GROUP OF ORDER 16 # 13
GROUP OF ORDER 16 # 13
Semidihedral(16)
The MAGMA library number for G is 8
GrpPC : G of order 16 = 2^4
PC-Relations:
G.2^2 = G.3,
G.3^2 = G.4,
G.2^G.1 = G.2 * G.3,
G.3^G.1 = G.3 * G.4
The center of G is abelian of type [ 2 ]
The orders of the terms of the lower central series are [ 16, 4, 2, 1 ]
The orders of the terms of the upper central series are [ 1, 2, 4, 16 ]
The order of the Frattini subgroup is 4
The exponent of G is 8
G has one conjugate class of maximal elementary abelian subgroups. Any
element of the class has order 4 . Its centralizer
has order 4 and its normalizer has order 8
The cohomology ring of G is the quotient of a polynomial
ring in the variables [
z,
y,
x,
w
]
in degrees [ 1, 1, 3, 4 ]
by the ideal generated by the relations
[
z*y + y^2,
y^3,
y*x,
z^3*x + z^2*w + y^2*w + x^2
]
The Hilbert series for the cohomology ring is 1/(t^4 - 2*t^3 + 2*t^2 - 2*t + 1)
Its denominator factors as
( t - 1
)^2
( t^2 + 1
)^1
The Krull dimension of the cohomology ring is 2
The longest regular sequence consists of the generators [
w
]
A homogeneous set of parameters is the set [
w,
z^2
]
of degrees [ 4, 2 ]
The hypercohomolgy spectral sequence has E2 term:
ROW (0)
[
z,
y
]
[
y^2
]
[
x
]
[
z*x
]
ROW (1)
[
y
]
[
y^2
]
The spectral sequence satisfies Poincaré duality
Restriction to the Maximal Elementary Abelian Subgroup
Generated by [ G.4, G.1 ]
The cohomology ring of E is a polynomial ring in the variables [
z,
y
]
The images of the generators of the cohomology of G
restricted to E are
[
z,
0,
z^2*y + z*y^2,
z^3*y + y^4
]
in the cohomology of E
The kernel of the restriction to E (Minimal Prime) of the
cohomology of G is generated by
[
y
]
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 [ 8 ]
The cohomology ring of H is a the quotient of a polynomial ring
in the variables [
z,
y
]
in degrees [ 1, 2 ]
by the ideal of relations
[
z^2
]
The images of the generators of the cohomology of G
restricted to H are
[
0,
z,
z*y,
y^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 Isomorphic to the
Group of Order 8 Number 5
GrpPC of order 8 = 2^3
PC-Relations:
$.1^2 = $.3,
$.2^2 = $.3,
$.2^$.1 = $.2 * $.3
Generated by [ G.3, G.1 * G.2 * G.3 ]
of type Quaternion(8)
The images of the generators of the cohomology of G
restricted to H are
[
y,
y,
z*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 Isomorphic to the
Group of Order 8 Number 4
GrpPC of order 8 = 2^3
PC-Relations:
$.2^2 = $.3,
$.2^$.1 = $.2 * $.3
Generated by [ G.3, G.1 ]
of type Dihedral(8)
The images of the generators of the cohomology of G
restricted to H are
[
z,
0,
z*x,
z^2*x + x^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