Evolutionary Reformulation of Quantum Gravity

We present a critical analysis of the Canonical approach to quantum gravity, which relies on the ambiguity of implementing a space-time slicing on the quantum level. We emphasize that such a splitting procedure is consistent only if a real matter fluid is involved in the dynamics.Comment: 5 pages, proceedings of the XI Marcel Grossmann meeting on Relativistic Astrophysics, July 23-29, 2006, Berlin, minor changes adde

EUROPEAN AUSTERITY WITHOUT GROWTH? EUROPEAN GROWTH WITHOUT EUROPEAN DEMOCRACY?

The European project is facing a crisis. Citizens no longer understand what the EU is about. Young people and the new ruling class have forgotten the clear message of the European project launched just after the Second World War "No wars ever again among Europeans." The founding fathers of the European Union are mentioned in history textbooks, but today Europe is felt as an irritating bureaucracy. In Europe, peace and economic stability are considered as a natural state, a gift from above. Why keep a useless EU alive? The state of the European Union is swiftly degenerating. In almost all the member states, the anti-European forces are gaining ground. Populism is not a new ideology and is not necessarily European: let's recall Peronism. In today's Europe populism is the new manifestation of nationalism. In Italy the Lega Nord is in Berlusconi's eurosceptic government. In France, the National Front is endangering UMP's hegemony. In Belgium the rows between the Flemish and the Walloons threatens the state's unity. In the Netherlands, Hungary, the Czech Republic, Austria and Finland, populist forces are either in the government or strongly influencing the government. National-populism is different from the nationalism of the past. De Gaulle's nationalism was an ideology founded on the "grandeur" of France's history and on a certain idea of Europe, which was "l'Europe de patrie", a kind of European unity accepting French leadership in world politics. Today national-populism is a form of micro-nationalism: it opposes the European project but without having a serious alternative. This is why populism is dangerous. Its real goal is not only the breaking down of the European Union but also the disintegration of the old nation states into micro-ethnic states, as what happened in former Yugoslavia.

Squeezing of toroidal accretion disks

Accretion disks around very compact objects such as very massive Black hole can grow according to thick toroidal models. We face the problem of defining how does change the thickness of a toroidal accretion disk spinning around a Schwarzschild Black hole under the influence of a toroidal magnetic field and by varying the fluid angular momentum. We consider both an hydrodynamic and a magnetohydrodynamic disk based on the Polish doughnut thick model. We show that the torus thickness remains basically unaffected but tends to increase or decrease slightly depending on the balance of the magnetic, gravitational and centrifugal effects which the disk is subjected to.Comment: 6 pages, 17 figures, to appear in EP

Implications of the Holst term in a f(R)f(R) theory with torsion

We analyze a modified $f(R)$ theory of gravity in the Palatini formulation, when an Holst term endowed with a dynamical Immirzi field is included. We study the basic features of the model, especially in view of liminating the torsion field via the Immirzi field and the scalar-tensor degrees of freedom of the $f(R)$ model. The main task of this study is the investigation of the morphology of the gravitational wave polarization when their coupling to a circle of test particles is considered. We first observe that the dynamics of the scalar mode of the $f(R)$ Lagrangian is frozen out, since its first order term identically vanishes. This allows a detailed characterization of the linearized theory, which outlines the emergence of a modified Newtonian potential in the static limit, and when time independence is relaxed a standard gravitational wave plus the scalar wave associated to the Immirzi field. Investigating the effect of the coupling of this scalar-tensor wave on a circle of test particles, we arrive to define two effective gravitational polarizations, corresponding to an equivalent phenomenological wave, whose morphology is anomalous with respect the standard case of General Relativity. In fact, the particle circle suffers modifications as it was subjected to modified plus and cross modes, whose specific features depend on the model free parameters and are, in principle, detectable via a data analysis procedure.Comment: 8 pages, 4 figures, accepted for publication in Physical Review

Classical and quantum behavior of the generic cosmological solution

In the present paper we generalize the original work of C.W. Misner \cite{M69q} about the quantum dynamics of the Bianchi type IX geometry near the cosmological singularity. We extend the analysis to the generic inhomogeneous universe by solving the super-momentum constraint and outlining the dynamical decoupling of spatial points. Firstly, we discuss the classical evolution of the model in terms of the Hamilton-Jacobi approach as applied to the super-momentum and super-Hamiltonian constraints; then we quantize it in the approximation of a square potential well after an ADM reduction of the dynamics with respect to the super-momentum constraint only. Such a reduction relies on a suitable form for the generic three-metric tensor which allows the use of its three functions as the new spatial coordinates. We get a functional representation of the quantum dynamics which is equivalent to the Misner-like one when extended point by point, since the Hilbert space factorizes into $\infty^3$ independent components due to the parametric role that the three-coordinates assume in the asymptotic potential term. Finally, we discuss the conditions for having a semiclassical behavior of the dynamics and we recognize that this already corresponds to having mean occupation numbers of order $\mathcal{O}(10^2)$.Comment: 8 pages, AIP Proceedings, Eistein Century Conference, Paris 200

Cosmological implications of an evolutionary quantum gravity

The cosmological implications of an evolutionary quantum gravity are analyzed in the context of a generic inhomogeneous model. The Schr\"{o}dinger problem is formulated and solved in the presence of a scalar field, an ultrarelativistic matter and a perfect gas regarded as the dust-clock. Considering the actual phenomenology, it is shown how the evolutionary approach overlaps the Wheeler-DeWitt one.Comment: 4 pages; to appear in the proceedings of the II Stueckelberg Workshop, Int.J.Mod.Phys.A, references adde

Viscoresistive MHD Configurations of Plasma in Accretion Disks

We present a discussion of two-dimensional magneto-hydrodynamics (MHD) configurations, concerning the equilibria of accretion disks of a strongly magnetized astrophysical object. We set up a viscoresistive scenario which generalizes previous two-dimensional analyses by reconciling the ideal MHD coupling of the vertical and the radial equilibria within the disk with the standard mechanism of the angular momentum transport, relying on dissipative properties of the plasma configuration. The linear features of the considered model are analytically developed and the non-linear configuration problem is addressed, by fixing the entire disk profile at the same order of approximation. Indeed, the azimuthal and electron force balance equations are no longer automatically satisfied when poloidal currents and matter fluxes are included in the problem. These additional components of the equilibrium configuration induce a different morphology of the magnetic flux surface, with respect to the ideal and simply rotating disk.Comment: 19 pages, 4 figures. To appear on the Proceedings of the Second Italian-Pakistani Workshop on Relativistic Astrophysic