Schedule for: 21w5171 - Strings: Geometry and Symmetries for Phenomenology (Online)

Extremal black holes play a key role in our understanding of various swampland conjectures and in particular the Weak Gravity Conjecture (WGC). In this talk, I will focus on the mild form of the WGC which states that extremal black holes themselves are the states that satisfy it. This is possible because higher-derivative corrections shift the extremality bound of black holes and, depending on the sign of the Wilson coefficients, increase the charge-to-mass ratio of an extremal black hole. Using the Iyer-Wald formalism I will present an elegant method to compute corrections to extremal black holes. This approach is universal and can be applied to a wide class of black hole solutions. I will show that in this formalism, the mild form of the WGC can be understood in terms of positivity properties of the stress tensor of the perturbation. Finally, I will comment on a recent formulation of the WGC in the context of the AdS/CFT correspondence.

Miguel Montero shall share his views and ideas on the progress of the swampland program. This session will be moderated by Nana Cabo-Bizet. This space is conceived to trigger a rich discussion among all participants of the workshop.

One of the most important swampland conditions is the presence of infinite towers of states becoming massless at the weak coupling/large field limits. This has been extensively tested in string theory compactifications, but a bottom-up explanation was missing. In this talk I will provide a possible explanation based on finiteness of black hole entropy. I will also explain how several swampland criteria, including the Weak Gravity Conjecture, Distance Conjecture and bounds on the finiteness of the quantum gravity vacua, may be more fundamentally a consequence of the finiteness of quantum gravity amplitudes.

I study low-energy effective field theory derived from string compactifictions. I show a specific structure among couplings, and then compare it with the minimal flavor violation scenario in the SMEFT. In this effective field theory, the modular symmetries are important. I review some aspects of modular symmetries.

Ignatios Antoniadis, Luis Ibáñez and Peter Nilles shall share their views and ideas on the progress of string phenomenology.

String phenomenology concerns the question of relating string theory to observation. Ideally, one would be able to construct a stringy version of the standard model of particle physics and make unequivocal predictions that can be tested eventually. The standard model leaves many questions unanswered, yet the bulk of its free parameters resides in the so-called flavor sector. In this talk some developments are described that conceivably may provide us with an understanding of the observed violation of CP, as well as the so-called modular flavor symmetries which promise a predictive description of fermion masses. The current status of implementing these developments in explicit string models will be reported. Finally, possible loopholes in previous model scans will be discussed using the example of "fermion flow", which refers to the possibility that the true number of generations may differ from its tree-level value.

Multifield inflation arises naturally in string theory and supergravity models. When several scalars are active during inflation, the eta-problem may be circumvented, while new trajectories with large turns can arise, with interesting observational consequences. When gauge field spectators are also present, these may source gravitational waves, enhancing the primordial gravitational wave spectrum. I will discuss the prospects of realising these features in supergravity and string theory models of inflation.

Shamit Kachru and Fernando Quevedo shall share their views and ideas on the progress of string cosmology. This session will be moderated by Liam McAllister. This space is conceived to trigger a rich discussion among all participants of the workshop.

I will discuss different theoretical and phenomenological challenges of quintessence model building in string theory in order to be able to give an informed answer to the question in the title.

In the first part of the talk, I will explain how to leverage neural networks to approximate Calabi-Yau or SU(3) structure metrics. We vastly extend previous work in this area to provide approximations for any Kreuzer-Skarke (KS) Calabi-Yau or CICY. While extensions to CICYs are rather straightforward, toric varieties require more work. I will first explain how to obtain the (non-Ricci-flat) analog of the Fubini-Study metric for KS models, and then how to sample points uniformly from these spaces using a powerful mathematical theorem. In the second part, I will explain how these metrics can be used to explicitly check the swampland distance conjecture by computing masses of moduli-dependent string excitations. In doing so, we make a curious observation that relates properties of the spectrum of the Laplace operator to symmetries of the compactification manifold.

Jim Halverson, Vishnu Jejjala and Andre Lukas shall share their views and ideas on the progress of the applications of machine learning for string theory. This session will be moderated by Oscar Loaiza-Brito. This space is conceived to trigger a rich discussion among all participants of the workshop.

Ricci flat metrics for Calabi-Yau threefolds are not known analytically. In this talk, I discuss techniques from machine learning to deduce numerical flat metrics for K3, the Fermat quintic, and the Dwork quintic. This investigation employs a simple, modular neural network architecture that is capable of approximating Ricci flat Kaehler metrics for Calabi-Yau manifolds of dimensions two and three. We show that measures that assess the Ricci flatness and consistency of the metric decrease after training. This improvement is corroborated by the performance of the trained network on an independent validation set. Finally, we demonstrate the consistency of the learnt metric by showing that it is invariant under the discrete symmetries it is expected to possess.

A rich class of d-dimensional field theories arises when placing M-theory on codimension (11-d) singularities. I will discuss how (d+1)-dimensional topological field theories (TQFTs) encode the (higher) symmetries and anomalies of these d-dimensional theories, and how these TQFTs can be extracted from the geometry of the singular space. I will illustrate the discussion by analysing some simple examples explicitly.

Washington Taylor and Albrecht Klemm shall share their views and ideas on the progress of geometry in string theory. This session will be moderated by Anamaría Font. This space is conceived to trigger a rich discussion among all participants of the workshop.

The first part of the talk will overview some no-go results on the string landscape. The second part of the talk will describe a way to potentially evade those no-go results by building non-classical string solutions. Specifically, I will outline a strategy to construct a family of non-supersymmetric AdS solutions where various swampland conjectures can be examined.