Even Hollywood heroes like Chris Hemsworth harbor fears that AI is up to no good . It’s a well-worn trope in traditional dystopian AI stories , like “Colossus: The Forbin Project” and the “Terminator” movies: A super-smart artificial intelligence program attains self-awareness and seeks to dominate or exterminate humanity.  And in a played-for-laughs new ad for Amazon, Hemsworth envisions various ways the company’s “AI helper” could decapitate, drown or otherwise murder him. But there are other,