Author Archives: rpflee

No reading

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Many people don’t read nor listen because they don’t want other people minds “invade” theirs.

In short, they are dumb.

— Me@2012.08.07

ARIADNE
Why are they looking at me?

COBB
Because you’re changing things. My subconscious feels that someone else is creating the world. The more you change things, the quicker the projections converge on you.

ARIADNE
Converge?

COBB
They feel the foreign nature of the dreamer, and attack-like white blood cells fighting an infection.

ARIADNE
They’re going to attack us?

COBB
Just you, actually.

— Inception

2012.08.08 Wednesday (c) All rights reserved by ACHK

個人客觀科學 1.2

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真相客觀程式 3.2

這段改編自 2010 年 3 月 27 日的對話。

（安：那為什麼「科學」可以百分百「以事實為中心」，而其他類型的學科卻不跟隨？）

那只是「字眼定義」，或者「科目命名」的問題。凡是肯百分百「以事實為中心」的學科，都已經被我們稱之為「科學」，歸類成「科學」了。

— Me@2012.08.07

2012.08.07 Tuesday (c) All rights reserved by ACHK

Wheeler–DeWitt equation, 5

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In the new paper, this concept is taken very seriously. “The wave function” is interpreted as nothing else than the Hawking-Hartle wave function of the Universe. You know, the Hawking-Hartle wave function is something like a wave functional of quantum gravity that solves the Wheeler-deWitt equation (a sophisticated definition of the quantum equation

    H.psi = 0

that is appropriate in general relativity but whose exact meaning requires a working quantum theory gravity, i.e. it requires string theory). The Hawking-Hartle wave function is a functional of the fields of quantum gravity on S^3, if you allow me to deal with the “most realistic” example, and this functional may be calculated as the path integral of quantum gravity defined in the ball B^4 inside this S^3, with the right boundary conditions at the sphere S^3. The Hawking-Hartle state is then the functional of these boundary conditions.

— Lubos Motl

2012.08.06 Monday ACHK

Eleven dimensions of color

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Diclaimer: I have full-color vision, but with color blindness there are (roughly) two dimensions of color, whereas most people have three (and a black and white photograph has one). What this means is that with 1D color, you can sort all of the colors you see into a line — dark to light. With 2D color, you can sort all of the colors you see on a flat plane. With 3D color, you require stacking colors.

Now, there’s plenty of animals out there that have more than 3 dimensional color (they have more than 3 types of cone cells). So two colors that look the same for a normal person will look completely different for an animal. Some octopi have eleven dimensions of color! To them almost every human would be severely colorblind.

…

It’s thought that some people might be tetrachromats. They have 4 types of cone cells because of a genetic mutation. There’s still some questions on how this extra information is processed by the brain, but there’s a chance that for these people almost everyone else seems colorblind. They are able to distinguish two colors that everyone else cannot. This also means that television won’t reproduce colors correctly for them, and it won’t look natural.

— Xcelerate 1 day ago

— Hacker News

2012.08.04 Saturday ACHK

個人客觀科學

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真相客觀程式 3

這段改編自 2010 年 3 月 27 日的對話。

（安：一般人以為，只有在學校裡，才會研習科學；只有物理、化學、生物等，才算是科學。其實，即使是日常的個人生活，很多時也很需要運用到，從科學研習中，提煉出來的「科學精神」和「科學方法」。

例如，我需要研究「阿安科學」。例如，我發現，如果在之前一晚，十一時就睡覺，早上六時成功起床的機會高達 90%；如果我遲過深夜十二時才睡，早上六時成功起床的機會則近乎 0%。

根據這個數據，我可以完善我的生活規劃。）

無錯。其實，所謂「科學」，就是「以事實為中心」。大部人的生活，也不是以事實為中心，而是以情緒、感覺 和 喜好為中心，導致枉費一生。

「科學」比其他類型的學科，有較明顯的進步，較高速的發展，是因為她堅持「以事實為中心」。如果你可以做到「不樂觀」和「不悲觀」，而保持客觀的話，你就已經是跟從「科學法度」。你的人生，將會有科學級數的進步發展。

所以，所有人都應該受科學的訓練。科學教育的最重點，不在於培養未來的科學家，而在於潛移默化，使大部分未來人，也習慣「以事實為中心」。

— Me@2012.08.03

2012.08.03 Friday (c) All rights reserved by ACHK

Wheeler–DeWitt equation, 4

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Lumo ‧ 7 years ago

Dear Anonymous,

I agree that loop quantum gravity may also be viewed as an attempt to make sense out of the WDW equation. Unfortunately it is not a consistent or successful attempt – simply because the Hamiltonian constraint can’t be defined. (In fact, even the physical Hilbert space is not well-defined.) See an older article “A very meaningful paper on loop quantum gravity”.

All the best
Lubos

Anonymous ‧ 7 years ago

But even the Wheeler-deWitt equation needs to be regularized!

Lumo ‧ 7 years ago

That’s right. This is why you need string theory to transmute the WDW equation from a heuristic speculation to a meaningful law of physics.

— Lubos Motl

2012.08.02 Thursday ACHK

Cute cat theory of digital activism

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The cute cat theory of digital activism is a theory concerning Internet activism, Web censorship, and “cute cats” (a term used for any low-value, but popular online activity) developed by Ethan Zuckerman in 2008. It posits that most people are not interested in activism; instead, they want to use the web for mundane activities, including surfing for pornography and lolcats (“cute cats”). The tools that they develop for that (such as Facebook, Flickr, Blogger, Twitter, and similar platforms) are very useful to social movement activists, who may lack resources to develop dedicated tools themselves. This, in turn, makes the activists more immune to reprisals by governments than if they were using a dedicated activism platform, because shutting down a popular public platform provokes a larger public outcry than shutting down an obscure one.

— Wikipedia on Cute cat theory of digital activism

2012.08.01 Wednesday ACHK

Good runners

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Good runners still get tired; they just get tired at higher speeds.

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If you feel exhausted, it’s not necessarily because there’s something wrong with you. Maybe you’re just running fast.

– Paul Graham

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2010.03.13 Saturday ACHK

Wheeler–DeWitt equation, 3

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Some of these questions are answered by string/M-theory in its current state; some of these questions were approximately answered even by QFT tools before string theory; some of these questions remain open.

For example, the Wheeler-DeWitt equation (together with its various solutions such as the Hartle-Hawking state) mostly belongs to the third category (the things not yet established). It’s the equation HΨ=0, expressing the idea that the Hamiltonian constraint in GR actually encodes the full evolution in time, something that is possible due to the ambiguous meaning of the word “time” in diffeomorphism-symmetric theories. To solve it, one must first define his own time, by linking it to some coordinate-independent evolving quantity, and so on.

— answered Oct 25 ’11 at 6:50

— Lubos Motl

2012.07.31 Tuesday ACHK

Spinors, 2

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Spinors are objects with a spinor index and in some very particular sense, a spinor index is exactly one-half of a vector index. So the generalized tensors may have either an integral number of indices or they may also have a half-integral number of indices! In a very clever sense, a spinor is a square root of a vector in the same sense as a vector is a square root of a tensor with two indices. How is it possible that we may break letters (indices) into pairs of letters?

— Why are there spinors?

— Lubos Motl

2012.07.30 Monday ACHK

Wheeler–DeWitt equation, 2

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This wave function contains all of the information about the geometry and matter content of the universe.

In fact, the principle of general covariance in general relativity implies that global evolution per se does not exist; the time t is just a label we assign to one of the coordinate axes. Thus, what we think about as time evolution of any physical system is just a gauge transformation, similar to that of QED induced by U(1) local gauge transformation , where plays the role of local time.

— Wikipedia on Wheeler–DeWitt equation

2012.07.29 Sunday ACHK

Backward compatibility, 4

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Because the real cost of compatibility is not in the hacks. The hacks are small potatoes. Most hacks are just a few lines of code (sometimes as few as zero), so the impact on performance is fairly low.

No, the real cost of compatibility is in the design.

If you’re going to design a feature that enhances the window manager in some way, you have to think about how existing programs are going to react to your feature. These are programs that predate your feature and naturally know nothing about it. Does your feature alter the message order? Does it introduce a new point of re-entrancy? Does it cause a function to begin dispatching messages that previously did not? You may be forced to design your feature differently in order to accommodate these concerns. These issues aren’t things you can “take out”; they are inherently part of the feature design.

— The Old New Thing

— Raymond Chen

2012.07.28 Saturday ACHK

The Dark Knight Rises, 2

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The Dark Knight Rises (2012 movie): At the end, why does Batman give Gordon such a cryptic clue, rather than just revealing his face?

He either wants Gordon to know, or he doesn’t. Why does he take the path where Gordon may or may not work it out?

Siddharth Bhandari, Batman Fanatic

You just killed all the emotion when you considered it a cryptic clue. This scene had such beautiful emotions.

A hero can be as simple as a man putting his coat around a little boy’s shoulders and reassuring him the world hadn’t ended yet.

See the beauty in this quote. He’s not just giving him a clue but implying that Gordon has been a hero for him all these years.

— Quora

2012.07.28 Saturday ACHK

Weinberg–Witten theorem

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In theoretical physics, the Weinberg–Witten theorem (WW), proved by Steven Weinberg and Edward Witten, states that massless particles (either composite or elementary) with spin j > 1/2 cannot carry a Lorentz-covariant current, while massless particles with spin j > 1 cannot carry a Lorentz-covariant stress-energy. The theorem is usually interpreted to mean that the graviton (j = 2) cannot be a composite particle in a relativistic quantum field theory.

Theories where the theorem is inapplicable

Superstring theory

Superstring theory defined over a background metric (possibly with some fluxes) over a 10D space which is the product of a flat 4D Minkowski space and a compact 6D space has a massless graviton in its spectrum. This is an emergent particle coming from the vibrations of a superstring.

— Wikipedia on Weinberg–Witten theorem

2012.07.27 Friday ACHK