Domination-type parameters are difficult to manage in Cartesian product graphs and there is usually no general relationship between the parameter in both factors and in the product graph. This is the situation of the domination number, the Roman domination number or the $2$-domination number, among others. Contrary to what happens with the domination number and the Roman domination number, the $2$-domination number remains unknown in cylinders, that is, the Cartesian product of a cycle and a path and in this paper, we will compute this parameter in the cylinders with small cycles. We will develop two algorithms involving the $(\min,+)$ matrix product that will allow us to compute the desired values of $\gamma_2(C_n\Box P_m)$, with $3\leq n\leq 15$ and $m\geq 2$. We will also pose a conjecture about the general formulae for the $2$-domination number in this graph class.
翻译:在笛卡尔产品图表中难以管理定额类型参数,而且两个系数和产品图表中通常没有参数之间的一般关系。这是支配号、罗马支配号或2美元定额数等情况。与支配号和罗马支配号不同,2美元定额数在气瓶中仍然不为人知,即一个循环和路径的笛卡尔产品。在本文件中,我们将在小周期的气瓶中计算这个参数。我们将开发两种涉及$(min,+)美元矩阵产品的算法,使我们能够用3\leq nleq 15美元和$m\geq 2美元来计算$(gamma_2(C_n\Box P_m)的预期值。我们还将对这个图形类中的$$($)定额数字的一般公式进行描述。