arXiv subjects

Diego Santoro

Publications and source records attributed to Diego Santoro.

8 recordsLinked to original sources

arXiv2026

On L-space surgeries on two-bridge links

We classify the sets of $L$-space surgeries on all two-bridge links, providing the first examples of hyperbolic links for which such sets cannot be described as unions of finitely many rectangles in $\mathbb{Q}^2$. The proof relies on several different techniques, each of which is applicable in greater generality: we introduce a sufficient diagrammatic condition for links in $S^3$ to be persistently foliar, a property that implies that every non-trivial surgery on such links supports a coorientable taut foliation. We define a simplified model for the Heegaard Floer homology of rational surgeries on two-component $L$-space links, following the work of Manolescu-Ozsváth, Liu, and Zemke, and use it to obtain obstructions to $L$-space surgeries. Finally, we use explicit computations of Turaev torsions to determine $L$-space surgeries in the case of generalised $L$-space links. Among the consequences of our results, we obtain an optimal uniform bound on the volume of any hyperbolic $L$-space that is surgery on a two-bridge link, together with a classification of all $L$-space satellite knots whose associated two-component pattern link is a two-bridge link.

math.GT↗

arXiv2026

Taut foliations from knot diagrams

We prove that knots in $S^3$ satisfying certain diagrammatic properties are persistently foliar. As a consequence, all their non-trivial surgeries support coorientable taut foliations. All non-fibered two-bridge knots, as well as many pretzel and Montesinos knots, satisfy these diagrammatic properties. More generally, our result applies to arborescent knots defined by weighted planar trees with more than one vertex, provided that all weights have absolute value greater than one and at least one weight has absolute value greater than two. We also use this result to provide sufficient conditions for closures of 3-braids, and more generally odd-strand braids, to be persistently foliar. The ideas involved in the proof extend to links: as an application, we show that for all surgeries $M$ on the Borromean rings one has that $M$ is not an $L$-space if and only if it supports a coorientable taut foliation.

math.GT↗

arXiv2026

L-spaces, taut foliations and the Whitehead link

We prove that if $M$ is a rational homology sphere that is a Dehn surgery on the Whitehead link, then $M$ is not an $L$-space if and only if $M$ supports a coorientable taut foliation. The left orderability of some of these manifolds is also proved, by determining which of the constructed taut foliations have vanishing Euler class. We also present some more general results about the structure of the $L$-space surgery slopes for links whose components are unknotted and with pairwise linking number zero, and about the existence of taut foliations on the fillings of a $k$-holed torus bundle over the circle with some prescribed monodromy. Our results, combined with some results from Roberts--Shareshian--Stein, also imply that all the rational homology spheres that arise as integer surgeries on the Whitehead link satisfy the L-space conjecture.

math.GT↗

arXiv2026

L-spaces, taut foliations and fibered hyperbolic two-bridge links

We prove that if $M$ is a rational homology sphere that is Dehn surgery on a fibered hyperbolic two-bridge link, then $M$ is not an $L$-space if and only if $M$ supports a coorientable taut foliation. As a corollary we show that if $K'$ is obtained by a non-trivial knot $K$ as result of an operation called two-bridge replacement, then all non-meridional surgeries on $K'$ support coorientable taut foliations. This operation generalises Whitehead doubling and as a particular case we deduce that all non-meridional surgeries on Whitehead doubles of a non-trivial knot support coorientable taut foliations.

math.GT↗

arXiv2025

On the detection of knotted spheres by their traces in high dimensions

For every $n \geq 4$, we demonstrate the existence of non-isotopic smooth $(n-2)$-knots in $S^n$ with diffeomorphic traces by generalising the RBG link construction to all dimensions. Conversely, we prove that for every $n \geq 4$, the unknot in $S^n$ is detected by the diffeomorphism type of its surgery and hence by its trace.

math.GT↗

arXiv2023

Dodecahedral L-spaces and hyperbolic 4-manifolds

We prove that exactly 6 out of the 29 rational homology 3-spheres tessellated by four or less right-angled hyperbolic dodecahedra are L-spaces. The algorithm used is based on the L-space census provided by Dunfield in arXiv:1904.04628, and relies on a result by Rasmussen-Rasmussen arXiv:1508.05900. We use the existence of these manifolds together with a result of Martelli arXiv:1510.06325 to construct explicit examples of hyperbolic 4-manifolds containing separating L-spaces, and therefore having vanishing Seiberg-Witten invariants. This answers a question asked by Agol and Lin in arXiv:1812.06536.

math.GT↗

arXiv2022

ONBRA: Rigorous Estimation of the Temporal Betweenness Centrality in Temporal Networks

In network analysis, the betweenness centrality of a node informally captures the fraction of shortest paths visiting that node. The computation of the betweenness centrality measure is a fundamental task in the analysis of modern networks, enabling the identification of the most central nodes in such networks. Additionally to being massive, modern networks also contain information about the time at which their events occur. Such networks are often called temporal networks. The temporal information makes the study of the betweenness centrality in temporal networks (i.e., temporal betweenness centrality) much more challenging than in static networks (i.e., networks without temporal information). Moreover, the exact computation of the temporal betweenness centrality is often impractical on even moderately-sized networks, given its extremely high computational cost. A natural approach to reduce such computational cost is to obtain high-quality estimates of the exact values of the temporal betweenness centrality. In this work we present ONBRA, the first sampling-based approximation algorithm for estimating the temporal betweenness centrality values of the nodes in a temporal network, providing rigorous probabilistic guarantees on the quality of its output. ONBRA is able to compute the estimates of the temporal betweenness centrality values under two different optimality criteria for the shortest paths of the temporal network. In addition, ONBRA outputs high-quality estimates with sharp theoretical guarantees leveraging on the \emph{empirical Bernstein bound}, an advanced concentration inequality. Finally, our experimental evaluation shows that ONBRA significantly reduces the computational resources required by the exact computation of the temporal betweenness centrality on several real world networks, while reporting high-quality estimates with rigorous guarantees.

cs.SI↗

arXiv2021

SPRISS: Approximating Frequent $k$-mers by Sampling Reads, and Applications

The extraction of $k$-mers is a fundamental component in many complex analyses of large next-generation sequencing datasets, including reads classification in genomics and the characterization of RNA-seq datasets. The extraction of all $k$-mers and their frequencies is extremely demanding in terms of running time and memory, owing to the size of the data and to the exponential number of $k$-mers to be considered. However, in several applications, only frequent $k$-mers, which are $k$-mers appearing in a relatively high proportion of the data, are required by the analysis. In this work we present SPRISS, a new efficient algorithm to approximate frequent $k$-mers and their frequencies in next-generation sequencing data. SPRISS employs a simple yet powerful reads sampling scheme, which allows to extract a representative subset of the dataset that can be used, in combination with any $k$-mer counting algorithm, to perform downstream analyses in a fraction of the time required by the analysis of the whole data, while obtaining comparable answers. Our extensive experimental evaluation demonstrates the efficiency and accuracy of SPRISS in approximating frequent $k$-mers, and shows that it can be used in various scenarios, such as the comparison of metagenomic datasets and the identification of discriminative $k$-mers, to extract insights in a fraction of the time required by the analysis of the whole dataset.

q-bio.QM↗