Use pow_pos(norm(...),3)
instead of pow_abs(norm(...),3)
for norm(...)^3
.
1/norm(v)
is neither convex nor concave. For instance, if v1) = v(2) = 1, its Hessian has one positive and one negative eigenvalue.
The log term is going to switch between convex and concave depending on the value of q^2.