Strings Untangled

How many string theorists does it take to have a fascinating roundtable discussion about the past, present and future of the field? In a recent case at ICTP: four.­

The 2014 Dirac Medallists Gabriele Veneziano, Andrew Strominger and Ashoke Sen, and new ICTP research scientist Atish Dabholkar, sat down for a relaxed discussion after the Dirac Medal ceremony held during ICTP's 50th Anniversary celebrations about string theory, its origins, and the impact it has had on physics.  Their discussion, which was captured on video, gives insights into successes and set backs of string theory and the medallists tackle some tough questions that Dabholkar puts forth. "I know these are very hard problems," Dabholkar says at one point during the discussion, "but since you are Dirac Medallists I can ask you these questions."

Veneziano, who is considered a pioneer of string theory, began laying the foundations for the field back in the 1960s when he discovered the Veneziano Amplitude. "[It was] not an accidental discovery, this description of string theory. We started from a bottom-up approach," he says. "Now the field has grown...it's like your baby that you don't recognise anymore.... it has gown up so much."

Strominger and Sen are two string theorists who have nurtured the field and contributed to its growth. "It's so interesting to listen to Gabriele's personal recollection," says Strominger. "When he discovered the Veneziano formula, it was a little bit disappointing that it didn't describe hadrons. Of course, what it did describe, I think, is more wonderful than anything you imagine...The truth about the laws of physics is more wonderful and more interesting than our imagination."

Strominger's co-discovery of Calabi-Yau compactifications allowed string theory to emerge as one of the candidates for the unified theory of nature. "If somebody in 1985 had predicted what was to come [in string theory], they would have been dismissed as optimistic fools," he says.

String theory, today, provides tools and a framework that can be used to solve problems posed by other fields including condensed matter physics, hydrodynamics, and the study of black holes. Ashoke Sen, who has contributed significantly to string theory, especially in studies related to duality and black holes, says, "That fact is that string theory can explain so many different properties of black holes, it is unthinkable for any rival theory." Sen was one of the first recipients of the Fundamental Physics Prize "for opening the path to the realisation that all string theories are different limits of the same underlying theory." "My experience is that in this field you cannot really plan your research because to do something you may need some more information, which you don't have at that time," says Sen. "So, you basically explore the theory in all possible ways. And then, when the time is right, you'll make a breakthrough in one particular front."

The complete discussion— "The Dirac Roundtable”— can be viewed on ICTP's YouTube channel. Scientific talks presented by the medallists during the ceremony are also available. The 2014 Dirac medal was awarded to the three physicists for their crucial contributions to the origin, development and further understanding of string theory.