Simcity, 2

Posted on December 29, 2019 by rpflee

d_2019_12_29__15_35_29_PM_

I bought this SimCity 2000 box in 1995. It was the first time I went to a big computer centre (mall).

At the first glance, I thought that it was sold at the price 800 HKD, which I could not afford. Luckily, the price label was actually NT800, which meant 800 New Taiwan Dollars.

So I could buy it at 200 Hong Kong Dollars.

— Me@2019-12-29 03:42:26 PM

scmutils, 2

Posted on December 29, 2019 by rpflee

The original method of setting up Emacs for scmutils does not work anymore if you uses the newest (August 2019) version of scmutils, because its installation directories are not the same as those in the previous version.

Either use an older version of scmutils in order to follow the previous instructions for setting up Emacs for scmutils, or give up using Emacs for scmutils for the time being.

Using command line is the best way to go, so far.

Do not use the Edwin editor, since you cannot easily run, edit, or copy existing lines of code, unless you are familiar with it. I do not like it anyway, because after all, it does not provide syntax highlighting.

— Me@2019-12-28 07:50:32 PM

Physics PageRank

Posted on December 27, 2019 by rpflee

PageRank 7

Physics has a high PageRank among fields of knowledge.

— Me@2011.07.28

— Me@2011.08.12

Principal details

Posted on December 27, 2019 by rpflee

Teaching hint:

Try to integrate all the details into one big principle.

— Me@ < 2008-06-20

Ken Chan 時光機 3.2

Posted on December 27, 2019 by rpflee

有一次，他在晚上十一時多，回覆我的致電。他說先要關掉實驗機器。他回答了我的物理題目後，我順道問他讀書方法，訴苦說，來不及溫習應試。

你識得咁樣問，幾好喎。（你懂得那樣問，相當好。）

他的意思是，欣賞我有上進心。

他答了我很久，花了他大概一個小時多，非常抱歉。

他講了一些東西。以下不依次序。

中五（會考年）每天溫習五、六小時，很正常的事。

你化學不好，為什麼不補化學？

我答：補得太多的話，我沒有足夠溫習。

他說：咁又係。（那又是。）

他問我附加數學有哪些課題。

如果讀了那幾個課題就不會有大問題。

他暫時不表達立場地，問我喜不喜歡生物科。我答不太喜歡後，他才和應。

係囉，成日有好多嘢背。都唔知背嚟做乜。（是的，時常有很多東西要背。都不知背來為了什麼。）

我又問中六時，應該選化學還是應用數學。（其實我一早就想選，應用數學。）我問他當年是讀什麼科。他說他預科時毋須二選一。

我兩科也有讀。

他中六預科時修讀的科目是，英文、純數學、應用數學、物理和化學，共五科。

我那時沒有中文必修科。［所以毋須犧牲，化學或應用數學。］

我又講到另外一些東西。我現在不記得是什麼。他答我：

你完成了力學的 MC（多項選擇題）沒有？

我大概回答，雖然完成了，但仍然沒有把握。（那些 MC，總共花了我三個月，沒有可能重新做一次。）

你試試逐題看一看，不需做多一次，只需嘗試對自己，講一講該題的做法。如果講得出，就為之學懂了該題。如果講不出，才詳細研究該題。

他答了我很久，阻礙了他的工作，十分抱歉，萬分感激。

— Me@2019-12-26 06:59:01 PM

1984

Posted on December 25, 2019 by rpflee

d_2019_09_27__00_14_03_AM_

<= 1984

Quick Calculation 13.1

Posted on December 25, 2019 by rpflee

A First Course in String Theory

Verify that

$\displaystyle{\left[ \bar L_m^\perp, x_0^I \right] = - i \sqrt{\frac{\alpha'}{2}} \bar \alpha^I_m}$ ,

$\displaystyle{\left[ L_m^\perp, x_0^I \right] = - i \sqrt{\frac{\alpha'}{2}} \alpha^I_m}$ .

~~~

Equation (13.37):

$\displaystyle{\bar L_m^\perp = \frac{1}{2} \sum_{p \in \mathbf{Z}} \bar \alpha_p^J \bar \alpha_{n-p}^J}$ , $\displaystyle{~~~L_m^\perp = \frac{1}{2} \sum_{p \in \mathbf{Z}} \alpha_p^J \alpha_{n-p}^J}$ .

$\displaystyle{ \begin{aligned} \left[ \bar L_m^\perp, x_0^I \right] &= \frac{1}{2} \sum_{p \in \mathbb{Z}} \left[ \bar \alpha^J_p \bar \alpha^J_{m-p}, x_0^I \right] \\ &= \frac{1}{2} \sum_{p \in \mathbb{Z}} \bar \alpha^I_p \left[ \bar \alpha^J_{m-p}, x_0^I \right] + \frac{1}{2} \sum_{p \in \mathbb{Z}} \left[ \bar \alpha^J_p, x_0^I \right] \bar \alpha^I_{m-p} \\ &= \frac{1}{2} \bar \alpha^J_m \left[ \bar \alpha^J_{0}, x_0^I \right] + \frac{1}{2} \left[ \bar \alpha^J_0, x_0^I \right] \bar \alpha^J_{m} \\ \end{aligned} }$

By Equation (13.33):

$\displaystyle{ \begin{aligned} \left[ \bar L_m^\perp, x_0^I \right] &= - \frac{1}{2} \bar \alpha^J_m \left[ i \sqrt{\frac{\alpha'}{2}} \eta^{IJ} \right] - \frac{1}{2} \left[ i \sqrt{\frac{\alpha'}{2}} \eta^{IJ} \right] \bar \alpha^J_{m} \\ &= - i \sqrt{\frac{\alpha'}{2}} \eta^{IJ} \bar \alpha^I_m \\ \end{aligned} }$

Since $I$ and $J$ are transverse coordinate indices, neither of them can be zero.

$\displaystyle{ \begin{aligned} \left[ \bar L_m^\perp, x_0^I \right] &= - i \sqrt{\frac{\alpha'}{2}} \bar \alpha^I_m \\ \end{aligned} }$

— Me@2019-12-25 10:56:15 AM

Two dimensional time 5.2.3

Posted on December 22, 2019 by rpflee

The first time direction is uncontrollable; the second is controlled by making choices, traveling through different realities. Future is a set of parallel universes.

— Me@2017-12-15 10:59:49 AM

The first time direction, which is along the timeline, is uncontrollable, because one can only travel from the past to the future, not the opposite.

The second direction, which is across different timelines, is controlled by making choices, forming different realities.

— Me@2019-12-21 11:03:23 PM

Two dimensional time 5.2.2

Posted on December 22, 2019 by rpflee

time direction ~ direction of change

multiple time directions ~ multiple directions of change

— Me@2019-12-22 04:38:47 PM

the first dimension of time ~ direction of change

the second dimension of time ~ direction of change of changes

— Me@2019-12-22 04:46:47 PM

Pandemonium, 2

Posted on December 21, 2019 by rpflee

Batman: You sold us out, Clark. You gave them the power that should have been ours. Just like your parents taught you. My parents taught me a different lesson… lying on this street… shaking in deep shock… dying for no reason at all. They showed me that the world only makes sense when you force it to.

— Batman

— The Dark Knight Returns

2019.12.21 Saturday ACHK

PhD, 3.8.2

Posted on December 19, 2019 by rpflee

財政自由 1.3.2

讀研究院的最大作用是，獲取獨家資料和人脈。

做到物理學家的其中一個，近乎先決條件是，認識一些一流的物理學家，從而可以跟他們對話。換句話說，讀研究院的主要目的是，爭取跟一些物理神人，對話的機會。
.

（問：但是，你又提議最好在，已經有財政自由時，才讀研究院？那樣，豈不是起碼要三、四十歲時，才可以讀研究院？

那時，頭腦都已經，大大不如十多二十歲了。）

無錯。那是兩難。

有如人生目標一樣，不會只有一個。當兩個目標有衝突時，要麼取一捨一、要麼雙方妥協。有時靈機一觸的話，則可以協同互生，合而為一。

（問：那即是怎樣？）

每個人不同，沒有一定的答案。但是，你可以參考學術界中，成功或失敗人士的經驗，從而避開一些宏觀的錯誤。之於其他細節，只能隨機應變，見步行步，行步見步。

例如，有些人年輕時專心賺錢，暫時放棄讀書；打算老一點時，才重操學業。但是，老一點時，已經沒有心思了。

沒有「心」的原因是，年紀越大，機會成本越高。亦即是話，研究學術的時間，往往可以用於更偉大的地方。沒有「思」的原因是，年紀越大，一般而言，身體和智力也不如年輕時。

（問：你即是話，財政充裕前，讀研究院時，即使智力再高，往往沒有自由去，研究自己喜歡的課題。但是，要等到財政自由時，才研究學術的話，又未必仍然有足夠的智力。）

無錯。那是兩難。

有如人生目標一樣，不會只有一個。當兩個目標有衝突時，要麼取一捨一、要麼雙方妥協。有時靈機一觸的話，則可以協同互生，合而為一。

（問：協同互生？如何執行？可否舉一個例？）

…

— Me@2019-10-22 09:44:23 PM

— Me@2019-12-17 09:35:51 PM

University

Posted on December 15, 2019 by rpflee

d_2019_09_29__17_29_36_PM_

In this picture, he was at his 15.

Later on, he studied at another university.

— Me@2019-12-15 03:27:25 PM

Varying the action, 2.2

Posted on December 15, 2019 by rpflee

…

$\displaystyle{ \begin{aligned} &= \int_{t_1}^{t_2} (D L \circ \Gamma[q]) \delta_\eta \Gamma[q] \\ \end{aligned}}$

…

$\displaystyle{ \begin{aligned} &= \int_{t_1}^{t_2} [\partial_0 L (t, q, v), \partial_1 L (t, q, v), \partial_2 L (t, q, v)] (0, \eta(t), D\eta(t)) \\ \end{aligned}}$

There are two kinds of tuples: up tuples and down tuples. We write tuples as ordered lists of their components; a tuple is delimited by parentheses if it is an up tuple and by square brackets if it is a down tuple.

— Structure and Interpretation of Classical Mechanics

So $\displaystyle{\left[\partial_0 L (t, q, v), \partial_1 L (t, q, v), \partial_2 L (t, q, v)\right] (0, \eta(t), D\eta(t))}$ is really a dot product:

$\displaystyle{ \begin{aligned} & \int_{t_1}^{t_2} (D L \circ \Gamma[q]) \delta_\eta \Gamma[q] \\ &= \int_{t_1}^{t_2} [\partial_0 L (t, q, v), \partial_1 L (t, q, v), \partial_2 L (t, q, v)] (0, \eta(t), D\eta(t)) \\ &= \int_{t_1}^{t_2} [\partial_1 L (t, q, v) \eta(t) + \partial_2 L (t, q, v) D\eta(t)] \\ \end{aligned}}$

— Me@2019-12-14 06:11:22 PM

Classical physics

Posted on December 14, 2019 by rpflee

Quantum Mechanics 6

As Gene and Sidney Coleman have pointed out, the term “interpretation of quantum mechanics” is a misnomer encouraging its users to generate logical fallacies. Why? It’s because we should always use a theory, or a more accurate, complete, and universal theory, to interpret its special cases, to interpret its approximations, to interpret the limits, and to interpret the phenomena it explains.

However, there’s no language “deeper than quantum mechanics” that could be used to interpret quantum mechanics. Unfortunately, what the “interpretation of quantum mechanics” ends up with is an attempt to find a hypothetical “deeper classical description” underneath the basic wheels and gears of quantum mechanics. But there’s demonstrably none. Instead, what makes sense is an “interpretation of classical physics” in terms of quantum mechanics. And that’s exactly what I am going to focus in this text.

Plan of this blog entry

After a very short summary of the rules of quantum mechanics, I present the widely taught “mathematical limit” based on the smallness of Planck’s constant. However, that doesn’t really fully explain why the world seems classical to us. I will discuss two somewhat different situations which however cover almost every example of a classical logic emerging from the quantum starting point:

Classical coherent fields (e.g. light waves) appearing as a state of many particles (photons)
Decoherence which makes us interpret absorbed particles as point-like objects and which makes generic superpositions of macroscopic objects unfit for well-defined questions about classical facts

— How classical fields, particles emerge from quantum theory

— Lubos Motl

There is no interpretation problem for quantum mechanics. Instead, if there is a problem, it should be the interpretation of classical mechanics problem.

— Lubos Motl

— paraphrased

— Me@2011.07.28

點石成金 8

Posted on December 12, 2019 by rpflee

The Metagame, 2

無謂的事務，如果不可避免，你可試試加一個有謂的情境。

For a boring but unavoidable task, add an amazing context.

For an interesting but useless activity, add a meaningful context.

For example, I use video games to train my courage.

— Me@2011.08.24

— Me@2019-12-12

Ken Chan 時光機 3.1

Posted on December 12, 2019 by rpflee

當年，他留下了傳呼機台的號碼。留言後，他會電話回覆，回答物理問題。

我在從事教學後才知道，用電話答物理概念問題，不會太花時間。但是，如果是答具體物理題目的話，其實十分費時，因為沒有紙筆的輔助。需要畫圖或者有繁複運算步驟時，大家也只能靠想像力。

同一題題目，假設當面解答，只需要 5 分鐘。但是，電話指點的話，就可以花上 15 分鐘至半小時不等。

但是，Ken Chan 仍然願意，以這個方式，為最多的學生，解答最多的問題，我對他十分感謝。

有一次，他在晚上十一時多回覆我的致電。他說先要關掉實驗機器。問了題目後，我順道問他讀書方法，訴苦說，來不及溫習應試。

他答了我很久，花了他大概半小時至一個小時，非常抱歉。

他講了一些東西。以下不依次序。

中五（會考年）每天溫習五、六小時，很正常的事。

你化學不好，為什麼不補化學？

我答：補得太多的話，我沒有足夠溫習。

他說：咁又係。（那又是。）

他問我附加數學有哪些課題。

如果讀了那幾個課題就不會有大問題。

…

— Me@2019-12-08 10:36:20 AM

Problem 13.5b

Posted on November 24, 2019 by rpflee

A First Course in String Theory

13.6 Unoriented closed strings

This problem is the closed string version of Problem 12.12. The closed string $\displaystyle{X^{\mu} (\tau, \sigma)}$ with $\displaystyle{\sigma \in [0, 2 \pi]}$ and fixed $\displaystyle{\tau}$ is a parameterized closed curve in spacetime. The orientation of a string is the direction of the increasing $\displaystyle{\sigma}$ on this curve.

…

Introduce an orientation reversing twist operator $\displaystyle{\Omega}$ such that

$\displaystyle{\Omega X^I(\tau, \sigma) \Omega^{-1}} = X^I (\tau, 2 \pi - \sigma)$

Moreover, declare that

$\displaystyle{\Omega x_0^- \Omega^{-1} = x_0^-}$

$\displaystyle{\Omega p^+ \Omega^{-1} = p^+}$

(b) Used the closed string oscillator expansion (13.24) to calculate

$\displaystyle{\Omega x_0^I \Omega^{-1}}$

$\displaystyle{\Omega \alpha_0^I \Omega^{-1}}$

$\displaystyle{\Omega \alpha_n^I \Omega^{-1}}$

$\displaystyle{\Omega \bar \alpha_n^I \Omega^{-1}}$

~~~

Equation (13.24):

$\displaystyle{X^{\mu} (\tau, \sigma) = x_0^\mu + \sqrt{2 \alpha'} \alpha_0^\mu \tau + i \sqrt{\frac{\alpha'}{2}} \sum_{n \ne 0} \frac{e^{-in\tau}}{n} (\alpha_n^\mu e^{i n \sigma} + \bar \alpha_n^\mu e^{-in \sigma})}$

$\displaystyle{\begin{aligned} X^{\mu} (\tau, \sigma) &= x_0^\mu + \sqrt{2 \alpha'} \alpha_0^\mu \tau + i \sqrt{\frac{\alpha'}{2}} \sum_{n \ne 0} \frac{e^{-in\tau}}{n} (\alpha_n^\mu e^{i n \sigma} + \bar \alpha_n^\mu e^{-in \sigma}) \\ X^I (\tau, 2 \pi - \sigma) &= x_0^I + \sqrt{2 \alpha'} \alpha_0^I \tau + i \sqrt{\frac{\alpha'}{2}} \sum_{n \ne 0} \frac{e^{-in\tau}}{n} \left( \alpha_n^I e^{- in\sigma} + \bar \alpha_n^I e^{i n \sigma)} \right) \\ \end{aligned}}$

$\displaystyle{\Omega X^I(\tau, \sigma) \Omega^{-1}} = X^I (\tau, 2 \pi - \sigma)$

By comparing $\displaystyle{\Omega X^I(\tau, \sigma) \Omega^{-1}}$ with $\displaystyle{X^I (\tau, 2 \pi - \sigma)}$ , we have:

$\displaystyle{\begin{aligned} \Omega x_0^I \Omega^{-1} &= x_0^I \\ \Omega \alpha_0^I \Omega^{-1} &= \alpha_0^I \\ \Omega \alpha_n^I \Omega^{-1} &= \bar \alpha_n^I \\ \Omega \bar \alpha_n^I \Omega^{-1} &= \alpha_n^I \\ \end{aligned}}$

— Me@2019-11-24 04:33:23 PM

回到過去 3.2

Posted on November 10, 2019 by rpflee

experience 2016 = reach 2017

— Me@2017-02-21 07:34:37 AM

having experienced the whole year of 2016

= having reached the beginning of the year 2017

— Me@2019-11-08 07:33:28 PM

Politics, 2

Posted on November 3, 2019 by rpflee

Try something impossible, 3 | Impossible self, 2

The challenge is to practice politics as the art of making what appears to be impossible, possible.

— Hillary Clinton

不是因為看見希望而堅持，而是因為堅持才看見希望。

—

2019.11.03 Sunday ACHK

PhD, 3.8.1

Posted on November 2, 2019 by rpflee

財政自由 1.3.1

The secret to creativity is knowing how to hide your sources.

— Not Einstein

In 1924, while working as a Reader (Professor without a chair) at the Physics Department of the University of Dhaka, Bose wrote a paper deriving Planck’s quantum radiation law without any reference to classical physics by using a novel way of counting states with identical particles. This paper was seminal in creating the very important field of quantum statistics. Though not accepted at once for publication, he sent the article directly to Albert Einstein in Germany. Einstein, recognising the importance of the paper, translated it into German himself and submitted it on Bose’s behalf to the prestigious Zeitschrift für Physik. As a result of this recognition, Bose was able to work for two years in European X-ray and crystallography laboratories, during which he worked with Louis de Broglie, Marie Curie, and Einstein.

— Wikipedia on Satyendra Nath Bose

（問：根據你的講法，好像大部分情況下，都不應該讀研究院似的。）

在理想的情況下，你可能應該讀研究院。

（問：那樣，你心目中的理想情況是什麼？）

假設你已經有財政自由，你就有可能，適合讀研究院；…

讀研究院的最大作用是，獲取獨家資料和人脈。

做到物理學家的其中一個，近乎先決條件是，認識一些一流的物理學家，從而可以跟他們對話。換句話說，讀研究院的主要目的是，爭取跟一些物理神人，對話的機會。

（問：那金錢和時間成本奇高。間中約他們暢談可以嗎？）

那比較困難。

如果你不是他們原本的朋友、同事或學生的話，大概不會有足夠時間，分配給你。

（問：自己一個做研究，一定不可以嗎？）

那十分困難。

即使是獨行俠愛因思坦，他的獨行俠形象，也是假的。大概而言，那只是他的大眾形象、公關技巧。

實情是，他在學術上，有一個開放謙卑的態度，十分願意吸收他人的思想，無論對方當時的名氣是怎麼樣。

例如，他有一段時期會，參加維也納學團的學術討論聚會。

又例如，有來自印度一所大學的，一位尚未世界知名的物理學家，企圖發表一篇文章，但給學術期刊拒絕了。於是，他把那篇文章，寄給了愛因思坦。

雖然素未謀面(?)，愛因思坦仍然用心閱讀，發現該文有料到，十分有意思。不單如此，他更親自把文章由英文翻譯成德文。在他的引薦下，德國一著名物理期刊出版了該文。

那位印度物理學家，就是後來舉世聞名的玻色。

愛因思坦一生幾大曠世鉅著之一，玻色-愛因斯坦統計規律，就是緣起於他和玻色的這次合作。

— Me@2019-10-29 10:20:33 PM

Bose adapted this lecture into a short article called Planck’s Law and the Hypothesis of Light Quanta and submitted it to the Philosophical Magazine. However, the referee’s report was negative, and the paper was rejected. Undaunted, he sent the manuscript to Albert Einstein requesting publication in the Zeitschrift für Physik. Einstein immediately agreed, personally translated the article from English into German (Bose had earlier translated Einstein’s article on the theory of General Relativity from German to English), and saw to it that it was published. Bose’s theory achieved respect when Einstein sent his own paper in support of Bose’s to Zeitschrift für Physik, asking that they be published together. The paper came out in 1924.

— Wikipedia on Bose–Einstein statistics

Physics Town

continues

Simcity, 2

scmutils, 2

Physics PageRank

Principal details

Ken Chan 時光機 3.2

1984

Quick Calculation 13.1

Two dimensional time 5.2.3

Two dimensional time 5.2.2

Pandemonium, 2

PhD, 3.8.2

University

Varying the action, 2.2

Classical physics

點石成金 8

Ken Chan 時光機 3.1

Problem 13.5b

回到過去 3.2

Politics, 2

PhD, 3.8.1