Scientific article
Open access

Cornering large-N$_{c}$ QCD with positivity bounds

Published inThe journal of high energy physics, vol. 2023, 94
Publication date2023
First online date2023-06-16

The simple analytic structure of meson scattering amplitudes in the large-N$_{c}$ limit, combined with positivity of the spectral density, provides precise predictions on low-energy observables. Building upon previous studies, we explore the allowed regions of chiral Lagrangian parameters and meson couplings to pions. We reveal a structure of kinks at all orders in the chiral expansion and develop analytical tools to show that kinks always correspond to amplitudes with a single light pole. We build (scalar- and vector-less) deformations of the Lovelace-Shapiro and Coon UV-complete amplitudes, and show that they lie close to the boundaries. Moreover, constraints from crossing-symmetry imply that meson couplings to pions become smaller as their spin increases, providing an explanation for the success of Vector Meson Dominance and holographic QCD. We study how these conclusions depend on assumptions about the high-energy behavior of amplitudes. Finally, we emphasize the complementarity between our results and Lattice computations in the exploration of large-N$_{c}$ QCD.

  • 1/N Expansion
  • Chiral Lagrangian
  • Chiral Symmetry
  • Scattering Amplitudes
  • Expansion 1/N: color
  • Meson: coupling
  • Meson: scattering amplitude
  • Effective Lagrangian: chiral
  • Density: spectral
  • Expansion: chiral
  • Quantum chromodynamics: holography
  • Kink
  • Structure
  • Buildings
  • Vector meson
  • High energy behavior
  • Meson dominance
  • Lattice
  • Pole
  • Spin
  • Deformation
Citation (ISO format)
FERNANDEZ, Clara et al. Cornering large-N$_{c}$ QCD with positivity bounds. In: The journal of high energy physics, 2023, vol. 2023, p. 94. doi: 10.1007/jhep06(2023)094
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Article (Published version)
ISSN of the journal1029-8479

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