GROUP OF ORDER 16 # 9
GROUP OF ORDER 16 # 9
The MAGMA library number for G is 3
GrpPC : G of order 16 = 2^4
PC-Relations:
G.1^2 = G.3,
G.2^G.1 = G.2 * G.4
The center of G is abelian of type [ 2, 2 ]
The orders of the terms of the lower central series are [ 16, 2, 1 ]
The orders of the terms of the upper central series are [ 1, 4, 16 ]
The order of the Frattini subgroup is 4
The exponent of G is 4
G has a unique maximal elementary abelian subgroup which is normal and
has order 8. Its centralizer has order 8
The cohomology ring of G is the quotient of a polynomial
ring in the variables [
z,
y,
x,
w,
v
]
in degrees [ 1, 1, 2, 2, 2 ]
by the ideal generated by the relations
[
z^2,
z*y,
z*x,
y^2*w + x^2
]
The Hilbert series for the cohomology ring is -1/(t^4 - 2*t^3 + 2*t - 1)
Its denominator factors as
( t - 1
)^3
( t + 1
)^1
The Krull dimension of the cohomology ring is 3
The longest regular sequence consists of the generators [
w,
v
]
A homogeneous set of parameters is the set [
w,
v,
y^2
]
of degrees [ 2, 2, 2 ]
The hypercohomolgy spectral sequence has E2 term:
ROW (0)
[
y,
z
]
[
x
]
[
y*x
]
ROW (1)
[
z
]
The spectral sequence satisfies Poincaré duality
Restriction to the Maximal Elementary Abelian Subgroup
Generated by [ G.2 * G.3 * G.4, G.4, G.3 * G.4 ]
The cohomology ring of E is a polynomial ring in the variables [
z,
y,
x
]
The images of the generators of the cohomology of G
restricted to E are
[
0,
z,
z^2 + z*y,
z^2 + y^2,
z*y + y^2 + z*x + x^2
]
in the cohomology of E
The kernel of the restriction to E (Minimal Prime) of the
cohomology of G is generated by
[
z
]
This ideal is also the nilradical of the cohomology of G.
Restrictions to Maximal Subgroups
Maximal Subgroup H # 1
The group H is abelian of type [ 2, 2, 2 ]
The cohomology ring of H is a polynomial ring with variables [
z,
y,
x
]
in degrees [ 1, 1, 1 ]
The images of the generators of the cohomology of G
restricted to H are
[
0,
z,
z*y,
y^2,
z*x + x^2
]
in the cohomology of H
The kernel of the restriction to H of the cohomology of G
is generated by
[
z
]
Maximal Subgroup H # 2
The group H is abelian of type [ 4, 2 ]
The cohomology ring of H is a the quotient of a polynomial ring
in the variables [
z,
y,
x
]
in degrees [ 1, 1, 2 ]
by the ideal of relations
[
z^2
]
The images of the generators of the cohomology of G
restricted to H are
[
z,
z,
z*y,
x,
y^2 + x
]
in the cohomology of H
The kernel of the restriction to H of the cohomology of G
is generated by
[
z + y
]
Maximal Subgroup H # 3
The group H is abelian of type [ 4, 2 ]
The cohomology ring of H is a the quotient of a polynomial ring
in the variables [
z,
y,
x
]
in degrees [ 1, 1, 2 ]
by the ideal of relations
[
z^2
]
The images of the generators of the cohomology of G
restricted to H are
[
z,
0,
z*y,
x,
z*y + y^2
]
in the cohomology of H
The kernel of the restriction to H of the cohomology of G
is generated by
[
y
]
The essential cohomology of G is zero
CHECKS
paramflag = true
qregflagflag = true
cmflag = false
essflag = true
centflag = true
THE COMPUTATION IS COMPLETE