C. S. Peirce and De Morgan on the four-colour conjecture
نویسندگان
چکیده
منابع مشابه
On the Four-colour Conjecture
Introduction and summary FOR the purposes of the four-colour conjecture it is convenient to consider only undirected graphs without loops and without multiple edges. In this paper an abstract graph F is taken to mean a set T^(F), whose elements are called the vertices of F, together with a set <5*(F), whose elements are unordered pairs of distinct vertices of F and are called the edges of F; an...
متن کاملOn the Four Colour Conjecture 137 on the Four - Colour Conjecture
1. Introduction The maps discussed in this paper are dissections of surfaces into simple polygons, called regions. In each map it is supposed that the regions are finite in number and that each vertex of a region is common to just three regions. Sides and vertices of the regions will be called edges and vertices of the map respectively. A colouring of a map M is defined as a set of four mutuall...
متن کاملBelnap's Four-Valued Logic and De Morgan Lattices
In my paper [3], recently published in this Journal, I study several aspects of the relations between Belnap's logic B and the class DM of De Morgan lattices. Some of these relations concern a Gentzen system for Belnap's logic, denoted by G B , which was introduced in 1988 by my colleague Ventura Verdú and me (see [5] and [6]); indeed, the study of this Gentzen system within the theory of full ...
متن کاملOn the (−1)-curve conjecture of Friedman and Morgan
We will prove that every differentiably embedded sphere with selfintersection −1 in a simply connected algebraic surface with pg > 0 is homologous to an algebraic class. If the surface has a minimal model with Picard number 1 or |Kmin| contains a smooth irreducible curve of genus at least 2, and pg is even or K 2 min 6≡ 7 (mod 8), then every such sphere is homologous to a (−1)-curve, as conject...
متن کاملDe Morgan Triples Revisited
In this paper we overview basic known results about the varieties generated by De Morgan triples and about the problem to find equations defining the variety generated by a concrete De Morgan triple. We also provide some alternative proofs and some new results, specially for the case of Łukasiewicz De Morgan triples.
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Historia Mathematica
سال: 1977
ISSN: 0315-0860
DOI: 10.1016/0315-0860(77)90118-5