About

Dr. Kimberly Boddy is a theoretical physicist working at the intersection of cosmology, particle physics, and astrophysics. She explores the fundamental properties of our Universe by analyzing data from cosmological and astrophysical observations. Her research topics include dark matter, cosmological structure formation, and gravitational waves. She is an Associate Professor and the Director of the Texas Center for Cosmology and Astroparticle Physics at the University of Texas at Austin. Dr. Boddy is affiliated with the Weinberg Institute and the Weinberg Theory Group, contributing to the understanding of the universe through her work in cosmology, astronomy-astrophysics, theory, gravitational physics, and computational/theoretical fields.

Research topics

• Physics
• Astronomy
• Astrophysics
• Artificial Intelligence
• Computer Science
• Quantum mechanics
• Optics
• Data science
• Theoretical physics
• Particle physics

Selected publications

• CMB constraints on dark matter-proton scattering: investigating prior-volume effects using profile likelihoods

  ArXiv.org · 2026-03-26

  articleOpen accessSenior author

  We present profile-likelihood constraints on velocity-independent dark matter-proton scattering, including cases in which only a fraction of dark matter has such non-gravitational interactions. Frequentist profile-likelihood techniques provide prior-independent constraints, circumventing prior-volume effects that we show arise in Bayesian constraints on this model. In the limit where the scattering cross section or the fraction of interacting dark matter approaches zero, the other interacting dark matter model parameters become unconstrained, causing the posterior distribution to favor that region of parameter space. Using Planck 2018 cosmic microwave background anisotropy data, we find a clear impact of prior-volume effects on the posteriors used to place constraints on dark matter scattering. Compared to the frequentist analysis, the Bayesian method consistently overestimates the constraints on the cross section. Given the potentially biased upper limits on models subject to prior-volume effects, such as this one, we recommend supplementing Bayesian constraints with frequentist statistics to better assess the impact of priors.

  PublisherOA PDF

• CMB Limits on the Absorption of Light Vector and Axial-Vector Dark Matter

  ArXiv.org · 2026-05-08

  articleOpen accessSenior author

  Leptophilic sub-MeV spin-1 dark matter (DM) can be converted into a photon via inelastic scattering with a free electron or absorption by a neutral hydrogen atom in the primordial plasma. We study for the first time the impact of the energy injection resulting from such processes on cosmic microwave background (CMB) anisotropies. We obtain upper limits on the vector and axial-vector DM-electron couplings using Planck 2018 temperature, polarization, and lensing data for DM masses between 100 eV and 100 keV. We find that, due to the suppression of the hydrogen atomic form factor at high energies, inelastic scattering provides the dominant constraint for DM masses above the keV scale. At lower masses, hydrogen ionization through DM absorption is the leading channel, driven by the higher efficiency of post-recombination energy injection in modifying the free-electron fraction. Although the bounds we derive are considerably weaker than existing laboratory and astrophysical limits, they provide a robust and independent cosmological probe of leptophilic DM interactions.

  PublisherOA PDF

• CMB Limits on the Absorption of Light Vector and Axial-Vector Dark Matter

  arXiv (Cornell University) · 2026-05-08

  preprintOpen accessSenior author

  Leptophilic sub-MeV spin-1 dark matter (DM) can be converted into a photon via inelastic scattering with a free electron or absorption by a neutral hydrogen atom in the primordial plasma. We study for the first time the impact of the energy injection resulting from such processes on cosmic microwave background (CMB) anisotropies. We obtain upper limits on the vector and axial-vector DM-electron couplings using Planck 2018 temperature, polarization, and lensing data for DM masses between 100 eV and 100 keV. We find that, due to the suppression of the hydrogen atomic form factor at high energies, inelastic scattering provides the dominant constraint for DM masses above the keV scale. At lower masses, hydrogen ionization through DM absorption is the leading channel, driven by the higher efficiency of post-recombination energy injection in modifying the free-electron fraction. Although the bounds we derive are considerably weaker than existing laboratory and astrophysical limits, they provide a robust and independent cosmological probe of leptophilic DM interactions.

  PublisherDOI

• CMB constraints on dark matter-proton scattering: investigating prior-volume effects using profile likelihoods

  arXiv (Cornell University) · 2026-03-26

  preprintOpen accessSenior author

  We present profile-likelihood constraints on velocity-independent dark matter-proton scattering, including cases in which only a fraction of dark matter has such non-gravitational interactions. Frequentist profile-likelihood techniques provide prior-independent constraints, circumventing prior-volume effects that we show arise in Bayesian constraints on this model. In the limit where the scattering cross section or the fraction of interacting dark matter approaches zero, the other interacting dark matter model parameters become unconstrained, causing the posterior distribution to favor that region of parameter space. Using Planck 2018 cosmic microwave background anisotropy data, we find a clear impact of prior-volume effects on the posteriors used to place constraints on dark matter scattering. Compared to the frequentist analysis, the Bayesian method consistently overestimates the constraints on the cross section. Given the potentially biased upper limits on models subject to prior-volume effects, such as this one, we recommend supplementing Bayesian constraints with frequentist statistics to better assess the impact of priors.

  PublisherDOI

• Survival of the most compact: the life and death of satellite halos in self-interacting dark matter

  arXiv (Cornell University) · 2026-03-19

  preprintOpen access

  Self-interacting dark matter (SIDM) models feature short-range interactions between dark matter (DM) particles that lead to larger diversity in the inner parts of galactic rotation curves and potentially unique gravitational lensing signatures. Satellite galaxies and dark subhalos provide a valuable testing ground for such models. We develop a simulation framework to explore subhalo evolution and its gravothermal collapse for velocity- and angle-dependent self-interacting cross section in these SIDM models. Our results are essential for testing these models. We perform N-body simulations, treating the host halo analytically and modelling the scattering-induced subhalo-halo interaction process using virtual host particles, a central innovation of our work. We use the Eddington inversion method to accurately model the local velocity distribution in the halo. Our approach is significantly less computationally expensive than simulations with a fully resolved host, while incorporating tidal stripping and tidal heating. We test both isotropic and forward-dominated self-scattering, which represent limiting cases for the angular dependence of the self-interaction cross section. Environmental effects, especially the scattering-induced subhalo-halo interaction, have a strong impact on the subhalo evolution and drive a complex structural evolution. As a result, SIDM subhalos have a larger range of central densities and density profile slopes compared to collisionless DM. Our cost-efficient simulation framework enables modelling of SIDM subhalos in realistic environments. Our results highlight the necessity of accurately modelling the scattering-induced subhalo-halo interaction to predict SIDM subhalo density profiles. For the SIDM models we investigate, the enhanced diversity in the mass profiles of subhalos would leave an observable imprint on strong lensing systems and satellite galaxies.

  PublisherDOI

• Conversations and deliberations: Non-standard cosmological epochs and expansion histories

  International Journal of Modern Physics A · 2025-03-01 · 12 citations

  article

  This paper summarizes the discussions which took place during the PITT-PACC Workshop entitled “Non-Standard Cosmological Epochs and Expansion Histories,” held in Pittsburgh, Pennsylvania, Sept. 5–7, 2024. Much like the non-standard cosmological epochs that were the subject of these discussions, the format of this workshop was also non-standard. Rather than consisting of a series of talks from participants, with each person presenting their own work, this workshop was instead organized around free-form discussion blocks, with each centered on a different overall theme and guided by a different set of Discussion Leaders. This document is not intended to serve as a comprehensive review of these topics, but rather as an informal record of the discussions that took place during the workshop, in the hope that the content and free-flowing spirit of these discussions may inspire new ideas and research directions.

  PublisherDOI

• Joint 21-cm and CMB forecasts for constraining self-interacting massive neutrinos

  Physical review. D/Physical review. D. · 2025-09-02 · 4 citations

  articleOpen access

  Self-interacting neutrinos provide an intriguing extension to the Standard Model, motivated by both particle physics and cosmology. Recent cosmological analyses suggest a bimodal posterior for the coupling strength ${G}_{\mathrm{eff}}$, favoring either strong or moderate interactions. These interactions modify the scale dependence of the growth of cosmic structures, leaving distinct imprints on the matter power spectrum at small scales, $k>0.1\text{ }\text{ }{\mathrm{Mpc}}^{\ensuremath{-}1}$. For the first time, we explore how the 21-cm power spectrum from the cosmic dawn and the dark ages can constrain the properties of self-interacting massive neutrinos. The effects of small-scale suppression and enhancement in the matter power spectrum caused by self-interacting neutrinos propagate to the halo mass function, shaping the abundance of small- and intermediate-mass halos. It is precisely these halos that host the galaxies responsible for driving the evolution of the 21-cm signal during the cosmic dawn. We find that Hydrogen Epoch of Reionization Array (HERA) at its design sensitivity can improve upon existing constraints on ${G}_{\mathrm{eff}}$ and be sensitive to small values of the coupling, beyond the reach of current and future cosmic microwave background (CMB) experiments. Crucially, we find that the combination of HERA and CMB-Stage 4 can break parameter degeneracies, significantly improving the sensitivity to ${G}_{\mathrm{eff}}$ over either experiment alone. Finally, we investigate the prospects of probing neutrino properties with futuristic Lunar interferometers, accessing the astrophysics-free 21-cm power spectrum during the dark ages. The capability of probing small scales of these instruments will allow us to reach a percent-level constraint on the neutrino self-coupling.

  PublisherOA PDFDOI

• Ultralight Dark Matter Statistics for Pulsar Timing Detection

  arXiv (Cornell University) · 2025-02-21

  preprintOpen access1st authorCorresponding

  Fluctuations in ultralight dark matter produce significant metric perturbations, which may be detected by monitoring the arrival times of light from millisecond pulsars. While searches using this technique are already underway, they do not consistently account for the statistical properties of the dark matter field. The statistics of this field depend on the velocity dispersion of dark matter and, consequently, its coherence length. In the mass range relevant for pulsar timing arrays, the coherence length is comparable to separations between pulsars, making it crucial to incorporate its effects into the analysis. This work presents a consistent statistical method for gravitational direct detection of ultralight dark matter. Our key result is the derivation of the two-point function of the metric fluctuations, which we apply to pulsar timing and discuss its implementation in future searches.

  PublisherDOI

• Ultralight Dark Matter Statistics for Pulsar Timing Detection

  Physical Review Letters · 2025-09-02 · 7 citations

  articleOpen access1st authorCorresponding

  Fluctuations in ultralight dark matter produce significant metric perturbations, which may be detected by monitoring the arrival times of light from millisecond pulsars. While searches using this technique are already underway, they do not consistently account for the statistical properties of the dark matter field. The statistics of this field depend on the velocity dispersion of dark matter and, consequently, its coherence length. In the mass range relevant for pulsar timing arrays, the coherence length is comparable to separations between pulsars, making it crucial to incorporate its effects into the analysis. This Letter presents a consistent statistical method for gravitational direct detection of ultralight dark matter. Our key result is the derivation of the two-point function of the metric fluctuations, which we apply to pulsar timing and discuss its implementation in future searches.

  PublisherOA PDFDOI

• Directly probing neutrino interactions through CMB phase shift measurements

  Physical review. D/Physical review. D. · 2025-12-24 · 4 citations

  articleOpen access

  Perturbations in the cosmic neutrino background produce a characteristic phase shift in the acoustic oscillations imprinted in the anisotropies of the cosmic microwave background (CMB), providing a unique observational probe of neutrino physics. In this work, we explore how this phase shift signature is altered in the presence of neutrino interactions with temperature-dependent scattering rates, motivated by physical constructions for neutrino self-interactions and neutrino-dark matter couplings. A key finding is that the phase shift in these realistic models -- characterized by gradual rather than instantaneous decoupling -- maintains the same functional form as the free-streaming template, with only the asymptotic amplitude decreasing for stronger interactions that delay decoupling. This simple parametrization enables us to directly constrain neutrino interactions through phase shift measurements in the temperature and polarization power spectra from CMB observations. Analyzing the latest data from \textit{Planck}, the Atacama Cosmology Telescope, and the South Pole Telescope, we derive strong constraints on the neutrino decoupling redshift. Our global analysis indicates that neutrinos have been freely streaming since deep within the radiation-dominated epoch. We also explore flavor-dependent scenarios in which only one neutrino species interacts. Overall, our work establishes a signature-driven framework that exploits the clean phase shift signal in the acoustic oscillations of the CMB as a precise and robust probe of non-standard neutrino interactions in the early universe.

  PublisherOA PDFDOI

Recent grants

• Investigating the Nature of Dark Matter throughout Cosmic History

  NSF · $225k · 2021–2024

Frequent coauthors

• Vera Gluscevic

  University of Southern California

  43 shared

• Ethan O. Nadler

  33 shared

• Francis-Yan Cyr-Racine

  21 shared

• Renée Hložek

  University of Toronto

  19 shared

• Risa H. Wechsler

  Kavli Institute for Particle Astrophysics and Cosmology

  19 shared

• Manoj Kaplinghat

  19 shared

• James G. Bartlett

  Centre National de la Recherche Scientifique

  18 shared

• Louis E. Strigari

  18 shared

Education

• SB, Physics

  Massachusetts Institute of Technology

• PhD, Physics

  California Institute of Technology