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Creators/Authors contains: "Percacci, Roberto"

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  1. ; ; ; (, Journal of High Energy Physics)
    A<sc>bstract</sc> We calculate the scattering amplitude in the two dimensionalCP(1) model in a regularization scheme independent way. When using cutoff regularization, a new Feynman rule from the path integral measure is required if one is to preserve the symmetry. The physical running of the coupling with renormalization scale arises from a UV finite Feynman integral in all schemes. We reproduce the usual result with asymptotic freedom, but the pathway to obtaining the beta function can be different in different schemes. The results can be extended to theO(N) model, for allN. We also comment on the way that this model evades the classic argument by Landau against asymptotic freedom in non-gauge theories. 
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    Free, publicly-accessible full text available February 1, 2026
  2. ; ; ; (, Physical Review Letters)
    We argue that the well-known beta functions of quadratic gravity do not correspond to the physical dependence of scattering amplitudes on external momenta, and derive the correct physical beta functions. Asymptotic freedom turns out to be compatible with the absence of tachyons. 
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  3. ; ; (, Physical Review D)
    We explore the properties of a simple renormalizable shift-symmetric model with a higher-derivative kinetic energy and quartic-derivative coupling that can serve as a toy model for higher-derivative theories of gravity. The scattering amplitude behaves as in a normal effective field theory below the threshold for the production of ghosts, but has an unexpectedly soft behavior above the threshold. The physical running of the parameters is extracted from the two-point and four-point amplitudes. The results are compared to those obtained by other methods and are found to agree only in limiting cases. We draw several lessons that may also apply to gravity. 
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