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Finite-Dimensional 2-Generated Lie Algebras of Derivations on T-Varieties
Siberian Mathematical Journal. 2025. Vol. 66. No. 3. P. 715–727.
D. A. Matveev
We consider an affine algebraic variety with a torus action of complexity one. It is known
that in this case homogeneous locally nilpotent derivations on the algebra of functions of this variety
are defined in terms of a polyhedral divisor. In the present paper, a formula is obtained for multiple
commutators of two homogeneous locally nilpotent derivations with at most one derivation of horizontal
type. Using the obtained formula, a criterion is derived for finite dimensionality of Lie algebras generated
by a pair of homogeneous locally nilpotent derivations in the Lie algebra of all derivations of the algebra
of functions on a variety with a torus action.
Denis Seliutskii, Russian Journal of Mathematical Physics 2025 Vol. 32 No. 2 P. 399–407
In this paper, we find an upper bound for the first Steklov eigenvalue for a surface of revolution with boundary consisting of two spheres of different radii. Moreover, we prove that, in some cases, this boundary is sharp. ...
Added: May 19, 2026
Жакупов О. Б., European Journal of Mathematics 2025 Vol. 11 Article 84
We provide examples of smooth three-dimensional Fano complete intersections of degree 2, 4, 6, and 8 that have absolute coregularity 0. Considering the main theorem of Avilov, Loginov, and Przyjalkowski (CNTP 18:506–577, 2024) on the remaining 101 families of smooth Fano threefolds, our result implies that each family of smooth Fano threefolds has an element of absolute ...
Added: May 18, 2026
Lerman L. M., Turaev D. V., Regular and Chaotic Dynamics 2026 Vol. 31 No. 3 P. 349–369
We show that bifurcations of four-dimensional symplectic diffeomorphisms with a quadratic homoclinic tangency to a saddle periodic orbit with real multipliers produce 2-elliptic periodic orbits if the tangency is not partially hyperbolic. We show that a normal form for the rescaled first-return maps near such tangency is given by a four-dimensional symplectic H´enonlike map and study bifurcations of the ...
Added: May 15, 2026
Aleskerov F. T., Yakuba V. I., Khutorskaya O. et al., Springer, 2026.
The book contains new models of bibliometric analysis based on centrality measures in network analysis, pattern analysis and stability analysis. A distinctive feature of these centrality measures is that they account for the parameters of vertices and group influence of vertices to a vertex. This reveals specific groups of publications, authors, terms, journals and affiliations ...
Added: May 15, 2026
Kuptsov P., Panyushev A., Stankevich N., Chaos 2026 Vol. 36 No. 5 Article 053138
We develop a machine-learning approach to reproduce the behavior of two versions of the van der Pol oscillator exhibiting a subcritical Andronov–Hopf bifurcation, with or without a codimension-2 Bautin point. We construct a neural-network model that functions as a recur rent map and train it on short segments of oscillator trajectories. The results show that, ...
Added: May 15, 2026
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
Lebedev V., Journal of Mathematical Analysis and Applications 2026 Vol. 563 No. 2 Article 130787
It is known that for every continuous real-valued
function $f$ on the circle $\mathbb T=\mathbb R/2\pi\mathbb Z$ there exists a
change of variable, i.e., a self-homeomorphism $h$ of $\mathbb T$, such that
the superposition $f\circ h$ is in the Sobolev space $W_2^{1/2}(\mathbb T)$.
We obtain new results on simultaneous improvement of functions by a single
change of variable in relation ...
Added: May 14, 2026
Blokh A., Oversteegen L., Selinger N. et al., Arnold Mathematical Journal 2025 Vol. 12 No. 1 P. 1–40
We describe a model for the boundary of the connectedness locus of the parameter space of cubic symmetric polynomials. We show that there exists a monotone continuous function from the connectedness locus to the model which is a homeomorphism if the former is locally connected. ...
Added: May 13, 2026
Petrov I., Автоматика и телемеханика 2026 № 6 С. 82–118
Системам связанных агентов и сетевому управлению посвящено большое число отечественных и зарубежных исследований. Исторически, наибольший интерес в теории управления возникал к усредняющим системам и, в частности, к задаче консенсуса. Однако сетевое взаимодействие может характеризоваться более специфическими функциями, отражающими зависимость от действий соседей по сети, что особенно явно проявляется в моделях стратегического взаимодействия на сети, которое ...
Added: May 12, 2026
М.: ООО «Макс Пресс», 2026.
В настоящем сборнике представлены тезисы докладов участников семинара "Интеграция основного и дополнительного физико-математического образования", проходившего 11 февраля 2026 года в ГБОУ Школа №2007 ФМШ г. москвы, а также другие публикации, посвящённые вопросам дополнительного физико-математического образования. ...
Added: May 11, 2026
Novikov R., V. N. Sivkin, Inverse Problems 2026 Vol. 42 No. 4 Article 045009
We consider a plane wave, a radiation solution, and the sum of these solutions (total solution) for
the Helmholtz equation in an exterior region in Rd, d ⩾ 2. In this region, we consider a hyperplane X with sufficiently large distance s from the origin in Rd. We give two-point local formulas
for approximate recovering the radiation ...
Added: May 11, 2026
Hecht M., Hofmann P., Wicaksono D. et al., IMA Journal of Numerical Analysis 2026 Vol. 00 P. 1–30
Recent advances in Bernstein—Walsh theory have extended Bernstein’s Theorem to multiple dimensions, stating that a multivariate function can be approximated with a geometric rate in a downward-closed polynomial space if and only if it is analytic in a generalized Bernstein polyellipse. To compute approximations of this class of functions—which we term Bos–Levenberg–Trefethen–(BLT) functions—we extend the ...
Added: May 11, 2026
Kelbert M., Kalimulina E. Y., Entropy 2026 Vol. 28 Article 536
We study binary hypothesis testing for i.i.d. observations under a multiplicative context
weight. For the optimal weighted total loss, defined as the sum of weighted type-I and typeII losses, we prove the logarithmic asymptotic L∗n = exp{−nDwC (P,Q) + o(n)}, n →∞, where Dw
C is the weighted Chernoff information. The single-letter form of the exponent
relies on ...
Added: May 7, 2026
N. Belousov, L. Cherepanov, Derkachov S. et al., Selecta Mathematica, New Series 2026 Vol. 32 Article 44
We prove equivalence of two integral representations for the wave functions of hyperbolic Calogero–Sutherland system. For this we study two families of Baxter operators related to hyperbolic Calogero–Sutherland and rational Ruijsenaars models; the first one as a limit from hyperbolic Ruijsenaars system, while the second one independently. Besides, computing asymptotics of integral representations and also ...
Added: May 6, 2026
Kazaryan M., Kodaneva N., Lando S., Journal of Geometry and Physics 2026 Vol. 225 Article 105841
Weight systems associated to the Lie algebras 𝔤𝔩(N) for N = 1,2,... can be unified into auniversal one. The construction is based on an extension of the 𝔤𝔩(N) weight systems to permutations. This universal weight system takes values in the algebra of polynomials C[N;C1,C2,...] in infinitely many variables. We show that under the substitution Cm ...
Added: April 23, 2026
Kazaryan M., Krasilnikov E., Lando S. et al., Russian Mathematical Surveys 2025 Vol. 80 No. 6(486) P. 73–136
The paper is devoted to a description of the recent progress in understanding the extension of Lie algebra weight systems to permutations. Lie algebra weight systems are functions on chord diagrams arising naturally in Vassiliev's theory of finite-type knot invariants. These functions satisfy certain linear restrictions known as Vassiliev's 4-term relations.
Chord diagrams can be interpreted as fixed-point-free involutions in ...
Added: December 4, 2025
Rassolov K., Математические заметки 2025 Т. 118 № 4 С. 575–593
Рассматривается наиболее тонкая градуировка на алгебре регулярных функций триномиального многообразия, относительно которой однородны все координатные функции. Получен явный вид однородных относительно этой градуировки локально нильпотентных дифференцирований. ...
Added: September 19, 2025
Dasgupta N., Gayfullin S., Математический сборник 2025 Т. 216 № 4 С. 3–34
В этой работе мы изучаем локально нильпотентные дифференцирования на алгебре многочленов от трех переменных над полем нулевой характеристики. Мы вводим итерационную конструкцию, дающую все локально нильпотентные дифференцирования ранга 2. Эта конструкция позволяет нам построить примеры нетриангуляризуемых локально нильпотентных дифференцирований ранга 2. Также мы показываем, что известный пример локально нильпотентного дифференцирования ранга 3, построенный Фройденбургом, может быть включен в большое ...
Added: July 1, 2025
Arzhantsev I., Russian Mathematical Surveys 2001 Vol. 56 No. 3 P. 569–571
Added: June 13, 2025
Arzhantsev I., Gayfullin S., Lopatkin V., Izvestiya. Mathematics 2025 Vol. 89 No. 3 P. 425–441
For a finite set of homogeneous locally nilpotent derivations of the algebra of polynomials in several variables, a finite dimensionality criterion for the Lie algebra generated by these derivations is known. The structure of the corresponding finite-dimensional Lie algebras was also described in previous works. In this paper, we obtain a finite dimensionality criterion for ...
Added: June 12, 2025
Arzhantsev I., Gayfullin S., Lopatkin V., Известия РАН. Серия математическая 2025 Т. 89 № 3 С. 5–22
For a finite set of homogeneous locally nilpotent derivations of the algebra of polynomials
in several variables, a finite dimensionality criterion for the Lie algebra generated by these
derivations is known. Also the structure of the corresponding finite-dimensional Lie algebras is
described in previous works. In this paper, we obtain a finite dimensionality criterion for a Lie
algebra generated ...
Added: May 31, 2025
Lando S., Yang Z., Annales de l'Institut Henri Poincare (D) Combinatorics, Physics and their Interactions 2025
n a recent paper by M. Kazarian and the second author, a recurrence for the Lie algebras so(N) weight systems has been suggested; the recurrence allows one to construct the universal so weight system. The construction is based on an extension of the so weight systems to permutations. Another recent paper, by M. Kazarian, N. Kodaneva, and the first author, shows that under the ...
Added: May 15, 2025
Kodaneva N., Lando S., Journal of Geometry and Physics 2025 Vol. 210 Article 105421
Weight systems are functions on chord diagrams satisfying so-called Vassiliev’s 4-term relations. They are closely related to finite type knot invariants, see [31 Certain weight systems can be derived from graph invariants, see a recent account in [19]. Another main source of weight systems are Lie algebras, the construction due to D. Bar-Natan [3] and ...
Added: January 23, 2025
Roman Avdeev, Vladimir Zhgoon, / Series arXiv "math". 2024. No. 2312.03377.
Given a connected reductive algebraic group G and a spherical G-variety X, a B-root subgroup on X is a one-parameter additive group of automorphisms of X normalized by a Borel subgroup B⊂G. We obtain a complete description of all B-root subgroups on a certain open subset of X. When X is horospherical, we extend the construction of standard B-root subgroups introduced earlier by Arzhantsev and Avdeev for affine X and obtain a ...
Added: December 17, 2024