Wormholes and nonlocality


  Dave Bacon在blog中写了篇有意思的文章:“Wormholes”。他提到,虫洞是由爱因斯坦和Rosen最早提出的。 在这篇论文中,爱因斯坦和Rosen实际上是希望找到一个广义相对论的特解,能够对统一量子理论和广义相对论有所帮助。也就是说“Under these circumstances it does not seem superfluous to raise the question as to what extend the method of general relativity provides the possibility of accounting for atomic phenomena.” 实际上他们发现了”一座桥”,能够连接空间中的两个切片。在论文中,这座”Einstein-Rosen 桥”也是一个中性粒子,就象中子或者中微子那样。
不过Bacon的日志中最让我感兴趣的是他提到,这个Einstein-Rosen桥实际上与量子力学中的Bell不等式有联系。John Bell证明了类空间隔的量子系统间的关联是无法用它们的局域自由度来描述的。Bacon认为爱因斯坦可能已经考虑过Bell的这个问题。他不是把 Bell的理论看做是经典的实在论(reasoning)无法处理量子理论,而是认为“量子理论是广义相对论拓补扩展的一个推论”。我理解这句话是说:所 谓非局域性(nonlocality)背后是不是存在这这么一个广义相对论的Eintein-Rosen桥,而从外部观测,类空间隔的量子系统间还有着关 联。真是一个很有意思的想法!
APS上还有对Einstein-Rosen桥的一个总结性的文章:”The Birth of Wormholes“,我读了读,很不错,推荐大家去看看,了解一下虫洞研究的历史。

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The Future of Computation


A very interesting lecture(quant-ph/0503068) was posted to the arxiv recently. The abstract of it says:

“The purpose of life is to obtain knowledge, use it to live with as much satisfaction as possible, and pass it on with improvements and modifications to the next generation.’’ This may sound philosophical, and the interpretation of words may be subjective, yet it is fairly clear that this is what all living organisms–from bacteria to human beings–do in their life time. Indeed, this can be adopted as the information theoretic definition of life. Over billions of years, biological evolution has experimented with a wide range of physical systems for acquiring, processing and communicating information. We are now in a position to make the principles behind these systems mathematically precise, and then extend them as far as laws of physics permit. Therein lies the future of computation, of ourselves, and of life.

In this article,Life is viewed as natural computer. During bilions of years evolution, life gets the best way to recieve and operate data from environment. The author illustrate the several basic processed during computation. In future, the computer will use less resources to get more tolerance against the errors and faster operation.

In my opinion, the most valuable part of this article is the very clear explaination of quantum compution in the mixed context of computation science and physics. The article talked all type of computation, including quantum computation. After reading it, I catch the links between computer science and physics.

Gross’s quesions


Recently, David J. Gross gave a lecture The Future of Physics in ITP, Beijing. Today I downloaded the video file of his lecture. I watched the lecture and found Gross asked many interesting Questions. In this lecture Gross talked about the future of physics in 25 years and discussed many open questions, such as the beginning of universe, the formation of the stars, dark energy existence, and so on. Here I list some questions I think most interesting.

  • Will Quantum Computer be quiet or deaf?
  • Can the theory of evolution be quantitative and predictive?
  • Can we tell the shape of an organism by looking at genome?
  • Will computers replace analytic technology? If we will change the way we train physicist?
  • When will the computers become creative physicist? How do we train them?

btw: I happily found that I can understand the lecture for 90%.

update: I found the official website that offers this lecture’s video.

I don’t know


As a Chinese physics student, Samuel CC Ting(丁 肇中) is one of my most respective physicists. Three years ago, I was lucky to have a chance to listen to the lecture given by Samuel CC Ting. The words of the lecture most impressed me was “I don’t know”. When asked whether dark energy exits or not, extro-space life exists or not and so on, the only rely from Ting was “I don’t know”. In fact, when ased those uncertain or unfamiliar questions, Ting usually said “I don’t know”.I like this reply.

Scientist is nod god. The more you know, the more you know you don’t know. Ting’s father is a schoolfellow of Jiaotong Univ(now becoming five universities: XJTU, SJTU, NJTU, SWJTU and NCTU) and hired by Jiaotong Univ in 1940s. His classmate Tsien Hsue-shen(钱 学森 ) is a famous aerodynamicsist and makes great contribution to the birth and development of missile in China. He is honored as people scientists by government.

Besides his contribution, he also made a big mistake outside his major. In the year near 1959, he wrote a paper to prove that the rice harvest every Chinese unit of area unit mu (666.7 square metres) can be as high as 150000 kg. Abviously it was wrong. But because Tsien is a famous scientist, the leader of government believed it. This is one reason which caused the famine from 1959 to 1961 in China. If Tsien could say I don’t know, the damage of famine may be less.

Actually speaking, we Chinese tend to say “I know”, no matter how little we know it. But as a scientist, we must do as CC Ting, say “I don’t know” if we don’t know exactly. Do not be another Tsien Huen-shen!