文章与日志

在宇宙空间,碟子状结构是最常见的力学结构,大约1半的恒星都位于碟子状螺旋星系当中,而象太阳系这样有行星的碟子状恒星结构,也越来越有迹象表明是普遍存在的.另外碟子的构型也出现在很多其他地方,如白矮星和黑洞,因此碟子一定引力的常见力学结果.

用红外眼睛朝银河系中心望去:

CREDIT: IPAC/CALTECH/2MASS/NASA

如果有可能在远处俯视银河这个大盘子:

CREDIT: CHRIS BUTLER
宇宙可见结构的演化,最主要的研究方法是计算机模拟.

Cosmological Parameters from Eigenmode Analysis of Sloan Digital Sky Survey Galaxy Redshifts

原文

We present estimates of cosmological parameters from the application of the Karhunen-Loève transform to the analysis of the 3D power spectrum of density fluctuations using Sloan Digital Sky Survey galaxy redshifts. We use mh and fb = b/m to describe the shape of the power spectrum, 8gL" align="middle"> for the (linearly extrapolated) normalization, and to parametrize linear theory redshift space distortions. On scales k 0.16hMpc–1, our maximum likelihood values are mh = 0.264 ± 0.043, fb = 0.286 ± 0.065, 8gL" align="middle"> = 0.966 ± 0.048, and = 0.45 ± 0.12. When we take a prior on b from WMAP, we find mh = 0.207 ± 0.030, which is in excellent agreement with WMAP and 2dF. This indicates that we have reasonably measured the gross shape of the power spectrum but we have difficulty breaking the degeneracy between mh and fb because the baryon oscillations are not resolved in the current spectroscopic survey window function. ©2004 American Institute of Physics

Brane Inflation: From Superstring to Cosmic Strings

S.-H. Henry Tye
Laboratory for Elementary Particle Physics, Cornell University, Ithaca, NY 14853

Brane inflation, where branes move towards each other in the brane world, has been shown to be quite natural in superstring theory. Inflation ends when branes collide and heat the universe, initiating the hot big bang. Cosmic strings (but not domain walls or monopoles) are copiously produced during the brane collision. Using the COBE data on the temperature anisotropy in the cosmic microwave background, the cosmic string tension µ is estimated to be around 10 –6 > Gµ > 10–11, while the present observational bound is 7 × 10 –7 > Gµ. This implies that the anisotropy that seeds structure formation comes mostly from inflation, but with a small component (< 10%) from cosmic string effects. This cosmic string effect should be testable in the near future via gravitational lensing, the cosmic microwave background radiation, and/or gravitational wave detectors like LIGO II/VIRGO. ©2004 American Institute of Physics

1923年11月3日，Slater非常兴奋，以至于在给母亲的信中，都忍不住写道：
“人们不知道光是旧式的波呢，还是爱因斯坦先生的光粒子，或是Silberstein先生的光箭头，...我想到了一个确实有希望的念头，...，我既用了波又用了粒子，而粒子则是被波所携带的某种东西，从而粒子就会到达波把它们送到的那些地方，而非别人所设想的那样只是沿着直线射出。因此，例如如果波受到反射，则粒子也受到反射，于是就一切顺利了。”

图像，是人最粗朴的感知，视觉，本体感觉，乃至听觉，都应该参与了图像的构成。
人对于世界的理解，通向概念之形成的理解，正是始于这个图像。
从图像当中最早形成的概念，似乎是图形，而表达人获得对于图形的领悟，可以是身体的依照图形的运动，更明确的，是能够绘摹图形，例如直线段。
这大概就是几何的起源，构成那个纯真的经典世界图景的基础框架，空间概念由此开始成长。

西安半坡遗址(约7000年前)出土鱼纹陶盆

随着几何经验的逐渐丰富起来，纯真年代的另一个要素-因果律开始参与构造那个图像的世界：几何背后的原因。

本文写作日期已忘，大概是99年前后吧，因为似乎最早是在BBS上写的。存此。
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我们常常认为自省是一种道德姿态，其实，如果再往前走一 步，我们就从德之域抵达道之域。

自省的一个常见定义就是检点自己的喜怒哀乐，当一个人因充沛的激情而自我燃烧时，不知道他有多大的几率会意识到需要这种初等的自省：）

然而检点自己的喜怒哀乐常常是得不到有意义的结果的，于是稍加歇息，之后又转入下一轮的激情燃烧准备期…