| Date | Event Type | Speaker | |
| 06/04/2025 | HEP Seminar | Victor Gorbenko [ + ] | |
| 06/10/2025 | Group Meeting | [ + ] | |
| 06/12/2025 | Informal Astro Talk | Nanoom Lee [ -- ] | |
| Title: Rapid and accurate numerical evolution of linear cosmological perturbations with non-cold relics Abstract: Accurately modeling linear cosmological perturbations requires solving the Boltzmann equation. For non-cold relics such as massive neutrinos, this typically involves solving a momentum-dependent Boltzmann hierarchy, an infinite set of coupled differential equations. While efficient numerical treatments such as hierarchy truncation and fluid approximation for massive neutrinos (as implemented in the Boltzmann solver CLASS) enable practical computation, they come with limitations, especially at small scales or in non-standard scenarios. In this talk, I will describe these limitations and present a new numerical approach that replaces the Boltzmann hierarchy for non-cold relics with a set of integral equations. These equations take the form of convolutions and are solved iteratively with the rest of the system. This method has been implemented in CLASS and applied to massive neutrino perturbations as a demonstration. The results match the accuracy of a fully converged Boltzmann hierarchy while offering substantial speedups, depending on the desired precision and the range of scales considered. This new framework provides a practical and robust alternative to the truncated Boltzmann hierarchy, particularly for studying beyond-$Lambda$CDM non-cold relics with signatures on small scales. The implementation is publicly available as CLASSIER (CLASS Integral Equation Revision) at https://github.com/nanoomlee/CLASSIER. (2:00 PM - 2:30 PM, 726 Broadway, 901, Sm Conf) | |||
| 06/12/2025 | Pate Group Meeting | Monica Pate [ + ] | |