Celestial insights into the S-matrix bootstrap

Abstract

We consider 2-2 scattering in four spacetime dimensions in Celestial variables. Using the crossing symmetric dispersion relation (CSDR), we recast the Celestial amplitudes in terms of crossing symmetric partial waves. These partial waves have spurious singularities in the complex Celestial variable, which need to be removed in local theories. The locality constraints (null constraints) admit closed form expressions, which lead to novel bounds on partial wave moments. These bounds allow us to quantify the degree of low spin dominance(LSD) for scalar theories. We study a new kind of positivity that seems to be present in a wide class of theories. We prove that this positivity arises only in theories with a spin-0 dominance. The crossing symmetric partial waves with spurious singularities removed, dubbed as Feynman blocks, have remarkable properties in the Celestial variable, namely typically realness, in the sense of Geometric Function Theory (GFT). Using GFT techniques we derive non-projective bounds on Wilson coefficients in terms of partial wave moments.

Positivity, low twist dominance and CSDR for CFTs

“…• In the future, it will be important to understand the locality constraints in more detail, both analytically and numerically. In principle, it should be possible to derive the low twist dominance from these constraints along the lines of [38]. We present more evidence for this in appendix C. In appendix C, we also show how to use the locality constraints, when we have some idea about the spectrum, but leaving the OPE coefficients undetermined.…”

An infinite family of $w_{1+\infty}$ invariant theories on the celestial sphere

“…Please see[29] for a discussion of conformal bootstrap approach to celestial holography. Also recently celestial holography has been used to shed light on S-matrix bootstrap in[30] 2. To be more precise the wedge subalgebra of w 1+∞ .…”