Mathematics / Math.GN

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Transfinite Sequences of Continuous and Baire Class 1 Functions

Transfinite Sequences of Continuous and Baire Class 1 Functions

๋ณธ ๋…ผ๋ฌธ์€ ์—ฐ์† ํ•จ์ˆ˜์™€ ๋ฐ”์ด์–ด ํด๋ž˜์Šค 1 ํ•จ์ˆ˜์˜ ์ˆœ์„œ ์œ ํ˜•์— ๋Œ€ํ•œ ์‹ฌ๋„ ์žˆ๋Š” ๋ถ„์„์„ ์ œ๊ณตํ•˜๋ฉฐ, ํŠนํžˆ ์ด๋Ÿฌํ•œ ํ•จ์ˆ˜๋“ค์˜ ์ฆ๊ฐ€ ๋˜๋Š” ๊ฐ์†Œํ•˜๋Š” ์ž˜ ์ •๋ ฌ๋œ ์‹œํ€€์Šค์˜ ๊ธธ์ด๋ฅผ ์กฐ์‚ฌํ•œ๋‹ค. ์ด ์—ฐ๊ตฌ๋Š” ๊ธฐ์กด์˜ ๊ณ ์ „์ ์ธ ๊ฒฐ๊ณผ๋ฅผ ํ™•์žฅํ•˜๊ณ , ๋ฉ”ํŠธ๋ฆญ ๊ณต๊ฐ„์—์„œ ๋ฐ”์ด์–ด ํด๋ž˜์Šค 1 ํ•จ์ˆ˜์˜ ์‚ฌ์Šฌ์— ๋Œ€ํ•œ ์ƒˆ๋กœ์šด ๊ด€์ ์„ ์ œ์‹œํ•œ๋‹ค. ์—ฐ์† ํ•จ์ˆ˜์™€ ๋ฐ”์ด์–ด ํด๋ž˜์Šค 1 ํ•จ์ˆ˜์˜ ์ˆœ์„œ ์œ ํ˜• ๋…ผ๋ฌธ์€ ๋จผ์ € ํด๋ž€๋“œ ๊ณต๊ฐ„์—์„œ ์—ฐ์† ํ•จ์ˆ˜์™€ ๋ฐ”์ด์–ด ํด๋ž˜์Šค 1 ํ•จ์ˆ˜์˜ ์‹œํ€€์Šค๋ฅผ ๋ถ„์„ํ•œ๋‹ค. ์ด๋Š” ๊ณ ์ „์ ์ธ ๊ฒฐ๊ณผ์ธ Kuratowski์˜ ์ •๋ฆฌ์— ๊ธฐ๋ฐ˜ํ•˜๋ฉฐ, ๋ฐ”์ด์–ด ํด๋ž˜์Šค 1 ํ•จ์ˆ˜์˜ ๋ชจ๋…ธํ†ค ์‹œํ€€์Šค์˜ ๊ธธ์ด

Mathematics
Decomposition of Cellular Balleans

Decomposition of Cellular Balleans

: ์ด ๋…ผ๋ฌธ์€ ์„ธํฌ ๊ตฌ ๊ตฌ์กฐ์— ๋Œ€ํ•œ ์‹ฌ๋„ ์žˆ๋Š” ์—ฐ๊ตฌ๋ฅผ ์ง„ํ–‰ํ•˜๋ฉฐ, ํŠนํžˆ ์ด๋Ÿฌํ•œ ๊ตฌ ๊ตฌ์กฐ์˜ ๋ถ„ํ•ด ๊ฐ€๋Šฅ์„ฑ๊ณผ ๋ฉ”ํŠธ๋ฆญํ™” ๊ฐ€๋Šฅ์„ฑ์„ ํƒ๊ตฌํ•œ๋‹ค. ๊ตฌ ๊ตฌ์กฐ๋Š” ์„ธ ๊ฐ€์ง€ ์š”์†Œ B ( X , P , B )๋กœ ๊ตฌ์„ฑ๋˜๋ฉฐ, ์—ฌ๊ธฐ์„œ X ์™€ P ๋Š” ๋น„๊ณตํ—ˆ ์ง‘ํ•ฉ์ด๊ณ , ๋ชจ๋“  x โˆˆ X ์™€ ฮฑ โˆˆ P ์— ๋Œ€ํ•ด B(x, ฮฑ) ๋Š” ๋ฐ˜์ง€๋ฆ„ ฮฑ ์˜ ๊ตฌ๋ฅผ ๋‚˜ํƒ€๋‚ด๋Š” X ์˜ ๋ถ€๋ถ„์ง‘ํ•ฉ์ด๋‹ค. ๋…ผ๋ฌธ์€ ์ด๋Ÿฌํ•œ ๊ตฌ ๊ตฌ์กฐ๊ฐ€ ๋ฉ”ํŠธ๋ฆญํ™” ๊ฐ€๋Šฅํ•˜๊ฑฐ๋‚˜ ์„ธํฌ ๊ตฌ ๊ตฌ์กฐ๋กœ ๋ถ„ํ•ด๋  ์ˆ˜ ์žˆ๋Š” ์กฐ๊ฑด์„ ์ •๋ฆฌํ•˜๊ณ  ์ฆ๋ช…ํ•œ๋‹ค. 1. ๊ตฌ ๊ตฌ์กฐ์˜ ๊ธฐ๋ณธ ๊ฐœ๋… ๊ตฌ ๊ตฌ์กฐ๋Š” ์„ธ ๊ฐ€์ง€ ์š”์†Œ B ( X , P , B )๋กœ ๊ตฌ์„ฑ๋˜๋ฉฐ

Mathematics
Convex hyperspaces of probability measures and extensors in the   asymptotic category

Convex hyperspaces of probability measures and extensors in the asymptotic category

๋งค๋ ฅ์ ์ธ ํ•œ๊ธ€ ์ œ๋ชฉ: ํ™•๋ฅ  ์ธก๋„ ๊ณต๊ฐ„์—์„œ ์••์ถ• ๊ณต์ง‘์˜ ์ ˆ๋Œ€ ํ™•์žฅ์„ฑ ์—ฐ๊ตฌ ์ดˆ๋ก ์ „์ฒด ๋ฒˆ์—ญ ๋ฐ ์ •๋ฆฌ: ๋ณธ ๋…ผ๋ฌธ์€ ๋ฉ”ํŠธ๋ฆญ ๊ณต๊ฐ„ ์œ„์— ์ •์˜๋œ ํ™•๋ฅ  ์ธก๋„ ๊ณต๊ฐ„๊ณผ ๊ทธ ํ•˜์ดํผ์ŠคํŽ˜์ด์Šค์ธ ์••์ถ• ๊ณต์ง‘์˜ ์ ˆ๋Œ€ ํ™•์žฅ์ž ์„ฑ์งˆ์„ ํƒ๊ตฌํ•œ๋‹ค. ํŠนํžˆ, ๊ทผ์‚ฌ ๋ฒ”์ฃผ์—์„œ ์ด๋Ÿฌํ•œ ๊ณต๊ฐ„๋“ค์ด ์ ˆ๋Œ€ ํ™•์žฅ์ž๊ฐ€ ๋˜๋Š”์ง€ ์—ฌ๋ถ€๋ฅผ ๋ถ„์„ํ•œ๋‹ค. ๋…ผ๋ฌธ์€ ๋“œ๋ผ๋‹ˆ์‹œ๋‹ˆ์ฝ”ํ”„๊ฐ€ ์ œ๊ธฐํ•œ ๋ฌธ์ œ์— ๋Œ€ํ•œ ๋ถ€์ •์ ์ธ ๋‹ต๋ณ€์„ ์ œ๊ณตํ•˜๋ฉฐ, ์ด๋Š” ๋ฉ”ํŠธ๋ฆญ ๊ณต๊ฐ„์˜ ํ™•๋ฅ  ์ธก๋„ ๊ณต๊ฐ„์ด ์ผ๋ฐ˜์ ์œผ๋กœ ๊ทผ์‚ฌ ๋ฒ”์ฃผ์˜ ์ ˆ๋Œ€ ํ™•์žฅ์ž๊ฐ€ ์•„๋‹ˆ๋ผ๋Š” ๊ฒƒ์„ ๋ณด์—ฌ์ค€๋‹ค. ๋˜ํ•œ, ๋ณธ ์—ฐ๊ตฌ์—์„œ๋Š” ์••์ถ• ๊ณต์ง‘์˜ ํŠน์„ฑ์„ ๋ถ„์„ํ•˜๊ณ , ์ด๋ฅผ ํ†ตํ•ด ํ™•๋ฅ  ์ธก๋„ ๊ณต

Mathematics
Preservation of the Borel class under open-$LC$ functions

Preservation of the Borel class under open-$LC$ functions

๋ณธ ๋…ผ๋ฌธ์€ ๋ณด๋  ์ง‘ํ•ฉ๊ณผ ๊ทธ ๋ณด๋  ํด๋ž˜์Šค์— ๋Œ€ํ•œ ์ค‘์š”ํ•œ ์ด๋ก ์  ๊ฒฐ๊ณผ๋ฅผ ์ œ๊ณตํ•œ๋‹ค. ํŠนํžˆ, ๊ฐœ๋ฐฉํ˜• ํด๋กœ์ฆˆ๋“œ(clopen) ํ•จ์ˆ˜๋ผ๋Š” ์ƒˆ๋กœ์šด ๊ฐœ๋…์„ ๋„์ž…ํ•˜์—ฌ, ์ด๋Ÿฌํ•œ ํ•จ์ˆ˜๊ฐ€ ํŠน์ • ์กฐ๊ฑด ํ•˜์—์„œ ๋ณด๋  ์ง‘ํ•ฉ์˜ ๋ณด๋  ํด๋ž˜์Šค๋ฅผ ์œ ์ง€ํ•˜๋Š” ๊ฒƒ์„ ์ฆ๋ช…ํ•˜๊ณ  ์žˆ๋‹ค. 1. ์„œ๋ก  ์„œ๋ก ์—์„œ๋Š” ๋ณด๋  ์ง‘ํ•ฉ๊ณผ ๊ทธ ๋ณด๋  ํด๋ž˜์Šค์— ๋Œ€ํ•œ ๊ธฐ์กด ์—ฐ๊ตฌ๋ฅผ ๊ฐ„๋žตํžˆ ์†Œ๊ฐœํ•œ๋‹ค. ํŠนํžˆ, ๋ณด๋  ์ง‘ํ•ฉ C์˜ ๋ถ€๋ถ„ ์ง‘ํ•ฉ X์™€ ์—ฐ์† ํ•จ์ˆ˜ f: X โ†’ Y๊ฐ€ ์ฃผ์–ด์กŒ์„ ๋•Œ, ๋งŒ์•ฝ ๋ชจ๋“  ํด๋กญ์—” ์„ธํŠธ U์˜ ์ด๋ฏธ์ง€ f(U)๊ฐ€ ์—ด๋ฆฐ ์ง‘ํ•ฉ์ด๊ฑฐ๋‚˜ ๋‹ซํžŒ ์ง‘ํ•ฉ์ด๋ผ๋ฉด, Y๋Š” ๋™์ผํ•œ ๋ณด๋  ํด๋ž˜์Šค๋ฅผ ๊ฐ€์ง„๋‹ค๋Š” ๊ฒฐ๊ณผ๋ฅผ ์–ธ๊ธ‰

Mathematics
Another approach to parametric Bing and Krasinkiewicz maps

Another approach to parametric Bing and Krasinkiewicz maps

๋ณธ ๋…ผ๋ฌธ์€ ๋น„๋‹(Bing) ๋งต๊ณผ ํฌ๋ผ์‹ ํ‚ค์—๋น„์น˜(Krasinkiewicz) ๋งต์— ๋Œ€ํ•œ ์ƒˆ๋กœ์šด ์ ‘๊ทผ๋ฒ•์„ ์ œ์‹œํ•˜๋ฉฐ, ํŠนํžˆ ํŒŒ๋ผ์ฝคํŒฉํŠธ ๊ณต๊ฐ„์—์„œ ์ด๋Ÿฌํ•œ ๋งต๋“ค์ด ์–ด๋–ป๊ฒŒ ํ•จ์ˆ˜ ๊ณต๊ฐ„ ๋‚ด์—์„œ ๋ฐ€์ง‘ ๋ถ€๋ถ„ ์ง‘ํ•ฉ์„ ํ˜•์„ฑํ•˜๋Š”์ง€ ๋ถ„์„ํ•œ๋‹ค. ์ด ์—ฐ๊ตฌ๋Š” Pasynkov์˜ ๊ธฐ๋ฒ•์„ ํ™œ์šฉํ•˜์—ฌ, ๋น„๋‹ ๋ฐ ํฌ๋ผ์‹ ํ‚ค์—๋น„์น˜ ๋งต์ด ์–ด๋–ค ์กฐ๊ฑด ํ•˜์—์„œ ํŠน์ • ์„ฑ์งˆ์„ ๊ฐ–๊ฒŒ ๋˜๋Š”์ง€๋ฅผ ํƒ๊ตฌํ•œ๋‹ค. 1. ๋„์ž… ๋ฐ ๋ฐฐ๊ฒฝ ๋…ผ๋ฌธ์€ ๋น„๋‹ ๋งต๊ณผ ํฌ๋ผ์‹ ํ‚ค์—๋น„์น˜ ๋งต์˜ ์ •์˜์™€ ๊ด€๋ จ๋œ ์ด๋ก ์  ๋ฐฐ๊ฒฝ์„ ์„ค๋ช…ํ•œ๋‹ค. ๋น„๋‹ ๋งต์€ ์ปดํŒฉํŠธ ๊ณต๊ฐ„ ์‚ฌ์ด์˜ ๋งต ์ค‘, ๋ชจ๋“  ์„ฌ์œ ๊ฐ€ ๋น„๋‹ ๊ณต๊ฐ„์ธ ๊ฒฝ์šฐ๋ฅผ ๋งํ•˜๋ฉฐ, ์—ฌ๊ธฐ์„œ ๋น„๋‹ ๊ณต

Mathematics
A 1-dimensional Peano continuum which is not an IFS attractor

A 1-dimensional Peano continuum which is not an IFS attractor

: ๋ณธ ๋…ผ๋ฌธ์€ ๋ณต์žกํ•œ ์œ„์ƒ ๊ณต๊ฐ„ ์ด๋ก ๊ณผ ๊ด€๋ จ๋œ ์ค‘์š”ํ•œ ๋ฌธ์ œ๋ฅผ ๋‹ค๋ฃจ๊ณ  ์žˆ๋‹ค. ํŠนํžˆ, ๋ฌดํ•œ ์ฐจ์›์˜ ํ‰๋ฉด Peano ์—ฐ์†์ฒด๊ฐ€ IFS attractor์™€ ๋™ํ˜•์ด ๋  ์ˆ˜ ์žˆ๋Š”์ง€์— ๋Œ€ํ•œ ์งˆ๋ฌธ์„ ์ œ๊ธฐํ•˜๊ณ  ์ด๋ฅผ ๋ถ€์ •์ ์œผ๋กœ ํ•ด๊ฒฐํ•œ๋‹ค. IFS attractor๋Š” ๋ฐ˜๋ณต ํ•จ์ˆ˜ ์‹œ์Šคํ…œ(Iterated Function System)์„ ํ†ตํ•ด ์ƒ์„ฑ๋˜๋Š” ์ง‘ํ•ฉ์œผ๋กœ, ์••์ถ•๋œ ๋ฉ”ํŠธ๋ฆญ ๊ณต๊ฐ„์—์„œ ์ค‘์š”ํ•œ ์—ญํ• ์„ ํ•œ๋‹ค. ์ด ๋…ผ๋ฌธ์—์„œ๋Š” IFS attractor์˜ ์œ„์ƒํ•™์  ์„ฑ์งˆ์— ๋Œ€ํ•ด ๊นŠ์ด ์žˆ๊ฒŒ ๋ถ„์„ํ•œ๋‹ค. ํŠนํžˆ, ์—ฐ๊ฒฐ๋œ IFS attractor๋Š” ๊ตญ์†Œ์ ์œผ๋กœ ์—ฐ๊ฒฐ๋˜์–ด ์žˆ๊ณ , ์†์„ฑ

Mathematics
SPM Bulletin 32

SPM Bulletin 32

[Catchy Title KO]: ์นœ๊ตฌ Ljubiลกa Koฤinac์˜ ์ƒ์ผ์„ ๊ธฐ๋…ํ•˜๋Š” ํ† ํฌ๋กœ์ง€ ์›Œํฌ์ˆ [Abstract KO]: ์ด ๋ฌธ์„œ๋Š” ์นœ๊ตฌ์ธ Ljubiลกa Koฤinac ์”จ์˜ 65์„ธ ์ƒ์ผ์„ ๊ธฐ๋…ํ•˜์—ฌ ์กฐ์ง๋œ IV ์›Œํฌ์ˆ: ํ† ํฌํ•™์—์„œ์˜ ๋ฎ๊ฐœ, ์„ ํƒ ๋ฐ ๊ฒŒ์ž„ ์— ๋Œ€ํ•œ ์•ˆ๋‚ด์ž…๋‹ˆ๋‹ค. ์ด ์›Œํฌ์ˆ์€ ์„ธ์ฝ˜๋‹ค ์œ ๋‹ˆ๋ฒ ๋ฅด์‹œํƒ€ ๋”” ๋‚˜ํด๋ฆฌ ์ˆ˜ํ•™๋ถ€์—์„œ 3์›” 2์ผ(๊ธˆ)์— ๊ฐœ์ตœ๋  ์˜ˆ์ •์ด๋ฉฐ, ๊ฐ ๋ฐœํ‘œ๋Š” ์•ฝ 30๋ถ„๊ฐ„ ์ง„ํ–‰๋ฉ๋‹ˆ๋‹ค. ๋˜ํ•œ, ์žฌ์ • ์ƒํ™ฉ์œผ๋กœ ์ธํ•ด ์ฐธ๊ฐ€ ์ง€์› ๋ฐ ๋“ฑ๋ก๋น„ ์ •๋ณด๋Š” ์•„์ง ํ™•์ •๋˜์ง€ ์•Š์•˜์Šต๋‹ˆ๋‹ค. ์‹ฌ๋„ ๋ถ„์„ (Deep Analysis KO): ์ด

Mathematics
$sigma$-homogeneity of Borel sets

$sigma$-homogeneity of Borel sets

๋ณธ ๋…ผ๋ฌธ์€ ๋ณด๋  ์ง‘ํ•ฉ์˜ ๋™์งˆ์„ฑ์— ๋Œ€ํ•œ ๊นŠ์ด ์žˆ๋Š” ์ดํ•ด๋ฅผ ์ œ๊ณตํ•˜๋ฉฐ, ํŠนํžˆ ์นธํ† ์–ด ์ง‘ํ•ฉ C ๋‚ด์—์„œ ๋ณด๋  ์ง‘ํ•ฉ์˜ ๊ตฌ์กฐ์™€ ๊ทธ ์„ฑ์งˆ์„ ํƒ๊ตฌํ•œ๋‹ค. ์ด ์—ฐ๊ตฌ๋Š” h ๋™์งˆ ๊ณต๊ฐ„์ด๋ผ๋Š” ๊ฐœ๋…์„ ์ค‘์‹ฌ์œผ๋กœ ์ง„ํ–‰๋˜๋ฉฐ, ์ด๋ฅผ ํ†ตํ•ด ๋ณด๋  ์ง‘ํ•ฉ์˜ ๋™์งˆ์„ฑ์„ ๋ถ„์„ํ•˜๊ณ  ์žˆ๋‹ค. 1. ๊ธฐ๋ณธ ๊ฐœ๋… ๋ฐ ์ •์˜ ๋…ผ๋ฌธ์—์„œ๋Š” ๋จผ์ € ๋ช‡ ๊ฐ€์ง€ ์ค‘์š”ํ•œ ์šฉ์–ด๋ฅผ ์ •์˜ํ•œ๋‹ค: ์นธํ† ์–ด ์ง‘ํ•ฉ (C) : ์ด์‚ฐ์  ์ˆ˜์™€ ํ•ฉ๋ฆฌ์  ์ˆ˜๋ฅผ ๊ฐ๊ฐ P, Q๋กœ ํ‘œ๊ธฐํ•˜๋ฉฐ, ์‹ค์ˆ˜ R์€ P์™€ Q์˜ ํ•ฉ์ง‘ํ•ฉ์œผ๋กœ ํ‘œํ˜„๋œ๋‹ค. h ๋™์งˆ ๊ณต๊ฐ„ : 0์ฐจ์› ํ† ํด๋กœ์ง€ ๊ณต๊ฐ„ X๊ฐ€ ๋ชจ๋“  ๋น„๊ณตํ—ˆ ํด๋กœํ”„ ์—ด๋ถ„ U์— ๋Œ€ํ•ด U์™€ X๊ฐ€ ํ™ˆ๋ชจ๋ฅดํ”ฝ(h

Mathematics
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Representing a profinite group as the homeomorphism group of a continuum

: ์ด ๋…ผ๋ฌธ์€ ํ”„๋กœํ•€ํŠธ ๊ตฐ(profinite group)์˜ ํ‘œํ˜„์— ์ƒˆ๋กœ์šด ์ ‘๊ทผ ๋ฐฉ์‹์„ ์ œ์‹œํ•˜๊ณ  ์žˆ๋‹ค. ํŠนํžˆ, ์ด ์—ฐ๊ตฌ๋Š” ๊ทธ๋ž˜ํ”„ ์ด๋ก ์„ ํ™œ์šฉํ•˜์—ฌ ํ”„๋กœํ•€ํŠธ ๊ตฐ์„ ์—ฐ์†์ ์ธ ์—ฐ๊ฒฐ๋œ ๋ฉ”ํŠธ๋ฆญ ๊ณต๊ฐ„์˜ ํ™ˆ์˜ค๋ชจ๋ฅดํ”ผ์ฆ˜ ๊ทธ๋ฃน(homeomorphism group)์œผ๋กœ ํ‘œํ˜„ํ•˜๋Š” ๋ฐฉ๋ฒ•์„ ํƒ๊ตฌํ•œ๋‹ค. 1. ๊ธฐ์กด ์—ฐ๊ตฌ์™€์˜ ์ฐจ๋ณ„ํ™” ๊ธฐ์กด ์—ฐ๊ตฌ์—์„œ๋Š” ์ฃผ๋กœ ํ”„๋กœํ•€ํŠธ ๊ตฐ์ด ์ปดํŒฉํŠธํ•œ ์—ฐ๊ฒฐ๋œ ๋ฉ”ํŠธ๋ฆญ ๊ณต๊ฐ„์˜ ํ™ˆ์˜ค๋ชจ๋ฅดํ”ผ์ฆ˜ ๊ทธ๋ฃน๊ณผ ๋™ํ˜•์ด๋ผ๋Š” ์‚ฌ์‹ค์„ ์ฆ๋ช…ํ•˜์˜€๋‹ค(

Mathematics

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