19,590 research outputs found
Non-Quadratic Gauge Fixing and Global Gauge Invariance in the Effective Action
The possibility of having a gauge fixing term in the effective Lagrangian
that is not a quadratic expression has been explored in spin-two theories so as
to have a propagator that is both traceless and transverse. We first show how
this same approach can be used in spontaneously broken gauge theories as an
alternate to the 't Hooft gauge fixing which avoids terms quadratic in the
scalar fields. This "non-quadratic" gauge fixing in the effective action
results in there being two complex Fermionic and one real Bosonic ghost fields.
A global gauge invariance involving a Fermionic gauge parameter, analogous to
the usual BRST invariance, is present in this effective action.Comment: 4 pages, revtex4 (submitted to Phys. Rev. D
Report of the Terrestrial Bodies Science Working Group. Volume 8: The comets
The determination of the nuclear and atmospheric properties of comets, and the interaction of the solar wind with the comet tail are scientific objectives for a mission to one or more comets in the next decade. Recommended priorities for direct cometary exploration are listed
The Effective Potential in Non-Conformal Gauge Theories
By using the renormalization group (RG) equation it has proved possible to
sum logarithmic corrections to quantities that arise due to quantum effects in
field theories. In particular, the effective potential V in the Standard Model
in the limit that there are no massive parameters in the classical action (the
"conformal limit") has been subject to this analysis, as has the effective
potential in a scalar theory with a quartic self coupling and in massless
scalar electrodynamics. Having multiple coupling constants and/or mass
parameters in the initial action complicates this analysis, as then several
mass scales arise. We show how to address this problem by considering the
effective potential in scalar electrodynamics when the scalar field has a tree
level mass term. In addition to summing logarithmic corrections by using the RG
equation, we also consider the consequences of the condition V'(v)=0 where v is
the vacuum expectation value of the scalar. If V is expanded in powers of the
logarithms that arise, then it proves possible to show that either v is zero or
that V is independent of the scalar. (That is, either there is no spontaneous
symmetry breaking or the vacuum expectation value is not determined by
minimizing V as V is "flat".
The long wavelength limit of hard thermal loop effective actions
We derive a closed form expression for the long wavelength limit of the
effective action for hard thermal loops in an external gravitational field. It
is a function of the metric, independent of time derivatives. It is compared
and contrasted with the static limit, and with the corresponding limits in an
external Yang-Mills field.Comment: 5 page
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