1998 (IPP)

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    Time in a quantum gravity
    (2015-03-13) Biswas, S.; Shaw, A.; Modak, B.
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    On the brown-york quasilocal energy, gravitational charge, and black hole event horizons
    (2015-03-13) Bose, Sukanta; Dadhich, Naresh
    We prove the recently proposed identity for certain black hole spacetimes that relates the difference of the Brown-York quasilocal energy and the Komar charge at the event horizon of the hole to the total energy of the spacetime. We prove this identity for the Kerr-Newman family of black hole spacetimes and for non-static (cosmological) spherically symmetric shear-free perfect fluid solutions of general relativity that contain black hole event horizons. We explicitly demonstrate its validity by applying it to several asymptotically fiat as well as non-fiat black hole solutions, including the case of a black hole with a global monopole charge.
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    Global anomalies in canonical gravity
    (2015-03-11) Surya, Sumati; Vaidya, Sachindeo
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    Conformal transformations in classical gravitational theories and in cosmology
    (2015-03-11) Faraoni, Valerio; Gunzing , Edgard; Nardone, Pasquale
    In recent years, the use of conformal transformation techniques has become widespread in the literature on gravitational theories alternative to general relativity, on cosmology, and on nonminimally coupled scalar fields. Tipically, the transformation to the Einstein frame is generated by a fundamental scalar field already present in the theory. In this context, the problem of which conformal frame is the physical one has to be dealt with and, in the general case, it has been clarified only recently; the formulation of a theory in the "new" conformal frame leads to departures from canonical Einstein gravity. In this article, we review the literature on conformal transformations in classical gravitational theories and in cosmology, seen both as purely mathematical tools and as maps with physically relevant aspects. It appears particularly urgent to refer the analysis of experimental tests of Brans-Dicke and scalar-tensor theories of gravity, as well as the predictions of cosmological inflationary scenarios, to the physical conformal frame, in order to have a meaningful comparison with the observations.