Interacting dark sector from the trace-free Einstein equations: cosmological perturbations with no instability

Abstract

In trace-free Einstein gravity, the stress-energy tensor of matter is not necessarily conserved and so the theory offers a natural framework for interacting dark energy models where dark energy has a constant equation of state $w=-1$. We derive the equations of motion for linear cosmological perturbations in interacting dark energy models of this class, focusing on the scalar sector. Then, we consider a specific model where the energy-momentum transfer potential is proportional to the energy density of cold dark matter; this transfer potential has the effect of inducing an effective equation of state $w_{\mathrm{eff}}\ne 0$ for cold dark matter. We analyze in detail the evolution of perturbations during radiation domination on super-Hubble scales, finding that the well-known large-scale instability that affects a large class of interacting dark energy models is absent in this model. To avoid a gradient instability, energy must flow from dark matter to dark energy. Finally, we show that interacting dark energy models with $w=-1$ are equivalent to a class of generalized dark matter models.

arXiv comment23 pages + references; accepted for publication in PRD

References in corpus (39)

• In the Realm of the Hubble tension $-$ a Review of Solutions
• Cosmological Perturbation Theory in the Synchronous and Conformal Newtonian Gauges
• Cosmological Perturbation Theory in the Synchronous vs. Conformal Newtonian Gauge
• Cosmological perturbations
• Dark Matter and Dark Energy Interactions: Theoretical Challenges, Cosmological Implications and Observational Signatures
• Structure Formation with Generalized Dark Matter
• Large-scale instability in interacting dark energy and dark matter fluids
• On the Trace-Free Einstein Equations as a Viable Alternative to General Relativity
• Dark energy as the weight of violating energy conservation
• The General Primordial Cosmic Perturbation
• Baryon bias and structure formation in an accelerating universe
• Constraining Dark Energy Dynamics in Extended Parameter Space
• Observational constraints on an interacting dark energy model
• Interacting Dark Energy -- constraints and degeneracies
• The Growth of Structure in Interacting Dark Energy Models
• Constraints on the interacting vacuum -- geodesic CDM scenario
• The Parameterized Post-Friedmannian Framework for Interacting Dark Energy Theories
• Adiabatic initial conditions for perturbations in interacting dark energy models
• Dark calling Dark: Interaction in the dark sector in presence of neutrino properties after Planck CMB final release
• Inhomogeneous vacuum energy
• Cosmological constraints on parametrized interacting dark energy
• Cosmological Perturbations in Unimodular Gravity
• Dark energy from quantum gravity discreteness
• Unimodular quantum gravity and the cosmological constant
• Weighing neutrinos in the scenario of vacuum energy interacting with cold dark matter: application of the parameterized post-Friedmann approach
• Resolving the $H_0$ tension with diffusion
• Understanding the suppression of structure formation from dark matter$\unicode{x2013}$dark energy momentum coupling
• The path integral of unimodular gravity
• Constraining dark matter properties with Cosmic Microwave Background observations
• Cosmic acceleration in unimodular gravity
• An extensive investigation of the Generalised Dark Matter model
• Dark Matter properties through cosmic history
• New Weyl-invariant vector-tensor theory for the cosmological constant
• Can quantum fluctuations differentiate between standard and unimodular gravity?
• Diffusion in unimodular gravity: Analytical solutions, late-time acceleration, and cosmological constraints
• Cosmological perturbation of Unimodular Gravity and General Relativity are identical
• Nonconservative unimodular gravity: a viable cosmological scenario
• Inflation and the cosmological (not-so) constant in unimodular gravity
• Qualitative dynamics of interacting vacuum cosmologies

Cited by in corpus (13)

• The CosmoVerse White Paper: Addressing observational tensions in cosmology with systematics and fundamental physics
• Dark matter solution to the $H_0$ and $S_8$ tensions, and the integrated Sachs-Wolfe void anomaly
• Reconciling $S_8$: Insights from Interacting Dark Sectors
• A clarification on prevailing misconceptions in unimodular gravity
• Planckian discreteness as seeds for cosmic structure
• Cosmological constant as an integration constant
• Reconstruction of inflationary scenarios in non-conservative unimodular gravity
• Climbing over the potential barrier during inflation via null energy condition violation
• Stochastic dark matter: Covariant Brownian motion from Planckian discreteness
• Higgs Inflation in Unimodular Gravity
• Charged thin shells in unimodular gravity
• Probing Interacting Dark Sectors with upcoming Post-Reionization and Galaxy Surveys
• Spherical thin shells with charge in unimodular gravity