I think I have seen an algorithm that has $x^{1.5}$ as its complexity. However, according to Wikipedia, it states that the complexity class P is defined as $\bigcup_{k\in\mathbb{N}} \mbox{DTIME}(n^k)$. So does this mean that only natural numbers are allowed in $k$ in the complexity class P? Or am I mistaken, and there is no algorithm that has rational number as $k$?
Thanks.