Publications

Order by: publication date number of citations

• Mixmasters in Wonderland: Chaotic dynamics from Carroll limits of gravity

  Gerben Oling, Juan F. Pedraza

  SciPost Phys. Core 8, 025 (2025) · published 27 February 2025 | Toggle abstract · pdf

  We demonstrate that the Carroll limit of general relativity coupled to matter captures the chaotic mixmaster dynamics of near-singularity limits. Zooming in on the behavior of general relativity close to spacelike singularities reveals rich and solvable ultra-local Belinski-Khalatnikov-Lifshitz (BKL) dynamics, which we show to be captured by a Carroll limit. Specifically, building on recent work on geometric Carroll expansions of general relativity, we establish that leading-order Carroll gravity, with suitable matter coupling, accurately describes well-known cosmological billiards behavior. Since the Carroll limit implements the ultra-local limit off shell, this opens up the door to a wide range of possible tractable applications, including spatially inhomogeneous setups and the emergence of spikes at late times. This further suggests that Carroll gravity, along with its subleading corrections, could serve as a valuable tool for studying deep infrared physics in AdS/CFT.

  5 citations

• Possible causes of false general relativity violations in gravitational wave observations

  Anuradha Gupta, K. G. Arun, Enrico Barausse, Laura Bernard, Emanuele Berti, Sajad A. Bhat, Alessandra Buonanno, Vitor Cardoso, Shun Yin Cheung, Teagan A. Clarke, Sayantani Datta, Arnab Dhani, Jose María Ezquiaga, Ish Gupta, Nir Guttman, Tanja Hinderer, Qian Hu, Justin Janquart, Nathan K. Johnson-McDaniel, Rahul Kashyap, N. V. Krishnendu, Paul D. Lasky, Andrew Lundgren, Elisa Maggio, Parthapratim Mahapatra, Andrea Maselli, Purnima Narayan, Alex B. Nielsen, Laura K. Nuttall, Paolo Pani, Lachlan Passenger, Ethan Payne, Lorenzo Pompili, Luca Reali, Pankaj Saini, Anuradha Samajdar, Shubhanshu Tiwari, Hui Tong, Chris Van Den Broeck, Kent Yagi, Huan Yang, Nicolás Yunes, B. S. Sathyaprakash

  SciPost Phys. Comm. Rep. 5 (2025) · published 13 February 2025 | Toggle abstract · pdf

  General relativity (GR) has proven to be a highly successful theory of gravity since its inception. The theory has thrivingly passed numerous experimental tests, predominantly in weak gravity, low relative speeds, and linear regimes, but also in the strong-field and very low-speed regimes with binary pulsars. Observable gravitational waves (GWs) originate from regions of spacetime where gravity is extremely strong, making them a unique tool for testing GR, in previously inaccessible regions of large curvature, relativistic speeds, and strong gravity. Since their first detection, GWs have been extensively used to test GR, but no deviations have been found so far. Given GR's tremendous success in explaining current astronomical observations and laboratory experiments, accepting any deviation from it requires a very high level of statistical confidence and consistency of the deviation across GW sources. In this paper, we compile a comprehensive list of potential causes that can lead to a false identification of a GR violation in standard tests of GR on data from current and future ground-based GW detectors. These causes include detector noise, signal overlaps, gaps in the data, detector calibration, source model inaccuracy, missing physics in the source and in the underlying environment model, source misidentification, and mismodeling of the astrophysical population. We also provide a rough estimate of when each of these causes will become important for tests of GR for different detector sensitivities. We argue that each of these causes should be thoroughly investigated, quantified, and ruled out before claiming a GR violation in GW observations.

  27 citations

• Gravitational higher-form symmetries and the origin of hidden symmetries in Kaluza-Klein compactifications

  Carmen Gómez-Fayrén, Tomás Ortín, Matteo Zatti

  SciPost Phys. Core 8, 010 (2025) · published 29 January 2025 | Toggle abstract · pdf

  We show that, in presence of isometries and non-trivial topology, the Einstein–Hilbert action is invariant under certain transformations of the metric which are not diffeomorphisms. These transformations are similar to the higher-form symmetries of field theories with $p$-form fields. In the context of toroidal Kaluza–Klein compactifications, we show that these symmetries give rise to some of the "hidden symmetries" (dualities) of the dimensionally-reduced theories.

  4 citations

• Celestial $w_{1+\infty}$ charges and the subleading structure of asymptotically-flat spacetimes

  Marc Geiller

  SciPost Phys. 18, 023 (2025) · published 20 January 2025 | Toggle abstract · pdf

  We study the subleading structure of asymptotically-flat spacetimes and its relationship to the $w_{1+∞}$ loop algebra of higher spin charges. We do so using both the Bondi–Sachs and the Newman–Penrose formalism, via a dictionary built from a preferred choice of tetrad. This enables us to access properties of the so-called higher Bondi aspects, such as their evolution equations, their transformation laws under asymptotic symmetries, and their relationship to the Newman–Penrose and the higher spin charges. By studying the recursive Einstein evolution equations defining these higher spin charges, we derive the general form of their transformation behavior under BMSW symmetries. This leads to an immediate proof that the spin 0,1 and spin $s$ brackets reproduce upon linearization the structure expected from the $w_{1+∞}$ algebra. We then define renormalized higher spin charges which are conserved in the radiative vacuum at quadratic order, and show that they satisfy for all spins the $w_{1+∞}$ algebra at linear order in the radiative data.

  9 citations

• EMRI_MC: A GPU-based code for Bayesian inference of EMRI waveforms

  Ippocratis D. Saltas, Roberto Oliveri

  SciPost Phys. Codebases 44 (2025) · published 16 January 2025 | Toggle abstract · pdf

  We describe a simple and efficient Python code to perform Bayesian forecasting for gravitational waves (GW) produced by Extreme-Mass-Ratio-Inspiral systems (EMRIs). The code runs on GPUs for an efficient parallelised computation of thousands of waveforms and sampling of the posterior through a Markov-Chain-Monte-Carlo (MCMC) algorithm. EMRI_MC generates EMRI waveforms based on the so-called kludge scheme, and propagates it to the observer accounting for cosmological effects in the observed waveform due to modified gravity/dark energy. The code provides a helpful resource for forecasts for interferometry missions in the milli-Hz scale, e.g the satellite-mission LISA.

  3 citations

• Codebase release 1.0 for EMRI_MC

  Ippocratis D. Saltas, Roberto Oliveri

  SciPost Phys. Codebases 44-r1.0 (2025) · published 16 January 2025 | Toggle abstract · src

  We describe a simple and efficient Python code to perform Bayesian forecasting for gravitational waves (GW) produced by Extreme-Mass-Ratio-Inspiral systems (EMRIs). The code runs on GPUs for an efficient parallelised computation of thousands of waveforms and sampling of the posterior through a Markov-Chain-Monte-Carlo (MCMC) algorithm. EMRI_MC generates EMRI waveforms based on the so-called kludge scheme, and propagates it to the observer accounting for cosmological effects in the observed waveform due to modified gravity/dark energy. The code provides a helpful resource for forecasts for interferometry missions in the milli-Hz scale, e.g the satellite-mission LISA.

  1 citation

• QCD axion strings or seeds?

  Simone Blasi, Alberto Mariotti

  SciPost Phys. 18, 016 (2025) · published 15 January 2025 | Toggle abstract · pdf

  We study the impact of QCD axion strings on the cosmological history of electroweak (EW) symmetry breaking, focussing on the minimal KSVZ axion model. We consider the case of the pure SM Higgs potential as well as a simple scenario with a first order EW phase transition. We capture the effect of the Peccei-Quinn (PQ) sector within an effective-theory approach for the Higgs field, where the axion string core and the heavy PQ states are integrated out. The relevant parameters in this effective theory are controlled by the size of the portal coupling between the Higgs and the PQ scalar, and the mass of the PQ radial excitation. We determine the range of portal couplings for which the axion strings can strongly affect the dynamics of EW symmetry breaking. In the case of a first order EW phase transition, the strings can act as seeds by either catalyzing the nucleation of (non-spherical) bubbles, or leading to the completion of the phase transition by triggering a classical instability.

  3 citations

• Cosmological cutting rules for Bogoliubov initial states

  Diptimoy Ghosh, Enrico Pajer, Farman Ullah

  SciPost Phys. 18, 005 (2025) · published 7 January 2025 | Toggle abstract · pdf

  The field theoretic wavefunction in cosmological spacetimes has received much attention as a fundamental object underlying the generation of primordial perturbations in our universe. Assuming an initial Bunch-Davies state, unitary time evolution implies an infinite set of cutting rules for the wavefunction to all orders in perturbation theory, collectively known as the cosmological optical theorem. In this work, we generalise these results to the case of Bogoliubov initial states, accounting for both parity-even and parity-odd interactions. We confirm our findings in a few explicit examples, assuming IR-finite interactions. In these examples, we preserve scale invariance by adiabatically turning on interactions in the infinite past rather than imposing a Bogoliubov state at some finite initial time. Finally, we give a prescription for computing Bogoliubov wavefunction coefficients from the corresponding Bunch-Davies coefficients for both $n$-point contact and four-point exchange diagrams.

  6 citations

• Codebase release 1.0 for NumDynInflation

  Siddharth S. Bhatt, Swagat S. Mishra, Soumen Basak, Surya N. Sahoo

  SciPost Phys. Codebases 42-r1.0 (2024) · published 12 December 2024 | Toggle abstract · src

  Numerical simulations of the inflationary dynamics are presented here for a single canonical scalar field minimally coupled to gravity. We spell out the basic equations governing the inflationary dynamics in terms of cosmic time $t$ and define a set of dimensionless variables convenient for numerical analysis. We then provide a link to our simple numerical Python code on GitHub that can be used to simulate the background dynamics as well as the evolution of linear perturbations during inflation. The code computes both scalar and tensor power spectra for a given inflaton potential $V(\phi)$. We discuss a concrete algorithm to use the code for various purposes, especially for computing the enhanced scalar power spectrum in the context of Primordial Black Holes and scalar-induced Gravitational Waves. We also compare the efficiency of different variables used in the literature to compute the scalar fluctuations. We intend to extend the framework to simulate the dynamics of a number of different quantities, including the computation of scalar-induced second-order tensor power spectrum in the near future.

  1 citation

• Numerical simulations of inflationary dynamics: Slow roll and beyond

  Siddharth S. Bhatt, Swagat S. Mishra, Soumen Basak, Surya N. Sahoo

  SciPost Phys. Codebases 42 (2024) · published 12 December 2024 | Toggle abstract · pdf

  Numerical simulations of the inflationary dynamics are presented here for a single canonical scalar field minimally coupled to gravity. We spell out the basic equations governing the inflationary dynamics in terms of cosmic time $t$ and define a set of dimensionless variables convenient for numerical analysis. We then provide a link to our simple numerical Python code on GitHub that can be used to simulate the background dynamics as well as the evolution of linear perturbations during inflation. The code computes both scalar and tensor power spectra for a given inflaton potential $V(\phi)$. We discuss a concrete algorithm to use the code for various purposes, especially for computing the enhanced scalar power spectrum in the context of Primordial Black Holes and scalar-induced Gravitational Waves. We also compare the efficiency of different variables used in the literature to compute the scalar fluctuations. We intend to extend the framework to simulate the dynamics of a number of different quantities, including the computation of scalar-induced second-order tensor power spectrum in the near future.

  1 citation