Bouncing Bianchi Type I Universes with Interacting Vacuum
Abstract
We investigate the global dynamics and cosmological viability of non-singular solutions in an anisotropic Bianchi type I universe featuring an interacting vacuum energy component V and a perfect fluid ρ, extending previous work based on a Robertson-Walker geometry. By modeling the energy-momentum transfer via a phenomenological four-vector Qμ, we reduce the field equations to a four-dimensional autonomous dynamical system for the expansion rate Θ, total shear σ, energy density ρ, and vacuum component V. We examine two distinct forms for how the interaction depends on ρ and V: a linear coupling Q1 ∝ Θ[ξ(VΛ− V) + χρ] and a non-linear coupling Q2 ∝ Θρ(1 − V/VΛ). Using a potential-energy analogy and phase-space analysis, we show that the linear model Q1 naturally admits non-singular bouncing trajectories. In contrast, unlike the Robertson-Walker case, for the non-linear interaction Q2, invariant boundary surfaces in phase space strictly constrain the domain of expansion ruling out cosmological bounce scenarios for physical matter configurations.
Related
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- Satellite stellar-to-halo mass relations in primordial black hole universes
- Exploring the scenarios of non-singular bouncing cosmology in f(Q,Lm) gravity
BibTeX
@misc{bruni2026bouncing,
title = {{Bouncing Bianchi Type I Universes with Interacting Vacuum}},
author = {Marco Bruni and Rodrigo Maier and Thomas Waters},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.20357},
eprint = {2610.20357},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.20357},
}
RIS
TY - UNPB
TI - Bouncing Bianchi Type I Universes with Interacting Vacuum
AU - Marco Bruni
AU - Rodrigo Maier
AU - Thomas Waters
PY - 2026
DA - 2026/10/14
PB - arXiv
DO - 10.48550/arxiv.2610.20357
UR - https://arxiv.org/abs/2610.20357
AB - We investigate the global dynamics and cosmological viability of non-singular solutions in an anisotropic Bianchi type I universe featuring an interacting vacuum energy component V and a perfect fluid ρ, extending previous work based on a Robertson-Walker geometry. By modeling the energy-momentum transfer via a phenomenological four-vector Q_μ, we reduce the field equations to a four-dimensional autonomous dynamical system for the expansion rate Θ, total shear σ, energy density ρ, and vacuum component V. We examine two distinct forms for how the interaction depends on ρ and V: a linear coupling Q_1 ∝ Θ[ξ(V_Λ− V) + χρ] and a non-linear coupling Q_2 ∝ Θρ(1 − V/V_Λ). Using a potential-energy analogy and phase-space analysis, we show that the linear model Q_1 naturally admits non-singular bouncing trajectories. In contrast, unlike the Robertson-Walker case, for the non-linear interaction Q_2, invariant boundary surfaces in phase space strictly constrain the domain of expansion ruling out cosmological bounce scenarios for physical matter configurations.
ER -