lambda] Γ[lambda, rho, alpha], {lambda, 1, 4,
- 1}, {rho, 1, 4, 1}];
- For[alpha = 1, alpha <= 4, alpha++,
- For[If[alpha <= beta, beta = alpha], beta <= 4, beta++,
- If[RicciTensor[alpha, beta] =!= 0,
- Print[Subscript[R, var[[alpha]], var[[beta]]], "=",
- FullSimplify[RicciTensor[alpha, beta]]]]]];
- RicciTensor[alpha_, beta_] :=
- Sum[D[Γ[rho, beta, alpha], var[[rho]]] - D[Γ[rho, rho, alpha], var[[beta]]], {rho, 1, 4, 1}]
- + Sum[Γ[rho, rho, lambda] Γ[lambda, beta, alpha]
- - Γ[rho, beta, lambda] Γ[lambda, rho, alpha], {lambda, 1, 4, 1}, {rho, 1, 4, 1}];
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