‎A $mu$-way $(v,k,t)$ $trade$ of volume $m$ consists of $mu$‎ ‎disjoint collections $T_1$‎, ‎$T_2‎, ‎dots T_{mu}$‎, ‎each of $m$‎ ‎blocks‎, ‎such that for every $t$-subset of $v$-set $V$ the number of‎ ‎blocks containing this t-subset is the same in each $T_i (1leq‎ ‎i leq mu)$‎. ‎In other words any pair of collections ${T_i,T_j}$‎, ‎$1leq i< j leq mu‎$ is a $(v,k,t)$ trade of volume $m$. In th...

‎a $mu$-way $(v,k,t)$ $trade$ of volume $m$ consists of $mu$‎ ‎disjoint collections $t_1$‎, ‎$t_2‎, ‎dots t_{mu}$‎, ‎each of $m$‎ ‎blocks‎, ‎such that for every $t$-subset of $v$-set $v$ the number of‎ ‎blocks containing this t-subset is the same in each $t_i (1leq‎ ‎i leq mu)$‎. ‎in other words any pair of collections ${t_i,t_j}$‎, ‎$1leq i< j leq mu‎$ is a $(v,k,t)$ trade of volume $m$. in th...

A q-analog of a Steiner system (briefly, q-Steiner system), denoted by S = Sq[t, k, n], is a set of k-dimensional subspaces of F n q such that each t-dimensional subspace of Fq is contained in exactly one element of S. Presently, q-Steiner systems are known only for t = 1 and in the trivial cases t = k and k = n. In this paper, the first known nontrivial q-Steiner systems with t ≥ 2 are constru...

Let Fn q be a vector space of dimension n over the finite field Fq . A q-analog of a Steiner system (also known as a q-Steiner system), denoted Sq(t,k,n), is a set S of k-dimensional subspaces of Fn q such that each t-dimensional subspace of Fn q is contained in exactly one element of S . Presently, q-Steiner systems are known only for t = 1, and in the trivial cases t = k and k= n. In this pap...

We study the Euclidean bottleneck Steiner tree problem: given a set P of n points in the Euclidean plane, called terminals, find a Steiner tree with at most k Steiner points such that the length of the longest edge in the tree is minimized. This problem is known to be NP-hard even to approximate within ratio √ 2. We focus on finding exact solutions to the problem for a small constant k. Based o...

We are interested in what sizes of cliques are to be found in any arbitrary spanning graph of a Steiner triple system S. In this paper we investigate spanning graphs of projective Steiner triple systems, proving, not surprisingly, that for any positive integer k and any sufficiently large projective Steiner triple system S, every spanning graph of S contains a clique of size k.

Given two sets of points in the plane, P of n terminals and S of m Steiner points, a Steiner tree of P is a tree spanning all points of P and some (or none or all) points of S. A Steiner tree with length of longest edge minimized is called a bottleneck Steiner tree. In this paper, we study the Euclidean bottleneck Steiner tree problem: given two sets, P and S, and a positive integer k ≤ m, find...

We present the first exact algorithm for constructing minimum bottleneck 2-connected Steiner networks containing at most k Steiner points, where k > 2 is a constant integer. The objective of the problem is – given a set of n terminals embedded in the Euclidean plane – to find the locations of the Steiner points, and the topology of a 2-connected graph Nk spanning the Steiner points and the term...

We introduce a temporal Steiner network problem in which a graph, as well as changes to its edges and/or vertices over a set of discrete times, are given as input; the goal is to find a minimal subgraph satisfying a set of k time-sensitive connectivity demands. We show that this problem, k-Temporal Steiner Network (k-TSN), is NP-hard to approximate to a factor of k − , for every fixed k ≥ 2 and...