Amplitudes are the major logical object in Quantum Theory. Despite this fact they presents no physical reality and in consequence only observables can be experimetally checked. We discuss the possibility of a theory of Quantum Probabilities capable of give full account to quantum phenomena. Advanteges of this formulation are the evidence of physical processes not described by the orotodox formu...

Abstract Scattering amplitudes are both a wonderful playground to discover novel ideas in quantum field theory and simultaneously of immense phenomenological importance make precision predictions for e.g. particle collider observables more recently also gravitational wave signals. In this review chapter, we give an overview some the exciting recent progress on reformulating QFT terms mathematic...

We review the status of the leptonic decay constants f K and f ,⊥ K of the K and K * , respectively , and the SU(3) breaking quantities a 1 (K) and a ,⊥ 1 (K *), the first Gegenbauer-moments of the leading-twist distribution amplitudes of K and K *. We obtain new predictions from QCD sum rules which are relevant for the calculation of K and K * form factors, for instance T B→K * 1 , which deter...

Splitting amplitudes are universal functions governing the collinear behavior of scattering amplitudes for massless particles. We compute the two-loop g → gg splitting amplitudes in QCD, N = 1, and N = 4 super-Yang-Mills theories, which describe the limits of two-loop n-point amplitudes where two gluon momenta become parallel. They also represent an ingredient in a direct x-space computation of...

In recent years there has been increasing attention to hard exclusive processes involving emission of soft pions in the final state. In the near future new experimental data will emerge and their interpretation requires information about the nucleon wave function. Such processes are attractive as they provide us new insights in the hadron (nucleon) structure. At this point the nucleon distribut...