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<strong>LitNet</strong> Akademies Jaargang 9 (2), April 2012<br />

Enumerasie van self-ortonogale Latynse vierkan<strong>te</strong><br />

met simmetriese ortogonale maats<br />

A.P. Burger, M.P. Kidd en J.H. van Vuuren<br />

A.P. Burger, M.P. Kidd en J.H. van Vuuren: Depar<strong>te</strong>ment Logistiek, Universi<strong>te</strong>it S<strong>te</strong>llenbosch<br />

Ops<strong>om</strong>m<strong>in</strong>g<br />

In <strong>hier</strong><strong>die</strong> artikel enumereer ons verskeie ekwivalensieklasse van self-ortogonale Latynse vierkan<strong>te</strong><br />

met simmetriese, ortogonale maats (SOLVSOMs), ’n probleem wat nog nie <strong>in</strong> <strong>die</strong> li<strong>te</strong>ratuur<br />

oor k<strong>om</strong>b<strong>in</strong>atoriese ontwerpe aangespreek is nie. In <strong>die</strong> besonder bepaal ons <strong>die</strong> getal<br />

(ry, kol<strong>om</strong>)-paratoopklasse van SOLVSOMs van orde n 10 deur <strong>in</strong>ligt<strong>in</strong>g <strong>in</strong> bestaande, uitput<strong>te</strong>nde<br />

databasisse van self-ortogonale Latynse vierkan<strong>te</strong> en simmetriese Latynse vierkan<strong>te</strong><br />

met behulp van ’n bo<strong>om</strong>soektog met <strong>te</strong>rugker<strong>in</strong>g (Eng: backtrack<strong>in</strong>g) <strong>te</strong> k<strong>om</strong>b<strong>in</strong>eer. Ons bepaal<br />

ook <strong>die</strong> getal verskillende SOLVSOMs, SOLVSOMs <strong>in</strong> standaardvorm en transponentis<strong>om</strong>orfismeklasse<br />

van SOLVSOMs van ordes n 10 deur gebruikmak<strong>in</strong>g van standaard <strong>te</strong>gnieke<br />

uit abstrak<strong>te</strong> algebra. In <strong>die</strong> proses beantwoord ons ’n 34 jaar-oue oop bestaansvraag<br />

oor SOLVSOMs van orde 10 deur aan <strong>te</strong> toon dat geen so ’n ontwerp bestaan nie. Aangesien<br />

’n SOLVSOM van orde n <strong>in</strong> standaardvorm ekwivalent is aan ’n spelskedule vir ’n gadevermydende<br />

gemengde-dubbels rond<strong>om</strong>talie-<strong>te</strong>nnistoernooi vir n getroude pare, dui <strong>hier</strong><strong>die</strong><br />

resultaat daarop dat geen so ’n toernooi vir 10 getroude pare geskeduleer kan word nie.<br />

Trefwoorde: Latynse vierkant, self-ortogonale Latynse vierkant, simmetriese Latynse vierkant,<br />

SOLVSOM, enumerasie.<br />

Abstract<br />

Enumeration of self-orthogonal Lat<strong>in</strong> squares with symmetric orthogonal ma<strong>te</strong>s<br />

A Lat<strong>in</strong> square of order n is an n × n array conta<strong>in</strong><strong>in</strong>g each symbol fr<strong>om</strong> a set of n dist<strong>in</strong>ct<br />

symbols exactly once <strong>in</strong> every row and every column. We deno<strong>te</strong> the entry <strong>in</strong> row i and column<br />

j of a Lat<strong>in</strong> square L by L(i, j) and take the n symbols fr<strong>om</strong> the set Zn = {0,...,n − 1}. The<br />

<strong>in</strong>dex sets for the rows and columns of a Lat<strong>in</strong> square are also taken as Zn. A Lat<strong>in</strong> square<br />

is said to be unipo<strong>te</strong>nt if all the entries on its ma<strong>in</strong> diagonal are a s<strong>in</strong>gle symbol fr<strong>om</strong> Zn,<br />

idempo<strong>te</strong>nt if the entries on its ma<strong>in</strong> diagonal are all the symbols of Zn <strong>in</strong> natural order, and<br />

reduced if both its first row and first column conta<strong>in</strong> the symbols of Zn <strong>in</strong> natural order.<br />

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