High Temperature Dimensional Reduction And Parity Violation

The effective super-renormalizable 3-dimensional Lagrangian, describing the high temperature limit of chiral gauge theories, has more symmetry than the original 4d Lagrangian: parity violation is absent. Parity violation appears in the 3d theory only through higher-dimensional operators. We compute the coefficients of dominant P-odd operators in the Standard Electroweak theory and discuss their implications. We also clarify the parametric accuracy obtained with dimensional reduction. 1 keijo.kajantie@cern.ch 2 mikko.laine@cern.ch 3 kari@nordita.dk 4 mshaposh@nxth04.cern.ch 1 Introduction A general feature of effective field theories is that they may have more symmetries than the corresponding original theories. These extra symmetries are then broken by higher-dimensional operators in the effective theory. In many cases, the higher order operators are non-renormalizable whereas the "effective" Lagrangian is renormalizable. A familiar example is GUT-induced baryon number violat..