5 Matching Annotations
  1. Sep 2024
    1. Z orn ’s lemma. Suppose S, < is a partially ordered set with the property that every chain in S has an upper bound. Then S contains amaximal element.

      typo : < should be ≤

    2. The axiom o f choice. Suppose {Si}, i E I, is a family of nonemptysets. Then there is a function / from I into U / Si such that f(i) E Sifor each i e I.

      For any collection of non-empty sets, one can create a set by choosing one element from each set in the given collection.

      There are a variety of other equivalent ways to state this as well as names. One variation is Zorn's lemma.

    3. Gemignani, Michael C. Elementary Topology. 2nd ed. Addison-Wesley Series in Mathematics. Reading, MA: Addison-Wesley Publishing Company, 1971.

      Annotations URL<br /> Alternate annotations URL

    4. opology has reached the point where a mathematician engagedin topological research is not only justified in calling himself a topologist,but he must specify whether he is a point set topologist, differentialtopologist, algebraic topologist, or some other topological specialist.

      sub-branches of topology: - point-set topology<br /> - differential topology<br /> - algebraic topology

    5. Geometrically, topologywas the study of properties preserved by a certain group of transformations, the homeomorphisms. Geometry itself can be considered as thestudy of properties preserved by certain types of functions; e.g., Euclideanmetric geometry is the study of properties preserved by rigid (that is,distance-preserving) transformations (known sometimes as congruences).(Of course, as with topology, it is somewhat unfair to try to define geometry as the study of one particular thing.)