Speaker
Description
As has been seen in recent calculations for $\phi^4$ theory, tadpole contributions are important for symmetry-breaking effects and yet are missing from standard light-front calculations, because they require transitions to and from the vacuum. Inclusion of such vacuum transitions also implies contributions from vacuum bubbles. A perturbative calculation can make the distinction and subtract such unwanted bubbles by hand, but a nonperturbative calculation cannot. We propose a method by which vacuum transitions may be included in light-front calculations: momentum-conserving delta functions are replaced with model functions of finite width. This regulates the vacuum-bubble contributions. The vacuum energy can then be subtracted from the eigenenergy of a physical state, followed by the limit of zero width.
