Manifestation of a nontrivial vacuum in discrete light cone quantization

TL;DR

This paper investigates spontaneous symmetry breaking in a (1+1)-dimensional $eta^4$ model using discrete light cone quantization, revealing degenerate vacua and challenging the notion of vacuum triviality.

Contribution

It introduces a variational approach to analyze vacuum structure and stability in light-cone quantized models with zero modes, highlighting nontrivial vacua.

Findings

Degenerate vacua in the broken phase.

Vacuum triviality is spurious in this context.

Lower energy states than Fock vacuum in the broken phase.

Abstract

We study a (1+1)-dimensional $\lambda\phi^4$ model with a light-cone zero mode and constant external source to describe spontaneous symmetry breaking. In the broken phase, we find degenerate vacua and discuss their stability based on effective-potential analysis. The vacuum triviality is spurious in the broken phase because these states have lower energy than Fock vacuum. Our results are based on the variational principle.