arXiv subjects

Caio B. de S. Nascimento

Publications and source records attributed to Caio B. de S. Nascimento.

4 recordsLinked to original sources

arXiv2026

Kinetic Theory of the EFTofLSS : A Halo-Based Approach

The Effective Field Theory of Large Scale Structure (EFTofLSS) provides a coarse-grained description of the non-linear gravitational clustering of dark matter, in which the effects of short-scale physics are encoded in an effective stress tensor and a set of counterterms. In this work, we develop a framework to investigate the physical origin of these counterterms by relating the effective stress tensor to the dynamics of individual dark matter halos in cosmological N-body simulations. We find that halo accretion contributes to the trace of the halo-based effective stress tensor, contributing to the background pressure and effective sound speed, while anisotropic accretion generates the traceless part, consequently contributing to the shear viscosity. For the halo population with $M_\mathrm{vir}>10^{12}\,M_\odot/h$, we find that halos account for $\sim\!95\%$, $\sim\!85\%$, and $\sim\!70\%$ of the full box background pressure, effective sound speed, and shear viscosity, respectively, depending on the EFT cutoff scale. The contributions to the counterterms are dominated by cluster-scale halos, $M_\mathrm{vir} \sim 10^{14} - 10^{15}\,M_\odot/h$ and halos with larger inflow rates, supporting an interpretation in terms of accretion-driven, out-of-equilibrium dynamics. Our results provide a short-scale, kinetic-theory interpretation of the EFTofLSS counterterms and establish a framework for connecting the properties and dynamics of short-scale structures to physics-informed priors for large-scale cosmological observables.

astro-ph.CO↗

arXiv2026

Dark winds on the horizon: Prospects for detecting neutrino and hot dark matter wakes in large-scale structure

We explore the cosmological signatures of neutrino and Hot Dark Matter (HDM) wakes, which refers to the preferential accumulation of neutrinos (or, more broadly, HDM particles) downstream of moving cold dark matter structures. We improve on existing theoretical models, and provide forecasts for the detectability of the effect in future surveys under more realistic conditions than previously considered in the literature. We show that neutrino and HDM wakes are unlikely to be ever observed with the most natural tracer of a hot subcomponent of the total dark matter on cosmological scales, i.e. 2D weak lensing surveys. However, the effect can be detected at a high significance with idealistic 3D maps of a tracer of HDM, for sufficiently small values of the effective free-streaming length (e.g. present-day values of $k_{\textrm{fs},0} \gtrsim 0.03\textrm{Mpc}^{-1}$ to reach $\textrm{SNR} \gtrsim 1$, for a HDM species accounting for a percent of the total dark matter). HDM wakes are a smoking gun of the effects of free-streaming, which cannot be mimicked by changes to the background expansion history (such as allowing for the dark energy to be dynamical), and hence offer another avenue to search for massive neutrinos, and hot subcomponents of the total dark matter more broadly, in a way that complements traditional observables.

astro-ph.CO↗

arXiv2026

Breaking the $f_{\text{NL}}$--$b_ϕ$ degeneracy with the time evolution of tracer number counts

Constraining local primordial non-Gaussianity through scale-dependent bias requires an accurate determination of the PNG bias parameter $b_ϕ$, which is completely degenerate with $f_\mathrm{NL}$ in the galaxy power spectrum. The standard universality relation predicts $b_ϕ$ from the linear bias, but breaks down for realistic galaxy populations due to PNG assembly bias. The time evolution estimator offers a promising alternative, inferring $b_ϕ$ from the redshift evolution of tracer number counts. We test it against the separate universe estimator using the IllustrisTNG and SIMBA suites of CAMELS. Our main contribution is to demonstrate that the estimator can be extended to realistic observer-frame photometric selections, provided correction factors derivable from the galaxy SEDs are applied to account for luminosity-distance dimming and $K$-corrections. We further show that physical evolution not directly tracing the growth of matter fluctuations can also be corrected under assumptions about the star formation history: magnitude cuts require correcting for passive stellar fading, after which agreement with the separate universe estimator is restored. This establishes the robustness of the time evolution estimator of PNG bias with realistic survey selections, paving the way to future applications with real data.

astro-ph.CO↗

arXiv2022

Snowmass2021 Theory Frontier White Paper: Data-Driven Cosmology

Over the past few decades, astronomical and cosmological data sets firmly established the existence of physics beyond the Standard Model of particle physics by providing strong evidence for the existence of dark matter, dark energy, and non-zero neutrino mass. In addition, the generation of primordial perturbations most likely also relies on physics beyond the Standard Model of particle physics. Theory work, ranging from models of the early universe in string theory that that led to novel phenomenological predictions to the development of effective field theories to large-scale cosmological simulations that include the physics of galaxy evolution, has played a key role in analyzing and interpreting these data sets and in suggesting novel paths forward to isolate the origins of this new physics. Over the next decade, even more sensitive surveys are beginning to take data and are being planned. In this white paper, we describe key areas of the theory program that will be needed to optimize the physics return on investment from these new observational opportunities.

astro-ph.CO↗