2018/01/31 by Damiano Anselmi · 2 citations
Mathematics · Physics and Astronomy · #Amplitude #Analytic continuation #Black Holes and Theoretical Physics #Computer science #Continuation #Cosmology and Gravitation Theories #Degrees of freedom (physics and chemistry) #Euclidean geometry #Feynman diagram #Geometry #Mathematical analysis #Mathematical physics #Mathematics #Noncommutative and Quantum Gravity Theories #Physics #Quantum mechanics #Theoretical physics #Unitarity #Unitary state #hep-ph #hep-th #math-ph #math.MP
paper · pdf · doi:10.1007/jhep02(2018)141
published as J. High Energy Phys. 02 (2018) 141 · 57 pages, 29 figures; v2: minor changes, JHEP
openalex publication_date 2018/02/01 · arxiv created 2018/02/25 · arxiv updated 2018/02/27 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The “fakeon” is a fake degree of freedom, i.e. a degree of freedom that does not belong to the physical spectrum, but propagates inside the Feynman diagrams. Fakeons can be used to make higher-derivative theories unitary. Moreover, they help us clarify how the Lee-Wick models work. In this paper we study the fakeon models, that is to say the theories that contain fake and physical degrees of freedom. We formulate them by (nonanalytically) Wick rotating their Euclidean versions. We investigate the properties of arbitrary Feynman diagrams and, among other things, prove that the fakeon models are perturbatively unitary to all orders. If standard power counting constraints are fulfilled, the models are also renormalizable. The S matrix is regionwise analytic. The amplitudes can be continued from the Euclidean region to the other regions by means of an unambiguous, but nonanalytic, operation, called average continuation. We compute the average continuation of typical amplitudes in four, three and two dimensions and show that its predictions agree with those of the nonanalytic Wick rotation. By reconciling renormalizability and unitarity in higher-derivative theories, the fakeon models are good candidates to explain quantum gravity.