Ultracompact stars with multiple necks

TL;DR

This paper explores ultracompact stellar objects with multiple necks in their optical geometry, demonstrating that certain equations of state can produce arbitrarily many necks, supported by a regularized formulation of the field equations.

Contribution

It introduces a framework for constructing ultracompact stars with multiple necks using a regularized field equation approach and highlights the role of specific equations of state.

Findings

Existence of ultracompact stars with arbitrarily many necks

Use of the p=ρ−ρ_s equation of state in modeling

Application of Nilsson and Uggla's regularized formulation

Abstract

We discuss ultracompact stellar objects which have multiple necks in their optical geometry. There are in fact physically reasonable equations of state for which the number of necks can be arbitrarily large. The proofs of these statements rely on a recent regularized formulation of the field equations for static spherically symmetric models due to Nilsson and Uggla. We discuss in particular the equation of state p=\rho-\rho_s which plays a central role in this context.