Warped Passages - Lisa Randall [167]
Theories that sequester particles have the potential to solve many problems. The story about Ike refers to my first foray into extra dimensions—the application of sequestering to supersymmetry breaking. Whereas four-dimensional theories face serious problems because supersymmetry-breaking models generally introduce unwanted interactions, sequestered supersymmetry-breaking models appear to be far more promising. Sequestering might also explain why particles have different masses from one another, and why proton decay does not occur in extra-dimensional models. In this chapter, we’ll explore sequestering and a few of its particle physics applications. We’ll see how even ideas, such as supersymmetry, that we thought applied to four-dimensional spacetime might be more successful in an extra-dimensional context.
My Passage to Extra Dimensions
We physicists are fortunate to have many conference opportunities to meet and share stimulating research ideas with colleagues. But such an overwhelming number of conferences and workshops in particle physics are held each year that choosing which invitations to accept can be difficult. Some are major gatherings that provide an opportunity to hear about others’ recent work and to share your latest results. Some are relatively short conferences, lasting two or three days, in which physicists report major new results in a highly specialized field. Other meetings are longer workshops where physicists begin or complete collaborations with colleagues. Sometimes conferences are held in such spectacular locations they are just too good to miss.
Although Oxford is a very nice place, the supersymmetry conference that I attended there in early July of 1998 fits best into the first category. Supersymmetry, which for many years was considered the only possible way out of the hierarchy problem, has evolved over time into a major research area, and every year physicists gather to discuss recent progress in the field.
The Oxford conference held a surprise, however. The most interesting topic was not supersymmetry, but the newly emergent idea of extra dimensions. One of the most stimulating talks was about large extra dimensions, the subject of Chapter 19. Other talks were on the fate of string theory’s extra dimensions, and still others discussed potential experimental implications of extra dimensions. The novelty and speculative nature of such ideas was clear from the title of Chicago theorist Jeff Harvey’s talk: he and several later speakers jokingly named their talks after Fantasy Island. Joe Lykken, a theorist from Fermilab, even had a slide with a little man pointing to “Da brane. Da brane.” (Needless to say, the joke about Tattoo, famous for welcoming “da plane” to Fantasy Island, was lost on those who had not experienced the joys of American seventies TV.)
Despite the jokes, I returned from the Oxford supersymmetry conference thinking about extra dimensions and why problems in particle physics might be solved in an extra-dimensional world. Although I was skeptical about the large extra dimensions that was one of the hot topics, and did not plan to work on them myself, I was fairly convinced that branes and extra dimensions could be important model building tools with the potential to explain some of the mysterious particle physics phenomena that have defied simple four-dimensional explanations.
That year I was planning