#### Why (your) mass isn't gauge dependent: Nielsen Identities

- Event time: 2:00pm
- Event date: 5th May 2010
- Speaker: Des Johnston (Heriot-Watt University)
- Location: Lecture Theatre B, James Clerk Maxwell Building (JCMB) James Clerk Maxwell Building Peter Guthrie Tait Road Edinburgh EH9 3FD GB

### Event details

To do perturbative calculations in gauge theories it is necessary, or at least expedient, to fix a gauge. At first site it looks as if this introduces a gauge-dependence into perturbative calculations involving the effective potential - in particular, for masses in spontaneously broken gauge theories. However, an extended variant of the BRST invariance which guarantees the gauge independence of physical quantities means that such mass calculations *can* be shown to be gauge independent.

We discuss the toy example of the Abelian Higgs model (scalar electrodynamics) in detail, but identical considerations also apply to the Standard Model and even in quantum field theories of gravity.

#### Event resources

The Particle Physics Theory seminar is a weekly series of talks reflecting the diverse interests of the group. Topics include analytic and numerical calculations based on the Standard Model of elementary particle physics, theories exploring new physics, as well as more formal developments in gauge theories and gravity..