Jacobson Filtration of the Singular Regular Module

Use the verified branch model

O_sing = Z_3 × R_loc,   R_loc = {(a,b) in Z_3 × Z_3 : a ≡ b mod 3}.

The arithmetic module is the regular module L_sing ≅ O_sing, so the module filtration is the ring filtration.

For the finite quotients modulo 3^k, write

O_k = (Z/3^k Z) × R_k,   R_k = {(a,b) : a ≡ b mod 3}.

Then

|O_k| = 3^(3k-1),
|3 O_k| = 3^(3k-4),
|J_k| = 3^(3k-3),
|J_k^r| = 3^(3k-3r)   (1 <= r <= k),

where J_k = 3(Z/3^k Z) × 3(Z/3^k Z × Z/3^k Z) is the Jacobson radical.

modulus dim(O_k / 3 O_k) dim(O_k / J_k) dim(J_k / 3 O_k) dims of J_k^r / J_k^{r+1} dims of 3^r O_k / 3^{r+1} O_k
27 3 2 1 [3, 3] [3, 3]
81 3 2 1 [3, 3, 3] [3, 3, 3]
243 3 2 1 [3, 3, 3, 3] [3, 3, 3, 3]
729 3 2 1 [3, 3, 3, 3, 3] [3, 3, 3, 3, 3]

Read

Three distinct structures coexist:

Two distinct filtrations must be separated:

So the correct arithmetic picture is: