l**********1
发帖数: 5204 | 1 那是 Poincaré 龐加萊猜想的解铃人 俄罗斯数学家 Perelman 佩雷尔曼
//en.wikipedia.org/wiki/Grigori_Perelman
please go to
//en.wikipedia.org/wiki/Henri_Poincaré
//en.wikipedia.org/wiki/Poincaré_conjecture
and
名稱三體問題
英語名稱：three-body problem
N體問題及三體問題的概念N體問題：
N體問題可以用一句話寫出來：在三維空間中給定N個質點，如果在它們之間只有萬
有引力的作用，那麽在給定它們的初始位置和速度的條件下，它們會怎樣在空間中運動。
三體問題：
最簡單的例子就是太陽系中太陽，地球和月球的運動。在浩瀚的宇宙中，星球的大
小可以忽略不記，所以我們可以把它們看成質點。如果不計太陽系其他星球的影響，那
麽它們的運動就只是在引力的作用下産生的，所以我們就可以把它們的運動看成一個三
體問題。
天體力學中的基本力學模型。研究三個可視爲質點的天體在相互之間萬有引力作用
下的運動規律問題。這三個天體的質量、初始位置和... 阅读全帖 |
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l**********1
发帖数: 5204 | 2 LZ just prepare Move on to lower rank journal
from your MS met aggressive one reviewer at least one and s/he prefer
gave her/his even negative reply which can be delayed one working day that
is better.
pls refer below english forum they talked about this topic
>>
59. physicsprof - June 16, 2010 at 10:55 am
Where does this notion that "the work of Einstein may at one time have been
dismissed"? Please check your facts. It was 1905 when Einstein made his
groundbreaking discoveries. Two of the subj... 阅读全帖 |
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l**********1
发帖数: 5204 | 3 FAQ follow on lower floor?
--matrix guess
>>
63. tsb2010 - June 16, 2010 at 11:16 am
Good points from #59 - but the amount of "low-hanging fruit" has diminished
- it is asymptotically harder to advance the field to the same degree as
researchers 100 years ago. bla bla bl
Progres is bound to be incremental - until (maybe) a BIG IDEA comes along.
But since research doesn't happen in a vacuum, it is hard to predict which
ones of the little "insignificant" steps along the way helped out... |
|
m******g
发帖数: 467 | 4 Science 13.11.15 (包含Editor's Choice等推荐的其他杂志的文章，之后省略这句话)
推荐：
1. Dosage compensation via transposable element mediated rewiring of a
regulatory network
D. miranda在1 my前出现neo-X chromosome, TE-mediated rewiring of regulatory
network (domestication, amplification, and fine-tuning) followed by erosion
of nonfunctional parts of the transposon
idea挺有趣的.
2. Long-term dynamics of adaptation in asexual populations
Power law model fits/predicts the data better than Hyperbolic model with an
asymptote.
Fitne... 阅读全帖 |
|
m******g
发帖数: 467 | 5 Science 13.11.15 (包含Editor's Choice等推荐的其他杂志的文章，之后省略这句话)
推荐：
1. Dosage compensation via transposable element mediated rewiring of a
regulatory network
D. miranda在1 my前出现neo-X chromosome, TE-mediated rewiring of regulatory
network (domestication, amplification, and fine-tuning) followed by erosion
of nonfunctional parts of the transposon
idea挺有趣的.
2. Long-term dynamics of adaptation in asexual populations
Power law model fits/predicts the data better than Hyperbolic model with an
asymptote.
Fitne... 阅读全帖 |
|
A****t
发帖数: 141 | 6 统计并不是总用mean而不用median，针对有些数据(比如可能有outlier)median比mean
更robust，可以用median.但是如果感兴趣的是average,在统计学上sample mean有很好
的asymptotic properties.而很多时候median没有这些性质，比如求个standard error
可能就要用bootstrap,或者一些比较复杂的方法来推导。 |
|
c****n
发帖数: 21367 | 7 for simple systems, i agree with you.
however, for complex systems, you can only "guess" the low dimension
asymptotical model. because if the system is "complex" to us human being
micro-level knowledge cannot infer the macro-level behavior, and vice versa
the mechanistic answer is meaningful, the phenomenological one is
meaningful too. and for complex systems, these two cannot subsititute
each other unless the system become resolvable (not complex anymore). |
|
|
|
g*****r
发帖数: 4 | 10 Just finished my econometric comp. FIML is asymptotically
equivalent to 3SLS without constraint on the variance matrix.
We know that if there exists heteroskedasticity or in the case
of simultaneous equation model, 3SLS is preferred, and thus FIML. |
|
j**********y
发帖数: 1360 | 11 ☆─────────────────────────────────────☆
colormetal (colormetal) 于 (Fri Apr 13 16:01:44 2007) 提到:
我有一组panel data
求证一个有关社会网络参数和区域专利数量的关系
有15年的纵向数据，15个横向data objects，independent variable 有13个，其中包
括8个control variable
想问一下，需要多大sample size, 我现在的SIZE(225)是不是够了
谢谢
☆─────────────────────────────────────☆
wlywly (hi) 于 (Fri Apr 13 17:00:12 2007) 提到:
Not enough. The asymptotic theory does not apply here.
☆─────────────────────────────────────☆
colormetal (colormetal) 于 (Fri Apr 13 17:15:38 20 |
|
m******y
发帖数: 266 | 12 是啊，我也是第一次才看到这种方法。这个理论应该有很大的局限性，要不这个理论会
很流行的。比local asymptotic analysis而言，其实要容易处理一些（多）。
Large deviation的确是他主要卖点,这么做的确很有风险. |
|
m******y
发帖数: 266 | 13 有几个基本假设是理论计量界很不喜欢的。现在计量理论基本都是基于asymptotics理论
了，所以我想，理论计量出身
的老师，是不大会推荐给学生的。
不过商学院貌似不关心，可能他们注意力基本上是在应用，而不是计量本身吧。本科生
用这本书的好处是，有了那几
个基本假设，一些结论就很好讲了。 |
|
i*******e
发帖数: 349 | 14 my $0.02。
BLUE里面的U=unbiased，unbiasedness是个finite sample的概念，consistency是个
asymptotic的概念，两者没有必然关系。
计量教材里面有很多estimator在finite sample里面是biased但是consistent。另外一
方面，有的estimator是unbiased但是不consistent，例如我用样本里面的第一个观测
值X1作为sample mean的estimator，是unbiased，但通常不是consistent的，因为在样
本趋向无穷大时，lim( |X1-mean(x)|>epsilon )=常数，该常数一般不为0。
另外，WLS是不是BLUE或者consistent当然要看DGP的假设。 |
|
f*******r
发帖数: 257 | 15 The reason that probit or logit reports z stat is that they are maximum
likelihood estimators, the asymptotic distribution of it is normal. "reg y
x" is an ols model. When the assumptions of OLS hold, the distribution of
the stat (b/se(b)) conforms to t distribution. However, if the assumptions
do not hold, then that statistic does not conform to t distribution anymore.
Despite that, stats packages still report them as t stat. The conclusion
is: you are safe to use z-stat for probit or t-s |
|
p********d
发帖数: 1007 | 16 you should distinguish between small sample properties and asymptotic
properties.
y
assumptions
anymore.
conclusion
the |
|
k***g
发帖数: 7244 | 17 国债越多越好不应该是个动态均衡，虽然美国可以印美钞，国债没有 credit risk，但
是有 interest rate risk，多发国债会影响到长期利率，考虑到 cost of borrowing
，举债不会是越多越好；
宏观模型里一般会有一个假定的外生借贷上限，或者内生的假设政府每个 period 的财
政收入在不举新债的前提下必须足够用以支付旧债的利息；或者内生的假定国家资产的
present value 必须是 asymptotically nonnegative；
另外你肯定也必须要考虑到 real business cycle，记得有一篇 NBER 的 working pa
per的结果是政府在 recession 的时候举债，在 boom 的时候不举债，也就是说债务的
均衡同时也由 economic shock 这个 （stochastic） state variable 决定；如果你
不引入状态变量，你无法解释美国的 debt cycle，i.e. 从几乎没有国债到到负债累累
的变化，因为如果几乎没有国债是一个均衡，那它应该是相对稳定的，单纯内生的选择
不应该打破这 |
|
G****n
发帖数: 145 | 18 I am sure about that. Notice that Li Wei is listed as Professor but
Wang Neng and Tian Guoqiang are listed as Visiting Professors. http://www.ckgsb.com/faculty/LIWei/index.aspx
教授简介
李伟博士现为长江商学院经济学教授、长江案例中心主任、长江企业社会责任研究中心
主任，世界银行顾问，在加入长江商学院之前，曾任教于杜克大学商学院。
主要研究领域
李伟教授的研究包括转型经济学，中国经济，政治经济学，新兴市场金融学，公共金融
学，应用经济等。
学术成就
李伟教授的研究成果多见于如《美国经济学期刊》、《政治经济学期刊》、《经济学研
究期刊》等国际一流学术杂志。因其出色的教学和研究工作，李伟博士曾多次获奖，如
1992年获梅隆博士学奖学金；1991年获Rackham奖学金等。
主要学术成果
1. "Can Stock Price Movements Inform Operational Improvement E... 阅读全帖 |
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t*******i
发帖数: 255 | 19 check Li Wei's biography at CKGSB
http://www.ckgsb.edu.cn/personalsites/Index.aspx?navid=8968e565
it clearly says that "Apart from his role at Cheung Kong Graduate School of
Business, Dr. Li Wei is a professor of Business Administration at Darden
Graduate School of Business, University of Virginia,"
Obviously he's still got a position at UVa
i don't know much about other guys, but for Li Wei, I believe he hasn't
resigned totally from his US university.
I am sure about that. Notice that Li Wei i... 阅读全帖 |
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G****n
发帖数: 145 | 20 李伟 LI Wei 密歇根大学经济学博士
长江商学院经济学教授
E-mail: w*[email protected]
个人主页
教授简介
李伟博士现为长江商学院经济学教授、长江案例中心主任、长江企业社会责任研究中心
主任，世界银行顾问，在加入长江商学院之前，曾任教于杜克大学商学院和达顿商学院
。
主要研究领域
李伟教授的研究包括转型经济学，中国经济，政治经济学，新兴市场金融学，公共金融
学，应用经济等。
学术成就
李伟教授的研究成果多见于如《美国经济学期刊》、《政治经济学期刊》、《经济学研
究期刊》等国际一流学术杂志。因其出色的教学和研究工作，李伟博士曾多次获奖，如
1992年获梅隆博士学奖学金；1991年获Rackham奖学金等。
主要学术成果
1. "Can Stock Price Movements Inform Operational Improvement Efforts?
Evidence from the U.S. Airline Industry", with Marc Lipson, Kamalini Ramdas,
and Jonathan Willia... 阅读全帖 |
|
w****r
发帖数: 748 | 21 他们三人获奖的理由是"for their empirical analysis of asset prices".楼上的说
法有意思，不过编的成分太重了，有些偏离，要是能更贴一点就好了。
Hansen对于GMM的贡献可不是把它拿到经济学里面推广。可以说，他是最早做出来GMM这
个想法的（即便可能有其它人曾经提出来类似的idea）。 他证明了GMM Estimator的
consistency,asymptotic normality,并讨论相关检验问题。
Fama大家熟悉的是有效市场假说，不过其实他还有因子模型。这是一篇被引用了过万次
的文章。 |
|
w****r
发帖数: 748 | 22 他们三人获奖的理由是"for their empirical analysis of asset prices".楼上的说
法有意思，不过编的成分太重了，有些偏离，要是能更贴一点就好了。
Hansen对于GMM的贡献可不是把它拿到经济学里面推广。可以说，他是最早做出来GMM这
个想法的（即便可能有其它人曾经提出来类似的idea）。 他证明了GMM Estimator的
consistency,asymptotic normality,并讨论相关检验问题。
Fama大家熟悉的是有效市场假说，不过其实他还有因子模型。这是一篇被引用了过万次
的文章。 |
|
h******h
发帖数: 4 | 23 图形界面的用Origin做图表，xfig画示意图。Orgin很好用，但不是免费的。
现在都转向用metapost和asymptote的脚本画。 |
|
h******h
发帖数: 4 | 24 If GnuPlot could produce professional looking graph, I will give it another
try...
The strengths of origin is GUI interface for data analysis. In initial stage
of a research project, I have to try plotting my data in many different
ways, and quickly. Plotting with scripts (matlab/gnuplot) is less efficient
in this case.
But the graphics and text capabilities of origin are yet to be enhanced.
That's why I chose metapost or asymptote to do graphics in manuscripts and
thesis.
If you are looking for |
|
c****n
发帖数: 21367 | 25 coding theory一般都不做finite length的情况，
天天asymptotics，天天channel assumption...
我是个外行，这个观察对嘛？请多多批判。
我所
的还 |
|
s*****y
发帖数: 1974 | 26 牛，沾点仙气
是 被有些人看得起， 不点名了。 可以去查查，2000前Hanzo几乎没有在Tran. Commun
.发过paper. 现在也是个灌水大牛，能混到现在这样，也不容易。
做过performance. 但只做performance没太大前途。最好的例子是MK Simon. 300+
journal papers. 去世前连个NAE member都没拿到。
performance，最近才publish，是个很古老（50+ years)的难题（同行知道），
asymptotic结果却非常漂亮。渴望被Proakis 6th edition 引用。 |
|
c****n
发帖数: 21367 | 27 unfortunately... for many practical, finite length coding schemes
it's hard to evaluate their performance
Shannon's theory works best for asymptotical cases... |
|
b****e
发帖数: 9 | 28 For diagram: xcircuit
for math: asymptote
These are the most powerful, flexible and beautiful tools I found.
And they are free. |
|
k**********g
发帖数: 989 | 29
好像有小学生讨论无穷大，为甚麽
lim x to +infinity ( (2 * x ) / x )
会等於二？反正都是无穷大，难道不是所有运算结果都是无穷大吗？
Define the asymptotic assumptions before we use the word "ideal". |
|
h****r
发帖数: 391 | 30 This is the reflection formula.
The proof is not complicated,
just using 2-multiple integral
transformation with a Jacobian
determinant. Actually we can
extend this result to any z that
is not 0 or a negative integer via
analytic continuation.You can see:
Special Functions
by Lebedev
or
Asymptotics & Special Functions
by F.Olver,Academic Press |
|
p**********y
发帖数: 61 | 31 来自主题: Mathematics版 - 文献求助 那位大哥大姐帮忙找一下这篇文献？
多谢了！
Title: Asymptotic ruin probabilities and optimal investment
Journal: Annals of Applied Probability
Year: 2003
请发到b**********[email protected]
good night~!~ |
|
m**a
发帖数: 1840 | 32 假设一个stationary Gaussian process， 它的spectrum （定义在[-\pi,\pi]上）为0的
部分的measure为2\pi\alpha. 那么是不是可以说，asymptotically, 我们在时域里只要
知道任意\alpha portion of the process，其余的部分就决定了。有没有那位大侠给指
点一下。 |
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B********e
发帖数: 10014 | 33 i don't think there is any explicit solution for such a complicated
expression
you may need do asymptotic analysis for any specific question |
|
r******n
发帖数: 88 | 34 正在改老板的老程序，碰到这个余误差函数很好奇是怎么求的。我比较wiki上面的
asymptotic expansion，发现和
这
个程序有点相似，但那个expansion是发散的。请哪位兄台指教一下，非常感谢！
REM this calculates erfc(X)
SUB Erfc(X#,Y#) STATIC
IF ABS(X#)<=1.7# THEN CALL Erf(X#,Y#) : Y#=1#-Y# : EXIT
SUB
X1#=ABS(X#) : XC1#=X# : XD1#=1#/(X1#+.5#/X1#) : Y#=XD1#
FOR I%=3 TO 10000
XC2#=X1#+.5#*(I%-1)/XC1#
XD2#=1#/(X1#+.5#*(I%-1)*XD1#)
|
|
v*c
发帖数: 42 | 35 suppose we know x_hat is aymptotic distributed with mean x and variance
sigma2.
here, x_hat is an estimator of x.
Now, we have integral (x_hat)dx, x from 0 to 1. Then how to obtain the
aymptotic distribution of this integral?
Thanks, |
|
s******h
发帖数: 539 | 36 How would you define the empirical estimator of \hat_f(Y)? |
|
|
|
f*******r
发帖数: 383 | 39 Please see attachment.
Any input is highly appreciated! |
|
k*********g
发帖数: 791 | 40 最puzzling藕的还是空间和物质的可分性；
物质不断地分下去，是什么？
这个古老的问题，已经puzzling藕N年了。。。
这个不需要物理学知识，完全是个纯逻辑问题、纯哲学问题，或者说纯数学问提；
空间的可分性，也很paradoxical；
其它的比较简单了；
藕斗胆评论几个：
1 ether exists；
以太无处不在；建议研究以太动力学，ether dynamics；
以太很难被直接观测，但是，在weak interaction的时候，是以太造成了W＋，W－，Z
2 电荷到底是什么？
什么东西都被看成是运动了、能量了，连质量都没有被放过；只有电荷是个例外；
what the hell is the charge？
藕speculate，电荷也是一种运动形式，跟spin自旋 很项似；
3 CQCD， computational quantum chromodynamics
量子色动力学，一个对付proton、neutron里面的quark的theory，是个呈现强烈非线性
的东西；故，没有exact solution，asymptotic之流也拿捏不定它；实验，对付p |
|
o*******w
发帖数: 349 | 41 直觉上很显然，怎么证明呢?
n
SUM i*Pr(i) is bounded by O(n^a) where a < 1
i
Pr(0), Pr(1), Pr(2), ... 是一个概率密度
大致有∶
因为 Pr(i) can be bounded by O(1/i^c) where c > 1 否则 SUM Pr(i) > 1（怎么证?）; e.g.
n
SUM 1/i = O(ln n)
1
只需考虑 SUM 1/i^(c-1) c<2 的情况, i.e. 1< c <2。则
n
SUM i*Pr(i) < SUM i*(1/i^c)
1
= SUM 1/i^(c-1) = O(n/n^(c-1))
= O(n^(2-c)) = O(n^a) where a = 2-c < 1 |
|
B****n
发帖数: 11290 | 42 This seems wrong. Consider the Pr(i)=c/(i*log(i)^2) i>=2, where c is a
constant which makes Pr(i) become a probability distribution.
Then the sum can not be bounded by O(n^a), where a<1
证?）; e.g. |
|
o*******w
发帖数: 349 | 43 感谢指教！
看来我只能得到
SUM i*Pr(i) = o(n) 了？
可能连这个结果都不一定 |
|
Q***5
发帖数: 994 | 44 This can be proved:
For any epsilon >0, there exists K, such that \sum_K^\infty i*P(i)<\epsilon
Let N big enough, such that K/N<\epsilon.
Now, for any n>N,
\sum_1^n i*P(i)/n <= (\sum_1^(K-1) K*P(i)+ n*\sum_K^n P(i))/n
epsilon< 2*\epsilon |
|
|
r*****z
发帖数: 906 | 46 metapost或者asymptote都可以胜任
一般来说，这类画图选编程式工具比较有效 |
|
G********n
发帖数: 615 | 47 Ramanujan Prize Winner 2010
ICTP's 2010 Ramanujan Prize has been awarded to Professor Yuguang Shi of the
School of Mathematical Sciences, Peking University. The prize is in
recognition of his outstanding contributions to the geometry of complete (
noncompact) Riemannian manifolds, specifically the positivity of quasi-local
mass and rigidity of asymptotically hyperbolic manifolds.
The prize is also in acknowledgement of the substantial contribution that
Professor Shi has made to mathematics in Ch... 阅读全帖 |
|
g*****h
发帖数: 15 | 48 College Algebra by Larson & Hostetler
DVDRip | MKV / AVC 692 Kbps | 720х544 | 29.97 fps | MP3 128 kbps | 8.75 GB
Language: English
Lecture Titles:
Prerequisites
P-1 Review of Real Numbers and Their Properties
P-2 Exponents and Radicals
P-3 Polynomials and Special Products
P-4 Factoring
P-5 Rational Expressions
P-6 Errors and the Algebra of Calculus
P-7 Graphical Representations of Data
Chapter 1 – Equations and Inequalities
1-1 Graphs of Equations
1-2 Linear Equations in in One Variable
1-3 Mode... 阅读全帖 |
|
i****g
发帖数: 3896 | 49 http://blog.sina.com.cn/s/blog_c24597bf0101b871.html
致谢：I would like to thank Prof. Shing-Tung Yau for suggesting the title of
this article, Prof. William Dunham for information on the history of the
Twin Prime Conjecture, Prof. Liming Ge for biographic information about
Yitang Zhang, Prof. Shiu-Yuen Cheng for pointing out the paper of
Soundararajan cited in this article, Prof. Lo Yang for information about
Chengbiao Pan quoted below, and Prof. Yuan Wang for detailed information on
result... 阅读全帖 |
|
x********i
发帖数: 905 | 50 Simon Brendle (born June 1981) is a German mathematician. He received his Ph
.D. from Tübingen University under the supervision of Gerhard Huisken (2001
) and is currently a professor at Stanford University.
In 2006 he constructed counterexamples to the Compactness Conjecture for the
Yamabe problem. He also gave a complete description of the asymptotic
behavior of the Yamabe flow. In 2007 he proved the Differentiable Sphere
Theorem (joint with Richard Schoen). In a joint work with Fernando Marqu... 阅读全帖 |
|
