Axio-Dilaton Dark Energy: A Dynamical Systems and Bayesian Inference Analysis

Mario Ramos-Hamud; Gabriela García-Arroyo; Fernando Quevedo; J. Alberto Vázquez

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arXiv · 2609.22539

Axio-Dilaton Dark Energy: A Dynamical Systems and Bayesian Inference Analysis

Mario Ramos-Hamud·Gabriela García-Arroyo·Fernando Quevedo·J. Alberto Vázquez

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Abstract

We initiate a systematic cosmological investigation of an axio-dilaton system governed by a curved field-space metric as generically motivated by supergravity and string compactifications. The scalar sector consists of a light scalar dilaton field evolving along an asymptotically exponential potential and a pseudoscalar field spanning an essentially flat direction, kinetically coupled through an exponential field-space metric. Deviations from the asymptotic regime are incorporated by introducing a generalised Albrecht-Skordis potential containing a polynomial factor. Utilising a dynamical systems approach alongside numerical evolution and Bayesian inference, we constrain the model using Type Ia Supernovae (SNe Ia), Baryon Acoustic Oscillations (BAO) and Planck 2018 distance-prior data. We identify a parameter degeneracy indicating that steeper potentials demand stronger field-space kinetic couplings to sustain late-time cosmic acceleration. Finally, a joint likelihood analysis reveals that while the model successfully accounts for dark energy dynamics, it is only slightly statistically favoured over $Λ$CDM by current observations.

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Mario Ramos-Hamud, Gabriela García-Arroyo, Fernando Quevedo, J. Alberto Vázquez. 2026-09-18. Axio-Dilaton Dark Energy: A Dynamical Systems and Bayesian Inference Analysis. https://arxiv.org/abs/2609.22539

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