| supergravity | |
|---|---|
| Name | Supergravity |
| Field | Theoretical physics |
| Introduced | 1976 |
| Proponents | Daniel Freedman, Peter van Nieuwenhuizen, Sergio Ferrara |
| Related | Supersymmetry, General relativity, String theory |
supergravity
Supergravity is a field theory combining supersymmetry with general relativity to produce a locally supersymmetric theory of gravitation. It emerged in the mid-1970s as an extension of quantum field theory that incorporates a spin-3/2 fermionic gauge field, the gravitino, and it plays a central role in attempts to reconcile gravity with the principles of quantum mechanics. Supergravity matters because it offers a mathematically constrained framework for low-energy limits of string theory and for studying quantum aspects of the gravitational interaction.
Supergravity was first formulated in 1976 by Freedman, van Nieuwenhuizen and Ferrara at a time when the community sought extensions of global supersymmetry such as those studied by Wess and Zumino. Early developments connected to work on superalgebras by Golfand and Likhtman and to the construction of supermultiplets in Moscow and Princeton. The 1980s saw classification of extended supergravities by number of supercharges (N) and formulation of higher-dimensional models in eleven-dimensional supergravity by Witten and Townsend building on work by Cremmer, Julia, and Scherk. Institutional support from groups at CERN, IAS, Caltech, and MIT accelerated applications to string theory and cosmology.
Supergravity unites principles of local gauge invariance in quantum field theory with the diffeomorphism invariance of general relativity. The local realization of supersymmetry implies the gravitino is a gauge field associated with local supersymmetry transformations, paralleling how the photon appears for U(1) gauge symmetry. Quantization attempts confront the standard perturbative non-renormalizability of pure gravity explored in the work of ’t Hooft and Veltman, but extended supersymmetry improves ultraviolet behavior, as studied in calculations by Bern and collaborators. Supergravity therefore occupies a bridge role between effective field theory approaches to gravity (e.g., Effective field theory) and nonperturbative frameworks like loop quantum gravity and string theory.
Mathematically, supergravity is founded on graded Lie algebras known as superalgebras (e.g., the Super-Poincaré algebra) and uses spinor bundles over pseudo-Riemannian manifolds. Formulations include minimal N=1 supergravity in four dimensions, extended N>1 models, and higher-dimensional theories such as 11-dimensional supergravity. Theories are constructed from supermultiplets like the gravity multiplet, vector multiplets, and hypermultiplets; Lagrangians respect local supersymmetry via the Noether procedure and employ tools from differential geometry, Clifford algebras, and cohomological methods developed by BRST. Duality symmetries such as S-duality and U-duality emerge in compactifications and relate supergravity solutions to p-branes and black hole solutions studied by Strominger and Vafa.
Supergravity predicts the gravitino, which couples to the supercurrent and acquires mass when local supersymmetry is broken. Models embed the MSSM into supergravity frameworks as supergravity-mediated supersymmetry breaking scenarios, including gravity mediation and anomaly mediation. The spectrum depends on the number of supercharges: N=1 gives a single gravitino, while extended theories include multiple gravitini and higher-spin fields. Supersymmetry breaking mechanisms invoke sectors such as hidden sector dynamics, F-term and D-term breaking, and cosmological constraints from Big Bang nucleosynthesis place bounds on the gravitino lifetime and mass. Experimental constraints also derive from searches at LHC collaborations like ATLAS and CMS for superpartners predicted in supergravity-inspired models.
Supergravity serves as the low-energy effective theory of various string theory and M-theory compactifications, connecting to heterotic, type II, and eleven-dimensional constructions studied by Polchinski and others. Eleven-dimensional supergravity is the low-energy limit of M-theory, while ten-dimensional supergravities correspond to type IIA, IIB and heterotic strings. Compactification on Calabi–Yau spaces and flux compactifications produce four-dimensional models with moduli stabilization studied in the KKLT scenario and by researchers at Stanford and Harvard. Supergravity also informs grand unification models (e.g., SU(5) and SO(10) embeddings) and the calculation of string-loop corrections and anomalies, with implications for gauge coupling unification.
Phenomenological studies derive soft supersymmetry-breaking terms, dark matter candidates such as the neutralino or gravitino, and collider signatures including missing transverse energy and long-lived particles. Precision tests of gravity, searches for deviations from the inverse-square law, and cosmological observations from Planck and WMAP constrain parameter regions. Direct searches for supersymmetric particles at CERN have pushed typical supergravity-inspired minimal models to higher mass scales, motivating alternative scenarios explored by groups at Fermilab and in global fits by the PDG.
Supergravity provides tractable models for black hole microstate counting, entropy calculations, and holographic dualities such as the AdS/CFT correspondence proposed by Maldacena, linking supergravity in anti-de Sitter space to CFT on the boundary. Cosmological applications include inflationary model building, analysis of the cosmological constant problem, and studies of early-universe dynamics including reheating and gravitino production. Supergravity-based constructions inform investigations into landscape and vacuum selection in the string landscape and contribute to debates about naturalness and stability central to contemporary theoretical physics.
Category:Theoretical physics Category:Quantum gravity Category:Supersymmetry