Relativistic Radiative Transfer in arbitrary spacetime

🎯 Goal

Solving the Relativistic Radiative Transfer first in Schwarzschild and Kerr spacetime and then for arbitrary spacetime, for Emission Intensity (Emissivity) , for an observer in equatorial plane (for starters) and then at any arbitrary angle.

💡 Possible solutions

https://arxiv.org/abs/1801.10452 https://arxiv.org/abs/1602.03184 http://discovery.ucl.ac.uk/1426969/1/Younsi_Ziri_741337 _Ziri_Thesis.pdf

📋 Steps to solve the problem

• Comment below about what you’ve started working on.
• Add, commit, push your changes
• Submit a pull request and add this in comments - Addresses #<put issue number here>
• Ask for a review in comments section of pull request
• Celebrate your contribution to this project 🎉

[ritzvik]

Hey @ritzvik very sorry for the delay , so I’ve outlined some basic parameters based on RAPTOR1 that we have to define for radiative transfer those being - 1.4 velocity comprising of the wave functions of the photons in list along with a helper method to compute it from photons position/velocity vector 2. differential step size comprising of an appropriate step size based on position or velocity vectors or differential lambda 3. frequencies of the photons 3.intensity field vector and a separate variable for current intensity value 4.tau vector

So basically after figuring out which of these params exist already in the codebase should I start defining those which don’t in a new class ? or in each spacetime class.

Also apparently for runge kutta , epy uses RK45 function but im a bit confused on how to use it could you clarify fun parameter used in it ?

I didn’t go through the paper, I will go through it at a later stage. Regarding fun parameter, it is used to pass a function(which may be a vector function) to calculate f(x) given x(which may be vector, again). This is because of differential equation y' = f(x), each new y is calculated by y=y+h*f(x), where h is the step-size. This is the simplest way of calculating solutions of ODE numerically, although RK45 involves a much more complicated algorithm.

[Bhavam]

Hey @ritzvik very sorry for the delay , so I’ve outlined some basic parameters based on RAPTOR1 that we have to define for radiative transfer those being - 1.4 velocity comprising of the wave functions of the photons in list along with a helper method to compute it from photons position/velocity vector 2. differential step size comprising of an appropriate step size based on position or velocity vectors or differential lambda 3. frequencies of the photons 3.intensity field vector and a separate variable for current intensity value 4.tau vector

So basically after figuring out which of these params exist already in the codebase should I start defining those which don’t in a new class ? or in each spacetime class.

Also apparently for runge kutta , epy uses RK45 function but im a bit confused on how to use it could you clarify fun parameter used in it ?