String theory allows for huge classes of possible models admitting a gravitational lowenergy effective description. However, not any effective field theory (EFT) of gravity admits a string theory UV completion. By using string theory as the main theoretical laboratory, the “Swampland program” aims at identifying the hallmarks distinguishing the “landscape” of gravitational EFTs that admit a consistent UV completion from the “swampland” of seemingly consistent EFTs that do not. In this context, it has been recently realized that the perturbative regimes of UV complete fourdimensional N=1 (i.e. minimally supersymmetric) EFTs are strongly characterized by the presence of specific types of fundamental strings, called EFT strings. The latter generically support an 'internal' worldsheet sector, besides the universal 'center of mass' sector, and it is currently unknown how to couple it to the bulk supergravity sector in a supersymmetrically controlled way. In this thesis, we illustrate how the universal sector of EFT strings can be coupled to fourdimensional N=1 supergravities by appropriately generalizing the superembedding formulation of superstrings. This provides a promising starting point to add the internal worldsheet sector. In this respect, we first study in depth the N=(0,2) twodimensional supergravity. We finally give a first example of inclusion of the internal sector, considering N=(0,2) Fermi multiplets and N=(0,2) chiral multiplets. In the latter case, we show that a generalization of the superembedding condition is needed, leaving the investigation of this interesting aspect for future work.
Worldsheet dynamics of EFT strings
GUGLIELMELLI, MATTIA
2021/2022
Abstract
String theory allows for huge classes of possible models admitting a gravitational lowenergy effective description. However, not any effective field theory (EFT) of gravity admits a string theory UV completion. By using string theory as the main theoretical laboratory, the “Swampland program” aims at identifying the hallmarks distinguishing the “landscape” of gravitational EFTs that admit a consistent UV completion from the “swampland” of seemingly consistent EFTs that do not. In this context, it has been recently realized that the perturbative regimes of UV complete fourdimensional N=1 (i.e. minimally supersymmetric) EFTs are strongly characterized by the presence of specific types of fundamental strings, called EFT strings. The latter generically support an 'internal' worldsheet sector, besides the universal 'center of mass' sector, and it is currently unknown how to couple it to the bulk supergravity sector in a supersymmetrically controlled way. In this thesis, we illustrate how the universal sector of EFT strings can be coupled to fourdimensional N=1 supergravities by appropriately generalizing the superembedding formulation of superstrings. This provides a promising starting point to add the internal worldsheet sector. In this respect, we first study in depth the N=(0,2) twodimensional supergravity. We finally give a first example of inclusion of the internal sector, considering N=(0,2) Fermi multiplets and N=(0,2) chiral multiplets. In the latter case, we show that a generalization of the superembedding condition is needed, leaving the investigation of this interesting aspect for future work.File  Dimensione  Formato  

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https://hdl.handle.net/20.500.12608/41606