7 research outputs found
The Application of the Newman-Janis Algorithm in Obtaining Interior Solutions of the Kerr Metric
In this paper we present a class of metrics to be considered as new possible
sources for the Kerr metric. These new solutions are generated by applying the
Newman-Janis algorithm (NJA) to any static spherically symmetric (SSS) ``seed''
metric. The continuity conditions for joining any two of these new metrics is
presented. A specific analysis of the joining of interior solutions to the Kerr
exterior is made. The boundary conditions used are those first developed by
Dormois and Israel. We find that the NJA can be used to generate new physically
allowable interior solutions. These new solutions can be matched smoothly to
the Kerr metric. We present a general method for finding such solutions with
oblate spheroidal boundary surfaces. Finally a trial solution is found and
presented.Comment: 11 pages, Latex, 4 postscript figures. To be published in Classical
and Quantum Gravity. Title and abstract are now on the same pag
Perinatal Nurses' Knowledge and Attitudes about AIDS
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72462/1/j.1552-6909.1989.tb00489.x.pd
Extended Theories of Gravity
Extended Theories of Gravity can be considered a new paradigm to cure
shortcomings of General Relativity at infrared and ultraviolet scales. They are
an approach that, by preserving the undoubtedly positive results of Einstein's
Theory, is aimed to address conceptual and experimental problems recently
emerged in Astrophysics, Cosmology and High Energy Physics. In particular, the
goal is to encompass, in a self-consistent scheme, problems like Inflation,
Dark Energy, Dark Matter, Large Scale Structure and, first of all, to give at
least an effective description of Quantum Gravity. We review the basic
principles that any gravitational theory has to follow. The geometrical
interpretation is discussed in a broad perspective in order to highlight the
basic assumptions of General Relativity and its possible extensions in the
general framework of gauge theories. Principles of such modifications are
presented, focusing on specific classes of theories like f (R)-gravity and
scalar-tensor gravity in the metric and Palatini approaches. The special role
of torsion is also discussed. The conceptual features of these theories are
fully explored and attention is payed to the issues of dynamical and conformal
equivalence between them considering also the initial value problem. A number
of viability criteria are presented considering the post-Newtonian and the
post-Minkowskian limits. In particular, we discuss the problems of neutrino
oscillations and gravitational waves in Extended Gravity. Finally, future
perspectives of Extended Gravity are considered with possibility to go beyond a
trial and error approach.Comment: 184 pages, 3 figures, survey to appear in Physics Report