Heavy Particle Towers and Nonlocal QFT

A number of gravitation-motivated theories, as well as theories with new coloured fermions predict heavy particle towers with spectral densities ρ(m²) growing faster than eᵐ, a characteristic of nonlocalizable theories. It is shown that if a light scalar, like the Higgs boson, interacts strongly with a heavy scalar particle tower with exponentially rising degeneracy, then the local low-energy theory is equivalent to an effective nonlocal scalar QFT. For energies approaching the nonlocality scale p²ΛNL², the scalar propagator and scattering amplitudes are modified by nonlocal factors of the form e^p²/Λ²NL. The double-Higgs production measurement at the LHC is proposed as a highly sensitive probe of nonlocality at the electroweak scale.