14575890
Morphology of the large-scale structure
The Minkowski functionals are a mathematical tool to quantify morphological features of patterns. Some applications to the matter distribution in galaxy catalogues and N-body simulations are reviewed, with an emphasis on the effects of cosmic variance. The conclusions are that (i) the observed large-scale morphology is sensitive to cosmic variance on scales much larger than the nonlinear length (approx. 8 Mpc/h), and (ii) the large-scale morphology predicted by simulations is thus affected by finite-size effects, but nonetheless a Lambda-CDM model is favored.
10408360
Scaling laws in the cosmic structure and renormalization group
There is an evidence of a scale-invariant matter distribution up to scales over 10 Mpc. We review scaling (fractal or multifractal) models of large-scale structure and their observational evidence. We conclude that the dynamics of cosmological structure formation seems to be driven to a multifractal attractor. This supports previous studies, which we review, of structure formation by means of the renormalization group within a hydrodynamic formulation.
15703222
Newtonian limit of the singular f(R) gravity in the Palatini formalism
Recently D. Vollick [Phys. Rev. D68, 063510 (2003)] has shown that the inclusion of the 1/R curvature terms in the gravitational action and the use of the Palatini formalism offer an alternative explanation for cosmological acceleration. In this work we show not only that this model of Vollick does not have a good Newtonian limit, but also that any f(R) theory with a pole of order n in R=0 and its second derivative respect to R evaluated at Ro is not zero, where Ro is the scalar curvature of background, does not have a good Newtonian limit.
9451406
Superselection sectors in asymptotic quantization of gravity
Using the continuity of the scalar ψ2 (the mass aspect) at null infinity through 1° we show that the space of radiative solutions of general relativity can be thought of a fibered space where the value of ψ2 at 1° plays the role of the base space. We also show that the restriction of the available symplectic form to each “fiber” is degenerate along directions that represent supertranslations of the BMS group. By factoring out these gauge directions we obtain the reduced phase space for the radiation data. This reduced phase space posses a global structure, i.e., it does not distinguishes between future or past null infinity. Thus, it can be used as the space of quantum gravitons. Moreover, a (pre)Hilbert space can be constructed on each “fiber” if an appropriate definition of scalar product is provided. Since there is no natural correspondence between the reduced phase spaces of different leaves they define superselection sectors on the space of asymptotic quantum states. We briefly review the dynamics of...