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Models of gravity with variable G and Λ have acquired greater relevance after the recent evidence in favour of the Einstein theory being non-perturbatively renormalizable in the Weinberg sense. The present paper builds a modified Arnowitt–Deser–Misner (ADM) action functional for such models which leads to a power-law growth of the scale factor for pure gravity and for a massless ϕ4 theory in a Universe with Robertson–Walker symmetry, in agreement with the recently developed fixed-point cosmology. Interestingly, the renormalization-group flow at the fixed point is found to be compatible with a Lagrangian description of the running quantities G and Λ. [ABSTRACT FROM AUTHOR]

Peierls brackets are part of the space-time approach to quantum field theory, and provide a Poisson bracket which, being defined for pairs of observables which are group invariant, is group invariant by construction. It is therefore well suited for combining the use of Poisson brackets and the full diffeomorphism group in general relativity. The present paper provides an introduction to the topic, with applications to gauge field theory. [ABSTRACT FROM AUTHOR]

For the first time accurate measurements of electron and positron fluxes in the energy range 0.2/10 GeV have been performed with the Alpha Magnetic Spectrometer (AMS) at altitudes of 370/390 km in the geographic latitude interval ±51.7°. We focused on the under-cutoff lepton fluxes inside the region of the South Atlantic Anomaly (SAA), defined as region where the local magnetic field B ≤ 0.26 G. A clear transition region from stably-trapped flux typical of the Inner Van Allen Belts to quasi-trapped flux typical underneath the Van Allen Belts is observed in the SAA up to energies O(Gev). The observations strongly support positrons abundance in the Inner Van Allen Belts, both in the stably trapped component and in the quasi-trapped one. The flux maps as a function of the canonical adiabatic variables L, α[sub o] are presented for the interval 0.95 < L < 3, 0° < α[sub o] < 90° for electrons (E < 10 GeV) and positrons (E<3 GeV). The results are compared with existing data at lower energies. [ABSTRACT FROM AUTHOR]

Vacuum fluctuations produce a force acting on a rigid Casimir cavity in a weak gravitational field. Such a force is here evaluated and is found to have opposite direction with respect to the gravitational acceleration; the order of magnitude for a multi-layer cavity configuration is analyzed and experimental detection is discussed, bearing in mind the current technological resources. [ABSTRACT FROM AUTHOR]