S3 Analysis Summary Questions, Answers, Comment and Discussion

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Bruce Allen
Bruce Allen
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Topic 189872

I have just posted the long-promised first report on the Einstein@Home S3 analysis. Please use this thread for questions, answers, comments and discussion.

Bruce

rbpeake
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S3 Analysis Summary Questions, Answers, Comment and Discussion

Quote:

I have just posted the long-promised first report on the Einstein@Home S3 analysis. Please use this thread for questions, answers, comments and discussion.

Bruce

This is just wonderful! :D I feel like I've gone to heaven! ;)

Now there is a lot of "meat" to this project for me, and that is a bigger incentive than the point system for sticking with it for the long term (although the points are fun to track one's progress on a day-to-day basis, and get a sense of one's contribution to the project, but they are not a great incentive for a long-term commitment to a project).

Thank you so much!

Regards,
Bob P.

MattDavis_2
MattDavis
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I have no idea what any of it

I have no idea what any of it means, but I'm happy to help.

Jquake
Jquake
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Excellent! Above and beyond

Excellent! Above and beyond the call to duty. Thanks for the marvelous report http://einstein.phys.uwm.edu/PartialS3Results/

The writers(s) have succeeded in a very difficult job of explaining the very technical science and math in "undergraduate" terms. Sharp, brief, ample and to the point, and nothing unnecessary or uninteresting. The pictures, diagrams and text all work together very well. There is a wealth of linked footnotes and deeper technical material.

I liked Ch 2, the brief overview of the way the LIGO instrument works. The essential components of the instrument are illustrated to show how gravitational waves generate the signal that Einstein@Home helps analyze.

Chapters 5 through 14 give a wonderful explanation of the nature of the raw data, signal levels, noise, and limits of detectability. One example: The Earth's rotation and movement around the sun complicate an ordinary FFT analysis of the data. This motion has to be -- and is -- compensated for in the software we use. A side effect is that there are always small areas in the celestial sphere where instrument sensitivity is reduced. (Fortunately, these points are not fixed; they change as the Earth moves and rotates.) There are local noise sources, such as power-grid 60Hz and harmonics that are attended to.

Chapter 9, "How does the Einstein@Home S3 search work?" gets to the meat. Here's part of the first few paragraphs.

Quote:

The Einstein@Home search in the LIGO S3 data set starts with the 600 'best' hours of S3 data. The most sensitive instrument operating during S3 was the LIGO Hanford Observatory 4-km detector, so we use that data set. This is broken up into 60 segments totaling ten hours of data each....

Each data segment is then prepared as follows. The data are calibrated in the time domain, using a method described in. This produces a time-domain data stream sampled 16384 times per second. Then 30-minute chunks of contiguous data are windowed and Fourier Transformed, producing 'Short Fourier Transform' (SFT) data sets. Known line features in the instrument are removed. The end result is 2901 SFT files, each of which covers an (overlapping) band of about 0.8 Hz. Each file contains 1200 Fourier Transforms (60 ten-hour segments * 20 SFTs/ten-hour segment). The frequency range covered is from 50.0Hz to 1500.5 Hz.

An Einstein@Home host (for example, YOUR home PC) downloads one of the 2901 SFT files. Each of these contains 0.5 Hz of usable data, plus 'wings' on either side.

Go to the link for more. It's a delight.

Honza_21
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Not saying that I undestand

Not saying that I undestand all what status report includes but great stuff. Definitely worth reading - saying a lot about Einstein@home science, data sets and it's future.

Thanks for the report.

Jquake
Jquake
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I can't resist quoting this

I can't resist quoting this fact about the LIGO instrument. The mirrors and beam splitter the end of the arms are 4 km (2.48 miles) apart (see Ch 2). It is the relative movement of the mirror/beam splitter pair that is measured. The sensitivity is proportional to the length divided by how small a movement of the mirror can be detected. We know the length. So how small a motion of the end point can be measured? This from Ch 8 of the Report:

Quote:

The quantity h that appears on the vertical axis of these graphs is called "strain". To appreciate the remarkable sensitivity of these instruments, refer back to the schematic diagram of an interferometric gravitational wave detector shown earlier. The strain h is the fractional change in the apparent arm length that would be caused by the passage of a gravitational wave. Thus a strain h = 10^(-21) in the LIGO 4km arms corresponds to a change in the arm length of 4x10^(-18) meters. This is about one thousand times smaller than the size of an atomic nucleus!

Currently, LIGO is the most sensitive gravitational wave detector operating anywhere in the world, and is operating close to design sensitivity. A long data taking run (S5) at design sensitivity is anticipated to begin late in 2005.


(my emphasis)

Wow!

ragnar schroder
ragnar schroder
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RE: I have just posted ...

Quote:
I have just posted ... [url=http://einstein.phys.uwm.edu/PartialS3Results] Bruce

It's just wonderful when cutting edge science is made so comprehensible.

Physicists usually scare me witless with their "spinors", "twistors", "Lie groups", "complex manifolds", "Hamiltonians", "calculus of variations" and what not.

Simple signal processing is familiar to "the rest of us".

Thanx!

Greetings, Mr. Ragnar Schroder, Bachelor of Science, math major :-) .

AnRM
AnRM
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Thanks all for such a great

Thanks all for such a great comprehensive and layman friendly report. It is worth the wait! I hope the S4 run report proves to be even more intresting! Thanks again.....it will help keep the intrest in the project alive and well. Cheers, Rog.

tullio
tullio
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RE: RE: I have just

Message 16461 in response to message 16459

Quote:
Quote:
I have just posted ... [url=http://einstein.phys.uwm.edu/PartialS3Results] Bruce

It's just wonderful when cutting edge science is made so comprehensible.

Physicists usually scare me witless with their "spinors", "twistors", "Lie groups", "complex manifolds", "Hamiltonians", "calculus of variations" and what not.

Simple signal processing is familiar to "the rest of us".

Thanx!

Greetings, Mr. Ragnar Schroder, Bachelor of Science, math major :-) .


There would be no search for gravitational waves without Einstein's General Theory of Relativity, heavily based on tensor calculus. See e.g. Peter G. Bergmann's (a disciple and coworker od Einstein) "The riddle of gravitation" (1968). In 1970 I published an article by Bergmann in the Mondadori's Yearbook of Science and Technology which gave an account of the first attempts to search for gravitational waves made by Joseph Weber at the University of Maryland with instruments far less advanced than those used in quote Einstein "theory teaches us what can be observed".

Tom Awtry
Tom Awtry
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Phd. Allen & Co-authors - A

Phd. Allen & Co-authors - A sincere “Thank You” for authoring for what I feel is a highly complicated paper, in terms a layman, such as myself, can mostly comprehend with relative ease. After several readings, I feel I have been educated more than I have over the past month and a-half of searching through and reviewing posted threads and written articles within this site and other web sites. You are truly Master's of diction.

Thank You,
Tom

Paul D. Buck
Paul D. Buck
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Hmm, Why are the graphs

Hmm,

Why are the graphs 5.1 and 13.3a flat lines? Or am I missing something?

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