### Limber approximation

**(Limber equation, Limber formula)**
(formula approximating the density of galaxies in some direction)

The **Limber approximation** is a formula (the **Limber formula**
or **Limber equation**) used for relating observation
with the density of galaxies at distances. It makes simplifying
assumptions, which simplifies the math, and has been used for the
last few decades in cosmological studies of distant galaxies,
including analysis of the effects of gravitational lensing.
The **relativistic Limber equation** is a version adjusted to
reflect relativity.

(*mathematics,galaxies*)
**Further reading:**

https://ui.adsabs.harvard.edu/abs/1953ApJ...117..134L/abstract

https://ui.adsabs.harvard.edu/abs/2007A%26A...473..711S/abstract

http://www.astro.ipm.ir/Limber_equation.pdf

https://ui.adsabs.harvard.edu/abs/1978QJRAS..19..353R/abstract

Index