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Void Filler

There is a game called Nihilumbra: You are born from the void, and the void keeps chasing you, trying to engulf you. To live, you travel, you learn all kinds of "colors" as tools to fight back. After a long journey, however, the void still catches you. You are in despair. Unexpectedly, however, the void expels you - all those colors that you collected during your journey have filled your void inside. You are no longer empty. You are no longer part of the void.

You are free at last.

But that's not the end. The world has been destroyed. That will prevail in your conscience unless you fix it. 

I like this game a lot. I had always been empty since childhood. “从童年起,我便独自一人照顾着,历代的星辰。” That emptiness reached its maximum during my undergraduate study. I wouldn't have felt sorry at all, had I died at some random accident. Well, yes, there were people who loved me, there were interesting things that were nice to experience, the world was in general good. But I had no passion for anything.

Not until I finally made my way to physics.

But that's not the end. I was and still am lacking way too much knowledge. I hope to use the rest of my life to fill this new, lovely, adorable void. 

I can never fail - at least I can fill a very small part of it.


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目录 一、工作 1. 无情的事实 2. 研究 3. 角色转换 二、生活 1. 作为母亲 2. 作为妻女 3. 作为朋友和自己 三、其他感想 1. 钱财 2. 海内与海外 3. 结尾必然要盲目乐观


上次搭档过生日,我写了三十条夸他的小列表,很多人评论说好甜。那算什么甜!还有更甜的。那三十条都是夸他本身的,并没写太多我俩之间的互动。我就写写。比起夸他,更像是秀恩爱。 领证那天我写过一次,但结了婚又有了小孩,我再重新写写,齁死你们。 1. 怀孕时帮我系鞋带穿袜子剪趾甲包揽所有事,洗好澡还会帮我涂身体乳防妊娠纹。 2. 我偷懒睡觉时,他从不叫醒我。从不。只是帮我把该我做的家务做了。 3. 小孩有时候手脚没轻没重弄疼我,我就委委屈屈窝进他怀里告状。他就会抱紧我然后训斥小孩。 4. 我们会趁小孩睡着,把他丢在家里(开着监控),偷跑出去看夜场电影。 5. 小孩嘴馋,会哭着叫“肉”、“葡萄”、“bagel”之类,搭档就慌忙去给他准备。往往把孩子弄好了,我又扁扁嘴跟着叫“cereal”,“葡萄”之类,搭档就也无奈地笑着给我准备。 6. 冬天我手脚冷,坐在一起时往往自然地把四肢往他身上搁,他会握住我的脚,还会找一些够得到的衣物把我盖好。 7. 他会给我编辫子。 8. 有次他喝咖啡,我觉得咖啡闻起来很香,就去亲他。果然唇齿留香。后来他又喝一口,反过来亲我。 9. 好吃的好喝的,最后几口,都会留给我。往往我们谦让半天,然后觉得好笑。 10. 不可描述时,非常尊重我的意愿。我们都乐于满足对方的需求和幻想。 11. 分别时,会吻我。 12. 我的耳洞是他给打的。 13. 常会在睡梦中翻身抱我。 14. 我想要买的东西,他从不拒绝,总是很痛快地同意。 15. 我们总有说走就走的旅行,往往一拍即合。 16. 他去超市买菜总会买回我喜欢吃的。 17. 他会保护我。即便站在我对面的,也是对他很重要的人。 18. 几乎从不批评指责我。(其实很多时候我需要他的批评。) 19. 我们会陪对方看自己不喜欢看的节目。 20. 他一抱我,我就困了。我总说他自带困场。反过来也一样。 21. 我叫他哥哥,他会叫我宝宝。孩子也跟他学,错认为我们家的宝宝是我,怎么也改不过来。 22. 他会给孩子讲各种科普知识,小孩对太阳系的认知已经超过了我。 23. 我给他剪头发剪得很丑,他也不怪我。 24. 只在我的要求下,给我写过一封情书。长消息也非常少发。可是每次都能把我看哭。 25. 领证那天,紧张得把钥匙和戒指缠在一起,抖着手半天才分开来;还把自己的名字念错。 26. 不是一个浪漫的人,可是会带我去他能想到的浪漫地方。

Basics: dimensional analysis

I decide to begin writing some back-of-the-envelope stuff in this blog; mostly very basic things. Consider Dirac fermion coupled to $U(1)$ field. $$\mathcal{L}=\bar{\psi}\gamma^\mu (\partial_\mu-iA_\mu) \psi - \frac{1}{e^2} F_{\mu\nu}F^{\mu\nu}. $$ In d spacetime dimensions, the first part in the kinetic term implies $[\partial]+2[\psi]=d$, leading to $[\psi]=(d-1)/2$. The second part leads to $2[\psi]+[A]=d$. Plugging in the value for $[\psi]$, we have $[A]=1$, then $[F]=2$. Using this and plug back in the Maxwell term $2[F]-[e^2]=d$, we arrive at $[e^2]=4-d$. When we are in 3+1d, the gauge coupling is thus dimensionless. For 2+1d, the gauge coupling has dimension $[e^2]=1$, so this theory is strongly coupled in the infrared. Also, the potential energy between two charges increases logarithmically with respect to the distance between them, which is a very mild form of confinement. References:  [1] David Tong, Lectures on gauge theory, chapter 8.