Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2311.08616

Emergent modified gravity: The perfect fluid and gravitational collapse

Erick I. Duque
View original source ↗Read source document ↗Export metadata ↓

Abstract

Emergent modified gravity is a canonical theory based on general covariance where the spacetime is not fundamental, but rather an emergent object. This feature allows for modifications of the classical theory and can be used to model new effects, such as those suggested by quantum gravity. We discuss how matter fields can be coupled to emergent modified gravity, realize the coupling of the perfect fluid, identify the symmetries of the system, and explicitly obtain the Hamiltonian in spherical symmetry. We formulate the Oppenheimer-Snyder collapse model in canonical terms, permitting us to extend the model to emergent modified gravity and obtain an exact solution to the dust collapsing from spatial infinity including some effects suggested by quantum gravity. In this solution the collapsing dust forms a black hole, then the star radius reaches a minimum with vanishing velocity and finite positive acceleration, and proceeds to emerge out now behaving as a white hole. While the geometry on the minimum-radius surface is regular in the vacuum, it is singular in the presence of dust. However, the fact that the geometry is emergent, and the fundamental fields that compose the phase-space are regular, allows us to continue the canonical solution in a meaningful way, obtaining the global structure for the interior of the star. The star-interior solution is complemented by the vacuum solution describing the star-exterior region by a continuous junction at the star radius. This gluing process can be viewed as the imposition of boundary conditions, which is non-unique and does not follow from the equations of motion. This ambiguity gives rise to different possible physical outcomes of the collapse. We discuss two such phenomena: the formation of a wormhole and the transition from a black hole to a white hole.

Explore related subjects

gr-qc

Keep this discovery

BibTeXRIS

Erick I. Duque. 2023-11-15. Emergent modified gravity: The perfect fluid and gravitational collapse. https://doi.org/10.1103/physrevd.109.044014

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Electrovacuum Black Hole Uniqueness

We prove the black hole uniqueness conjecture in the axially symmetric, stationary, electrovacuum setting, subject to the refined asymptotic analysis of the associated singular harmonic maps, which includes an analyticity hypothesis at the axes. More precisely, it is shown that any asymptotically flat solution of the Einstein--Maxwell equations in this class, with more than one black hole horizon component is either: Majumdar--Papapetrou, up to a duality rotation, in which case all logarithmic angle defects vanish, or every finite axis rod logarithmic angle defect is strictly negative and hence every interaction force is strictly attractive. The proof extends the singular harmonic map method used for vacuum Kerr uniqueness in [18].

gr-qc↗
arXiv2026

Constraining Modified Mass-to-Horizon Cosmology Through Primordial Inflationary Observables

We investigate slow-roll inflation in a modified cosmological framework inspired by a generalized mass-to-horizon relation (MHR), $M=\gamma {c^2 L^n}/{G}$, where $n$ is a real parameter and $\gamma$ a dimensional constant. Using Padmanabhan's emergence paradigm, we derive the modified Friedmann equations for a flat FRW universe and analyze the dynamics of a canonical scalar field (inflaton) under the slow-roll approximation. We study the resulting inflationary phenomenology for power-law and Starobinsky potentials. For power-law potentials, the MHR modification fails to reconcile these models with current CMB constraints on $r$ and $n_s$. In contrast, Starobinsky inflation exhibits significant sensitivity to deviations from $n=1$. A perturbative analysis ($n=1+\Delta$) yields corrections to inflationary observables. We observe that the scalar power-spectrum normalization, under a fixed-Starobinsky prescription, imposes the stringent constraint $0.960 \lesssim n \lesssim 1.040$ for $N=60$ efolds. This is considerably tighter than spectral-index bounds. Our results establish inflation, particularly Starobinsky-like models, as a sensitive probe of generalized horizon thermodynamics and departures from standard MHR scaling.

gr-qc↗
arXiv2026

Improving the Sensitivity of Gravitational Wave Detection with Weighted Conformal Prediction

In the last decade, kilometre-scale interferometric gravitational-wave detectors have observed hundreds of compact binary mergers, the majority of which are binary black holes. However, the data are noise-dominated, and multiple independent search algorithms (pipelines) are used to enhance sensitivity and improve robustness. Rather than the standard approach of selecting the most significant pipeline output, we combine the outputs from all pipelines using a conformal prediction-based framework to provide statistically rigorous confidence estimates for candidate events. While combining pipelines improves sensitivity and ranking robustness, it requires a principled statistical framework that remains valid as data properties evolve across observing runs. A key challenge is distribution shifts between simulated datasets used for training and calibration and the real, unlabelled, observations used for testing, which can invalidate coverage guarantees and bias confidence estimates. In this work, we address this challenge by incorporating likelihood-ratio reweighting into our conformal prediction framework to account for covariate shift. Using mock datasets containing simulated signals, we demonstrate that weighted conformal prediction restores well-calibrated coverage under covariate shift and increases the confidence of events near the detection threshold, recovering true signals that would otherwise be missed.

gr-qc↗