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| Emergent gravity | |
|---|---|
| Name | Emergent gravity |
| Field | Theoretical physics |
| Notable figures | Eric Verlinde, Ted Jacobson, Gerard 't Hooft, Leonard Susskind, Juan Maldacena, Carlo Rovelli, Roger Penrose, Kip Thorne, Subrahmanyan Chandrasekhar, Stephen Hawking |
| Institutions | Institute for Advanced Study, CERN, Perimeter Institute, Harvard University, Princeton University, University of Cambridge, Stanford University, MIT, Caltech |
Emergent gravity is a research program proposing that the gravitational interaction arises as an effective, macroscopic phenomenon from underlying microscopic degrees of freedom rather than as a fundamental force. It connects ideas from General relativity, Quantum field theory, Statistical mechanics, Condensed matter physics, Quantum information theory, and Thermodynamics, and has motivated interdisciplinary work across institutes such as the Institute for Advanced Study, CERN, and the Perimeter Institute.
Emergent gravity posits that spacetime, inertia, and gravitational dynamics emerge from entropic, thermodynamic, or quantum-informational substrates rather than being fundamental entities, linking concepts from Black hole thermodynamics, Holographic principle, Gauge/gravity duality, AdS/CFT correspondence, Bekenstein–Hawking entropy, and Unruh effect. Proponents draw on results from Loop quantum gravity, String theory, Causal set theory, Tensor network models, and analogies with Superfluid helium, Fractional quantum Hall effect, and Topological insulator systems to argue that emergent laws reproduce the Einstein field equations in appropriate limits. Critics compare these efforts to historical analogies such as the transition from Phlogiston theory to Chemical thermodynamics or from Ptolemaic system to Copernican heliocentrism.
Early precursors include thermodynamic analyses by Jacob Bekenstein and studies of black holes by Stephen Hawking that linked entropy and geometry, developments continued with Ted Jacobson deriving Einstein equations from thermodynamic relations and with conceptual pushes from Gerard 't Hooft and Leonard Susskind proposing holography and information-based descriptions. The 1990s saw maturation through Juan Maldacena's formulation of the AdS/CFT correspondence and debates involving Edward Witten, Andrew Strominger, Cumrun Vafa, and Joseph Polchinski. In the 21st century, figures such as Erik Verlinde popularized entropic gravity proposals, while researchers at Harvard University, Princeton University, Stanford University, and MIT explored tensor networks and quantum error correction in connection with spacetime emergence; parallel work at Perimeter Institute and Caltech examined condensed-matter analogues and analogue gravity experiments inspired by William Unruh and Matt Visser.
Approaches to emergent gravity include entropic or thermodynamic derivations (e.g., proposals by Erik Verlinde, building on Jacobson), holographic reconstructions using AdS/CFT correspondence and Quantum error correction as articulated by Almheiri, Dong, and Harlow, and condensed-matter inspired models from Xiao-Gang Wen and Subir Sachdev invoking emergent gauge fields and fractionalization seen in Quantum spin liquid phases. Other frameworks involve causal sets advanced by Rafael Sorkin, group field theory linked to Carlo Rovelli and Daniele Oriti, and approaches employing Tensor network states influenced by Guifre Vidal and Brian Swingle. String-theoretic contexts developed by Edward Witten, Joseph Polchinski, Cumrun Vafa, and Juan Maldacena connect to emergent geometry via D-brane constructions from Polchinski and dualities studied by Ashoke Sen. Semiclassical formulations reference work by Roger Penrose, Kip Thorne, and Stephen Hawking on gravitational entropy and singularity theorems, while information-theoretic treatments invoke Charles Bennett, Peter Shor, and John Preskill on quantum information measures.
A central thread links spacetime geometry to entanglement structure, exemplified by the Ryu–Takayanagi formula developed by Shinsei Ryu and Tadashi Takayanagi in holography and by Mark Van Raamsdonk's arguments about entanglement building geometry, with subsequent refinements by Matthew Headrick and Thomas Faulkner. Tensor network analogies from Guifre Vidal and Brian Swingle map entanglement patterns in lattice models to discretized spatial slices resembling hyperbolic slices used in AdS/CFT correspondence. Quantum error-correcting interpretations by Daniel Harlow and Patrick Hayden frame bulk locality as protection against boundary noise, while studies by Hugh Osborn and Horacio Casini relate modular Hamiltonians and relative entropy to spacetime dynamics. Connections to Topological quantum field theory and Conformal field theory are emphasized by researchers including Alexander Zamolodchikov and Paul Ginsparg.
Predictions and tests span galactic rotation curves, cosmological observations, and precision tests of gravity. Some emergent proposals, notably by Erik Verlinde, suggest modifications that could mimic Dark matter phenomenology in galactic dynamics, prompting comparisons with empirical programs led by teams at Max Planck Society, European Southern Observatory, Keck Observatory, and Sloan Digital Sky Survey. Cosmological implications interface with work on Cosmic microwave background measurements by WMAP and Planck collaboration teams, and with large-scale structure surveys such as the Dark Energy Survey and LSST (Vera C. Rubin Observatory). Laboratory analogues inspired by William Unruh and experiments at MIT and Caltech use superfluid helium and Bose–Einstein condensates studied by Eric Cornell and Carl Wieman to simulate horizon phenomena, while precision tests of equivalence principles involve groups at LIGO Scientific Collaboration and European Space Agency missions.
Critiques arise from researchers including Clifford Will, Sean Carroll, Juan Maldacena, and Robert Wald who point to challenges in deriving full nonlinear dynamics, reproducing gravitational radiation consistent with LIGO Scientific Collaboration observations, and embedding in a quantum UV-complete framework akin to String theory or Loop quantum gravity. Open problems include identifying microscopic constituents analogous to atoms in Statistical mechanics that yield Lorentz invariance, demonstrating renormalizability or emergence of coupling constants as in Renormalization group flows studied by Kenneth Wilson, and connecting to particle physics frameworks developed at CERN and by the Particle Data Group.
Related ideas include the Holographic principle, AdS/CFT correspondence, Thermodynamics of spacetime, Black hole thermodynamics, Quantum error correction, Tensor networks, Causal set theory, Loop quantum gravity, String theory, Analog gravity, Topological phases of matter, Fractional quantum Hall effect, and Quantum criticality explored by physicists across institutions such as Harvard University, Princeton University, Perimeter Institute, CERN, and Institute for Advanced Study; applications extend to quantum simulation platforms at MIT, Caltech, and University of Cambridge and to astrophysical constraints from observatories like NASA and European Southern Observatory.