The complexity of Dehn's algorithm for word problems in groups

Given the presentation for a group of Dehn's algorithm, a multitape Turing machine is shown to exist that solves the word problem for that presentation in linear time. Key to this solution is the pattern matching methodology from complexity theory as well as a recent result for confluent Thue systems.     

The projective geometry of Mario Pieri: A legacy of Georg Karl Christian von Staudt

The research of Mario Pieri (1860–1913) can be classified into three main areas: metric differential and algebraic geometry and vector analysis; foundations of geometry and arithmetic; logic and the philosophy of science. In writing this article, I intend to reveal some important aspects of his contributions to the foundations of projective geometry, notably those that emanated from his intensive study of the works of Georg Karl Christian von Staudt (1798–1867). Pieri was the first geometer to successfully establish projective geometry as an independent subject (rigorous mathematical theory), freed from all ties to Euclidean geometry. The path to this achievement began with Staudt, and involved the reformulation of the classical ideas of cross ratio and projectivity in terms of harmonic sets, as well as a critical analysis of the proof of a fundamental theorem that connects these ideas. Included is a brief overview of Pieri's life and work.     

Johann Heinrich Lambert,mathematician and scientist, 1728 – 1777

1977 is the two hundredth anniversary of the death of Johann Heinrich Lambert, a little known but nonetheless intriguing figure in 18th century science. In the general histories of science and mathematics Lambert's contributions are often described piecemeal, with each discovery and invention usually divorced both from the method by which he arrived at it and from the totality of his intellectual endeavour. To the student of optics he is remembered for his cosine law in photometry, to the astronomer for his work on comets, to the meteorologist for his design of a gut hygrometer, and to the mathematician for his work on non-Euclidean geometry and his demonstration of the irrationality of π and e. There is no doubt that each of these contributions had a definite importance of its own; but it is not the aim of the present article to enumerate in this way the high points of Lambert's scientific and mathematical work, rather to describe it for once as a unified whole, and to relate it to the contemporary intellectual outlook.     

Serendipity

The aim of this short paper, is to show how serendipity was a key input in the research that led Ivar’s to two of his main contributions: proof of an old Hamiltonian systems conjecture using devices from the math eco tool box, then smart investigation of family’s budget decision process using symplectic geometry. Of course anyone is expected to say: “you mean: symplectic tools for Hamiltonians, and math eco toolkit for family budget.” Here is the point: these Ivar’s works illuminate how much serendipity creates unexpected brilliant results.     

Mario Pieri’s address at the University of Catania

The contributions made by the Italian mathematician Mario Pieri (1860-1913) are well known in the field of geometry. Pieri was a member of the School of Peano at the University of Turin. There he became engaged both by the problems of logic and by the philosophical aspects of Peano’s epistemology. This article was motivated by Pieri’s address given at the University of Catania, at the inauguration of the 1906-1907 academic year. My aim is to identify Pieri’s philosophical premises as found in his works and to present them in the general framework of the historical development of the Peano School.     

Gauss as a geometer

In an attempt to reveal the breadth of Gauss's interest in geometry, this account is divided into six chapters. The first mentions the fundamental theorem of algebra, which can be proved only with the aid of geometric ideas, and in return, an application of algebra to geometry: the connection between the Fermat primes and the construction of regular polygons. Chapter 2 shows his essentially ‘modern’ approach to quaternions. Chapter 3 is a sample of his work in trigonometry. Chapter 4 deals with his approach to the geometry of numbers. Chapter 5 sketches his differential geometry of surfaces: his use of two parameters, the elements of distance and area, his theorema egregium, and the total curvature of a geodesic polygon. Finally, Chapter 6 shows that he continually returned to the subject of non-Euclidean geometry, which was so precious and personal that he would not publish anything of it during his lifetime, and yet did not wish to let it perish with him.     

Descartes and the geometrization of thought: The methodological background of Descartes' géométrie

After the relationship between geometry and algebra exemplified in his distinction between geometrical and mechanical lines is examined, the basis for Descartes' limited approach to analytical geometry is discussed in connection with his reflections on method. It is argued that his epistemology, which required that conceptual thinking be accompanied by a construction supplied by the imagination, in conjunction with the significant role he attributed to mnemonic devices, helps to clarify the methodological background for Descartes' distinctive approach to geometry.     

Torsten Brodén's work on the foundations of Euclidean geometry

The Swedish mathematician Torsten Brodén (1857–1931) wrote two articles on the foundations of Euclidean geometry. The first was published in 1890, almost a decade before Hilbert's first attempt, and the second was published in 1912. Brodén's philosophical view of the nature of geometry is discussed and his thoughts on axiomatic systems are described. His axiomatic system for Euclidean geometry from 1890 is considered in detail and compared with his later work on the foundations of geometry. The two continuity axioms given are compared to and proved to imply Hilbert's two continuity axioms of 1903.     

Hermann Minkowski’s approach to physics

Hermann Minkowski’s contributions to relativity theory are extraordinary from a disciplinary standpoint, in that so few mathematicians in Wilhelmine Germany took an interest in theoretical physics. Based on correspondence, lectures, research notes and the accounts of his students and colleagues, Minkowski’s interest in mechanics and physics is retraced, from his early career to his discovery of spacetime.     

Arnold Kirsch and mathematics education

This article pays tribute to the German mathematics educator Arnold Kirsch (1922–2013), especially for his contributions to calculus education. The main aim of his work was to make mathematics accessible to learners so that they are able to genuinely understand the subject.     

对话李克正教授：为什么学习代数几何

以与首都师范大学的李克正教授对话的方式,通过其口简要介绍代数几何这门重要学科在我国的早期发展情况,详细回忆李克正教授在国外学习代数几何的过程,以及他回国后的教学与研究成果,并通俗地阐述代数几何方法对于解决重大数论问题所起的关键作用．     

Rethinking geometrical exactness

A crucial concern of early modern geometry was fixing appropriate norms for deciding whether some objects, procedures, or arguments should or should not be allowed into it. According to Bos, this is the exactness concern. I argue that Descartes’s way of responding to this concern was to suggest an appropriate conservative extension of Euclid’s plane geometry (EPG). In Section 2, I outline the exactness concern as, I think, it appeared to Descartes. In Section 3, I account for Descartes’s views on exactness and for his attitude towards the most common sorts of constructions in classical geometry. I also explain in which sense his geometry can be conceived as a conservative extension of EPG. I conclude by briefly discussing some structural similarities and differences between Descartes’s geometry and EPG.     

Forward

Tatsien LI Fanghua LIN Guiqiang CHEN Xiaoming WANG Professor Andrew Majda is one of the most prominent applied mathematicians in the world. He is well-known for both his seminal theoretical contributions to partial differential equations and his diverse and fundamental contributions to many applied areas such as scattering theory, shock waves, combustion, incompressible flow, vortex motion, turbulent diffusion and atmosphere ocean science.     

Robert Patterson: American ‘revolutionary’ mathematician

You will not see Robert Patterson’s name mentioned in many mathematics books. While his mathematical works survive, his name is more likely to appear in American history books dealing with the Colonial period, given his associations with the most influential men of that time. In this article, we will examine his mathematical work, as well as his contributions to a newly-formed nation. Most of what we know about Robert Patterson’s ancestors and life is due to his grandson, William Ewing DuBois, who wrote a family history in 1847. For other information, I have drawn upon diaries and a great many letters. All spelling and syntax are copied exactly as they appear.     

Physics and Mathematics Without Coordinates

The author presents his views on how physics should be phrased in a coordinate-free manner. Examples are given, which range from classical Continuum Mechanics to Special and General Relativity, in a narrative that hinges on the author’s original contributions to these fields.     

Aldo Cossu’s Work in Finite Geometry

A survey of the contributions of Aldo Cossu in finite geometry is given. Dedicated to the memory of Professor Aldo Cossu     

Hjelmslev's geometry of reality

During the first half of the 20th century the Danish geometer Johannes Hjelmslev developed what he called a geometry of reality. It was presented as an alternative to the idealized Euclidean paradigm that had recently been completed by Hilbert. Hjelmslev argued that his geometry of reality was superior to the Euclidean geometry both didactically, scientifically and in practice: Didactically, because it was closer to experience and intuition, in practice because it was in accordance with the real geometrical drawing practice of the engineer, and scientifically because it was based on a smaller axiomatic basis than Hilbertian Euclidean geometry but still included the important theorems of ordinary geometry. In this paper, I shall primarily analyze the scientific aspect of Hjelmslev's new approach to geometry that gave rise to the so-called Hjelmslev (incidence) geometry or ring geometry.     

Multigroups and the foundations of geometry

The aim of this paper is to show that the foundations of geometry and the theory of moultigroups are strictly related. Dedicated to Helmut Salzmann on his 60^th birthady.     

线性代数课堂中的“教”与“学”

结合教学实践经验,从人才培养的角度阐述线性代数课堂教学中的思维培养问题.指出课堂教学中要善于创设和营造和谐民主、积极向上、与学生心理相融的良好的课堂氛围;设置有利于学生参与认知的教学环节,通过采用灵活的教学方式,激发学生思考;尊重学生主体地位,让他们在教学活动中获得最大的情感体验;充分利用直观形象思维,教学中贯穿直观的几何形象,激发学生学习的兴趣,激发他们的求知欲.     

Non-Euclidean geometry and Weierstrassian mathematics: The background to Killing's work on Lie algebras

A discussion of the manner in which discoveries in non-Euclidean geometry, combined with the Weierstrassian attitude towards mathematics, led Wilhelm Killing, one of Weierstrass' students, to initiate a research program on foundations of geometry that led to his groundbreaking investigations on the structure of Lie algebras.