labellib Libraries of small loops form an integral part of LOOPS. Loops in libraries are stored up to isomorphism or up to isotopism. The name of a library up to isotopism starts with itp.
A library named my Library is stored in file data/mylibrary.tbl
, and the
corresponding data structure is named my_library_data
.
In most cases, the array my_library_data
consists of three lists
my_library_data[ 1 ]
is a list of orders for which there is at
least one loop in the library,
my_library_data[ 2 ][ k ]
is the number of loops of order
my_library_data[ 1 ][ k ]
in the library,
my_library_data[ 3 ][ s ]
contains data necessary to produce the
sth loop in the library.
my_library_data[ 3 ]
depends on the particular library and is
not standardized in any way.
The user can retrieve the mth loop of order n from library named my Library according to the template
MyLibraryLoop(
n,
m ) F
It is also possible to obtain the same loop with
LibraryLoop(
name,
n,
m ) F
where name is the name of the library.
For example, when the library is called left Bol, the corresponding data file
is called data/leftbol.tbl
, the corresponding data structure is named
left_bol_data
, and the mth left Bol loop of order n is obtained via
LeftBolLoop(
n,
m )
or via
LibraryLoop("left Bol",
n,
m )
We are now going to describe the individual libraries in detail. A brief information about the library named name can also be obtained in LOOPS with
DisplayLibraryInfo(
name ) F
The library named left Bol contains all nonassociative left Bol loops of order less than 17, including Moufang loops. There are 6 such loops of order 8, 1 of order 12, 2 of order 15, and 2038 of order 16. (The classification of left Bol loops of order 16 was first accomplished by Moorhouse Mo. Our library was generated independently, and agrees with Moorhouse's results.)
Following the general pattern, the mth nonassociative left Bol loop of order n is obtained by
LeftBolLoop(
n,
m ) F
The library named Moufang contains all nonassociative Moufang loops of order n £ 64 and n=81.
The mth nonassociative Moufang loop of order n is obtained by
MoufangLoop(
n,
m ) F
For n £ 63, our catalog numbers coincide with those of Goodaire et al. Go. The classification of Moufang loops of order 64 and 81 was carried out in NaVo2007.
The extent of the library is summarized below:
|
The octonion loop
multiplication loop of the ± basis elements in the 8-dimensional standard
real octonion algebra) is MoufangLoop( 16, 3 )
.
The library named code contains all nonassociative code loops of order less than 65. There are 5 such loops of order 16, 16 of order 32, and 80 of order 64, all Moufang. The library merely points to the corresponding Moufang loops. See NaVo2007 for a classification of small code loops.
The mth nonassociative code loop of order n is obtained by
CodeLoop(
n,
m ) F
Here is how the libary Steiner is described within LOOPS:
gap> DisplayLibraryInfo( "Steiner" ); The library contains all nonassociative Steiner loops of order less or equal to 16. It also contains the associative Steiner loops of order 4 and 8. ------ Extent of the library: 1 loop of order 4 1 loop of order 8 1 loop of order 10 2 loops of order 14 80 loops of order 16 true
The mth Steiner loop of order n is obtained by
SteinerLoop(
n,
m ) F
Our catalog numbers coincide with those of Colbourn and Rosa CoRo.
By results of Kunen Ku, for every odd prime p there are precisely 3 nonassociative conjugacy closed loopsindexconjugacy closed loop of order p2. Csörgö and Drápal CsDr described these 3 loops by multiplicative formulas on Zp2 and Zp ×Zp.
Case m = 1: Let k be the smallest positive integer relatively prime to p and such that k is a square modulo p (i.e., k=1). Define multiplication on Zp2 by x·y = x + y + kpx2y.
Case m = 2: Let k be the smallest positive integer relatively prime to p and such that k is not a square modulo p. Define multiplication on Zp2 by x·y = x + y + kpx2y.
Case m = 3: Define multiplication on Zp ×Zp by (x,a)(y,b) = (x+y, a+b+x2y ).
Moreover, Wilson Wi constructed a nonassociative CC-loop of order 2p for every odd prime p, and Kunen Ku showed that there are no other nonassociative CC-loops of this order. Here is the construction:
Let N be an additive cyclic group of order n > 2, N = á1ñ.
Let G be the additive cyclic group of order 2. Define multiplication on
L = G ×N as follows:
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The CC-loops described above can be obtained by
CCLoop(
n,
m ) F
The library named small contains all nonassociative loops of order 5 and 6. There are 5 and 107 such loops, respectively. The loops are obtained by
SmallLoop(
n,
m ) F
Paige loopsindexPaige loop are nonassociative finite simple Moufang loops. By Li, there is precisely one Paige loop for every finite field GF(q).
The library named Paige contains the smallest nonassociative simple Moufang loop
PaigeLoop(
2 ) F
The library named interesting contains some loops that are illustrative for the theory of loops. At this point, the library contains a nonassociative loop of order 5, a nonassociative nilpotent loop of order 6, a nonMoufang left Bol loop of order 16, and the loop of sedenionsindexsedenions of order 32 (sedenions generalize octonions).
The loops are obtained with
InterestingLoop(
n,
m ) F
For the library small we also provide the corresponding library of loops up to isotopism.
In general, given a library named lib, the corresponding library up to
isotopism is named itp lib, and the loops can be retrieved by the template
function ItpLibLoop( n, m )
. Thus we have
ItpSmallLoop( n, m ) O
Here is an example:
gap> SmallLoop( 6, 14 ); <small loop 6/14> gap> ItpSmallLoop( 6, 14 ); <small loop 6/42> gap> LibraryLoop( "itp small", 6, 14 ); <small loop 6/42>
Note that loops up to isotopism form a subset of the corresponding library of loops up to isomorphism. For instance, the above example shows that the 14th small loop of order 6 up to isotopism is in fact the 42nd small loop of order 6 up to isomorphism.
Here is the list of all supported libraries up to isotopism and their extent, as displayed by LOOPS:
gap> DisplayLibraryInfo("itp small"); The library contains all nonassociative loops of order less than 7 up to isotopism. ------ Extent of the library: 1 loop of order 5 20 loops of order 6
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