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Proceedings of Journees 2019
Paris Observatory, 2020.
Bizouard C.
Journees 2019 have been marked by record numbers of participants and communications. Therewere 118 attendants coming from 21 countries over the 5 continents. The scientific programincluded 58 oral presentations and 38 posters. Presentations were split into five sessions, alternatingastrometry (sessions I and III), Earth rotation changes (Session II/IV) and solar system dynamics(session V). Of particular interest were the communications dedicated to the results of the Gaiamission and its possible future prolongation in IR band (Session I), the realization of the InternationalCelestial Frame III (session III). In session II, many interesting talks were devoted to the centennialof the ”Earth rotation” IAU commission
Chapters
Zotov L., Bizouard C., Сидоренков Н. С. et al., , in: Proceedings of Journees 2019.: Paris Observatory, 2020. P. 249–254.
The works that we carried out during the last ten years lead to significant progress inthe knowledge of the Chandler wobble (CW) of the Earth polar motion (PM). In Zotov and Bizouard(2012) we reconstructed the excitation of this resonant mode by using Panteleev’s correctivefiltering. Now we are sure, that this filtering is a regularizing algorithm ...
Added: November 30, 2020
Сидоренков Н. С., Dionis E., Bizouard C. et al., , in: Proceedings of Journees 2019.: Paris Observatory, 2020. P. 243–247.
The decadal instabilities in Earth’s rotation (DIER) are thought to be caused bythe interactions between the Earth’s core and its mantle. This hypothesissuccessfully explains whythere is a close correlation between DIER and the variations in the rate of the westward drift of thegeomagnetic eccentric dipole, since it is successfully reproduced by modeling of the redistribution ...
Added: November 30, 2020
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. ...
Added: May 14, 2026
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 ...
Added: May 1, 2026
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, ...
Added: April 30, 2026
Zlotnik Alexander, / Series arXiv "math". 2026. No. 2602.03481v1.
We deal with the global in time weak solutions to the 1D compressible Navier-Stokes system of equations for large discontinuous initial data and nonhomogeneous boundary conditions of three standard types. We prove the Lipschitz-type continuous dependence of the solution $(\eta,u,\theta)$, in a norm slightly stronger than $L^{2,\infty}(Q)\times L^2(Q)\times L^2(Q)$, on the initial data $(\eta^0,u^0,e^0)$ in a ...
Added: April 18, 2026
Medvedev V., / Series arXiv "math". 2026.
We investigate the interplay between the dimension of the space of static potentials and the geometric and topological structure of the underlying static three-manifold. A partial classification of boundaryless static manifolds is obtained in terms of this dimension. We also treat the case of static manifolds with boundary. In particular, we prove that if a ...
Added: April 3, 2026
Gabdullin N., Androsov I., / Series Computer Science "arxiv.org". 2026.
Label prediction in neural networks (NNs) has O(n) complexity proportional to the number of classes. This holds true for classification using fully connected layers and cosine similarity with some set of class prototypes. In this paper we show that if NN latent space (LS) geometry is known and possesses specific properties, label prediction complexity can ...
Added: April 2, 2026
Zotov L., Sidorenkov N., Bizouard C., , in: Proceedings of the 19th Annual Meeting ofthe Asia Oceania Geosciences Society.: Singapore: World Scientific Publishing Co. Pte. Ltd, 2023. P. 153–155.
In early 2000-s the amplitude of the Chandler wobble (CW) started to decrease and in 2017-2020 reached its historic minima, comparable only with the minima of ~1928 yr. In 2021 the CW appeared again. We demonstrate that the phase of the CW is changing now, as during 1920-1930s. Since 2010 it has changed almost by ...
Added: March 5, 2026
Zotov L., Sidorenkov N., Bizouard C., , in: Proceedings of the XV Conference and School (St. Petersburg, Russia, April 22–26). Problems of Geocosmos—2024.: Switzerland: Springer, 2026. P. 289–312.
Earth rotation in recent epoch shows anomalies: its rotation velocity reached decadal maximum in 2024; the Chandler wobble (CW) of the rotation axis disappeared in 2018–2020, then resumed with a phase changed by 180^\circ
◦; the ampli-tude of the Free Core Nutation (FCO) decreased since 2021 as well. We analyzed the CW amplitude modulations since the ...
Added: March 1, 2026
Kolesnikov A., / Series arXiv "math". 2025.
We study Blaschke--Santal{ó}-type inequalities for N>=2 sets (functions) and a special class of cost functions. In particular, we prove new results about reduction of the maximization problem for the Blaschke--Santal{ó}-type functional to homogeneous case (functional inequalities on the sphere) and extend the symmetrization argument to the case of N>2 sets.
We also discuss links to the ...
Added: February 13, 2026
Sorokin K., Beketov M., Онучин А. et al., / arxiv.org. Серия cs.SI "Social and Information Networks ". 2025.
Community detection in complex networks is a fundamental problem, open to new approaches in various scientific settings. We introduce a novel community detection method, based on Ricci flow on graphs. Our technique iteratively updates edge weights (their metric lengths) according to their (combinatorial) Foster version of Ricci curvature computed from effective resistance distance between the ...
Added: January 15, 2026
Gaianov N., Parusnikova A., / Cornell University. Серия math "arxiv.org". 2025.
An algebraic q-difference equation is considered. A sufficient condition for the existence of a formal power-logarithmic expansion of a solution to such an equation in the neighborhood of zero is proposed. An example of applying this sufficient condition for constructing a formal expansion of a solution to a certain q-difference analogue of the fifth Painlevé equation ...
Added: December 25, 2025
Popov V., / Series arXiv "math". 2025. No. 2502.01539.
We prove that the variety of flexes of algebraic curves
of degree 3 in the projective plane is an ideal theoretic complete
intersection in the product of a two-dimensional and a nine-dimensional projective spaces. ...
Added: December 16, 2025
Zotov L., Логинов А. В., Ольховский А. А. et al., В кн.: ВОПРОСЫ ТЕОРИИ И ПРАКТИКИ ГЕОЛОГИЧЕСКОЙ ИНТЕРПРЕТАЦИИ ГРАВИТАЦИОННЫХ, МАГНИТНЫХ И ЭЛЕКТРИЧЕСКИХ ПОЛЕЙ 51-я сессия Международного семинара им. Д.Г. Успенского - В.Н. Страхова. Москва, 2025.: Пермский государственный университет, 2025.
One of the major components of the Earth’s polar motion is Chandler wobble with 433-day period. To extract it from observations narrow-band filtering is required. We have developed method which joins Kalman filtering and band-pass filtering in direct time with the phase correction in reversed time. By using Euler-Liouville equation generating resonant CW as a ...
Added: December 10, 2025
Gnetov F., Konakov V., / Series arXiv "math". 2025. No. 2512.04667.
We establish a central limit theorem, a local limit theorem, and a law of large numbers for a natural
random walk on a symmetric space M of non-compact type and rank one. This class of spaces, which
includes the complex and quaternionic hyperbolic spaces and the Cayley hyperbolic plane, generalizes
the real hyperbolic space Hn. Our approach introduces ...
Added: December 5, 2025
Kazakov A., Koryakin V., Safonov K. et al., / Series arXiv "math". 2025.
The Lorenz attractor is the first example of a robustly chaotic non-hyperbolic attractor. Each orbit of such an attractor has a positive top Lyapunov exponent, and this property persists under small perturbations despite possible bifurcations of the attractor. In this paper, we study the boundary of the Lorenz attractor existence region in the Shimizu-Morioka model. ...
Added: December 4, 2025
Bitter I., Konakov V., / Cornell University. Серия arXiv "math". 2025. № 2505.24548.
В работе приводится обобщение локальной предельной теоремы о сходимости неоднородных цепей Маркова к диффузионному пределу на случай, когда соответ- ствующие коэффициенты процессов удовлетворяют слабым условиям регулярности и совпадают лишь асимптотически. В частности, рассматриваемые нами коэффици- енты сноса могут быть неограниченными с не более чем линейным ростом, а оценки отражают перенос терминального состояния неограниченным трендом через ...
Added: December 3, 2025
Bogomolov F. A., Schrandt S., / Series arXiv "math". 2025.
We discuss phenomena of stabilization for direct images of line bundles over projective curves mapping onto the projective line, for maps of sufficiently big degree. ...
Added: December 1, 2025
Deviatov R., Baek S., / Series arXiv "math". 2025.
The torsion index of split simple groups has been extensively studied, notably by Totaro, who calculated the torsion indexes of the spin groups and $E_{8}$ in [5] and [6], respectively. The aim of this paper is to provide upper bounds for the torsion index of half-spin groups, the only remaining case in the calculation of ...
Added: December 1, 2025
Hessian-based lightweight neural network for brain vessel segmentation on a minimal training dataset
Меньшиков И. А., Бернадотт А. К., Elvimov N. S., / Series arXie "Statistical mechanics". 2025.
Accurate segmentation of blood vessels in brain magnetic resonance angiography (MRA) is essential for successful surgical procedures, such as aneurysm repair or bypass surgery. Currently, annotation is primarily performed through manual segmentation or classical methods, such as the Frangi filter, which often lack sufficient accuracy. Neural networks have emerged as powerful tools for medical image ...
Added: December 1, 2025
Prokhorov Y., / Series arXiv "math". 2025.
A $\mathbf{Q}$-conic bundle is a contraction $f: X\to Z$ of a three-dimensional algebraic variety $X$ to a surface~$Z$ such that the variety~$X$ has only terminal $\mathbf{Q}$-factorial singularities, the anticanonical divisor $-K_X$ is~$f$-ample, and $\uprho(X/Z)=1$. We provide an algorithm to transform a $\mathbf{Q}$-conic bundle to its standard form. ...
Added: December 1, 2025
Amerik E., Verbitsky M., Soldatenkov A., / Series arXiv "math". 2025.
Wierzba and Wisniewski proved that in dimension 4, every bimeromorphic map of hyperkahler manifolds is represented as a composition of Mukai flops. Hu and Yau conjectured that this result can be generalized to arbitrary dimension. They defined ``Mukai's elementary transformation'' as the blow-up of a subvariety ruled by complex projective spaces, composed with the contraction ...
Added: December 1, 2025
Zotov L., Юшкин В. Д., Фролова Н. Л. et al., , in: Информационные технологии и нанотехнологии (ИТНТ-2024). сборник трудов по материалам X Международной конференции и молодежной школы: в 6 томах.: Самарский государственный университет, 2024. P. 22002–22004.
The GRACE and GRACE-FO satellites provide data on the Earth's gravitational field changes and are among the most successful NASA/DLR geodetic missions in recent decades. Based on their data, the melting of glaciers, redistribution of masses in the river basins, and changes in the ocean mass are studied. We use multichannel singular spectral analysis (MSSA) ...
Added: May 30, 2025
Abrashkin A. A., World Scientific Publishing Co. Pte. Ltd, 2025.
This book is devoted to the problems of the analytical description of incompressible fluid flows in Lagrangian variables. Commonly, specialists in fluid dynamics prefer to use the Euler approach. For example, even classical textbooks by J. Batchelor, L.G. Loitsyansky, L.D. Landau, and E.M. Lifshitz do not provide the Lagrange equations of f luid dynamics. Exceptions ...
Added: January 28, 2025
Zotov L., Сидоренков Н. С., Марчукова О. В. et al., В кн.: ВОПРОСЫ ТЕОРИИ И ПРАКТИКИ ГЕОЛОГИЧЕСКОЙ ИНТЕРПРЕТАЦИИ ГРАВИТАЦИОННЫХ, МАГНИТНЫХ И ЭЛЕКТРИЧЕСКИХ ПОЛЕЙ 50-я юбилейная сессия Международного семинара им. Д.Г. Успенского - В.Н. Страхова. Москва, 2024.: М.: Издательство "Перо", 2024. С. 162–166.
Since strong El Nino 2016 the tendency of acceleration of the Earth rotation has been observed. In 2022 the Earth rotation velocity reached maxima comparable with those happened 90 years ago. Triplet of La Nina accompanied this case. Chandler wobble of the pole almost disappeared in 2017-2020, which was earlier observed only in the end ...
Added: March 1, 2024