Holographic principle, 7

Thus, the holographic correspondence is not just a wild new possibility for a quantum theory of gravity. Rather, in a fundamental way, it connects string theory, the most studied approach to quantum gravity, with theories of quarks and gluons, which are the cornerstone of particle physics.

— The Illusion of Gravity

— Juan Maldacena

2012.08.31 Friday ACHK

The Tree of Knowledge

Sorrow is Knowledge: they who know the most
Must mourn the deepest o’er the fatal truth,
The Tree of Knowledge is not that of Life.

— LORD BYRON, Manfred

We need both the Tree of Knowledge and the Tree of Life.

Both are crucial.

— Me@2012-08-31 9:51:11 AM 

2012.08.31 Friday (c) All rights reserved by ACHK


The accuracy of the measured value of G has increased only modestly since the original Cavendish experiment. G is quite difficult to measure, as gravity is much weaker than other fundamental forces, and an experimental apparatus cannot be separated from the gravitational influence of other bodies. Furthermore, gravity has no established relation to other fundamental forces, so it does not appear possible to calculate it indirectly from other constants that can be measured more accurately, as is done in some other areas of physics.

— Wikipedia on Gravitational constant

2012.08.30 Thursday ACHK


Angels can fly because they take themselves lightly; devils fall because of their [own] gravity.

– G. K. Chesterton

In order to develop yourself and transcend yourself, you have to decentralize yourself.

— Me@2011.11.04

2012.08.30 Thursday (c) All rights reserved by ACHK

蘋果 與 Apple

Electric Field and Electric Potential

這段改編自 2010 年 6 月 9 日的對話。

千萬不要以為,「electric field」(電場)和「electric potential」(電勢)是兩種不同的東西。實情是,它們只不過是,描述同一類物理現象的兩種不同的語言。換言話說,同一個電學現象,你既可以用「electric field」來解釋,亦可以用「electric potential」來說明。


This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

這個現象,一方面,你可以用「electric field」來解釋:因為 electric field lines(電力線)向右指,而正電荷的天性是,跟著電力線的方向走,所以該正電荷會向右走。

另一方面,你亦可以用「electric potential」來解釋:因為左邊的 electric potential 高於右邊,而正電荷的天性是,由高 potential 的地方,流向低 potential,所以該正電荷會向右走。

記住,「electric field」(電場)和「electric potential」(電勢)不是兩種東西,而是同一種東西的兩種語言。就正如「蘋果」和「apple」,它們是同一種東西的兩種語言。至於用哪一種語言,則要視乎情況而定,哪一種比較方便就用哪一個。例如,見到中國人時,就用「蘋果」;見到英國人時,則用「apple」。

— Me@2012.08.30

2012.08.30 Thursday (c) All rights reserved by ACHK


Charge (physics), the susceptibility of a body to one of the fundamental forces

— Wikipedia on Charge

2012.08.29 Wednesday ACHK

2.3.1 What is statistics

Data Statistics Information Studying Knowledge Aging Wisdom Dying Next What is Next?

Data and Information

First, differentiate data and information: Data is raw. Data have no meaning. Information is processed data. Information has meaning. The process to transform data to information is statistics.

Information and Knowledge

Information is higher-level than data. What is higher than information?


What is the process of transforming information to knowledge?

Studying. (or AI for computers)

If you want a lot of mathematics information, just buy 50 maths books, then you get a lot of information. But if you want a lot of mathematics knowledge, you have a lot of hard work to do.

Knowledge and Wisdom

After knowledge, what is next? Wisdom.

What is the process of transforming knowledge to wisdom?


If you want to have a lot of knowledge, buy a lots of books, read them and read them well. But if you want to have a lot of wisdom, you need to live your life for a long time or a long long time.

Wisdom and Next

Is there anything higher than wisdom? If yes, what is the process to go from wisdom to there?

Dying. (This can be trivial. When you age to certain extent, you die.)




2008.06.11 Wednesday (c) All rights reserved by ACHK

卡拉 OK, 3

這段改編自 2010 年 3 月 27 日的對話。



— Me@2012.08.29

2012.08.29 Wednesday (c) All rights reserved by ACHK

Decoherence and the Collapse

An important technical difference between decoherence and the collapse of the wave function is that decoherence actually doesn’t decide which result will be measured. It just diagonalizes the density matrix to diag(p1,p2,…,pN) where p_i then play the role of the probabilities that the individual preferred basis vectors will be detected. Because the information about the relative phases is getting quickly lost, the off-diagonal elements rapidly converge to zero. But decoherence never transforms the density matrix with the many p’s to something like (0,0,1,0,…,0). Never, ever. Quantum mechanics remains the only player here and its predictions remain and will always stay probabilistic. One can never and one will never restore determinism and decoherence doesn’t try to do anything of the sort.

— Lubos Motl

2012.08.28 Tuesday ACHK

Quantum Field Theory

Such QFTs arise naturally in generalizations of QCD from three colors to a larger number of colors, N.

— Solving quantum field theories via curved spacetimes

— Igor R. Klebanov and Juan M. Maldacena

2012.08.27 Monday ACHK

Take over the world

At some point, Graham will ask his favorite question: “What’s your long-term plan to take over the world?” Eventually the Westclox buzzer goes off, Livingston snaps a picture of the candidates, and the next group is ushered in.

— Y Combinator Is Boot Camp for Startups

— Steven Levy

2012.08.26 Sunday ACHK

Read more slowly, 3

Like most individuals, and probably, most mathematicians outside his field, I do not deeply understand much of Thurston’s work. But he did have a rather large impact on my life insofar as a paragraph of his has stayed with me several years (not many do, I’m afraid), and has been my reminder to slow down whenever I find myself saying “psh, that was easy, all I had to do was browse through the documentation”:

I prided myself in reading quickly. I was really amazed by my first encounters with serious mathematics textbooks. I was very interested and impressed by the quality of the reasoning, but it was quite hard to stay alert and focused. After a few experiences of reading a few pages only to discover that I really had no idea what I’d just read, I learned to drink lots of coffee, slow way down, and accept that I needed to read these books at 1/10th or 1/50th standard reading speed, pay attention to every single word and backtrack to look up all the obscure numbers of equations and theorems in order to follow the arguments.

If a Fields medalist needed to slow down to read some maths, I can slow down to really understand whatever it is that I’m doing. And when I tell myself “I’ve learned that already!” I stop and ask whether I learned it at a “1/50th pace.”

— kevinalexbrown 1 day ago

— Hacker News

2012.08.24 Friday ACHK

Normal Reaction


這段改編自 2010 年 6 月 9 日的對話。

為什麼會有 normal reaction(法向力)?


Normal reaction 歸根究底,來自電力(electric force)。

— Me@2012.08.24

2012.08.24 Friday (c) All rights reserved by ACHK

Gauge symmetry, 4

One must distinguish gauge symmetries and global symmetries. A gauge symmetry is a redundancy of a description, not a property of a physical system.

— Lubos Motl

2012.08.23 Thursday ACHK