Physical Cosmology

Lurdes Ondaro Mallea examines whether current models of the kinematic Sunyaev–Zeldovich signal accurately recover diffuse baryons and the strength of astrophysical feedback. The analysis uses hydrodynamic simulations to generate mock stacked measurements for realistic DESI-like galaxy samples, separating contributions from gas density, velocities and nonlinear astrophysics. It tests baryonic changes to density and velocity fields, satellite galaxies, nonlinear velocities and velocity reconstruction. Neglecting satellites can underestimate halo gas fractions at today's measurement precision; further corrections become significant for future datasets. The talk explains how including these effects can improve gas-distribution measurements and assessments of feedback. Online via Zoom. Monday 28 September 2026, 11:00–12:00 PDT (America/Los_Angeles; UTC−7). Follow Join the zoom meeting on the organizer's event page. Lurdes Ondaro Mallea is affiliated with Cambridge. Organized by the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University. This listing advertises the verified remote option.

This seminar derives how dark-matter halo density profiles emerge from hierarchical assembly using the Boltzmann–Poisson equations for a coarse-grained distribution of subhalos in an expanding universe. An exact self-similar solution relates density slope γ to mass growth M proportional to tˢ through γ = 6/(s + 2). Initial collapse gives a prompt γ = 3/2 cusp; hierarchical accretion recovers the Syer–White relation and an attractive n = −2 fixed point with γ = 1; stalled accretion approaches γ = 3. These stages provide a dynamical account of the inner and outer Navarro–Frenk–White profile.

Haruki Ebina discusses the marked power spectrum as a two-point approach to non-Gaussian density information, reducing the data-vector and covariance challenges of direct bispectrum analysis while retaining perturbative modelling. Recent work incorporates survey geometry, bringing applications to observations closer. Time permitting, he will also cover high-redshift DESI Run 2 cosmology and perturbative modelling of fast-radio-burst dispersion measures. Samuel Goldstein presents new constraints on fundamental physics from the cosmic microwave background and large-scale structure: axions using Atacama Cosmology Telescope observations, primordial non-Gaussianity, multi-field inflation using DESI, and component-separated temperature, polarization, thermal Sunyaev–Zeldovich and kinetic Sunyaev–Zeldovich maps from early Simons Observatory data. Speakers: Haruki Ebina, UC Berkeley, and Samuel Goldstein, Columbia University. Organized by Stanford KIPAC. Tuesday 29 September 2026, 10:40–11:30 America/Los_Angeles (PDT). Online via Zoom using Join the zoom meeting on the official event page. The organizer lists the intended audience as Faculty/Staff, Members and Students. Only remote attendance is verified for this listing.

Lyman Page introduces temperature variations and polarization in the cosmic microwave background for researchers outside cosmology, explaining how these measurements underpin the standard cosmological model. He then considers what that model leaves unresolved, especially whether gravitational waves originating in the early Universe are detectable. The talk reviews the Simons Observatory’s experimental search for those primordial signals and its role in addressing this question. Online via Zoom Events in the John Bahcall Colloquium, hosted by the Institute for Underground Science at SURF. The free series welcomes the scientific community across career stages. Wednesday 14 October, 09:00–10:00 MDT (America/Denver), equivalent to 15:00–16:00 UTC. Follow Register on the organizer page, then select this dated session in the Zoom Events registration list.

Haruki Ebina discusses the marked power spectrum as a two-point approach to non-Gaussian density information, reducing the data-vector and covariance challenges of direct bispectrum analysis while retaining perturbative modelling. Recent work incorporates survey geometry, bringing applications to observations closer. Time permitting, he will also cover high-redshift DESI Run 2 cosmology and perturbative modelling of fast-radio-burst dispersion measures. Samuel Goldstein presents new constraints on fundamental physics from the cosmic microwave background and large-scale structure: axions using Atacama Cosmology Telescope observations, primordial non-Gaussianity, multi-field inflation using DESI, and component-separated temperature, polarization, thermal Sunyaev–Zeldovich and kinetic Sunyaev–Zeldovich maps from early Simons Observatory data. Speakers: Haruki Ebina, UC Berkeley, and Samuel Goldstein, Columbia University. Organized by Stanford KIPAC. Tuesday 29 September 2026, 10:40–11:30 America/Los_Angeles (PDT). Online via Zoom using Join the zoom meeting on the official event page. The organizer lists the intended audience as Faculty/Staff, Members and Students. Only remote attendance is verified for this listing.

Lurdes Ondaro Mallea examines whether current models of the kinematic Sunyaev–Zeldovich signal accurately recover diffuse baryons and the strength of astrophysical feedback. The analysis uses hydrodynamic simulations to generate mock stacked measurements for realistic DESI-like galaxy samples, separating contributions from gas density, velocities and nonlinear astrophysics. It tests baryonic changes to density and velocity fields, satellite galaxies, nonlinear velocities and velocity reconstruction. Neglecting satellites can underestimate halo gas fractions at today's measurement precision; further corrections become significant for future datasets. The talk explains how including these effects can improve gas-distribution measurements and assessments of feedback. Online via Zoom. Monday 28 September 2026, 11:00–12:00 PDT (America/Los_Angeles; UTC−7). Follow Join the zoom meeting on the organizer's event page. Lurdes Ondaro Mallea is affiliated with Cambridge. Organized by the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford University. This listing advertises the verified remote option.

Lyman Page introduces temperature variations and polarization in the cosmic microwave background for researchers outside cosmology, explaining how these measurements underpin the standard cosmological model. He then considers what that model leaves unresolved, especially whether gravitational waves originating in the early Universe are detectable. The talk reviews the Simons Observatory’s experimental search for those primordial signals and its role in addressing this question. Online via Zoom Events in the John Bahcall Colloquium, hosted by the Institute for Underground Science at SURF. The free series welcomes the scientific community across career stages. Wednesday 14 October, 09:00–10:00 MDT (America/Denver), equivalent to 15:00–16:00 UTC. Follow Register on the organizer page, then select this dated session in the Zoom Events registration list.

This seminar derives how dark-matter halo density profiles emerge from hierarchical assembly using the Boltzmann–Poisson equations for a coarse-grained distribution of subhalos in an expanding universe. An exact self-similar solution relates density slope γ to mass growth M proportional to tˢ through γ = 6/(s + 2). Initial collapse gives a prompt γ = 3/2 cusp; hierarchical accretion recovers the Syer–White relation and an attractive n = −2 fixed point with γ = 1; stalled accretion approaches γ = 3. These stages provide a dynamical account of the inner and outer Navarro–Frenk–White profile.