Gives the most precise available description of the p-Frattini module for any
p-perfect finite group G=G0 (Thm. 2.8), and therefore of the groups G_{k,ab}, k
\ge 0, from which we form the abelianized M(odular) T(ower). \S 4 includes a
classification of Schur multiplier quotients, from which we figure two points
(see the html file this http URL):
1. Whether there is a non-empty MT over a given Hurwitz space component at
level 0; and
2. whether all cusps above a given level 0 o-p' cusp are p-cusps.
The "relating" entwines three problems:
1. Davenport's Problem, describing pairs of polynomials over Q whose ranges
on Z/p are the same for almost all p.
2. Showing that the monodromy groups of rational function maps over the
complexes are limited to a finite set of groups, outside of groups close to
alternating groups (example, symmetric groups) with special representations,
and dihedral and cyclic groups.
A cover of normal varieties is exceptional over a finite field if the map on
points over infinitely many extensions of the field is one-one. A cover over a
number field is exceptional if it is exceptional over infinitely many residue
class fields. The first result: The category of exceptional covers of a normal
variety, Z, over a finite field, F_q, has fiber products, and therefore a
natural Galois group (with permutation representation) limit. This has many
applications to considering Poincare series attached to diophantine questions.
The paper follows three lines:
A cover of normal varieties is exceptional over a finite field if the map on
points over infinitely many extensions of the field is one-one. A cover over a
number field is exceptional if it is exceptional over infinitely many residue
class fields. The first result: The category of exceptional covers of a normal
variety, Z, over a finite field, F_q, has fiber products, and therefore a
natural Galois group (with permutation representation) limit. This has many
applications to considering Poincare series attached to diophantine questions.
The paper follows three lines: