Alan,

I read a very similar book more recently, now I'll have to look up that title too

>Umpteen years ago, James P. Hogan wrote a book in which a scientist sent messages back in time using "tau" radiation to stop a project he was working on himself. The book was "Thrice Upon a Time". Very good book by a very good writer (until he stopped writing SciFi and started with political thrillers).