Archive for the ‘News’ Category.

[MADS] Law of Total Variance

This simple law, despite my trial of full text search, was not showing in ADS. As discussed in systematic errors, astronomers, like physicists, show their error components in two additive terms; statistical error + systematic error. To explain such decomposition and to make error analysis statistically rigorous, the law of total variance (LTV) seems indispensable. Continue reading ‘[MADS] Law of Total Variance’ »


The wikipedia-like repository for mathematical “tricks” has now gone live. Their mission statement:

The main body of the Tricki will be a (large, if all goes according to plan) collection of articles about methods for solving mathematical problems. These will be everything from very general problem-solving tips such as, “If you can’t solve the problem, then try to invent an easier problem that sheds light on it,” to much more specific advice such as, “If you want to solve a linear differential equation, you can convert it into a polynomial equation by taking the Fourier transform.”

[MADS] Chernoff face

I cannot remember when I first met Chernoff face but it hooked me up instantly. I always hoped for confronting multivariate data from astronomy applicable to this charming EDA method. Then, somewhat such eager faded, without realizing what’s happening. Tragically, this was mainly due to my absent mind. Continue reading ‘[MADS] Chernoff face’ »

DOE Petascale Data Analysis Program

Woncheol Jang pointed me to the following web site describing a proposal opportunity at DOE that may be of interest to readers of this list:

Mathematics for Analysis of Petascale Data

The Office of Advanced Scientific Computing Research (ASCR) of the Office of Science (SC), U.S. Department of Energy (DOE), hereby announces its interest in receiving grant applications for research addressing the mathematical challenges involved in extracting insights from extremely large datasets (“petascale data”) and investigating fundamental issues in finding key features and understanding the relationships between those features.

All applications should address the potential for advances in mathematical methods or numerical algorithms and not just the application of methods and algorithms to a specific science problem, no matter how challenging.

This solicitation seeks applications for basic research in mathematical models, methods and tools for the representation, analysis, and understanding of petascale data.

They specifically mention data from physics simulations and observational data from cosmology as examples in the description.

Letters of Intent (required) are due 15 April, proposals are due 29 May. $4M is available for FY09; awards may be for up to 3 yr.

[Announce] Heidelberg Summer School

From Christian Fendt comes this announcement:

First Announcement and Call for Applications

The “International Max Planck Research School for Astronomy & Cosmic Physics at the University of Heidelberg” (IMPRS-HD)

announces the

— 4th Heidelberg Summer School:

— Statistical Inferences from Astrophysical Data

— August 10-14, 2009

Continue reading ‘[Announce] Heidelberg Summer School’ »

[Announce] AstroStat Summer School at Penn State

From Jogesh Babu comes this announcement:

Summer School in Statistics for Astronomers V
June 1-6, 2009
Penn State University

Continue reading ‘[Announce] AstroStat Summer School at Penn State’ »

iFish in the archive

The iPhone App Store has a couple of apps that make life significantly easier for those of us inundated and overwhelmed by the stream of daily arXiv preprints. These are and, both providing a means to browse and search the arXiv preprint database and both selling for 99c with the first selling for 99c and the second free. Check them out! The former even lets you save papers for off-line reading.

For me at least, the hardest part of going through the arXiv emails every day was to pick out the interesting papers in the deluge of text. These apps do the right thing and segregate the categories and highlight the titles. Fitts’ Law in action — suddenly the daily ritual is orders of magnitude more pleasant!

systematic errors

Ah ha~ Once I questioned, “what is systematic error?” (see [Q] systematic error.) Thanks to L. Lyons’ work discussed in [ArXiv] Particle Physics, I found this paper, titled Systematic Errors describing the concept and statistical inference related to systematic errors in the field of particle physics. It, gladly, shares lots of similarity with high energy astrophysics. Continue reading ‘systematic errors’ »

Circumspect frequentist

The first issue of this year’s IMS bulletin has an obituary, from which the following is quoted. Continue reading ‘Circumspect frequentist’ »


The year 2009 is the Darwin bicentennial and the sesquicentennial of the publication of the Origin of Species, but, um, even more importantly, it is the International Year of Astronomy, celebrating 400 orbits since Galileo started to look through a telescope.


I do not rely much on my cell phone. It functions as a tool for confronting emergencies. On the other hand, it seems like people do lots of things with their smart phones and I like to add one thing to your “what I do with my phone.” Continue reading ‘Wapedia’ »

Borel Cantelli Lemma for the Gaussian World

Almost two year long scrutinizing some publications by astronomers gave me enough impression that astronomers live in the Gaussian world. You are likely to object this statement by saying that astronomers know and use Poisson, binomial, Pareto (power laws), Weibull, exponential, Laplace (Cauchy), Gamma, and some other distributions.[1] This is true. I witness that these distributions are referred in many publications; however, when it comes to obtaining “BEST FIT estimates for the parameters of interest” and “their ERROR (BARS)”, suddenly everything goes back to the Gaussian world.[2]

Borel Cantelli Lemma (from Planet Math): because of mathematical symbols, a link was made but any probability books have the lemma with proofs and descriptions.

Continue reading ‘Borel Cantelli Lemma for the Gaussian World’ »

  1. It is a bit disappointing fact that not many mention the t distribution, even though less than 30 observations are available.[]
  2. To stay off this Gaussian world, some astronomers rely on Bayesian statistics and explicitly say that it is the only escape, which is sometimes true and sometimes not – I personally weigh more that Bayesians are not always more robust than frequentist methods as opposed to astronomers’ discussion about robust methods.[]

[SPS] Testing Completeness

There will be a special session at the 213th AAS meeting on meaning from surveys and population studies (SPS). Until then, it might be useful to pull out some interesting and relevant papers and questions/challenges as a preliminary to the meeting. I will not list astronomical catalogs and surveys only, which are literally countless these days but will bring out some if they change the way how science is performed with a description of the catalog (the best example would be SDSS, Sloan Digital Sky Survey, to my knowledge). Continue reading ‘[SPS] Testing Completeness’ »

“Thanks to Henrietta Leavitt”


The CfA is celebrating the 100th anniversary of the discovery of the Cepheid period-luminosity relation on Nov 6, 2008. See for details.

[Update 10/03] For a nice introduction to the story of Henrietta Swan Leavitt, listen to this Perimeter Institute talk by George Johnson:

[Update 11/06] The full program is now available. The symposium begins at Noon today.

Astroart Survey

Astronomy is known for its pretty pictures, but as Joe the Astronomer would say, those pretty pictures don’t make themselves. A lot of thought goes into maximizing scientific content while conveying just the right information, all discernible at a single glance. So the hardworkin folks at Chandra want your help in figuring out what works and how well, and they have set up a survey at Take the survey, it is both interesting and challenging!