for the Popular Science. Renate Loll: physicist who worked on loop quantum gravity and more recently helped develop the causal dynamical triangulations approach to quantum gravity. Luboš Motl: physicist who worked on string theory. Fotini Markopoulou-Kalamara: physicist who works on loop quantum gravity and spin network models that take causality into account. Leonardo Modesto: physicist who works on Nonlocal Quantum Gravity a unitary and finite theory of quantum gravity in the quantum field theory framework. Roger Penrose: mathematical physicist who invented spin networks and twistor theory. Jorge Pullin: physicist who helped develop loop quantum gravity, co-author of Loops, Knots, Gauge Theories and Quantum Gravity. Carlo Rovelli: one of the founders and major contributors to loop quantum gravity. Lee Smolin: one of the founders and major contributors to loop quantum gravity. Rafael Sorkin: physicist, primary proponent of the causal set approach to quantum gravity. Andrew Strominger: physicist who works on string theory. Leonard Susskind: physicist who is considered to be one of the three fathers of string theory. Frank J. Tipler: mathematical physicist who incorporates quantum gravity into his ideas of a Judeo-Christian God. Bill Unruh: physicist engaged in the study of semiclassical gravity and responsible for the discovery of the so-called Unruh effect. Cumrun Vafa: physicist and developer of F-theory, known for Vafa-Witten theorem and Gopakumar-Vafa conjecture. Robert Wald: physicist in the field of quantum field theory in curved spacetime. Anzhong Wang: physicist, major contributor to Horava-Lifshitz gravity; String theory and applications to cosmology. Paul S. Wesson: physicist, cosmologist and writer, known as founder of the "Space-time Consortium" and his work on Kaluza–Klein theory. John Archibald Wheeler: physicist in the field of quantum gravity due to his development, with Bryce DeWitt, of the Wheeler–DeWitt equation. Edward Witten: mathematical physicist in string theory and M-Theory See also List of loop quantum gravity researchers List of string theorists List of contributors to general relativity References Lists of physicists by field Research-related lists