Event horizons 3

The black hole entropy is a fundamental property of quantized space. The information may be generally attributed to surfaces – the event horizons. In Jacobson’s derivation of Einstein’s equations via Rindler spaces – much like in the case of the “cosmic horizon” of the anti de Sitter space – these event horizons depend on the observer. But there are also event horizons that are shared by pretty much everyone who lives in the Universe – the event horizons of localized black holes that causally separate their finite internal volume from the rest of the Universe.

— Event horizons and thermodynamics: more than an analogy

— Lubos Motl

2013.04.30 Tuesday ACHK

藉口 4.3

原因 5.3

這段改編自 2010 年 4 月 3 日的對話。
















— Me@2013.04.29

2013.04.30 Tuesday (c) All rights reserved by ACHK

Event horizons and thermodynamics

In early 1995, Ted Jacobson found an intriguing way to “localize” the relationship between the temperature and entropy on one side, and the acceleration and areas on the other side. In fact, he derived Einstein’s equations from a well-known thermodynamic equation. See also Einstein’s equations as equations of state.

— Event horizons and thermodynamics: more than an analogy

— Lubos Motl

2013.04.29 Monday ACHK

Trust paper

Trust is like a piece of paper. Once it’s crumpled, it can’t be perfect again.

You can flatten the piece of paper and try to make it as straight as you want. But it will never be the same any more.



2013.04.28 Sunday ACHK

藉口 4.2

原因 5.2

這段改編自 2010 年 4 月 3 日的對話。



1. 你當年「選中大」的理由是,那時李教授在中大任教。

2. 你「有『選中大』這個決定」的其中兩個原因是,「李教授在中大任教」和「你很想上李教授的課」。

3. 而你「入到中大」(獲得中大取錄)的其中兩個原因是,「你做了『選中大』這個決定」和「你考試成績足夠好」。




— Me@2013.04.28

2013.04.28 Sunday (c) All rights reserved by ACHK

Elementary particles, 5

There is another consequence of the UV/IR connection: this connection makes the black hole microstates simultaneously composite as well as elementary.

They’re elementary because they can be thought of as some excitations of a collection of strings and branes. Even if you had a different theory, it would have to be able to calculate the black hole entropy from the number of excited states of “something”. This “something” would play the very same role as strings in perturbative string theory. And differently excited strings must be interpreted as different fields in spacetime – in an effective field theory. The same has to hold for “something” whatever it is.

On the other hand, the number of black hole microstates is so large that there must exist many ways to excite the “something”, some internal degrees of freedom.

— Event horizons and thermodynamics: more than an analogy

— Lubos Motl

2013.04.27 Saturday ACHK

Ethical laws

Except physical and ethical laws, make and follow only your own laws.

— Me@2009.03.11

2013.04.26 Friday (c) All rights reserved by ACHK

Posted in OCD

藉口 4.1

原因 5.1

這段改編自 2010 年 4 月 3 日的對話。






— Me@2013.04.26

2013.04.26 Friday (c) All rights reserved by ACHK

Hardware designers 3

I worked with Mike for a couple of years on Newton. I had tremendous respect for his breadth of understanding of systems, from transistors and batteries all the way up to user interaction. He was a hardware designer who really understood software, too; in my experience, that’s rare.

— kabdib 2 days ago

— Hacker News

2013.04.24 Wednesday ACHK

一步一生 1.1

這段改編自 2010 年 4 月 3 日的對話。






— Me@2013.04.23

2013.04.24 Wednesday (c) All rights reserved by ACHK

Fluctuation theorem

The fluctuation theorem (FT), which originated from statistical mechanics, deals with the relative probability that the entropy of a system which is currently away from thermodynamic equilibrium (i.e., maximum entropy) will increase or decrease over a given amount of time. While the second law of thermodynamics predicts that the entropy of an isolated system should tend to increase until it reaches equilibrium, it became apparent after the discovery of statistical mechanics that the second law is only a statistical one, suggesting that there should always be some nonzero probability that the entropy of an isolated system might spontaneously decrease; the fluctuation theorem precisely quantifies this probability.

Note that the FT does not state that the second law of thermodynamics is wrong or invalid. The second law of thermodynamics is a statement about macroscopic systems. The FT is more general. It can be applied to both microscopic and macroscopic systems. When applied to macroscopic systems, the FT is equivalent to the Second Law of Thermodynamics.

— Wikipedia on Fluctuation theorem

2013.04.23 Tuesday ACHK

Dear Esther, 3

Process, not a state, 10

An event is a change of state.

— Me@2011.01.01

Dying is not just a change of state from one to another.

In order words, dying is not a single event, but a lifelong process.

In a sense, your whole life is already a near-death experience. 

— Me@2010.12.31

— Me@2013.04.22

2013.04.22 Monday (c) All rights reserved by ACHK

超世 5

這段改編自 2010 年 6 月 29 日的對話。








— Me@2013.04.21

2013.04.22 Monday (c) All rights reserved by ACHK

The Killer Question

And if the Labs leadership believes a researcher is too attached to an idea in the exploration phase, they’ll make sure that individual isn’t involved in the company’s founding.

Why? Because in Afeyan’s view, entrepreneurs who get attached become afraid to ask the “killer question” that will expose the flaw in their idea. At Labs, where the idea is to get to No as quickly as possible, that’s not OK.

— No Founders Required: How Flagship Starts Companies

— Walter Frick

2013.04.21 Sunday ACHK

惜此際 3.2

這段改編自 2010 年 4 月 3 日的對話。






— Me@2013.04.20

2013.04.20 Saturday (c) All rights reserved by ACHK