# Comprehensive numerical relativity -- effective-one-body comparison to inform improvements in waveform models for binary neutron star systems

## TL;DR

This paper compares various tidal effective-one-body models with high-precision numerical relativity simulations for binary neutron star systems, identifying strengths and limitations to improve gravitational waveform modeling.

## Contribution

It provides the most extensive comparison to date, evaluating multiple EOB models against numerical relativity across a broad parameter space.

## Key findings

- Dynamical tides EOB model best matches simulations
- All models underestimate tidal effects for stiff equations or small masses
- Discrepancies increase near merger, highlighting model limitations

## Abstract

We present a detailed comparison between tidal effective-one-body (EOB) models and new state-of-the-art numerical relativity simulations for non-spinning binary neutron star systems. This comparison is the most extensive one to date, covering a wide range in the parameter space and encompassing the energetics of the binary, the periastron advance, the time and frequency evolution of the gravitational wave phase for the dominant mode, and several subdominant modes. We consider different EOB models with tidal effects that have been proposed, including the model with dynamical tides of [Phys.Rev.Lett. 116 (2016) no.18, 181101] and the gravitational self-force (GSF) inspired tidal EOB model of [Phys.Rev.Lett. 114 (2015) no.16, 161103]. The EOB model with dynamical tides leads to the best representation of the systems considered here, however, the differences to the GSF-inspired model are small. A common feature is that for systems where matter effects are large, i.e. stiff equations of state or small total masses, all EOB models underestimate the tidal effects and differences to the results from numerical relativity simulations become noticeable near the merger. We analyze this regime to diagnose the shortcomings of the models in the late inspiral, where the two neutron stars are no longer isolated bodies moving in vacuum. Our work will serve to guide further advances in modeling these systems.