Integrable Quantum Field Theories can be solved exactly using bootstrap
techniques based on their elastic and factorisable S-matrix. While knowledge of
the scattering amplitudes reveals the exact spectrum of particles and their
on-shell dynamics, the expression of the matrix elements of the various
operators allows the reconstruction of off-shell quantities such as two-point
correlation functions with a high level of precision. In this review, we
summarise results relevant to the contact point between theory and experiment
providing a number of quantities that can be computed theoretically with great
accuracy. We concentrate on universal amplitude ratios which can be determined
from the measurement of generalised susceptibilities, and dynamical structure
factors, which can be accessed experimentally e.g. via inelastic neutron
scattering or nuclear magnetic resonance. Besides an overview of the subject
and a summary of recent advances, we also present new results regarding
generalised susceptibilities in the tricritical Ising universality class.Comment: 53 pages, 12 figures. arXiv admin note: text overlap with
arXiv:2109.0976