One-loop multicollinear limits from 2-point amplitudes on self-dual backgrounds

For scattering amplitudes in strong background fields, it is — at least in principle — possible to perturbatively expand the background to obtain higher-point vacuum amplitudes. In the case of self-dual plane wave backgrounds we consider this expansion for two-point, one-loop amplitudes in pure Yang-Mills, QED and QCD. This enables us to obtain multicollinear limits of 1-loop vacuum amplitudes; the resulting helicity configurations are surprisingly restricted, with only the all-plus helicity amplitude surviving. These results are shown to be consistent with well-known vacuum amplitudes. We also show that for both abelian and non-abelian supersymmetric gauge theories, there is no helicity flip (and hence no vacuum birefringence) on any plane wave background, generalising a result previously known in the Euler-Heisenberg limit of super-QED.

The “Shirt Pocket” Technique—An Alternative for Augmentation-Mastopexy

Augmentation-mastopexy is a frequent procedure with high rates of early recurrence of breast ptosis, mainly after subglandular approach. The dual-plane techniques, based on the cranial dissection of the pectoralis, is the most used, but this plane does not cover the inferior pole of the breast. Then, the possibility of a downward dissection of the muscle seems to be more reasonable to retain the implant and improve postoperative results. This study aimed to review the anatomy of the pectoralis in cadavers and the use of its downward dissection to create a pocket for breast implant as a “shirt pocket.” This maneuver was associated with a superior-based dermoglandular flap to overprotect the inferior pole. No complications were related in the postoperative period. The anatomic review showed that the “shirt pocket” is a safe option if done carefully. The technique demonstrated to be feasible and seemed to be effective, being another alternative to prevent early recurrence of breast ptosis in these procedures.