Publikace

Článek

10.1016/j.physletb.2025.139563

We report on the first ab initio informed α knock-out reaction in the intermediate-mass region, with the aim to probe the underlying chiral potential and its impact on the emergence of alpha clustering in this mass region. The theoretical predictions of the α+16O clustering in the 20Ne ground state, based on the ab initio symmetry-adapted no-core shell model with continuum, yield a triple differential cross section for 20Ne(p, pα)16O that is in a remarkable agreement with the data. This allows us to examine predictions of surface and in-medium α-cluster features that emerge from the underlying realistic nucleon-nucleon interaction with no parameters fitted to nuclear data beyond the two-body system, and to compare these to the successful antisymmetrized molecular dynamics approach.

Stať ve sborníku

10.1609/aaai.v39i28.35368

We propose a 2D simulation system for multi-agent collective construction (MACC) based on simple line-following intelligent machines (SLIM) - small differential drive mobile robots. Our MACC-SLIM system alleviates the high upfront cost of implementing MACC on real hardware. Our system builds upon widely available resources, namely a standard LCD screen and commodity mobile robots, allowing researchers and schools easier access to MACC hardware implementation. We test the system on plans generated by an optimal state-of-the-art MACC algorithm, demonstrating there are still non-insignificant synchronization delays. The MACC-SLIM system allows us to observe bottlenecks, parallelism, and possible execution failures of plans generated by the MACC algorithms.

Článek

10.1007/s11139-024-01005-2

We consider Shanks’ simplest cubic fields K for which the index [O_K : Z[rho]] of a root rho of the defining parametric polynomial is 3. For them, we study the additive indecomposables of K and provide a complete list of them. Moreover, we use the knowledge of the indecomposables to prove some interesting consequences on the arithmetic of K. Mainly, we obtain good bounds on the ranks of universal quadratic forms over K and prove that the Pythagoras number of O_K is 6.

Článek

10.37236/13326

Dendric shift spaces simultaneously generalize co dings of regular interval exchanges and episturmian shift spaces, themselves both generalizations of Sturmian words. One of the key properties enforced by dendricity is the Return Theorem. In this paper, we prove its converse, providing the following natural algebraic perspective on dendricity: A minimal shift space is dendric if and only if every set of return words is a basis of the free group over the alphabet.

Stať ve sborníku

10.1007/978-981-96-0576-7_2

Organisations today heavily rely on complex software systems integrated through multiple layers of middleware. This complexity leads to substantial generation of operational data of structured and semi-structured formats which is recorded in log files. The workload of the system fluctuates according to specific periods of the day which impacts the amount and quality of data generated in log files. In this paper, we propose a new log anomaly detection approach that leverages a collection of smaller models designed to capture workload fluctuations over specific time intervals. We demonstrate its effectiveness in detecting anomalies within log streams. Our evaluation uses log data from servers in a production environment, handling a complex back-end system that processes hundreds of requests per second. We show that our method outperforms traditional and widely used anomaly detection methods in data streams in the context of dynamic and time-sensitive workload scenarios.

Článek

10.1016/j.jnt.2024.12.001

We study a new connection between multidimensional continued fractions, such as Jacobi-Perron algorithm, and additively indecomposable integers in totally real cubic number fields. First, we find the indecomposables of all signatures in Ennola's family of cubic fields, and use them to determine the Pythagoras numbers. Second, we compute a number of periodic JPA expansions, also in Shanks' family of simplest cubic fields. Finally, we compare these expansions with indecomposables to formulate our conclusions.

Stať ve sborníku

10.1609/aaai.v39i13.33503

In the recently introduced model of fair partitioning of friends, there is a set of agents located on the vertices of an underlying graph that indicates the friendships between the agents. The task is to partition the graph into k balanced-sized groups, keeping in mind that the value of an agent for a group is equal to the number of edges they have in that group. The goal is to construct partitions that are "fair", i.e., no agent would like to replace an agent in a different group. We generalize the standard model by considering utilities for the agents that are beyond binary and additive. Having this as our foundation, our contribution is threefold: (a) we adapt several fairness notions that have been developed in the fair division literature to our setting; (b) we give several existence guarantees supported by polynomial-time algorithms; (c) we initiate the study of the computational (and parameterized) complexity of the model and provide an almost complete landscape of the (in)tractability frontier for our fairness concepts.

Článek

10.1038/s41597-025-04603-x

Anomaly detection in network traffic is crucial for maintaining the security of computer networks and identifying malicious activities. Most approaches to anomaly detection use methods based on forecasting. Extensive real-world network datasets for forecasting and anomaly detection techniques are missing, potentially causing overestimation of anomaly detection algorithm performance and fabricating the illusion of progress. This manuscript tackles this issue by introducing a comprehensive dataset derived from 40 weeks of traffic transmitted by 275,000 active IP addresses in the CESNET3 network—an ISP network serving approximately half a million customers daily. It captures the behavior of diverse network entities, reflecting the variability typical of an ISP environment. This variability provides a realistic and challenging environment for developing forecasting and anomaly detection models, enabling evaluations that are closer to real-world deployment scenarios. It provides valuable insights into the practical deployment of forecast-based anomaly detection approaches.

Článek

10.1016/j.cola.2024.101300

This paper explores how to reconstruct UML diagrams from dynamically typed languages such as Smalltalk, which do not use explicit type information. This lack of information makes traditional methods for extracting associations difficult. It addresses the need for automated techniques, particularly in legacy software systems, to facilitate their transformation into modern technologies, focusing on Smalltalk as a case study due to its extensive industrial legacy and modern adaptations like Pharo. We propose a way to create UML diagrams from Smalltalk code, focusing on using type inference to determine UML associations. For optimal outcomes for large-scale software systems, we recommend combining different type inference methods in an automatic or semi-automatic way.

Článek

10.1109/TNNLS.2024.3383246

In areas of machine learning such as cognitive modeling or recommendation, user feedback is usually context-dependent. For instance, a website might provide a user with a set of recommendations and observe which (if any) of the links were clicked by the user. Similarly, there is growing interest in the so-called “odd-one-out” learning setting, where human participants are provided with a basket of items and asked which is the most dissimilar to the others. In both of those cases, the presence of all the items in the basket can influence the final decision. In this article, we consider a classification task where each input consists of three items (a triplet), and the task is to predict which of the three will be selected. Our aim is not only to return accurate predictions for the selection task, but also to additionally provide interpretable feature representations for both the context and for each individual item. To achieve this, we introduce CARE, a specialized neural network architecture that yields Context-Aware REpresentations of items based on observations of triplets of items alone. We demonstrate that, in addition to achieving state-of-the-art performance at the selection task, our model can produce meaningful representations both for each item, as well for each context (triplet of items). This is done using only triplet responses: CARE has no access to supervised item-level information. In addition, we prove parameter counting generalization bounds for our model in the i.i.d. setting, demonstrating that the apparent sample sparsity arising from the combinatorially large number of possible triplets is no obstacle to efficient learning.

Stať ve sborníku

Assessing the structural similarity of different implementations of logic functions is of importance in many areas of digital design, such as iterative resynthesis, engineering change order (ECO) based design, design of reliable redundant systems (duplex, TMR), etc. In general, numerous metrics exist that describe such similarity, mostly based on its intended application. In this paper, we introduce a novel metric based on a calculation of the functional equivalence of subcircuits. As this approach requires repeated calls of time-consuming functional equivalence checking, we propose a linear-time approximation of this method based on signal controllability calculation. These two approaches are compared to the state-of-the-art fault detection-based design diversity estimation technique and applied to assess the fault-security capabilities of duplex systems.

Článek

10.1002/jgt.23187

We study a counting version of Cycle Double Cover Conjecture. We discuss why it is more interesting to count circuits (i.e., graphs isomorphic to C_k for some k) instead of cycles (graphs with all degrees even). We give an almost-exponential lower bound for graphs with a surface embedding of representativity at least 4. We also prove an exponential lower bound for planar graphs. We conjecture that any bridgeless cubic graph has at least 2^(n/2 - 1) circuit double covers and we show an infinite class of graphs for which this bound is tight.

Stať ve sborníku

10.1007/978-3-031-85703-4_16

An efficient algorithm for enumerating representations of the unitary group U(3) that occur in a representation of the unitary group U(N) is introduced. The algorithm is applicable to U(N) representations associated with a system of nucleons distributed among the degenerate eigenstates of the selected three-dimensional harmonic oscillator level, where each eigenstate can be occupied by up to 4 particles with different combinations of spin and isospin quantum numbers. A C++ implementation of the proposed algorithm is provided, and its performance evaluation is reported.

Stať ve sborníku

Imagine we want to split a group of agents into teams in the most efficient way, considering that each agent has their own preferences about their teammates. This scenario is modeled by the extensively studied Coalition Formation problem. Here, we study a version of this problem where each team must additionally be of bounded size. We conduct a systematic algorithmic study, providing several intractability results as well as multiple exact algorithms that scale well as the input grows (FPT), which could prove useful in practice. Our main contribution is an algorithm that deals efficiently with tree-like structures (bounded treewidth) for "small" teams. We complement this result by proving that our algorithm is asymptotically optimal. Particularly, there can be no algorithm that vastly outperforms the one we present, under reasonable theoretical assumptions, even when considering star-like structures (bounded vertex cover number).

Článek

10.1090/proc/17141

We discuss the phenomenon where an element in a number field is not integrally represented by a given positive definite quadratic form, but becomes integrally represented by this form over a totally real extension of odd degree. We prove that this phenomenon happens infinitely often, and, conversely, establish finiteness results about the situation when the quadratic form is fixed.

Stať ve sborníku

10.1007/978-3-031-85703-4_23

A model for simulating pedestrian recreational movement along a tourist trail is introduced. The model reduces the two-dimensional nature of bidirectional flow to one dimension while preserving the inter-agent interaction and density-induced velocity reduction. This is achieved by applying kernel estimates of pedestrian density to describe the pedestrian mass in the perceived surroundings of an agent. The applicability of the model is investigated by means of numerical simulations using three speed distribution scenarios and three arrival rate scenarios. The simulation results are in correspondence with expectations and recommendations related to capacity for day-use facilities in national parks (pedestrian level of service D). The model mimics the expected trail capacity behaviour represented by arrival rate, leading to speed deterioration and stoppages. Heterogeneity of the agents similarly as non-homogeneity of arrival rate leads to clogging at smaller average arrival rates.

Článek

n/a

Článek

10.1016/j.eswa.2024.126187

The triplet-based odd-one-out problem, which involves trials where human subjects are asked to select the most different concept among three, is a well-studied task in cognitive sciences. With the release of a large triplet-based dataset, THINGS, there has been a recent surge in the popularity of machine learning models aimed at learning mathematical representations of object concepts, such as SPoSE, VICE, and CARE. The first two models learn representations by maximizing the similarity between the two most similar objects, while the latter diverges by directly learning the odd-one-out, making its embedding more distant. No prior attempts have integrated both paradigms, which are important for understanding object representation in cognitive science. In this paper, we propose MASTER, a multitask learning method for the triplet problem that encapsulates both paradigms. Our results demonstrate that our method not only better predicts the odd-one-out object but also provides insightful representations for studying these concepts. Furthermore, we studied the conditions under which each model performs better, offering valuable insights for future research on how these paradigms affect human understanding of object concepts.

Článek

10.1002/jgt.23200

A graph is called odd (respectively, even) if every vertex has odd (respectively, even) degree. Gallai proved that every graph can be partitioned into two even induced subgraphs, or into an odd and an even induced subgraph. We refer to a partition into odd subgraphs as an odd colouring of G $G$. Scott proved that a connected graph admits an odd colouring if and only if it has an even number of vertices. We say that a graph G $G$ is k $k$-odd colourable if it can be partitioned into at most k $k$ odd induced subgraphs. The odd chromatic number of G $G$, denoted by chi odd( G ) ${\chi }_{\text{odd}}(G)$, is the minimum integer k $k$ for which G $G$ is k $k$-odd colourable. We initiate the systematic study of odd colouring and odd chromatic number of graph classes. We first consider a question due to Scott, which states that every graph G $G$ of even order n $n$ has chi odd( G ) <= c n ${\chi }_{\text{odd}}(G)\le c\sqrt{n}$, for some positive constant c $c$, by proving that this is indeed the case if G $G$ is restricted to having girth at least seven. We also show that any graph G $G$ whose all components have even order satisfies chi odd( G ) <= 2 Delta - 1 ${\chi }_{\text{odd}}(G)\le 2{\rm{\Delta }}-1$, where Delta ${\rm{\Delta }}$ is the maximum degree of G $G$. Next, we show that certain interesting classes have bounded odd chromatic number. Our main results in this direction are that interval graphs, graphs of bounded modular-width all have bounded odd chromatic number. In particular, every even interval graph is 6-odd colourable, and every even graph is 3 m w $3mw$-odd colourable, where m w $mw$ is the modular width of a graph.

Článek

10.1090/proc/17019

The normed spaces of molecules constructed by Arens and Eells allow us to define two natural equivalence relations on the class of complete metric spaces. We say that two complete metric spaces M and N are M at- equivalent if their normed spaces of molecules are isomorphic and we say that they are .F- equivalent if the corresponding completions - the Lipschitz-free Banach spaces .F ( M ) and .F ( N ) - are isomorphic. In this note, we compare these and some other relevant equivalences of metric spaces. Clearly, M at-equivalent spaces are .F-equivalent. Our main result states that M at-equivalent spaces must have the same covering dimension. In combination with the work of Godard, this implies that M at-equivalence is indeed strictly stronger than .F-equivalence. However, M at-equivalent spaces need not be homeomorphic, as we demonstrate through a general construction. We also observe that M at-equivalence does not preserve the Assouad dimension. We introduce a natural notion of a free basis to simplify the notation.