Cosmological consequences of a scalar field with oscillating equation of state: A possible solution to the fine-tuning and coincidence problems

Abstract

We propose a new dark energy model for solving the cosmological fine-tuning and coincidence problems. A default assumption is that the fine-tuning problem disappears if we do not interpret dark energy as vacuum energy. The key idea to solving the coincidence problem is that the Universe may have several acceleration phases across the whole cosmic history. The specific example we study is a quintessence model with approximately repeated double exponential potential, which only introduces one Planck scale parameter and three dimensionless parameters of order unity. The cosmological background evolution equations can be recast into a four-dimensional dynamical system and its main properties are discussed in details. Preliminary calculations show that our model is able to explain the observed cosmic late-time acceleration.

7 pages, 3 figures, matches published version

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• Smoothing the $H_0$ tension with a dynamical dark energy model
• Cosmological constraints on dynamical dark energy model in $F(Q)$ gravity
• Oscillating dark energy in light of the latest observations and its impact on the Hubble tension
• Dynamical aspects for scalar fields coupled to cubic contractions of the Riemann tensor
• Inflation and the cosmological (not-so) constant in unimodular gravity
• Cosmological model with linear equation of state parameter in f(R, Lm) gravity
• Time evolution of the local gravitational parameters and gravitational wave polarizations in a relativistic MOND theory
• Cosmological consequences of a scalar field with oscillating equation of state. II. Oscillating scaling and chaotic accelerating solutions
• Cosmological consequences of a scalar field with oscillating equation of state. III. Unifying inflation with dark energy and small tensor-to-scalar ratio
• Cosmological consequences of a scalar field with oscillating equation of state. IV. Primordial nucleosynthesis and the deuterium problem
• Gravitation with modified fluid Lagrangian: Variational principle and an early dark energy model
• Gravitational Field of a Rotating Mass on an Expanding Universe
• Production of Primordial Gravitational Waves in Teleparallel Gravity
• Testing the Anton-Schmidt dark energy model with the DESI DR2 measurements
• Constraints on the Modified Emergent Dark Energy Model Using DESI DR2 BAO