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Juan M. Maldacena

Publications and source records attributed to Juan M. Maldacena.

At least 19 recordsLinked to original sources
arXiv2011

On graviton non-Gaussianities during inflation

We consider the most general three point function for gravitational waves produced during a period of exactly de Sitter expansion. The de Sitter isometries constrain the possible shapes to only three: two preserving parity and one violating parity. These isometries imply that these correlation functions should be conformal invariant. One of the shapes is produced by the ordinary gravity action. The other shape is produced by a higher derivative correction and could be as large as the gravity contribution. The parity violating shape does not contribute to the bispectrum [1106.3228, 1108.0175], even though it is present in the wavefunction. We also introduce a spinor helicity formalism to describe de Sitter gravitational waves with circular polarization. These results also apply to correlation functions in Anti-de Sitter space. They also describe the general form of stress tensor correlation functions, in momentum space, in a three dimensional conformal field theory. Here all three shapes can arise, including the parity violating one.

hep-th↗
arXiv2004

Superconformal Gauge Theories and Non-Critical Superstrings

We consider effective actions for six-dimensional non-critical superstrings. We show that the addition of $N$ units of R-R flux and of $N_f$ space-time filling D5-branes produces $AdS_5 \times S^1$ solutions with curvature comparable to the string scale. These solutions have the right structure to be dual to ${\cal N}=1$ supersymmetric SU(N) gauge theories with $N_f$ flavors. We further suggest bounds on the mass-squared of tachyonic fields in this background that should restrict the theory to the conformal window.

hep-th↗
arXiv2004

Brane Dynamics From the Born-Infeld Action

We use the abelian Born-Infeld action for the worldvolume gauge field and transverse displacement scalars to explore new aspects of D-brane structure and dynamics. We study several classic gauge field configurations, including point charges in any worldvolume dimension and vortices in two worldvolume dimensions, and show that, with an appropriate excitation of the transverse coordinate field, they are BPS-saturated solutions. The Coulomb point charge solutions turn out to represent, with considerable fidelity, fundamental strings attached to the brane (their magnetic counterparts describe D1-branes attached to D3-branes). We also show that S-matrix for small excitations propagating on the point charge solution is consistent with (and gives further illuminating information about) Polchinski's effective open string boundary condition.

hep-th↗
arXiv2003

Exact Solution of a Boundary Conformal Field Theory

We study the conformal field theory of a free massless scalar field living on the half line with interactions introduced via a periodic potential at the boundary. An SU(2) current algebra underlies this system and the interacting boundary state is given by a global SU(2) rotation of the left-moving fields in the zero-potential (Neumann) boundary state. As the potential strength varies from zero to infinity, the boundary state interpolates between the Neumann and the Dirichlet values. The full S-matrix for scattering from the boundary, with arbitrary particle production, is explicitly computed. To maintain unitarity, it is necessary to attribute a hidden discrete ``soliton'' degree of freedom to the boundary. The same unitarity puzzle occurs in the Kondo problem, and we anticipate a similar solution.

hep-th↗
arXiv2001

Eternal Black Holes in AdS

We propose a dual non-perturbative description for maximally extended Schwarzschild Anti-de-Sitter spacetimes. The description involves two copies of the conformal field theory associated to the AdS spacetime and an initial entangled state. In this context we also discuss a version of the information loss paradox and its resolution.

hep-th↗
arXiv2000

Supergravity and The Large N Limit of Theories With Sixteen Supercharges

We consider field theories with sixteen supersymmetries, which includes U(N) Yang-Mills theories in various dimensions, and argue that their large N limit is related to certain supergravity solutions. We study this by considering a system of D-branes in string theory and then taking a limit where the brane worldvolume theory decouples from gravity. At the same time we study the corresponding D-brane supergravity solution and argue that we can trust it in certain regions where the curvature (and the effective string coupling, where appropriate) are small. The supergravity solutions typically have several weakly coupled regions and interpolate between different limits of string-M-theory.

hep-th↗
arXiv2000

Towards the large N limit of pure N=1 super Yang Mills

We find the gravity solution corresponding to a large number of NS or D fivebranes wrapped on a two sphere so that we have pure ${\cal N}=1$ super Yang-Mills in the IR. The supergravity solution is smooth, it shows confinement and it breaks the $U(1)_R$ chiral symmetry in the appropriate way. When the gravity approximation is valid the masses of glueballs are comparable to the masses of Kaluza Klein states on the fivebrane, but if we could quantize strings on this background it looks like we should be able to decouple the KK states.

hep-th↗
arXiv2000

Large N Limit of Non-Commutative Gauge Theories

Using the correspondence between gauge theories and string theory in curved backgrounds, we investigate aspects of the large $N$ limit of non-commutative gauge theories by considering gravity solutions with $B$ fields. We argue that the total number of physical degrees of freedom at any given scale coincides with the commutative case. We then compute a two-point correlation function involving momentum components in the directions of the $B$-field. In the UV regime, we find that the two-point function decays exponentially with the momentum. A calculation of Wilson lines suggests that strings cannot be localized near the boundary. We also find string configurations that are localized in a finite region of the radial direction. These are worldsheet instantons.

hep-th↗
arXiv1998

Probing Near Extremal Black Holes with D-branes

We calculate the one loop effective action for D-brane probes moving in the presence of near BPS D-branes. The $v^2$ term agrees with supergravity in all cases and the static force agrees for a five dimensional black hole with two large charges. It also agrees qualitatively in all the other cases. We make some comments on the M(atrix) theory interpretation of these results.

hep-th↗
arXiv1998

Wilson loops in large N field theories

We propose a method to calculate the expectation values of an operator similar to the Wilson loop in the large N limit of field theories. We consider N=4 3+1 dimensional super-Yang-Mills. The prescription involves calculating the area of a fundamental string worldsheet in certain supergravity backgrounds. We also consider the case of coincident M-theory fivebranes where one is lead to calculating the area of M-theory two-branes. We briefly discuss the computation for 2+1 dimensional super-Yang-Mills with sixteen supercharges which is non-conformal. In all these cases we calculate the energy of quark-antiquark pair.

hep-th↗
arXiv1998

Statistical Entropy of De Sitter Space

Quantum gravity in 2+1 dimensions with a positive cosmological constant can be represented as an SL(2,C) Chern-Simons gauge theory. The symmetric vacuum of this theory is a degenerate configuration for which the gauge fields and spacetime metric vanish, while de Sitter space corresponds to a highly excited thermal state. Carlip's approach to black hole entropy can be adapted in this context to determine the statistical entropy of de Sitter space. We find that it equals one-quarter the area of the de Sitter horizon, in agreement with the semiclassical formula.

gr-qc↗
arXiv1998

The Large N Limit of Superconformal Field Theories and Supergravity

We show that the large $N$ limit of certain conformal field theories in various dimensions include in their Hilbert space a sector describing supergravity on the product of Anti-deSitter spacetimes, spheres and other compact manifolds. This is shown by taking some branes in the full M/string theory and then taking a low energy limit where the field theory on the brane decouples from the bulk. We observe that, in this limit, we can still trust the near horizon geometry for large $N$. The enhanced supersymmetries of the near horizon geometry correspond to the extra supersymmetry generators present in the superconformal group (as opposed to just the super-Poincare group). The 't Hooft limit of 4-d ${\cal N} =4$ super-Yang-Mills at the conformal point is shown to contain strings: they are IIB strings. We conjecture that compactifications of M/string theory on various Anti-deSitter spacetimes are dual to various conformal field theories. This leads to a new proposal for a definition of M-theory which could be extended to include five non-compact dimensions.

hep-th↗
arXiv1997

Branes probing black holes

We consider a brane moving close to a large number of coincident branes. We compare the calculation of the effective action using the gauge theory living on the brane and the calculation using the supergravity approximation. We discuss some general features about the correspondence between large N gauge theories and black holes. Then we do a one loop calculation which applies for extremal and near extremal black holes. We comment on the expected results for higher loop calculations. We make some comments on the Matrix theory interpretation of these results.

hep-th↗
arXiv1997

Semiclassical decay of near extremal fivebranes

We argue that a near-extremal charge-$k$ type II NS fivebrane can be reliably described in semiclassical string perturbation theory as long as both $k$ and $μ\over k$ are large, where $μ$ is the energy density in string units. For a small value of the asymptotic string coupling $g$, the dynamics in the throat surrounding the fivebrane reduces to the CGHS model with massive fields. We find that the energy density leaks off the brane in the form of Hawking radiation at a rate of order $1 \over k^{7/2}$ in string units independently of $g$ to leading order. In the $g\to 0$ limit the radiation persists but never reaches asymptotic infinity because the throat becomes infinitely long.

hep-th↗
arXiv1997

Branes, central charges and U-duality invariant BPS conditions

In extended supergravity theories there are $p$-brane solutions preserving different numbers of supersymmetries, depending on the charges, the spacetime dimension and the number of original supersymmetries (8, 16 or 32). We find U-duality invariant conditions on the quantized charges which specify the number of supersymmetries preserved with a particular charge configuration. These conditions relate U-duality invariants to the picture of intersecting branes. The analysis is carried out for all extended supergravities with 16 or 32 supersymmetries in various dimensions.

hep-th↗
arXiv1997

Black Holes and D-branes

D-branes have been used to describe many properties of extremal and near extremal black holes. These lecture notes provide a short review of these developments.

hep-th↗
arXiv1997

Universal Low-Energy Dynamics for Rotating Black Holes

Fundamental string theory has been used to show that low energy excitations of certain black holes are described by a two dimensional conformal field theory. This picture has been found to be extremely robust. In this paper it is argued that many essential features of the low energy effective theory can be inferred directly from a semiclassical analysis of the general Kerr-Newman solution of supersymmetric four-dimensional Einstein-Maxwell gravity, without using string theory. We consider the absorption and emission of scalars with orbital angular momentum, which provide a sensitive probe of the black hole. We find that the semiclassical emission rates -including superradiant emission and greybody factors - for such scalars agree in striking detail with those computed in the effective conformal field theory, in both four and five dimensions. Also the value of the quantum mass gap to the lowest-lying excitation of a charge-$Q$ black hole, $E_{gap}=1/8Q^3$ in Planck units, can be derived without knowledge of fundamental string theory.

hep-th↗