Brane-like singularities with no brane

TL;DR

This paper investigates a new class of future cosmological singularities where the Hubble parameter remains finite but higher derivatives diverge, occurring in standard cosmological models with scalar or tachyon fields, and introduces a generalized $w$-singularity.

Contribution

It uncovers brane-like singularities in usual Friedmann universes and introduces a new finite-time singularity with finite scale factor, pressure, and density, expanding the understanding of cosmological singularities.

Findings

Identified singularities with finite Hubble parameter but diverging higher derivatives.

Discovered a new finite-time singularity with finite scale factor, pressure, and density.

Generalized the concept of $w$-singularity.

Abstract

We use a method of linearization to study the emergence of the future cosmological singularity characterized by finite value of the cosmological radius. We uncover such singularities that keep Hubble parameter finite while making all higher derivatives of the scale factor (starting out from the $\ddot a$) diverge as the cosmological singularity is approached. Since such singularities has been obtained before in the brane world model we name them the "brane-like" singularities. These singularities can occur during the expanding phase in usual Friedmann universe filled with both a self-acting, minimally coupled scalar field and a homogeneous tachyon field. We discover a new type of finite-time, future singularity which is different from type I-IV cosmological singularities in that it has the scale factor, pressure and density finite and nonzero. The generalization of $w$-singularity is obtained as well.