<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">APM</journal-id><journal-title-group><journal-title>Advances in Pure Mathematics</journal-title></journal-title-group><issn pub-type="epub">2160-0368</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/apm.2012.26055</article-id><article-id pub-id-type="publisher-id">APM-24365</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Physics&amp;Mathematics</subject></subj-group></article-categories><title-group><article-title>
 
 
  Necessary Conditions for a Fixed Point of Maps in Non-Metric Spaces
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>.</surname><given-names>Raykov</given-names></name><xref ref-type="aff" rid="aff1"><sub>1</sub></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib></contrib-group><aff id="aff1"><label>1</label><addr-line>Department of Mathematics and Physics, Colorado State University, Pueblo, USA</addr-line></aff><author-notes><corresp id="cor1">* E-mail:<email>ivan.raykov@colostate-pueblo.edu</email></corresp></author-notes><pub-date pub-type="epub"><day>09</day><month>11</month><year>2012</year></pub-date><volume>02</volume><issue>06</issue><fpage>371</fpage><lpage>372</lpage><history><date date-type="received"><day>July</day>	<month>17,</month>	<year>2012</year></date><date date-type="rev-recd"><day>September</day>	<month>3,</month>	<year>2012</year>	</date><date date-type="accepted"><day>September</day>	<month>11,</month>	<year>2012</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
 
 
  The main purpose of the present work is to introduce necessary conditions for a map on a non-metric space, defined by using a map on a metric space, to have a fixed point.
 
</p></abstract><kwd-group><kwd>Topological Space; Complete Metric Compact Space; Cauchy Sequence; Lipschitz Continuous Map; Contraction Map</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>Let X denote a complete (or compact) metric space and also <img src="3-5300241\d7010410-57d1-491c-875a-433e8449c027.jpg" /> a continuous map of X onto Y, where Y is a bounded closed topological normal space with a countable base.</p><p>What must be the conditions, in the means of the meric space X, such that the continuous map <img src="3-5300241\928f8d3d-a8f5-4ec3-867a-564b0ea1758b.jpg" /> from Y onto Y will have a fixed point?</p><p>We suppose that (see [1-3]):</p><p>the continuous map <img src="3-5300241\0738a443-e409-4b9d-be7b-8103005fdd58.jpg" /> (not one to one) and the continuous map <img src="3-5300241\6b5b153d-6abe-4147-b1e4-d06dc5b56787.jpg" /> are given and the continuous inverse map of f, <img src="3-5300241\e86b5c89-fe46-4356-9f2f-bd18e70e5dcc.jpg" />exists.</p><p><img src="3-5300241\ba19c5a2-83ce-4549-8bbd-e23f9fb90209.jpg" /></p><p>We remind that Banach contraction principle for multivalued maps is valid and also the next Theorem, proved by H. Covitz and S. B. Nadler Jr. (see [<xref ref-type="bibr" rid="scirp.24365-ref4">4</xref>]).</p><p>Theorem 1. Let <img src="3-5300241\b437c578-1c95-469e-9226-9dc3322b0a54.jpg" /> be a complete metric space and <img src="3-5300241\af47bde1-50b7-4dd2-8b9f-8470d7982b95.jpg" /> a conraction map (<img src="3-5300241\9e938af2-cd35-4e42-8301-0ee0df1f25bb.jpg" />denotes the family of all nonempty closed bounded (compact) subsets of X). Then there exists <img src="3-5300241\a81dd806-f9da-478c-a0f8-3bda1e3c23e4.jpg" /> such that<img src="3-5300241\0108f7f8-8610-47d6-827b-03631cbd6a2b.jpg" />.</p></sec><sec id="s2"><title>2. Main Result</title><p>We consider now the next theorem:</p><p>Theorem 2. Let <img src="3-5300241\c213dbc8-1dc7-4fad-9e50-bee3ff37e8a2.jpg" /> denote a complete (or compact) metric space <img src="3-5300241\31624c8f-141f-4a61-8d7b-23833d2695a2.jpg" /> and also:</p><p><img src="3-5300241\fffc72aa-e39a-42dc-b0a5-e6101f171f6a.jpg" />a continuous map of <img src="3-5300241\ee894d72-16b2-4e27-8d5b-a7f08c376186.jpg" /> onto<img src="3-5300241\9e7209e5-29c6-4852-bd49-69903f3caf7b.jpg" />, where <img src="3-5300241\671c40c7-012f-4e87-8612-ae42d0f62fa0.jpg" /> is a bounded closed topological normal space with a countable base.</p><p>We suppose also that the maps:</p><p><img src="3-5300241\36f96b26-86a9-4d13-baf8-9ac77f38a4d3.jpg" />is continuous and onto.</p><p>and</p><p><img src="3-5300241\07d2eec6-d6be-42db-9b6b-0fc4c6caa5e1.jpg" />exists and it is continuous.</p><p>If <img src="3-5300241\0a5ae84a-4238-4b30-9093-e44e4a90a487.jpg" /> is a point from <img src="3-5300241\973f12ba-c570-4a36-9d3e-0b1f1b2c29ed.jpg" /> and if we suppose also that<img src="3-5300241\d077ae0a-90c6-4c5a-bf00-ea35f11ebcec.jpg" />.</p><p>Then if the rest terms of the sequence <img src="3-5300241\9b9629d5-12ec-4bf1-bce2-040fc0c60b4a.jpg" /> are received from <img src="3-5300241\f8e9f041-1d1c-4ccd-a493-8cff65dee2fb.jpg" /> and the rest of the terms of the sequence <img src="3-5300241\f518e9b7-df75-4392-8975-54264c9e3942.jpg" /> are determined by <img src="3-5300241\5e524052-2a7d-4c8f-9ca0-1288838957c6.jpg" /> and if also <img src="3-5300241\d685c8f0-71d9-44f6-abba-8e7d20af1ea9.jpg" /> is a Cauchy sequence and therefore convergent to a fixed point <img src="3-5300241\f3bce552-1bce-46c4-b26d-8174d5fe0901.jpg" /> in<img src="3-5300241\1c041bbc-e4ff-4671-b8ef-d51bb14d2cd8.jpg" />, then the sequence <img src="3-5300241\42cb311b-163b-4361-8c49-fbcdf6a6d3d3.jpg" /> will be also convergent to a fixed point <img src="3-5300241\98d82285-1248-4c90-a4bf-7ed9a55adb61.jpg" /> in<img src="3-5300241\35e81ca1-323b-470c-9d3b-cdb699c88c97.jpg" />.</p><p>Proof. Let <img src="3-5300241\aa4c4b71-e6a6-4113-bf5e-87eb1e06879a.jpg" /> is a point from <img src="3-5300241\f93bdaf9-2841-4ac6-a3a6-64244fd62d7b.jpg" /> and let us suppose also that <img src="3-5300241\f3d144e0-d89d-4590-9396-ee2d44ec04af.jpg" /> and let the rest terms of the sequence <img src="3-5300241\737628ec-9cac-43f6-8e20-339ebfc4bdc8.jpg" /> are received from <img src="3-5300241\acfa9fa5-b7fa-4818-942d-34a732224bc7.jpg" /> <img src="3-5300241\6e73676b-72fb-4ea7-b377-e72c5519d987.jpg" />.</p><p>Let also the rest of the terms of the sequence <img src="3-5300241\0b9cc51d-074c-4f4d-93c8-72ac437c2a22.jpg" /> are determined by <img src="3-5300241\41522d48-3544-4c8b-9a3e-20d0e410e0ee.jpg" /> <img src="3-5300241\17eab5dd-6b99-4ade-a2c7-469af96d1580.jpg" />.</p><p>If <img src="3-5300241\b327aae0-ee5f-4d3a-8ca2-5af1fd3e1cc9.jpg" /> is a Cauchy sequence then for any <img src="3-5300241\51c2e57d-34a8-49df-8ea5-09eecec774b1.jpg" /> there exists an integer<img src="3-5300241\199f0e49-91fc-4097-b83e-dec12ce75f01.jpg" />, such that for all integers i and k, <img src="3-5300241\588b717f-02bf-4fd3-9599-a797096b2635.jpg" />and <img src="3-5300241\e99d7cd8-d6ce-43a1-808d-2f80841179e0.jpg" /> will be satisfied the inequality</p><p><img src="3-5300241\bb2f937b-e988-4bd1-b04e-8c573d31670f.jpg" /></p><p>and therefore the Cauchy sequence <img src="3-5300241\70b89acd-e0be-4e88-8b47-913a722e5552.jpg" /> will be convergent with a fixed point <img src="3-5300241\373dc459-aa65-4972-af27-6a9fb04606d6.jpg" /> in X, and because X is complete (or compact), i.e.</p><p><img src="3-5300241\88322063-6f41-4bee-9286-2d2494b6651e.jpg" /></p><p>Since <img src="3-5300241\bbc39858-08a2-481b-88a1-f73a5f3939ba.jpg" /> and <img src="3-5300241\9d7a7c0c-d8e0-480f-a35d-115913969d58.jpg" /> and <img src="3-5300241\462b36cc-7f13-4840-a963-aa2236a3c09f.jpg" /> is a continuous map and <img src="3-5300241\0bf30b3a-fb10-497d-9933-5ea85a82243b.jpg" /> is continuous map onto the closed and bounded space<img src="3-5300241\35c7b4fa-f1fd-43e2-ac5f-0a8dfe1d6823.jpg" />, and also <img src="3-5300241\9ec243e5-f760-4db2-8899-35231e82fed5.jpg" /> and<img src="3-5300241\7d0a3000-fe9d-46fe-9913-02cd0b69f087.jpg" />, therefore the sequence <img src="3-5300241\e1d30123-c919-489f-a29f-8418e2bd98f4.jpg" /> will be also convergent with a fixed point <img src="3-5300241\ecc2737c-a170-4fbe-b356-a1f35d23f85e.jpg" /> in<img src="3-5300241\7804e83b-90c9-42c7-ae36-0073e5c06f7b.jpg" />, such that <img src="3-5300241\01d3fcd1-f5e4-4f3a-888e-f203ca6ea27f.jpg" /> and<img src="3-5300241\23615f16-fad7-4520-9845-6d6b386b520e.jpg" />, i.e.</p><p><img src="3-5300241\29240c5c-9c6d-4b04-bead-82bbdf9c0f7b.jpg" /></p><p>Q.E.D.</p></sec><sec id="s3"><title>3. Acknowledgements</title><p>We express our gratitude to Professor Alexander Arhangelskii from OU-Athens for creating the problem and to Professor Jonathan Poritz and Professor Frank Zizza from CSU-Pueblo for the precious help for solving this problem, and to Professor Darren Funk-Neubauer and Professor Bruce Lundberg for correcting some grammatical and spelling errors.</p></sec><sec id="s4"><title>REFERENCES</title></sec></body><back><ref-list><title>References</title><ref id="scirp.24365-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">A. V. Arhangel’skii and V. V. Fedorchuk, “The Basic Concepts and Constructions of General Topology,” In: A. V. Arkhangel’skii and L. S. Pontrjagin, Eds., General Topology I, Encyclopedia of the Mathematical Sciences, Springer, Berlin, 1990.</mixed-citation></ref><ref id="scirp.24365-ref2"><label>2</label><mixed-citation publication-type="other" xlink:type="simple">J. 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