Initially, Gerard O’Reilly is a little intense.  Framed in a well-cut dark suit, O’Reilly sits in The Ivy restaurant in Dublin, where he orders a simple fish meal. O’Reilly asks lots of questions and, unlike many people, drills into the answers. But O’Reilly is not like most people. He has a doctorate in aeronautics from the California Institute of Technology, one of America’s best universities, commonly known as Caltech. And the Waterford native has also risen to the top of Dimensional, an investment firm with $777 billion in assets under management. But as the conversation continues, O’Reilly warms up and…