Stellar Objects From Quantum Gravity

TL;DR

The paper addresses how quantum gravity could modify stellar collapse outcomes by constructing horizonless compact objects sourced by noncommutative-geometry-inspired matter with a Gaussian core. It develops three analytical models—a pure quantum-vacuum star and two quantum-core stars—characterized by a local quantum vacuum and an exterior Schwarzschild-like region, all governed by the noncommutative scale $\sqrt{\theta}$. By exploring four regimes with $\Lambda=1/\sqrt{\theta}$ from Planckian to nuclear scales, it maps how mass, radius, and density profiles scale, predicting objects spanning from microscopic to astrophysically relevant masses and outlining observable discriminants in NICER, EHT, and gravitational-wave channels. The work proposes a viable pathway to experimental evidence of non-classical gravity and outlines concrete multi-messenger signatures that could distinguish these horizonless ultra-compact objects from classical black holes or neutron stars.

Abstract

This paper explores the theoretical implications of quantum gravity by analyzing compact stellar objects, presenting three distinct models that serve as alternatives to traditional black holes. These models are characterized by their extreme compactness and incorporation of a quantum core, successfully avoiding the curvature singularities typically associated with classical general relativity. Central to these models is the noncommutative parameter, which plays a crucial role in determining stellar properties and enables the exploration of various astrophysical regimes. While pure Planckian effects pose significant challenges for observational detection, our findings suggest that lower energy scales may reveal exotic stellar objects with Earth and Sun-like masses that lack classical counterparts, potentially providing the first experimental evidence of non-classical gravity. We propose that the metrics derived in this study can be tested against known neutron stars, offering promising avenues for future research aimed at understanding the interplay between quantum effects in gravity and stellar evolution, ultimately enhancing our comprehension of the universe's fundamental properties.

Figures (2)

• Figure 1: Plots of $w(r) = \frac{p_r(r)}{\rho(r)}$ versus $\frac{r}{\sqrt{\theta}}$ for three different mass values $\mu < \mu_0$. The curves are independent of $\sqrt{\theta}$.
• Figure 2: Density profile of the envelope. Plot of the density $\rho(r)$ given by Eq. \ref{['eq:penv']}, in units of $\rho_1$, as a function of $r/R_1$. The parameters are chosen such that $R_1 \simeq 6.32\sqrt{\theta}$, $R_2 \simeq 30\sqrt{\theta}$, and $M \simeq 6\sqrt{\theta}$. This choice ensures $0.20 \leq r/R_2 \leq 1$ and $2M/R_2 \simeq 0.40$.