The eikonal approach to gravitational scattering and radiation at $$ \mathcal{O} $$(G3)

Using $$ \mathcal{N} $$ N = 8 supergravity as a theoretical laboratory, we extract the 3PM gravitational eikonal for two colliding massive scalars from the classical limit of the corresponding elastic two-loop amplitude. We employ the eikonal phase to obtain the physical deflection angle and to show how its non-relativistic (NR) and ultra-relativistic (UR) regimes are smoothly connected. Such a smooth interpolation rests on keeping contributions to the loop integrals originating from the full soft region, rather than restricting it to its potential sub-region. This task is efficiently carried out by using the method of differential equations with complete near-static boundary conditions. In contrast to the potential-region result, the physical deflection angle includes radiation-reaction contributions that are essential for recovering the finite and universal UR limit implied by general analyticity and crossing arguments. We finally discuss the real emission of massless states, which accounts for the imaginary part of the 3PM eikonal and for the dissipation of energy-momentum. Adopting a direct approach based on unitarity and on the classical limit of the inelastic tree-level amplitude, we are able to treat $$ \mathcal{N} $$ N = 8 and General Relativity on the same footing, and to complete the conservative 3PM eikonal in Einstein’s gravity by the addition of the radiation-reaction contribution. We also show how this approach can be used to compute waveforms, as well as the differential and integrated spectra, for the different radiated massless fields.

Towards the Virasoro-Shapiro amplitude in AdS5×S5

We propose a systematic procedure for obtaining all single trace 1/2-BPS correlators in $$ \mathcal{N} $$ N = 4 super Yang-Mills corresponding to the four-point tree-level amplitude for type IIB string theory in AdS5 × S5. The underlying idea is to compute generalised contact Witten diagrams coming from a 10d effective field theory on AdS5 × S5 whose coefficients are fixed by the flat space Virasoro-Shapiro amplitude up to ambiguities related to commutators of the 10d covariant derivatives which require additional information such as localisation. We illustrate this procedure by computing stringy corrections to the supergravity prediction for all single trace 1/2-BPS correlators up to $$ \mathcal{O} $$ O (α′7), and spell out a general algorithm for extending this to any order in α′.

Generalized two-point tree-level amplitude j f → j′ f′ in a magnetized medium

The tree-level two-point amplitudes for the transitions j f → j′ f′, where f is a fermion and j is a generalized current, in a constant uniform magnetic field of an arbitrary strength and in charged fermion plasma, for the j f f interaction vertices of the scalar, pseudoscalar, vector and axial-vector types have been calculated. The generalized current j could mean the field operator of a boson, or a current consisting of fermions, e.g. the neutrino current. The particular cases of a very strong magnetic field, and of the coherent scattering off the real fermions without change of their states (the "forward" scattering) have been analyzed. The contribution of the neutrino photoproduction process, [Formula: see text], to the neutrino emissivity has been calculated with taking account of a possible resonance on the virtual electron.

FLAVORED CP ASYMMETRIES FOR TYPE II SEESAW LEPTOGENESIS

A novel contribution to the leptonic CP asymmetries in type II seesaw leptogenesis scenarios is obtained for the cases in which flavor effects are relevant for the dynamics of leptogenesis. In the so-called flavored leptogenesis regime, the interference between the tree-level amplitude of the scalar triplet decaying into two leptons and the one-loop wave function correction with leptons in the loop, leads to a new nonvanishing CP asymmetry contribution. The latter conserves total lepton number but violates lepton flavor. Cases in which this novel contribution may be dominant in the generation of the baryon asymmetry are briefly discussed.

NONCOMMUTATIVE N = 2 p - p′ SYSTEM

We analyze several open and mixed sector tree-level amplitudes in N = 2 p - p′ systems with a constant magnetic B turned on. The three-point function vanishes on-shell. The four-point function, in the Seiberg–Witten (SW) low energy limit,2 is local, indicating the possible topological nature of the theory (in the SW low energy limit) and the possible relation between noncommutativeN = 2 p - p′system in two complex dimensions and in the SW limit, and (non)commutativeN = 2 p′ - p′system in two real dimensions. We discuss three extreme noncommutativity limits (after having taken the Seiberg–Witten low energy limit) of the mixed three-point function, and get two kinds of commutative nonassociative generalized star products. We make some speculative remarks related to reproducing the above four-point tree level amplitude in the open sector, from a field theory.