New class of compact stars: Pion stars

TL;DR

This paper explores the theoretical possibility of pion stars, compact objects composed mainly of a pion Bose-Einstein condensate, using lattice QCD data and gravitational modeling.

Contribution

It introduces a new class of compact stars based on pion condensates, derived from first-principles lattice QCD calculations without nuclear force modeling.

Findings

Pion stars could be stable gravitationally bound objects.

The equation of state is obtained directly from lattice QCD simulations.

Potential formation mechanisms for pion stars are discussed.

Abstract

We investigate the viability of a new type of compact star whose main constituent is a Bose-Einstein condensate of charged pions. Several different setups are considered, where a gas of charged leptons and neutrinos is also present. The pionic equation of state is obtained from lattice QCD simulations in the presence of an isospin chemical potential, and requires no modeling of the nuclear force. The gravitationally bound configurations of these systems are found by solving the Tolman-Oppenheimer-Volkov equations. We discuss weak decays within the pion condensed phase and elaborate on the generation mechanism of such objects.