Please visit Jefferson Lab Event Policies and Guidance before planning your next event: https://www.jlab.org/conference_planning.

# Light Cone 2018

14-18 May 2018
Jefferson Lab - CEBAF Center
US/Eastern timezone

## Non-vanishing of vacuum diagrams in light-cone perturbation theory

17 May 2018, 17:10
20m
F113 (Jefferson Lab - CEBAF Center)

### Speaker

Lubomir Martinovic (Institute of Physics SAS, Bratislava and BLTP JINR Dubna)

### Description

Recently, J. Collins has pointed out that vacuum diagrams are, contrary to the general belief, non-vanishing in light-front field theory. In our contribution, we first recall the old (forgotten) arguments by Chang and Ma and by Yan, why this should be so. Then we apply the argument of analyticity of the self-energy diagrams in \lambda\phi^3 and \lambda \phi^4 two-dimensional models in light-front (LF) perturbation theory to calculate the vacuum bubbles explicitly as p=0 values of the appropriate self-energy diagrams. The results are non-zero and agree with the usual Feynman-diagram calculation. Surprisingly, the light-front bubbles are non-vanishing NOT due to LF zero modes. This is confirmed by the DLCQ calculations, where the mode with n=0 (the LF zero mode k^+ =0) is manifestly absent, but the results still converge to the continuum values for increasing "harmonic resolution" K. Generalization to realistic 3+1 dimensional case and to e.g. Yukawa theory is straightforward. *) work done in collaboration with A. Dorokhov, BLTP JINR Dubna

### Primary author

Lubomir Martinovic (Institute of Physics SAS, Bratislava and BLTP JINR Dubna)

 Slides