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Composite objects in quantum (super)gravity

Axel Maas, Simon Plätzer, Felix Pressler

TL;DR

The paper investigates geons, self-bound gravitons, as dark matter candidates or primordial black hole analogs using non-perturbative CDT quantum gravity. It shows via CDT simulations that global geometry follows a de Sitter-like profile and that geon-like massive excitations occur with a cosmological-time dependent mass around $0.1-0.2 M_{Planck}$. It extends the framework to supergravity, arguing that diffeomorphism invariance and Elitzur-type arguments render SUSY unobservable directly, but a Fröhlich-Morchio-Strocchi and Brout-Englert-Higgs mechanism could reveal SUSY-like structure in invariant observables. Together, these results suggest a route to particle-like excitations in quantum gravity without contradicting the non-observability of SUSY, with implications for early-universe dynamics and the interpretation of SUSY in high-energy experiments.

Abstract

It has been a long entertained idea that self-bound gravitons, so-called geons, could be a dark matter candidate or form (primordial) black holes. The development of viable candidates for quantum gravity allows now to investigate these ideas. Analytic methods show that the description of geons needs to be based on composite operators made out of the graviton field. We present results from a numerical investigation into this idea using causal dynamical triangulations, an ab-initio non-perturbative definition of quantum gravity based on general relativity, and accessible in lattice-gauge-theory-like simulations. Our results suggest an interesting dependence on cosmological time and other unexpected features. Finally, we extend the analytic part of the setting to a supergravity scenario. This provides hints which, if confirmed, could explain why supersymmetry may in a realistic universe in principle not be observable at low (collider) energy scales.

Composite objects in quantum (super)gravity

TL;DR

The paper investigates geons, self-bound gravitons, as dark matter candidates or primordial black hole analogs using non-perturbative CDT quantum gravity. It shows via CDT simulations that global geometry follows a de Sitter-like profile and that geon-like massive excitations occur with a cosmological-time dependent mass around . It extends the framework to supergravity, arguing that diffeomorphism invariance and Elitzur-type arguments render SUSY unobservable directly, but a Fröhlich-Morchio-Strocchi and Brout-Englert-Higgs mechanism could reveal SUSY-like structure in invariant observables. Together, these results suggest a route to particle-like excitations in quantum gravity without contradicting the non-observability of SUSY, with implications for early-universe dynamics and the interpretation of SUSY in high-energy experiments.

Abstract

It has been a long entertained idea that self-bound gravitons, so-called geons, could be a dark matter candidate or form (primordial) black holes. The development of viable candidates for quantum gravity allows now to investigate these ideas. Analytic methods show that the description of geons needs to be based on composite operators made out of the graviton field. We present results from a numerical investigation into this idea using causal dynamical triangulations, an ab-initio non-perturbative definition of quantum gravity based on general relativity, and accessible in lattice-gauge-theory-like simulations. Our results suggest an interesting dependence on cosmological time and other unexpected features. Finally, we extend the analytic part of the setting to a supergravity scenario. This provides hints which, if confirmed, could explain why supersymmetry may in a realistic universe in principle not be observable at low (collider) energy scales.
Paper Structure (5 sections, 1 equation, 2 figures)

This paper contains 5 sections, 1 equation, 2 figures.

Table of Contents

  1. Introduction
  2. Global properties
  3. Geon
  4. Supergravity
  5. Conclusions and open questions

Figures (2)

  • Figure 1: Left: The average global properties Maas:2025rug as a function of cosmological time $\tau$: The size in terms of simplices and the value and fluctuation of the quantum Ricci curvature scalar. Right: The size measured in simplices, but per configuration MPP:unpublished. Note that the simulations were done using three-dimensional spherical boundary conditions and periodic temporal boundary conditions. Left panel is from a simulation with 320k simplices and 80 time-slices, right panel from 80k simplices and 60 time slices. Always a smearing value of $\delta=6$Maas:2025rug is used for $Q$.
  • Figure 2: The normalized, connected correlator of the Quantum Ricci curvature scalar (top left), together with a fit of type $a+b\exp(-ms)+cs^d$. Top right panel the same for the extracted curvature scalar, but where the fit is mass $m$ and exponent $d$ fixed to be the same as for $Q$. Lower right panel is the extracted mass for different volumes and time extensions as a function of cosmological time normalized to the peak cosmological time. From Maas:2025rugMPP:unpublished.