Research

1. Nonlinear Dynamics near the Threshold of Gravitational Collapse J. Redondo-Yuste & J. C. Aurrekoetxea preprint  ·  arXiv:2607.27343  ·  INSPIRE

   Perturbation theory is an essential tool to model and interpret gravitational dynamics, for example, binary black hole mergers. Therefore it is also crucial to precisely understand its regimes of validity. The collapse of a scalar field under its own self-gravity provides a clean laboratory to study these questions. By varying the field's initial amplitude we can transition smoothly between a perturbative regime, where the field scatters in an approximately flat spacetime; and a nonperturbative regime, where a black hole forms in finite time. In this work, we use numerical relativity simulations of this set-up to investigate the accuracy of a perturbative expansion around flat spacetime, including next-to-next-to-leading order effects. Our simulations show deviations from these perturbative predictions before black hole formation, once the maximum luminosity of the process is sufficiently large, L_peak ~ 10^-2 L_Planck. We characterize these nonlinear effects including a redshift of the driving frequency and a power-law spectral amplitude, which we show is consistent with approximate discrete self-similarity. These results provide a step forward towards understanding the limits of perturbative expansions in more realistic strong-gravity phenomena such as non-spherical collapse and high-velocity black hole mergers.

2. Black Hole Ringdown Nonlinearities in the Large-D Limit R. Emparan, A. Green-Salinas, D. Pereñiguez & J. Redondo-Yuste preprint  ·  arXiv:2606.23804  ·  INSPIRE

   We initiate the study of nonlinear effects in the ringdown phase of black hole mergers using the effective theory of black hole dynamics in the large-D limit. This framework offers several advantages: the quasinormal mode spectrum, including nonlinear corrections, is analytically tractable; numerical simulations of collisions are computationally inexpensive; and the extraction and analysis of the ringdown signal are clean and controlled. As a proof of concept, we derive analytic expressions for the third-order response of a static black hole driven by a single quasinormal mode, and apply them to study the ringdown following head-on collisions of non-spinning black holes across a range of velocities and mass ratios. We find that including nonlinear effects, up to quadratic and cubic order, improves the accuracy of quasinormal-mode modelling of black hole relaxation by several orders of magnitude. The results also show a clear growth in the strength of nonlinear effects as the collision velocity increases.

3. The third wheel: ringdown and lensing of triple systems V. Cardoso, G. Ficarra, J. Redondo-Yuste & J. S. dos Santos Phys. Rev. D 114 (2026) 024065  ·  arXiv:2605.20320  ·  INSPIRE

   Triple systems have progressively been recognized as ubiquitous in our universe and provide a good testing ground for wave generation and propagation in nontrivial environments. We study the dynamics of triple systems in a fully nonlinear setting. In particular, we analyze numerical relativity simulations of head-on collisions of black holes in the presence of a companion. We show evidence for Doppler and gravitational redshift in the ringdown, and clear signs of amplification by lensing. In certain cases, we also show the appearance of a second image, with hints of resonant mode excitation. Our results pave the way for the understanding of mergers in the vicinity of massive companions. Even in extreme setups we do not find collapse to black holes from lensed gravitational radiation.

4. Axial Oscillations of Viscous Neutron Stars S. Bussières, J. Redondo-Yuste, J. J. Ortega Gómez & V. Cardoso Phys. Rev. D 114 (2026) 044012  ·  arXiv:2604.13208  ·  INSPIRE

   The oscillation modes of stars play an important role in observations, and on the understanding of stellar stability properties. The role of viscosity in the oscillation modes of compact stars has been so far understood very loosely only, in absence of a well posed framework. We use recent breakthroughs in the formulation of a causal and stable theory of relativistic hydrodynamics, to study oscillation modes of neutron stars. We characterize the axial spectrum of compact stars and uncover new, viscosity-driven families of modes, without a perfect fluid counterpart. Our results show mode avoidance in some of these families, and a spectrum of long-lived modes, whose role in astrophysical, dynamical processes is yet to be understood.

5. Radial Oscillations of Viscous Stars L. S. Keeble & J. Redondo-Yuste Phys. Rev. D 113 (2026) 124058  ·  arXiv:2603.23622  ·  INSPIRE

   Oscillation modes of neutron stars, a key target for third-generation gravitational wave detectors, encode key information about their constituent nuclear matter. In this work, we study the effect of viscosity on oscillations of cold, polytropic, spherically symmetric neutron stars. We focus on purely radial oscillations and work perturbatively to linear order within two hydrodynamic frameworks: the acausal covariant generalization of the Navier-Stokes equations proposed by Eckart, and the causal generalization formulated by Bemfica, Disconzi, Noronha, and Kovtun (BDNK). We find that viscosity damps the radial modes on millisecond timescales and induces fractional shifts in the oscillation frequency which increase both with the compactness and viscosity of the star, reaching up to the percent level for the fundamental mode with bulk viscosities ζ~10^30 g/cm/s. For more viscous stars, the oscillation frequency decreases, becoming zero (i.e., an overdamped mode) for ζ≳10^31 g/cm/s. We also study the linear threshold of gravitational collapse. Consistent with recent analytic results in the zero heat conductivity limit, we find that viscosity in Eckart theory cannot stabilize an unstable inviscid star. We provide numerical evidence that viscosity in BDNK theory is similarly unable to prevent gravitational collapse, but it slightly modifies the threshold of collapse. Overall, our results advance our understanding of the impact of viscosity on the oscillation modes of neutron stars, a key component of viscous asteroseismology with next-generation gravitational wave detectors.

6. Nonlinear Dynamics in General Relativity V. Cardoso, J. Redondo-Yuste, U. Sperhake & F. Tuncer preprint  ·  arXiv:2603.04501  ·  INSPIRE

   Black holes and gravitational waves are consequences of the nonlinear character of the Einstein equations. Yet, the remarkable properties of General Relativity point to the existence of other effects. Here we uncover new nonlinear facets of gravity. We establish higher harmonic generation, spectral broadening and focusing in the Einstein Klein-Gordon system. In vacuum, we show that scattering of monochromatic waves at quadratic order is weakly sensitive to frequency, at large wavelengths. These aspects can both explain the seemingly smooth behavior of mergers, but also caution us against too simplistic an interpretation of waveforms.

7. Perturbations of Plane Waves and Quadratic Quasinormal Modes on the Lightring K. Fransen, D. Pereñiguez & J. Redondo-Yuste JHEP 12 (2025) 148  ·  arXiv:2509.03598  ·  INSPIRE

   We study second order gravitational perturbations on plane wave spacetimes from both the metric and curvature perturbation points of view. For the former, we explicitly use the isometries of the background to introduce tensor oscillator harmonics, which render Einstein’s equations algebraic around symmetric plane waves. For the latter, we formulate the first and second order Teukolsky equations in a Geroch-Held-Penrose covariant way. Both approaches are useful in their own right, and together with our discussion on gauge freedom, they provide a foundation for the study of higher-order gravitational dynamics around plane wave spacetimes. Taking the perspective that these plane wave spacetimes arise from Penrose limits, we subsequently use these results to explore the nonlinear gravitational dynamics close to black hole lightrings. Specifically, we define and discuss quadratic quasinormal mode ratios, observe that they satisfy emergent selection rules, and make publicly available a code to compute them.

8. Superradiant amplification by rotating viscous compact objects J. Redondo-Yuste & V. Cardoso Phys. Rev. D 112 (2025) L061501  ·  arXiv:2506.13850  ·  INSPIRE

   We study fluctuations of rotating viscous stars, using the causal relativistic hydrodynamics of Bemfica, Disconzi, Kovtun, and Noronha. We derive, in a slow-rotation approximation, a coupled system of equations describing the propagation of axial gravitational waves through the star, which couple to internal viscous modes. We show that rotating viscous stars amplify incoming low-frequency gravitational waves, a phenomenon which we argue to be universal. Superradiant amplification does not seem to trigger an instability for uniformly rotating stars, even if the object is compact enough to have light rings.

9. Black hole spectroscopy: from theory to experiment E. Berti et al. (incl. J. Redondo-Yuste) Class. Quant. Grav. 43 (2026) 123001  ·  arXiv:2505.23895  ·  INSPIRE

   The ‘ringdown’ radiation emitted by oscillating black holes has great scientific potential. By carefully predicting the frequencies and amplitudes of black hole quasinormal modes and comparing them with gravitational-wave (GW) data from compact binary mergers we can advance our understanding of the two-body problem in general relativity, verify the predictions of the theory in the regime of strong and dynamical gravitational fields, and search for physics beyond the Standard Model or new gravitational degrees of freedom. We summarize the state of the art in our understanding of black hole quasinormal modes in general relativity and modified gravity, their excitation, and the modeling of ringdown waveforms. We also review the status of LIGO-Virgo-KAGRA ringdown observations, data analysis techniques, and the bright prospects of the field in the era of LISA and next-generation ground-based GW detectors.

10. Perturbative and non-linear analyses of gravitational turbulence in spacetimes with stable light rings J. Redondo-Yuste & A. Cárdenas-Avendaño Phys. Rev. D 111 (2025) 124009  ·  arXiv:2502.18643  ·  INSPIRE

    Some black hole mimickers, as well as black strings and other higher-dimensional spacetimes, exhibit stable light rings-regions where light or high-frequency gravitational waves can be trapped. In these regions, linear perturbations decay slowly, raising the possibility of nonlinear instability mechanisms. In this work, we study the cubic nonlinear wave equation as a proxy for Einstein’s equations, using a four-dimensional model geometry that allows stable trapping. By employing a perturbative approach, and neglecting the backreaction onto the spacetime, we show that the nonlinear wave equation on the sphere with dissipative terms captures several features of the full nonlinear problem. This framework allows us to confirm a previous conjecture: all higher-order energy norms grow for arbitrarily small initial fluctuation amplitudes. Additionally, we analyze the system’s mode spectrum at late times, revealing an inertial range dominated by a direct energy cascade. These findings further support the notion that spacetimes with stable light rings develop weak, high-frequency radiation hair, which will not generically lead to instabilities.

11. Lensing and wave optics in the strong field of a black hole J. C. L. Chan, C. Dyson, M. Garcia, J. Redondo-Yuste & L. Vujeva Phys. Rev. D 112 (2025) 064009  ·  arXiv:2502.14073  ·  INSPIRE

    Gravitational waves (GWs) are lensed by matter, offering a unique probe of both the large-scale structure of the Universe and the fundamental properties of GW propagation. GWs can also be affected by wave optics effects when their wavelength is comparable to the size of the lens. While this regime has been well studied in the Newtonian approximation, the role of strong gravitational fields remains largely unexplored. This is particularly relevant for lensing by intermediate and supermassive black holes (BHs), which can occur near active galactic nuclei or in compact triple systems. In this work, we analyze the lensing of GWs by a non-rotating BH and compare our results to the Newtonian point-mass approximation. We construct frequency-dependent amplification factors that incorporate strong-field effects, revealing explicit polarization mixing and absorption by the event horizon. Using a fiducial GW event, we explore key phenomenological signatures of BH lensing, highlighting new observational opportunities to probe strong gravitational fields through GW lensing.

12. Ringdown nonlinearities in the eikonal regime B. Bucciotti, V. Cardoso, A. Kuntz, D. Pereñiguez & J. Redondo-Yuste Phys. Rev. D 111 (2025) L081502  ·  arXiv:2501.17950  ·  INSPIRE

    The eikonal limit of black hole quasinormal modes (the large multipole limit ℓ ≫ 1) can be realized geometrically as a next-to-leading order solution to the geometric optics approximation, and also as linear fluctuations about the Penrose limit plane wave adapted to the lightring. Extending this interpretation beyond the linear order in perturbation theory requires a robust understanding of quadratic quasinormal modes for large values of ℓ. We analyze numerically the relative excitation of quadratic to linear quasinormal modes of Schwarzschild black holes, with two independent methods. Our results suggest that the ratio of quadratic to linear amplitudes for the ℓ × ℓ → 2ℓ channel converges towards a finite value for large ℓ, in sharp contrast with a recent proposal inspired by the Penrose limit perspective. On the other hand, the 2 × ℓ → ℓ + 2 channel seems to have a linearly growing ratio. Nevertheless, we show that there is no breakdown of black hole perturbation theory for physically realistic initial data.

13. Perturbations of relativistic dissipative stars J. Redondo-Yuste Class. Quant. Grav. 42 (2025) 075012  ·  arXiv:2411.16841  ·  INSPIRE

    Viscous fluids can dissipate and alter the propagation of gravitational waves (GWs), as well as modify the relaxation and stability properties of self-gravitating fluids. This is particularly relevant in order to understand the relaxation to equilibrium of neutron stars, and their GW emission. Here we study the linearized theory of perturbations of spherically symmetric self-gravitating fluids, treating only the radiative modes. Dissipative effects are included through the hydrodynamics theory of Bemfica, Disconzi, Noronha and Kovtun (BDNK). This theory has been shown to be causal and stable, despite involving only first order gradients. We show how the problem reduces to two coupled wave equations in the axial sector, one of them associated to a novel viscous mode, and including explicitly dissipative terms. In the polar sector we reduce the problem to five coupled wave equations and one additional constraint. We comment on their causal structure, and recover the causality bounds of the BDNK theory.

14. The dynamical response of viscous objects to gravitational waves V. Boyanov, V. Cardoso, K. D. Kokkotas & J. Redondo-Yuste Phys. Rev. Lett. 135 (2025) 151402  ·  arXiv:2411.16861  ·  INSPIRE

    We study the dynamical response of viscous materials to gravitational waves, in the context of a fully relativistic theory of fluid dynamics. For the first time, we calculate oscillation modes and scattering properties of viscous stars. Viscous stars absorb high-frequency radiation, following a dispersion relation introduced by Press. In the extremely large viscosity regime, stars would become reflectors of waves, but this regime appears to be forbidden by causality bounds. In the context of black hole mimickers, we show how maximally viscous stars on the threshold of stability mimic the absorption of a black hole with the same mass. Our results suggest that rotating viscous stars will amplify incoming radiation.

15. Hushing black holes: tails in dynamical spacetimes V. Cardoso et al. (incl. J. Redondo-Yuste) Phys. Rev. D 109 (2024) L121502  ·  arXiv:2405.12290  ·  INSPIRE

    Stationary, asymptotically flat, black hole solutions of the vacuum field equations of general relativity belong to the Kerr family. But how does one approach this state, dynamically? Linearized fluctuations decay at late times, at fixed spatial position, as a Price power law for generic initial conditions. However, little attention was paid to forced and nonlinear spacetimes, where matter and nonlinearities play a role. We uncover a new, source-driven tail governing waves generated by pointlike matter and nonlinearities, which can dominate over Price’s decay.

16. Relativistic aerodynamics of spinning black holes C. Dyson, J. Redondo-Yuste, M. van de Meent & V. Cardoso Phys. Rev. D 109 (2024) 104038  ·  arXiv:2402.07981  ·  INSPIRE

    Astrophysical black holes do not exist in a vacuum, and their motion is affected by the galactic environment. As a black hole moves it attracts stars and matter, creating a wake that, in turn, exerts an effective friction slowing down the black hole. This force is known as dynamical friction and has significant consequences, ranging from the formation of supermassive black hole binaries to modifications in the phase of binary mergers. In this work we explore the motion of spinning black holes on a medium. We find that the classical “drag” along the velocity direction is modified and two novel forces appear: a rotational force, which in the context of fluid dynamics is dubbed the Magnus force, and a lift, orthogonal to the direction of motion. We develop a first-principles fully relativistic treatment of these spin-induced aerodynamic forces in two types of environment: (i) collisionless corpuscular matter and (ii) a light scalar field, exploring the differences between both cases. In both cases we find that the total rotational force acts precisely in the opposite direction as compared to the classical setup of a spinning ball moving through a fluid. Finally, we comment on the consequences of these new effects for astrophysics and gravitational wave observations.

17. Ringdown of a dynamical spacetime J. Redondo-Yuste, D. Pereñiguez & V. Cardoso Phys. Rev. D 109 (2024) 044048  ·  arXiv:2312.04633  ·  INSPIRE

    The gravitational waves emitted (some time) after two black holes merge are well described by the theory of linear perturbations on a spacetime characterized by the mass and spin of the remnant. However, in the very early stages right after merger, both the mass and spin are changing. In this work we explore, in a setup based on Vaidya’s spacetime, the dynamical consequences of a change of mass in the spacetime due to the accretion of null matter (for example, gravitational waves). We show that accretion imprints time-dependent frequencies and amplitude to a ringdown waveform, and we show how to model accurately this effect in certain regimes. We also comment on the direct emission of gravitational waves due to perturbations in the infalling matter, which is of relevance for black holes embedded in astrophysical environments.

18. Twisted traces on abelian quantum Higgs and Coulomb branches D. Gaiotto, J. Hilburn, J. Redondo-Yuste, B. Webster & Z. Zhou Commun. Math. Phys. 406 (2025) 202  ·  arXiv:2308.15198  ·  INSPIRE

    We study twisted traces on the quantum Higgs branches A_ Higgs of 3d, N=4 gauge theories, that is, the quantum Hamiltonian reductions of Weyl algebras. In theories which are good or ugly, we define a twisted trace that arises naturally from the correlation functions of the gauge theory. We show that this trace induces an inner product and a short star product on A_ Higgs. We analyze this trace in the case of an abelian gauge group and show that it has a natural expansion in terms of the twisted traces of Verma modules, confirming a conjecture of the first author and Okazaki. This expansion has a natural interpretation in terms of 3-d mirror symmetry, and we predict that it can be interpreted as an Atiyah-Bott fixed-point formula under the quantum Hikita isomorphism.

19. Spin dependence of black hole ringdown nonlinearities J. Redondo-Yuste, G. Carullo, J. L. Ripley, E. Berti & V. Cardoso Phys. Rev. D 109 (2024) L101503  ·  arXiv:2308.14796  ·  INSPIRE

    The nonlinear character of general relativity leaves its imprint in the coalescence of two black holes, from the inspiral to the final ringdown stage. To quantify the impact of nonlinearities, we work at second order in black hole perturbation theory and we study the excitation of second-order modes relative to the first-order modes that drive them as we vary the black hole spin and the initial data for the perturbations. The relative amplitude of second-order modes is only mildly dependent on the initial data that we consider, but it strongly decreases for large black hole spins. This implies that the extrapolation of calculations based on the Kerr–conformal field theory correspondence to subextremal Kerr black holes should be viewed with caution.

20. Eternal binaries J. Redondo-Yuste, V. Cardoso, C. F. B. Macedo & M. van de Meent Phys. Rev. D 107 (2023) 124025  ·  arXiv:2304.02039  ·  INSPIRE

    The two-body problem is extensively studied in open systems and asymptotically flat spacetimes. However, there are many systems where radiation is trapped: they range from radiating charges in cavities to low-energy excitations of massive degrees of freedom, to anti–de Sitter spacetimes. Here, we study the problem of motion of a pointlike scalar charge orbiting a massive compact object inside a cavity. We first show that—assuming circular motion—there are initial conditions for which the scalar self-force vanishes and the binary is eternal. We then consider the evolution of the system under radiation reaction in a toy model which we argue captures the essentials of orbiting particles. We show that eternal circular binaries may exist. We also show that the presence of cavity modes leads to chaos in regimes of strong coupling or when the system is initialized close enough to a resonance. Our results have implications for physics in anti–de Sitter spacetimes and possibly for binaries evolving within dark matter haloes, if it consists of massive fields.

21. Diverging black hole entropy from quantum infrared non-localities A. Platania & J. Redondo-Yuste Phys. Lett. B 857 (2024) 138993  ·  arXiv:2303.17621  ·  INSPIRE

    Local higher-derivative corrections to the Einstein-Hilbert action yield sub-leading corrections to the Bekenstein-Hawking area law. Here we show that if the quantum effective action comprises a certain class of infrared non-localities, the entropy of large black holes generally diverges to either positive or negative infinity. In such theories, large spherically symmetric black holes would be either highly chaotic or thermodynamically impossible, respectively. In turn, this puts strong constraints on the Laurent expansion of the form factors in the effective action.

22. Non-linear black hole dynamics and Carrollian fluids J. Redondo-Yuste & L. Lehner JHEP 02 (2023) 240  ·  arXiv:2212.06175  ·  INSPIRE

    The dynamics of black hole horizons has recently been linked to that of Carrollian fluids. This results in a dictionary between geometrical quantities and those of a fluid with unusual properties due its underlying Carrollian symmetries. In this work we explore this relation in dynamical settings with the interest of shedding light on either side by relevant observations. In particular: we discuss how the null surface where the Carrollian fluid evolves is affected by its behavior; that the fluid’s equilibration properties are tied to teleological considerations; the connection of higher derivative contributions as both source of energy and dissipation for the fluid and the non-linear behavior of black holes. This latter point, connects with discussions of non-linear modes in the relaxation to equilibrium of perturbed black holes.

23. Carrollian Motion in Magnetized Black Hole Horizons F. Gray, D. Kubiznak, T. R. Perche & J. Redondo-Yuste Phys. Rev. D 107 (2023) 064009  ·  arXiv:2211.13695  ·  INSPIRE

    We revisit the motion of massless particles with anyonic spin in the horizon of Kerr-Newman geometry. As recently shown, such particles can move within the horizon of the black hole due to the coupling of charges associated with a two-parametric central extension of the two-dimensional Carroll group to the magnetic field generated by the black hole—the so-called “anyonic spin-Hall effect.” We show that the previously computed magnetic field is not invariant under Carroll diffeomorphisms and find another result which respects these symmetries of the horizon. We also consider a more astrophysically relevant case of a (weakly charged) rotating back hole placed in a uniform magnetic field, which could, for instance, be induced by the surrounding plasma. We show that a qualitatively similar magnetic field assisted anyonic spin-Hall effect takes place, even in the absence of black hole rotation. The theoretical possibility of a motion induced by a magnetic monopole is also studied.

24. Quantum electrodynamics in anisotropic and tilted Dirac photonic lattices J. Redondo-Yuste, M. B. de Paz, P. A. Huidobro & A. González-Tudela New J. Phys. 23 (2021) 103018  ·  arXiv:2106.10743  ·  INSPIRE

    One of the most striking predictions of quantum electrodynamics is that vacuum fluctuations of the electromagnetic field can lead to spontaneous emission of atoms as well as photon-mediated interactions among them. Since these processes strongly depend on the nature of the photonic bath, a current burgeoning field is the study of their modification in the presence of photons with non-trivial energy dispersions, e.g. the ones confined in photonic crystals. A remarkable example is the case of isotropic Dirac-photons, which has been recently shown to lead to non-exponential spontaneous emission as well as dissipation-less long-range emitter interactions. In this work, we show how to further tune these processes by considering anisotropic Dirac cone dispersions, which include tilted, semi-Dirac, and the recently discovered type II and III Dirac points. In particular, we show how by changing the anisotropy of the lattice one can change both the spatial shape of the interactions as well as its coherent/incoherent nature. Finally, we theoretically analyze a possible implementation based on subwavelength atomic arrays where these energy dispersions can be engineered and interfaced with quantum emitters.

25. Interpretations and naturalness in the radiation-reaction problem C. Barceló, L. J. Garay & J. Redondo-Yuste Symmetry 13 (2021) 658  ·  arXiv:2005.08725  ·  INSPIRE

    After more than a century of history, the radiation-reaction problem in classical electrodynamics still surprises and puzzles new generations of researchers. Here, we revise and explain some of the paradoxical issues that one faces when approaching the problem, mostly associated with regimes of uniform proper acceleration. The answers we provide can be found in the literature and are a synthesis of a large body of research. We only present them in a personal way that may help in their understanding. Besides, after the presentation of the standard answers, we motivate and present a twist to those ideas. The physics of emission of radiation by extended charges (charges with internal structure) might proceed in a surprising oscillating fashion. This hypothetical process could open up new research paths and a new take on the equivalence principle.

Also on: INSPIRE · Google Scholar · arXiv.

◆ invited  ·  ◇ contributed

• Quadratic Quasinormal Modesblackboard 2026.07.06Astrophysics Seminar, Yukawa Institute for Theoretical Physics, Japan
• Strong Field Gravitational Wave Lensing 2026.06.28RESCEU Seminar, Tokyo, Japan
• Perturbation Theory is Unreasonably Effective 2026.06.16New Developments in GW Physics, Kyoto, Japan
• Gravitational Waves from Viscous Stars 2025.11.28Theory Seminar, ICC-UB, Barcelona, Spain
• Nonlinearities and High-frequency Gravitational Wavesblackboard 2025.10.23Strong Gravity Seminar, Perimeter Institute, Waterloo, Canada
• Viscous Stars and the Quest for Gravitational Mirrorsblackboard 2025.09.23Gravity Seminar, Johns Hopkins University, Baltimore, MD
• Nonlinear Effects in Perturbation Theory 2025.05.28QNM Workshop, IBS, Daejeon, Korea
• Nonlinear Gravitational Waves 2025.04.22ACR Division Seminar, Albert Einstein Institute, Berlin, Germany
• Turbulence of Gravitational Waves 2025.03.12Distinguished Astrophysics Seminar, Los Alamos National Laboratory, NM

Public code accompanying some of my research work. Feel free to reach out if you have any questions!

• BlackHoleNonlinearities.jlJulia · Mathematica Excitation of nonlinear higher harmonics when gravitational waves scatter off a black hole. arXiv:2603.04501
• StableLRJulia · Mathematica Perturbations and (dimensionally reduced) nonlinear evolutions of nonlinear waves trapped on stable light rings. arXiv:2502.18643
• Pert_BDNK_StarsMathematica Perturbation theory equations for viscous stars. arXiv:2411.16841
• VaidyaPT.jlJulia Numerical evolution of the ringdown of an accreting black hole (Vaidya spacetime). arXiv:2312.04633
• SURFPython Numerical simulations of Carrollian fluids dual to black hole horizons. arXiv:2212.06175
• DivergingBHEntropyMathematica Mathematica notebook detailing calculations in the paper. . arXiv:2303.17621
• Quadratic mode ratios on Plane WavesMathematica Excitation of quadratic quasinormal modes in the plane wave emerging as the Penrose limit of a Kerr black hole. arXiv:2509.03598
• Axial modes of viscous starsMathematica Also the perfect-fluid version. arXiv:2604.13208
• Slowly rotating viscous starsMathematica · Julia Derivation of perturbation theory equations for rotating viscous stars, and routines to integrate them. arXiv:2411.16861

Teaching assistant at the Niels Bohr Institute, Københavns Universitet.

• Analytical Mechanics with Poul Henrik Damgaard 2023
• Numerical Methods for Physics with Julius Bier Kierkegaard 2023
• Computational Ocean Dynamics with Markus Jochum 2023

Students

• José Ortega Gómez & Sofía Bussieres Master, Erasmus+ internship 2025
• Lucía Vélez  ·  Sashvat Iyer Master thesis at KU2025
• Laura Micheletti  ·  Mathilde Menu Bachelor, summer internship 2025