An Unexpected LinkĪn effort to solve some of LQG’s own internal problems has led to the first surprising link with string theory. Combining LQG and string theory would truly make it the only game in town. Moreover, in the absence of experimental evidence for either string theory or LQG, mathematical proof that the two are in fact opposite sides of the same coin would bolster the argument that physicists are progressing toward the correct theory of everything. A young generation of string theorists has begun to look outside string theory for methods and tools that might be useful in the quest to understand how to create a “theory of everything.” And a still-raw paradox involving black holes and information loss has given everyone a fresh dose of humility. New theoretical findings have revealed potential similarities between LQG and string theory. I think it’s unfortunate that it developed this way.”Įmily Fuhrman for Quanta Magazine, with text by Natalie Wolchover and art direction by Olena Shmahalo.īut a number of factors may be pushing the camps closer together. They don’t even go to ‘physics’ conferences anymore. Stringy people go to stringy conferences. “Conferences have segregated,” said Jorge Pullin, a physicist at Louisiana State University and co-author of an LQG textbook. ![]() These and other differences have split the theoretical physics community into deeply divergent camps. String theory also implies the existence of supersymmetry, in which all known particles have yet-undiscovered partners. String theory requires that space-time have 10 dimensions LQG doesn’t work in higher dimensions. Specific technical problems separate the fields. For starters, LQG studies bits of space-time, whereas string theory investigates the behavior of objects within space-time. Indeed, the conceptual differences are obvious and profound. This approach has long been thought incompatible with string theory. LQG is in large part a study of these chunks. In this way, space is built up of discrete chunks. The smooth background of Einstein’s theory of gravity is replaced by nodes and links to which quantum properties are assigned. In loop quantum gravity, or LQG, space-time is a network. Loop quantum gravity, by contrast, is concerned less with the matter that inhabits space-time than with the quantum properties of space-time itself. And in these manifold appearances lie the explanations for all phenomena we observe, both matter and space-time included. The strings may be closed unto themselves or have loose ends they can vibrate, stretch, join or split. ![]() Its premise is simple: Everything is made of tiny strings. ![]() Among the attempts to unify quantum theory and gravity, string theory has attracted the most attention.
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