Neutrino winds on the sky

Abstract

We develop a first-principles formalism to compute the distortion to the relic neutrino density field caused by the peculiar motions of large-scale structures. This distortion slows halos down due to dynamical friction, causes a local anisotropy in the neutrino-CDM cross-correlation, and reduces the global cross-correlation between neutrinos and CDM. The local anisotropy in the neutrino-CDM cross-spectrum is imprinted in the three point cross-correlations of matter and galaxies, or the bispectrum in Fourier space, producing a signal peaking at squeezed triangle configurations. This bispectrum signature of neutrino masses is not limited by cosmic variance or potential inaccuracies in the modeling of complicated nonlinear and galaxy formation physics, and it is not degenerate with the optical depth to reionization. We show that future surveys have the potential to detect the distortion bispectrum.

Neutrino mass measurement with cosmic gravitational focusing

“…Comparing the Hubble parameter term and the second term in the same bracket of eq. (2.10), the above approximation happens at |p|/m ν ≫ H∆x, namely, ∆x ≪ 7.4 Mpc (0.1eV/m ν )(1 + z) −1/2 [75] which is exactly the scale for neutrino free streaming as explored in [77]. In addition, the DM halo gravitational potential also varies slowly with time, Φ ∼ 0.…”

“…In addition to the standard cosmology approaches, we explore an additional and independent method for measuring neutrino masses based on the cosmic gravitational focusing between the CνF and dark matter halos [74][75][76][77]. With dependence on the mass fourth power instead of the usual linear neutrino mass sum, the cosmic gravitational focusing is more sensitive to the neutrino masses and can provide a complementary measurement.…”

“…Below the neutrino free-streaming scale k fs , the neutrino overdensity is suppressed by a factor (k fs /|k|) 2 compared to the matter overdensity δ m . To extend beyond the static Boltzmann approximation, we can simply replace the factor (k fs /|k|) 2 with (k fs /|k|) 2 /(1 + k fs /|k|) 2[77].…”

Local clustering of relic neutrinos: comparison of kinetic field theory and the Vlasov equation

“…The solution to the linearized version of the Vlasov equation (5.1) is well-known either as Gilbert equation or linear response 2 (see e.g. [20,21,[28][29][30][31][32][33]). At higher orders, solutions to the Vlasov equation can be found in [37].…”

“…Concerning the first question, we already noted in [8] that the analytical expression for the number density from first-order KFT looks similar to the solution of the linearized Vlasov equation, often referred to as linear response or the Gilbert equation (see e.g. [20,21,[28][29][30][31][32][33]). In this work, we illustrate by explicit derivation that these two approaches are equivalent JCAP07(2024)050 up to second order in perturbation theory.…”