Kavli Affiliate: Elise Jennings
| First 5 Authors: Elise Jennings, David Jennings, , ,
| Summary:
The linear growth rate is commonly defined through a simple deterministic relation between the velocity divergence and the matter overdensity in the linear regime. We introduce a formalism that extends this to a nonlinear, stochastic relation between $θ= nabla cdot v({bf x},t)/aH$ and $δ$. This provides a new phenomenological approach that examines the conditional mean $< θ|δ>$, together with the fluctuations of $θ$ around this mean. We measure these stochastic components using N-body simulations and find they are non-negative and increase with decreasing scale from $sim$10% at $k<0.2 h $Mpc$^{-1}$ to 25% at $ksim0.45h$Mpc$^{-1}$ at $z = 0$. Both the stochastic relation and nonlinearity are more pronounced for halos, $M le 5 times 10^{12}M_odot h^{-1}$, compared to the dark matter at $z=0$ and $1$. Nonlinear growth effects manifest themselves as a rotation of the mean $< θ|δ>$ away from the linear theory prediction $-f_{tiny rm LT}δ$, where $f_{tiny rm LT}$ is the linear growth rate. This rotation increases with wavenumber, $k$, and we show that it can be well-described by second order Lagrangian perturbation theory (2LPT) for $k < 0.1 h$Mpc$^{-1}$. The stochasticity in the $θ$ — $δ$ relation is not so simply described by 2LPT, and we discuss its impact on measurements of $f_{tiny rm LT}$ from two point statistics in redshift space. Given that the relationship between $δ$ and $θ$ is stochastic and nonlinear, this will have implications for the interpretation and precision of $f_{tiny rm LT}$ extracted using models which assume a linear, deterministic expression.
| Search Query: arXiv Query: search_query=au:”Elise Jennings”&id_list=&start=0&max_results=3