Conformal Bootstrap in Three Dimensions?

Critical Ising Model in Varying Dimension by Conformal Bootstrap

The single-correlator conformal bootstrap is solved numerically for several values of dimension 4>d>2 using the available SDPB and Extremal Functional methods. Critical exponents and other conformal data of low-lying states are obtained over the entire range of dimensions with up to four-decimal precision and then compared with several existing results. The conformal dimensions of leading-twist fields are also determined up to high spin, and their d-dependence shows how the conformal states rearrange themselves around d=2.2 for matching the Virasoro conformal blocks in the d=2 limit. The decou…

Snowmass White Paper: The Numerical Conformal Bootstrap

We give a brief overview of the status of the numerical conformal bootstrap.

TASI Lectures on the Conformal Bootstrap

These notes are from courses given at TASI and the Advanced Strings School in summer 2015. Starting from principles of quantum field theory and the assumption of a traceless stress tensor, we develop the basics of conformal field theory, including conformal Ward identities, radial quantization, reflection positivity, the operator product expansion, and conformal blocks. We end with an introduction to numerical bootstrap methods, focusing on the 2d and 3d Ising models.

具有相互作用边界的 $O(N)$ 边界共形场论的解析自举

Analytic Bootstrap for $O(N)$ Boundary Conformal Field Theories with Interacting Boundaries

利用解析自举和微扰重整化群分析，研究 $d=4-\varepsilon$ 和 $d=3-\varepsilon$ 中具有边界相互作用的 $O(N)$ 边界共形场论，发现新的边界固定点并首次提取三临界 $O(N)$ 模型的边界共形数据。

Conformal Bootstrap Signatures of the Tricritical Ising Universality Class

We study the tricritical Ising universality class using conformal bootstrap techniques. By studying bootstrap constraints originating from multiple correlators on the CFT data of multiple OPEs, we are able to determine the scaling dimension of the spin field $Δ_σ$ in various non-integer dimensions $2 \le d \le 3$. $Δ_σ$ is connected to the critical exponent $η$ that governs the (tri-)critical behaviour of the two point function via the relation, $η= 2 - d + 2 Δ_σ$. Our results for $Δ_σ$ match with the exactly known values in two and three dimensions and are a conjecture for non-integer dimensi…

Inverse Bootstrapping Conformal Field Theories

We propose a novel approach to study conformal field theories (CFTs) in general dimensions. In the conformal bootstrap program, one usually searches for consistent CFT data that satisfy crossing symmetry. In the new approach, we reverse the logic and interpret manifestly crossing-symmetric functions as generating functions of conformal data. Physical CFTs can be obtained by scanning the space of symmetric functions. By truncating the fusion rules, we are able to concentrate on the low-lying operators and derive some approximate relations for their conformal data. It turns out that the free sca…

Positive geometry in the diagonal limit of the conformal bootstrap

We consider the diagonal limit of the conformal bootstrap in arbitrary dimensions and investigate the question if physical theories are given in terms of cyclic polytopes. Recently, it has been pointed out that in $d=1$, the geometric understanding of the bootstrap equations for unitary theories leads to cyclic polytopes for which the faces can all be written down and, in principle, the intersection between the unitarity polytope and the crossing plane can be systematically explored. We find that in higher dimensions, the natural structure that emerges, due to the inclusion of spin, is the wei…

Conformal Bootstrap in Embedding Space

It is shown how to obtain conformal blocks from embedding space with the help of the operator product expansion. The minimal conformal block originates from scalar exchange in a four-point correlation functions of four scalars. All remaining conformal blocks are simple derivatives of the minimal conformal block. With the help of the orthogonality properties of the conformal blocks, the analytic conformal bootstrap can be implemented directly in embedding space, leading to a Jacobi-like definition of conformal field theories.

数值共形自举的新进展

New Developments in the Numerical Conformal Bootstrap

本文综述了数值共形自举领域近5年的软件与算法新进展，以及基于这些新技术取得的主要物理应用成果，补充了2018年综述后的最新发展。

"Old" Conformal Bootstrap on AdS: $O(N)$ symmetric scalar model

Bootstrap equations for conformal correlators that mimic the early theory of conformal bootstrap are written down in frames of the AdS/CFT approach. The simplified version of these equations, that may be justified if Schwinger-Keldysh formalism is used in AdS/CFT instead of conventional Feynman-Witten diagrams technique, permits to calculate values of conformal dimensions in the $O(N)$ symmetric model with conformal or composite Hubbard-Stratonovich field.

Bootstrapping critical Ising model on three-dimensional real projective space

Given a conformal data on a flat Euclidean space, we use crosscap conformal bootstrap equations to numerically solve the Lee-Yang model as well as the critical Ising model on a three-dimensional real projective space. We check the rapid convergence of our bootstrap program in two-dimensions from the exact solutions available. Based on the comparison, we estimate that our systematic error on the numerically solved one-point functions of the critical Ising model on a three-dimensional real projective space is less than one percent. Our method opens up a novel way to solve conformal field theorie…

PCT Theorem, Wightman Axioms and Conformal Bootstrap

The axiomatic Wightman formulation for nonderivative conformal field theory is adopted to derive conformal bootstrap equation for the four point function. The equivalence between PCT theorem and {\it weak local commutativity}, due to Jost, play a very crucial role in axiomatic field theory. The theorem is suitably adopted for conformal field theory to derive the desired equations in CFT. We demonstrate that the two Wightman functions are analytic continuation of each other.

The Analytic Functional Bootstrap I: 1D CFTs and 2D S-Matrices

We study a general class of functionals providing an analytic handle on the conformal bootstrap equations in one dimension. We explicitly identify the extremal functionals, corresponding to theories saturating conformal bootstrap bounds, in two regimes. The first corresponds to functionals that annihilate the generalized free fermion spectrum. In this case, we analytically find both OPE and gap maximization functionals proving the extremality of the generalized free fermion solution to crossing. Secondly, we consider a scaling limit where all conformal dimensions become large, equivalent to th…

Numerical Methods in the Conformal Bootstrap

We present a low entry-level introduction to the Conformal Bootstrap. We review and obtain several basic bounds using Linear Programming in machine precision in Mathematica, making the results accessible even to the most uneducated computer user. The Extremal Functional Method and the method of determinants are also explored. Finally, we make an attempt at writing modular invariance statements as crossing symmetry equations for twist operators and perform Modular Bootstrap using 4-pt correlators.

The old conformal bootstrap revisited

The "old" conformal bootstrap was originally formulated by Migdal and Polyakov (MP) as a method for calculating conformal dimensions self-consistently. In this work we revisit the MP bootstrap and apply efficient multi-loop Feynman integral techniques in order to solve the corresponding equations. We obtain solutions at first order in the skeleton expansion for finite coupling and for integer values of the spacetime dimension. We focus in particular on the $ϕ^3$ theory in seven dimensions and the $O(N)$ vector models in three dimensions.

Quantum algorithms for conformal bootstrap

With the help of recent developments in quantum algorithms for semidefinite programming, we discuss the possibility for quantum speedup for the numerical conformal bootstrap in conformal field theory. We show that quantum algorithms may have significant improvement in the computational performance for several numerical bootstrap problems.

Solving the 3D Ising Model with the Conformal Bootstrap

We study the constraints of crossing symmetry and unitarity in general 3D Conformal Field Theories. In doing so we derive new results for conformal blocks appearing in four-point functions of scalars and present an efficient method for their computation in arbitrary space-time dimension. Comparing the resulting bounds on operator dimensions and OPE coefficients in 3D to known results, we find that the 3D Ising model lies at a corner point on the boundary of the allowed parameter space. We also derive general upper bounds on the dimensions of higher spin operators, relevant in the context of th…

Navigator Function for the Conformal Bootstrap

Current numerical conformal bootstrap techniques carve out islands in theory space by repeatedly checking whether points are allowed or excluded. We propose a new method for searching theory space that replaces the binary information "allowed"/"excluded" with a continuous "navigator" function that is negative in the allowed region and positive in the excluded region. Such a navigator function allows one to efficiently explore high-dimensional parameter spaces and smoothly sail towards any islands they may contain. The specific functions we introduce have several attractive features: they are e…

On the conformal bootstrap for SL(2,R)-WZNW models

This paper has been withdrawn. A more satisfactory account of the results it was supposed to present will appear in a series of papers starting with hep-th/9712256 and hep-th/9712258

共形自举：从Polyakov时代到当代

Conformal bootstrap: from Polyakov to our times

本文梳理共形自举从Polyakov时期至今的发展历程，回顾不同阶段的关键研究、团队成果与技术突破，总结现存挑战并强调共形不变性的物理本质。

Bootstrapping (D, D) Conformal Matter

We use the numerical conformal bootstrap to study six-dimensional $\mathcal{N}=(1,0)$ superconformal field theories with flavor symmetry $\mathfrak{so}_{4k}$. We present evidence that minimal $(D_k, D_k)$ conformal matter saturates the unitarity bounds for arbitrary $k$. Furthermore, using the extremal-functional method, we check that the chiral-ring relations are correctly reproduced, extract the anomalous dimensions of low-lying long superconformal multiplets, and find hints for novel OPE selection rules involving type-$\mathcal{B}$ multiplets.

Critical exponents of the 3d Ising and related models from Conformal Bootstrap

The constraints of conformal bootstrap are applied to investigate a set of conformal field theories in various dimensions. The prescriptions can be applied to both unitary and non unitary theories allowing for the study of the spectrum of low-lying primary operators of the theory. We evaluate the lowest scaling dimensions of the local operators associated with the Yang-Lee edge singularity for $2 \le D \le 6$. Likewise we obtain the scaling dimensions of six scalars and four spinning operators for the 3d critical Ising model. Our findings are in agreement with existing results to a per mill pr…

O(1/N^3) Conformal Bootstrap Solution of the SU(2) x SU(2) Nambu--Jona-Lasinio Model

Using the full conformal bootstrap method an analytic expression is given in d-dimensions for the anomalous dimension of the fermion at O(1/N^3) in a large N expansion of the Nambu--Jona-Lasinio model with SU(2) x SU(2) continuous chiral symmetry.

The extraordinary boundary transition in the 3d O(N) model via conformal bootstrap

This paper studies the critical behavior of the 3d classical $\mathrm{O}(N)$ model with a boundary. Recently, one of us established that upon treating $N$ as a continuous variable, there exists a critical value $N_c > 2$ such that for $2 \leq N < N_c$ the model exhibits a new extraordinary-log boundary universality class, if the symmetry preserving interactions on the boundary are enhanced. $N_c$ is determined by a ratio of universal amplitudes in the normal universality class, where instead a symmetry breaking field is applied on the boundary. We study the normal universality class using the …

$ϕ^3$ theory with $F_4$ flavor symmetry in $6-2ε$ dimensions: 3-loop renormalization and conformal bootstrap

We consider $ϕ^3$ theory in $6-2ε$ with $F_4$ global symmetry. The beta function is calculated up to 3 loops, and a stable unitary IR fixed point is observed. The anomalous dimensions of operators quadratic or cubic in $ϕ$ are also computed. We then employ conformal bootstrap technique to study the fixed point predicted from the perturbative approach. For each putative scaling dimension of $ϕ$ ($Δ_ϕ)$, we obtain the corresponding upper bound on the scaling dimension of the second lowest scalar primary in the ${\mathbf 26}$ representation $(Δ^{\rm 2nd}_{\mathbf 26})$ which appears in the OPE of…

Bootstrapping Conformal Field Theories with the Extremal Functional Method

The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and OPE coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the Extremal Functional Method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying …

Two applications of the analytic conformal bootstrap: A quick tour guide

We review the recent developments in the study of conformal field theories in generic space time dimensions using the methods of the conformal bootstrap, in its analytic aspect. These techniques are based solely on symmetries, in particular in the analytic structure and in the associativity of the operator product expansion. We focus on two applications of the analytic conformal bootstrap: the study of the $ε$ expansion of the Wilson Fisher model via the introduction of a dispersion relation and the large $N$ expansion of maximally supersymmetric Super Yang Mills theory in four dimensions.

"Old" Conformal Bootstrap in the AdS/CFT Context

The Schwinger-Dyson equations for Green functions and 3-vertexes in planar approximation used 50 years ago in the earlier theory of conformal bootstrap are written in frames of the AdS/CFT correspondence. The technique of "Wightman-Witten" diagrams is used in calculations of the bubble bulk diagrams that permitted to obtain the values of conformal dimensions of primary operators in two models of the interacting bulk scalar fields which conformal dimensions obey "extremal" relation. Simple expressions for the four-point tree "Wightman-Witten" correlators of these primary operators are obtained …

评 S. R. Kousvos 与 A. Stergiou 的“共形引导中的冗余通道”

Comment on "Redundancy Channels in the Conformal Bootstrap" by S. R. Kousvos and A. Stergiou

本文回应 Kousvos 和 Stergiou 的批评，论证在微扰重整化群中识别仅相差接触项的算符是正确且更优的做法，因为 CFT 只描述重合点之外的关联函数，无需重整化最终被丢弃的接触项。

(No) Bootstrap for the Fractal Ising Model

We consider the conformal bootstrap for spacetime dimension $1<d<2$. We determine bounds on operator dimensions and compare our results with various theoretical and numerical models, in particular with resummed $ε$-expansion and Monte Carlo simulations of the Ising model on fractal lattices. The bounds clearly rule out that these models correspond to unitary conformal field theories. We also clarify the $d\to 1$ limit of the conformal bootstrap, showing that bounds can be - and indeed are - discontinuous in this limit. This discontinuity implies that for small $ε=d-1$ the expected critical exp…

Conformal bootstrap for percolation and polymers

The conformal bootstrap is applied to percolation and dilute self-avoiding polymers, two theories with Virasoro central charge $c=0$ in two dimensions. In both cases we propose a spectrum of operators motivated by Virasoro symmetry which is devoid of a stress energy tensor as an approximate means of enforcing $c=0$. Percolation is treated in $2\leq D \leq 6$ dimensions, and the self-avoiding walk in $2 \leq D \leq 4$.

Bootstrap experiments on higher dimensional CFTs

Recent programs on conformal bootstrap suggest an empirical relationship between the existence of non-trivial conformal field theories and non-trivial features such as a kink in the unitarity bound of conformal dimensions in the conformal bootstrap equations. We report the existene of non-trivial kinks in the unitarity bound of scalar operators in the adjoint representation of the $SU(N)$ symmetric conformal field theories. They have interesting properties (1) the kinks exist in $d<6$ dimensions (2) the location of kinks are when the unitarity bound hits the space-time dimension $d$ (3) there …

三临界伊辛共形场论与共形引导法

The tricritical Ising CFT and conformal bootstrap

研究三临界伊辛共形场论，通过数值共形引导法，利用含三个外场的混合系统，在特定维度找到与理论插值一致的“引导岛”，在另一些维度设置不足以分离理论，还包含微扰谱综述及文献结果回顾。

PyCFTBoot：共形bootstrap的灵活接口

PyCFTBoot: A flexible interface for the conformal bootstrap

本文介绍了PyCFTBoot，一个降低共形bootstrap计算门槛的wrapper，它利用Symengine和SDPB处理符号与数值步骤，并通过示例验证了其可用性及在多关联函数bootstrap中的应用。

Cut-touching linear functionals in the conformal bootstrap

The modern conformal bootstrap program often employs the method of linear functionals to derive the numerical or analytical bounds on the CFT data. These functionals must have a crucial "swapping" property, allowing to swap infinite summation with the action of the functional in the conformal bootstrap sum rule. Swapping is easy to justify for the popular functionals involving finite sums of derivatives. However, it is far from obvious for "cut-touching" functionals, involving integration over regions where conformal block decomposition does not converge uniformly. Functionals of this type wer…

On Galilean conformal bootstrap

In this work, we develop conformal bootstrap for Galilean conformal field theory (GCFT). In a GCFT, the Hilbert space could be decomposed into quasiprimary states and its global descendants. Different from the usual conformal field theory, the quasi-primary states in a GCFT constitute multiplets, which are block-diagonized under the Galilean boost operator. More importantly the multiplets include the states of negative norms, indicating the theory is not unitary. We compute global blocks of the multiplets, and discuss the expansion of four-point functions in terms of the global blocks of the m…

共形线缺陷端点自举的开端

The beginning of the endpoint bootstrap for conformal line defects

本文首次将数值自举方法扩展到共形线缺陷的端点，利用新的交叉对称关系研究三维伊辛CFT的钉扎场缺陷，所得数据与模糊球方法一致，并证明对称缺陷的不稳定性。

Snowmass White Paper: The Analytic Conformal Bootstrap

The analytic conformal bootstrap is an array of techniques to characterize, constrain, and solve strongly interacting quantum field theories using symmetries, causality, unitarity, and other general principles. In the last decade, bolstered by the development of new Lorentzian methods, it has been used to solve conformal field theories at large spin; to place bounds on energy distributions, event shapes, operator product coefficients, and other observables; and to understand aspects of quantum gravity in anti-de Sitter space. We review these advances and highlight several promising areas for f…

Selected Topics in Analytic Conformal Bootstrap: A Guided Journey

This review aims to offer a pedagogical introduction to the analytic conformal bootstrap program via a journey through selected topics. We review analytic methods which include the large spin perturbation theory, Mellin space methods and the Lorentzian inversion formula. These techniques are applied to a variety of topics ranging from large-N theories, to the epsilon expansion and holographic superconformal correlators, and are demonstrated in a large number of explicit examples.

A conformal bootstrap approach to critical percolation in two dimensions

We study four-point functions of critical percolation in two dimensions, and more generally of the Potts model. We propose an exact ansatz for the spectrum: an infinite, discrete and non-diagonal combination of representations of the Virasoro algebra. Based on this ansatz, we compute four-point functions using a numerical conformal bootstrap approach. The results agree with Monte-Carlo computations of connectivities of random clusters.

Analytic Bootstrap for Perturbative Conformal Field Theories

Conformal field theories play a central role in theoretical physics with many applications ranging from condensed matter to string theory. The conformal bootstrap studies conformal field theories using mathematical consistency conditions and has seen great progress over the last decade. In this thesis we present an implementation of analytic bootstrap methods for perturbative conformal field theories in dimensions greater than two, which we achieve by combining large spin perturbation theory with the Lorentzian inversion formula. In the presence of a small expansion parameter, not necessarily …

共形自举中的冗余通道

Redundancy Channels in the Conformal Bootstrap

提出一种在数值共形自举计算中阻碍对称性增强的方法，通过施加冗余算子的谱间隙来区分低对称性理论与高对称性理论，并应用于三维中区分立方模型与O(3)模型。

使用解析泛函与外部逼近的数值共形bootstrap

Numerical Conformal bootstrap with Analytic Functionals and Outer Approximation

本文通过解析泛函与外部逼近方法在任意时空维度实现数值共形bootstrap，发现其性能优于传统导数方法，并在二维标量通道中识别出新的kinks，为共形bootstrap应用提供了潜在替代范式。

Locality, bulk equations of motion and the conformal bootstrap

We develop an approach to construct local bulk operators in a CFT to order $1/N^2$. Since 4-point functions are not fixed by conformal invariance we use the OPE to categorize possible forms for a bulk operator. Using previous results on 3-point functions we construct a local bulk operator in each OPE channel. We then impose the condition that the bulk operators constructed in different channels agree, and hence give rise to a well-defined bulk operator. We refer to this condition as the "bulk bootstrap." We argue and explicitly show in some examples that the bulk bootstrap leads to some of the…

Conformal bootstrap for the BFKL Pomeron

We calculate the interaction vertex of three BFKL states including the bare triple BFKL Pomeron coupling and discuss its relation with the correlation functions in two-dimensional conformal field theory. We construct the operator algebra of the fields interpolating the BFKL states and show that in the multi-color limit the vertex satisfies the constraints imposed by the conformal bootstrap on the structure constants of the operator product expansion in conformal field theory.

有限体积下动量空间中的共形bootstrap

Conformal bootstrap in momentum space at finite volume

本文在$D=2,3$维径向量子化中利用共形Ward恒等式求解Wightman函数的傅里叶分量，构建了有限体积下动量空间的共形块，并展示了能提供非平凡约束的bootstrap方程实例。

Convergent Momentum-Space OPE and Bootstrap Equations in Conformal Field Theory

General principles of quantum field theory imply that there exists an operator product expansion (OPE) for Wightman functions in Minkowski momentum space that converges for arbitrary kinematics. This convergence is guaranteed to hold in the sense of a distribution, meaning that it holds for correlation functions smeared by smooth test functions. The conformal blocks for this OPE are conceptually extremely simple: they are products of 3-point functions. We construct the conformal blocks in 2-dimensional conformal field theory and show that the OPE in fact converges pointwise to an ordinary func…

源自嵌入空间算子乘积展开的共形自举方程

Conformal Bootstrap Equations from the Embedding Space Operator Product Expansion

本文在嵌入空间OPE形式化框架下构造张量推广的共形块和特殊张量结构基，直接导出任意洛伦兹表示中准初级算子的共形自举方程，并以⟨SSSV⟩为例验证算法。

Perturbative Four-Point Functions from the Analytic Conformal Bootstrap

We apply the analytic conformal bootstrap method to study weakly coupled conformal gauge theories in four dimensions. We employ twist conformal blocks to find the most general form of the one-loop four-point correlation function of identical scalar operators, without any reference to Feynman calculations. The method relies only on symmetries of the model. In particular, it does not require introducing any regularisation and it is free from the redundancies usually associated with the Feynman approach. By supplementing the general solution with known data for a small number of operators, we rec…

A functional approach to the numerical conformal bootstrap

We apply recently constructed functional bases to the numerical conformal bootstrap for 1D CFTs. We argue and show that numerical results in this basis converge much faster than the traditional derivative basis. In particular, truncations of the crossing equation with even a handful of components can lead to extremely accurate results, in opposition to hundreds of components in the usual approach. We explain how this is a consequence of the functional basis correctly capturing the asymptotics of bound-saturating extremal solutions to crossing. We discuss how these methods can and should be imp…

Solving the Conformal Bootstrap: Four-Fermion Interactions at 2<d<4

We formulate the conformal bootstrap approach to four--fermion theory at its strong coupling fixed point in dimensions $2<d<4$. We present a solution of the bootstrap equations in the five--vertex approximation. We show that the bootstrap approach gives a particularly simple way to obtain next to leading order corrections to critical exponents in the large $N$ expansion and present the values of the anomalous dimensions of the fermion field $ψ$ and the composite $\barψψ$ to order $1/N^2$.

Bootstrapping conformal QED$_3$ and deconfined quantum critical point

We bootstrap the deconfined quantum critical point (DQCP) and 3D Quantum Electrodynamics (QED$_3$) coupled to $N_f$ flavors of two-component Dirac fermions. We show the lattice and perturbative results on the $SO(5)$ symmetric DQCP are excluded by the bootstrap bounds combined with an irrelevant condition of the lowest singlet scalar. Remarkably, we discover a new family of kinks in the 3D $SO(N)$ vector bootstrap bounds with $N\geqslant6$. We demonstrate bound coincidences between $SU(N_f)$ adjoint and $SO(N_f^2-1)$ vector bootstrap which result from a novel algebraic relation between their c…

Conformal Bootstrap Deformations

We explore the space of extremal functionals in the conformal bootstrap. By recasting the bootstrap problem as a set of non-linear equations parameterized by the CFT data, we find an efficient algorithm for converging to the extremal solution corresponding to the boundary of allowed regions in the parameter space of CFTs. Furthermore, by deforming these solutions, we demonstrate that certain solutions corresponding to known theories are continuously connected. Employing these methods, we will explore the space of non-unitary CFTs in the context of modular as well as correlation function bootst…

Exclusion Inside or at the Border of Conformal Bootstrap Continent

How large can anomalous dimensions be in conformal field theories? What can we do to attain larger values? One attempt to obtain large anomalous dimensions efficiently is to use the Pauli exclusion principle. Certain operators constructed out of constituent fermions cannot form bound states without introducing non-trivial excitations. To assess the efficiency of this mechanism, we compare them with the numerical conformal bootstrap bound as well as with other interacting field theory examples. In two dimensions, it turns out to be the most efficient: it saturates the bound and is located at th…