PowermapsAllowedBySymmetrisations( tbl, subchars, chars, pow,
prime, parameters )
More about Maps and Parametrized Maps) maps map which are contained in the parametrized map
pow and which have the property that for all chi in the list chars of
characters of the character table tbl, the symmetrizations
[ chi^p- = M
inusCharacter(
chi, map, prime )
]
(see MinusCharacter) have nonnegative integral scalar products with all
characters in the list subchars.
parameters must be a record with fields
maxlen
:
contained
:contained( tbl, subchars, minus )
minamb
, maxamb
:minamb < Indeterminateness( minus ) < maxamb
]
quick
:pow will be improved, i.e. is changed by the algorithm.
If there is no character left which allows an immediate improvement but there
are characters in chars with indeterminateness of the symmetrizations bigger
than parameters.minamb
, a branch is necessary. Two kinds of branches may
occur: If parameters.contained( tbl, subchars, minus )
has
length at most parameters.maxlen
, the union of maps allowed by the
characters in minus is computed; otherwise a suitable class c
is taken
which is significant for some character, and the union of all admissible maps
with image x
on c
is computed, where x
runs over pow[c]
.
# see example in "ConsiderKernels" gap> t := CharTable( "U4(3).4" );; gap> PowermapsAllowedBySymmetrisations(t,t.irreducibles,t.irreducibles, > pow, 2, rec( maxlen:=10, contained:=ContainedPossibleCharacters, > minamb:= 2, maxamb:= "infinity", quick:= false ) ); [ [ 1, 1, 3, 4, 5, 2, 2, 8, 3, 4, 11, 12, 6, 14, 9, 1, 1, 2, 2, 3, 4, 5, 6, 8, 9, 9, 10, 11, 12, 16, 16, 16, 16, 17, 17, 18, 18, 18, 18, 20, 20, 20, 20, 22, 22, 24, 24, 25, 26, 28, 28, 29, 29 ] ] gap> t.powermap[2] = last[1]; true
GAP 3.4.4