Distance Between Quantum Field Theories As A Measure Of Lorentz Violation

Understand

We study the distance between symmetry-violating quantum field theories and the surface of symmetric theories.

• We use this notion to quantify how precise Lorentz symmetry is today, according to experimental data.
• The metric in parameter space is defined \`a la Zamolodchikov, from the two-point function of the Lagrangian perturbation.
• The distance is obtained minimizing the length of paths connecting the Lorentz-violating theory to the Lorentz surface.