I want to solve the heat equation using the finite difference method. Here is my code:

```
θ[j_, n_] := θ[j, n] =
2*θ[j, n - 1] - θ[j, n - 2] + (Δt)^2*
Gz*(1 - (Subscript[x, j])^2)*((θ[j + 1, n - 1] - θ[
j - 1, n - 1])/(
2*Δx))*(1 + (
3 γ^3 (λ^2 - (Subscript[x,
j])^2))/(-γ^3*(1 + (Subscript[x, j])^2)^3 +
3*γ*(1 + (Subscript[x, j])^2) -
3 Tanh[(1 + (Subscript[x, j])^2) γ])*1/
2*(t^2 - 1) (1 + (Subscript[x, j])^2)^2 + 1/γ^2 -
Cosh[(1 + (Subscript[x, j])^2) t γ]/(γ^2*
Cosh[(1 + (Subscript[x,
j])^2) γ])) - (Δt)^2*
Br ((3 γ^3 (λ^2 - (Subscript[x,
j])^2))/(-γ^3*(1 + (Subscript[x, j])^2)^3 +
3*γ*(1 + (Subscript[x, j])^2) -
3 Tanh[(1 + (Subscript[x,
j])^2) γ]))^2*((t*(1 + (Subscript[x, j])^2)^2 -
1/(γ*
Cosh[γ*(1 + (Subscript[x, j])^2)]) (1 + (Subscript[
x, j])^2)^2*
Sinh[γ*(1 + Subscript[x, j]^2)*t])^2 + (1 +
Subscript[x, j]^2)/γ^2*(1 -
Cosh[γ*(1 + Subscript[x, j]^2)*t]/
Cosh[γ*(1 + Subscript[x, j]^2)])^2);
Br = 5;
Gz = 20;
γ = 6;
λ = 0.2923;
Subscript[x, j] = (j - 1) Δx;
θ[j_, 1] = θ1[t] /. t -> n*Δt;
θ[j_, -1] = θ2[t] /. t -> -n*Δt;
θ[-10, n_] = θ0[x] /. x -> j*Δx;
m = 10;
L = 1; Δt = 0.1; Δx = 0.1;
θ0[x_] = 0;
θ1[t_] = 0;
θ2[t_] = 0;
Table[ListPlot[
Table[{Δt*n, θ[j, n]}, {n, -m, m}],
Joined -> True, PlotRange -> {0, 0.03}, AxesLabel -> {"x", ""},
PlotLabel ->
"θ[x,t], x=" <> ToString[Δx j]], {j, -6, 2,
2}]
```

But I get the error:

RecursionLimit::reclim2: Recursion depth of 1024 exceeded during evaluation of 2 θ[-6, -1030 -1] – θ