A proof from the book,perchance

Journal of Algebraic Combinatorics - The fact that the groups $${\mathbb {Z}}_{2^m} \times {\mathbb {Z}}_{2^m}$$ contain difference sets was first established by induction by Jim Davis in his...     

A free boundary problem arising from DCIS mathematical model

Ductal carcinoma in situ – a special cancer – is confined within the breast ductal only. We derive the mathematical ductal carcinoma in situ model in a form of a nonlinear parabolic equation with initial, boundary, and free boundary conditions. Existence, uniqueness, and stability of problem are proved. Algorithm and illustrative examples are included to demonstrate the validity and applicability of the technique in this paper. Copyright © 2016 John Wiley & Sons, Ltd.     

Singular open book structures from real mappings

We define open book structures with singular bindings. Starting with an extension of Milnor’s results on local fibrations for germs with nonisolated singularity, we find classes of genuine real analytic mappings which yield such open book structures.     

More from the mathematical ethicist

Opening a copy ofThe Mathematical Intelligencer you may ask yourself uneasily, “What is this anyway—a mathematical journal, or what?” Or you may ask, “Where am I?” Or even “Who am I?” This sense of disorientation is at its most acute when you open to Colin Adams’s column.Relax. Breathe regularly. It’s mathematical, it’s a humor column, and it may even be harmless.     

A mathematical analysis for a model arising from public goods games

We study the effects of altruistic behaviors in a public goods game model which describes the competition between the farmers and the exploiters. Corresponding to different parametric regions, we analyze in detail the stability of the equilibrium states and obtain attraction regions for stable equilibria. Then using the upper–lower solution method and monotone iterations, we further show that for a family of wave speeds, there exist traveling wave solutions connecting one of the unstable states to the stable state. This answers a conjecture made by Wakano in [J.Y. Wakano, A mathematical analysis on public goods games in the continuous space, Math. Biosci. 201 (2006) 72–89]. The results indicate that when the penalty for the altruistic behavior is small, the growth rate of the population determines its survival or extinction states in the long run. Furthermore, if the two populations have the same total growth rate, altruism in the competition leads to a wide range of co-existent states. Numerical simulations are also presented to illustrate the theoretical results.     

A mathematical model for unemployment

In this paper we have proposed and analyzed a non-linear mathematical model for unemployment by considering three variables, namely the numbers of unemployed, temporarily employed and regularly employed persons. The model is studied using the stability theory of differential equations. It is found that the model has only one equilibrium, which is non-linearly stable under certain conditions. Numerical simulation of the model has been carried out to confirm the analytical results.     

A mathematical theory of climbing

Is it possible to develop a theory of climbing? The answer isno. Mountains are so different in quality of rock and geometryof their faces that any wall would require a specific theoryon the best strategy for being climbed. For this reason, climbingschools, so precise in teaching belaying, rappelling and prusiking,are instead vague in instructing how one must progress alongan irregular wall. This paper suggests a rough model for graspingthis complex problem.     

A social perspective on technology-enhanced mathematical learning: from collaboration to performance

This paper documents both developments in the technologies used to promote learning mathematics and the influence on research of social theories of learning, through reference to the activities of the International Commission on Mathematical Instruction (ICMI), and argues that these changes provide opportunity for the reconceptualization of our understanding of mathematical learning. Firstly, changes in technology are traced from discipline-specific computer-based software through to Web 2.0-based learning tools. Secondly, the increasing influence of social theories of learning on mathematics education research is reviewed by examining the prevalence of papers and presentations, which acknowledge the role of social interaction in learning, at ICMI conferences over the past 20 years. Finally, it is argued that the confluence of these developments means that it is necessary to re-examine what it means to learn and do mathematics and proposes that it is now possible to view learning mathematics as an activity that is performed rather than passively acquired.     

The vehicle routing problem: A book review

We review the recent book, edited by Paolo Toth and Daniele Vigo, The Vehicle Routing Problem, SIAM Monographs on Discrete Mathematics and Applications 2002, ISBN: 0-89871-498-2, price: 95 USD.