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Gravity, Quantum Fields and Information

The aim of the independent research group “Gravity, Quantum Fields and Information” (GQFI), led by Dr. Michal P. Heller, is to explore the fascinating interplay between general relativity, quantum field theory, and quantum information theory uncovered in recent years, using insights from holography (AdS/CFT), many-body physics, black holes, and more.

Some of the motivating questions for GQFI are:

  • Can we understand the dynamical geometry of spacetime, and hence gravity itself, as an emergent quantum-many body phenomenon, in the spirit of “It from Qubit”? And what role do quantum information concepts such as entanglement and complexity play in this connection?
  • Quantum systems with many constituents are known to be very complex, and require powerful computers to simulate. Can we use new ideas from tensor networks to finding efficient ways to model these systems on a computer?
  • Black holes are the only known objects in nature in which both quantum theory and general relativity are simultaneously relevant, and therefore serve as a true “theorists laboratory” for quantum gravity. Can we use tools from holography and algebraic quantum field theory to shed light on these mysterious objects, and perhaps reveal their interior?

Here are some of the specific research projects currently being pursued by GQFI:

Complexity in quantum field theory

In the context of holography, the quantum information-theoretic notion of “complexity” has been conjectured to encode certain gravitational quantities (particularly those pertaining to the spacetime inside black holes). Members of our group have pioneered the effort to make this idea precise in quantum field theories, and we are continuing the study of this novel quantity in a variety of models [1,2].

Tensor networks

Tensor networks are extremely useful tools for representing certain quantum states, and have interesting geometric properties that have led to fruitful analogies with holography. In particular, the MERA tensor network, which is naturally suited to represent 1D critical systems (described by CFTs), has a 2D negatively curved geometry, and has been conjectured to describe certain aspects of the AdS/CFT correspondence. Can insights from gravity and holography be useful to strengthen this connection, or to design new, more powerful tensor networks for simulating complex quantum systems, e.g., by taking advantage of symmetrical aspects [3]?

Entanglement structure & modular flow

We are investigating the properties of modular (entanglement) Hamiltonians for low dimensional systems [4,5]. In particular, we have focused on understanding the transition from locality to continuous non-locality in the modular flow. This may provide new insights into the problem of bulk reconstruction in holography.

Black hole interiors & the firewall paradox

AdS/CFT provides a particularly useful framework for investigating the firewall paradox [6], a 40 year-old puzzle at the heart of our attempts to unify gravity and quantum theory. We are applying insights from holography and algebraic quantum field theory to shed light on how one can reconstruct the black hole interior, as well as the nascent relationship between entanglement and spacetime geometry [7].

Non-equilibrium dynamics

Quantum dynamics away from equilibrium is relevant to a vast array of problems, including the physics of highly excited primordial nuclear matter described by the strong force, which is reproduced in ultra-energetic collisions of atomic nuclei. AdS/CFT allows us to model these collisions, and has led to many interesting phenomenological lessons in nuclear physics [8]. Beyond holographic methods, we also simulate quantum many-body systems (i.e. spin chains) with tensor networks algorithms in (1+1)D to extract properties of thermal quantum field theory dynamics. We want to understand equilibration in models of quark-gluon plasmas, using ideas at the interface of tensor networks and high-energy physics.

Other activities

The GQFI is engaged in a number of other activities aimed to further collaboration, communication, and general interest in physics. We run a series of weekly virtual seminars---an innovative format that allows us to broadcast a variety of talks from researchers around the world while reducing our carbon footprint. Interested researchers from other groups can tune-in and participate interactively (ask questions, etc), and the talks are subsequently posted to our YouTube channel so that anyone can view them freely, anytime. We also host a topical “GQFI Workshop” twice a year; links to past events can be found on the right side of the page. Additionally, members of our group are engaged in various outreach activities, such as local Science Day events, and a research blog . To keep up with the latest news and developments, check out our Twitter feed!


Most of our group's publications can be found on INSPIRE-HEP.

[1] H. A. Camargo, M. P. Heller, R. Jefferson, J. Knaute, arXiv:1904.02713

[2] H. A. Camargo, P. Caputa, D. Das, M. P. Heller, R. Jefferson, Phys. Rev. Lett. 122, 081601 (2019), arXiv:1807.07075.

[3] S Singh, NA McMahon, and GK Brennen, Physical Review D 97, 026013 (2018),  arXiv:1702.00392.

[4] P. Fries, I. A. Reyes,  arXiv:1905.05768.

[5] P. Fries, I. A. Reyes, arXiv:1906.02207

[6] R. Jefferson, arXiv:1901.01149.

[7] R. Jefferson, SciPost Phys. 6, 042 (2019), arXiv:1811.08900.

[8] W. Florkowski, M. P. Heller, M. Spalinski, Rep. Prog. Phys. 81, 4 (2017), arXiv:1707.02282.

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