title: Analytical and Numerical Methods for High-Precision Studies in Ultrarelativistic Strong-Field Quantum Electrodynamics creator: Montefiori, Samuele subject: ddc-530 subject: 530 Physics description: This thesis presents a comprehensive exploration of both analytical and numerical techniques used to model processes in ultrarelativistic strong-field quantum electrodynamics (SFQED). % We developed SFQEDtoolkit, an open-source library that employs advanced function approximation techniques to accurately model nonlinear Compton (NIC) emission and nonlinear Breit-Wheeler (NBW) pair creation processes. % Simulations combining particle-in-cell (PIC) codes with SFQEDtoolkit have been used to investigate collisions between ultrarelativistic dense electron beams and plasma targets, demonstrating that electron-positron jets exceeding solid densities can be produced within self-generated magnetic fields up to 10 MT. % These findings reveal a novel regime where SFQED, atomic, and plasma physics are intrinsically interwoven, opening a new avenue of research in SFQED. % Furthermore, we derive analytical expressions for NIC and NBW differential distributions that describe the energy, angular, spin, and polarization characteristics of the produced particles. % Notably, the derivation of these distributions, following state-of-the-art methodologies, yields results that can give negative values over certain parameter intervals, undermining their probabilistic interpretation. % We demonstrate that integrating these distributions over the ``formation time'' of the quantum process restores their conventional physical meaning. % Overall, the contributions of this thesis advance the analytical and numerical modeling of SFQED processes, providing a robust framework for forthcoming experimental studies of SFQED, which are critically relevant for extreme-field plasma physics and the microphysics of pulsars and magnetars. date: 2025 type: Dissertation type: info:eu-repo/semantics/doctoralThesis type: NonPeerReviewed format: application/pdf identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/36586/5/Samuele%20Montefiori%20-%20PhD%20thesis.pdf format: application/pdf identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/36586/15/erratum.pdf identifier: DOI:10.11588/heidok.00036586 identifier: urn:nbn:de:bsz:16-heidok-365864 identifier: Montefiori, Samuele (2025) Analytical and Numerical Methods for High-Precision Studies in Ultrarelativistic Strong-Field Quantum Electrodynamics. [Dissertation] relation: https://archiv.ub.uni-heidelberg.de/volltextserver/36586/ rights: info:eu-repo/semantics/openAccess rights: http://archiv.ub.uni-heidelberg.de/volltextserver/help/license_urhg.html language: eng