Gauge Invariance of a Critical Number of Flavours in QED3 |
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Authors: | A Bashir A Raya S Sánchez-Madrigal and C D Roberts |
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Institution: | Dipartimento di Fisica “E. Amaldi”, Università di Roma Tre, I-00146 Rome, Italy |
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Abstract: | The fermion propagator in an arbitrary covariant gauge can be obtained from the Landau gauge result via a Landau–Khalatnikov–Fradkin
transformation. This transformation can be written in a practically useful form in both configuration and momentum space.
It is therefore possible to anticipate effects of a gauge transformation on the propagator’s analytic properties. These facts
enable one to establish that if a critical number of flavours for chiral symmetry restoration and deconfinement exists in
noncompact QED3, then its value is independent of the gauge parameter. This is explicated using simple forms for the fermion–photon
vertex and the photon vacuum polarisation. The illustration highlights pitfalls that must be avoided in order to arrive at
valid conclusions. Landau gauge is seen to be the covariant gauge in which the propagator avoids modification by a non-dynamical
gauge-dependent exponential factor, whose presence can obscure truly observable features of the theory. |
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