LEVEL 43
GRITSENKO LIFTS
Number of wt 2 Gritsenko lifts: 1
Number of wt 4 Gritsenko lifts: 8
WEIGHT 4 CUSP FORMS
The weight 4 space of cusp forms (and the plus and minus parts) have dimensions:
dim S4(K(43)) = 9
dim S4(K(43))+ = 9
dim S4(K(43))- = 0
Here, there is one wt 2 Gritsenko lift and 8
wt 4 Gritsenkow lifts.
Because the square of the wt 2 Gritsenko lift is necessarily linearly independent
of the wt 4 Gritsenko lifts, then
the square of the wt 2 Gritsenko lift along with the wt 4 Gritsenko lifts
must span the the 9-dimesnional wt 4 cusp forms,
implying that all the wt 4 cusp forms are plus forms.
PROVING UPPER BOUND ON NUMBER OF WEIGHT 2 NONLIFTS
We claim:
At most number of wt 2 plus nonlifts: 0
At most number of wt 2 minus nonlifts: 0
We use the theorem that if
there is only one wt 2 Gritsenko lift and if
dim S4(K(43)) equals 1 plus the number of wt 4 Gritsenko lifts,
then we have that
dim H(2)''+ = 0
which implies that there are no plus wt 2 nonlifts.
Because S4(K(43))-=0 and there is at least one
wt 2 Gritsenko lift, then
there cannot be any wt 2 minus form,
and in particular no wt 2 minus nonlift.