2020年10月8日 星期四

Sir Roger Penrose.Nobel Prize. MOSAIC SOPHISTICATION

When a massive star collapses under its own gravity, it forms a black hole that is so heavy that it captures everything that passes its event horizon. Not even light can escape. At the event horizon, time replaces space and points only forward. The flow of time carries everything towards a singularity furthest inside the black hole, where density is infinite and time ends (see figure).
Roger Penrose – awarded the 2020 Nobel Prize in Physics – invented ingenious mathematical methods to explore Albert Einstein’s general theory of relativity. He showed that the theory leads to the formation of black holes, those monsters in time and space that capture everything that enters them.
Not even Albert Einstein, the father of general relativity, thought that black holes could actually exist. However, ten years after Einstein’s death, the British theorist Roger Penrose demonstrated that black holes can form and described their properties. At their heart, black holes hide a singularity, a boundary at which all the known laws of nature break down.
To prove that black hole formation is a stable process, Penrose needed to expand the methods used to study the theory of relativity – tackling the theory’s problems with new mathematical concepts. Penrose’s ground-breaking article was published in January 1965 and is still regarded as the most important contribution to the general theory of relativity since Einstein.
The 2020 Nobel Prize in Physics has been awarded with one half to Roger Penrose “for the discovery that black hole formation is a robust prediction of the general theory of relativity” and the other half jointly to Reinhard Genzel and Andrea Ghez “for the discovery of a supermassive compact object at the centre of our galaxy.”
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圖像裡可能有顯示的文字是「 Cross section of a black hole When massive collapses under black hati everything passes escape. points forward. singularity inside density is inhnite and time nds. own gravity, captures OBSERVER morizon replaces and erything black hole, where SINGULARITY EVENT HORIZON TIME SINGULARITY SPACE TIME EVENT HORIZON TIME SPACE MATTER FUTURE COLLAPSING STAR PRESENT The cone shows paths backward When horizon PAST horizon, they ©Johan Jarnestad/T forward and black black event toward singularity. outside light event ee further In. nudge No Royal Swedish Academy Sciences 」







羅傑·潘洛斯爵士,OMFRS(英語:Sir Roger Penrose,1931年8月8日),英國數學物理學家牛津大學數學系W. W. Rouse Ball名譽教授。他在數學物理方面的工作擁有高度評價,特別是對廣義相對論宇宙學方面的貢獻。他也是娛樂數學家與具爭議性的哲學家。羅傑·潘洛斯是科學家理昂內·潘洛斯瑪格麗特·雷瑟斯的兒子,為數學家奧利佛·潘洛斯西洋棋大師強納森·潘洛斯的兄弟。

他於2020年獲得諾貝爾物理學獎,因為他發現黑洞的形成有力預測了廣義相對論


Hanching Chung

3人中只知道此君。連我這外行人都買過:Popular publications
The Emperor's New Mind: Concerning Computers, Minds, and The Laws of Physics (1989) 可能有中譯


羅傑·潘洛斯以其於1974年發現潘洛斯鋪磚法著稱,能以兩種磚片非週期性地鋪滿整個平面。於1984年,類似特徵被發現在類晶體中的原子排列。他最重要的貢獻可能是他在1971年發明了自旋網路,爾後在迴圈量子重力理論中成為構成時空幾何的基礎。他在推廣通稱為潘洛斯圖因果圖頗具影響力。


西方藝術中的幾何多半著重空間與比例,但是在其他文化,特別是伊斯蘭、中國和日本,平面幾何藝術則是較為繁盛,尤其是嵌合、拼貼和織錦藝術,通常都會利用緊密複雜的重複圖形,製造精細美麗的視覺效果。

幾何藝術其實就是點、線、面的規律組成,經過幾百年的發展後,「面」與「界」的應用產生了各種繁雜而循環的樣式,有些後來甚至為數學法則證明。一九七四年之前,大家深信嵌合組成的基本樣式只有一、二、三、四、六角對稱,直到牛津大學的數學家羅傑‧潘若斯(Roger Penrose)發現了五角對稱的樣式,才把這種迷思推翻。組成這種樣式的主要成分有二,「菱形」和兩組角各為七十二度和一百四十四度的「鳶形」。鳶形中兩條對角線的比例正好是黃金比例。

潘若斯用這兩種胖「菱形」與瘦「鳶形」的磁磚拼湊出五角對稱,但是儘管看起來很像,事實上五角對稱的圖樣,並不會如同其他對稱那般不斷規律重複,而是會一直變化。

伯斯的西澳大利亞大學的分子化學大樓,中庭地板就巧妙地運用潘若斯的五角對稱概念(見下圖上半部)鋪設地磚。這起先是凱普(David Kepert)、林肯(Frank Lincoln)還有化學學院院長共同的主意,建築師佛格森(Guz Ferguson)則是負責磁磚設計。結果鋪排的圖形從天井中央的五芒星開始,介於電梯和樓梯之間(五芒星在古文明有深遠的意涵)。佛格森用了兩種當地產的水泥磚,分別是瘦長鳶形和菱形。

佛格森用簡單的兩種形狀,舖絮出了奇異而複雜的網狀線條,也讓人見識到幾何世界不可思議的無盡可能性。如此奧秘而複雜的結構,給人的震撼是一般對稱圖形所遠遠不能及的。

盯著這種繁複的圖案一段時間之後,一般都會產生錯覺,覺得自己看到了什麼圖案,像是五芒星、對稱多面體、彎彎曲曲的長條之類。立體感錯覺也常常在這時候介入搗亂,讓人覺得看見了凹凸立體的形狀,但事實上圖形的表面是完全平坦的,就像是瑞士結晶學家奈克(Necker)一八三二年著名的凹凸方塊為例。

早期拼磚藝術家們多半會利用這種錯覺,以顏色、質料不同的磚瓦製造立體效果,並在其間留下空隙作為勾邊。早在一五二四年德國藝術家杜赫(Albrecht Dürer)讓人困惑的作品中,就可以看到這種傾向。把某些區塊塗黑之後,帶有立體感的圖形看起來順眼多了,因為它們看起來就是像立體方塊。儘管原本的作品上並沒有標明陰影,但是我們看到的時候就是忍不住會「覺得」那是立體的。

同樣地,西澳大利亞大學的拼磚也沒有任何呈現立體感的深淺著色,因為那樣做會把視覺效果變得太明顯而讓人不舒服。不過就算沒有深淺色差,看到的人還是忍不住會覺得它是立體的,抗拒這種錯覺反而比較困難。



K. Dudley and M. Elliff

MOSAIC SOPHISTICATION A quasi-crystalline Penrose pattern at the Darb-i Imam shrine in Isfahan, Iran.

Published: February 27, 2007

In the beauty and geometric complexity of tile mosaics on walls of medieval Islamic buildings, scientists have recognized patterns suggesting that the designers had made a conceptual breakthrough in mathematics beginning as early as the 13th century.

Science

A piece from a mausoleum in Turkey.

W. B. Denny

A pattern taken from a Turkish mosque.

A new study shows that the Islamic pattern-making process, far more intricate than the laying of one's bathroom floor, appears to have involved an advanced math of quasi crystals, which was not understood by modern scientists until three decades ago.

The findings, reported in the current issue of the journal Science, are a reminder of the sophistication of art, architecture and science long ago in the Islamic culture. They also challenge the assumption that the designers somehow created these elaborate patterns with only a ruler and a compass. Instead, experts say, they may have had other tools and concepts.

Two years ago, Peter J. Lu, a doctoral student in physics at Harvard University, was transfixed by the geometric pattern on a wall in Uzbekistan. It reminded him of what mathematicians call quasi-crystalline designs. These were demonstrated in the early 1970s by Roger Penrose, a mathematician and cosmologist at the University of Oxford.

Mr. Lu set about examining pictures of other tile mosaics from Afghanistan, Iran, Iraq and Turkey, working with Paul J. Steinhardt, a Princeton cosmologist who is an authority on quasi crystals and had been Mr. Lu's undergraduate adviser. The research was a bit like trying to figure out the design principle of a jigsaw puzzle, Mr. Lu said in an interview.

In their journal report, Mr. Lu and Dr. Steinhardt concluded that by the 15th century, Islamic designers and artisans had developed techniques "to construct nearly perfect quasi-crystalline Penrose patterns, five centuries before discovery in the West."

Some of the most complex patterns, called "girih" in Persian, consist of sets of contiguous polygons fitted together with little distortion and no gaps. Running through each polygon (a decagon, pentagon, diamond, bowtie or hexagon) is a decorative line. Mr. Lu found that the interlocking tiles were arranged in predictable ways to create a pattern that never repeats — that is, quasi crystals.

"Again and again, girih tiles provide logical explanations for complicated designs," Mr. Lu said in a news release from Harvard.

He and Dr. Steinhardt recognized that the artisans in the 13th century had begun creating mosaic patterns in this way. The geometric star-and-polygon girihs, as quasi crystals, can be rotated a certain number of degrees, say one-fifth of a circle, to positions from which other tiles are fitted. As such, this makes possible a pattern that is infinitely big and yet the pattern never repeats itself, unlike the tiles on the typical floor.

This was, the scientists wrote, "an important breakthrough in Islamic mathematics and design."

Dr. Steinhardt said in an interview that it was not clear how well the Islamic designers understood all the elements they were applying to the construction of these patterns. "I can just say what's on the walls," he said.

Mr. Lu said that it would be "incredible if it were all coincidence."

"At the very least," he said, "it shows us a culture that we often don't credit enough was far more advanced than we ever thought before."

From a study of a few hundred examples, Mr. Lu and Dr. Steinhardt determined that the technique was fully developed two centuries later in mosques, palaces, shrines and other buildings. They noted that "a nearly perfect quasi-crystalline Penrose pattern" is found on the Darb-i Imam shrine in Isfahan, Iran, which was built in 1453. The researchers described how the architects there had created overlapping patterns with girih tiles at two sizes to produce nearly perfect quasi-crystalline patterns.

In the report, Mr. Lu and Dr. Steinhardt said the examples they had studied so far "fall just short of being perfect quasi crystals; there may be more interesting examples yet to be discovered."

In a separate article in Science, some experts in the math of crystals questioned if the findings were an entirely new insight. In particular, Emil Makovicky of the University of Copenhagen in Denmark said the new report failed to give sufficient credit to an analysis he published in 1992 of mosaic patterns on a tomb in Iran.

Mr. Lu and Dr. Steinhardt said they regretted what they called a misunderstanding. They pointed out that the length of their report was strictly enforced by journal editors, but it did include two footnotes to Dr. Makovicky's research. None of the referees or editors who reviewed the paper, Dr. Steinhardt said, asked for more attention to the previous research.

Although their work had some elements in common with Dr. Makovicky's, Dr. Steinhardt said in an interview that their research dealt with not one but a "whole sweep of tilings" interpreted through a few hundred examples.

The article quoted two other experts, Dov Levine and Joshua Socolar, physicists at the Israel Institute of Technology in Haifa and Duke University, respectively, as agreeing that Dr. Makovicky deserved more credit. But, the article noted, they said the Lu-Steinhardt research had "generated interesting and testable hypotheses."



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