Stars In Other Universes: Stellar structure with different fundamental constants

TL;DR

This paper develops a semi-analytical model to explore how variations in fundamental constants could still permit star formation in hypothetical universes, revealing that such conditions are relatively common.

Contribution

It introduces a new semi-analytical stellar structure model to analyze the impact of varying fundamental constants on star existence in alternate universes.

Findings

Approximately 25% of parameter space supports nuclear fusion stars.

A significant portion of fundamental constant variations still allows star formation.

Unconventional stars like black holes or dark matter stars are also considered in the parameter space.

Abstract

Motivated by the possible existence of other universes, with possible variations in the laws of physics, this paper explores the parameter space of fundamental constants that allows for the existence of stars. To make this problem tractable, we develop a semi-analytical stellar structure model that allows for physical understanding of these stars with unconventional parameters, as well as a means to survey the relevant parameter space. In this work, the most important quantities that determine stellar properties -- and are allowed to vary -- are the gravitational constant $G$, the fine structure constant $\alpha$, and a composite parameter $C$ that determines nuclear reaction rates. Working within this model, we delineate the portion of parameter space that allows for the existence of stars. Our main finding is that a sizable fraction of the parameter space (roughly one fourth) provides the values necessary for stellar objects to operate through sustained nuclear fusion. As a result, the set of parameters necessary to support stars are not particularly rare. In addition, we briefly consider the possibility that unconventional stars (e.g., black holes, dark matter stars) play the role filled by stars in our universe and constrain the allowed parameter space.