How would I use the pumping lemma to show L = {(ab^n)(ab^n), n>=0} is not regular?
What I would do is this:
Choose s=ab^p ab^p
and |xy| <= p so xy = a because ab^p would be one more always
so if you increase the value of a y (ay^iz) then u would have more a's in the first section than the second, hence it is not regular?