Europhys. Lett, 45 (5), pp. 612-618 (1999)
Gauge dependence of the order parameter
in the Ginzburg-Landau model
and the critical fluctuations in
F. S. Nogueira
Centre de Physique Théorique, Ecole Polytechnique - F-91128 Palaiseau Cedex, France
(received 23 September 1998; accepted in final form 4 January 1999)
PACS. 74.20De - Phenomenological theories (two-fluid, Ginzburg-Landau, etc.).
PACS. 11.10Hi - Renormalization group evolution of parameters.
The critical fluctuations of superconductors are discussed in a fixed dimension scaling suited to describe the type-II regime. The gauge dependence of the anomalous dimension of the scalar field is established exactly from the Ward-Takahashi identities. Its fixed-point value gives the critical exponent and it is shown that is gauge independent, as expected on physical grounds. In the scaling considered, is found to be zero at 1-loop order, while . This result is just the 1-loop values for the XY model obtained in the fixed-dimension renormalization group approach. It is shown that this XY behavior holds at all orders. The result should be contrasted with the negative values frequently reported in the literature.