Speaker
Description
Hamiltonian truncation is a powerful non-perturbative method for quantum field theory, but its accuracy is generally limited by the influence of high-energy states excluded from the truncated Hilbert space. I will present Hamiltonian Truncation Effective Theory (HTET), which addresses this issue by interpreting the truncation scale as an effective field theory cutoff and encoding the effects of the discarded states into an effective Hamiltonian acting within the truncated space. The two-dimensional $\lambda \phi^4$ theory provides a useful benchmark for this framework, where HTET yields a systematic improvement in the computation of low-energy observables. Beyond leading order, the effective Hamiltonian develops a non-local structure. Ongoing work focuses on extending this framework to light-front Hamiltonian truncation, with the goal of constructing a direct and systematic HTET formulation in the light-front setting.