String Theory

In the past few hundred years, scientists have searched for fundamental laws of nature by exploring phenomena at shorter and shorter distances. Does this progression continue indefinitely? Surprisingly, there are reasons to think that the hierarchical structure of nature will terminate at 1035 meter, the so-called Planck length. Let us perform a thought-experiment to explain why this might be the case. Physicists build particle colliders to probe short distances. The more energy we use to collide particles, the shorter distances we can explore. This has been the case so far. One may then ask: can we build a collider with energy so high that it can probe distances shorter than the Planck length? The answer is no. When we collide particles with such high energy, a black hole will form and its event horizon will conceal the entire interaction area. Stated in another way, the measurement at this energy would perturb the geometry so much that the fabric of space and time would be torn apart. This would prevent physicists from ever seeing what is happening at distances shorter than the Planck length. This is a new kind of uncertainty principle. The Planck length is truly fundamental since it is the distance where the hierarchical structure of nature will terminate.

Space and time do not exist beyond the Planck scale, and they should emerge from a more fundamental structure. Superstring theory is a leading candidate for a mathematical framework to describe physics at the Planck scale since it contains all the ingredients necessary to unify general relativity and quantum mechanics and to deduce the Standard Model of particle physics. Superstring theory has helped us solve various mysteries of quantum gravity such as the information paradox of black holes posed by Stephen Hawking. The theory has given us insights into early universe cosmology and models beyond the Standard Model of particle physics. It provides powerful tools study many difficult problems in theoretical physics - often involving strongly interacting systems - such as QCD (theory of quark interactions), quantum liquid and quantum phase transitions. It has also inspired many important developments in mathematics. All of these aspects of string theory are vigorously investigated at IPMU.

Group Members

Damien Easson

Building models of inflation from string theory. Time dependent solutions in string theory. Brane Gas model of string cosmology.

Dongfeng Gao

Mathematical aspects of string theory.

Jose Figueroa O'Farrill

AdS/CFT, M2-brane theories, and supergravity solutions.

Simeon Hellerman

String theory and its connections to quantum gravity, cosmology, condensed matter, particle physics and mathematics. Development of tools to understand and apply string theory in generic environments.

Minxin Huang

Aspects of the AdS/CFT correspondence such as pp-waves, and giant gravitons. Topological string theory.

Kentaro Hori

4d N=1 string compactifications in various frameworks, especially, worldsheet approaches to Type II orientifolds with D-branes and fluxes, M-theory on G_ 2 holonomy manifolds, worldsheet approaches to heterotic strings. Topological strings as well as supersymmetric gauge theories in various dimensions.

Shinobu Hosono

Mirror symmetry of Calabi-Yau manifolds and its applications to Gromov-Witten theory.

Toshiya Imoto

Holographic QCD.

Daniel Krefl

Topological string theory and mirror symmetry with O-planes and D-branes.

Wei Li

Black holes. Gauge/Gravity correspondence. 3D quantum gravity.

Andrei Mikhailov

String worldsheet theory, Green-Schwarz and pure spinor formalism, AdS/CFT, integrability.

Shinji Mukohyama

String cosmology.

Tatsuma Nishioka

Gauge/Gravity Duality, Black Hole Physics.

Hirosi Ooguri

Development of theoretical tools to apply string theory to questions relevant to high energy physics, astrophysics, and cosmology.

Domenico Orlando

Exact CFT solutions. Topological strings. Integrable models. Effective descriptions for M-theory.

Susanne Reffert

String compactifications. Topological string theory. Relation to integrable models.

Ken Shackleton

Connection between string theory and the completion of the Weil-Petersson metric on Teichmueller space.

Cornelius Schmidt-Colinet

Conformal field theory and its applications in string theory.

Yogesh Srivastava

Black Holes in String Theory, Gauge-Gravity correspondence and its applications in various fields.

Shigeki Sugimoto

Conjectured duality between string theory and gauge theory, and its application to QCD and hadron physics.

Tadashi Takayanagi

String theory as quantum gravity especially from the viewpoint of holography such as AdS/CFT duality. Relation between the entanglement entropy and the gravitational entropy such as the black hole entropy.

Taizan Watari

String phenomenology. Inflation (in the past). GUT and F-theory compactification.