S5 early results paper

Simplex0
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RE: Yes, and no

Message 93307 in response to message 93303

Quote:

Yes, and no respectively. The interferometers are working at their design specifications and are correctly reporting no detections above a certain level. It is operating just above the threshold of detection of the most 'obvious' or 'best case' continuous waves from the rotating neutron stars ( at the specified frequencies ). There is confidence in the data analysis, specifically :

Cheers, Mike.

Thank you Mike!
So the lack of signals could just be that they are to faint to be detected.

Mike Hewson
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RE: Even the current

Message 93308 in response to message 93304

Quote:
Even the current "Enhanced LIGO" upgrade (S6 run is supposed to start this summer) should help. The sensitivity should increase by a factor of 2, so the volume of space covered increases by a factor of 8. Not too bad.


Hmmmm .....

[ lowest detection limit quoted in this S5 report ]

divided by

[ maximum expected signal quoted in the limits paper ]

= 3 x 10(-24) / 1.6 x 10(-24)

= 1.88

< 2

So I wonder what odds the bookies ( Ladbroke's maybe ) are giving on Enhanced LIGO with S6 then? :-)

Cheers, Mike.

( edit ) I'm pretty sure it started out as 500 to 1 in 2004 ( detection by 2010 ). I think it's single figure odds now.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

Simplex0
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So even with the new more

So even with the new more sensitive detector you will only be able
to detect the strongest signal you are counting fore.

That's make me wonder why you built the first detector at all or have something
change during the time of the experiment?

Bikeman (Heinz-Bernd Eggenstein)
Bikeman (Heinz-...
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RE: So even with the new

Message 93310 in response to message 93309

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So even with the new more sensitive detector you will only be able
to detect the strongest signal you are counting fore.

That's make me wonder why you built the first detector at all or have something
change during the time of the experiment?

Well it's not that you build a whole new detector, it's upgrading existing existing ones. You start with something that is close to state-of-the-art (and affordable enough to get funding...), and then you learn how to improve it, demonstrate that you can handle the instrument and get more funding. Some of the upgrades that are installed now were not discovered at the time the original LIGO was conceived, so "doing it like now in the first place" was no option.

Also, we are discussing here a specific form of gravitational waves, continuous waves like those probably generated by pulsars with a hump. There are other forms as well like bursts which might be detectable by current equipment, but those events don't happen every day in our vicinity (like supernovae and whatever causes gamma ray bursts). And even the non-detection tells us something (an upper bound on GW amplitudes). So it's not in vain.

CU
Bikeman

Simplex0
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I see. Thank you

I see. Thank you Bikeman.

Maybe you could considere to get a machine like this :)

Mike Hewson
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RE: Maybe you could

Message 93312 in response to message 93311

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Maybe you could considere to get a machine like this :)


That's exactly the sort of machine we want! :-)
What a terrific explanation of the project by Mr Vickers in that thread by the way. If I wasn't such an Einstein@Home freak I'd probably go for that project - stellar stream mapping/modelling using the Sloan survey.

Cheers, Mike.

( edit ) I'm clearly getting old, or some relativistic effect perhaps. Time does seem to fly - Enhanced LIGO is soon to take data in the near future ?!

( edit ) This is the latest offering, that refers to timing of S6, on Enhanced LIGO that I could find.

( edit ) Here's the summary paragraph from that paper :

Quote:
Initial LIGO has finished a two-year long data run with its three interferometers operating at their design sensitivity. The LIGO Scientific Collaboration is completing joint analysis of this data with the Virgo Collaboration. Following the S5 data run GEO600 and H2 have continued running in ‘astrowatch mode’, to observe for gravitational waves until the LIGO and Virgo detectors are upgraded. The Enhanced LIGO upgrades to H1 and L1 are nearly complete. The next LIGO data run, S6, is planned for mid-2009 with about twice the sensitivity of S5. In parallel, construction of Advanced LIGO has begun. Installation and commissioning of Advanced LIGO at the LIGO sites will commence at the conclusion of S6 in 2011. Advanced LIGO data collection could begin as early as 2014. When fully commissioned, Advanced LIGO will be sensitive enough to make multiple gravitational-wave detections per year.

I have made this letter longer than usual because I lack the time to make it shorter. Blaise Pascal

tullio
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Here is an abstract from

Here is an abstract from "Nature" magazine:
A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations1. Direct measurements of the amplitude of this background are therefore of fundamental importance for understanding the evolution of the Universe when it was younger than one minute. Here we report limits on the amplitude of the stochastic gravitational-wave background using the data from a two-year science run of the Laser Interferometer Gravitational-wave Observatory2 (LIGO). Our result constrains the energy density of the stochastic gravitational-wave background normalized by the critical energy density of the Universe, in the frequency band around 100 Hz, to be <6.9 times 10-6 at 95% confidence. The data rule out models of early Universe evolution with relatively large equation-of-state parameter3, as well as cosmic (super)string models with relatively small string tension4 that are favoured in some string theory models5. This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis1, 6 and cosmic microwave background7 at 100 Hz.
Tullio

rbpeake
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A bit off topic, and sorry if

A bit off topic, and sorry if I missed it, but what are the more immediate plans for E@H following the completion of the S5R5 crunching in approximately 2 months?

ABP1 will continue I am sure (with more and more GPU power, hopefully! ;), and maybe another run of S5 data?

Thanks!

tullio
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RE: A bit off topic, and

Message 93315 in response to message 93314

Quote:

A bit off topic, and sorry if I missed it, but what are the more immediate plans for E@H following the completion of the S5R5 crunching in approximately 2 months?

ABP1 will continue I am sure (with more and more GPU power, hopefully! ;), and maybe another run of S5 data?

Thanks!


The LIGO site gave this message in June:
R5S6
Tullio

Mad_Max
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When do you plan to publish

When do you plan to publish the first results of the S5R5 analysis? It is more than half year since the end of the calculation. Time for post-processing data and writing the short article was enough I think...
And this is the most interesting portion of the data. S5R6 just glanced at higher frequencies (if I remember right 1000-1200 Hz), where there are no known pulsars. So that no special interest (the expected result - again make sure of non-existent of such pulsars within the Availability of sensors)
And Global Correlation runs using the same S5 dataset and give only a small improvement in sensitivity (by a new method of analysis) compared with S5R5.

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