51ÁÔÆæÈë¿Ú

Abstract:

We explore the dynamics of the fermion-rotor system, a simple impurity model in d = 1 +1 dimensions consisting of a collection of purely right-moving fermions interacting with a quantum mechanical rotor localised at the origin. This was first introduced by Polchinski as a toy model for monopole-fermion scattering and is surprisingly subtle, with ingoing and outgoing fermions carrying different quantum numbers. We show that the rotor acts as a twist operator in the low-energy theory, changing the quantum numbers of excitations that have previously passed through the origin to ensure scattering consistent with all symmetries. We further show how generalisations of this model with multiple rotors and unequal charges can be viewed as a UV-completion of boundary states for chiral theories, including the well-studied 3450 model. We compute correlation functions between ingoing and outgoing fermions, and show that fermions dressed with the rotor degree of freedom act as local operators and create single-particle states, generalizing an earlier result obtained in a theory with a single rotor and equal charges. Finally, we point out a mod 2 anomaly in these models that descends from the Witten anomaly in 4d.

Abstract:

Astrophysical and cosmological observations strongly support the existence of Dark Matter (DM). In this study, we investigate the potential of the mono-Higgs plus missing transverse energy signature at the LHC to search for a fermionic DM candidate using the framework of Effective Field Theory. In our study, the DM interacts with the Standard Model (SM) via dimension-6 and dimension-7 effective operators involving the Higgs and the gauge bosons. Although our analysis is independent of any Ultra Violet complete dynamics of DM, such interactions can be realized in an extension of the SM where the gauge group is extended minimally by adding an extra U (1). Boosted Decision Tree (BDT) discriminators are used to estimate and optimize the signal sensitivity over the SM backgrounds, assuming an integrated luminosity of 3000fb^−1 at s=14 TeV at the High Luminosity phase of the LHC (HL-LHC). In the most optimistic scenario, a significance exceeding 3 σ can be achieved for relic masses ranging from 90 to 300 GeV, which showcases the prospects of the search at the HL-LHC. This study provides a foundation for future explorations in this direction.

Abstract:

Vector bundle cohomology represents a key ingredient for string phenomenology, being associated with the massless spectrum arising in string compactifications on smooth compact manifolds. Although standard algorithmic techniques exist for performing cohomology calculations, they are laborious and ill-suited for scanning over large sets of string compactifications to find those most relevant to particle physics. In this article (based on the second author’s lecture at the Nankai Symposium, August 2021) we review some recent progress in deriving closed-form expressions for line bundle cohomology and discuss some applications to string phenomenology.

Abstract: