# D-Algebraic Functions¶

ABSTRACT: We investigate D-algebraic, i.e., differentially-algebraic functions. Those are functions which are solutions of multivariate polynomial equations in the function, its derivatives, and the independent variables. We revisit closure properties of these functions by providing constructive proofs. For the univariate case, we present algorithms to compute differential equations for compositions and arithmetic manipulations of D-algebraic functions and derive bounds for the order of the resulting differential equations. We apply our methods to examples in the sciences.

For instance, the exponential of the Painlevé transcendent of type I is a D-algebraic function. It fullfils the following ADE (see Example 5.7 in our article):

We have described two methods of computations, and each of them yields algorithms.
The algorithms of our second method are implemented in Maple
in the package NLDE (NonLinear algebra and Differential Equations). The package can be downloaded
here `NLDE.mla`

, and its source here `sourceNLDE.mpl`

.
This is a user-friendly interface to the code for any Maple user who wants to try our implelentation.
Questions and comments are welcome. The use of the package is illustrated in the following notebook:

The following file is a Maple worksheet with the same computations.

`DalgebraicFunc-Examples-Maple-Worksheet.mw`

.

The outputs are presented in the following printed pdf:

We also have a Macaulay2 code that implements our first method. The corresponding Jupyter notebook is going to be made available at this place soon.

Project page created: 14/11/2022

Project contributors: Rida Ait El Manssour, Anna-Laura Sattelberger, Bertrand Teguia Tabuguia

Corresponding author of this page: Bertrand Teguia Tabuguia, teguia@mis.mpg.de

Software used: Maple 2022. The implementation works on recent versions of Maple: 2018 to 2022. Macaulay2 (version 1.19.1).

System setup used: Processor: Intel(R) Core(TM) i5-10210U CPU @ 1.60GHz 2.11 GHz, Installed RAM: 16,0 GB (15,8 GB usable), System type: 64-bit operating system, x64-based processor, Edition: Windows 11 Home Version 21H2.