Research in Quantum Gravity
Finding Quantum Gravity traces in our Universe
More than a decade ago, the dominant approach to explaining the Physics of our Universe from String Theory was of top-down nature. Namely, the question that was asked was:
can String Theory deliver a four-dimensional model that correctly explains the Physics of our Universe, ranging from inflation, to subatomic phenomena?
Answering such a question proved to be hard, for String Theory predicts too many four-dimensional models, and it is hard to systematically study them and check their consistency with the Physics that we observe. Thus, in the recent years, the question has been reversed, and the problem of consistency has been rather formulated in a bottom-up fashion. Indeed, the question that is now asked is:
given a four- dimensional effective field theory, which characteristics should it be endowed with in order to actually originate from String Theory?
Those theories that can be ‘completed’ within String Theory are said to belong to the Landscape of consistent effective theories, while those that are not are said to be part of the Swampland. The boundaries that separate the Landscape of effective theories from the Swampland are governed by the so-called Swampland Conjectures. These are general criteria that aim at identifying the signatures that Quantum Gravity, or String Theory leaves within lower-dimensional effective field theories. As the name suggests, almost all the criteria proposed are conjectural: they have been checked in several scenarios, but they are devoid of any mathematical proof that could demonstrate their general validity.
My main contributions to the progress of the Swampland program include:
1. Characterizing the Swampland at the boundaries of the field space
I contributed to a better understanding of how extended objects (in particular, strings and membranes) can enter the formulation of the Swampland Conjectures in the following work:
- Swampland Conjectures for Strings and Membranes
Stefano Lanza, Fernando Marchesano, Luca Martucci, Irene Valenzuela
Published in: JHEP 02 (2021) 006
PDF, arXiv, INSPIRE-HEP
In a subsequent work, we showed that such objects play a pivotal role in the characterization of the (pathological) Physics that emerge towards some field space boundaries:
- The EFT stringy viewpoint on large distances
Stefano Lanza, Fernando Marchesano, Luca Martucci, Irene Valenzuela
Published in: JHEP 02 (2021) 006
PDF, arXiv, INSPIRE-HEP
2. Understanding the geometrical structures that define the String Landscape
During my postdoctoral appointment at Utrecht University, with the supervision of Prof. Thomas Grimm, I got interested in the application of forefront mathematical research in the investigation of effective field theories that originate from String Theory. In this work:
- Tameness, Strings, and the Distance Conjecture
Thomas W. Grimm, Stefano Lanza, Chongchuo Li
Published in: JHEP 09 (2022) 149
PDF, arXiv, INSPIRE-HEP
we first showed how tame geometry and o-minimal structures can help better understand some geometrical structures of consistent effective field theories. Indeed, we illustrated that considering tame geometry might be crucial for a proper formulation of the Swampland Conjectures.