q*d
发帖数: 22178 | 1 最近王所长正在上书国家要1000亿建大加速器，
据说被无数人骂的屁滚尿流的，眼看是要黄了，
洋大人不失时机的出来打气鼓励啊。
into
High
University
University
Cosmic
researchers
cosmology.
of |
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p*****k
发帖数: 318 | 2 fanta, i think native is correct.
this seems to be a good example to teach hubble expansion
in an introductory cosmology class :P |
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s**e
发帖数: 103 | 3 There is a book by A.Linde 'inflational cosmology' or something like that.
Maybe it is too technical, but if you jut read the parts about the general
idea...
A.Guth et.al. wrote a pretty good popular article in Scientific American,
but I forgot what issue it is. :o( |
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y****o
发帖数: 2 | 4 A.Linde 'inflational cosmology'(90) 和M.Turner,
E.Kolb 'the early universe'(90)都是很不错的专业书,
在scientific american上,A.Guth,A.Linde,以及Steinhardt,
N.Turok等许多作出重要工作的人都写过文章,对了解早
宇宙的重要进展很有帮助 |
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P*****s
发帖数: 375 | 5 Flat and happy. Cosmologists can hardly believe how their luck has changed.
New observations often send theorists scurrying back to their equations, but
this year, measurements of one of the cosmos's most basic numbers gave the
answer theorists had hoped for: The universe appears to contain just the
amount of matter and energy that the most elegant picture of its origins
requires.
This theory, called inflation, holds that a burst of expansion in the first
instant of time stretched space almost p |
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c**********g
发帖数: 222 | 6
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
The point is that in fact pressure is a tensor, so the sign has no much definite
meaning. Also, in relativity, it can be covariant or contravovariant (the sign
is opposite). SO, we need to pay attention to the meaning of the sign.
In the case of the cosmological constant, the negative pressure will produce
a repulsive gravity! This is the reason that it will accelarate the expansion of
the universe.
I still do |
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l**n
发帖数: 67 | 7 I agree i was wrong here. But i still don't quite understand that
why this cosmological constant with negative pressure is needed
to ensure a static universe. If the total angular momentum(fishy?)
of the universe is not zero, is it possible to get a static universe
without \Lambda? The earth doesn't necessarily fall into the sun
as long as it has angular momentum, right? |
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f*******d
发帖数: 339 | 8 I often heard about anti-deSitter Universe. I know what is a de Sitter Universe,
which is explained in many cosmology books. Basically, it is a vacuum energy
dominated Universe. However, I don't know what is an Anti-de Sitter Universe.
It must be the opposite of the de Sitter space, but in what sense? A Universe
dominated by negative vacuum energy? Could any string theorist explain it to
me? |
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i*******n
发帖数: 166 | 9
why \sqrt R(t)? I think it is R(t).
BTW, in last chapter, you said that there are two kinds of redshift:
gravitational and cosmological. I think you should add another: Doppler
redshift. |
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c**********g
发帖数: 222 | 10
fun.
>>>>Here, I mean that the photon field itself is in thermal
equilibrium. Because
the photon is decoupled from the matter after recombation, it expandes
adaibatically. Its evolution is the same as that of the closed box of
photon
in adaibatic expansion. For this reason I say that it is in thermal
equibrium
with itself though no interaction at all.
a
is
the
not
talking
Yes, you are absolutly right. Because gravity play a cruical role
in cosmology,
I cite the cosmic energy theorem just i |
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f*******d
发帖数: 339 | 11
My feeling is that you spend more time on trying to understand
relativity theory than cosmology. |
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d****y
发帖数: 53 | 12 I guess you should be able find an explanation from
any book on cosmological physics, e.g. Peacock.
Roughly speaking, the distribution function in phase space
is proportional to g_s\eta, where g_s the the spin degeneracy
(number of polarizations), while the difference in the numerical
constant
(1 for boson, 7/8 for fermion) just comes from the fact that \eta is
different for bosons and fermions. |
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f*******d
发帖数: 339 | 13 There is no such thing as "safe". Every assumption must be tested. In the standard cosmological model,
the fundamental physical constants are assumed to be constant. However, there are various
models where these constants vary in some way,
and would produce observational effects. The first such
varying constant model was proposed by Dirac in 1930s (or 40s, I don't remember), but that model was ruled out. However, there are many other models floating around, and each year there
are maybe a few do |
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r******p
发帖数: 15 | 14 支持一把. 比较专业:)
热寂说的不成立就是因为辐射和物质在膨胀中T(t)函数不一样从而永远无法达到平衡态.
至于用熵(或热力学)来讨论宇宙演化的性质, 可以参见任何一本cosmology的教科书.
一般都有熵的表达式. 除此之外,
大爆炸模型也是用可逆绝热过程中熵不变来解释在0.51Mev
(正负电子湮灭)附近光子的reheating, 从而通过现在的微波背景辐射温度(~2.73K)来预
测中微子背景辐射温度的(~1.9K).这些在当代宇宙学里都是被广泛接受的.
学，也不需要涉及它。
使用，并不是很神秘
平衡态。 这种原始
达到平衡态，比如
数的条件下，
视界，
星球都耗尽了所有
衰变成
，在碰撞时放点光，
然，也许有我们
人对此既不偏爱
况，并不需要
end
not
idea,
what
right,
about
before
。
个更
哪里
演化 |
|
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T*********r
发帖数: 11175 | 16 不知道
我猜刘克峰一听他的什么东西可以跟COSMOLOGY MODEL扯上点关系
一定挺得意的
结果就中招了
呵呵
这事完全属于WAY BEYOND WEIRD |
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d****g
发帖数: 100 | 17 I think it is only because so-called "COSMOLOGY MODEL" and "string theory"
are only something like "new clothes of a king." These theories can not be
proved whether they are correct or wrong. So anybody can propose any theory.
Now a group of people is studying "string theory," which says this universe
has 11 dimensions. They will never prove it as they cannot, but on the other hand,
we cannot prove they are wrong either, as those are imaginations. This is the same
as a group of Christian study t |
|
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a****y
发帖数: 1035 | 19 【 以下文字转载自 Physics 讨论区 】
发信人: happytiger (快乐龙龙), 信区: Physics
标 题: 超新星与暗能量的发现－－今年诺贝尔物理奖工作的介绍[zz]
发信站: BBS 未名空间站 (Wed Oct 5 12:12:03 2011, 美东)
这个科普太好看了。
http://bbs.sciencenet.cn/home.php?mod=space&uid=3061&do=blog&id
今年的诺贝尔物理奖授予了三位在发现宇宙加速膨胀的研究中做出杰出贡献的学者：Pe
rlmutter, Schmidt和Riess. 应该说，由于这项工作无可争辩的巨大重要性，几年来他
们一直是获奖的热门人选。但是，导致宇宙加速膨胀的暗能量是什么仍是一个未解决的
问题，而相关的许多理论和观测还处在研究的前沿，存在许多疑问和争论，诺贝尔奖评
委会素有稳重、保守的传统，所以我原以为他们还要再过若干年才会获奖。因此，作为
一名宇宙学研究者，我为他们今年获得这项殊荣感到非常高兴。
Perlmutter, Schmidt 和 Riess 是因为对超新星的研究而获奖的。超新星的... 阅读全帖 |
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s****1
发帖数: 425 | 20 要么全新，要么没有笔迹。有感兴趣的同学发信给我，可以提供详情。廉价
处理
1.Observational cosmology, stephen serjeant
2, Mathematical Methods for Physicists,物理学家用数学方法 Sixth Edition,
George B. Arfken (Author), Hans J. Weber (Author), Frank E. Harris (Author)
3,Atom Optics,原子光学 Pierre Meystre
4,Elements of quantum optics,量子光学基础 Pierre Meystre and Murray Sargent
5,Spectra of Diatomic molecules (Molecular spectra and molecular structure),
Gerhard herzberg
6,Quantum theory of atomic structure, JOHN C. Slater
7,Atomic collision theory, B... 阅读全帖 |
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f**d
发帖数: 768 | 21 http://theory.people.com.cn/GB/40538/3132387.html
10年前，中国一百多名顶尖级科学家，耗时4年，预测了21世纪的100道科学难题。
其中很多课题已经成为国家973，985的重点攻关课题。
这是中国科学家第一次向全世界发布自己对未来的看法。
其中19个难题涉及神经科学
49.脑神经系统动力学
Dynamics of the Nervous systems in Brain
50.生命、人的思维、意识、目的等的物理学基础
The Physical Bases of Life, Thinking, Consciousness and Intention
54.脑的计算模型能带我们走多远
How far can the Computational Model of Brain Bring Us?
56.未来的认知神经科学能否给意识以新的解释
If the Future Cognitive Neuroscience Give Us New Explanation of
Consciousness
59.脑的选择性自适应
The Selective... 阅读全帖 |
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l*******r
发帖数: 39279 | 22 ☆─────────────────────────────────────☆
qed (鸟瞰红尘) 于 (Tue Oct 6 00:13:58 2009, 美东) 提到:
–noun (used with a singular verb) 1. the branch of philosophy that treats
of first principles, includes ontology and cosmology, and is intimately
connected with epistemology.
2. philosophy, esp. in its more abstruse branches.
3. the underlying theoretical principles of a subject or field of inquiry.
4. (initial capital letter, italics) a treatise (4th century b.c.) by
Aristotle, dealing with first princi |
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w*******y
发帖数: 60932 | 23 I don't think the game discounts are live yet, but the soundtrack is up to
pay as you want, no minimum.
Soundtrack = Link:
http://jimguthrie.bandcamp.com/
Link:
http://www.swordandsworcery.com/news
SUMMER SOLSTICE VIDEOGAME & MUSIC SALE: Tuesday, June 21st 2011 [1 DAY ONLY]
The videogame + music project known as Sword & Sworcery launched 'around the
vernal equinox' on the first day of spring 2011 & so a summer solstice
videogame + music sale is both chronologically & cosmologically inevitable.
.... 阅读全帖 |
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w*******y
发帖数: 60932 | 24 Link:
http://www.khanacademy.org/
Free Step By Step Video's On Math, Science, Humanities & Other, Test Prep's
Learn almost anything for free.
With a library of over 2,600 videos covering everything from arithmetic to
physics, finance, and history and 207 practice exercises, we're on a mission
to help you learn what you want, when you want, at your own pace.
Learn Anything to Math, Science, Humanities & Other, Test Prep's
Math
Too Basic Math..
Arithmetic
Developmental Math
Developmental Math 1
De... 阅读全帖 |
|
v**********m
发帖数: 5516 | 25 Sir Karl Raimund Popper, CH FRS[1] FBA (28 July 1902 – 17 September 1994)
was an Austro-British[2] philosopher and a professor at the London School of
Economics.[3] He is regarded as one of the greatest philosophers of science
of the 20th century;[4][5] he also wrote extensively on social and
political philosophy.
Popper is known for his attempt to repudiate the classical observationalist
/ inductivist form of scientific method in favour of empirical falsification
. He is also known for his oppo... 阅读全帖 |
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s******o
发帖数: 298 | 26 By SPACE.com Staff
posted: 07:00 am ET
15 March 2002
A highly sensitive new survey instrument attached to a telescope in the
Southern Hemisphere has come online, showing that the device works and
producing several new pictures of distant galaxies.
The European Southern Observatory's Visible Multi-Object Spectrograph (VIMOS)
made its first observations, achieving what astronomers call "first light,"
on Feb. 26 and the images were released Wednesday.
Astronomers are billing the device as a "cosmol |
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s******o
发帖数: 298 | 27 Physicists Put Brakes on Accelerating Universe Theory
New calculations suggest that dim supernovae may not signal acceleration
after all.
by William Schomaker
Scientists from Los Alamos National Laboratory and Stanford University say
there’s more than one way to dim a supernova. If they’re right, hypothetical
particles called axions may be robbing light from intergalactic space to usher
the return of a decelerating universe model.
In 1998, two teams of astronomers turned cosmology upside-down wi |
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s*****t
发帖数: 1994 | 28 The Galaxy and the Quasar
Credit: R. Knacke (Penn State Erie) et al., Hubble Heritage Team, NASA
Explanation: Is the galaxy in the center connected to the quasar on the upper right?
Disagreements about systems like this have raged for decades and have been used to
challenge the foundations of modern cosmology. Some believe that the quasar Markarian
205 was recently ejected from galaxy NGC 4319, indicating that the high redshift of
Markarian 205 is not indicative of its distance. Most astro |
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s*****t
发帖数: 1994 | 29 WMAP Resolves the Universe
Credit: WMAP Science Team, NASA
Explanation: Analyses of a new high-resolution map of microwave light emitted only 380,000 years after the Big Bang appear to define our universe more precisely than ever before. The eagerly awaited results from the orbiting Wilkinson Microwave
Anisotropy Probe resolve several long-standing disagreements in cosmology rooted in less precise data. Specifically, present analyses of above WMAP all-sky image indicate that the universe is 13.7 |
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