形形色色（8）
1、最近得知，加州理工学院的Andrew Lange自杀身亡。
Lange是物理学家、宇宙学家，BOOMERang实验的领导人之一，出生于1957年，是加州理工数学天文物理部主任。
台湾大学黄伟彦教授领导的COSPA小组从1999年开始定期举办研讨会，我在2000年得知BOOMERang的实验结果，那时还有MAXIMA等实验。是这些关于CMB各向异性的重要实验让我下决心进入宇宙学领域。我私下曾感谢黄伟彦教授，他的小组直接对我施加了影响，当然，去世的Lange则间接地对我施加了影响。
加州理工校长Jean-Lou Chameau说：
It is with great sadness and regret that I must report to you the death of Professor Andrew Lange, a valued member of the Caltech faculty. Andrew was found this morning off campus, and it appears that he took his own life. Among the most difficult things that people have to deal with in life are tragedies of this sort, especially when they affect people that we know and care for; and Andrew was such a well-known, well-respected, and well-liked member of our community that many of us will be deeply affected.
Andrew came to Caltech in 1993 and was most recently the chair of the Division of Physics, Mathematics and Astronomy. He was a truly great physicist and astronomer who had made seminal discoveries in observational cosmology.
Andrew was a valued colleague and a close friend to many of us. His death is a source of great sadness to us all and our deepest sympathy goes out to his family, friends, and colleagues, all of whom mourn his loss.
We know this tragic news will come as a shock to everyone — faculty, staff, and students alike, even those of you who knew that Andrew had been struggling with personal issues. Many of us feel the need in times like these to reach out and seek help in dealing with the shock, and I urge anyone who wants help to seek it from family members, friends, faculty, and/or professional counselors. This is not only a reasonable thing to do, it is an important thing to do. I want to emphasize in particular that counselors are always available, 24-hours a day. Students should call the Counseling Center at 626-395-8331, while faculty, staff, and postdocs, should call the Staff and Faculty Consultation Center at 626-395-8360. In addition, the Counseling Center will be open on Saturday and Sunday from 10-3pm.
博客Jennifer Ouellette说
The only way I can think to honor Lange is to tell you a bit more about his most famous work. BOOMERang stands for Balloon Observations Of Millimetric Extragalactic Radiation and Geophysics, and it’s essentially a balloon-borne telescope designed to make measurements of the cosmic microwave background radiation — the “afterglow” of the Big Bang that still pervades our universe. The first flight, in 1997, concentrated on North America, while two subsequent flights in 1998 and 2003 circled the South Pole. Maps
Based on this data, the BOOMERang team made the most detailed map of temperature fluctuations in the CMB — at least as of April 2000, when the first results were announced.
……
BOOMERang’s exciting results were the first “to resolve the structures in the CMB, allowing us to ’see’ structures that predate even the first star or galaxy in the universe,” Lange said in an interview with the European Space Agency in 2001. But he was always looking forward to the next experiment — in this case, the Planck satellite that launched last spring. Planck’s instruments have even better resolution than BOOMERang, capable of measuring many more frequencies in the CMB, and it will cover the entire night sky, instead of just select regions. “Planck will be revolutionary!” Lange declared in that 2001 ESA interview. It’s a tragedy that he didn’t live to see the revolution in action.
2、关于Verlinde的熵力
Lee Smolin最近写了一篇文章，声称可以从loop gravity推导出牛顿引力。对此，Erik Verlinde评论道：“Lee Smolin paper to appear getting emergent gravity from loop quantum gravity. I don’t understand the logic: explain gravity from gravity??”
我在理论所的报告中就说过，会有很多研究Verlinde的想法的人，而且一开始估计有60%的文章是错的，Smolin可能是错的之一，至少是trivial的。我没有看他的文章，但我有这种感觉。
毫无疑问，Verlinde的想法将刺激人们去获得更多的有意思的结果，而且我个人感到这个想法本身或延伸会导致一些令人意料不到的结果。目前，似乎还没有任何意料不到的结果被发表。我们只需要一点点耐心。
New Scientist对Verlinde的工作做了报道，The entropy force: a new direction for gravity，其中说：
Verlinde’s paper has prompted praise from some physicists. Robbert Dijkgraaf, a prominent mathematical physicist also at the University of Amsterdam, says he admires the elegance of Verlinde’s concepts. “It is amazing no one has come up with this earlier, it looks just so simple and yet convincing,” he says.
The jury is still out for many others. Some believe that Verlinde is using circular reasoning in his equations, by “starting out” with gravity. Others have expressed concern about the almost trivial mathematics involved, leaving most of the theory based on very general concepts of space, time and information.
Stanley Deser of Brandeis University in Waltham, Massachusetts, whose work has expanded the scope of general relativity, says Verlinde’s work appears to be a promising avenue but adds that it is “a bombshell that will take a lot of digesting, challenging all our dogmas from Newton and Hooke to Einstein.”
Verlinde的老师’t Hooft的评论也是正面的，他认为，这个工作至少比弦论来得更物理。
2010年1月26日 4:55:32
我记得是Ehrenfest, 并非Erenfest。也许我错了，请博主查一下。
2010年1月26日 9:28:45
李老师，引力作为熵力的假设会导致和经典理论不一样的预言吗？只有这样才能把它和过去的理论进行鉴别吧。
2010年1月26日 11:56:25
abada贴的连接“浪费”了我一上午的时间，浏览了一遍曹天元写的量子物理史话，呵呵。
我看的新鲜的是，量子论的多种解释。很新鲜，看完了之后才知道原来自己一直是鸵鸟派的，对解释不闻不问。
2010年1月26日 12:58:42
Both pmo and naoc folks met Andrew a year ago, and a few naoc folks
just met him again recently and are supposed to go to Caltech to see
him again in a few days. Such a saddened tragedy, incomprehensible…
2010年1月26日 13:09:15
随笔：
你是对的，谢谢。
adam：
会，见今天我和王一的文章：
http://arxiv.org/abs/1001.4466
2010年1月26日 13:19:12
深夜一游，你们聊得很high
2010年1月26日 13:23:38
pmo：
:(
math苹果：
加拿大现在不算深夜。也许你在美国？我更信任google
2010年1月26日 16:43:38
Lee Smolin最近写了一篇文章，声称可以从loop gravity推导出牛顿引力。对此，Erik Verlinde评论道：“Lee Smolin paper to appear getting emergent gravity from loop quantum gravity. I don’t understand the logic: explain gravity from gravity??”
——————————————————————————–
Smolin’s motivation is important at least to loop quatum gravity (LQG) community. One big problem of LQG is whether it is really a quantum theory of gravity, which has a limit with an emergent spacetime described by the usual general relativity with a non-relativistic limit being the Newton’s gravity? It was hoped so but has been never demonstrated to be so. This was because in the historic development of LQG, the variables chosen for quantizing General Relativity have been extended several times, and the formalism and mathematics became so abstract, complicated and far away from the gravity we have been familiar, so people have lost track of the original Einsten’s theory of gravity. This is why an argument or a demonstration of emergent Newton’s law would strengthen the case for taking LQG to be a candidate of a quantum theory of gravity. L. Smolin is an insider, so he knows the existence of the problem and the importance of such demonstration.
E. Verlinde may not care about LQG, so he made his criticism. But anyway L. Smolin has argued that several important ingredients for Verlinde’s argument have existed in LQG already, and are no longer needed as conjectures, THOUGH the existence of emergent classical spacetime is still a key assumption in Smolin’s paper . I expect that their disargreement would continue: Verlinde emphasizes that the entropic-force point of classical gravity would lead to exploration of new ways to understand gravity, while Smolin seems to imply that LQG already contains Verlinde’s argument, so LQG is perhaps the right framework to understand gravity and nothing new is necessary. In this sense E. Verlinde is more radical, while Smolin is more conservative, though both agree that gravity is thermodynamic in nature.
2010年1月26日 17:29:50
随感：
谢谢comments，我马上要走，回来仔细看。
2010年1月26日 18:03:40
43 楼 Erratum （或请博主代为修改）
through the existence of emergent classical spacetime is still a key assumption in Smolin’s paper
should be
THOUGH the existence of emergent classical spacetime is still a key assumption in Smolin’s paper
2010年1月26日 19:01:06
关于Verlinde的文章，一些质疑它的人，似乎混淆了两种不同的逻辑概念：
1）循环论证。循环论证当然是错误的论证，但这种论证本质上属于“A→A”的论证过程。
Verlinde的文章应该不属于这种情形。
2）由数理逻辑我们知道，对于一个理论系统，我们可以把它的某些相互独立的定理“升级”为公设（公理），使得原来的某些公设（公理）自动地“降级”为定理，这样得到的理论系统与原来的完全等价。这种过程属于把“A→B”变成“B→A”的过程，与上述“A→A”的循环论证过程有着本质的区别。
感觉Verlinde的文章更有可能属于情形2)。特别是，如果有一天人们发现，由引力理论可以推导出全息理论，那么Verlinde的文章，如果没有带来比传统理论更多或者不同的东西，则无疑相当于把“A→B”变成“B→A”的过程。
2010年1月26日 20:26:07
随感：
虽然我还看Smolin的文章，我基本同意你的看法，loop gravity一直以来在证明低能状态下是否能够回到Einstein理论遇到麻烦-也就是说continuum limit是否存在。Lee的工作也许是关键的一步。
星空：
同意。
2010年1月26日 22:11:45
在美国，深夜一点算深夜吧，喝了咖啡睡不着。
学术的东西讨论最好，在争论中将理论明了
2010年1月26日 23:07:26
math苹果：
算是深夜吧
2010年1月27日 13:03:15
天妒英才
2010年1月27日 14:55:09
今天早上一看，WMAP 7-year 出来了。这回出来偷偷摸摸的，可不像 5-year 那样做足铺垫钓人眼球，呵呵。跑来李老师这里看，居然没有动静。李老师或者哪位大侠 comment 一下吧？
2010年1月27日 14:57:31
WMAP：
王一昨天跟我说Komatsu在facebook已经说了-可惜facebook被封了。我昨天大略看了两篇文章。见我新的博文。
2010年2月20日 15:03:33
“李淼
2010年1月24日 23:25:17
多云转晴：
因为量子力学在热力学中不重要，至少在这个推导中不重要。 ”
在这个推导中重不重要我还不清楚，但热力学给我的感觉是过于强调随机性、无规无序性，而忽视热运动中信息传递和各组成部分之间的相干性。近年来Quantum Hologram（QH）的发展认识到了热辐射中包含着一个物体的全息信息。QH与从黑洞热力学中发展出来的全息原理不是一回事，尽管两者肯定是有深层联系的。QH研究的基本现象是宏观物体发射/吸收能量这样的基本过程（也是量子力学诞生时的一个接生婆），用到的数学工具是标准量子力学的Heisenberg群和全息照相原理，但得到的结论却不同寻常–所有宏观物体在发射/吸收能量这样的基本过程中都在发射出的能量子的相位关系中携带了此宏观物体的事件历史的信息，这个理论是一个叫Walter Schempp的德国人在研究MRI成像过程中提出的。这是我在网上搜到的（应该就是）这个人写的关于QH的初始论文：http://www.ima.umn.edu/preprints/Aug91Series/860s.pdf
论文较长而且有许多对MRI成像技术发面的内容，我还没读完。
还有大力提倡QH的一个叫做Edgar Mitchell的人的网站，里面有更多对QH的文字介绍：http://www.quantrek.com/index.htm
QH是量子力学在宏观尺度上的普遍的直接的表现，普遍存在于热辐射这样的基本现象中，其重要性是不言而喻的。如果热辐射都包含着辐射体的事件历史信息是普遍的，那么黑洞蒸发过程也没有理由例外，那么黑洞蒸发过程中的information paradox也就不是个paradox了，信息存储于热辐射中。黑洞热力学已经表现出了热、引力、量子力学的不可分割性，这些观念都指向了对真空的理解。因此，热力学在根本上是与量子力学联系在一起的，热力学中的“无规”、“随机”这样的观念需要修正，甚至统计规律、量子力学中出现的概率性本身也许都会有个更基本的解释。
2010年2月20日 17:00:43
查了一下，Quantum Hologram资料很少， 知道的人也不多，可能是一个很冷僻的研究方向，似乎只算是一家之言，未得到学界主流认可。
2010年2月20日 18:07:25
lixkyx ：
知道的人确实很少，可能是因为QH不是搞纯理论的人做出来的，所以理论界可能知道的人不多，搞NMR、MRI成像的
，搞生物的可能知道的人就多一些，QH中信息的非局域性还被用于解释超常心理学中的现象，尽管还是很初等的尝试。目前我所了解的最先做这方面工作的就是Walter Schempp和Ernst Binz这两个人，后来又有人跟进或者将其用到了其他领域。QH是非常普遍基本，而且有实验验证做基础。
另外，对DNA的研究也有非常有趣的进展，比如Phantom DNA effect，有兴趣的可以去了解一下–DNA的工作方式很像一个全息投影仪。