Andreas Ringwald, Alexander Westphal (Theory group, DESY), Géraldine Servant (Theory group, DESY and II. Institute, UHH) and Günter Sigl (II. Institute, UHH)

Topics will include Non-canonical QCD axion models to address the strong CP problem, the electroweak hierarchy problem, dark matter. Investigation of alternative production mechanisms for generic axion-like-particles and cosmological histories,  observational tests, in particular gravitational-wave signals, science case for high-frequency gravitational-wave detectors.

Frank Tackmann (Theory group, DESY)

This project aims to obtain precise theoretical predictions for kinematic distributions of Higgs and electroweak bosons. It will introduce and eventually further develop modern effective-field-theory techniques to obtain the best possible theoretical precision including reliable estimates of the remaining theoretical uncertainties. The predictions will be compared with experimental measurements to determine important Standard-Model parameters, such as Higgs couplings to quarks, to further constrain residual theory uncertainties, and to constrain possible effects from new physics beyond the Standard Model.

Georg Weiglein (Theory group, DESY)

Theoretical predictions for Higgs physics, taking into account possible effects of physics beyond the Standard Model of particle physics, will be derived. The resulting phenomenological implications will be investigated by confronting the predictions with the latest experimental results.

Jürgen Reuter (Theory group, DESY)

Investigation of the physics potential of future high-energy colliders, specifically muon colliders, but also FCC-hh of models of extended Higgs sectors and Higgs portal models. Specifically, the sensitivity to the triple and quadruple Higgs shall be studied and its interdependence with the sensitivity to the corresponding Yukawa couplings.

Jürgen Reuter (Theory group, DESY)

The project aims at the high-precision description of exclusive photon radiation at future electron-positron (and muon) colliders by methods of collinear factorization and coherent infrared (YFS) resummation. This  includes the development and implementation of corresponding matching procedures for QED resummation with fixed-order calculations. This can be employed to the study of BSM searches where the exact knowledge of exclusive photon distributions is mandatory, like e.g. the search for dark matter or radiatively decaying particles.

Georg Weiglein (Theory group, DESY)

The underlying physics of electroweak symmetry breaking will be investigated by studying Higgs sectors that are extended in comparison to the minimal realisation predicted by the Standard Model of particle physics. The information obtainable at present and future colliders will be analysed in view of the connection of Higgs physics with the electroweak phase transition, possible signals of gravitational waves, and the vacuum structure during the thermal evolution of the early universe.

Géraldine Servant (Theory group, DESY and II. Institute, UHH)

Topics will include Higgs and axion cosmology, early universe, dark matter, baryogenesis, cosmological phase transitions at the electroweak scale and beyond, gravitational-wave signatures of BSM physics, predictions of spectra of primordial origin.

For this position***, it is necessary to also apply on the University of Hamburg portal:

https://www.uni-hamburg.de/en/stellenangebote/formular.html?jobID=862cc609cf0002f7e0e3232601fe8faeb028af29

***
https://www.uni-hamburg.de/stellenangebote/ausschreibung.html?jobID=862cc609cf0002f7e0e3232601fe8faeb028af29

Vicente Cortés (Math department, UHH), Christophe Grojean (Theory group, DESY) and Timo Weigand (II. Institute, UHH)

Effective field theories are a convenient to systematically explore quantum field theory in the presence of a large separation of physical scales, be there the weak scale and the scale of new physics. EFTs can be matched to any specific UV physics scenario but they can also be used to parametrise unknown physics in terms of few coefficients capturing local interactions of know particles. Locality and unitarity actually offer powerful constraints on the values of these coefficients. Consistency with the laws of gravity at the quantum level also impose some non-trivial constraints on these IR coefficients. The aim of this project will be to investigate the geometrical structure of these constraints. The project will be done in collaboration between the theoretical physics at DESY and the Centre for Mathematical Physics of the University of Hamburg.

Volker Schomerus and Jörg Teschner (Theory group, DESY)

The project will study the use of defect observables for understanding non-perturbative effects in supersymmetric QFT. The use of defects as probes in QFT is a very promising recent direction of research due to its potential to reveal hidden symmetries or integrable structures. Depending on the background of the successful candidate, we will either use bootstrap techniques or employ relations to integrable models (or both). The project will introduce to the relevant mathematical techniques such as aspects of harmonic analysis or geometric structures on Riemann surfaces.

Gleb Arutyunov (II. Institute, UHH) and Volker Schomerus (Theory group, DESY)

The calculation of Feynman integrals in an important and challenging problem in perturbative quantum field theory, with applications also to gravitational physics and string theory. In an appropriate parametrisation, Feynman integrals can be written as so-called A-hypergeometric functions. The goal of this project is to explore and exploit the integrability of A-hypergeometric functions to compute new classes of Feynman integrals and to pursue applications in articular to perturbative quantum field theory and the gravitational binary problem.

Elli Pomoni (Theory group, DESY)

Supersymmetry and Conformal invariance are broken when the temperature is turned on. Nonetheless we can still use these broken symmetries to derive Broken Ward identities. Broken Ward identities lead to novel constraints on observables and combined with exact results techniques (which are already successful when the symmetries are unbroken) will allow us to derive exact results at finite temperature. Through the AdS/CFT correspondence these results will have important applications to the modern study of Black hole physics.

Till Bargheer (Theory group, DESY)

The goal of this project is to develop and apply integrability techniques to the computation of observables (correlation functions, Wilson loops, scattering amplitudes) in supersymmetric field theory, and to the corresponding quantities in the dual gravitational (string) theory, thereby probing and illuminating the gauge/gravity duality in the deep quantum regime.

Craig Lawrie (Theory group, DESY)

Geometric engineering of supersymmetric and superconformal field theories from string theory provides a powerful technique to explore features of quantum field theory in terms of geometric properties and features of the compactification space. Recently a vast landscape of 6d SCFTs has been constructed in this way, and many novel and interesting SCFTs in dimensions <6 can be realised from their further compactification (especially interesting are 4d N=1 SCFTs). The geometric approach provides a handle to understanding the strongly-coupled aspects of this class of theories, such as dualities.

Volker Schomerus (Theory group, DESY)

The holographic duality between d-dimensional conformal field theories and string theory in d+1-dimensional Anti-DeSitter space provides an intriguing handle for our understanding of quantum gravity. In this project we want to explore fundamental consistency requirements of the conformal field theory, as captured by the conformal bootstrap, in order to constrain the low energy effective theory of gravity in Anti-deSitter space. In particular, we plan to derive and explore multi-particle dispersive sum rules within d-dimensional conformal field theory.