Opin vísindi

 

Nýlega bætt við

Verk
Connectedness matters : construction and exact random sampling of connected networks
(2021-03) Horvát, Sz; Modes, Carl D.; Department of Computer Science
We describe a new method for the random sampling of connected networks with a specified degree sequence. We consider both the case of simple graphs and that of loopless multigraphs. The constraints of fixed degrees and of connectedness are two of the most commonly needed ones when constructing null models for the practical analysis of physical or biological networks. Yet handling these constraints, let alone combining them, is non-trivial. Our method builds on a recently introduced novel sampling approach that constructs graphs with given degrees independently (unlike edge-switching Markov chain Monte Carlo methods) and efficiently (unlike the configuration model), and extends it to incorporate the constraint of connectedness. Additionally, we present a simple and elegant algorithm for directly constructing a single connected realization of a degree sequence, either as a simple graph or a multigraph. Finally, we demonstrate our sampling method on a realistic scale-free example, as well as on degree sequences of connected real-world networks, and show that enforcing connectedness can significantly alter the properties of sampled networks.
Verk
Tight Localizations of Feedback Sets
(2021) Hecht, Michael; Gonciarz, Krzysztof; Horvát, Szabolcs; Department of Computer Science
The classical NP-hard feedback arc set problem (FASP) and feedback vertex set problem (FVSP) ask for a minimum set of arcs ϵ ⊆ E or vertices ν ⊆ V whose removal G ∖ ϵ, G ∖ ν makes a given multi-digraph G=(V, E) acyclic, respectively. Though both problems are known to be APX-hard, constant ratio approximations or proofs of inapproximability are unknown. We propose a new universal O(|V||E|4)-heuristic for the directed FASP. While a ratio of r ≈ 1.3606 is known to be a lower bound for the APX-hardness, at least by empirical validation we achieve an approximation of r ≤ 2. Most of the relevant applications, such as circuit testing, ask for solving the FASP on large sparse graphs, which can be done efficiently within tight error bounds with our approach.
Verk
Impossible ecologies : Interaction networks and stability of coexistence in ecological communities
(2025-07-16) Meng, Yu; Horvát, Szabolcs; Modes, Carl D.; Haas, Pierre A.; Department of Computer Science
Does an ecological community allow stable species coexistence? Identifying the general effects of competitive, mutualistic, and predator-prey interactions on stability remains a central problem of systems ecology because established approaches cannot account for the full network arrangement of these interactions. Here, we therefore analyze all interaction networks of N≤5 species with Lotka-Volterra dynamics by combining exact results and numerical exploration. We find that a very small subset of these networks is “impossible ecologies,” in which stable coexistence is non-trivially impossible. We prove that the possibility of stable coexistence is determined by similarly rare “irreducible ecologies.” Statistical sampling shows that this probability varies over orders of magnitude even in ecologies that differ only in the network arrangement of identical interactions. Thus, our approach reveals that the full network structure of interactions can influence stability of coexistence more than the established effect of interaction-type proportions. A record of this paper's transparent peer review process is included in the supplemental information.
Verk
Patient Generated Data And Affordances: Conversation Cues In Clinical Decision Making
(2018) Grisot, Miria; Lindroth, Thomas; Islind, Anna Sigridur; Department of Computer Science
Verk
Balancing the social media seesaw in public sector: a sociomaterial perspective
(2017) Norström, Livia; Islind, Anna Sigridur; Vallo Hult, Helena; Department of Computer Science

Flokkar í Opnum vísindum

Veldu flokk til að skoða.

Niðurstöður 1 - 9 af 9