Coloring triangles in a Delaunay triangulation on the surface of a 3d sphere.












0














Suppose a delaunay triangulation over the surface of a 3d sphere (or generally some 3d surface of something topologically equivalent to the sphere). How many colors do I need to color its triangles so that triangles sharing an edge have different colors?



My idea: For the delaunay triangulation of a set of points on the plane, 3 colors are always enough.



Proof: taking the 1-ring (all the triangles that touch an epsilon small circle around a vertex) 3 colors are always enough to color it.



enter image description here



This is taken from wikipedia. The 4rth point from the bottom, (4rth in the sense of y coordinate) has a 1-ring of size 5, thus I need three colors to color it.



I think the argument still holds for the surface of a sphere. Am I correct?



Will it still hold even if there is genus?










share|cite|improve this question






















  • The small-ring argument would work for general maps, won't it? Even for a tertrahedron ...
    – Hagen von Eitzen
    Nov 23 at 20:10










  • I think yes. Even genus seems irrelevant. Seems a little suspicious, that is why I asked
    – Paramar
    Nov 23 at 20:12










  • The point being if it works for a tetrahedron, it must be wrong. You need four colors to color a tetrahedron.
    – WhatToDo
    Nov 23 at 20:48
















0














Suppose a delaunay triangulation over the surface of a 3d sphere (or generally some 3d surface of something topologically equivalent to the sphere). How many colors do I need to color its triangles so that triangles sharing an edge have different colors?



My idea: For the delaunay triangulation of a set of points on the plane, 3 colors are always enough.



Proof: taking the 1-ring (all the triangles that touch an epsilon small circle around a vertex) 3 colors are always enough to color it.



enter image description here



This is taken from wikipedia. The 4rth point from the bottom, (4rth in the sense of y coordinate) has a 1-ring of size 5, thus I need three colors to color it.



I think the argument still holds for the surface of a sphere. Am I correct?



Will it still hold even if there is genus?










share|cite|improve this question






















  • The small-ring argument would work for general maps, won't it? Even for a tertrahedron ...
    – Hagen von Eitzen
    Nov 23 at 20:10










  • I think yes. Even genus seems irrelevant. Seems a little suspicious, that is why I asked
    – Paramar
    Nov 23 at 20:12










  • The point being if it works for a tetrahedron, it must be wrong. You need four colors to color a tetrahedron.
    – WhatToDo
    Nov 23 at 20:48














0












0








0







Suppose a delaunay triangulation over the surface of a 3d sphere (or generally some 3d surface of something topologically equivalent to the sphere). How many colors do I need to color its triangles so that triangles sharing an edge have different colors?



My idea: For the delaunay triangulation of a set of points on the plane, 3 colors are always enough.



Proof: taking the 1-ring (all the triangles that touch an epsilon small circle around a vertex) 3 colors are always enough to color it.



enter image description here



This is taken from wikipedia. The 4rth point from the bottom, (4rth in the sense of y coordinate) has a 1-ring of size 5, thus I need three colors to color it.



I think the argument still holds for the surface of a sphere. Am I correct?



Will it still hold even if there is genus?










share|cite|improve this question













Suppose a delaunay triangulation over the surface of a 3d sphere (or generally some 3d surface of something topologically equivalent to the sphere). How many colors do I need to color its triangles so that triangles sharing an edge have different colors?



My idea: For the delaunay triangulation of a set of points on the plane, 3 colors are always enough.



Proof: taking the 1-ring (all the triangles that touch an epsilon small circle around a vertex) 3 colors are always enough to color it.



enter image description here



This is taken from wikipedia. The 4rth point from the bottom, (4rth in the sense of y coordinate) has a 1-ring of size 5, thus I need three colors to color it.



I think the argument still holds for the surface of a sphere. Am I correct?



Will it still hold even if there is genus?







general-topology graph-theory coloring triangulation






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 23 at 20:07









Paramar

257111




257111












  • The small-ring argument would work for general maps, won't it? Even for a tertrahedron ...
    – Hagen von Eitzen
    Nov 23 at 20:10










  • I think yes. Even genus seems irrelevant. Seems a little suspicious, that is why I asked
    – Paramar
    Nov 23 at 20:12










  • The point being if it works for a tetrahedron, it must be wrong. You need four colors to color a tetrahedron.
    – WhatToDo
    Nov 23 at 20:48


















  • The small-ring argument would work for general maps, won't it? Even for a tertrahedron ...
    – Hagen von Eitzen
    Nov 23 at 20:10










  • I think yes. Even genus seems irrelevant. Seems a little suspicious, that is why I asked
    – Paramar
    Nov 23 at 20:12










  • The point being if it works for a tetrahedron, it must be wrong. You need four colors to color a tetrahedron.
    – WhatToDo
    Nov 23 at 20:48
















The small-ring argument would work for general maps, won't it? Even for a tertrahedron ...
– Hagen von Eitzen
Nov 23 at 20:10




The small-ring argument would work for general maps, won't it? Even for a tertrahedron ...
– Hagen von Eitzen
Nov 23 at 20:10












I think yes. Even genus seems irrelevant. Seems a little suspicious, that is why I asked
– Paramar
Nov 23 at 20:12




I think yes. Even genus seems irrelevant. Seems a little suspicious, that is why I asked
– Paramar
Nov 23 at 20:12












The point being if it works for a tetrahedron, it must be wrong. You need four colors to color a tetrahedron.
– WhatToDo
Nov 23 at 20:48




The point being if it works for a tetrahedron, it must be wrong. You need four colors to color a tetrahedron.
– WhatToDo
Nov 23 at 20:48















active

oldest

votes











Your Answer





StackExchange.ifUsing("editor", function () {
return StackExchange.using("mathjaxEditing", function () {
StackExchange.MarkdownEditor.creationCallbacks.add(function (editor, postfix) {
StackExchange.mathjaxEditing.prepareWmdForMathJax(editor, postfix, [["$", "$"], ["\\(","\\)"]]);
});
});
}, "mathjax-editing");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "69"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
noCode: true, onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});


}
});














draft saved

draft discarded


















StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3010778%2fcoloring-triangles-in-a-delaunay-triangulation-on-the-surface-of-a-3d-sphere%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown






























active

oldest

votes













active

oldest

votes









active

oldest

votes






active

oldest

votes
















draft saved

draft discarded




















































Thanks for contributing an answer to Mathematics Stack Exchange!


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


Use MathJax to format equations. MathJax reference.


To learn more, see our tips on writing great answers.





Some of your past answers have not been well-received, and you're in danger of being blocked from answering.


Please pay close attention to the following guidance:


  • Please be sure to answer the question. Provide details and share your research!

But avoid



  • Asking for help, clarification, or responding to other answers.

  • Making statements based on opinion; back them up with references or personal experience.


To learn more, see our tips on writing great answers.




draft saved


draft discarded














StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f3010778%2fcoloring-triangles-in-a-delaunay-triangulation-on-the-surface-of-a-3d-sphere%23new-answer', 'question_page');
}
);

Post as a guest















Required, but never shown





















































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown

































Required, but never shown














Required, but never shown












Required, but never shown







Required, but never shown







Popular posts from this blog

Plaza Victoria

Puebla de Zaragoza

Musa