Attractive Casimir effect in an infrared modified gluon bag model
  In this work, we are motivated by previous attempts to derive the vacuum contribution to the bag energy in terms of familiar Casimir energy calculations for spherical geometries. A simple infrared modified model is introduced which allows studying the effects of the analytic structure as well as the geometry in a clear manner. In this context, we show that if a class of infrared vanishing effective gluon propagators is considered, then the renormalized vacuum energy for a spherical bag is attractive, as required by the bag model to adjust hadron spectroscopy. 
L. E. Oxman (1), N. F. Svaiter (2) and R. L. P. G. Amaral (1) ((1)   Universidade Federal Fluminense, (2) Centro Brasileiro ...