R. Percacci

Publications (8)14.64 Total impact

• Source

  Available from: ArXiv

  Article: A short introduction to asymptotic safety

  R. Percacci
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  ABSTRACT: I discuss the notion of asymptotic safety and possible applications to quantum field theories of gravity and matter.
  10/2011;
• Source

  Available from: ArXiv

  Article: Electroweak S and T parameters from a fixed point condition.

  M Fabbrichesi, R Percacci, A Tonero, L Vecchi
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  ABSTRACT: We consider the standard model without the Higgs boson, where the Goldstone modes are described by a nonlinear sigma model. We study the renormalization group flow of the sigma model coupling f and of the electroweak parameters S and T. The condition that the couplings reach a fixed point at high energy leaves the low energy values of f and T arbitrary (to be determined experimentally) and fixes S to a value compatible with electroweak precision data.
  Physical Review Letters 07/2011; 107(2):021803. · 7.37 Impact Factor
• Source

  Available from: F. Bazzocchi

  Article: Fermions and Goldstone bosons in an asymptotically safe model

  F. Bazzocchi, M. Fabbrichesi, R. Percacci, A. Tonero, L. Vecchi
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  ABSTRACT: We consider a model in which Goldstone bosons, described by a SU(N) chiral nonlinear sigma model, are coupled to an N-plet of colored fermions by means of a Yukawa interaction. We study the one-loop renormalization group flow and show that the non-Gaussian UV fixed point, which is present in the purely bosonic model, is lost because of fermion loop effects unless N is sufficiently large. We then add four-fermion contact interactions to the lagrangian and show that in this case there exist several non-Gaussian fixed points. The strength of the contact interactions, predicted by the requirement that the theory flows towards a fixed point in the UV, is compared to the current experimental bounds. This toy model could provide an important building block of an asymptotically safe model of the weak interactions.
  05/2011;
• Source

  Available from: ArXiv

  Article: Asymptotic safety and the gauged SU(N) nonlinear sigma-model

  M. Fabbrichesi, R. Percacci, A. Tonero, O. Zanusso
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  ABSTRACT: We study the beta functions of the leading, two-derivative terms of the left-gauged SU(N) nonlinear sigma-model in d dimensions. In d>2, we find the usual Gaussian ultraviolet fixed point for the gauge coupling and an attractive non-Gaussian fixed point for the Goldstone boson coupling. The position of the latter fixed point controls the chiral expansion, unitarity and the strength of the tree-level Goldstone boson scattering amplitudes. Attention is paid to the gauge- and scheme-dependence of the results.
  10/2010;
• Source

  Available from: ArXiv

  Article: Asymptotic Safety, Emergence and Minimal Length

  R. Percacci, G. P. Vacca
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  ABSTRACT: There seems to be a common prejudice that asymptotic safety is either incompatible with, or at best unrelated to, the other topics in the title. This is not the case. In fact, we show that 1) the existence of a fixed point with suitable properties is a promising way of deriving emergent properties of gravity, and 2) there is a sense in which asymptotic safety implies a minimal length. In so doing we also discuss possible signatures of asymptotic safety in scattering experiments.
  Classical and Quantum Gravity 08/2010; 27:245026. · 3.32 Impact Factor
• Source

  Available from: ArXiv

  Article: Gravitational corrections to Yukawa systems

  O. Zanusso, L. Zambelli, G.P. Vacca, R. Percacci
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  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.
  Physics Letters B 04/2010; 689:90-94. · 3.95 Impact Factor
• Source

  Available from: ArXiv

  Article: One loop beta functions and fixed points in Higher Derivative Sigma Models

  R. Percacci, O. Zanusso
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  ABSTRACT: We calculate the one loop beta functions for nonlinear sigma models in four dimensions containing general two and four derivative terms. In the O(N) model there are four such terms and nontrivial fixed points exist for all N \geq 4. In the chiral SU(N) models there are in general six couplings, but only five for N=3 and four for N=2; we find fixed points only for N=2,3. In the approximation considered, the four derivative couplings are asymptotically free but the coupling in the two derivative term has a nonzero limit. These results support the hypothesis that certain sigma models may be asymptotically safe. Comment: 26 pages
  10/2009;
• Source

  Available from: arxiv.org

  Article: Cancellation of Global Anomalies in Spontaneously Broken Gauge Theories

  M. Fabbrichesi, R. Percacci, M. Piai, M. Serone
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  ABSTRACT: We discuss the generalization to global gauge anomalies of the familiar procedure for the cancellation of local gauge anomalies in effective theories of spontaneously broken symmetries. We illustrate this mechanism in a recently proposed six-dimensional extension of the standard model. Comment: 5 pages; v2: version to appear in Phys. Rev. D
  07/2002;