arXiv subjects

Nicolas Faroß

Publications and source records attributed to Nicolas Faroß.

6 recordsLinked to original sources

arXiv2026

Pseudo-Complex Quantifier Elimination

We describe the design of a quantifier elimination framework for the complex numbers in the language of ordered rings supplemented with symbols for the imaginary unit, real parts, imaginary parts, and conjugates. Technically, we use a reduction to real quantifier elimination followed by a heuristic reinterpretation of the results within our complex framework. We present computational examples using a prototypical implementation of our approach in our Python-based open-source system Logic1.

cs.SC↗

arXiv2025

Algorithmic Problems in Categories of Partitions

Categories of partitions are combinatorial structures arising from the representation theory of certain compact quantum groups and are linked to classical diagram algebras such as the Temperley-Lieb algebra. In this paper, we present efficient algorithms and data-structures for partitions of sets and their corresponding category operations, including a concrete implementation in the computer algebra system OSCAR. Moreover, we show that there exists a category of partitions for which the natural computational problems of deciding membership of a given partition as well as counting partitions of a given size are algorithmically undecidable.

cs.DS↗

arXiv2025

On the Number of Real Types of Univariate Polynomials

The real type of a finite family of univariate polynomials characterizes the combined sign behavior of the polynomials over the real line. We derive an explicit formula for the number of real types subject to given degree bounds. For the special case of a single polynomial we present a closed-form expression involving Fibonacci numbers. This allows us to precisely describe the asymptotic growth of the number of real types as the degree increases, in terms of the golden ratio.

cs.SC↗

arXiv2024

Projective Versions of Spatial Partition Quantum Groups

We generalize categories of spatial partitions in the sense of Cébron-Weber by introducing new base partitions. This allows us to construct additional examples of free orthogonal quantum groups but yields the same class of spatial partition quantum groups as before. Further, we use these new base partitions to show that the class of spatial partition quantum groups is closed under taking projective versions and in particular contains the projective version of all easy quantum groups. As an application, we determine the quantum groups corresponding to the categories of all spatial pair partitions and give explicit descriptions of the projective versions of easy quantum groups in terms of spatial partitions.

math.QA↗

arXiv2024

Quantum Automorphism Groups of Hypergraphs

We introduce a quantum automorphism group for hypergraphs, which turns out to generalize the quantum automorphism group of Bichon for classical graphs. Further, we show that our quantum automorphism group acts on hypergraph C*-algebras as recently defined. In particular, this action generalizes the one on graph C*-algebras by Schmidt-Weber in 2018.

math.OA↗

arXiv2023

A Concrete Model for the Quantum Permutation Group on 4 Points

In 2019, Jung-Weber gave an example of a concrete magic unitary $M$, which defines a $C^*$-algebraic model of the quantum permutation group $S_4^+$. We show with the help of a computer that there exist no polynomials up to degree $50$ separating the entries of $M$ from the generators of $C(S_4^+)$. This indicates that the magic unitary $M$ might already define a faithful model of $S_4^+$.

math.QA↗