Overruling a prominent dean, the president of Columbia University, Lee Bollinger, yesterday withdrew an invitation to the Iranian president, Mahmoud Ahmadinejad. The dean of Columbia's school of international and public affairs, Lisa Anderson, had independently invited Mr. Ahmadinejad to speak at the World Leader's Forum, a year-long program that aims to unite "renowned intellectuals and cultural icons from many nations to examine global challenges and explore cultural perspectives." In a statement issued yesterday afternoon, Mr. Bollinger said he canceled Mr. Ahmadinejad's invitation because he couldn't be certain it would "reflect the academic values that are the hallmark of a University...