/usr/share/gap/pkg/ctbllib/doc/construc.tex is in gap-character-tables 1r1p3-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 | % This file was created automatically from construc.msk.
% DO NOT EDIT!
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%W construc.msk GAP 4 package `ctbllib' Thomas Breuer
%%
%H @(#)$Id: construc.msk,v 1.6 2004/03/12 09:41:42 gap Exp $
%%
%Y Copyright (C) 2002, Lehrstuhl D fuer Mathematik, RWTH Aachen, Germany
%%
\Chapter{Functions for Character Table Constructions}
The functions in this chapter deal with the construction of character
tables from other character tables. So they fit to the functions in
Section~"ref:Constructing Character Tables from Others" in the {\GAP}
Reference Manual.
But since they are used in situations that are typical for the {\GAP}
Character Table Library, they are described here.
An important ingredient of the constructions is the description of the
action of a group automorphism on the classes by a permutation.
In practice, these permutations are usually chosen from the group of
table automorphisms of the character table in question
(see~"ref:AutomorphismsOfTable" in the {\GAP} Reference Manual).
Section~"Character Tables of Groups of Structure MGA" deals with
groups of structure $M\.G\.A$, where the upwards extension $G\.A$ acts
suitably on the central extension $M\.G$.
Section~"Character Tables of Groups of Structure GS3" deals with
groups that have a factor group of type $S_3$.
Section~"Character Tables of Coprime Central Extensions" deals with
special cases of the construction of character tables of central
extensions from known character tables of suitable factor groups.
Section~"Construction Functions used in the Character Table Library"
documents the functions used to encode certain tables in the {\GAP}
Character Table Library.
Examples can be found in~\cite{Auto}.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\Section{Attributes for Character Table Constructions}
\>ConstructionInfoCharacterTable( <tbl> ) A
If this attribute is set for an ordinary character table <tbl> then
the value is a list that describes how this table was constructed.
The first entry is a string that is the identifier of the function that
was applied to the pre-table record; the remaining entries are the
arguments for that functions, except that the pre-table record must be
prepended to these arguments.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\Section{Character Tables of Groups of Structure MGA}
\>PossibleCharacterTablesOfTypeMGA( <tblMG>, <tblG>, <tblGA>, <aut>, %
<identifier> ) F
Let $H$ be a group with normal subgroups $N$ and $M$ such that
$H/N$ is cyclic, $M \leq N$ holds,
and such that each irreducible character of $N$
that does not contain $M$ in its kernel induces irreducibly to $H$.
(This is satisfied for example if $N$ has prime index in $H$
and $M$ is a group of prime order that is central in $N$ but not in $H$.)
Let $G = N/M$ and $A = H/N$, so $H$ has the structure $M\.G\.A$.
Let <tblMG>, <tblG>, <tblGA> be the ordinary character tables of the
groups $M\.G$, $G$, and $G\.A$, respectively,
and <aut> the permutation of classes of <tblMG> induced by the action
of $H$ on $M\.G$.
Furthermore, let the class fusions from <tblMG> to <tblG> and from <tblG>
to <tblGA> be stored on <tblMG> and <tblG>, respectively
(see~"ref:StoreFusion" in the {\GAP} Reference Manual).
`PossibleCharacterTablesOfTypeMGA' returns a list of records describing
all possible character tables for groups $H$ that are compatible with the
arguments.
Note that in general there may be several possible groups $H$,
and it may also be that ``character tables'' are constructed for which no
group exists.
Each of the records in the result has the following components.
\beginitems
`table' &
the ordinary character table of a possible table for $H$, and
`MGfusMGA' &
the fusion map from <tblMG> into the table stored in `table'.
\enditems
The possible tables differ w.r.t. some power maps, and perhaps element
orders and table automorphisms;
in particular, the `MGfusMGA' component is the same in all records.
The returned tables have the `Identifier' value <identifier>.
The classes of these tables are sorted as follows.
First come the classes contained in $M\.G$, sorted compatibly with the
classes in <tblMG>, then the classes in $H \setminus M\.G$ follow,
in the same ordering as the classes of $G\.A \setminus G$.
\>PossibleActionsForTypeMGA( <tblMG>, <tblG>, <tblGA> ) F
Let the arguments be as described for `PossibleCharacterTablesOfTypeMGA'
(see~"PossibleCharacterTablesOfTypeMGA").
`PossibleActionsForTypeMGA' returns the set of those table automorphisms
(see~"ref:AutomorphismsOfTable" in the {\GAP} Reference Manual)
of <tblMG> that can be induced by the action of $H$ on $M\.G$.
Information about the progress is reported if the info level of
`InfoCharacterTable' is at least $1$
(see~"ref:SetInfoLevel" in the {\GAP} Reference Manual).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\Section{Character Tables of Groups of Structure GS3}
\>CharacterTableOfTypeGS3( <tbl>, <tbl2>, <tbl3>, <aut>, <identifier> ) F
\>CharacterTableOfTypeGS3( <modtbl>, <modtbl2>, <modtbl3>, <ordtbls3>, %
<identifier> ) F
Let $H$ be a group with a normal subgroup $G$ such that $H/G \cong S_3$,
the symmetric group on three points,
and let $G\.2$ and $G\.3$ be preimages of subgroups of order $2$ and $3$,
respectively, under the natural projection onto this factor group.
In the first form, let <tbl>, <tbl2>, <tbl3> be the ordinary character
tables of the groups $G$, $G\.2$, and $G\.3$, respectively,
and <aut> the permutation of classes of <tbl3> induced by the action
of $H$ on $G\.3$.
Furthermore assume that the class fusions from <tbl> to <tbl2> and <tbl3>
are stored on <tbl>
(see~"ref:StoreFusion" in the {\GAP} Reference Manual).
In the second form, let <modtbl>, <modtbl2>, <modtbl3> be the $p$-modular
character tables of the groups $G$, $G\.2$, and $G\.3$, respectively,
and <ordtbls3> the ordinary character table of $H$.
`CharacterTableOfTypeGS3' returns a record with the following components.
\beginitems
`table' &
the ordinary or $p$-modular character table of $H$, respectively,
`tbl2fustbls3' &
the fusion map from <tbl2> into the table of $H$, and
`tbl3fustbls3' &
the fusion map from <tbl3> into the table of $H$.
\enditems
The returned table of $H$ has the `Identifier' value <identifier>.
The classes of the table of $H$ are sorted as follows.
First come the classes contained in $G\.3$, sorted compatibly with the
classes in <tbl3>, then the classes in $H \setminus G\.3$ follow,
in the same ordering as the classes of $G\.2 \setminus G$.
\>PossibleActionsForTypeGS3( <tbl>, <tbl2>, <tbl3> ) F
Let the arguments be as described for `CharacterTableOfTypeGS3'
(see~"CharacterTableOfTypeGS3").
`PossibleActionsForTypeGS3' returns the set of those table automorphisms
(see~"ref:AutomorphismsOfTable" in the {\GAP} Reference Manual)
of <tbl3> that can be induced by the action of $H$ on the classes of
<tbl3>.
Information about the progress is reported if the info level of
`InfoCharacterTable' is at least $1$
(see~"ref:InfoCharacterTable" in the {\GAP} Reference Manual).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Section{Character Tables of Groups of Structure GV4}
%FileHeader[4]{construc}
%Declaration{PossibleCharacterTablesOfTypeGV4}
%Declaration{PossibleActionsForTypeGV4}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Section{Character Tables of Groups of Structure V4G}
%FileHeader[5]{construc}
%Declaration{PossibleCharacterTablesOfTypeV4G}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Section{Brauer Tables of Extensions by p-regular Automorphisms}
%FileHeader[6]{construc}
%Declaration{BrauerTableOfExtensionBySingularAutomorphism}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\Section{Character Tables of Coprime Central Extensions}
\>CharacterTableOfCommonCentralExtension( <tblG>, <tblmG>, <tblnG>, <id> ) F
Let <tblG> be the ordinary character table of a group $G$, say,
and let <tblmG> and <tblnG> be the ordinary character tables of central
extensions $m.G$ and $n.G$ of $G$ by cyclic groups of prime orders $m$
and $n$, respectively, with $m \not= n$.
We assume that the factor fusions from <tblmG> and <tblnG> to <tblG> are
stored on the tables.
`CharacterTableOfCommonCentralExtension' returns a record with the
following components.
\beginitems
`tblmnG' &
the character table $t$, say, of the corresponding central extension
of $G$ by a cyclic group of order $m n$ that factors through $m.G$
and $n.G$; the `Identifier' value of this table is <id>,
`IsComplete' &
`true' if the `Irr' value is stored in $t$, and `false' otherwise,
`irreducibles' &
the list of irreducibles of $t$ that are known;
it contains the inflated characters of the factor groups $m.G$ and
$n.G$, plus those irreducibles that were found in tensor
products of characters of these groups.
\enditems
Note that the conjugacy classes and the power maps of $t$ are uniquely
determined by the input data.
Concerning the irreducible characters, we try to extract them from the
tensor products of characters of the given factor groups by reducing
with known irreducibles and applying the LLL algorithm
(see~"ref:ReducedClassFunctions" and~"ref:LLL"
in the {\GAP} Reference Manual).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\Section{Construction Functions used in the Character Table Library}
The following functions are used in the {\GAP} Character Table Library,
for encoding table constructions via the mechanism that is based on the
attribute `ConstructionInfoCharacterTable'
(see~"ConstructionInfoCharacterTable").
All construction functions take as their first argument a record that
describes the table to be constructed, and the function adds only those
components that are not yet contained in this record.
\>ConstructMGA( <tbl>, <subname>, <factname>, <plan>, <perm> ) F
`ConstructMGA' constructs the ordinary character table <tbl> of a group
$m\.G\.a$ where the automorphism $a$ (a group of prime order) of $m\.G$
acts notrivially on the central subgroup $m$ of $m\.G$.
<subname> is the name of the subgroup $m\.G$ which is a (not necessarily
cyclic) central extension of the (not necessarily simple) group $G$,
<factname> is the name of the factor group $G\.a$.
Then the faithful characters of <tbl> are induced characters of $m\.G$.
<plan> is a list, each entry being a list containing positions of
characters of $m\.G$ that form an orbit under the action of $a$
(so the induction of characters is simulated).
<perm> is the permutation that must be applied to the list of characters
that is obtained on appending the faithful characters to the
inflated characters of the factor group.
A nonidentity permutation occurs for example for groups of structure
$12\.G\.2$ that are encoded via the subgroup $12\.G$ and the factor group
$6\.G\.2$, where the faithful characters of $4\.G\.2$ shall precede those
of $6\.G\.2$.
Examples where `ConstructMGA' is used to encode library tables are the
tables of $3\.F_{3+}\.2$ (subgroup $3\.F_{3+}$, factor group $F_{3+}\.2$)
and $12_1\.U_4(3)\.2_2$ (subgroup $12_1\.U_4(3)$, factor group
$6_1\.U_4(3)\.2_2$).
\>ConstructMGAInfo( <tblmGa>, <tblmG>, <tblGa> ) F
Let <tblmGa> be the ordinary character table of a group of structure
$m\.G\.a$ where the factor group of prime order $a$ acts nontrivially on
the normal subgroup of order $m$ that is central in $m\.G$,
<tblmG> the character table of $m\.G$, and <tblGa> the character table of
the factor group $G\.a$.
`ConstructMGAInfo' returns the list that is to be stored in the library
version of <tblmGa>: the first entry is the string `"ConstructMGA"',
the remaining four entries are the last four arguments for the call to
`ConstructMGA' (see~"ConstructMGA").
\>ConstructGS3( <tbls3>, <tbl2>, <tbl3>, <ind2>, <ind3>, <ext>, <perm> ) F
\>ConstructGS3Info( <tbl2>, <tbl3>, <tbls3> ) F
`ConstructGS3' constructs the irreducibles of an ordinary character table
<tbls3> of type $G\.S_3$ from the tables with names <tbl2> and <tbl3>,
which correspond to the groups $G\.2$ and $G\.3$, respectively.
<ind2> is a list of numbers referring to irreducibles of <tbl2>.
<ind3> is a list of pairs, each referring to irreducibles of <tbl3>.
<ext> is a list of pairs, each referring to one irreducible of <tbl2>
and one of <tbl3>.
<perm> is a permutation that must be applied to the irreducibles
after the construction.
`ConstructGS3Info' returns a record with the components `ind2', `ind3',
`ext', `perm', and `list', as are needed for `ConstructGS3'.
\>ConstructV4G( <tbl>, <facttbl>, <aut>[, <ker>] ) F
Let <tbl> be the character table of a group of type $2^2\.G$
where an outer automorphism of order 3 permutes the three involutions
in the central $2^2$.
Let <aut> be the permutation of classes of <tbl> induced by that
automorphism, and <facttbl> the name of the character table
of the factor group $2\.G$.
Then `ConstructV4G' constructs the irreducible characters of <tbl> from
that information.
The optional argument <ker> is an integer denoting the position of the
nontrivial class of the table of $2\.G$ that lies in the kernel of the
epimorphism onto $G$; the default for <ker> is $2$.
\>ConstructProj( <tbl>, <irrinfo> ) F
\>ConstructProjInfo( <tbl>, <kernel> ) F
`ConstructProj' constructs the irreducible characters of record encoding
the ordinary character table <tbl> from projective characters of tables
of factor groups,
which are stored in the `ProjectivesInfo' (see~"ProjectivesInfo") value
of the smallest factor;
the information about the name of this factor and the projectives to
take is stored in <irrinfo>.
`ConstructProjInfo' takes an ordinary character table <tbl> and a list
<kernel> of class positions of a cyclic kernel of order dividing $12$,
and returns a record with the components
\beginitems
`tbl' &
a character table that is permutation isomorphic with <tbl>,
and sorted such that classes that differ only by multiplication with
elements in the classes of <kernel> are consecutive,
`projectives' &
a record being the entry for the `projectives' list of the table of
the factor of <tbl> by <kernel>,
describing this part of the irreducibles of <tbl>, and
`info' &
the value of <irrinfo>.
\enditems
In order to encode a library table $t$ as a ``projective table'' relative
to another library table $f$, say, one has to do the following.
First the factor fusion from $t$ to $f$ must be stored on the table of
$t$, and $t$ is written to a library file.
Then the result of `ConstructProjInfo', called for $t$ and the kernel of
the factor fusion, is used as follows.
The list containing `"ConstructProj"' at its first position and the
`info' component is added as last entry of the `MOT' call for this
library version.
The `projectives' component is added to the `ProjectivesInfo' list of
$f$, and a new library version of $f$ is produced (this contains the new
projectives via an `ARC' call).
Finally, `etc/maketbl' is called in order to store the projection for the
factor fusion in the `ctprimar.tbl' data.
\>ConstructDirectProduct( <tbl>, <factors> ) F
\>ConstructDirectProduct( <tbl>, <factors>, <permclasses>, <permchars> ) F
is a special case of a `construction' call for a library table <tbl>.
The direct product of the tables described in the list <factors> is
constructed, and all its components stored not yet in <tbl> are
added to <tbl>.
The `computedClassFusions' component of <tbl> is enlarged
by the factor fusions from the direct product to the factors.
If the optional arguments <permclasses>, <permchars> are given then
classes and characters of the result are sorted accordingly.
<factors> must have length at least two;
use `ConstructPermuted' (see~"ConstructPermuted") in the case of only
one factor.
\>ConstructSubdirect( <tbl>, <factors>, <choice> ) F
The library table <tbl> is completed with help of the table obtained by
taking the direct product of the tables with names in the list <factors>,
and then taking the table consisting of the classes in the list <choice>.
Note that in general, the restriction to the classes of a normal subgroup
is not sufficient for describing the irreducible characters of this
normal subgroup.
\>ConstructIsoclinic( <tbl>, <factors> ) F
\>ConstructIsoclinic( <tbl>, <factors>, <nsg> ) F
constructs first the direct product of library tables as given by the
list <factors>, and then constructs the isoclinic table of the result.
\>ConstructPermuted( <tbl>, <libnam>[, <prmclasses>, <prmchars>] ) F
The library table <tbl> is completed with help of the library table with
name <libnam>, whose classes and characters must be permuted by the
permutations <prmclasses> and <prmchars>, respectively.
\>ConstructFactor( <tbl>, <libnam>, <kernel> ) F
The library table <tbl> is completed with help of the library table with
name <libnam>, by factoring out the classes in the list <kernel>.
%Declaration{ConstructClifford}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Section{Miscellaneous}
%FileHeader[8]{construc}
%Declaration{PossibleActionsForTypeGA}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%
%E
|