01662nas a2200121   4500008004100000245009600041210006900137260001300206520124300219100002001462700002201482856003601504       2012                        en  d00aNon-uniqueness results for critical metrics of regularized determinants  in four dimensions0 aNonuniqueness results for critical metrics of regularized determ  bSpringer3 aThe regularized determinant of the Paneitz operator arises in quantum gravity
(see Connes 1994, IV.4.$\gamma$). An explicit formula for the relative
determinant of two conformally related metrics was computed by Branson in
Branson (1996). A similar formula holds for Cheeger's half-torsion, which plays
a role in self-dual field theory (see Juhl, 2009), and is defined in terms of
regularized determinants of the Hodge laplacian on $p$-forms ($p < n/2$). In
this article we show that the corresponding actions are unbounded (above and
below) on any conformal four-manifold. We also show that the conformal class of
the round sphere admits a second solution which is not given by the pull-back
of the round metric by a conformal map, thus violating uniqueness up to gauge
equivalence. These results differ from the properties of the determinant of the
conformal Laplacian established in Chang and Yang (1995), Branson, Chang, and
Yang (1992), and Gursky (1997).
  We also study entire solutions of the Euler-Lagrange equation of $\log \det
P$ and the half-torsion $\tau_h$ on $\mathbb{R}^4 \setminus {0}$, and show the
existence of two families of periodic solutions. One of these families includes
Delaunay-type solutions.1 aGursky, Matthew1 aMalchiodi, Andrea  uhttp://hdl.handle.net/1963/6559