Gravity and the neutral currents: Effective interactions from the trace anomaly

Costantini

Dell’Atti

et al. 2015

Self Cite

We extend a previous phenomenological analysis of photon lensing in an external gravitational background to the case of a massless neutrino, and propose a method to incorporate radiative effects in the classical lens equations of neutrinos and photons. The study is performed for a Schwarzschild metric, generated by a point-like source, and expanded in the Newtonian potential at first order. We use a semiclassical approach, where the perturbative corrections to neutrino scattering, evaluated at one-loop in the Standard Model, are compared with the Einstein formula for the deflection using an impact parameter formulation. For this purpose, we use the renormalized expression of the graviton/fermion/fermion vertex presented in previous studies. We show the agreement between the classical and the semiclassical formulations, for values of the impact parameter b h of the neutrinos of the order of b h ∼ 20, measured in units of the Schwarzschild radius. The analysis is then extended with the inclusion of the post Newtonian corrections in the external gravity field, showing that this extension finds application in the case of the scattering of a neutrino/photon off a primordial black hole. The energy dependence of the deflection, generated by the quantum corrections, is then combined with the standard formulation of the classical lens equations. We illustrate our approach by detailed numerical studies, using as a reference both the thin lens and the Virbhadra-Ellis lens.

Section: Discussionsupporting

confidence: 77%

“…where we have denoted with Σ L the neutrino self-energy 17) which is a combination of the self-energy contributions…”

Section: Gravitational Interaction Of Neutrinosmentioning

confidence: 99%

Section: Jhep07(2015)160mentioning

confidence: 99%

Section: Gravitational Interaction Of Neutrinosmentioning

confidence: 99%

“…where we have included the minimal and the term of improvement [17]. For a conformally coupled scalar χ = 1/6.…”

Section: Jhep07(2015)160mentioning

confidence: 99%

See 3 more Smart Citations

Neutrino and photon lensing by black holes: radiative lens equations and post-Newtonian contributions

Costantini

Dell’Atti

et al. 2015

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Electroweak corrections to photon scattering, polarization and lensing in a gravitational background and the near horizon limit

Rose

Maglio

et al. 2015

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We investigate the semiclassical approach to the lensing of photons in a spherically symmetric gravitational background, starting from Born level and include in our analysis the radiative corrections obtained from the electroweak theory for the graviton/photon/photon vertex. In this approach, the cross section is related to the angular variation of the impact parameter (b), which is then solved for b as a function of the angle of deflection, and measured in horizon units (b h ≡ b/(2GM )). Exact numerical solutions for the angular deflection are presented. The numerical analysis shows that perturbation theory in a weak background agrees with the classical Einstein formula for the deflection already at distances of the order of 20 horizon units (∼ 20 b h ) and it is optimal in the description both of very strong and weak lensings. We show that the electroweak corrections to the cross section are sizeable, becoming very significant for high energy gamma rays. Our analysis covers in energy most of the photon spectrum, from the cosmic microwave background up to very high energy gamma rays, and scatterings with any value of the photon impact parameter. We also study the helicity-flip photon amplitude, which is of O(α 2 ) in the weak coupling α, and its massless fermion limit, which involves the exchange of a conformal anomaly pole. The corresponding cross section is proportional to the Born level result and brings to a simple renormalization of Einsten's formula.

Fermion scattering in a gravitational background: electroweak corrections and flavour transitions

Rose

Gabrielli

et al. 2014

Self Cite

Abstract:We investigate the role of the electroweak corrections to the scattering cross section of Standard Model fermions with gravity. We use both an approach of scattering off an external potential, where the gravitational field is treated as a classical background generated by a heavy source, and the usual interaction based on the one-graviton-exchange. In the potential appoach we consider the fields both of a localized and of a distributed gravitational source of spherical symmetry and uniform density, separating the cases of interactions taking place both in the inner and external regions of the source. This allows to make a distinction between interactions involving neutrinos and dark matter particles with a realistic gravity source, which cover the inner region, and the rest of the Standard model fermions. The role of the gravitationally induced flavour-changing transitions, as well as the flavour diagonal ones, are investigated in the limit of both large and small momentum transfers, deriving the structure of the corresponding Hamiltonian.