Effective theory models from string theory: implications in particle physics and cosmology
Mar 11, 2025Citations per year
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Abstract: (didaktorika.gr)
This thesis aims to provide a better understanding of the moduli stabilization mechanisms in string theory and the phenomenological consequences of Grand Unified Theories (GUTs) in the framework of F-theory. In the first section, a review of the Standard Model is provided along with the open problems in high energy physics and cosmology. Moreover, the most promising solutions for the Kähler moduli stabilization problem are analyzed, along with the basic geometric tools for constructing local F-theory GUTs. In the next chapter, the analysis of perturbative moduli stabilization with D7 is presented, where the logarithmic string loop corrections are added to the Kähler potential complementing the contributions of non-perturbative corrections to the superpotential. We show that de Sitter (dS) vacua are accessible to the low-energy effective theory due to the uplifting effects of the D-terms, emerging from the magnetic fluxes in the D7 branes context. In addition, more complex geometric compactifications are discussed exhibiting the universal effect of the loop corrections to the search for dS vacua beyond the simple toroidal-like volumes. Apart from the stabilization conditions, a model of dark radiation and dark matter is suggested, where the moduli decay into closed string axions, comprising the dark radiation of the universe. Additionally, moduli decays to the dark sector degrees of freedom could in principle produce the correct dark matter abundance. From the F-theory perspective, two different GUTs are presented. In the first attempt, a flipped SU(5) is constructed in the spectral cover approach, where right handed and sterile neutrinos are augmented to explain the tiny mass of the left handed partners. Furthermore, phenomenological issues like proton decay, 0νββ decay and g-2 are explained, in light of the new symmetry breaking scales introduced in the model. Finally, an F-theory SU(5) model is examined, pointing towards the emergence of a flavor family symmetry from internal fluxes. The complex structure moduli of the geometry's tori are laid stabilized to specific non-linear paths due to G3 fluxes, resulting in the breaking of the SL(2,Z) symmetry down to a congruence subgroup Γ(Ν). Based on the above, an SU(5) x S4 is utilized to explain the Yukawa matrices in both the quark and the neutrino sector, where the whole setup is parametrized by the values of the moduli. In the last chapter, a conclusion is outlined sketching the prospects for future expansions.- String theory and cosmology
- F-theory
- Grand unified theories
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