arXiv subjects

Vasileios Basiouris

Publications and source records attributed to Vasileios Basiouris.

7 recordsLinked to original sources

arXiv2026

Thermal effects and finite-temperature cosmology in perturbatively stabilized large volume scenarios

We analyze finite-temperature effects in the perturbative Large Volume Scenario (LVS), examining the dynamics of thermalized K\"ahler moduli and the stability of thermally induced vacua. We determine the maximum decompactification temperature $T_{\max}$, showing its dependence on winding-loop corrections in the effective theory. Moduli stabilization arises from perturbative logarithmic loop corrections to the K\"ahler potential, with higher-derivative $F^4$ terms used to test vacuum robustness. We derive cosmological implications, including bounds on reheating, and show that the model favors high scale inflationary scenarios with the heavy modulus decaying before dominating the energy density of the universe. We also analyze thermal metastability, demonstrating that the recovery of the $T=0$ vacuum is sensitive to the post-inflationary thermal history, potentially yielding either an AdS vacuum, a metastable phase, or a stable dS configuration. We conclude by briefly discussing the relevance of finite-temperature effects for entropy-assisted tunneling and the broader string landscape.

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arXiv2025

Three-Field String Inflation with Perturbative Corrections: Dynamics and Implications

In this work, we construct an explicit string motivated example of three-field inflation in a related, yet distinct from, the recently discovered perturbative large volume scenario (pLVS). Contrary to the usual constructions, in this set up, large volume is ensured by the interplay between the effects of $\alpha^{\prime 3}$, logarithmic loop and higher derivative $F^4$ corrections. After addressing a full moduli stabilization scenario, we move on to a detailed analysis of three-field model of inflation in a canonical basis. We conduct multiple consistency checks to establish a solid foundation for our model within the framework of the underlying 4D effective field theory (EFT). Our model differs from previous setups in three key aspects: first, the interaction between subleading corrections that drive full moduli stabilization follows a different pattern, second, the volume form of the underlying Calabi-Yau is different, and third, in our three-field inflation scenario, the second slow-roll parameter consistently dominates over the first by several orders of magnitude. The latter signals the possible presence of primordial features which can be verified by forthcoming ground and space based experiments. We can roughly distinguish two stages of inflation: the first stage mostly occurs in the steepest direction during horizon crossing giving us almost $55$ efolds of inflation -- once one of the inflatons falls off the ridge and then to its true minimum, the other two fields become active, giving us a truly multi-field behavior in the second stage -- adding few more efolds of inflation. We also confirm our claim by introducing the non-planar torsion in the inflationary trajectory -- this quantity becomes non-trivial in the second stage of inflation. Finally, we calculate the cosmological observables, which align with Planck data, and discuss potential directions for future research.

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arXiv2024

String loop origin for dark radiation and superheavy dark matter in type IIB compactifications

In this article we study the significance of string loop corrections, in a perturbative moduli stabilization scenario, focusing on their role in unraveling the origin of dark radiation in the late cosmological epoch and their correlation to dark matter. More specifically, a detailed analysis is provided in which the mass hierarchy of the normalized fields in the K{\"a}hler moduli sector is determined by the scales of the integer fluxes and the quantum corrections. Furthermore, we compute the previously underestimated contributions to the decay rates of moduli to axions, which behave as dark radiation, highlighting their connection to the aforementioned higher-order corrections. Two contrasting reheating scenarios (low-scale and high-scale) are provided, depending on the decay rate of the longest-lived particle into the Standard Model degrees of freedom through a Giudice-Masiero mechanism, while the effective number of neutrino species $\Delta N_{eff}$ remains below the respective bounds. Finally, a non-thermal dark matter scenario is proposed based on the decays of heavy scalar fields, where the main production mechanisms are investigated, leading to a dark matter candidate mass ranging from a few $GeV$ up to $10^{12}\; GeV$.

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arXiv2024

Modular Family Symmetry in Fluxed GUTs

We discuss modular family symmetry in effective theories based on generic properties of bottom-up local F-theory inspired GUTs broken by fluxes, which we refer to as Fluxed GUTs. We argue that the Yukawa couplings will depend on the complex structure moduli of the matter curves in such a way that they can be modular forms associated with these symmetries. To illustrate the approach we analyse in detail a concrete local fluxed $SU(5)$ GUT with modular $S_4$ family symmetry.

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arXiv2022

Sterile neutrinos, $0νββ$ decay and the W-boson mass anomaly in a Flipped $SU(5)$ from F-theory

We investigate the low energy properties of an effective local model with flipped $SU(5)\times U(1)_χ$ gauge group, constructed within the framework of F-theory. Its origin is traced back to the $SO(10)$ symmetry -- associated with a geometric singularity of the compactification manifold -- broken by an internal flux which is turned on along the seven-brane in the $U(1)_χ$ direction. Topological properties and the choice of flux parameters determine the massless spectrum of the model to be that of the minimal flipped $SU(5)$ supplemented with an extra right-handed electron-type state and its complex conjugate, $E^c+\bar E^c$, as well as neutral singlet fields. The subsequent symmetry breaking to the $SU(3)\times SU(2)\times U(1)_Y$ gauge group occurs with a Higgs pair in $10+\overline{10}$ representations of $SU(5)$. Next we proceed to the phenomenological analysis of the resulting effective model and the salient outcomes are: The $E^c+\bar E^c$ pair acquires a mass of few TeV and as such could solve the $g_μ-2$ discrepancy. Neutrino couplings to extra neutral singlets lead to an inverse seesaw mechanism where an extra light state could be a suitable dark matter candidate. The predictions of the model for the ${0ν}ββ$ decay rate could be tested in near future experiments. There are non-unitarity deviations from lepton mixing matrix ($U_{PMNS}$), which could in principle explain the new precision measurement of the W-boson mass recently reported by CDF II collaboration.

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arXiv2021

Remarks on the effects of quantum corrections on moduli stabilization and de Sitter vacua in type IIB string theory

The rôle of string loop corrections on the existence of de Sitter vacua and the moduli stabilization problem is examined in type IIB effective theories. The fundamental building blocks are a minimum of three intersecting D7 brane stacks, three Kähler moduli, and a novel Einstein-Hilbert term associated with higher derivative terms of the 10-dimensional effective action. It was shown in previous works that loop corrections appear which induce novel logarithmic volume-dependent terms in the effective potential. When D-term contributions are considered, all Kähler moduli are stabilized and de Sitter vacua are achieved. In the present work, a comprehensive study of multiple non-perturbative terms in the superpotential is undertaken. The combined effects of the logarithmic loop corrections and two non-perturbative superpotential Kähler moduli dependent terms have been investigated. It is shown that a variety of fluxes exist for large as well as moderate volume compactifications which define a de Sitter space and stabilize the moduli fields. For large volumes, a generic simple form of the potential is achieved. The so obtained effective potential appears to be promising for cosmological applications.

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arXiv2020

Note on de Sitter vacua from perturbative and non-perturbative dynamics in type IIB/F-theory compactifications

The properties of the effective scalar potential are studied in the framework of type IIB string theory, taking into account perturbative and non-perturbative corrections. The former modify the Kähler potential and include $α'$ and logarithmic corrections generated when intersecting D7 branes are part of the internal geometric configuration. The latter add exponentially suppressed Kähler moduli dependent terms to the fluxed superpotential. The possibility of partial elimination of such terms which may happen for particular choices of world fluxes is also taken into account. That being the case, a simple set up of three Kähler moduli is considered in the large volume regime, where only one of them is assumed to induce non-perturbative corrections. It is found that the shape of the F-term potential crucially depends on the parametric space associated with the perturbative sector and the volume modulus. De Sitter vacua can be obtained by implementing one of the standard mechanisms, i.e., either relying on D-terms related to $U(1)$ symmetries associated with the $D7$ branes, or introducing $\overline{D3}$ branes. In general it is observed that the combined effects of non-perturbative dynamics and the recently introduced logarithmic corrections lead to an effective scalar potential displaying interesting cosmological and phenomenological properties.

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