Daily Archives: May 16, 2011

Backdoor (computing)

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David A. Wheeler has proposed a counter to this attack using an approach he calls “diverse double-compiling”, which uses techniques adapted from compiler bootstrapping. This involves re-compiling the source of the compiler through another independently-written and generated “trusted” compiler, and then using the binary generated from this to recompile the original compiler again, and then comparing the binary generated from this second compilation with that generated from using the original compiler to recompile itself directly.

— Wikipedia on Backdoor (computing)

2011.05.16 Monday ACHK

小學生傳奇 1.1

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（安：那我修改我的講法。最近發現，有一部分位高權重的管理人員，智力已經退化到，連小學生都不如。）

那有什麼出奇呢？

（安：一點也不出奇。但是，我發覺那是對我來說，一個很大的應世問題。）

為什麼呢？

（安：如果我要應付那些人呢，我就要時常思考，究竟要用什麼表達方式，才可以令到他們接受我的意見。

但是，如果是面對理性的人，我根本毋須考慮什麼「表達方式」。真正重要的是，我的意見本身要正確。只要我列舉證據，理性的人就自然會認同。換言之，理性的人會被「事實」說服，而不是被「人」說服。所以，他們不會重視，道出那個事實的人，究竟用什麼表達方式。

但是，我發現一大部分人也不是那樣的。）

那樣，對你的應世，構成什麼實際的問題？

— Me@2011.05.12

2011.05.12 Thursday (c) All rights reserved by ACHK

A Fraction of Algebra

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As a mathematician there is a story I hear a lot. It tends to come up whenever I tell someone what I do for the first time, and they admit that they don’t really like, or aren’t very good at, mathematics. In almost every case, if I bother to ask (and these days I usually do), I find that the person, once upon a time, was good at and liked mathematics, but somewhere along the way they had a bad teacher, or struck a subject they couldn’t grasp at first, and fell a bit behind. From that point on their experiences of mathematics is a tale of woe: because mathematics piles layer upon layer, if you fall behind then you find yourself in a never ending game of catch-up, chasing a horizon that you never seem to reach; that can be very dispiriting and depressing.

— The Narrow Road, Zen and the Art of Mathematics

2011.05.12 Thursday ACHK

Spinors

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Twistors are closely related to spinors, objects that may be understood as “square roots of vectors”. I like to say that twistors may similarly be interpreted as “square roots of spacetime points”.

Witten enters the scene

In 2003, Edward Witten published his papers on the twistor treatment of the maximally supersymmetric Yang-Mills theory in four dimensions. For the first time, geometry in the twistor space was used to calculate scattering amplitudes – quantities knowing about some real dynamics and interactions in physics.

— Lubos Motl

2011.05.11 Wednesday ACHK