Black Holes and Quantum Gravity Benjamin A. Burrington
Mathematical Descriptions: Predictions
• The black hole, predicted by general relativity, has a description through a solution metric for spacetime. Simplest is Schwarzchild solution (1917)
• Can use to compute models of • Describes a gravitational accretion disk, lensing of light, “funnel” from which not even and other properties light cannot escape: [NASA image]
Clues for Quantum Gravity
• General relativity is a “classical” theory: not quantum. • When coupled to quantum field theory, predicts radiation (Hawking, 1974)
AdS/CFT and Black Holes
• String theory has objects, • The open strings and interactions are described by a called D-branes, where gauge theory at low energy. open strings end.
g
Hawking radiation
Large N Limit
Virtual Pair
Large ‘t Hooft Coupling
• Radiation implies temperature, which implies entropy, which implies # of quantum states… a HUGE amount of states, in the case of black holes: • entropy of solar mass bh: 10^77 thermal entropy of sun : 10^57
Black Holes: Observations
• Black holes have now been observed indirectly through gravitational effects: (Sagittarius A*) (2002) [Max Planck, NYT image]
• Indirect observation through gravitational waves: (LIGO, 2015)
• In this limit, the gauge theory becomes a string theory.
• Quantum theories of gravity must be able to count the states.
• Field theory at strong coupling well defined as quantum theory.
String Theories & Counting
• String theories are quantum theories, and contain gravity: accomplish counting for symmetric black holes by counting string and brane windings:
[Image: Wikipedia]
• And through direct imaging (Event horizon telescope, M87, 2019)
• The string theory in question is as above, with target curved background, anti-de Sitter space (AdS). (AdS/CFT or the Maldacena conjecture, 1998)
Wrapped Branes Pointlike • String theories also contain gauge theories: standard particle theory tools… but with new perspectives.
• Duality gives a new way to define quantum gravity: address counting of quantum states using field theory dual to count states • Characterize other properties of BH as well.