# Solving PDEs using Taylor series

I'm thinking of solving a Partial differential algebraic equation using multidimensional polynomial (i.e. Taylor series). Consider the PDAE:

$$\mathbf F \left( \mathbf x, \mathbf y, \frac{\partial y_i}{\partial x_j}, \frac{\partial^2 y_i}{\partial x_j \partial x_n}, \ldots \right) = \mathbf 0 \, , \left\{1<i<m,1<j<n\right\} \, ,\tag{1}$$

with a boundary/initial condition of

$$\mathbf G \left( \mathbf y, \frac{\partial y_i}{\partial x_j}, \frac{\partial^2 y_i}{\partial x_j \partial x_n}, \ldots \right)_{\partial \Omega} = \mathbf 0 \, . \tag{2}$$

Now if we approximate $\mathbf y$ with a multidimensional polynomial:

$$y_i \approx \sum_{l_1=0}^{o_1} \ldots \sum_{l_n=0}^{o_n} a_{i\left(l_1, \ldots, l_n\right)}x_1^{l_1} \ldots x_n^{l_n} \, , \tag{3}$$

and substitute it in Eq. 1 , we get system of nonlinear equations of $a_{i\left(l_1, \ldots, l_n\right)}$s. Using the boundary conditions this system of nonlinear equations can be solved to find $a$s.

I want to write a Matematica macro to automate this process.

• Where should I start?
• Are there any example about that?
• Has there ever been an attempt to do so? even with other symbolic CAS software

• Something like AsymptoticDSolveValue? Read this mathematica blog post – rhermans Jul 27 '18 at 12:48
• @rhermans awesome. exactly. let me check this out and come back here. – Foad Jul 27 '18 at 12:49
• @rhermans I'm gonna try it on this which I want to finally solve and then post a new question if I had any issues. as far as this question matters I think I have found a solution to work on. – Foad Jul 27 '18 at 13:03
• Realted 177120 168064 25363. – rhermans Jul 27 '18 at 13:08
• I suggest that you show the due diligence in your question. Edit and explain how/why the related questions and the documentation for AsymptoticDSolveValue do not answer your need. – rhermans Jul 27 '18 at 13:30