# The analytic functional bootstrap. Part II. Natural bases for the crossing equation

Authors
• 1 Stony Brook University, C.N. Yang Institute for Theoretical Physics, Stony Brook, NY, 11794, U.S.A. , Stony Brook (United States)
• 2 Stony Brook University, Simons Center for Geometry and Physics, Stony Brook, NY, 11794, U.S.A. , Stony Brook (United States)
• 3 PSL University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Laboratoire de Physique Théorique de l’ École Normale Supérieure, 24 rue Lhomond, Paris Cedex 05, 75231, France , Paris Cedex 05 (France)
Type
Published Article
Journal
Journal of High Energy Physics
Publisher
Springer-Verlag
Publication Date
Feb 25, 2019
Volume
2019
Issue
2
Identifiers
DOI: 10.1007/JHEP02(2019)163
Source
Springer Nature
Keywords
License
Yellow

## Abstract

We clarify the relationships between different approaches to the conformal bootstrap. A central role is played by the so-called extremal functionals. They are linear functionals acting on the crossing equation which are directly responsible for the optimal bounds of the numerical bootstrap. We explain in detail that the extremal functionals probe the Regge limit. We construct two complete sets of extremal functionals for the crossing equation specialized to z=z¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$z=\overline{z}$$\end{document}, associated to the generalized free boson and fermion theories. These functionals lead to non-perturbative sum rules on the CFT data which automatically incorporate Regge boundedness of physical correlators. The sum rules imply universal properties of the OPE at large Δ in every unitary solution of SL(2) crossing. In particular, we prove an upper and lower bound on a weighted sum of OPE coefficients present between consecutive generalized free field dimensions. The lower bound implies the ϕ × ϕ OPE must contain at least one primary in the interval [2Δϕ + 2n, 2Δϕ + 2n + 4] for all sufficiently large integer n. The functionals directly compute the OPE decomposition of crossing-symmetrized Witten exchange diagrams in AdS2. Therefore, they provide a derivation of the Polyakov bootstrap for SL(2), in particular fixing the so-called contact-term ambiguity. We also use the resulting sum rules to bootstrap several Witten diagrams in AdS2 up to two loops.

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