{"title":"The Arithmetic of Points on a Conic and Projectivities","authors":"H. Coxeter, G. Beck","doi":"10.3888/TMJ.21-2","DOIUrl":"https://doi.org/10.3888/TMJ.21-2","url":null,"abstract":"","PeriodicalId":91418,"journal":{"name":"The Mathematica journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69962562","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Peak Response of Single-Degree-of-Freedom Systems to Swept-Frequency Excitation","authors":"Christopher H. Reed, A. Kabe","doi":"10.3888/tmj.21-1","DOIUrl":"https://doi.org/10.3888/tmj.21-1","url":null,"abstract":"","PeriodicalId":91418,"journal":{"name":"The Mathematica journal","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69962503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
I. Falcão, Fernando Miranda, R. Severino, Joana Soares
{"title":"Computational Aspects of Quaternionic Polynomials - Part I: Manipulating, Evaluating and Factoring","authors":"I. Falcão, Fernando Miranda, R. Severino, Joana Soares","doi":"10.3888/TMJ.20-4","DOIUrl":"https://doi.org/10.3888/TMJ.20-4","url":null,"abstract":"Research at the Centre of Mathematics at the University of Minho was financed by Portuguese Funds \u0000through FCT - Fundacao para a Ciencia e a Tecnologia, within the Project UID/MAT/00013/2013. Research \u0000at the Economics Politics Research Unit was carried out within the funding with COMPETE \u0000reference number POCI-01-0145-FEDER-006683 (UID/ECO/03182/2013), with the FCT/MEC’s \u0000(Fundacao para a Ciencia e a Tecnologia, I.P.) financial support through national funding and by the \u0000European Regional Development Fund through the Operational Programme on “Competitiveness and \u0000Internationalization - COMPETE 2020” under the PT2020 Partnership Agreement.","PeriodicalId":91418,"journal":{"name":"The Mathematica journal","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42504197","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Improving the Kruskal–Katona Bounds for Complete Subgraphs of a Graph","authors":"R. Cowen","doi":"10.3888/TMJ.20-6","DOIUrl":"https://doi.org/10.3888/TMJ.20-6","url":null,"abstract":"","PeriodicalId":91418,"journal":{"name":"The Mathematica journal","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69962375","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"The Modular Group","authors":"P. Mccreary, Teri Jo Murphy, Christan Carter","doi":"10.3888/TMJ.20-3","DOIUrl":"https://doi.org/10.3888/TMJ.20-3","url":null,"abstract":"The modular group Γ is the set of all 2 × 2 matrices with integral elements and determinant 1. That is, Γ is the special linear group of 2 × 2 matrices over the integers, Γ = SL(2, Z). It forms a group under matrix multiplication. If M = a b c d ∈ Γ Then M defines a map f M (z) = az + b cz + d of the extended complex plane to itself. Here f M (−d/c) = ∞, and f M (∞) = a/c. Suppose that N = α β γ δ. Then by direct calculation we find that f N (f M (z)) = (αa + βc)z + (αb + βd) (γa + δc)z + (γb + δd) = f N M (z). While it might seem surprising that the composition of one such rational function with another would be connected with matrix multiplication, the mystery can be dispelled by considering how M and N transform the 2-dimensional vectors C 2. Suppose that M z 1 z 2 = w 1 w 2 , N w 1 w 2 = t 1 t 2. Then N M z 1 z 2 = t 1 t 2. Now suppose we consider these vectors in terms of projective geometry. Two vectors are then considered to be the same if their coordinates are proportional (i.e., the vectors are colinear). In other words, if c is a non-zero complex number, then z 1 z 2 and cz 1 cz 2 are considered to be the same. Thus a projective point z 1 : z 2 is determined by the ratio z = z 1 /z 2 if its coordinates, and the image w 1 : w 2 is determined by the ratio w = w 1 /w 2 of its coordinates. But then w = w 1 w 2 = az 1 + bz 2 cz 1 + dz 2 = az 1 /z 2 + b cz 1 /z 2 + d = az + b cz + d , so the map from z to w reflects a linear transformation in projective coordinates.","PeriodicalId":91418,"journal":{"name":"The Mathematica journal","volume":"9 1","pages":"564-582"},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69962348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"A Wolfram Language Approach to Real Numerical Algebraic Plane Curves","authors":"Barry H. Dayton","doi":"10.3888/tmj.20-7","DOIUrl":"https://doi.org/10.3888/tmj.20-7","url":null,"abstract":"","PeriodicalId":91418,"journal":{"name":"The Mathematica journal","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69962388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Aspects of Input Shaping Control of Flexible Mechanical Systems","authors":"D. Adair, M. Jaeger","doi":"10.3888/TMJ.19-3","DOIUrl":"https://doi.org/10.3888/TMJ.19-3","url":null,"abstract":"","PeriodicalId":91418,"journal":{"name":"The Mathematica journal","volume":"19 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"69962731","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}