A solution space for a system of null-state partial differential equations 2

Abstract

This article is the second of four that completely characterize a solution space ${\mathcal{S}}_N$ for a homogeneous system of $2N+3$ linear partial differential equations (PDEs) in 2N variables that arises in conformal field theory (CFT) and multiple Schramm-Lowner evolution (SLE). The system comprises $2N$ null-state equations and three conformal Ward identities which govern CFT correlation functions of $2N$ one-leg boundary operators. In the first article (part I), we use methods of analysis and linear algebra to prove that $\dim {\mathcal{S}}_N\le C_N$, with $C_N$ the $N$th Catalan number. The analysis of that article is complete except for the proof of a lemma that it invokes. This article provides the proof. The lemma states that if every interval among $(x_2,x_3),$ $(x_3,x_4),...,(x_{2N-1},x_{2N})$ is a two-leg interval of $F\in {\mathcal{S}}_N$, then $F$ vanishes. Proving this lemma by contradiction, we show that the existence of such a nonzero function implies the existence of a non-vanishing CFT two-point function involving primary operators with different conformal weights, an impossibility. This proof (which is rigorous in spite of our occasional reference to CFT) involves two different types of estimates, those that give the asymptotic behavior of F as the length of one interval vanishes, and those that give this behavior as the lengths of two intervals vanish simultaneously. We derive these estimates by using Green functions to rewrite certain null-state PDEs as integral equations, combining other null-state PDEs to obtain Schauder interior estimates, and then repeatedly integrating the integral equations with these estimates until we obtain optimal bounds. In the case where two adjacent interval lengths vanish, we use a Green function that contains the Jacobi heat kernel as its essential ingredient.

Minor typos from v1 corrected, acknowledgments expanded

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• Global and Local Multiple SLEs for $\kappa \le 4$ and Connection Probabilities for Level Lines of GFF
• A solution space for a system of null-state partial differential equations 3
• Pure partition functions of multiple SLEs
• Conformally covariant boundary correlation functions with a quantum group
• A formula for crossing probabilities of critical systems inside polygons
• Towards a conformal field theory for Schramm-Loewner evolutions
• Exact logarithmic four-point functions in the critical two-dimensional Ising model
• Four-point boundary connectivities in critical two-dimensional percolation from conformal invariance
• Boundary correlations in planar LERW and UST
• Connection Probabilities of Multiple FK-Ising Interfaces
• Numerical Study on a Crossing Probability for the Four-State Potts Model: Logarithmic Correction to the Finite-Size Scaling
• The singularities of Selberg- and Dotsenko-Fateev-like integrals
• Multiple Ising interfaces in annulus and $2N$-sided radial SLE