# zieglerk/multivariate_polynomials

Generating Functions for Special Multivariate Polynomials
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# Generating Functions for Special Multivariate Polynomials

This Python-module computes generating functions for the number of some special multivariate polynomials over finite fields. The accompanying paper [GVZ13] also provides proofs and asymptotics with explicit error terms.

## Module

multi-def.sage
run within Sage to obtain symbolic expressions (q) for the number of reducible/s-powerful/absolutely irreducible polynomials at degree n in r variables over GF(q).

## Usage

\$ sage -q

Then, compute generating functions up to the desired degree. For example, the number of reducible, bivariate monic polynomials at degree 10 over GF(q) is:

sage: RR(2, z, 10).coeff(z^10)
q^56 + 2*q^55 + 2*q^54 + 2*q^53 + 2*q^52 + 2*q^51 + 2*q^50 +
3*q^49 + 3*q^48 + 2*q^47 - q^45 + q^43 - q^41 - 3/2*q^40 + q^39 +
5/2*q^38 - 11/2*q^36 - 9*q^35 - 23/2*q^34 - 15*q^33 - 16*q^32 -
9*q^31 + 19/2*q^30 + 30*q^29 + 93/2*q^28 + 46*q^27 + 31/2*q^26 -
181/5*q^25 - 147/2*q^24 - 58*q^23 + 2*q^22 + 53*q^21 +
509/10*q^20 + 15/2*q^19 - 25*q^18 - 41/2*q^17 - 1/2*q^16 +
15/2*q^15 + 2*q^14 - 5/2*q^13 - 3/2*q^12 + q^11 + 17/10*q^10 +
1/2*q^9 - 1/2*q^8 - 1/2*q^7 + 3/10*q^5 + 1/10*q^4 - 1/5*q^2 -
1/10*q

And the number of trivariate, squareful monic polynomials at degree 5 over GF(q) is:

sage: SS(3, 2, z, 5).coeff(z^5)
q^55 + q^54 + q^53 + q^52 + q^51 + q^50 + q^49 + q^48 + q^47 +
q^46 + q^45 + q^44 + q^43 + q^42 + q^41 + q^40 + q^39 + q^38 +
q^37 + q^36 + q^35 - q^22 - 2*q^21 - 3*q^20 - 3*q^19 - 3*q^18 -
3*q^17 - 3*q^16 - 3*q^15 - 3*q^14 - 3*q^13 - 3*q^12 - 3*q^11 -
3*q^10 - 2*q^9 + 3*q^7 + 5*q^6 + 5*q^5 + 3*q^4 + q^3

Finally, the number of absolutely absolutely irreducible, bivariate monic polynomials at degree 7 over GF(q) is:

sage: AA(2, z, 7).coeff(z^7)
q^35 + q^34 + q^33 + q^32 + q^31 + q^30 - q^28 - 2*q^27 - 2*q^26 -
3*q^25 - 3*q^24 - 3*q^23 - 2*q^22 + 3*q^20 + 8*q^19 + 9*q^18 +
4*q^17 - 5*q^16 - 10*q^15 - 6*q^14 + 2*q^13 + 5*q^12 + 2*q^11 -
q^10 - q^9

## Requirements

This code requires the free mathematical software [Sage] which is available for download at http://www.sagemath.org and as cloud service at https://cloud.sagemath.org. It has been tested under GNU/Linux with Sage 6.4.

## References

 [GVZ13] Joachim von zur Gathen, Alfredo Viola & Konstantin Ziegler (2013). Counting reducible, powerful, and relatively irreducible multivariate polynomials over finite fields. SIAM Journal on Discrete Mathematics 27(2):855–891. URL http://dx.doi.org/10.1137/110854680. Also available at http://arxiv.org/abs/0912.3312. Extended Abstract in Alejandro López-Ortiz (ed.), Proceedings of LATIN 2010, Oaxaca, Mexico, volume 6034 of Lecture Notes in Computer Science, 243–254 (2010).
 [Sage] W. A. Stein et al. (2014). Sage Mathematics Software (Version 6.4). The Sage Development Team. URL http://www.sagemath.org.

## Author

• Konstantin Ziegler (2013-12-24): initial version