College of Liberal Arts & Sciences

# Math Physics Seminar

**Abstract:**

Light front formulations of quantum field theory are useful for computing observables that are sensitive to the structure of hadrons. The key properties are (1) there is a subgroup of interaction independent boosts (2) the algebra of free fields restricted to the light front is irreducible (3) and the generators of translations tangent to the light front are interaction independent and (4) the spectrum of P⁻, which generates translation in the x⁺ direction tangent to the light front is positive.

These conditions can be used to argue that the light-front vacuum is the

same as the free field Fock vacuum. Light front generators of the

Poincaré group are Noether charges that arise from integration over the light-front, which should result is a set of generators defined in the irreducible algebra of fields on the light front. I will discuss how this fails to happen, how it can be fixed and used to recover the non-trivial vacuum for free fields of different masses, and discuss the implications for interacting theories.