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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
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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!
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Regards,
Bob P.
I have no idea what any of it means, but I'm happy to help.
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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.
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.
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.
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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:
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!
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 :-) .
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.
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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 Einstein@home.To quote Einstein "theory teaches us what can be observed".
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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
Hmm,
Why are the graphs 5.1 and 13.3a flat lines? Or am I missing something?
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Thanks for publishing such a detailed status report!
It's a pity, that nothing was discovered so far :(
Michael
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Bruce AllenForum moderator
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Hmm,
Why are the graphs 5.1 and 13.3a flat lines? Or am I missing something?
5.1 is a flat line, because a detector in space far from our solar system would not be spinning or orbiting the sun and so there would be no frequency modulation due to its motion.
13.3a is not quite flat. Look at the vertical scale, and the zoom below.
13.3a/b is the frequency of a pulsar located directly over the Earth's orbital plane. There is no annual variation of the Earth's distance from this pulsar, so no annual frequency modulation. Just the (smaller) frequency modulation due to the Earth's rotation, shown in 13.3b.
Bruce
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Nice report! Something for everyone! I got to page 10 before my brain started to hurt.
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derekm
Team MacAddict
Thanks Bruce, Fascinating reading even though I don't fully understand all of it. Makes the project more interesting though, and nice to know the direction we are headed.
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Team MacNN - The best Macintosh team ever.
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
It's been 30+ years since I received my Physics degree and long years of hard work and raising a family have migrated Physics to the back burner of my life. But thanks to the amazing work and articulate analysis of Einstein@Home, there is growing hope that I may fully revive my Physics roots. Thank you all for your amazing work!!
Is there a projected schedule for the completion of the S4 analysis?
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There are only 10 kind of people in the world, those that understand binary and those that don't!
Outstanding report.
Interesting to note that LIGO Hanford is more sensitive than GEO600 on S3. Is GEO600 up to par on S4? What are some of the upgrades that are planned for LIGO Hanford, and how will they improve sensitivity?
I've been away on business since Sept 10 and I find a very pleasant document awaiting my perusal now that I'm back. I'm referring to the well written progress report that has appeared during my absence. I have read it through once and intend to digest it more fully in the coming weeks. I'm extremely pleased to be able to more fully understand the importance of the science to which I'm contributing. My personal prediction is that as more people visit the website and discover this report, there will be a steady stream of previously "diehard" Seti only crunchers who will suddenly realise that EAH is equally worthy of their support. As one of those who were canvassing for this type of progress report many months ago, let me say that the wait has been more than worthwhile. Well done - from a very satisfied contributor.
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Cheers,
Gary.
Does anybody know if and when this program will run smoothly with windows?Is anything being done to correct the problems?Thanks
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Does anybody know if and when this program will run smoothly with windows?
I only use windows boxes for running EAH. It runs absolutely magnificently under all versions of windows, 98, ME, 2K and XP. I can't say I've had a single problem with any of them.
Is anything being done to correct the problems?Thanks
How do you correct a non-existent problem? Might I suggest that your "problem", if you care to describe the actual symptoms you are experiencing, may in fact have nothing to do with the interaction between the science app and the OS. And you really couldn't have picked a less appropriate thread in which to tell us that EAH wont run smoothly on windows. Here's my suggestion. Go to the "Getting Started" message board and tell us precisely what the symptoms of your problem really are. Be very thorough in your description and I'm sure somebody very knowledgeable will be only too pleased to help you. I'm sure you really do have some problem. But you must learn to describe it fully and to do so in the appropriate forum.
Best of luck with it.
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Cheers,
Gary.
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
Hi all
The `unofficial` German translated Report is available at
http://www.cmds.tk
The German Team: Special:OffTopic made a good Job. Thx to all.
Special Thx to Reinhard Prix and Bernd Machenschalk for their help, motivation an corrections.
available: Adobe(TM) PDF & OpenDocument ODT
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Outstanding report.
Interesting to note that LIGO Hanford is more sensitive than GEO600 on S3. Is GEO600 up to par on S4? What are some of the upgrades that are planned for LIGO Hanford, and how will they improve sensitivity?
Improvements in sensitivity get harder and harder as you get closer to the design goal. We've made two key upgrades at Hanford this summer, to the 4km instrument, to make it more sensitive and get very near our design goal for our one-year run, starting Nov 5, 05. The first was to swap out a suspended test mass, one of the core optics of the long arm of the machine. This optic was too reflective, scattering some excess light out of the arm and spoiling the heating (thermal lensing property) of the cavity. We installed a better, less reflective optic. This is described (with some nice photos) at: http://www.ligo-wa.caltech.edu/ligo_science/vent_0605.html
Furthermore, we've been boosting the laser power incident on the 4km machine (and the others, as well), in order to reduce the noise at high frequency (so-called shot noise)
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Improvements in sensitivity get harder and harder as you get closer to the design goal...
Thanks, landry – looks like quite a chore swapping out a test mass! Surprising to learn that it takes about 5 weeks to reach operational pressure of 10^-9 torr, even with the partitioned enclosure. So if the old ITMX is no good, has anyone called dibs on it yet? :) Looking forward to S5!
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This may be the wrong place to ask this question. If so, I apologize. We are currently scanning the entire celestial sphere for pulsar signals. This seems like a diffuse search. Why don't we, at some point, focus a large effort in the direction of a single known pulsar? We would know precisely what frequency the signal should have, and we could concentrate a lot of computing power on one spot, thus digging deeper into the data.
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Brian
Al known pulsars are to far away to be detected by LIGO.
Thank you, Mark. After I had posted I realized that that was probably the reason. I'm very excited about LIGO and happy to be able to contribute in some way.
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Brian
Al known pulsars are to far away to be detected by LIGO.
While it is true that many of the known pulsars are farther away than we'd like, LIGO and GEO do target them for analysis. This is typically done with different code and search algorithms than Einstein@home, for example http://xxx.lanl.gov/PS_cache/gr-qc/pdf/0410/0410007.pdf (this preprint is a technical paper that was published in Phys Rev Letters).
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All known pulsars are too far away to be detected by LIGO.
While it is true that many of the known pulsars are farther away than we'd like, LIGO and GEO do target them for analysis.
Just to expand on what Mike Landry said: They are all too far away for the S4 search to get them. But S5 will have a shot at the Crab pulsar.
How do we know this?
The radio astronomers can tell us not only how fast a pulsar is spinning, but also how fast it's spinning down. (The frequency slowly decreases with time.)
As noted in the "Am I on the right track?" thread, a pulsar that is emitting gravitational waves will spin down as it loses kinetic energy of rotation. If you assume that all of that observed energy loss is emitted as gravitational waves, you can plug in the distance to the pulsar and get a number for the strength of the gravitational wave signal. This "spindown limit" for the Crab pulsar is high enough that S5 will be able to see it if all the spindown is from gravitational waves.
In real life, we know that's overly optimistic. Radio pulsars are certainly emitting radio waves after all, so only some fraction of the spindown could be due to gravitational waves. For the Crab it's probably a pretty small fraction of the spindown, because it's in a big glowing nebula that it is constantly stirring up, as you can see from Chandra and Hubble.
Also, the results of the all-sky search for unknown pulsars that Einstein@Home is doing can be phrased in terms of limits like that. It's trickier in this case, but we're working on it.
Hope this helps,
Ben
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Excuse me please for a petty question but I am don't fully understand this “phrase block� from chapter nine “How does the Einstein@Home S3 search work?�:
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.
If I understood right:
60 ten-hour segment / all data x 20 SFTs / ten-hour segment = 1200 x (ten-hour segment x SFTs / all data x ten-hour segment) = 1200 SFTs / all data…
…but not each file…
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Excuse me please for a petty question but I am don't fully understand this “phrase block� from chapter nine “How does the Einstein@Home S3 search work?�:
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.
If I understood right:
60 ten-hour segment / all data x 20 SFTs / ten-hour segment = 1200 x (ten-hour segment x SFTs / all data x ten-hour segment) = 1200 SFTs / all data…
…but not each file…
I would interpret that as:
The SFT's, being Fourier transforms gives you a power vs. frequency data, derived from amplitude vs. time.
Define Frequency Bands
The total range of frequencies is 1500.5 - 50 = 1450.5 Hz.
Chop this range into 0.5Hz wide blocks giving 2 * 1450.5 = 2901 blocks.
Add the wings, hence overlap, to 0.8Hz wide blocks, still 2901 blocks though.
Define Time Periods
Divide your best 600 hours of data into 30 minute periods = 600/(0.5) = 1200 periods.
Get Power vs. Frequency From Each Time Period
Do a Fourier transform on each period.
Look at a Given Frequency Band Across all Periods
For a given 0.8Hz frequency band, chop the data out of each of the transforms.
Repackage these by frequency band .. that is construct a file for each 0.8Hz frequency band ( 2901 files ), each of which contains the Fourier transform data obtained from each of the 30 minute segments of the 600 best hours. Hence 1200 data 'subsets' in each file.
Search For Signals
Hand them out for crunching.
(edit) So each 'SFT file' actually contains pieces of 1200 separate Fourier Transforms. The 2901 files handed out for analysis are 'externally indexed' by frequency, but are 'internally indexed' by time period. As opposed to the original transforms which as a set were externally indexed by time period, but internally could be divided by frequency. Your just cutting up the data set by 'rows' instead of 'columns'.
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"I have made this letter longer than usual, because I lack the time to make it short." - Blaise Pascal
I would interpret that as:
Thank you for explanation!
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