2,954 research outputs found
On unitarity of a linearized Yang-Mills formulation for massless and massive gravity with propagating torsion
A perturbative regime based on contortion as a dynamical variable and metric
as a (classical) fixed background, is performed in the context of a pure
Yang-Mills formulation for gravity in a dimensional space-time. In the
massless case we show that the theory contains three degrees of freedom and
only one is a non-unitary mode. Next, we introduce quadratical terms dependent
on torsion, which preserve parity and general covariance. The linearized
version reproduces an analogue Hilbert-Einstein-Fierz-Pauli unitary massive
theory plus three massless modes, two of them represents non-unitary ones.
Finally we confirm the existence of a family of unitary Yang-Mills-extended
theories which are classically consistent with Einstein's solutions coming from
non massive and topologically massive gravity. The unitarity of these
YM-extended theories is shown in a perturbative regime. A possible way to
perform a non-perturbative study is remarked.Comment: To appear in International Journal of Modern Physics
On Consistence of Material Coupling in a GL(3,R) Gauge Formulation of Gravity
A covariant scheme for material coupling with gauge formulation of
gravity is studied. We revisit a known idea of a Yang-Mills type construction,
where quadratical power of cosmological constant have to be considered in
consistence with vacuum Einstein's gravity. Then, matter coupling with gravity
is introduced and some constraints on fields and background appear. Finally,
exploring the N=3 case we elucidate that introduction of auxiliary fields
decreases the number of these constraints.Comment: 9 pages, LaTeX, title, and abstract changed. To appear in
Mod.Phys.Lett.A, Vol. 18, No. 25 (2003) pp. 1753-176
Inverse Conductivity Problem for a Parabolic Equation using a Carlemen Estimate with one Observation
For the heat equation in a bounded domain we give a stability result for a
smooth diffusion coefficient. The key ingredients are a global Carleman-type
estimate, a Poincar\'e-type estimate and an energy estimate with a single
observation acting on a part of the boundary
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