Further Results on Overlarge Sets of Kirkman Triple Systems
Landang Yuan and Qingde Kang
Institute of Mathematics, Hebei Normal University, Hebei 050016,
P. R. China
Abstract Full Text PDF
An Steiner triple system of
order $v$, denoted by $STS(v)$, is a pair $(X, {\cal B})$, where
$X$ is a $v$-set, ${\cal B}$ is a collection of triples on $X$,
such that each 2-set of $X$ occurs in exactly one triple of ${\cal
B}$. An $STS(v)=(X,{\cal B})$ is resolvable, denoted by
$KTS(v)$, if there exists a partition
$\Gamma=\{P_1,P_2,\cdot\cdot\cdot,P_{\frac{v-1}{2}}\}$ of ${\cal
B}$ such that each part $P_i$, called parallel class, forms
a partition of $X$. It is well known that there exists a $KTS(v)$
if and only if $v\equiv3$ mod 6.
An overlarge set of Kirkman triple systems, denoted by
$OLKTS(v)$, is a collection $\{(X\backslash\{x\},{\cal B}_x)\colon
x\in X\}$, where $X$ is a $(v+1)$-set, each
$(X\backslash\{x\},{\cal B}_x)$ is a $KTS(v)$, and these ${\cal
B}_x,~x\in X$, partition all triples on $X$.
The existence of $OLKTS(v)$
has been investigated. The known results are that
there exists an $OLKTS(v)$ for $v=9,~4^n-1$ and $2q^n+1$, where $n \geq 1$
and prime power $q=13$ or $q\equiv 7~({\rm mod ~12})$.
In this paper, in order to study $OLKTS(v)$, we introduce a kind of
auxiliary designs---overlarge sets of generalized Kirkman systems,
and obtain some results for its existence. Our main conclusion is
to exist an $OLKTS(6u+3)$ for $u=2^{2n+1}-1,~7^n,~31^n$ and
$127^n$, where $n\geq1$.