\[\begin{equation} \frac{dw}{du}=\frac{dw}{dv}\frac{dv}{du} \end{equation} \]
import tensorflow as tf
import flowpm
# Defines integration steps
stages = np.linspace(0.1, 1.0, 10, endpoint=True)
initial_conds = flowpm.linear_field(32, # size of the cube
100, # Physical size
ipklin, # Initial powerspectrum
batch_size=16)
# Sample particles and displace them by LPT
state = flowpm.lpt_init(initial_conds, a0=0.1)
# Evolve particles down to z=0
final_state = flowpm.nbody(state, stages, 32)
# Retrieve final density field
final_field = flowpm.cic_paint(tf.zeros_like(initial_conditions),
final_state[0])
with tf.Session() as sess:
sim = sess.run(final_field)
\[\begin{equation} \kappa_{born}(\boldsymbol{\theta},\chi_s)= \frac{3H_0^2 \Omega_m}{2c^2} \int_0^{\chi_s} d\chi \frac{\chi}{a(\chi)} W(\chi,\chi_s) \delta(\chi \boldsymbol{\theta},\chi). \end{equation} \]
Thank you !