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John McGreevy

Bio: John McGreevy is an academic researcher from University of California, San Diego. The author has contributed to research in topics: Gauge theory & String theory. The author has an hindex of 29, co-authored 56 publications receiving 5751 citations. Previous affiliations of John McGreevy include Massachusetts Institute of Technology.


Papers
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TL;DR: This work attempts to generalize the anti-de Sitter/conformal field theory correspondence to nonrelativistic conformal field theories which are invariant under Galilean transformations, and constructs a family of metrics which realize these symmetries as isometries.
Abstract: We attempt to generalize the anti-de Sitter/conformal field theory correspondence to nonrelativistic conformal field theories which are invariant under Galilean transformations. Such systems govern ultracold atoms at unitarity, nucleon scattering in some channels, and, more generally, a family of universality classes of quantum critical behavior. We construct a family of metrics which realize these symmetries as isometries. They are solutions of gravity with a negative cosmological constant coupled to pressureless dust. We discuss realizations of the dust, which include a bulk superconductor. We develop the holographic dictionary and find two-point correlators of the correct form. A strange aspect of the correspondence is that the bulk geometry has two extra noncompact dimensions.

1,010 citations

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TL;DR: In particular, when the operator is marginal in the IR CFT, the corresponding spectral function is precisely of the ''marginal Fermi liquid'' form, postulated to describe the optimally doped cuprates as discussed by the authors.
Abstract: Gravity solutions dual to $d$-dimensional field theories at finite charge density have a near-horizon region, which is ${\mathrm{AdS}}_{2}\ifmmode\times\else\texttimes\fi{}{\mathbb{R}}^{d\ensuremath{-}1}$. The scale invariance of the ${\mathrm{AdS}}_{2}$ region implies that at low energies the dual field theory exhibits emergent quantum critical behavior controlled by a ($0+1$)-dimensional conformal field theories (CFT). This interpretation sheds light on recently-discovered holographic descriptions of Fermi surfaces, allowing an analytic understanding of their low-energy excitations. For example, the scaling behavior near the Fermi surfaces is determined by conformal dimensions in the emergent IR CFT. In particular, when the operator is marginal in the IR CFT, the corresponding spectral function is precisely of the ``marginal Fermi liquid'' form, postulated to describe the optimally doped cuprates.

738 citations

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TL;DR: In this paper, a series of lectures given at the KITP workshop Quantum Criticality and the AdS/CFT Correspondence in July 2009 were described, with the goal of the lectures being to introduce condensed matter physicists to the CFT correspondence.
Abstract: These are notes based on a series of lectures given at the KITP workshop Quantum Criticality and the AdS/CFT Correspondence in July, 2009. The goal of the lectures was to introduce condensed matter physicists to the AdS/CFT correspondence. Discussion of string theory and of supersymmetry is avoided to the extent possible.

635 citations

Journal ArticleDOI
21 Jul 2005
TL;DR: The presence of many axion fields in four-dimensional string vacua can lead to a simple, radiatively stable realization of chaotic inflation as discussed by the authors, which can be seen as an example of the so-called chaotic inflation.
Abstract: The presence of many axion fields in four-dimensional string vacua can lead to a simple, radiatively stable realization of chaotic inflation

620 citations

01 Jan 2010
TL;DR: In this article, a series of lectures given at the KITP workshop Quantum Criticality and the AdS/CFT Correspondence in July 2009 were described, with the goal of the lectures being to introduce condensed matter physicists to the CFT correspondence.
Abstract: These are notes based on a series of lectures given at the KITP workshop Quantum Criticality and the AdS/CFT Correspondence in July, 2009. The goal of the lectures was to introduce condensed matter physicists to the AdS/CFT correspondence. Discussion of string theory and of supersymmetry is avoided to the extent possible.

486 citations


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TL;DR: Topological superconductors are new states of quantum matter which cannot be adiabatically connected to conventional insulators and semiconductors and are characterized by a full insulating gap in the bulk and gapless edge or surface states which are protected by time reversal symmetry.
Abstract: Topological insulators are new states of quantum matter which cannot be adiabatically connected to conventional insulators and semiconductors. They are characterized by a full insulating gap in the bulk and gapless edge or surface states which are protected by time-reversal symmetry. These topological materials have been theoretically predicted and experimentally observed in a variety of systems, including HgTe quantum wells, BiSb alloys, and Bi2Te3 and Bi2Se3 crystals. Theoretical models, materials properties, and experimental results on two-dimensional and three-dimensional topological insulators are reviewed, and both the topological band theory and the topological field theory are discussed. Topological superconductors have a full pairing gap in the bulk and gapless surface states consisting of Majorana fermions. The theory of topological superconductors is reviewed, in close analogy to the theory of topological insulators.

11,092 citations

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TL;DR: In this article, a quantum field theory of gravity with dynamical critical exponent equal to $z = 3$ in the UV is presented. But this theory is restricted to satisfy the condition of detailed balance.
Abstract: We present a candidate quantum field theory of gravity with dynamical critical exponent equal to $z=3$ in the UV. (As in condensed-matter systems, $z$ measures the degree of anisotropy between space and time.) This theory, which at short distances describes interacting nonrelativistic gravitons, is power-counting renormalizable in $3+1$ dimensions. When restricted to satisfy the condition of detailed balance, this theory is intimately related to topologically massive gravity in three dimensions, and the geometry of the Cotton tensor. At long distances, this theory flows naturally to the relativistic value $z=1$, and could therefore serve as a possible candidate for a UV completion of Einstein's general relativity or an infrared modification thereof. The effective speed of light, the Newton constant and the cosmological constant all emerge from relevant deformations of the deeply nonrelativistic $z=3$ theory at short distances.

2,816 citations

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TL;DR: In this article, a discussion of holographic techniques progresses from equilibrium, to transport and to superconductivity, and the discussion of supergravity, Strings and Gauge theories are discussed.
Abstract: These notes are loosely based on lectures given at the CERN Winter School on Supergravity, Strings and Gauge theories, February 2009, and at the IPM String School in Tehran, April 2009. I have focused on a few concrete topics and also on addressing questions that have arisen repeatedly. Background condensed matter physics material is included as motivation and easy reference for the high energy physics community. The discussion of holographic techniques progresses from equilibrium, to transport and to superconductivity.

1,951 citations

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TL;DR: In this paper, an upper bound on the strength of gravity relative to gauge forces in quantum gravity was given, motivated by arguments involving holography and absence of remnants, the stability of black holes as well as the non-existence of global symmetries in string theory.
Abstract: We conjecture a general upper bound on the strength of gravity relative to gauge forces in quantum gravity. This implies, in particular, that in a four-dimensional theory with gravity and a U(1) gauge field with gauge coupling g, there is a new ultraviolet scale Λ = gMPl, invisible to the low-energy effective field theorist, which sets a cutoff on the validity of the effective theory. Moreover, there is some light charged particle with mass smaller than or equal to Λ. The bound is motivated by arguments involving holography and absence of remnants, the (in) stability of black holes as well as the non-existence of global symmetries in string theory. A sharp form of the conjecture is that there are always light ``elementary'' electric and magnetic objects with a mass/charge ratio smaller than the corresponding ratio for macroscopic extremal black holes, allowing extremal black holes to decay. This conjecture is supported by a number of non-trivial examples in string theory. It implies the necessary presence of new physics beneath the Planck scale, not far from the GUT scale, and explains why some apparently natural models of inflation resist an embedding in string theory.

1,424 citations

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TL;DR: A review of quantum spin liquids can be found in this paper, where the authors discuss the nature of such phases and their properties based on paradigmatic models and general arguments, and introduce theoretical technology such as gauge theory and partons that are conveniently used in the study of spin liquids.
Abstract: Quantum spin liquids may be considered "quantum disordered" ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects, such as non-local excitations, topological properties, and more. In this review, we discuss the nature of such phases and their properties based on paradigmatic models and general arguments, and introduce theoretical technology such as gauge theory and partons that are conveniently used in the study of quantum spin liquids. An overview is given of the different types of quantum spin liquids and the models and theories used to describe them. We also provide a guide to the current status of experiments to study quantum spin liquids, and to the diverse probes used therein.

1,339 citations