Hollywood hunk Josh Hartnett has hinted he enjoys lengthy Tantric sex sessions with his stunning girlfriend Scarlett Johansson. The SIN CITY star has been dating Lost In Translation beauty Johansson since meeting on the set of The Black Dahlia in Bulgaria last April (06). Recently, Hartnett admitted he has been studying the New Age sexual method for some time. Hartnett confesses, "A friend of mine gave me a book on Tantric sex for my birthday. "I studied it to see what all the fuss was about. It's not easy but it's all good."