Discrete Mathematics

All posts under tag "Discrete Mathematics"

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Nordhaus-Gaddum for Treewidth

Nordhaus-Gaddum for Treewidth

: ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ๋…ธ๋“œ ๊ฐ€๋“œ๋‹ด ์œ ํ˜• ์ •๋ฆฌ๋ฅผ ์‚ฌ์šฉํ•˜์—ฌ ํŠธ๋ฆฌ ๋„ˆ๋น„(treewidth)์— ๋Œ€ํ•œ ์ƒˆ๋กœ์šด ๊ด€์ ์„ ์ œ์‹œํ•˜๊ณ  ์žˆ์Šต๋‹ˆ๋‹ค. ์ด๋Š” ํŠนํžˆ ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ๋งค๊ฐœ๋ณ€์ˆ˜๋กœ, ๊ทธ๋ž˜ํ”„์˜ ๋ณต์žก์„ฑ์„ ์ธก์ •ํ•˜๋Š” ๋ฐ ํ™œ์šฉ๋ฉ๋‹ˆ๋‹ค. ํŠธ๋ฆฌ ๋„ˆ๋น„์™€ ๊ทธ ์˜๋ฏธ: ํŠธ๋ฆฌ ๋„ˆ๋น„๋Š” ๊ทธ๋ž˜ํ”„ G๋ฅผ ๋ถ€๋ถ„ ๊ทธ๋ž˜ํ”„๋กœ ํฌํ•จํ•  ์ˆ˜ ์žˆ๋Š” k ํŠธ๋ฆฌ(k tree)์˜ ์ตœ์†Œ ์ •์ˆ˜ k๋ฅผ ๋‚˜ํƒ€๋ƒ…๋‹ˆ๋‹ค. ์ด๋Š” ํŠธ๋ฆฌ ๋ถ„ํ•ด(tree decomposition)๋ฅผ ํ†ตํ•ด ์ •์˜๋˜๋ฉฐ, ๊ทธ๋ž˜ํ”„์˜ ๋ณต์žก์„ฑ์„ ์ธก์ •ํ•˜๋Š” ๋ฐ ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•ฉ๋‹ˆ๋‹ค. ๋…ธ๋“œ ๊ฐ€๋“œ๋‹ด ์œ ํ˜• ์ •๋ฆฌ์™€ ํŠธ๋ฆฌ ๋„ˆ๋น„: ๋ณธ ๋…ผ๋ฌธ์—์„œ ์ œ์‹œ๋œ ๋…ธ๋“œ ๊ฐ€๋“œ๋‹ด

Mathematics Computer Science Discrete Mathematics
Verifying Sierpinski and Riesel Numbers in ACL2

Verifying Sierpinski and Riesel Numbers in ACL2

์ด ๋…ผ๋ฌธ์€ ์‹œ๋ฅดํ”ผ๋‹ˆ(Sierpiล„ski) ์ˆ˜์™€ ๋ ˆ์ ค(Riesel) ์ˆ˜์— ๋Œ€ํ•œ ์‹ฌ๋„ ์žˆ๋Š” ๋ถ„์„๊ณผ ACL2๋ผ๋Š” ์ปดํ“จํ„ฐ ์ฆ๋ช… ๋„๊ตฌ๋ฅผ ํ™œ์šฉํ•œ ๊ทธ๋“ค์˜ ์„ฑ์งˆ ๊ฒ€์ฆ ๋ฐฉ๋ฒ•์„ ๋‹ค๋ฃน๋‹ˆ๋‹ค. ์ด๋“ค ์ˆ˜๋Š” ํŠน์ • ์–‘์˜ ํ™€์ˆ˜ ์ •์ˆ˜๊ฐ€ ๋ฌดํ•œ ๋ฆฌ์ŠคํŠธ์—์„œ ์†Œ์ˆ˜๊ฐ€ ๋ฐœ๊ฒฌ๋˜์ง€ ์•Š๋Š” ๊ฒฝ์šฐ์— ํ•ด๋‹นํ•˜๋ฉฐ, ์ด๋ฅผ ํ†ตํ•ด ์ˆ˜ํ•™์ ์œผ๋กœ ์ค‘์š”ํ•œ ์œ„์น˜๋ฅผ ์ฐจ์ง€ํ•˜๊ณ  ์žˆ์Šต๋‹ˆ๋‹ค. ์‹œ๋ฅดํ”ผ๋‹ˆ์™€ ๋ ˆ์ ค ์ˆ˜์˜ ๊ฐœ๋… ์‹œ๋ฅดํ”ผ๋‹ˆ ์ˆ˜์™€ ๋ ˆ์ ค ์ˆ˜๋Š” ๊ฐ๊ฐ k โ€ข 2^n + 1๊ณผ k โ€ข 2^n 1 ํ˜•ํƒœ์˜ ๋ฌดํ•œ ๋ฆฌ์ŠคํŠธ์—์„œ ์†Œ์ˆ˜๊ฐ€ ๋ฐœ๊ฒฌ๋˜์ง€ ์•Š๋Š” ์–‘์˜ ํ™€์ˆ˜ ์ •์ˆ˜์ž…๋‹ˆ๋‹ค. ์ด๋“ค ์ˆ˜๋ฅผ ์‹๋ณ„ํ•˜๋Š” ๊ฒƒ์€ ์–ด๋ ต์ง€๋งŒ, ํŠน์ • ์กฐ๊ฑด์„ ๋งŒ์กฑํ•˜๋ฉด

Computer Science Discrete Mathematics Logic
On the Intersection of All Critical Sets of a Unicyclic Graph

On the Intersection of All Critical Sets of a Unicyclic Graph

: ๋ณธ ๋…ผ๋ฌธ์€ ์œ ์‚ฌ์ดํด์  ๊ทธ๋ž˜ํ”„, ์ฆ‰ ๋‹จ์ผ ์‚ฌ์ดํด์„ ๊ฐ–๋Š” ์—ฐ๊ฒฐ ๊ทธ๋ž˜ํ”„์—์„œ ํ•ต์‹ฌ(core), ์ฝ”๋กœ๋‚˜(corona), ๊ทธ๋ฆฌ๊ณ  ker(G) ์ง‘ํ•ฉ๋“ค ๊ฐ„์˜ ๊ด€๊ณ„์— ๋Œ€ํ•ด ๊นŠ์ด ์žˆ๋Š” ๋ถ„์„์„ ์ œ๊ณตํ•œ๋‹ค. ์ด๋Ÿฌํ•œ ๊ทธ๋ž˜ํ”„๋“ค์€ ์ด๋ก ์ ์œผ๋กœ ์ค‘์š”ํ•œ ์œ„์น˜๋ฅผ ์ฐจ์ง€ํ•˜๋ฉฐ, ํŠนํžˆ ๊ทธ๋“ค์˜ ๋…๋ฆฝ ์ง‘ํ•ฉ๊ณผ ๋งค์นญ์— ๋Œ€ํ•œ ์„ฑ์งˆ์€ ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ํ•ต์‹ฌ์ ์ธ ์—ญํ• ์„ ํ•œ๋‹ค. ๋…ผ๋ฌธ์—์„œ๋Š” ๋จผ์ € ํ•ต์‹ฌ(core)๊ณผ ์ฝ”๋กœ๋‚˜(corona)์˜ ์ •์˜๋ฅผ ์ œ์‹œํ•œ๋‹ค. ํ•ต์‹ฌ์€ ๋ชจ๋“  ์ตœ๋Œ€ ๋…๋ฆฝ ์ง‘ํ•ฉ๋“ค์˜ ๊ต์ง‘ํ•ฉ์ด๊ณ , ์ฝ”๋กœ๋‚˜๋Š” ์ด๋Ÿฌํ•œ ์ง‘ํ•ฉ๋“ค์˜ ํ•ฉ์ง‘ํ•ฉ์ด๋‹ค. ker(G)๋Š” G์˜ ์ค‘์š”ํ•œ ๋…๋ฆฝ ์ง‘ํ•ฉ๋“ค์˜ ๊ต์ง‘ํ•ฉ์œผ๋กœ ์ •

Mathematics Computer Science Discrete Mathematics
The complexity of tangent words

The complexity of tangent words

์ด ๋…ผ๋ฌธ์€ ๋งค๋„๋Ÿฌ์šด ๊ณก์„ ๊ณผ ๊ทธ์— ๋Œ€ํ•œ ์ ‘์„  ๋‹จ์–ด์˜ ์–ธ์–ด์  ์ ‘๊ทผ๋ฒ•์„ ์ฒด๊ณ„์ ์œผ๋กœ ๋ถ„์„ํ•œ๋‹ค. ์ฃผ์š” ๋‚ด์šฉ์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค: 1. ๋งค๋„๋Ÿฌ์šด ๊ณก์„ ์˜ ์ •์˜์™€ ํŠน์„ฑ : ๋งค๋„๋Ÿฌ์šด ๊ณก์„ ์€ ์‹ค์ˆ˜ ์ง์„  ์œ„์˜ ์ปดํŒฉํŠธ ๊ตฌ๊ฐ„ I์—์„œ ์ •์˜๋˜๋ฉฐ, ๋ชจ๋“  t โˆˆ I ์— ๋Œ€ํ•ด ||ฮณโ€ฒ(t)|| > 0 ์ด๋ผ๋Š” ๊ทœ์น™์„ฑ์„ ๋งŒ์กฑํ•œ๋‹ค. ์ด๋Ÿฌํ•œ ๊ณก์„ ์€ ์›ํ•˜๋Š” ๋งŒํผ ์žฌ๋งค๊ฐœ๋ณ€์ˆ˜ํ™”๋  ์ˆ˜ ์žˆ์œผ๋ฉฐ, ์ผ๋ฐ˜์ ์œผ๋กœ ๊ฐ t ์— ๋Œ€ํ•ด ||ฮณโ€ฒ(t)|| 1 ์ด๋‹ค. ๋งค๋„๋Ÿฌ์šด ๊ณก์„ ์˜ ๊ทผ์‚ฌ ๋ฐฉ๋ฒ•์œผ๋กœ ํ‰๋ฉด์— ๊ฒฉ์ž๋ง์„ ๊ทธ๋ ค์„œ ๊ณก์„ ์ด ๋งŒ๋‚˜๋Š” ์‚ฌ๊ฐํ˜•์˜ ์ˆœ์„œ๋ฅผ ์‚ดํŽด๋ณธ๋‹ค. ์ด ์ ˆ๋‹จ ์ˆœ์„œ๋Š” ์ƒ, ํ•˜, ์ขŒ, ์šฐ ๋ฐฉํ–ฅ์œผ

Formal Languages Computational Geometry Computer Science Discrete Mathematics
Integral Value Transformations: A Class of Discrete Dynamical Systems

Integral Value Transformations: A Class of Discrete Dynamical Systems

์ด ๋…ผ๋ฌธ์€ Integral Value Transformations (IVTs)๋ฅผ ์ค‘์‹ฌ์œผ๋กœ ์ด์งˆ์  ๋™์—ญํ•™ ์‹œ์Šคํ…œ๊ณผ ๊ทธ ์•ˆ์ •์„ฑ์— ๋Œ€ํ•œ ๊นŠ์ด ์žˆ๋Š” ๋ถ„์„์„ ์ œ๊ณตํ•ฉ๋‹ˆ๋‹ค. IVT๋Š” Sk. S. Hassan ์™ธ ์—ฐ๊ตฌ์ž๋“ค์— ์˜ํ•ด ์†Œ๊ฐœ๋˜์—ˆ์œผ๋ฉฐ, p adic ์‹œ์Šคํ…œ์—์„œ Collatz ์œ ์‚ฌ ํ•จ์ˆ˜์™€ ๊ด€๋ จ์ด ์žˆ์Šต๋‹ˆ๋‹ค. ์ด๋Ÿฌํ•œ ๋ณ€ํ™˜์€ ์…€๋ฃฐ๋Ÿฌ ์˜คํ† ๋งˆํƒ€์™€ ์œ ์‚ฌํ•œ ๋ฐฉ์‹์œผ๋กœ ์—ฐ๊ตฌ๋˜์–ด ์™”์Šต๋‹ˆ๋‹ค. ๋™์—ญํ•™ ์‹œ์Šคํ…œ์˜ ์ •์˜ ๋ฐ ๋ถ„์„ ๋…ผ๋ฌธ์—์„œ๋Š” IVTs๊ฐ€ ๋ฐ˜๋ณต์ ์œผ๋กœ ์ ์šฉ๋  ๋•Œ ํ˜•์„ฑ๋˜๋Š” ์ด์งˆ์  ๋™์—ญํ•™ ์‹œ์Šคํ…œ์„ ํƒ๊ตฌํ•ฉ๋‹ˆ๋‹ค. ์ด๋Ÿฌํ•œ ํ•จ์ˆ˜๋“ค์ด ์‹œ๊ฐ„์— ๋”ฐ๋ผ ์–ด๋–ป๊ฒŒ ์ง„ํ™”ํ•˜๊ณ  ํ˜ผ๋ž€์Šค๋Ÿฌ์šด

System Mathematics Computer Science Discrete Mathematics
A Reformulation of the Arora-Rao-Vazirani Structure Theorem

A Reformulation of the Arora-Rao-Vazirani Structure Theorem

๋งค๋ ฅ์ ์ธ ํ•œ๊ธ€ ์ œ๋ชฉ: ์•„๋กœ๋ผ ๋ผ์˜ค ๋ฐ”์ง€๋ผ๋‹ˆ ๊ตฌ์กฐ ์ •๋ฆฌ์˜ ๊ทธ๋ž˜ํ”„ ์ด๋ก ์  ์žฌํ•ด์„ ์ดˆ๋ก ์ „์ฒด ๋ฒˆ์—ญ ๋ฐ ์ •๋ฆฌ: ๋ณธ ๋…ผ๋ฌธ์€ ์•„๋กœ๋ผ, ๋ผ์˜ค, ๋ฐ”์ง€๋ผ๋‹ˆ(ARV)๊ฐ€ ์ฆ๋ช…ํ•œ ๊ตฌ์กฐ ์ •๋ฆฌ๋ฅผ ํ™•์žฅ๋œ ๊ทธ๋ž˜ํ”„ ๊ฐœ๋…์œผ๋กœ ์žฌํ•ด์„ํ•ฉ๋‹ˆ๋‹ค. ARV๋Š” ๊ท ํ˜• ๋ถ„๋ฆฌ ๋ฌธ์ œ์™€ ๊ท ์ผ ๊ฐ€์žฅ ํฌ๋ฐ• ์ ˆ๋‹จ ๋ฌธ์ œ์— ๋Œ€ํ•ด O(โˆšlog n) ๊ทผ์‚ฌ์น˜๋ฅผ ๋„์ถœํ–ˆ์Šต๋‹ˆ๋‹ค. ๊ทธ๋“ค์˜ ๊ฒฐ๊ณผ๋Š” ์‚ผ๊ฐ ๋ถ€๋“ฑ์‹์„ ๋งŒ์กฑํ•˜๋Š” ์  ์ง‘ํ•ฉ์˜ ๊ธฐํ•˜ํ•™์  ์ง„์ˆ ์— ๊ธฐ๋ฐ˜ํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ์ดํ›„ ๊ทผ์‚ฌ ์•Œ๊ณ ๋ฆฌ์ฆ˜๊ณผ ๋ฉ”ํŠธ๋ฆญ ์ž„๋ฒ ๋”ฉ ์—ฐ๊ตฌ์˜ ํ† ๋Œ€๊ฐ€ ๋˜์—ˆ์Šต๋‹ˆ๋‹ค. ๋ณธ ๋…ผ๋ฌธ์—์„œ๋Š” ARV ๊ตฌ์กฐ ์ •๋ฆฌ๋ฅผ ํ™•์žฅ๋œ ๊ทธ๋ž˜ํ”„ GV,ฯต์—์„œ ํฐ ์ง‘ํ•ฉ์˜ ํ™•์žฅ ๊ฐœ๋…์œผ

Computer Science Discrete Mathematics
Convex Polyhedra Realizing Given Face Areas

Convex Polyhedra Realizing Given Face Areas

: ์ด ๋…ผ๋ฌธ์€ 3์ฐจ์› ๊ณต๊ฐ„์—์„œ ํŠน์ • ๋ฉด์ ์ด ์ฃผ์–ด์กŒ์„ ๋•Œ, ์ด ๋ฉด์ ์ด ๋‹ค๊ฐํ˜•์˜ ๊ฐ ๋ฉด์˜ ๋ฉด์ ์„ ๋‚˜ํƒ€๋‚ด๋Š” ์กฐ๊ฑด์— ๋Œ€ํ•ด ๊นŠ๊ฒŒ ํƒ๊ตฌํ•˜๊ณ  ์žˆ์Šต๋‹ˆ๋‹ค. ํŠนํžˆ, Aโ‚ โ‰ค i > 1 Aแตข์ธ ๊ฒฝ์šฐ, ์ด ๋ฒกํ„ฐ๋กœ ๊ตฌ์„ฑ๋œ ๋‹ค๊ฐํ˜•์ด ์กด์žฌํ•œ๋‹ค๋Š” ๊ฒƒ์„ ์ฆ๋ช…ํ•ฉ๋‹ˆ๋‹ค. ์ฃผ์š” ๊ฐœ๋…๊ณผ ์ •๋ฆฌ Minkowski์˜ ์ •๋ฆฌ : Minkowski์˜ ์ •๋ฆฌ๋Š” ์ฃผ์–ด์ง„ ๋ฉด์ ๊ณผ ๋‹จ์œ„ ๋ฒ•์„  ๋ฒกํ„ฐ๋ฅผ ํ†ตํ•ด ๊ณ ์œ ํ•œ ๋‹ซํžŒ ๋‹ค๊ฐํ˜•์„ ํ˜•์„ฑํ•  ์ˆ˜ ์žˆ๋Š” ์กฐ๊ฑด์„ ์ œ๊ณตํ•ฉ๋‹ˆ๋‹ค. ์ด ๋…ผ๋ฌธ์—์„œ๋Š” ์ด๋ฅผ '์™„์ „ํžˆ ๊ท ํ˜• ์žกํžŒ' ๋ฒกํ„ฐ๋กœ ์žฌํ•ด์„ํ•˜์—ฌ, ๊ฐ ๋ฉด์˜ ๋ฉด์ ์ด ์ฃผ์–ด์กŒ์„ ๋•Œ, ๊ทธ ๋ฉด์ ์„ ๊ฐ€์ง„ ๋‹ค๊ฐํ˜•์ด ์กด์žฌํ•˜๋Š”์ง€ ํŒ๋‹จํ• 

Computer Science Discrete Mathematics
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Recovery of a Sparse Integer Solution to an Underdetermined System of Linear Equations

๋ณธ ๋…ผ๋ฌธ์€ ์Šค๋งˆํŠธ ๊ทธ๋ฆฌ๋“œ์—์„œ ๋ฐœ์ƒํ•˜๋Š” ์ด์ง„ ํ•ด ๋ณต์› ๋ฌธ์ œ๋ฅผ ๋‹ค๋ฃจ๋ฉฐ, ํŠนํžˆ m < n ์ธ ๊ฒฝ์šฐ ๋ฌดํ•œํ•œ ์‹ค์ˆ˜ ํ•ด์™€ ์—ฌ๋Ÿฌ ์ด์ง„ ํ•ด๊ฐ€ ์กด์žฌํ•  ์ˆ˜ ์žˆ๋Š” ์ƒํ™ฉ์„ ๊ณ ๋ คํ•ฉ๋‹ˆ๋‹ค. ์ด๋Ÿฌํ•œ ๋ฌธ์ œ๋Š” NP ํ•˜๋“œ๋กœ ์•Œ๋ ค์ ธ ์žˆ์œผ๋ฉฐ, ์ด๋ฅผ ํ•ด๊ฒฐํ•˜๊ธฐ ์œ„ํ•ด Mangasarian ๋“ฑ์ด ์ œ์•ˆํ•œ ๋ฐฉ๋ฒ•๋ก ์„ ๊ธฐ๋ฐ˜์œผ๋กœ ์—ฐ๊ตฌ๋ฅผ ์ง„ํ–‰ํ•˜๊ณ  ์žˆ์Šต๋‹ˆ๋‹ค. 1. ๋ฌธ์ œ์˜ ๋ฐฐ๊ฒฝ๊ณผ ์ค‘์š”์„ฑ ๋…ผ๋ฌธ์€ ์Šค๋งˆํŠธ ๊ทธ๋ฆฌ๋“œ์—์„œ ๋ฐœ์ƒํ•˜๋Š” ์ด์ง„ ํ•ด ๋ณต์› ๋ฌธ์ œ์— ๋Œ€ํ•ด ๋‹ค๋ฃน๋‹ˆ๋‹ค. ๊ฐ ๊ณ ๊ฐ ๊ฐ€๊ตฌ๋Š” ์ €์ „์•• ๋ณ€์••๊ธฐ์˜ ์„ธ ๊ฐ€์ง€ ์ „์œ„ ์ค‘ ํ•˜๋‚˜์— ์—ฐ๊ฒฐ๋˜์–ด ์žˆ์œผ๋ฉฐ, ์ด๋ฅผ ์ถ”์ถœํ•˜๊ธฐ ์œ„ํ•ด A ํ–‰๋ ฌ์„ ์‚ฌ์šฉํ•ฉ๋‹ˆ๋‹ค. ์—ฌ๊ธฐ์„œ A ์˜ ์—ด

Information Theory Machine Learning Computer Science System Discrete Mathematics Mathematics
A note on triangle-free graphs

A note on triangle-free graphs

: ๋ณธ ๋…ผ๋ฌธ์€ ์‚ผ๊ฐ ๋ฌด๋ณ€ ๊ทธ๋ž˜ํ”„์˜ ์ด๋ก ์  ํƒ๊ตฌ๋ฅผ ์ค‘์‹ฌ์œผ๋กœ ์ง„ํ–‰๋˜๋ฉฐ, ํŠนํžˆ ์ด๋Ÿฌํ•œ ๊ทธ๋ž˜ํ”„๊ฐ€ ๊ฐ–๋Š” ํŠน์„ฑ๊ณผ ๊ทธ์— ๋”ฐ๋ฅธ ์—ฌ๋Ÿฌ ์กฐ๊ฑด๋“ค์„ ๋ถ„์„ํ•˜๊ณ  ์žˆ๋‹ค. ์‚ผ๊ฐ ๋ฌด๋ณ€ ๊ทธ๋ž˜ํ”„๋ž€ ๊ฐ„๋‹จํžˆ ๋งํ•ด ์‚ผ๊ฐํ˜•์„ ํฌํ•จํ•˜์ง€ ์•Š๋Š” ๊ทธ๋ž˜ํ”„๋ฅผ ์˜๋ฏธํ•˜๋ฉฐ, ์ด๋Š” ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ์—ฐ๊ตฌ ๋Œ€์ƒ ์ค‘ ํ•˜๋‚˜์ด๋‹ค. ๋…ผ๋ฌธ์˜ ์ดˆ๋ฐ˜๋ถ€์—์„œ๋Š” ๊ธฐ๋ณธ์ ์ธ ์šฉ์–ด์™€ ์ •์˜๊ฐ€ ์ œ์‹œ๋œ๋‹ค. ํŠนํžˆ, ์ •์ ๊ณผ ๊ฐ„์„ ์˜ ์ง‘ํ•ฉ, ์ฐจ์ˆ˜, ์ง€๋ฆ„ ๋“ฑ์˜ ๊ฐœ๋…์ด ์†Œ๊ฐœ๋˜๋ฉฐ, ์ด๋Ÿฌํ•œ ๊ธฐ์ดˆ์ ์ธ ์ •์˜๋“ค์€ ์ดํ›„ ๋…ผ์˜์— ์žˆ์–ด ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•œ๋‹ค. ๋˜ํ•œ, Cn๊ณผ Km,n์ด๋ผ๋Š” ํŠน๋ณ„ํ•œ ํ˜•ํƒœ์˜ ๊ทธ๋ž˜ํ”„๋“ค์ด ์–ธ๊ธ‰๋˜๋Š”๋ฐ, ์ด๋Š” ์‚ผ๊ฐ ๋ฌด๋ณ€

Computer Science Discrete Mathematics
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Monochromatic Progressions in Random Colorings

: 1. ๋ฐ˜๋”์™€๋ฅด๋ด ์ •๋ฆฌ์™€ W(k) ๋ฐ˜๋”์™€๋ฅด๋ด ์ •๋ฆฌ๋Š” ๋žจ์ง€ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ์œ„์น˜๋ฅผ ์ฐจ์ง€ํ•˜๋ฉฐ, ๋ชจ๋“  ์–‘์˜ ์ •์ˆ˜ k์— ๋Œ€ํ•ด W(k)๋ผ๋Š” ์ƒํ•œ์„ ์„ ์ œ์‹œํ•ฉ๋‹ˆ๋‹ค. ์ด๋Š” {1, 2, ..., W(k)}์˜ 2์ƒ‰ ๋ถ„๋ฅ˜์—์„œ kํ•ญ ์•„๋ ˆํŠธ๋ฆญ ์ง„ํ–‰์ด ๋ฐ˜๋“œ์‹œ ๋ชจ๋…ธํฌ๋กฌ์œผ๋กœ ๋‚˜ํƒ€๋‚œ๋‹ค๋Š” ๊ฒƒ์„ ์˜๋ฏธํ•ฉ๋‹ˆ๋‹ค. ๊ทธ๋Ÿฌ๋‚˜ W(k)์˜ ์ •ํ™•ํ•œ ๊ฐ’์€ k๊ฐ€ ์ž‘์„ ๋•Œ๋งŒ ์•Œ๋ ค์ ธ ์žˆ์œผ๋ฉฐ, k๊ฐ€ ์ปค์งˆ์ˆ˜๋ก ์ด ๊ฐ’์„ ๊ตฌํ•˜๋Š” ๊ฒƒ์ด ๋งค์šฐ ์–ด๋ ค์›Œ์ง‘๋‹ˆ๋‹ค. 2. ํ™•๋ฅ ์  ์ ‘๊ทผ: N+(k)์™€ N (k) N+(k)๋Š” {1, 2, ..., N+(k)}์˜ 2์ƒ‰ ๋ถ„๋ฅ˜์—์„œ kํ•ญ ์•„๋ ˆํŠธ๋ฆญ ์ง„ํ–‰์ด ํฌํ•จ๋  ํ™•๋ฅ ์ด

Computer Science Mathematics Discrete Mathematics
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A note on the paper 'Minimizing total tardiness on parallel machines with preemptions' by Kravchenko and Werner [2010]

: Kravchenko์™€ Werner์˜ ๋…ผ๋ฌธ์€ ๋ณ‘๋ ฌ ๋จธ์‹  ํ™˜๊ฒฝ์—์„œ ์ž‘์—…์˜ ์ด ์ง€์—ฐ ์‹œ๊ฐ„์„ ์ตœ์†Œํ™”ํ•˜๋Š” ๋ฌธ์ œ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๋ฅผ ๋‹ค๋ฃจ๊ณ  ์žˆ๋‹ค. ์ด๋“ค์€ 'ํŒŒํ‹ฐ์…˜' ๋ฌธ์ œ๋กœ๋ถ€ํ„ฐ ํŒŒ์ƒ๋œ ๋‘ ๊ฐ€์ง€ ๋ณต์žก๋„ ํด๋ž˜์Šค์ธ P |pmtn| T j์™€ P |r j , p j p, pmtn| T j์— ๋Œ€ํ•ด ๊ฐ์†Œ ๋ฐฉ๋ฒ•์„ ์ œ์‹œํ•˜์˜€์œผ๋ฉฐ, ํŠนํžˆ P |pmtn| T j์˜ ๊ฐ์†Œ ๋ฐฉ๋ฒ•์„ ์ƒ์„ธํžˆ ์„ค๋ช…ํ•˜์˜€๋‹ค. ์ด ๋…ผ๋ฌธ์€ ๋ณ‘๋ ฌ ๋จธ์‹  ํ™˜๊ฒฝ์—์„œ ์ž‘์—… ์Šค์ผ€์ค„๋ง ๋ฌธ์ œ๋ฅผ ํ•ด๊ฒฐํ•˜๋Š” ๋ฐ ์žˆ์–ด ์ค‘์š”ํ•œ ๊ธฐ์—ฌ๋ฅผ ํ•˜์˜€์ง€๋งŒ, ์ผ๋ถ€ ๋ถ€๋ถ„์— ๋Œ€ํ•œ ๋ถ„์„์ด ๋ถ€์กฑํ•˜๊ฑฐ๋‚˜ ์ž˜๋ชป๋˜์—ˆ์Œ์„ ๋ณด์—ฌ์ฃผ๊ณ  ์žˆ๋‹ค. ๋…ผ๋ฌธ์˜ ํ•ต์‹ฌ ๋‚ด

Computer Science Discrete Mathematics
On a property of the $n$-dimensional cube

On a property of the $n$-dimensional cube

๋ณธ ๋…ผ๋ฌธ์€ ๊ณ ์ฐจ์› ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ๋ฌธ์ œ ์ค‘ ํ•˜๋‚˜์ธ n์ฐจ์› ํ๋ธŒ์˜ ๋ถ€๋ถ„ ์ง‘ํ•ฉ์— ๋Œ€ํ•œ ์—ฐ๊ตฌ๋ฅผ ์ˆ˜ํ–‰ํ•˜๊ณ  ์žˆ๋‹ค. ํŠนํžˆ, n โ‰ฅ 4์ผ ๋•Œ, |V'| โ‰ฅ 2^(n 1) + 1์ธ ๋ชจ๋“  ๋ถ€๋ถ„ ์ง‘ํ•ฉ V'์— ๋Œ€ํ•ด ํด๋ผ์šฐ ๋˜๋Š” ๋‹จ์ˆœ ์ˆœํ™˜์„ ์œ ๋„ํ•˜๋Š” ์ •์ ๋“ค์˜ ์กด์žฌ๋ฅผ ์ฆ๋ช…ํ•œ๋‹ค. ์„œ๋ก  ๋ฐ ์ •์˜ ๋…ผ๋ฌธ์€ ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ๊ฐœ๋…๋“ค์„ ์†Œ๊ฐœํ•˜๊ณ , n์ฐจ์› ํ๋ธŒ Qn๊ณผ ํด๋ผ์šฐ(K1,3)์˜ ์ •์˜๋ฅผ ์ œ๊ณตํ•œ๋‹ค. ํŠนํžˆ, n์ฐจ์› ํ๋ธŒ๋Š” ๊ฐ ์ฐจ์›๋งˆ๋‹ค ๋‘ ๊ฐœ์˜ ๊ฐ’์„ ๊ฐ€์งˆ ์ˆ˜ ์žˆ๋Š” ์ •์  ์ง‘ํ•ฉ์œผ๋กœ ๊ตฌ์„ฑ๋˜๋ฉฐ, ํด๋ผ์šฐ๋Š” ์ค‘์‹ฌ ์ •์ ์„ ํฌํ•จํ•˜๋Š” ์™„์ „ ์ด๋ถ„ ๊ทธ๋ž˜ํ”„ K1,3์„ ์˜๋ฏธํ•œ

Mathematics Computer Science Discrete Mathematics
A conjecture on independent sets and graph covers

A conjecture on independent sets and graph covers

๋ณธ ๋…ผ๋ฌธ์€ ๊ทธ๋ž˜ํ”„ ์ด๋ก ์˜ ํ•ต์‹ฌ ๊ฐœ๋…์ธ ๋…๋ฆฝ ์ง‘ํ•ฉ๊ณผ ์ปค๋ฒ„๋ฅผ ๋‹ค๋ฃจ๋ฉฐ, ํŠนํžˆ M ์ปค๋ฒ„์™€ ๋ฒ ํ…Œ ๊ทผ์‚ฌ(Bethe approximation) ์‚ฌ์ด์˜ ๊ด€๊ณ„๋ฅผ ํƒ๊ตฌํ•œ๋‹ค. ์ด๋Ÿฌํ•œ ์—ฐ๊ตฌ๋Š” ํ†ต๊ณ„ ๋ฌผ๋ฆฌํ•™์—์„œ ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•˜๋Š” ๋ถ„ํ•  ํ•จ์ˆ˜(partition function)์™€ ์ž์œ  ์—๋„ˆ์ง€(free energy)์— ๋Œ€ํ•œ ์ดํ•ด๋ฅผ ํ™•์žฅํ•˜๋Š” ๋ฐ ๊ธฐ์—ฌํ•œ๋‹ค. 1. ๋‹ค๋ณ€์ˆ˜ ๋…๋ฆฝ ์ง‘ํ•ฉ ๋‹คํ•ญ์‹๊ณผ M ์ปค๋ฒ„ ๋…ผ๋ฌธ์€ ๊ทธ๋ž˜ํ”„ G์˜ ๋‹ค๋ณ€์ˆ˜ ๋…๋ฆฝ ์ง‘ํ•ฉ ๋‹คํ•ญ์‹์„ ์ •์˜ํ•˜๊ณ , ์ด๋ฅผ ํ†ตํ•ด ๋…๋ฆฝ ์ง‘ํ•ฉ์˜ ํฌ๊ธฐ์— ๋”ฐ๋ฅธ ๊ฐ€์ค‘์น˜๋ฅผ ํ‘œํ˜„ํ•œ๋‹ค. ์ด ๋‹คํ•ญ์‹์€ G์˜ ๋ชจ๋“  ๋…๋ฆฝ ์ง‘ํ•ฉ I์— ๋Œ€ํ•ด x^{|I|

Mathematics Computer Science Discrete Mathematics
Bandwidth and pathwidth of three-dimensional grids

Bandwidth and pathwidth of three-dimensional grids

๋ณธ ๋…ผ๋ฌธ์€ ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ๋‘ ๊ฐ€์ง€ ํŒŒ๋ผ๋ฏธํ„ฐ์ธ ๋ฐด๋“œ ๋„ˆ๋น„์™€ ๊ฒฝ๋กœ ๋„ˆ๋น„์— ๋Œ€ํ•œ ์‹ฌ๋„ ์žˆ๋Š” ์—ฐ๊ตฌ๋ฅผ ์ œ๊ณตํ•˜๋ฉฐ, ํŠนํžˆ 3์ฐจ์› ๊ทธ๋ฆฌ๋“œ์˜ ๊ฒฝ์šฐ์— ๋Œ€ํ•ด ์ง‘์ค‘์ ์œผ๋กœ ๋‹ค๋ฃฌ๋‹ค. ์ด ์—ฐ๊ตฌ๋Š” ์ปดํ“จํ„ฐ ๊ณผํ•™ ๋ถ„์•ผ์—์„œ ๋„๋ฆฌ ํ™œ์šฉ๋˜๋Š” ๊ทธ๋ž˜ํ”„ ์ด๋ก ์˜ ์ค‘์š”ํ•œ ์ธก๋ฉด์„ ํƒ๊ตฌํ•˜๊ณ  ์žˆ์œผ๋ฉฐ, ๊ทธ ๊ฒฐ๊ณผ๋Š” VLSI ๋ ˆ์ด์•„์›ƒ๊ณผ ๋ณ‘๋ ฌ ์ปดํ“จํŒ… ๋“ฑ ๋‹ค์–‘ํ•œ ์‘์šฉ ๋ถ„์•ผ์— ์ ์šฉ๋  ์ˆ˜ ์žˆ๋‹ค. ๋ฐด๋“œ ๋„ˆ๋น„์™€ ๊ฒฝ๋กœ ๋„ˆ๋น„์˜ ์ •์˜ ๋ฐ ๊ด€๋ จ์„ฑ ๋ฐด๋“œ ๋„ˆ๋น„์™€ ๊ฒฝ๋กœ ๋„ˆ๋น„๋Š” ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ๊ฐœ๋…์œผ๋กœ, ๊ฐ๊ฐ ๊ทธ๋ž˜ํ”„์˜ ๊ตฌ์กฐ๋ฅผ ์ธก์ •ํ•˜๋Š” ๋ฐ ์‚ฌ์šฉ๋œ๋‹ค. ๋ฐด๋“œ ๋„ˆ๋น„๋Š” ๊ทธ๋ž˜ํ”„์˜ ์ •์  ์ง‘ํ•ฉ์„ ์ผ๋ ฌ๋กœ ๋ฐฐ์—ดํ–ˆ์„

Computer Science Discrete Mathematics
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Guaranteed successful strategies for a square achievement game on an n by n grid

์ด ๋…ผ๋ฌธ์€ ์ •์‚ฌ๊ฐํ˜• ๋‹ฌ์„ฑ ๊ฒŒ์ž„์—์„œ ์ตœ์ ์˜ ํ”Œ๋ ˆ์ด ์ „๋žต์— ๋Œ€ํ•œ ์‹ฌ๋„ ์žˆ๋Š” ๋ถ„์„์„ ์ œ๊ณตํ•œ๋‹ค. ์ด ๊ฒŒ์ž„์€ n x n ๊ทธ๋ฆฌ๋“œ ์œ„์—์„œ ๋‘ ํ”Œ๋ ˆ์ด์–ด๊ฐ€ 'O'์™€ 'X'๋ฅผ ๋ฒˆ๊ฐˆ์•„ ๋ฐฐ์น˜ํ•˜๋ฉฐ, ์ฒซ ๋ฒˆ์งธ ํ”Œ๋ ˆ์ด์–ด๋Š” ์ˆ˜ํ‰ ๋ฐ ์ˆ˜์ง ๋ณ€์˜ ๋ชจ์„œ๋ฆฌ์— 4๊ฐœ์˜ ์…€์„ ์ ์œ ํ•˜์—ฌ ์Šน๋ฆฌ๋ฅผ ๋‹ฌ์„ฑํ•ด์•ผ ํ•œ๋‹ค. ๋…ผ๋ฌธ์€ SQRGAME2๋ผ๋Š” ์ปดํ“จํ„ฐ ํ”„๋กœ๊ทธ๋žจ์„ ์‚ฌ์šฉํ•ด n์ด 3, 4, 5์ผ ๋•Œ ๊ฐ ํ”Œ๋ ˆ์ด์–ด๊ฐ€ ์ตœ์ ์˜ ์ „๋žต์œผ๋กœ ๊ฒŒ์ž„์—์„œ ์–ด๋–ป๊ฒŒ ์ด๊ธธ ์ˆ˜ ์žˆ๋Š”์ง€ ๋ถ„์„ํ•œ๋‹ค. ๊ฒŒ์ž„์˜ ๊ทœ์น™๊ณผ ์ง„ํ–‰ ๋ฐฉ์‹์— ๋Œ€ํ•œ ์ž์„ธํ•œ ์„ค๋ช…์€ ๋‹ค์Œ๊ณผ ๊ฐ™๋‹ค. G๋Š” 0๋ถ€ํ„ฐ (์ ์–ด๋„) n 1๊นŒ์ง€์˜ ์ •์ˆ˜ ์ธ๋ฑ์Šค ๋ฒ”์œ„๋ฅผ ๊ฐ€

Mathematics Computer Science Discrete Mathematics
Total coloring of pseudo-outerplanar graphs

Total coloring of pseudo-outerplanar graphs

: 1. ์ด ์ƒ‰์น  ๋ฌธ์ œ์™€ ๊ทธ ์ค‘์š”์„ฑ ์ด ์ƒ‰์น  ๋ฌธ์ œ๋Š” ๊ทธ๋ž˜ํ”„ ์ด๋ก ์—์„œ ์ค‘์š”ํ•œ ์œ„์น˜๋ฅผ ์ฐจ์ง€ํ•˜๋ฉฐ, ๊ฐ ์ •์ ๊ณผ ๊ฐ„์„ ์— ๊ณ ์œ ํ•œ ์ƒ‰์ƒ์„ ํ• ๋‹นํ•˜๋Š” ๋ฐฉ์‹์œผ๋กœ ๊ทธ๋ž˜ํ”„์˜ ๊ตฌ์กฐ์  ํŠน์„ฑ์„ ์ดํ•ดํ•˜๊ณ  ๋ถ„์„ํ•ฉ๋‹ˆ๋‹ค. ํŠนํžˆ, ์ด ์ƒ‰์น  ์ถ”์ธก์€ ๊ทธ๋ž˜ํ”„์˜ ์ตœ๋Œ€ ์ฐจ์ˆ˜ ฮ”(G)์™€ ๊ด€๋ จ๋œ ์ค‘์š”ํ•œ ๋ฌธ์ œ๋กœ, ์ด ์ถ”์ธก์ด ์ฆ๋ช…๋˜๋ฉด ๋งŽ์€ ๊ทธ๋ž˜ํ”„ ํด๋ž˜์Šค์— ๋Œ€ํ•œ ์ด ์ƒ‰์ƒ ์ˆ˜๋ฅผ ๊ฒฐ์ •ํ•˜๋Š” ๋ฐ ๋„์›€์ด ๋ฉ๋‹ˆ๋‹ค. 2. ์œ„์ƒ์  ์™ธํŒ ๊ทธ๋ž˜ํ”„์˜ ์ •์˜ ๋ฐ ํŠน์„ฑ ์œ„์ƒ์  ์™ธํŒ ๊ทธ๋ž˜ํ”„๋Š” ๊ฐ ๋ธ”๋ก์ด ๊ณ ์ •๋œ ์› ์œ„์—์„œ ์ •์ ๋“ค์„ ๋ฐฐ์น˜ํ•˜๊ณ , ๊ฐ„์„ ๋“ค์ด ์›์˜ ๋””์Šคํฌ ๋‚ด๋ถ€์—์„œ ์„œ๋กœ ๊ต์ฐจํ•˜์ง€ ์•Š๋„๋ก ๋ฐฐ์น˜๋  ์ˆ˜ ์žˆ๋Š” ๊ทธ๋ž˜

Mathematics Computer Science Discrete Mathematics
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Greedy Set Cover Estimations

๋ณธ ๋…ผ๋ฌธ์€ ์ง‘ํ•ฉ ๋ฎ๊ธฐ ๋ฌธ์ œ(Set Cover Problem)์— ๋Œ€ํ•œ ์ƒˆ๋กœ์šด ์ ‘๊ทผ ๋ฐฉ์‹์„ ์ œ์•ˆํ•˜๋ฉฐ, ํŠนํžˆ ์ด์ง„ ํƒ์ƒ‰ ์•Œ๊ณ ๋ฆฌ์ฆ˜์„ ์ด์šฉํ•œ ๊ทผ์‚ฌ ์•Œ๊ณ ๋ฆฌ์ฆ˜์˜ ๊ฐœ์„ ์ ์„ ๋‹ค๋ฃฌ๋‹ค. ์ง‘ํ•ฉ ๋ฎ๊ธฐ ๋ฌธ์ œ๋Š” NP ์™„์ „ ๋ฌธ์ œ๋กœ ์•Œ๋ ค์ ธ ์žˆ์–ด ์ •ํ™•ํ•œ ํ•ด๊ฒฐ์ฑ…์„ ์ฐพ๋Š” ๊ฒƒ์ด ๋งค์šฐ ์–ด๋ ต๋‹ค๋Š” ์ ์—์„œ ์ค‘์š”ํ•˜๋‹ค. ๋”ฐ๋ผ์„œ, ๋ณธ ๋…ผ๋ฌธ์€ ์ด ๋ฌธ์ œ๋ฅผ ํšจ๊ณผ์ ์œผ๋กœ ๊ทผ์‚ฌํ•˜๋Š” ๋ฐฉ๋ฒ•์„ ์ œ์‹œํ•จ์œผ๋กœ์จ ์‹ค์šฉ์ ์ธ ํ•ด๊ฒฐ์ฑ…์„ ์ œ๊ณตํ•œ๋‹ค. ๊ธฐ์กด ์ ‘๊ทผ ๋ฐฉ์‹์˜ ํ•œ๊ณ„ ๊ธฐ์กด์˜ ์ ‘๊ทผ ๋ฐฉ์‹์—์„œ๋Š” ๊ฐ ์—ด์— ์ตœ์†Œ m๊ฐœ์˜ 1์ด ์žˆ๋Š” (0,1) ํ–‰๋ ฌ๋กœ ์ง‘ํ•ฉ ๋ฎ๊ธฐ ๋ฌธ์ œ๋ฅผ ํ‘œํ˜„ํ•˜๊ณ , ์ด์ง„ ํƒ์ƒ‰์„ ํ†ตํ•ด ๊ฐ€์žฅ ๋งŽ์€ 1์„ ํฌํ•จํ•˜

Computer Science Discrete Mathematics

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