Thesis

NLO study of Lorentz violation: extended non- abelian models and Lorentz violating effective QED

• Call:

  IDPASC Portugal - PHD Programme 2019

• Academic Year:

  2019 / 2020

• Domain:

  Theoretical Particle Physics

• Supervisor:

  Brigitte Hiller

• Co-Supervisor:

  Marcos Rodrigues-Sampaio

• Institution:

  Universidade de Coimbra

• Host Institution:

  Universidade de Coimbra

• Abstract:

  In [1] we have studied n-point one loop functions in the photonic sector of Extended Quantum Electrodynamics and shown that no gauge anomalies are present, just as in standard QED, which is particularly tricky given that gamma-5 matrices can lead to spurious breaking due to regularization issues. The Lagrangian above has been shown to be multiplicatively renormalizable at one loop order in [2], where the divergent structure of both fermion and photon 2- and 3-point functions were studied in order to compute the renormalization constants and thereupon the beta-function. However reference [2] left out the explicit complete evaluation of 2 and 3 point functions as it contained regularization dependent parameters. Some important and immediate issues must be explored: 1. An important point addressed in [1], [3] was the careful treatment of the gamma5-matrix in divergent amplitudes. Under the light of [4] and using Implicit regularization we intend to extend the work by Colladay and McDonald in [5] and generalise the analysis of [2] to non-abelian theories without fermions. Standard Model extensions have motivations as mentioned in [5] where neutrino oscillation physics and large radiative corrections due to strong coupling in QCD, to mention a few, can lead to good bounds for Lorentz violation. 2. There appear CPT even and odd terms so that the radiative corrections can therefore be calculated separately. The CPT odd term is topological which means that it is defined up to large gauge transformations. The question whether we want to impose gauge symmetry at the level of the Lagrangian or the action becomes important. It may lead to a quantisation of coupling constants when radiative corrections are taken into account [6]. Besides its Riemann-tensor-like symmetries may bring some other constraints on (arbitrarily defined) surface terms. This study is important because CPT-odd terms behave analogously to the usual strong coupling, while the CPT-even parameter increases with energy scale. Thus CPT-even effects in the strong interactions may increase significantly at higher-energy scales and become observable. Bibliography: [1] A. R. Vieira, A. L. Cherchiglia and Marcos Sampaio, Phys. Rev. D93 (2016) 025029. [2] V. A. Kostelecký, C. D. Lane and A. G. Pickering, Phys. Rev. D 65, 056006 (2002). [3] A. Viglioni, A.L. Cherchiglia, A.R. Vieira, Brigitte Hiller, Marcos Sampaio, Phys.Rev. D94 (2016) no.6, 065023; J.S. Porto, A.R. Vieira, A.L. Cherchiglia, Marcos Sampaio, Brigitte Hiller, Eur.Phys.J. C78 (2018) no.2, 160. [4] A. M. Bruque, A. L. Cherchiglia, M. Perez-Victoria, JHEP08 (2018) 109. [5] D. Colladay and P. McDonald, Phys. Rev. D75 (2007) 105002. [6] G. Dunne, Lectures at the 1998 Les Houches Summer School, hep-th/9902115v1. [7] M. Haghighat et al., Int.J.Mod.Phys. A28 (2013) 1350115.