How new physics affects primordial neutrinos decoupling: Direct Simulation Monte Carlo approach

TL;DR

This paper introduces a novel neutrino Direct Simulation Monte Carlo method to study how new physics could have influenced primordial neutrino decoupling, offering a more transparent and efficient tool for analyzing early universe conditions.

Contribution

The paper develops a new, model-independent DSMC approach for simulating primordial neutrino decoupling, addressing limitations of existing methods and enabling exploration of new physics effects.

Findings

Demonstrated the DSMC method on toy scenarios of early universe evolution

Showcased the method's transparency and computational efficiency

Provided insights into how new physics could alter neutrino decoupling

Abstract

Cosmological observations from Big Bang Nucleosynthesis and the Cosmic Microwave Background (CMB) offer crucial insights into the Early Universe, enabling us to trace its evolution back to lifetimes as short as 0.01 seconds. Upcoming CMB spectrum measurements will achieve unprecedented precision, allowing for more accurate extraction of information about the primordial neutrinos. This provides an opportunity to test whether their properties align with the predictions of the standard cosmological model or indicate the presence of new physics that influenced the evolution of the MeV-temperature plasma. A key component in understanding how new physics may have affected primordial neutrinos is solving the neutrino Boltzmann equation. In this paper, we address this question by developing a novel approach -- neutrino Direct Simulation Monte Carlo (DSMC). We discuss it in-depth, highlighting its model independence, transparency, and computational efficiency -- features that current state-of-the-art methods lack. Then, we introduce a proof-of-concept implementation of the neutrino DSMC and apply it to several toy scenarios, showcasing key aspects of the primordial plasma's evolution in the presence of new physics.