(反對)開夜車 2.3

Ken Chan 時光機 1.4.2.3

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本文章並(!)(!)可作為醫學建議。如需專業意見,請諮詢專業人士。

結果,他那天只睡了,一個半小時。

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我那時以為,那沒有什麼大不了。但是現在,我也已一把年紀了,才驚覺,只要有一點不幸,那就可以造成,嚴重的後果。

(問:那有什麼「嚴重的後果」?)

「嚴重後果」中,較為輕微的,我也經歷過,而且可以視為「不可逆轉」的。

例如,大前年開始,我左眼患有飛蚊症。即是話,視野中,有一些黑點等,不應存在的小垃圾。

飛蚊症可以視為「不可逆轉」的原因是,以現今科技,醫治飛蚊症方法,風險遠比「良性飛蚊」的症狀本身高。所以,除非一個人的飛蚊症極度嚴重,否則,眼科醫生也不會建議病人,去接受那些手術。

(問:「良性飛蚊」?)

「良性飛蚊」的「良性」,並不是說真的有益,而只是指「不會致盲,只會帶來精神困擾」。

至於「惡性飛蚊」,即是指「有致盲風險」,因為,那代表著,視網膜開始脫落;必須立刻做手術制止之。

(問:如果開始有飛蚊,自己又怎會知道是,「良性」還是「惡性」呢?)

不會知道。

所以:

  • 第一,你要在未有飛蚊時,防範於未然。

  • 第二,萬一仍然出現飛蚊的話,要立刻看眼科醫生,讓他為你檢查,是否視網膜開始脫落。

    • 如果不是,就不用擔心。

    • 如果是,可以立刻做手術,制止視網膜脫落,保住完整的視力。視網膜開始脫落,而不立刻做手術制止之,有致盲的風險。

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至於,我自己的案例,則幸好是良性的,不會致盲;只要飛蚊不惡化,視力不會減弱。

(問:但你剛才說,飛蚊症「會帶來精神困擾」?)

無錯。可以說是心靈創傷。

(問:為什麼呢?)

本文章並(!)(!)可作為醫學建議。如需專業意見,請諮詢專業人士。

— Me@2019-02-25 04:01:37 PM

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2019.02.26 Tuesday (c) All rights reserved by ACHK

知識論

(導師:李天命)

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d_2019_02_19__22_28_27_PM_

後設哲學

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Aside(題外話):

李天命先生推薦書籍:

《四大聖哲:蘇格拉底、佛陀、孔子、耶穌》

作者:雅士培 Karl Jaspers

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希伯來

宗教

耶穌

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希臘

理性

蘇格拉底

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邏輯/思考方法[大部分研究哲學人士,也不懂邏輯,不懂思考方法。]

庸顱戴光環

哲學無哲技

[科學有科技,哲學無哲技]

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知識論 —— 思

形上學 —— 死

倫理學 —— 生

— Me@2002-01-10

— Me@2019-02-20

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2019.02.20 Wednesday (c) All rights reserved by ACHK

Path-distinguishing function, 2

\displaystyle{\gamma(t)} = configuration path function

\displaystyle{\mathcal{F} [\gamma]} = a function of time that measures some local property of the path

……….It may depend upon the value of the function \displaystyle{\gamma} at that time

……….and the value of any derivatives of \displaystyle{\gamma} at that time.

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We can decompose \mathcal{F} [\gamma] into two parts:

1. a part that measures some property of a local description

and

2. a part that extracts a local description of the path from the path function.

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— 1.3 The Principle of Stationary Action

— Structure and Interpretation of Classical Mechanics

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1. The function that measures the local property of the system depends on the particular physical system;

2. the method of construction of a local description of a path from a path is the same for any system.

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\displaystyle{ \begin{aligned}  \mathcal{F} [\gamma] &= \mathcal{L} \circ \mathcal{T}[\gamma] \\  \mathcal{T} [\gamma] &= (t, \gamma (t), \mathcal{D} \gamma (t), ...)  \end{aligned}}

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— 1.3 The Principle of Stationary Action

— Structure and Interpretation of Classical Mechanics

— Me@2019-02-22 11:46:50 PM

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2019.02.24 Sunday ACHK

Quantum decoherence 9

d_2019_02_22__14_57_20_PM_

This is a file from the Wikimedia Commons.

In classical scattering of target body by environmental photons, the motion of the target body will not be changed by the scattered photons on the average. In quantum scattering, the interaction between the scattered photons and the superposed target body will cause them to be entangled, thereby delocalizing the phase coherence from the target body to the whole system, rendering the interference pattern unobservable.

The decohered elements of the system no longer exhibit quantum interference between each other, as in a double-slit experiment. Any elements that decohere from each other via environmental interactions are said to be quantum-entangled with the environment. The converse is not true: not all entangled states are decohered from each other.

— Wikipedia on Quantum decoherence

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2019.02.22 Friday ACHK

PhD, 3.3

故事連線 1.1.5.3 | 碩士 4.3 | On Keeping Your Soul, 2.2.3 | Release early. Release often, 3.3

這段改編自 2010 年 4 月 18 日的對話。

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所以,如果不是為了做學問、做研究,我大概不會去讀研究院。

(問:那是什麼意思?)

如果不是為了做研究,而是純粹為了穫得,碩士或博士學位的話,攻讀研究院是,十分浪費時間的。

換句話說,理想而言,不應為了穫得博士學位,去花(例如)六年時間,寫博士論文。反而,如果你的終極目標是做學問,你就應該直接,不斷做學問;能否穫得碩士/博士學位,並不應成為你考慮的,主要因素。

在你不斷做研究的途中,自然會有一刻,累積的研究成果/文章,無論在質素和份量上,都等價甚至優於,一般的博士論文。那時,你就有機會,透過遞交研究成果,向大學申請參與,博士論文答辯試(thesis defense);從而有機會,「直接」獲得一個博士學位。

換而言之,你的研究文章,如果是真材實學、上乘之作,它就是你的「博士論文」。

當年,哲學家維根斯坦(Ludwig Wittgenstein)和物理學家愛因斯坦,都是用這個方法,獲得博士學位的。

(問:他們大概毋須,任何博士學位吧?

根本,「愛因斯坦」這名字,遠遠重要過,「博士」這銜頭。)

無錯。所以,我以上是說「理想而言」。實際而言,在你不是研究生的情況下,要「不斷做研究」,近乎沒有可能;除非,你是金庸小說中的主要角色。

(問:什麼意思?)

他們彷彿都是,既不用上班,亦毋須維生。

那樣,他們才可以全天候地,鑽研武功。

— Me@2019-02-21 03:06:38 PM

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2019.02.21 Thursday (c) All rights reserved by ACHK

Path-distinguishing function

So we will try to arrange that the path-distinguishing function, constructed as an integral of a local property along the path, assumes a stationary value for any realizable path. Such a path-distinguishing function is traditionally called an action for the system. We use the word “action” to be consistent with common usage. Perhaps it would be clearer to continue to call it “path-distinguishing function,” but then it would be more difficult for others to know what we were talking about.

— 1.3 The Principle of Stationary Action

— Structure and Interpretation of Classical Mechanics

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2019.02.17 Sunday ACHK

Logical arrow of time, 7

When we imagine that we know and keep track of all the exact information about the physical system – which, in practice, we can only do for small microscopic physical systems – the microscopic laws are time-reversal-symmetric (or at least CPT-symmetric) and we don’t see any arrow. There is a one-to-one unitary map between the states at times “t1” and “t2” and it doesn’t matter which of them is the past and which of them is the future.

A problem is that with this microscopic description where everything is exact, no thermodynamic concepts such as the entropy “emerge” at all. You might say that the entropy is zero if the pure state is exactly known all the time – at any rate, a definition of the entropy that would make it identically zero would be completely useless, too. By “entropy”, I never mean a quantity that is allowed to be zero for macroscopic systems at room temperature.

But whenever we deal with incomplete information, this one-to-one map inevitably disappears and the simple rules break down. Macroscopic laws of physics are irreversible. If friction brings your car to a halt and you wait for days, you won’t be able to say when the car stopped. The information disappears: it dissipates.

— The arrow of time: understood for 100 years

— Lubos Motl

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If there is a god-view, there is no time arrow.

Time arrow only exists from a macroscopic point of view. Microscopically, there is no time arrow.

If there is a god-view that can observe all the pieces of the exact information, including the microscopic ones, there is no time arrow.

Also, if there is a god-view, there will be paradoxes, such as the black hole information paradox.

Black hole complementarity is a conjectured solution to the black hole information paradox, proposed by Leonard Susskind, Larus Thorlacius, and Gerard ‘t Hooft.

Leonard Susskind proposed a radical resolution to this problem by claiming that the information is both reflected at the event horizon and passes through the event horizon and cannot escape, with the catch being no observer can confirm both stories simultaneously.

— Wikipedia on Black hole complementarity

The spirit of black hole complementarity is that there is no god-view. Instead, physics is always about what an observer can observe.

— Me@2018-06-21 01:09:05 PM

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2019.02.11 Monday (c) All rights reserved by ACHK

Pandemonium

E: Can you just, you know, like, just tell me the answer?

J: Sorry?

E: You know, the answer. To everything.

What’s the point of love if it’s just disappear?

There has to be meaning to existence, otherwise the universe is made of pain and I don’t like the thought of that.

So, tell me the answer!

J: The more human I become, the less things make sense.

But that’s part of the fun. Right?

E: What do you mean?

J: If there were an answer I can give you to, how the universe works, it wouldn’t be special. It would be just a machinery fulfilling its cosmic design. It would be just a big, dumb food processor.

But, since nothing seems to make sense, when you find something or someone that does, it’s euphoria.

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In all of this randomness, in this pandemonium, you and Chidi found each other and you had a life together.

Isn’t that remarkable?

E: Pandemonium is from Paradise Lost. Milton called the center of hell “pandemonium”, meaning “place of all demons”.

I guess all I can do is to embrace the Pandemonium.

Find happiness in the unique insanity of being here, now.

— The Good Place

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2019.01.27 Sunday ACHK

(反對)開夜車 2.2

Ken Chan 時光機 1.4.2.2

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The light that burns twice as bright burns half as long, …

— Blade Runner (1982)

可能,因為他「溫習到凌晨」式的方法,對他來說有效,他亦鼓勵學生那樣做。

我現在的記憶,暫時未能確定,他在課堂中,有沒有明示推介過,用這個方法。但是,我記得在他派發的筆記中,其中一頁,有一個正在深夜讀書的漫畫。而在漫畫下面,有一句「study to 3 a.m.」(讀書至深夜三點鐘)。

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長話短說,我是反對這個方法的,理由有很多,例如:

第一,長期睡眠不足,會導致腦袋呆了,大大減低下一天的工作效率。

第二,長期睡眠不足,會導致身體時常病。

在 Ken Chan 的部分課堂,特別是假期的補課中,我就見到他時常咳嗽。可能,他在工作時代,仍然過著,極度忙碌的生活。

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還記得在九月,在課程的第一課,他就已經遲到,遲了大概 15 至 30 分鐘之間。那課原定於早上八時半開始。上課中途,他有點咳嗽。他說,因為當天早上之前,吸入了太多的氮氣。他懷疑一位同事,作弄了他。

話說,他工作的地方,有一部儀器壞了。他的同事跟他說:「部機好似壞咗,漏緊啲 nitrogen 喎,你聞下係唔係?」(那儀器疑似壞了,正在洩漏氮氣。你聞一聞,看看是不是。)

Ken Chan 事後回心一想,才醒起:「Nitrogen 又點會有味咖?」(氮氣又何來會有味道呢?)

結果,他那天只睡了,一個半小時。

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我那時以為,那沒有什麼大不了。但是現在,我也已一把年紀了,才驚覺,只要有一點不幸,那就可以造成,嚴重的後果。

— Me@2019-02-03 07:02:42 AM

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2019.02.03 Sunday (c) All rights reserved by ACHK

SICM

d_2019_02_02__12_27_49_PM_

Structure and Interpretation of Classical Mechanics (SICM) is a classical mechanics textbook written by Gerald Jay Sussman and Jack Wisdom with Meinhard E. Mayer. The first edition was published by MIT Press in 2001, and [the] second edition was released in 2015. The book is used at the Massachusetts Institute of Technology to teach a class in advanced classical mechanics, starting with Lagrange’s equations and proceeding through canonical perturbation theory.

— Wikipedia on Structure and Interpretation of Classical Mechanics

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2019.02.02 Saturday ACHK

DO

While DOLIST and DOTIMES are convenient and easy to use, they aren’t flexible enough to use for all loops. For instance, what if you want to step multiple variables in parallel?

(do (variable-definition*)
    (end-test-form result-form*)
  statement*)

— Practical Common Lisp

— Peter Seibel

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(defun split-if (fn lst)
  (let ((acc nil))
    (do ((src lst (cdr src)))
        ((or (null src) (funcall fn (car src)))
         (values (nreverse acc) src))
      (push (car src) acc))))


>(split-if #'(lambda (x) (> x 4)) '(1 2 3 4 5 6 7 8 9 10))

(1 2 3 4)
(5 6 7 8 9 10)

— p.50

— On Lisp

— Paul Graham

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Exercise 4.5

Implement the function split-if without using the macro do.

— Me@2019-01-30 09:58:30 PM

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2019.01.30 Wednesday ACHK

Problem 14.5d3

Counting states in heterotic SO(32) string theory | A First Course in String Theory

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d) Write a generating function \displaystyle{f_L(x) = \sum_{r} a(r) x^r} for the full set of GSO-truncated states in the left-moving sector (include both NS’+ and R’+ states).

Use the convention where \displaystyle{a(r)} counts the number of states with \displaystyle{\alpha' M_L^2 = r}.

Use \displaystyle{f_L(x)} and an algebraic manipulator to find the total number of states in heterotic string theory at \displaystyle{\alpha' M_L^2 = 8}.

~~~

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— This answer is my guess. —

~~~

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\displaystyle{ \begin{aligned} \alpha' M_L^2: \end{aligned}}

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\displaystyle{ \begin{aligned}   &f_{L, NS'+}(x) \\   &= a_{NS'+} (r) x^r \\  &= \frac{1}{2x} \left[ \prod_{r=1}^\infty \frac{(1 + x^{r-\frac{1}{2}})^{32}}{(1 - x^r)^8} + \prod_{r=1}^\infty \frac{(1 - x^{r-\frac{1}{2}})^{32}}{(1 - x^r)^8} \right] \\   & \\  &= \frac{1}{x} + 504 + 40996 x + 1384320 x^{2} + ... \\   \end{aligned}}

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\displaystyle{\begin{aligned}  &f_{L, R'+}(x) \\ &= a_{R'+} (r) x^r \\ &= 2^{15} x \prod_{r=1}^\infty \frac{(1 + x^{r})^{32}}{(1 - x^r)^8} \\ & \\ &= 32768 \, x+1310720 \, x^{2}+27131904 \, x^{3}+387973120 \, x^{4}+4312727552 \, x^{5} + ...   \end{aligned}}

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\displaystyle{ \begin{aligned} \alpha' M_R^2: \end{aligned}}

\displaystyle{ \begin{aligned} f_{NS+}(x)  &= 8 + 128 \, x + 1152 \, x^{2} + 7680 \, x^{3} + 42112 \, x^{4} + ... \\ \end{aligned}}

\displaystyle{ \begin{aligned} f_{R-}(x)  &= 8 + 128 x + 1152 x^{2} + 7680 x^{3} + 42112 x^{4} + ... \\ \end{aligned}}

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So the total number of states in heterotic string theory at \displaystyle{ \begin{aligned} \alpha' M^2 = 8 \end{aligned}} is

\displaystyle{ \begin{aligned}   &\left(1384320 + 1310720 \right) \times \left(1152 + 1152\right) \\  \end{aligned}}.

\displaystyle{ \begin{aligned}   &= 6209372160 \\ \end{aligned}}.

~~~

— This answer is my guess. —

— Me@2019-01-26 04:49:37 PM

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2019.01.27 Sunday (c) All rights reserved by ACHK

Quantum logic, 3

The more common view regarding quantum logic, however, is that it provides a formalism for relating observables, system preparation filters and states.^\text{[citation needed]} In this view, the quantum logic approach resembles more closely the C*-algebraic approach to quantum mechanics. The similarities of the quantum logic formalism to a system of deductive logic may then be regarded more as a curiosity than as a fact of fundamental philosophical importance. A more modern approach to the structure of quantum logic is to assume that it is a diagram – in the sense of category theory – of classical logics (see David Edwards).

— Wikipedia on Quantum logic

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2019.01.26 Saturday ACHK

PhD, 3.2

故事連線 1.1.5.2 | 碩士 4.2 | On Keeping Your Soul, 2.2.2 | Release early. Release often, 3.2

這段改編自 2010 年 4 月 18 日的對話。

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同理,合理一點的博士論文編寫模式,同樣是「release early, release often」(極速(而)頻繁(地)出版)。如果我攻讀博士課程,從課程之開頭,我就應該(例如)每一出版一篇網誌短文。日日如是,累績三年。然後,選當中最好之十篇文章合體,再打磨成學術文章出版。

(問:那樣,會不會在你成功,出版學術文章之前,就已經被同行之中的害群之馬,盜取了你的原創概念,從而捷足先登,出版了文章?)

絕對有可能。所以,你未必要跟足這個例子。重點是,你根據其精神,來設計你的策略。

(問:你的「其精神」,是指「release early, release often」?)

無錯。以下把它簡稱為「頻繁出版」。有了這個精神,你自然可以適當地修改這個例子,避免被壞人抄襲。例如,你每天學術短文,不必發表於公開網誌上。你可以改為,只發表在半公開的網誌上,導致只有知己朋友可以看到。

而最重點是,有了這個「『極速頻繁出版』遠比『延緩完美出版』優勝」的心態後,你會知道,在博士課程中途,甚至是之初,在專業學術期刊發表,每篇幾頁的文章,遠比在博士課程後期,在大學研究院之內發表,每本三百頁的論文,來得重要。

試想想,如果已經出版過,幾篇學術文章,把它們合體成博士論文,又有何難度呢?

其實,你博士論文中,最重要的想法,就已經在那幾篇文章之中。你需要做的,就只是串聯、擴展和打磨罷了。

(問:你的意思是,要透過每天出版一篇短文,累積成每數個月一篇,可出版的學術期刊文章;然後,再透過那數篇學術期刊文章,累積成你那本博士論文?)

— Me@2019-01-22 06:46:23 PM

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2019.01.22 Tuesday (c) All rights reserved by ACHK

duplicate

If (member o l) finds o in the list l, it also returns the cdr of l beginning with o. This return value can be used, for example, to test for duplication. If o is duplicated in l, then it will also be found in the cdr of the list returned by member. This idiom is embodied in the next utility, duplicate:

>(duplicate ’a ’(a b c a d))
(A D)

(defun duplicate (obj lst &key (test #’eql))
    (member obj (cdr (member obj lst :test test))
            :test test))

— p.51

— On Lisp

— Paul Graham

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Exercise 4.4

Without using the existing function member, define duplicate as in

>(duplicate ’a ’(a b c a d))
(A D)

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— This answer is my guess. —


(defun my-member (obj lst)
    (cond ((not lst) NIL)
          ((eq obj (car lst)) lst)
          (t (my-member obj (cdr lst)))))

— This answer is my guess. —

— Me@2019-01-21 06:34:46 AM

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2019.01.21 Monday (c) All rights reserved by ACHK