# Degeneracy in Studying the Supranuclear Equation of State and Modified Gravity with Neutron Stars

## TL;DR

This paper reviews recent theoretical efforts to understand the degeneracy between the neutron star equation of state and alternative gravity theories, highlighting uncertainties in extrapolating physics to strong gravitational fields.

## Contribution

It provides an overview of the challenges and recent progress in disentangling the effects of the EOS and modified gravity in neutron star studies.

## Key findings

- Highlighting the degeneracy complicates EOS determination from astrophysical data.
- Recent theoretical models explore how alternative gravity theories affect neutron star properties.
- Understanding this degeneracy is crucial for interpreting future observational data.

## Abstract

It is generally acknowledged that an extrapolation in physics from a well-known scale to an unknown scale is perilous. This prevents us from using laboratory experience to gain precise information for the supranuclear matter inside neutron stars (NSs). With operating and upcoming astronomical facilities, NSs' equation of state (EOS) is expected to be determined at a new level in the near future, under the assumption that general relativity (GR) is the correct theory for gravitation. While GR is a reasonable working assumption yet still an extrapolation, there could be a large uncertainty due to the not-so-well-tested strong gravitational field inside NSs. Here we review some recent theoretical efforts towards a better understanding of the degeneracy between the supranuclear EOS and alternative gravity theories.