Gian Paolo Vacca

Triple pomeron vertex in the limit N(c) ---> infinity

In the hard pomeron theory with the number of colours Nc in the infinity limit the diffractive amplitude obtained in [3] is compared with the results found for Nc=3 in [1] and in the dipole approach in [5]. It is shown that the double pomeron exchange contribution can be substituted by an equivalent triple pomeron interaction term. After such a substitution the triple pomeron vertices in [1,3,5] essentially coincide. It is demonstrated that, in any form, the triple pomeron vertex is conformal invariant. It is also shown that higher order densities in the dipole approach do not involve 1 to k pomeron verteces with k>2 but are rather given by a set of pomeron fan diagrams with only a triple pomeron coupling.

A new odderon solution in perturbative QCD

Abstract We present and discuss a new bound state solution of the three gluon system in perturbative QCD. It carries the quantum numbers of the odderon, has intercept at one and couples to the impact factor γ ∗ →η c .

Gravitational corrections to Yukawa systems

Abstract We compute the gravitational corrections to the running of couplings in a scalar-fermion system, using the Wilsonian approach. Our discussion is relevant for symmetric as well as for broken scalar phases. We find that the Yukawa and quartic scalar couplings become irrelevant at the Gaussian fixed point.

Search of scaling solutions in scalar–tensor gravity

We write new functional renormalization group equations for a scalar nonminimally coupled to gravity. Thanks to the choice of the parametrization and of the gauge fixing they are simpler than older equations and avoid some of the difficulties that were previously present. In three dimensions these equations admit, at least for sufficiently small fields, a solution that may be interpreted as a gravitationally dressed Wilson–Fisher fixed point. We also find for any dimension

f(R)

d>2

Generation of fluctuations during inflation: Comparison of stochastic and field-theoretic approaches

d>2 additional analytic scaling solutions which we study for

Asymptotic safety in O (N) scalar models coupled to gravity

d=3