### Conveners

#### Quantum Field and String Theory

- Miguel Montero (KU Leuven)

The dynamical cancellation of the vacuum energy of the QCD sector in the infrared regime is a relevant problem for both particle physics and cosmology. We find an argument related to the existence of Z2-symmetry for the renormalization group flow derived from the bare Yang-Mills Lagrangian, and show that the cancellation of the vacuum energy may arise motivated both from the renormalization...

Within supergravity (the low energy effective theory of string theory) there exist non-singular, horizonless solutions, called fuzzballs, with asymptotic charges $M$, $J$, $Q$ coincident with the charges of a black hole. Two immediate questions arise: 1) Are these solutions viable candidates for microstates that make up the black hole entropy? 2) Can humans (asymptotic observers) distinguish...

Elaboration of some fundamental relations in 3-dimensional quantum mechanics is

considered taking into account the restricted character of areas in radial distance. In such cases

the boundary behavior of the radial wave function and singularity of operators at the origin of

coordinates contribute to these relations. We derive the relation between the average value of the

operator’s time...

Photon-photon scattering in vacuum is one of the oldest and most intriguing predictions of quantum electrodynamics, as it would confirm what is called "vacuum polarization" and change our perception of the electromagnetic vacuum. However, experimental verification of scattering between real photons in vacuum hasn't materialized yet. This is due, in part, to the relative weakness of this...

The phenomenological application of the Higgs boson production via gluon fusion has been extensively studied in the full theory of the standard model and in the effective field theory approach where the Higgs boson couples directly to gluons. The latter is straightforwardly obtained by considering the heavy top mass limit. In this talk, following the ideas of universal dual amplitudes in the...

We propose a new algorithm based on the Loop-Tree Duality theorem to renormalise and calculate two-loop diagrams. The ultraviolet singularities are locally cancelled in a systematic way and at the integrand level, allowing for a full four-dimensional numerical implementation of the method. In particular, we apply the method to calculate the $H\to\gamma\gamma$ amplitude at two-loop level, and...

In the past years, we have been developing a novel technique, called Four-Dimensional Unsubtraction (FDU) which aims to obtain purely four-dimensional representations of the matrix elements contributing to physical observables. In this talk, we describe the application of the loop-tree duality (LTD) theorem to represent loop amplitudes in terms of tree-level like objects, focusing on the...

Scattering amplitudes in gauge theories display important applications for the calculation of observables in the physics that the LHC delivers and, also, formal properties where mathematical aspects are considered. In this talk we consider relations among scattering amplitudes that are obtained as a consequence of the duality between colour and kinematics. These relations are obtained from...