In this talk, I discuss recent progress in constructing explicit examples of de Sitter vacua at leading order in the \alpha' and g_s expansions as envisioned by Kachru, Kallosh, Linde and Trivedi 20 years ago. Initially, I will specify explicit Calabi-Yau orientifolds, and choices of quantised fluxes leading to exponentially small flux superpotential. I derive the four-dimensional effective supergravity theories, incorporating the leading non-perturbative superpotential terms from Euclidean D3-branes, and the leading corrections to the Kähler potential that are inherited from N=2 supersymmetry. Subsequently, I will demonstrate how warped Randall-Sundrum throats and SUSY breaking uplifts from anti-D3 branes can be incorporated in this construction. Lastly, I will briefly comment on the robustness of the construction against genuinely N=1 corrections in the \alpha’ and g_s expansions which are however not fully known.

The history of the universe between inflation and the onset of BBN - covering half its lifetime on a log scale - is essentially unconstrained by observations. In this talk, I will discuss how general features of String Theory motivate an unusual cosmology in this period, (co-)dominated by the energy density of scalar fields such as moduli and axions. After reviewing the physics of moduli and axions in realistic string compactifications, I will describe how exotic epochs such as kination and trackers can arise in this setting, and present a complete, alternative history of the early universe based on such considerations. In the second part of the talk, I will discuss some observational consequences, and in particular show how perturbation growth in these stringy cosmologies is substantially enhanced compared to the standard ones. If time permits, I will conclude with some applications to baryogenesis, dark matter and gravitational wave production.

Based on 2311.12429, 2401.04064 + work in progress

Symmetries are a powerful tool in the physicist’s toolkit, and when it comes to symmetric functions, rarely can one find functions as symmetric as automorphic forms. What makes certain automorphic forms powerful is their connection to arithmetic, via the theory of L functions. They are core to some of the most challenging and ambitious open problems in modern mathematics, and played a central role for example in the proof of Fermat’s last theorem. These arithmetic structures are valuable to physicists too. The “how” will be addressed in this talk. I will go over what automorphic forms are, how they give rise to arithmetic structures in string theory and quantum field theory, and some applications. Due to the technical nature of this subject, most of it will be an overview with a few new insights and WIP towards the end.

Scale separation is the important phenomenological property for a given vacuum to have an internal compact space much "smaller" than the extended spacetime, so that a lower-dimensional effective description indeed makes sense. At a practical level, this is measured by the decoupling or not of the magnitude of the cosmological constant from the Kaluza-Klein scale. The status of scale separation in AdS vacua obtained from string theory is under debate. On the one hand bottom-up constructions in type IIA string theory seem to achieve this hierarchy of scales parametrically. However on the other hand some Swampland arguments as well as holographic considerations cast a pessimistic shadow on scale separation and about its presence in the Landscape. After an overview of the evolution of scale separation in string theory over the last twenty years, I will present new families of scale separated vacua obtained via a 4d EFT analysis in massless type IIA flux compactifications on elliptic fibrations with metric fluxes. Parametric scale separation is achieved by an asymmetric flux rescaling which, however, in general is not a simple symmetry of the 4d equations of motion. At this level of approximation the vacua are stable but, unlike in the Calabi-Yau case, they display a non-universal mass spectrum of light fields.

The existence of nonbaryonic dark matter (DM) in the Universe is compelling, as suggested by astrophysical and cosmological observations. The most commonly assumed production mechanism for DM in the early universe corresponds to the weakly interacting massive particle (WIMP) paradigm, in which DM has mass and couplings at the electroweak scale. However, the current null experimental results and severe constraints on the natural parameter space are forcing us to search beyond the standard WIMP paradigm. In this talk, I will review alternative DM production mechanisms in the early universe, both thermal and non-thermal, like the FIMP and the SIMP paradigms. The possible impact of alternative non-standard cosmological scenarios will also be analyzed. Finally, experimental avenues for DM detection are discussed.

In this talk I will summarize how duality symmetries of supergravity models can potentially lead to global symmetries. These are associated to deformation classes of spaces with non-trivial duality bundle and classified by so-called bordism groups. Since global symmetries are not allowed for consistent theories of quantum gravity, there need to exist certain objects that break these global symmetries. We will discuss S-duality for type IIB supergravity as well as U-duality for maximal 8d supergravities and explore the necessary symmetry-breaking objects in the various setups.

Elaborating on the recent developments concerning Feynman integrals' calculus and Scattering Amplitudes' evaluation,
I introduce the Intersection Theory for twisted de Rham co-homology, and discuss how Intersection Numbers rule the vector-space structure of special functions, such as Euler-Mellin integrals, appearing in Mathematics and Physics.
Applications in Electromagnetism, Quantum Mechanics,
QFT and Cosmology point to the crucial impact of Intersection Theory on the theory of Fundamental Interactions.

Nearly twenty years ago in an experiment at Brookhaven National Laboratory, physicists measured the muon's anomalous magnetic moment, a_mu, with a remarkable precision of 0.54 parts per million. Since that time, the reference Standard Model prediction for a_mu has exhibited a discrepancy with experiment of over 3 standard deviations, raising the tantalizing possibility of elementary particles or fundamental forces as yet undiscovered. On April 7, 2021 the physicists of an ongoing experiment at Fermilab presented first results of a new measurement of a_mu, brilliantly confirming Brookhaven's measurement and bringing the discrepancy with the reference prediction to a near discovery level of 4.2 sigma. This discrepancy was further enhanced to 5.1 sigma this past with the publication of Fermilab’s new result that reduces the measurement uncertainty by a factor of 2. According to usual particle physics standards, such a discrepancy would mean that new fundamental physics has been uncovered.

In the meantime a very large-scale supercomputer calculation of the contribution that most limits the precision of the Standard Model prediction was performed by the Budapest-Marseille-Wuppertal collaboration. The results of this lattice quantum chromodynamics (QCD) calculation paint a very different picture, in particular reducing the difference between theory and experiment and suggesting that new physics may not be needed to explain the current, experimental, world-average value of a_mu. However, it does so at the expense of an untenable discrepancy with the data-driven determination of this most uncertain contribution.

After an introduction and a discussion of the current experimental and theoretical status of a_mu, I will present this precise lattice QCD calculation and partial confirmations by other teams. I will also present a framework that enables a comparison of the primary ingredients that are used in the lattice QCD and data-driven approaches and discuss the steps that are required to make a Standard Model prediction that will allow determine whether the final results of the Fermilab experiment, expected in 2025, indicate the presence of new fundamental physics.