Université de Fribourg

Maximum eccentric connectivity index for graphs with given diameter

Hauweele, Pierre ; Hertz, Alain ; Mélot, Hadrien ; Ries, Bernard ; Devillez, Gauvain

In: Discrete Applied Mathematics, 2019, vol. 268, p. 102-111

The eccentricity of a vertex v in a graph G is the maximum distance between v and any other vertex of G. The diameter of a graph G is the maximum eccentricity of a vertex in G. The eccentric connectivity index of a connected graph is the sum over all vertices of the product between eccentricity and degree. Given two integers n and D with D ≤ n−1, we characterize those graphs which have...

Consortium of Swiss Academic Libraries

The monomorphism problem in free groups

Ciobanu, Laura ; Houcine, Abderezak

In: Archiv der Mathematik, 2010, vol. 94, no. 5, p. 423-434

Consortium of Swiss Academic Libraries

Local Currents in Metric Spaces

Lang, Urs

In: Journal of Geometric Analysis, 2011, vol. 21, no. 3, p. 683-742

Consortium of Swiss Academic Libraries

On Lyndon's equation in some Λ-free groups and HNN extensions

Ciobanu, L. ; Fine, B. ; Rosenberger, G.

In: Journal of Group Theory, 2011, vol. 14, no. 3, p. 333-339

Université de Fribourg

A robust ranking algorithm to spamming

Zhou, Yan-Bo ; Lei, Ting ; Zhou, Tao

In: EPL - Europhysics Letters, 2011, vol. 94, no. 4, p. 48002

Ranking problem of web-based rating systems has attracted much attention. A good ranking algorithm should be robust against spammer attack. Here we proposed a correlation-based reputation algorithm to solve the ranking problem of such rating systems where user votes some objects with ratings. In this algorithm, the reputation of a user is iteratively determined by the correlation coefficient...

Université de Fribourg

The monomorphism problem in free groups

Ciobanu, Laura ; Houcine, Abderezak Ould

In: Archiv der Mathematik, 2010, vol. 94, no. 5, p. 423-434

Let F be a free group of finite rank. We say that the monomorphism problem in F is decidable if there is an algorithm such that, for any two elements u and v in F, it determines whether there exists a monomorphism of F that sends u to v. In this paper we show that the monomorphism problem is decidable and we provide an effective...