I think in this case, electroweak may be in reference to Lagrangian mechanics. Kinetic energy versus potential energy, or, offsetting mass via some form of internal energy. Considering the Traveller, well, [i]travels[/i], it might be that its mass is entirely compensated by some form of internal anomaly or mini-"Big Bang" that gives it the ability to move through space without displacing other masses it comes in contact with. Or, space magic. Whatever.