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On the closest stable/unstable nonnegative matrix and related stability radii
SIAM Journal on Matrix Analysis and Applications. 2018. Vol. 39. No. 4. P. 1642–1669.
Guglielmi N., Protasov V.
We consider the problem of computing the closest stable/unstable nonnegative matrix
to a given real matrix. The distance between matrices is measured in the Frobenius norm. The
problem is addressed for two types of stability: the Schur stability (the matrix is stable if its spectral
radius is smaller than one) and the Hurwitz stability (the matrix is stable if its spectral abscissa is
negative). We show that the closest unstable matrix can always be explicitly found. The problem
of computing the closest stable matrix to a nonnegative matrix is a hard problem even if the stable
matrix is not constrained to be nonnegative. Adding the nonnegativity constraint makes the problem
even more dicult. For the closest stable matrix, we present an iterative algorithm which converges
to a local minimum with a linear rate. It is shown that the total number of local minima can be
exponential in the dimension. Numerical results and the complexity estimates are presented.
Ponomarenko A., / Series Computer Science "arxiv.org". 2025.
This paper addresses the challenge of merging hierarchical navigable small world (HNSW) graphs, a critical operation for distributed systems, incremental indexing, and database compaction. We propose three algorithms for this task: Naive Graph Merge (NGM), Intra Graph Traversal Merge (IGTM), and Cross Graph Traversal Merge (CGTM). These algorithms differ in their approach to vertex selection ...
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Loubenets E. R., / Series arxiv.org "quant-ph". 2026. No. 2607.18050.
In many quantum applications it is important to know whether or not a Bell nonlocal two-qudit state exhibits its nonlocality under correlation scenarios with some given numbers S1,S2≥1 of generalized quantum measurements at two sites. In the present article, we find analytically a new general locality condition sufficient for a nonseparable Werner state with a ...
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Bolbachan V., / Series math "arxiv.org". 2024.
Chow polylogarithms are some special functions arising in explicit description of the Beilinson regulator map. The most interesting functional equation for this function reflects its vanishing on the boundary in the Bloch's cycle complex. We show that this functional equation formally follows from more simple ones, namely skew-symmetry, functoriality and multiplicativity.
To prove this, we study ...
Added: July 16, 2026
Bolbachan V., / Series math "arxiv.org". 2024.
Let K be a field of characteristic zero. We prove that its motivic cohomology in degree m−1 and weight m is rationally isomorphic to the cohomology of the polylogarithmic complex. This gives a partial extension of A. Suslin theorem describing the indecomposable K3 of a field. ...
Added: July 16, 2026
Panov V., Ryabchenko A., / Series arXiv "stat.ME". 2026. No. 2607.05048.
This paper investigates the problem of statistical inference for a mixture distribution consisting of a discrete and a continuous component, with a particular focus on the class of rational-infinitely divisible distributions. We consider non-parametric estimation of both components of the mixture as well as the quasi-L{é}vy measure, assuming that the mixture belongs to the class ...
Added: July 9, 2026
Piontkovski D., / Series arXiv "math". 2026.
A noncommutative projective variety is defined, following Artin and Zhang, by a graded coherent algebra 𝐴. The category of coherent sheaves is then the quotient qgr(𝐴) of the category of finitely presented graded modules by the subcategory of torsion modules. We consider the categorical and polynomial entropies of the Serre twist, that is, of the ...
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Piontkovski D., / Series arXiv "math". 2025.
If a symmetric multilinear algebra is weakly nil, then it is Engel. This result may be regarded as an infinite-dimensional analogue of the well-known Jacobian theorem, which states that if a polynomial mapping has a polynomial inverse, then its Jacobian matrix is invertible. This refines a theorem of Gerstenhaber and partially answers a question posed ...
Added: June 23, 2026
Konakov V., Kucher D., Mammen E., / Series arXiv "math". 2026. No. 2606.11142v1.
In this paper, we construct strong approximations for discrete-time Markov chains weakly converging to continuous diffusion processes, as well as for their perturbed counterparts. Under the assumption of bounded coefficients, we construct closely coupled versions of these processes on a shared probability space. In particular, for both non-degenerate and degenerate cases, we maximize the probability ...
Added: June 11, 2026
Chertopolokhov V., Mukhamedov A., Bugriy G. et al., IEEE Access 2026 Vol. 14 P. 14369–14392
This study presents on-the-fly identification and multi-step prediction of nonlinear systems with delayed inputs using a dynamic neural network combined with a smooth projection onto ellipsoids. The projection enforces parameter constraints that guarantee stability, while a Lyapunov–Krasovskii analysis yields computable ultimate error bounds. Riccati-type matrix inequalities are derived, providing an efficient vectorization–projection–devectorization implementation suitable for ...
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Shipilov F., Barnyakov A., Ivanov A. et al., / Series Physics "arxiv.org". 2026.
A fast simulation of the detector response is a vital task in high-energy physics (HEP). Traditional Monte-Carlo methods form the backbone of modern particle physics simulation software but are computationally expensive. We present a machine-learning-based approach to fast simulation of the Focusing Aerogel Ring Imaging Cherenkov (FARICH) detector response. Given a particle track and momentum, ...
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Гущина В. А., / Series chemrxiv-2023-vpzhz-v2 "ChemRxiv". 2023.
All-inorganic perovskite CsPbBr3 and Cs4PbBr6 nanoparticles are being intensively studied due to their unique properties and wide range of applications; however, however, the nature of their optical properties is not yet fully understood due to the difficulty of synthesis of singlephase nanoparticles. In this article we describe the features of the synthesis of single-phase particles ...
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Dorovskiy A., / Series arXiv "math". 2026.
In this paper the structural stability of generic families of vector fields of the PC-HC class on the two-dimensional sphere is proved. A classification of these families up to moderate equivalence in neighborhoods of their large bifurcation supports is presented, based on such invariants as the configuration and the characteristic set. The realization lemma is proved. ...
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Taletskii D., / Series arXiv "math". 2026.
A vertex subset of a graph is called a \textit{distance-$k$ independent set} if the distance between any two of its distinct vertices is at least $k + 1$. For all $n,k \geq 1$, we determine the minimum possible number of inclusion-wise maximal distance-$k$ independent sets among all $n$-vertex trees. It equals~$n$ if $n \leq k ...
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Ovcharenko M., / Series arXiv "math". 2026.
We introduce an explicit class of tempered Laurent polynomials in the sense of Villegas and Doran--Kerr in n⩽4 variables including all Landau--Ginzburg models for smooth Fano threefolds with very ample anticanonical class. We check that it contains Landau--Ginzburg models for various Fano fourfolds which are complete intersections in smooth toric varieties and Grassmannians of planes, ...
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Derkacheva A., Sakirkina M., Kraev G. et al., /. 2026.
Comprehensive data on natural hazards and their consequences are crucial for effective for risk assessment, adaptation planning, and emergency response. However, many countries face challenges with fragmented, inconsistent, and inaccessible data, particularly regarding local-scale events. To address this data gap in Russia, we developed an end-to-end processing pipeline that scrapes news from various online sources, ...
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Shishkina E., Revista Internacional de Metodos Numericos para Calculo y Diseno en Ingenieria 2025
This article investigates the problem of approximating the generalized
Erdélyi-Kober fractional operator (often referred to as the Lowndes operator)
using cubic splines. A method based on cubic spline interpolation
is proposed for approximating the operator on a non-uniform grid. The
convergence rate of the proposed method is proven, and its stability is
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A. S. Baybar, M. Yu. Puzachenko, R. B. Sandlersky, Geography and Natural Resources 2025 Vol. 46 No. S1 P. S15–S22
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S M., Seralan V., R V. et al., Journal of Applied Nonlinear Dynamics 2025 Vol. 14 No. 3 P. 719–743
In this work, we propose a ratio-dependent intraguild predation model that incorporates fear and gestation delay. Further, the cost of the intraguild predator's fear is thought to decrease the size of the intraguild prey. The interaction between prey and predator takes place in the form ratio-dependence type. This type of functional response offers a valuable ...
Added: October 15, 2025
Seralan V., D C., Sarasu P. et al., Cognitive Neurodynamics 2024 Vol. 18 P. 4071–4087
This study delves into the examination of a network of adaptive synapse neurons characterized by a small-world network topology connected through electromagnetic flux and infused with randomness. First, this research extensively explores the existence of the global multi-stability of a single adaptive synapse-based neuron model with magnetic flux. The non-autonomous neuron model exhibits periodically switchable ...
Added: October 15, 2025
Seralan V., R V., Nien T. H. et al., Mathematics 2023 Vol. 11 No. 14 Article 3118
Fear and prey refuges are two significant topics in the ecological community because they are closely associated with the connectivity of natural resources. The effect of fear on prey populations and prey refuges (proportional to both the prey and predator) is investigated in the nonlinear-type predator-harvested Leslie–Gower model. This type of prey refuge is much ...
Added: October 15, 2025
S M., Seralan V., K S. et al., International Journal of Biomathematics 2022 Vol. 15 No. 04 Article 2250014
This paper deals with the investigation of the three species food-web model. This model includes two logistically growing interaction species, namely x and y, and the third species z behaves as the predator and also host for x. The species z predating on the species y with the Holling type-II functional response, while the first species x is benefited from the third species z. Further, the effect of ...
Added: October 15, 2025
Seralan V., R S., K S. et al., Complexity 2022 Vol. 3022 Article 6931354
*e discrete-time system has more complex and chaotic dynamical behaviors as compared to the continuous-time system. *ispaper extends a discrete Leslie–Gower predator-prey system with the Allee effect in the predator’s population, whose dynamics areanalyzed and explored. We have determined the equilibrium points and studied their local stability properties. We find that thesystem undergoes flip bifurcation ...
Added: October 15, 2025
Seralan V., R S., K S. et al., Advances in Continuous and Discrete Models 2021 Vol. 2021 Article 338
In this article, we discuss the dynamics of a Leslie–Gower ratio-dependent predator–prey model incorporating fear in the prey population. Moreover, the Allee effect in the predator growth is added into account from both biological and mathematical points of view. We explore the influence of the Allee and fear effect on the existence of all positive ...
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Seralan V., R S., K S. et al., Advances in Continuous and Discrete Models 2021 Vol. 2021 Article 54
Dynamical analysis of a delayed tri-trophic food chain consisting of prey, an intermediate, and a top predator is investigated in this paper. The additive Allee effect is introduced in the prey population, and it is assumed that there is a time lag due to the gestation effect in the intermediate predator. The interference among the ...
Added: October 15, 2025