The Evolution of dark energy in a gas of thin closed tubes of a massless scalar field, radially changing their size.

Observational indications of a possible complex two-phase evolution of dark energy obtained within the framework of DESI DR2 actualize the search for cosmological models capable of realizing the transition through the phantom barrier and, at the same time, capable of eliminating the theoretical problems associated with the violation of the weak energy condition in the phantom regime. In addition to multicomponent scalar field models and modified gravity models, the two-phase evolution of dark energy can also be realized by “simple” (one-component) scalar field models that are based on the standard General Theory of Relativity, provided that these models can simultaneously realize several mechanisms of accelerated expansion. Models with this property include the gas of thin tubes of a massless scalar field (TToMSF). In the simplest version, the homogeneous phase of TToMSF gas is formed by tubes that, on a small time scale, either move without changing their shape and size, or radially increase (radially decrease) their size. In this work, we investigated the influence of the gravitational field of a thin closed tube of a massless scalar field, radially changing its size, on its local environment in the gas. In particular, we showed that locally the accelerated expansion is influenced by such parameters as the shape of a thin tube, its thickness, and the relative position of the tubes in the gas.