S2(K(389))+
Proving the existence of a nonlift.
-
A nonlift Borcherds product Borch(ψ) in S2(K(389))+ can
be proven by constructing (the same) ψ explicitly in the following ways.
- Define ψ here
as a weight 12 cusp form divided by Δ
- Define ψ here as (-φ|V2)/φ + c Θ/φ,
where Θ is an inflation of φ
- The nonlift eigenform f in S2(K(389))+ has a formula as a linear combination of the above Borcherds product
and Gritsenko lifts. See
here
for the formula.