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We study scattering equations of hyperplane arrangements from the perspective of combinatorial commutative algebra and numerical algebraic geometry. We formulate the problem as linear equations on a reciprocal linear space and develop a degeneration-based homotopy algorithm for solving them. We investigate the Hilbert regularity of the corresponding homogeneous ideal and apply our methods to CHY scattering equations.

Using novel metallic magnetic calorimeter detectors at the CRYRING@ESR, we recorded X-ray spectra of stored and electron cooled helium-like uranium (U$^{90+}$) with an unmatched spectral resolution of close to 90 eV. This allowed for an accurate determination of the energies of all four components of the K$\alpha$ transitions in U$^{90+}$. We find good agreement with state-of-the-art bound-state QED calculations for the strong-field regime. Our results do not support any systematic deviation between experiment and theory in helium-like systems, the presence of which was subject of intense debates in recent years.

We give a review of one of the lines in development of the theory of groups of finite Morley rank. These groups naturally appear in model theory as model-theoretic analogues of Galois groups, therefore their actions and their role as permutation groups is of primary interest. We restrict our story to the study of connected groups of finite Morley rank $G$ acting in a definably primitive way on a set $X$ and containing a definable abelian normal subgroup $V$ which acts on $X$ regularly -- the so-called \emph{primitive groups of affine type}. For reasons explained in the paper, this case plays a central role in the theory., Comment: Some typos were corrected, a few wordings were changed, bibliography was updated

An induced additive action on a projective variety $X \subseteq \mathbb{P}^n$ is a regular action of the group $\mathbb{G}_a^m$ on $X$ with an open orbit, which can be extended to a regular action on the ambient projective space $\mathbb{P}^n$. In this work, we classify all projective hypersurfaces admitting an induced additive action with a finite number of orbits.

We introduce a detection algorithm for SAGBI basis in polynomial rings, analogous to a Gr\"obner basis detection algorithm previously proposed by Gritzmann and Sturmfels. We also present two accompanying software packages named SagbiGbDetection for Macaulay2 and Julia. Both packages allow the user to find one or more term orders for which a set of input polynomials form either Gr\"obner basis for the ideal they generate or a SAGBI basis for the subalgebra. Additionally, we investigate the computational complexity of homogeneous SAGBI detection and apply our implementation to several novel examples.

We present new experimental and theoretical cross sections for electron-impact single ionization of Xe$^{12+}$ and Xe$^{13+}$ ions, and double ionization of Xe$^{12+}$, Xe$^{13+}$ and Xe$^{14+}$ ions for collision energies from the respective ionization thresholds up to 3500 eV. The calculations use the fully relativistic subconfiguration-averaged distorted-wave (SCADW) approach and, partly, the more detailed level-to-level distorted wave (LLDW) method. We find that, unlike in previous work, our theoretical cross sections agree with our experimental ones within the experimental uncertainties, except for the near-threshold double-ionization cross sections. We attribute this remaining discrepancy to the neglect of direct-double ionization in the present theoretical treatment., Comment: 12 pages, 9 figures, 1 table

In this work, we complete the classification of generically multiply transitive actions of groups on solvable groups in the finite Morley rank setting. We prove that if $G$ is a connected group of finite Morley rank acting definably, faithfully and generically $m$-transitively on a connected solvable group $V$ of finite Morley rank where $\operatorname{rk}(V)\leqslant m$, then $\operatorname{rk}(V)=m$, $V$ is a vector space of dimension $m$ over an algebraically closed field $F$, $G\cong \operatorname{GL}_m(F)$, and the action is equivalent to the natural action of $\operatorname{GL}_m(F)$ on $F^m$. This generalises our previous work arXiv:2107.09997. As an application of our result, we classify definably primitive groups of finite Morley rank and affine type acting on a set $X$ with a generic transitivity degree of $\operatorname{rk}(X)+1$., Comment: A new section on definably primitive groups of affine type is added

This paper provides an example of structural proxies for black box rings encrypting rings of 2 by 2 matrices of finite fields of odd order.

We determine the number of complex solutions to a nonlinear eigenvalue problem on the Grassmannian in its Pl\"ucker embedding. This is motivated by quantum chemistry, where it represents the truncation to single electrons in coupled cluster theory. We prove the formula for the Grassmannian of lines which was conjectured in earlier work with Fabian Faulstich. This rests on the geometry of the graph of a birational parametrization of the Grassmannian. We present a squarefree Gr\"obner basis for this graph, and we develop connections to toric degenerations from representation theory., Comment: 13 pages

We provide an approach to counting roots of polynomial systems, where each polynomial is a general linear combination of prescribed, fixed polynomials. Our tools rely on the theory of Khovanskii bases, combined with toric geometry, the Bernstein-Khovanskii-Kushnirenko (BKK) Theorem, and fiber products. As a direct application of this theory, we solve the problem of counting the number of approximate stationary states for coupled driven nonlinear resonators. We set up a system of polynomial equations that depends on three numbers $N, n$ and $M$ and whose solutions model the stationary states. The parameter $N$ is the number of coupled resonators, $2n - 1$ is the degree of nonlinearity of the underlying differential equation, and $M$ is the number of frequencies used in the approximation. We use our main theorems, that is, the generalized BKK Theorem and the Decoupling Theorem, to count the number of (complex) solutions of the polynomial system for an arbitrary degree of nonlinearity $2n - 1 \geq 3$, any number of resonators $N \geq 1$, and $M = 1$ harmonic. We also solve the case $N = 1, n = 2$ and $M = 2$ and give a computational way to check the number of solutions for $N = 1, n = 2$ and $M \geq 2$. This extends the results of arXiv:2208.08179.

The Parameter Continuation Theorem is the theoretical foundation for polynomial homotopy continuation, which is one of the main tools in computational algebraic geometry. In this note, we give a short proof using Gr\"obner bases. Our approach gives a method for computing discriminants.

University level mathematics in a number of countries is under pressure to `decolonise the curriculum'. This paper considers, as a test case, a possible `decolonisation' of linear algebra. This is a representative case, since linear algebra is one of the core courses of undergraduate mathematics and a mathematical discipline with a millennia long historic tradition. This paper is written for my colleagues, university mathematicians. In my opinion, it could help them to determine their position and calmly stick to it without entering into an unnecessary debate with promoters of `decolonisation of the curricula'. The paper offers a simple and honest defence against `decolonisation' pressures: tell students the real (pre)history of a particular mathematical discipline. Let us call this activity `historical enrichment'. It would be useful if all attempts at `decolonization' (and vice versa, `historical enrichment') were known to a wider circle of the mathematical community. Publicity and an open discussion are the best way to resist outside pressures to engage in virtue signalling at the expense of historical and mathematical truth. The international mathematical community should defend academic freedom and insist on our right to formulate our curricula and evaluate the history of mathematics and judge mathematicians of the past according to criteria developed within the profession, and ignore any kind of political fads and pressure, Comment: 13 pp. Submitted for publication. Changes from Version 3: former Section 6 is deleted and will be used in another paper, plus some corrections and minor changes

The words ``Programming is the second literacy'' were coined more than 40 years ago but never came to life. This paper is one in the series of papers aimed at the analysis of mathematical requirements for a merge of school mathematics with computer science and computer programming. First indications are this demands development of quite serious mathematical tools most of which, hopefully, will be hidden "under the hood'' of software systems used in the process, but many will feature prominently in the Domain Specific Language needed for support of mathematical exchanges between Learner, Teacher, and Computer. We focus on "hardcore" mathematical aspects of this development., Comment: 23 pp. Submitted for publication

Leibniz scholarship is currently an area of lively debate. We respond to some recent criticisms by Archibald et al., Comment: 2 pages, appeared in The Mathematical Intelligencer

In the history of infinitesimal calculus, we trace innovation from Leibniz to Cauchy and reaction from Berkeley to Mansion and beyond. We explore 19th century infinitesimal lores, including the approaches of Simeon-Denis Poisson, Gaspard-Gustave de Coriolis, and Jean-Nicolas Noel. We examine contrasting historiographic approaches to such lores, in the work of Laugwitz, Schubring, Spalt, and others, and address a recent critique by Archibald et al. We argue that the element of contingency in this history is more prominent than many modern historians seem willing to acknowledge., Comment: 60 pages

In the Soviet Union a reform movement in mathematics education was triggered by Andrey Kolmogorov in the 1970s, and followed by a counter-reform. This movement was rooted in the very different socioeconomic conditions of that time and place, and followed a strategy with very significant contrasts to similar programs in the USA, England, or France. This provides an interesting case study which may illuminate the way such movements arise and succeed or fail, and, at the social level, certain fundamental commonalities of constraints as well as significant differences according to local conditions. We shall show that the principal reasons of the failure of the Kolmogorov reform were political: (1) The reform ignored the reality of the socio-economic conditions of the country; (2) The human factor was ignored, and very little attention was given to professional development and retraining of, and methodological help to, the whole army of teachers; (3) An attempt to transfer mathematical content and methods from the highly successful advanced extension stream for mathematically strong and highly engaged children to mainstream education was an especially grievous error., Comment: This is a pre-print of the following chapter: Alexandre Borovik, The Kolmogorov Reform of Mathematics Education in the USSR, published in Modern mathematics. An international movement?, edited by Dirk De Bock, 202X, Springer, reproduced with permission of Springer Nature Switzerland AG. The final authenticated version will become available online at: http://dx.doi.org/[to be confirmed]

Mathematics enters the period of change unprecedented in its history, perhaps even a revolution: a switch to use of computers as assistants and checkers in production of proofs. This requires rethinking traditional approaches to mathematics education which is struggling through a crisis of its own, socio-economic and political by its nature. The mathematical community faces Pandora's box of problems, which, surprisingly, are not usually discussed in any connected form. The present paper attempts to address this issue in a bit more joint and cohesive way., Comment: Submitted for possible open access publication under the terms and conditions of the Creative Commons Attribution (CC BY) license

We investigate the configuration where a group of finite Morley rank acts definably and generically $m$-transitively on an elementary abelian $p$-group of Morley rank $n$, where $p$ is an odd prime, and $m\geqslant n$. We conclude that $m=n$, and the action is equivalent to the natural action of $\operatorname{GL}_n(F)$ on $F^n$ for some algebraically closed field $F$. This strengthens our earlier result in arXiv:1802.05222, and partially answers two problems posed in [9]., Comment: To appear in \textit{Model Theory}. The manuscript will undergo copy editing, typesetting, and review of the resulting proof before it is published

This paper is an introduction to our ongoing more comprehensive work on a critically important period in the history of Russian mathematics education; it provides a glimpse into the socio-political environment in which the famous Soviet tradition of mathematics education was born. The authors are practitioners of mathematics education in two very different countries, England and Russia. We have a chance to see that too many trends and debates in current education policy resemble battles around mathematics education in the 1920s and 1930s Soviet Russia. This is why this period should be revisited and re-analysed, despite quite a considerable amount of previous research. Our main conclusion: mathematicians, first of all, were fighting for control over selection, education, and career development, of young mathematicians. In the harshest possible political environment, they were taking potentially lethal risks.

In this paper we describe orbits of automorphism group on a horospherical variety in terms of degrees of homogeneous with respect to natural grading locally nilpotent derivations. In case of (may be non-normal) toric varieties a description of orbits of automorphism group in terms of corresponding weight monoid is obtained.

This paper discusses, from a mathematician's point of view, the thesis formulated by Israel Gelfand, one of the greatest mathematicians of the 20th century, and one of the pioneers of mathematical biology: "There is only one thing which is more unreasonable than the unreasonable effectiveness of mathematics in physics, and this is the unreasonable ineffectiveness of mathematics in biology."

The classical platonist / formalist dilemma in philosophy of mathematics can be expressed in lay terms as a deceptively naive question: \emph{Is new mathematics discovered or invented? Using examples from my own mathematical work during the Coronavirus lockdown, I argue that there is also a third way: new mathematics can also be inherited. And entering into possession, making it your own, could be great fun., Comment: A shorter version of the paper (roughly Sections 1 to 4) appeared as: Borovik A. (2020) A View from Lockdown: Mathematics Discovered, Invented, and Inherited. In: . Mathematics Online First Collections. Springer, Cham. https://doi.org/10.1007/16618_2020_6