424 research outputs found
Improved action functionals in non-perturbative quantum gravity
No full textModels of gravity with variable G and Lambda 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 phi**4 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 Lambda
Come Cristallo di Cianuro Rubano Arts Festival, Padua, Italy
No full textA composition for the harp and violoncello commissioned for Rubano Arts Festival, performed by Giulia Rettore and Leonardo Sapere (7 min
On the Uniqueness of the Lagrangian Description for a Charged Particle in External Magnetic Field, Il Nuovo Cimento 98A (1987) 387
No full textOn the Uniqueness of the Lagrangian Description for a Charged Particle in External Magnetic Field, Il Nuovo Cimento 98A (1987) 387
No full textArnowitt-Deser-Misner gravity with variable G and Lambda and fixed point cosmologies from the renormalization group
No full textModels of gravity with variable G and Lambda 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 applies the Arnowitt–
Deser–Misner (ADM) formalism to such a class of gravitational models. A
modified action functional is then built which reduces to the Einstein–Hilbert
action when G is constant, and leads to a power-law growth of the scale factor
for pure gravity and for a massless φ**4 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 Lambda
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