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Francesca Dalla Volta

Publications and source records attributed to Francesca Dalla Volta.

11 recordsLinked to original sources
arXiv2023

On the cardinality of irredundant and minimal bases of finite permutation groups

Given a finite permutation group $G$ with domain $Ω$, we associate two subsets of natural numbers to $G$, namely $\mathcal{I}(G,Ω)$ and $\mathcal{M}(G,Ω)$, which are the sets of cardinalities of all the irredundant and minimal bases of $G$, respectively. We prove that $\mathcal{I}(G)$ is an interval of natural numbers, whereas $\mathcal{M}(G,Ω)$ may not necessarily form an interval. Moreover, for a given subset of natural numbers $X \subseteq \mathbb{N}$, we provide some conditions on $X$ that ensure the existence of both intransitive and transitive groups $G$ such that $\mathcal{I}(G,Ω) = X$ and $\mathcal{M}(G,Ω) = X$.

math.GR↗
arXiv2022

On the primitivity of the AES-128 key-schedule

The key-scheduling algorithm in the AES is the component responsible for selecting from the master key the sequence of round keys to be xor-ed to the partially encrypted state at each iteration. We consider here the group $Γ$ generated by the action of the AES-128 key-scheduling operation, and we prove that the smallest group containing $Γ$ and all the translations of the message space is primitive. As a consequence, we obtain that no proper and non-trivial subspace can be invariant under its action.

math.GR↗
arXiv2021

The $A$-Möbius function of a finite group

The Möbius function of the subgroup lettice of a finite group $G$ has been introduced by Hall and applied to investigate several different questions. We propose the following generalization. Let $A$ be a subgroup of the automorphism group $\rm{Aut}(G)$ of a finite group $G$ and denote by $\mathcal C_A(G)$ the set of $A$-conjugacy classes of subgroups of $G.$ For $H\leq G$ let $[H]_A~=~\{~H^a ~\mid ~a\in ~A\}$ be the element of $\mathcal C_A(G)$ containing $H.$ We may define an ordering in $\mathcal C_A(G)$ in the following way: $[H]_A\leq [K]_A$ if $H^a\leq K$ for some $a\in A$. We consider the Möbius function $μ_A$ of the corresponding poset and analyse its properties and possible applications.

math.GR↗
arXiv2020

On two Möbius function for a finite non-solvable group

Let $G$ be a finite group, $μ$ be the Möbius function on the subgroup lattice of $G$, and $λ$ be the Möbius function on the poset of conjugacy classes of subgroups of $G$. It was proved by Pahlings that, whenever $G$ is solvable, the property $μ(H,G)=[N_{G^\prime}(H):G^{\prime}\cap H]\cdotλ(H,G)$ holds for any subgroup $H$ of $G$. It is known that this property does not hold in general; for instance it does not hold for every simple groups, the Mathieu group $M_{12}$ being a counterexample. In this paper we investigate the relation between $μ$ and $λ$ for some classes of non-solvable groups; among them, the minimal non-solvable groups. We also provide several examples of groups not satisfying the property.

math.GR↗
arXiv2019

The Möbius function of ${\rm PSL}(3,2^p)$ for any prime $p$

Let $G$ be the simple group ${\rm PSL}(3,2^p)$, where $p$ is a prime number. For any subgroup $H$ of $G$, we compute the Möbius function of $H$ in the subgroup lattice of $G$. To this aim, we describe the intersections of maximal subgroups of $G$. We point out some connections of the Möbius function with other combinatorial objects, and, in this context, we compute the reduced Euler characteristic of the order complex of the subposet of $r$-subgroups of ${\rm PGL}(3,q)$, for any prime $r$ and any prime power $q$.

math.GR↗
arXiv2018

On the classification problem for the genera of quotients of the Hermitian curve

In this paper we characterize the genera of those quotient curves $\mathcal{H}_q/G$ of the $\mathbb{F}_{q^2}$-maximal Hermitian curve $\mathcal{H}_q$ for which $G$ is contained in the maximal subgroup $\mathcal{M}_1$ of ${\rm Aut}(\mathcal{H}_q)$ fixing a self-polar triangle, or $q$ is even and $G$ is contained in the maximal subgroup $\mathcal{M}_2$ of ${\rm Aut}(\mathcal{H}_q)$ fixing a pole-polar pair $(P,\ell)$ with respect to the unitary polarity associated to $\mathcal{H}_q(\mathbb{F}_{q^2})$. In this way several new values for the genus of a maximal curve over a finite field are obtained. Together with what is known in the literature, our results leave just two open cases to provide the complete list of genera of Galois subcovers of the Hermitian curve; namely, the open cases in [Bassa-Ma-Xing-Yeo, J. Combin. Theory Ser. A, 2013] when $G$ fixes a point $P \in \mathcal{H}_q(\mathbb{F}_{q^2})$ and $q$ is even, and the open cases in [Montanucci-Zini, Comm. Algebra, 2018] when $G\leq\mathcal{M}_2$ and $q$ is odd.

math.AG↗
arXiv2013

The automorphism group of a self-dual [72,36,16] code does not contain S_3, A_4, or D_8

A computer calculation with Magma shows that there is no extremal self-dual binary code C of length 72, whose automorphism group contains the symmetric group of degree 3, the alternating group of degree 4 or the dihedral group of order 8. Combining this with the known results in the literature one obtains that Aut(C) has order at most 5 or isomorphic to the elementary abelian group of order 8.

cs.IT↗
arXiv2007

On solvable minimally transitive permutation groups

We investigate properties of finite transitive permutation groups $(G, Ω)$ in which all proper subgroups of $G$ act intransitively on $Ω.$ In particular, we are interested in reduction theorems for minimally transitive representations of solvable groups.

math.GR↗
arXiv2006

Abelian regular subgroups of the affine group and radical rings

We establish a link between abelian regular subgroup of the affine group, and commutative, associative algebra structures on the underlying vector space that are (Jacobson) radical rings. As an application, we show that if the underlying field has positive characteristic, then an abelian regular subgroup has finite exponent if the vector space is finite-dimensional, while it can be torsion free if the dimension is infinite. We also give an example of an abelian, regular subgroup of the affine group over an infinite vector space, which intersects trivially the group of translations.

math.GR↗