scholarly journals CFT in AdS and boundary RG flows

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Simone Giombi ◽  
Himanshu Khanchandani
Keyword(s):  
Free Energy ◽  
Correlation Functions ◽  
Equations Of Motion ◽  
Flat Space ◽  
De Sitter ◽  
Conformal Field ◽  
Anomalous Dimensions ◽  
Epsilon Expansion ◽  
Boundary Operators ◽  
Renormalization Group Flows

Abstract Using the fact that flat space with a boundary is related by a Weyl transformation to anti-de Sitter (AdS) space, one may study observables in boundary conformal field theory (BCFT) by placing a CFT in AdS. In addition to correlation functions of local operators, a quantity of interest is the free energy of the CFT computed on the AdS space with hyperbolic ball metric, i.e. with a spherical boundary. It is natural to expect that the AdS free energy can be used to define a quantity that decreases under boundary renormalization group flows. We test this idea by discussing in detail the case of the large N critical O(N) model in general dimension d, as well as its perturbative descriptions in the epsilon-expansion. Using the AdS approach, we recover the various known boundary critical behaviors of the model, and we compute the free energy for each boundary fixed point, finding results which are consistent with the conjectured F-theorem in a continuous range of dimensions. Finally, we also use the AdS setup to compute correlation functions and extract some of the BCFT data. In particular, we show that using the bulk equations of motion, in conjunction with crossing symmetry, gives an efficient way to constrain bulk two-point functions and extract anomalous dimensions of boundary operators.

scholarly journals Two point functions in defect CFTs

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Christopher P. Herzog ◽  
Abhay Shrestha
Keyword(s):  
Field Theory ◽  
Conformal Field Theory ◽  
Correlation Functions ◽  
Equations Of Motion ◽  
Physical Space ◽  
Arbitrary Spin ◽  
Momentum Tensor ◽  
Maxwell Theory ◽  
Conformal Field ◽  
Point Correlation

Abstract This paper is designed to be a practical tool for constructing and investigating two-point correlation functions in defect conformal field theory, directly in physical space, between any two bulk primaries or between a bulk primary and a defect primary, with arbitrary spin. Although geometrically elegant and ultimately a more powerful approach, the embedding space formalism gets rather cumbersome when dealing with mixed symmetry tensors, especially in the projection to physical space. The results in this paper provide an alternative method for studying two-point correlation functions for a generic d-dimensional conformal field theory with a flat p-dimensional defect and d − p = q co-dimensions. We tabulate some examples of correlation functions involving a conserved current, an energy momentum tensor and a Maxwell field strength, while analysing the constraints arising from conservation and the equations of motion. A method for obtaining bulk-to-defect correlators is also explained. Some explicit examples are considered: free scalar theory on ℝp× (ℝq/ℤ2) and a free four dimensional Maxwell theory on a wedge.

scholarly journals Random boundary geometry and gravity dual of $$ T\overline{T} $$ deformation

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Shinji Hirano ◽  
Masaki Shigemori
Keyword(s):  
Field Theory ◽  
Free Energy ◽  
Energy Spectrum ◽  
Correlation Functions ◽  
Degrees Of Freedom ◽  
Dual Language ◽  
Renormalization Group Flow ◽  
Conformal Field ◽  
Logarithmic Corrections ◽  
Group Flow

Abstract We study the random geometry approach to the $$ T\overline{T} $$ T T ¯ deformation of 2d conformal field theory developed by Cardy and discuss its realization in a gravity dual. In this representation, the gravity dual of the $$ T\overline{T} $$ T T ¯ deformation becomes a straightforward translation of the field theory language. Namely, the dual geometry is an ensemble of AdS3 spaces or BTZ black holes, without a finite cutoff, but instead with randomly fluctuating boundary diffeomorphisms. This reflects an increase in degrees of freedom in the renormalization group flow to the UV by the irrelevant $$ T\overline{T} $$ T T ¯ operator. We streamline the method of computation and calculate the energy spectrum and the thermal free energy in a manner that can be directly translated into the gravity dual language. We further generalize this approach to correlation functions and reproduce the all-order result with universal logarithmic corrections computed by Cardy in a different method. In contrast to earlier proposals, this version of the gravity dual of the $$ T\overline{T} $$ T T ¯ deformation works not only for the energy spectrum and the thermal free energy but also for correlation functions.

Flat space holography

2008 ◽  
Vol 86 (4) ◽  
pp. 563-570
Author(s):  
R B Mann
Keyword(s):  
Field Theory ◽  
Flat Space ◽  
De Sitter ◽  
Spacetime Dimension ◽  
Asymptotically Flat ◽  
Conformal Field ◽  
Recent Developments ◽  
Concrete Realization ◽  
Flat Spacetimes ◽  
Spacelike Infinity

The implementation of holography in gravitational physics has its most concrete realization in the context of the anti-de Sitter/conformal field theory (AdS/CFT) correspondence conjecture, an implication of which is that counterterms from the boundary CFT can be understood as surface terms that render the variational principle finite and well-defined for the gravity theory in the bulk. I discuss recent developments that show how such gravitational counterterms can be deployed for asymptotically flat spacetimes in any spacetime dimension d ≥ 4. These actions yield conserved quantities at spacelike infinity that agree with the usual Arnowitt–Deser–Misner results but are more general. This approach removes the need for ill-defined background subtraction methods and suggests the possibility of obtaining a dual field theory to gravity theories in asymptotically flat spacetimes.PACS Nos.: 04.20.Ha, 04.60.–m, 11.25.Tq

scholarly journals Effective field theory for closed strings near the Hagedorn temperature

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Ram Brustein ◽  
Yoav Zigdon
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Effective Action ◽  
Equations Of Motion ◽  
Flat Space ◽  
Conformal Structure ◽  
Effective Field ◽  
Conformally Invariant ◽  
Conformal Field ◽  
Quartic Interaction

Abstract We discuss interacting, closed, bosonic and superstrings in thermal equilibrium at temperatures close to the Hagedorn temperature in flat space. We calculate S-matrix elements of the strings at the Hagedorn temperature and use them to construct a low-energy effective action for interacting strings near the Hagedorn temperature. We show, in particular, that the four-point amplitude of massless winding modes leads to a positive quartic interaction. Furthermore, the effective field theory has a generalized conformal structure, namely, it is conformally invariant when the temperature is assigned an appropriate scaling dimension. Then, we show that the equations of motion resulting from the effective action possess a winding-mode-condensate background solution above the Hagedorn temperature and present a worldsheet conformal field theory, similar to a Sine-Gordon theory, that corresponds to this solution. We find that the Hagedorn phase transition in our setup is second order, in contrast to a first-order transition that was found previously in different setups.

scholarly journals On the time evolution of cosmological correlators

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Sebastián Céspedes ◽  
Anne-Christine Davis ◽  
Scott Melville
Keyword(s):  
Time Evolution ◽  
Transfer Functions ◽  
Equations Of Motion ◽  
Late Time ◽  
De Sitter ◽  
Initial State ◽  
Conformal Boundary ◽  
Sitter Spacetime ◽  
Boundary Operators ◽  
Simple Equations

Abstract Developing our understanding of how correlations evolve during inflation is crucial if we are to extract information about the early Universe from our late-time observables. To that end, we revisit the time evolution of scalar field correlators on de Sitter spacetime in the Schrödinger picture. By direct manipulation of the Schrödinger equation, we write down simple “equations of motion” for the coefficients which determine the wavefunction. Rather than specify a particular interaction Hamiltonian, we assume only very basic properties (unitarity, de Sitter invariance and locality) to derive general consequences for the wavefunction’s evolution. In particular, we identify a number of “constants of motion” — properties of the initial state which are conserved by any unitary dynamics — and show how this can be used to partially fix the cubic and quartic wavefunction coefficients at weak coupling. We further constrain the time evolution by deriving constraints from the de Sitter isometries and show that these reduce to the familiar conformal Ward identities at late times. Finally, we show how the evolution of a state from the conformal boundary into the bulk can be described via a number of “transfer functions” which are analytic outside the horizon for any local interaction. These objects exhibit divergences for particular values of the scalar mass, and we show how such divergences can be removed by a renormalisation of the boundary wavefunction — this is equivalent to performing a “Boundary Operator Expansion” which expresses the bulk operators in terms of regulated boundary operators. Altogether, this improved understanding of the wavefunction in the bulk of de Sitter complements recent advances from a purely boundary perspective, and reveals new structure in cosmological correlators.

HOLOGRAMS OF FLAT SPACE

2013 ◽  
Vol 22 (12) ◽  
pp. 1342003 ◽  
Author(s):  
ARJUN BAGCHI ◽  
DANIEL GRUMILLER
Keyword(s):  
Field Theory ◽  
Three Dimensional ◽  
Flat Space ◽  
De Sitter ◽  
Conformal Field ◽  
Gravitational Theories ◽  
Concrete Realization ◽  
Flat Spacetimes ◽  
Space Boundary ◽  
Chern Simons

The holographic principle has a concrete realization in the Anti-de Sitter/Conformal Field Theory (AdS/CFT) correspondence. If this principle is a true fact about quantum gravity then it must also hold beyond AdS/CFT. In this paper, we address specifically holographic field theory duals of gravitational theories in asymptotically flat spacetimes. We present some evidence of our recent conjecture that three-dimensional (3d) conformal Chern–Simons gravity (CSG) with flat space boundary conditions is dual to an extremal CFT.

scholarly journals Helicity basis for three-dimensional conformal field theory

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Simon Caron-Huot ◽  
Yue-Zhou Li
Keyword(s):  
Conformal Symmetry ◽  
Mean Field ◽  
Three Dimensional ◽  
Flat Space ◽  
Three Dimensions ◽  
Tree Level ◽  
Conformal Field ◽  
Anomalous Dimensions ◽  
Conserved Currents ◽  
Level Order

Abstract Three-point correlators of spinning operators admit multiple tensor structures compatible with conformal symmetry. For conserved currents in three dimensions, we point out that helicity commutes with conformal transformations and we use this to construct three-point structures which diagonalize helicity. In this helicity basis, OPE data is found to be diagonal for mean-field correlators of conserved currents and stress tensor. Furthermore, we use Lorentzian inversion formula to obtain anomalous dimensions for conserved currents at bulk tree-level order in holographic theories, which we compare with corresponding flat-space gluon scattering amplitudes.

scholarly journals Comments on contact terms and conformal manifolds in the AdS/CFT correspondence

2020 ◽  
Author(s):  
Tadakatsu Sakai ◽  
Masashi Zenkai
Keyword(s):  
Fixed Point ◽  
Correlation Functions ◽  
Equations Of Motion ◽  
Mathematical Structure ◽  
Regularization Scheme ◽  
Anomalous Dimensions ◽  
Geometrical Data ◽  
Conformal Manifolds ◽  
General Setup ◽  
Marginal Deformation

Abstract We study the contact terms that appear in the correlation functions of exactly marginal operators using the AdS/CFT correspondence. It is known that CFT with an exactly marginal deformation requires the existence of the contact terms is crucial for a consistency of with their coefficients having a geometrical interpretation in the context of conformal manifolds. We show that the AdS/CFT correspondence captures properly the mathematical structure of the correlation functions that is expected from the CFT analysis. For this purpose, we employ holographic RG to formulate a most general setup in the bulk for describing an exactly marginal deformation. The resultant bulk equations of motion are nonlinear and solved perturbatively to obtain the on-shell action. We compute three- and four-point functions of the exactly marginal operators using the GKP-Witten prescription, and show that they match with the expected results precisely. It is pointed out that The cut-off surface prescription in the bulk provides us with a regularization scheme for performing a conformal perturbation. serves as a regularization scheme for conformal perturbation theory in the boundary CFT. around a fixed point is regularized by putting a cut-off surface in the bulk. As an application, we examine a double OPE limit of the four-point functions. The anomalous dimensions of double trace operators are written in terms of the geometrical data of a conformal manifold.

scholarly journals Relation between parity-even and parity-odd CFT correlation functions in three dimensions

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Sachin Jain ◽  
Renjan Rajan John
Keyword(s):  
Scattering Amplitudes ◽  
Correlation Functions ◽  
Flat Space ◽  
Three Dimensions ◽  
Higher Dimension ◽  
De Sitter ◽  
Higher Spin ◽  
Space Limit ◽  
Point Correlation

Abstract In this paper we relate the parity-odd part of two and three point correlation functions in theories with exactly conserved or weakly broken higher spin symmetries to the parity-even part which can be computed from free theories. We also comment on higher point functions.The well known connection of CFT correlation functions with de-Sitter amplitudes in one higher dimension implies a relation between parity-even and parity-odd amplitudes calculated using non-minimal interactions such as $$ {\mathcal{W}}^3 $$ W 3 and $$ {\mathcal{W}}^2\tilde{\mathcal{W}} $$ W 2 W ˜ . In the flat-space limit this implies a relation between parity-even and parity-odd parts of flat-space scattering amplitudes.

scholarly journals LIOUVILLE THEORY AND LOGARITHMIC SOLUTIONS TO KNIZHNIK–ZAMOLODCHIKOV EQUATION

2005 ◽  
Vol 20 (20n21) ◽  
pp. 4821-4862 ◽  
Author(s):  
GASTÓN GIRIBET ◽  
CLAUDIO SIMEONE
Keyword(s):  
Correlation Functions ◽  
Three Dimensional ◽  
Liouville Theory ◽  
Operator Product ◽  
De Sitter ◽  
Conformal Field ◽  
Point Correlation ◽  
Symmetry Transformations ◽  
Logarithmic Singularities ◽  
Zamolodchikov Equation

We study a class of solutions to the SL (2, ℝ)k Knizhnik–Zamolodchikov equation. First, logarithmic solutions which represent four-point correlation functions describing string scattering processes on three-dimensional anti-de Sitter space are discussed. These solutions satisfy the factorization ansatz and include logarithmic dependence on the SL (2, ℝ)-isospin variables. Different types of logarithmic singularities arising are classified and the interpretation of these is discussed. The logarithms found here fit into the usual pattern of the structure of four-point function of other examples of AdS/CFT correspondence. Composite states arising in the intermediate channels can be identified as the phenomena responsible for the appearance of such singularities in the four-point correlation functions. In addition, logarithmic solutions which are related to nonperturbative (finite k) effects are found. By means of the relation existing between four-point functions in Wess–Zumino–Novikov–Witten model formulated on SL (2, ℝ) and certain five-point functions in Liouville quantum conformal field theory, we show how the reflection symmetry of Liouville theory induces particular ℤ2 symmetry transformations on the WZNW correlators. This observation allows to find relations between different logarithmic solutions. This Liouville description also provides a natural explanation for the appearance of the logarithmic singularities in terms of the operator product expansion between degenerate and puncture fields.

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