arXiv subjects

Anthony Mezzacappa

Publications and source records attributed to Anthony Mezzacappa.

At least 19 recordsLinked to original sources

arXiv2026

Classifying the nuclear equation of state in LVK interferometric noise through core-collapse supernova gravitational-wave signatures using convolutional neural networks

This paper presents a convolutional neural network (CNN) approach to classifying the nuclear equation of state (EOS). As illustrative examples, we use five two-dimensional core-collapse supernova (CCSN) simulations that differ only in their EOS. We analyze estimates of the initial slope of the high-frequency feature (HFF) reconstructed in real interferometric data from the O3b LIGO-Virgo-KAGRA (LVK) observing run at Galactic source distances of 1, 5, and 10 kpc. The CNN classifier achieves an overall accuracy of 98.58% at 1 kpc and 52.43% at 5 kpc. At 10 kpc, its ability to distinguish among the EOS classes is effectively lost. The successful EOS classification at 1 kpc suggests that this approach may be scalable to next-generation observatories. The expected order-of-magnitude sensitivity improvements of Cosmic Explorer and the Einstein Telescope could enable comparable classification performance at approximately ten times the current distance. More detailed performance metrics, including the macro-averaged one-vs-rest (OvR) area under the curve (AUC), yield values of 0.97 and 0.98 at 1 kpc. These results indicate strong classification performance both across the complete set of EOS classes and for the individual classes.

gr-qc↗

arXiv2026

From the Early Slope to Curvature: Future Prospects and challenges for Astrophysical Parameter Estimation Using the Core-Collapse Supernova High-Frequency Feature

Gravitational-wave (GW) signals from core-collapse supernovae (CCSNe) contain both stochastic and deterministic components. Among these, the High-Frequency Feature (HFF), associated with PNS oscillations, has emerged as a robust observable for probing dense-matter physics. Previous studies of the HFF have primarily focused on the early-time slope as a diagnostic of PNS contraction and its dependence on the equation of state (EOS). In this work, we extend the analysis beyond the early-time linear regime. In particular, we discuss how higher-order features of the HFF evolution, such as its curvature, may encode additional information about the time-dependent structure of the PNS and the transition between oscillation modes. Using real interferometric noise and reconstruction techniques on detected candidates by the coherent WaveBurst (cWB) algorithm in its cWB-XP implementation, we illustrate how such features can be accessed. By comparing reconstructed signals at different source distances, we assess the relative impact of detector noise.

gr-qc↗

arXiv2026

Universal relations applied to proto-neutron star generated gravitational waves from three-dimensional core collapse supernova simulations

Using asteroseismology techniques, several relations have been developed that relate the quasi-normal, non-radial oscillation mode frequencies of the proto-neutron star (PNS) to the high frequency component of core collapse supernova (CCSN) generated gravitational waves predicted from simulation. These relations are universal in the sense that they are parameterized entirely by PNS properties, e.g., mean density or surface gravity, and are independent of both progenitor properties, e.g., zero age man sequence (ZAMS) mass or metallicity, and the physics included in CCSN simulations, e.g., nuclear equation of state (EOS). In this work, we apply several externally developed universal relations to PNS evolution data--specifically the mass, M, and radius, R,--generated from both two- and three-dimensional CCSN simulations and compare the resulting PNS oscillation frequencies predicted by the universal relations to the peak gravitational wave frequencies computed directly from the simulation-produced spectrogram. Additionally, we use the gravitational wave spectrogram peak frequencies as input to the universal relations and compare the predicted PNS properties from each relation to the true PNS properties as determined by the simulations. In this way, we show what these universal relations would predict for the PNS properties and their evolution from a real CCSN gravitational wave detection in the best case scenario, i.e., no detector noise. Our results indicate that caution must be exercised when using these universal relations, particularly when interpreting their predictions for PNS evolution from a gravitational wave detection, and that, given the extent to which we do see agreement between asteroseismological predictions and simulation outcomes, further development of universal relations would be beneficial.

gr-qc↗

arXiv2026

Linear Gravitational Wave Memory Through the Window of Core-Collapse Supernovae

Low-frequency gravitational waves ($\lessapprox$ 50 Hz) from core-collapse supernovae are becoming more important for current and future gravitational wave studies. This frequency region is dominated by the global morphology of the explosion and the anisotropic emission of neutrinos from the event. This paper serves as a brief review of both theory and detection (prospects) for gravitational waves in the low-frequency region. We discuss the generation of the linear gravitational wave memory sourced from neutrino emission and show results from an example 15 $M_{\odot}$ Solar metallicity progenitor. We also discuss the detection of the linear gravitational wave memory in current detectors, utilizing a combination of a linear predictive filter and matched templating. Finally we will discuss detection prospects in future detectors such as Cosmic Explorer, Einstein Telescope, the Laser Interferometer Space Antenna, and the Lunar Gravitational-wave Antenna.

astro-ph.HE↗

arXiv2026

Core Collapse Supernova Modeling: The Next Ten Years

Core collapse supernova modeling has advanced considerably since the first numerical simulations were performed sixty years ago. In particular, the last decade has brought us sophisticated three-dimensional models with significant predictive capabilities -- e.g., for core collapse supernova gravitational wave emission. The six decades of modeling have shown us the importance of individual components of these general relativistic neutrino radiation magnetohydrodynamics events -- specifically, the importance of neutrino kinetics, fluid instabilities, magnetic fields, strong gravity, and the nuclear equation of state and neutrino--matter interactions calculated in a manner consistent with the equation of state. They have also shown us that simulation outcomes are sensitive to variations in the treatment of these ingredients, demanding a level of rigor that has not yet been consistently met by modelers. The efficacy of the neutrino shock reheating mechanism for core collapse supernovae has been demonstrated. The models now require an improved quantitative predictive capability, which will be achieved through increased sophistication in the treatment of model components, both macroscopic (e.g., strong-field gravity) and microscopic (e.g., neutrino--matter interactions). Advancement of core collapse supernova theory will also require the cooperation of modelers in other fields, especially stellar evolution and nuclear theory, to meet the level of rigor required to make the most of the eventuality of a Galactic core collapse supernova and its multimessenger emissions.

astro-ph.HE↗

arXiv2026

thornado+Flash-X: A Hybrid DG-IMEX and Finite-Volume Framework for Neutrino-Radiation Hydrodynamics in Core-Collapse Supernovae

We present neutrino-transport algorithms implemented in the toolkit for high-order neutrino-radiation hydrodynamics (thornado) and their coupling to self-gravitating hydrodynamics within the adaptive mesh refinement (AMR)-based multiphysics simulation framework Flash-X. thornado, developed primarily for simulations of core-collapse supernovae (CCSNe), employs a spectral, six-species two-moment formulation with algebraic closure and special-relativistic observer corrections accurate to $O(v/c)$, and uses discontinuous Galerkin (DG) methods for phase-space discretization combined with implicit-explicit time stepping. A key development is a nonlinear neutrino-matter coupling algorithm based on nested fixed-point iteration with Anderson acceleration, enabling fully implicit treatment of collisional processes, including energy-coupling interactions such as neutrino-electron scattering and pair production. Coupling to finite-volume (FV) hydrodynamics is achieved with a hybrid DG-FV representation of the fluid variables and operator-split evolution in Flash-X. The implementation is verified using basic transport tests with idealized opacities and relaxation and deleptonization problems with tabulated microphysics. Spherically symmetric CCSN simulations demonstrate accuracy and robustness of the coupled scheme, including close agreement with the CCSN simulation code Chimera. An axisymmetric CCSN simulation further demonstrates the viability of DG-based neutrino transport for multidimensional supernova modeling within Flash-X. thornado's neutrino-transport solver is GPU-enabled using OpenMP offloading or OpenACC, and all CCSN applications included in this work use the GPU implementation. Together, these results establish a foundation for future enhancements in physics fidelity, numerical algorithms, and computational performance, for increasingly realistic large-scale CCSN simulations.

astro-ph.IM↗

arXiv2025

Gravitational Waves as a Probe of Core Collapse Supernova Progenitor Structure

We present the gravitational wave predictions from two-dimensional core collapse supernova (CCSN) simulations initiated from two nearly identical progenitors that have significantly different internal structures due to their late-stage stellar evolution. At the time of collapse, the 15.78 $M_{\odot}$ and 15.79 $M_{\odot}$ progenitors have compactness parameters $\xi_{2.5}$ of 0.136 and 0.206, respectively. We connect several features of the gravitational wave signal from each model to its previously explored explosion dynamics. In particular, the greater accretion onto the PNS of the more compact model is evident in broad-band frequency features with larger amplitude gravitational wave strains and greater gravitational wave energy release when compared to the less compact model. Additionally, the faster contraction rate of the more compact model is reflected in the $\sim$26% greater slope of the $g$-/$f$-mode feature (gfF) evolution of the gravitational wave signal. This work shows that in principle gravitational wave detection may provide information about interior stellar structure.

astro-ph.HE↗

arXiv2025

Low-Frequency Gravitational Waves in Three-Dimensional Core-Collapse Supernova Models

We discuss the low-frequency gravitational wave signals from three state-of-the-art three-dimensional core-collapse supernova models produced with the \textsc{Chimera} supernova code. We provide a detailed derivation of the gravitational wave signal sourced from the anisotropic emission of neutrinos and provide the total (fluid sourced and neutrino sourced) gravitational waves signal generated in our models. We discuss the templatablity of this low-frequency signal, which is useful for future work involving matched filtering for signal detection and parameter estimation. Errata: The neutrino-induced gravitational waveforms presented were computed incorrectly. They were underestimated by a factor of $4\pi$. While the results are impacted, the original conclusions are not. In fact, they are only reinforced. The corrected versions of Figs. 5--7, 11--16, and 19 are given here. The captions of Figs. 5--7, 11, 12, 16, and 19 are not modified. The captions of Figs. 13, 14, and 15 are corrected to the fit parameters for the corrected waveforms. The corrected versions of Tables I--III are given here. There is no correction to the caption. Finally the authors would like to acknowledge Lella et al. [90] for pointing out the discrepancy between our computed neutrino-induced waveforms and theirs, which prompted us to investigate the discrepancy and which led to the discovery of our error.

astro-ph.HE↗

arXiv2025

Core Collapse Supernova Gravitational Wave Sourcing and Characterization based on Three-Dimensional Models

We present for the first time an analysis of high-frequency gravitational wave (GW) emission from proto-neutron stars (PNS) in core collapse supernovae (CCSN) that combines spatial decomposition and modal decomposition to both source and characterize the emission using three-dimensional CCSN simulations. We analyze simulations initiated from 15 and 25 solar mass progenitors with Solar- and zero-metallicity respectively. We decompose the GW strains into five spatial regions and find that strains are initially largest in the PNS surface layers from accretion and later largest from the Ledoux convective and convective overshoot regions of the PNS. We compute the fractional GW luminosity as a function of enclosed radius and observe that most of the luminosity moves from the PNS surface to deep within the PNS at later times. Using a self-consistent perturbative analysis, we investigate the evolution of the oscillation modes of the PNS. We find that the frequency of the evolving high-frequency component of the GW signal is well matched to the eigenfrequency evolution of the ${}^2g_2$-, ${}^2g_1$-, and ${}^2f$-modes over time. We show that the ${}^2g$-modes emit most of their power in GW initially from the PNS surface region, but within a few 100 ms after bounce, it is the convective overshoot region of the PNS that emits the most GW power for the ${}^2g_1$-mode. Eventually, the ${}^2f$-mode is the dominant mode producing GWs, and they are emitted primarily from the convective overshoot region. Thus, we show that, while the GW emission is global, it is possible to source the dominant contributions to it. We find that the source of the high-frequency GW emission from the PNS in CCSN is more complex than assessed by other methods, as well as time dependent, first emitted by ${}^2g$-modes driven by accretion onto the PNS and later emitted by the ${}^2f$-mode driven by sustained Ledoux convection.

astro-ph.HE↗

arXiv2024

Dependence of the Reconstructed Core-Collapse Supernova Gravitational Wave High-Frequency Feature on the Nuclear Equation of State, in Real Interferometric Data

We present an analysis of gravitational wave (GW) predictions from five two-dimensional Core Collapse Supernova (CCSN) simulations that varied only in the Equation of State (EOS) implemented. The GW signals from these simulations are used to produce spectrograms in the absence of noise, and the emergent high-frequency feature (HFF) is found to differ quantitatively between simulations. Below 1 kHz, the HFF is well approximated by a first-order polynomial in time. The resulting slope was found to vary between 10-50% across all models. Further, using real interferometric noise we investigated the current capabilities of GW detectors to resolve these differences in HFF slope for a Galactic CCSN. We find that for distances up to 1 kpc, current detectors can resolve HFF slopes that vary by at least 30%. For further Galactic distances, current detectors are capable of distinguishing the upper and lower bounds of the HFF slope for groupings of our models that varied in EOS. With the higher sensitivity of future GW detectors, and with improved analysis of the HFF, our ability to resolve properties of the HFF will improve for all Galactic distances. This study shows the potential of using the HFF of CCSN produced GWs to provide insight into the physical processes occurring deep within CCSN during collapse, and in particular its potential to further constrain the EOS through GW detection.

astro-ph.HE↗

arXiv2024

Detecting Gravitational Wave Memory in the Next Galactic Core-Collapse Supernova

We present an approach to detecting (linear) gravitational wave memory in a Galactic core-collapse supernova using current interferometers. Gravitational wave memory is an important prediction of general relativity that has yet to be confirmed. Our approach uses a combination of Linear Prediction Filtering and Matched-Filtering. We present the results of our approach on data from core-collapse supernova simulations that span a range of progenitor mass and metallicity. We are able to detect gravitational wave memory out to 10 kpc. We also present the False Alarm Probabilities assuming an On-Source Window compatible with the presence of a neutrino detection. Errata: The neutrino-induced gravitational waveforms, a component of the total waveforms used to demonstrate the efficacy of the proposed detection method for gravitational wave memory, were computed incorrectly. They were underestimated by a factor of $4\pi$. As a result, the detection results improve and, most important, our primary conclusions are reinforced. In particular, with the corrected waveforms, see Fig. 1 and Fig. 3, the signal for D9.6-3D is in fact detectable at 1 kiloparsec, see Fig. 6 and Fig. 4. The corrected fit parameters are presented in Table 1. The false alarm probability for all three signals is impacted, as shown in Fig. 5. Fig. 5 demonstrates that our proposed method can reliably detect the D9.6-3D signal at 1 kpc for all cutoff values, but our conclusions regarding the inability to detect this signal at 10 and 100 kpc remain the same. We see a boost in the detectability of the D15-3D and D25-3D signals. We now obtain a lower false alarm probability at 10 and 100 kpc. The authors would like to acknowledge Lella et al. [87] for pointing out the discrepancy between our computed neutrino-induced waveforms and theirs, which prompted us to investigate the discrepancy and which led to the discovery of our error.

astro-ph.HE↗

arXiv2024

Gravitational Waves from Neutrino-Driven Core Collapse Supernovae: Predictions, Detection, and Parameter Estimation

Three-dimensional modeling has reached a level of maturity to provide detailed predictions of the gravitational wave emission in neutrino-driven core collapse supernovae. We review the status of these modeling efforts, current predictions for core collapse supernova gravitational wave emission, and the status of algorithms for the detection of core collapse supernova gravitational waves and the estimation of physical parameters associated with these events, which we hope to use to cull information about the central engine.

astro-ph.HE↗

arXiv2023

DG-IMEX Method for a Two-Moment Model for Radiation Transport in the $\mathcal{O}(v/c)$ Limit

We consider particle systems described by moments of a phase-space density and propose a realizability-preserving numerical method to evolve a spectral two-moment model for particles interacting with a background fluid moving with nonrelativistic velocities. The system of nonlinear moment equations, with special relativistic corrections to $\mathcal{O}(v/c)$, expresses a balance between phase-space advection and collisions and includes velocity-dependent terms that account for spatial advection, Doppler shift, and angular aberration. This model is closely related to the one promoted by Lowrie et al. (2001; JQSRT, 69, 291-304) and similar to models currently used to study transport phenomena in large-scale simulations of astrophysical environments. The method is designed to preserve moment realizability, which guarantees that the moments correspond to a nonnegative phase-space density. The realizability-preserving scheme consists of the following key components: (i) a strong stability-preserving implicit-explicit (IMEX) time-integration method; (ii) a discontinuous Galerkin (DG) phase-space discretization with carefully constructed numerical fluxes; (iii) a realizability-preserving implicit collision update; and (iv) a realizability-enforcing limiter. In time integration, nonlinearity of the moment model necessitates solution of nonlinear equations, which we formulate as fixed-point problems and solve with tailored iterative solvers that preserve moment realizability with guaranteed convergence. We also analyze the simultaneous Eulerian-frame number and energy conservation properties of the semi-discrete DG scheme and propose an "energy limiter" that promotes Eulerian-frame energy conservation. Through numerical experiments, we demonstrate the accuracy and robustness of this DG-IMEX method and investigate its Eulerian-frame energy conservation properties.

math.NA↗

arXiv2023

A Parametric Study of the SASI Comparing General Relativistic and Nonrelativistic Treatments

We present numerical results from a parameter study of the standing accretion shock instability (SASI), investigating the impact of general relativity (GR) on the dynamics. Using GR hydrodynamics with GR gravity, and nonrelativistic (NR) hydrodynamics with Newtonian gravity, in an idealized model setting, we vary the initial radius of the shock and, by varying its mass and radius in concert, the proto-neutron star (PNS) compactness. We investigate four compactnesses expected in a post-bounce core-collapse supernova (CCSN). We find that GR leads to a longer SASI oscillation period, with ratios between the GR and NR cases as large as 1.29 for the highest-compactness suite. We also find that GR leads to a slower SASI growth rate, with ratios between the GR and NR cases as low as 0.47 for the highest-compactness suite. We discuss implications of our results for CCSN simulations.

astro-ph.HE↗

arXiv2023

Characterizing the gravitational wave temporal evolution of the gmode fundamental resonant frequency for a core collapse supernova: A neural network approach

We present a methodology based on the implementation of a fully connected neural network to estimate the gravitational wave (GW) temporal evolution of the gmode fundamental resonant frequency for a Core Collapse Supernova (CCSN). To perform the estimation, we construct a training data set, using synthetic waveforms, that serves to train the ML algorithm, and then use several CCSN waveforms to test the model. According to the results obtained from the implementation of our model, we provide numerical evidence to support the classification of progenitors according to their degree of rotation. The relative error associated with the estimate of the slope of the resonant frequency versus time for the GW from CCSN signals is within $13\%$ for the tested candidates included in this study. This method of classification does not require priors or templates, it is based on physical modelling, and can be combined with studies that classify the progenitor with other physical features.

gr-qc↗

arXiv2022

Comparison of the Core-Collapse Evolution of Two Nearly Equal Mass Progenitors

We compare the core-collapse evolution of a pair of 15.8 $M_\odot$ stars with significantly different internal structures, a consequence of bimodal variability exhibited by massive stars during their late evolutionary stages. The 15.78 and 15.79 $M_\odot $ progenitors have core masses of 1.47 and 1.78 $M_\odot$ and compactness parameters $\xi_{1.75}$ of 0.302 and 0.604. The core collapse simulations are carried out in 2D to nearly 3 s post-bounce and show substantial differences in the times of shock revival and explosion energies. The 15.78 $M_\odot$ model explodes promptly at 120 ms post-bounce when a strong density decrement at the Si--Si/O shell interface encounters the stalled shock. The 15.79 $M_\odot$ model, which lacks the density decrement, takes 100 ms longer to explode but ultimately produces a more powerful explosion. Larger mass accretion rate of the 15.79 $M_\odot$ model during the first 0.8 s post-bounce results in larger $\nu_{e}$/$\bar \nu_{e}$ luminosities and rms energies. The $\nu_{e}$/$\bar \nu_{e}$ luminosities and rms energies arising from the inner core are also larger in the 15.79 $M_\odot$ model throughout due to the larger negative temperature gradient of this core due to greater adiabatic compression. Larger luminosities and rms energies in the 15.79 $M_\odot$ model and a flatter and higher density heating region, result in more energy deposition behind the shock and more ejected matter with higher enthalpy. We find the ejected $^{56}$Ni mass of the 15.79 $M_\odot$ model is more than double that of the 15.78 $M_\odot$ model. Most of the ejecta in both models is moderately proton-rich, though counterintuitively the highest electron fraction ($Y_e=0.61$) ejecta in either model is in the less energetic 15.78 $M_\odot$ model while the lowest electron fraction ($Y_e=0.45$) ejecta in either model is in the 15.79 $M_\odot$ model.

astro-ph.SR↗

arXiv2022

Flash-X, a multiphysics simulation software instrument

Flash-X is a highly composable multiphysics software system that can be used to simulate physical phenomena in several scientific domains. It derives some of its solvers from FLASH, which was first released in 2000. Flash-X has a new framework that relies on abstractions and asynchronous communications for performance portability across a range of increasingly heterogeneous hardware platforms. Flash-X is meant primarily for solving Eulerian formulations of applications with compressible and/or incompressible reactive flows. It also has a built-in, versatile Lagrangian framework that can be used in many different ways, including implementing tracers, particle-in-cell simulations, and immersed boundary methods.

physics.comp-ph↗

arXiv2022

Core Collapse Supernova Gravitational Wave Emission for Progenitors of 9.6, 15, and 25 Solar Masses

We present gravitational wave emission predictions based on three core collapse supernova simulations corresponding to three different progenitor masses. The masses span a large range, between 9.6 and 25 Solar masses, are all initially non-rotating, and are of two metallicities: zero and Solar. We compute both the temporal evolution of the gravitational wave strains for both the plus and the cross polarizations, as well as their spectral decomposition and characteristic strains.

astro-ph.SR↗