July 26, 2016 0:28 WSPC/INSTRUCTION FILE review˙2016July23 International Journal of Modern Physics A c World Scientific Publishing Company What lattice theorists can do for superstring/M-theory MASANORI HANADA Yukawa Institute for Theoretical Physics Kyoto University, Kyoto 606-8502, JAPAN The Hakubi Center for Advanced Research Kyoto University, Kyoto 606-8501, JAPAN Stanford Institute for Theoretical Physics Stanford University, Stanford, CA 94305, USA
[email protected] The gauge/gravity duality provides us with nonperturbative formulation of superstring/M-theory. Although inputs from gauge theory side are crucial for answering many deep questions associated with quantum gravitational aspects of superstring/M- theory, many of the important problems have evaded analytic approaches. For them, lattice gauge theory is the only hope at this moment. In this review I give a list of such problems, putting emphasis on problems within reach in a five-year span, including both Euclidean and real-time simulations. Keywords: Lattice Gauge Theory; Gauge/Gravity Duality; Quantum Gravity. PACS numbers:11.15.Ha,11.25.Tq,11.25.Yb,11.30.Pb Preprint number:YITP-16-28 1. Introduction During the second superstring revolution, string theorists built a beautiful arXiv:1604.05421v2 [hep-lat] 23 Jul 2016 framework for quantum gravity: the gauge/gravity duality.1, 2 It claims that superstring/M-theory is equivalent to certain gauge theories, at least about certain background spacetimes (e.g. black brane background, asymptotically anti de-Sitter (AdS) spacetime). Here the word ‘equivalence’ would be a little bit misleading, be- cause it is not clear how to define string/M-theory nonperturbatively; superstring theory has been formulated based on perturbative expansions, and M-theory3 is defined as the strong coupling limit of type IIA superstring theory, where the non- perturbative effects should play important roles.