Module 1 · The Quantum-Gravity Programme
Strings, Supergravity & Unification
The largest single thread of modern theoretical physics is the search for a quantum theory of gravity unified with the other three forces. String theory, supergravity, and the duality web that connects them have produced ICTP Dirac Medals in nearly every decade since the 1980s. The five lectures in this module survey their key ideas in the laureates’ own words.
Michael Green — the First Superstring Revolution
Michael Green and John Schwarz received the Dirac Medal in 1989 (with Yoichiro Nambu and others honoured separately for related work) for showing that the superstring theory of type I in ten dimensions is anomaly-free for gauge group SO(32) or E8×E8 — the Green–Schwarz mechanism of 1984. This single calculation triggered the “first superstring revolution” and made superstring theory a mainstream candidate for unified physics.
Michael Green — Dirac Medal Lecture, Part 1
Green surveys the path from dual-resonance models through the anomaly-cancellation calculation to modern superstring theory and the early hints of M-theory.
Michael Green — Dirac Medal Lecture, Part 2
Continuation: scattering amplitudes, modular forms in type IIB, and the role of supersymmetry in producing finite quantum-gravity amplitudes.
John Schwarz — Superconformal Field Theories
Schwarz, who with Green proved anomaly cancellation in 1984, is one of the architects of the entire superstring programme. In this lecture he focuses on superconformal field theories — the worldsheet theories that define string backgrounds, and the theories living on D-brane worldvolumes that, via the AdS/CFT correspondence, encode quantum gravity in higher dimensions.
John Schwarz — Superconformal Field Theories, Part 1
The structure of N = 4 super-Yang–Mills, its conformal symmetry, and its role as the holographic dual of type IIB string theory on AdS₅ × S₅.
John Schwarz — Superconformal Field Theories, Part 2
Six-dimensional (2,0) theory, M5-branes, and the still-mysterious non-Lagrangian SCFTs that string theory predicts must exist.
Joseph Polchinski — Holography and Unification
Joseph Polchinski (1954–2018) discovered that D-branes — surfaces on which open strings end — are the carriers of Ramond-Ramond charges (1995), an insight that triggered the “second superstring revolution” and made Maldacena’s 1997 AdS/CFT discovery possible. He shared the 2008 Dirac Medal with Maldacena and Strominger.
Joseph Polchinski — Holography and Unification, Part 1
The web of dualities between five superstring theories, M-theory in 11 dimensions, and the role of D-branes as the bridge between geometry and gauge theory.
Joseph Polchinski — Holography and Unification, Part 2
The AdS/CFT correspondence as a precise realisation of the holographic principle, and what it tells us about black-hole information, entanglement, and emergent spacetime.
Cumrun Vafa — Strings and Geometry
Cumrun Vafa (Dirac Medal 2008, with Polchinski and Strominger) is a leading architect of the deep ties between string theory and pure mathematics — mirror symmetry, F-theory, the Strominger–Vafa microstate counting for black-hole entropy (1996), and more recently the swampland programme that delineates the boundary between effective theories that can be UV-completed in quantum gravity and those that cannot.
Cumrun Vafa — Strings and Geometry, Part 1
Calabi–Yau compactifications, mirror symmetry, and how string theory continues to predict (and sometimes prove) deep statements in algebraic geometry.
Cumrun Vafa — Strings and Geometry, Part 2
F-theory, the geometry behind elliptic fibrations, and how 8-dimensional Calabi–Yau spaces realise the most generic backgrounds of type IIB string theory.
Sergio Ferrara — Black Holes and Supergravity
Sergio Ferrara (Dirac Medal 1993, shared with Daniel Z. Freedman and Peter van Nieuwenhuizen) was one of the discoverers of supergravity — the supersymmetric extension of general relativity, in 1976. Supergravity remains the standard low-energy effective theory of every superstring vacuum and underlies modern black-hole microstate counting and AdS/CFT phenomenology.
Sergio Ferrara — Black Holes and Supergravity, Part 1
The construction of N = 1 supergravity in 4 dimensions, the role of the gravitino, and how the algebra closes off-shell with auxiliary fields.
Sergio Ferrara — Black Holes and Supergravity, Part 2
Extremal black holes in N = 2 supergravity, attractor mechanisms, and Strominger–Vafa-style microstate counting for BPS states.