Monday, September 21, 2009

Update on the GEO 600 "Mystery Noise"

If you recall, the gravitational wave experiment GEO 600 had reported unexplained noise above the theoretical prediction. Craig Hogan suggested this unexplained noise might be an effect of quantum gravity. This does not work easily in a straightforward setting but necessitates the introduction of a new version of holography. I previously commented on Hogan's theoretical framework in my post "Holographic Noise."

Hartmut Grote from the GEO 600 collaboration kindly replied to my inquiry about the status and let me know

"In GEO600 we recently found that there is no more unexplained noise in the region from 150 to 300 Hz, if we use a different readout method, which points to the fact that the unexplained noise in this region might be associated with the former readout method, and not be of any fundamental type (i.e. holographic).

However, this does not change much in the current discussion of wether GEO is limited by holographic noise or not, as Craig Hogan already agreed some time ago, that the low-frequency rise in the noise in GEO would not be holographic noise. Hogans latest prediction is a flat (in frequency spectrum) noise, and we have not yet made an experimental statement about this in GEO.

So in summary:
Mystery noise in GEO disappeared in the region 150-300Hz, but Hogan anyway was not suggesting any more that holographic noise would be limiting GEO at these frequencies since a while."

Thus, a big bunch of the "mystery noise" has found a non-mysterious explanation. It is not entirely clear yet how much is left to explain and whether there will be anything mysterious about what is left. GEO600 might then just about reach the required sensitivity to test the remainder of Hogan's prediction. The experimentalists plan to improve the sensitivity in the coming year and hope to eventually be able to settle the question.

23 comments:

stefan said...

Dear Bee,

thanks for the update!
Cheers, Stefan

Daniel de França MTd2 said...

Hi Bee,

will you post an explanation on your new bimetrical theory? I am eagerly waiting for your explanations and inspirations!

Bee said...

Hi Danie,

Well, I just posted a summary on the arxiv

http://arxiv.org/abs/0909.3456

Unfortunately that's presently all I have to say. I wish I had already made more contact to observations, but this has been hindered by me moving overseas and lacking a collaborator. Best,

B.

Bee said...

Oops, there was an 'l' missing.

Giotis said...

I suppose you can treat the modified EMT and equations semiclassically. Have you tried this already Bee?

Neil' said...

Since there is a CMB of EM waves from the dense beginning of the universe, I long suspected on my own that there should be a gravitational wave background from what happened. It would be red-shifted the same amount from any distance, but it wouldn't have to come from the same special moment (when the universe condensed from plasma so light could go through.)

The subject has already been delved into, see e.g. http://www.aip.org/pnu/2007/split/809-1.html. I figure Hogan et al would have considered it, but it's interesting to throw that issue into the mix.

Bee, I am impressed with how much you can accomplish with a high ratio of words to equations! ("Antigravitation") It's the sort of thing I'd write (and have) myself.

I can imagine special matter that repulsed ordinary matter instead of attracted it, but two other ideas that people played with, have problems:
1. Matter' that is repelled by ordinary matter (or even, that doesn't fall the same rate.) That violates the core idea of the equivalence principle, as you note. But, that doesn't stop some from speculating that antimatter falls at a different rate.
2. Matter' that is truly "negative" (should effectively count as -m in general.) If we tried to extract the "negative energy", we couldn't because conversion into EM waves must produce fields of positive energy density.

Zephir said...

In Aether model gravitational waves are related to light waves in simmilar way, like underwater (sound) longitudinal waves to transversal surface waves: they're way way faster, but weaker, because they spread in higher number of dimensions and they disperse fast at CMB scale. Tangible evidence of gravitational waves shielding in 6D is Casimir force, in 9D strong nuclear force.

In AWT CMB photons are gravitons expanded during inflation and gravitational waves collapsed during the same event. Gravitational waves are longitudinal portion of the same noise, which forms dual transversal microwaves of CMB. The observation of noise appears rather invariant to holographic theory, because if we would observe harmonic gravitational waves, we could consider them as an evidence of holographic theory as well.

Zephir said...

This shot of underwater nuclear explosion illustrates, what we should observe during passage of gravitational waves through gallaxy: a temporal change in density of CMB noise from all directions at the same moment, instead of occurrence of harmonic waves.

http://www.youtube.com/watch?v=SHoXJuv8tDM

Note that sound waves are dispersing fast, so it's improbable, we could observe gravitational waves at longer distance, then the wavelength of CMB.

Matt said...

Dear Bee,

Interesting how timely this post is. The LIGO collaboration (of which GEO is part of) just put out a paper on a search for Gravitational Wave background from Inflation. It covers a search for Stochastic Waves from the 5th LIGO Science Run that collected a year's worth of triple-coincidence data. See http://ligonews.blogspot.com.

Also one can follow the daily noise hunting for the LIGO interferometers in Washington State and Louisiana, since their elogs are publicaly viewable (read only).

Bee said...

Hi Giotis: Sorry, I don't know what you are referring to with "EMT"?

Giotis said...

Energy-Momentum Tensor. You know, I meant to treat the model semi-classically i.e. "G = < T >"

Bee said...

Ah. I still don't know what model who should treat semi-classically?

Giotis said...

I mean for example to take a scalar field in this classical bimetric background and quantize it in order to check how this background affects the quantum field and vice versa.

Can you treat this way?

Bee said...

Giotis: It's a classical model. It's as classical as ΛCDM. The stress energy is that of the usual cosmic fluid. And I'm not tremendously interested in scalar fields. Best,

B.

Phil Warnell said...

This is all reminiscent of the days when Penzias and Wilson suspected bird droppings where responsible for the noise in their microwave antennae and initially did more sweeping then thinking. With the mention that the GEO 600 group is now using what they refer to as a different read out method, let’s hope they aren’t throwing the baby out with the bathwater or here some unexpected phenomena out with their knob twisting. Sometimes experimentalists tend to act more like engineers and think Murphy is out to get them, rather than help them along. :-)

Best,

Phil

Zephir said...

I'm not saying', holographic theory is complete BS (in AWT no theory is complete BS, until it remains strictly logical and supported by at least pair of postulates at observational level) - but until we cannot explain gravitational noise to our grandmothers, I'd consider the simplest possible classical models of reality first.

As we can see, one hundred year of positivism and platonism in science development lead into pronounced unbalance between formal and non-formal understanding of reality. We don't understand even connections, which are quite trivial from perspective if intuitive understanding. Even worse, mainstream scientists proactivelly refuting to consider these connections under hope, fastly growing pile of formal theories and their variants would introduce some clue into it. Whereas every new theory makes such understanding more difficult, instead.

It's not difficult to explain such naive stance: intuitive understanding of reality is opened for everyone, while understanding of these theories is difficult and time consuming and it keeps informational barrier and superiority of mainstream science before eyes of layman world. It means, position of AWT deniers is logical, predictable and analogous to Catholic Church stance before years - but untenable with respect to long term perspective.

Plato said...

Pinpointing a time for gravitational wave production is an important step in our assumption of what information allows us to push back that perspective on time?

So what sources in conjunction with this perspective also qualifies information that may be seen in relation to gravitational wave science to support the contention in relation too Supernova explosions?

Is there any such correlations?

In their supernova model, the bounce, the time of the first gravitational waves, occurs about 5 milliseconds before neutrino emission. So looking back at their data, gravitational wave hunters should focus on that point in time. See:Supernova Starting Gun: Neutrinos

Uncle Al said...

Quantized gravitation may have embraced some non-ugly existence,

http://physics.aps.org/articles/v2/79

Will testable implications accompany a published hectare of explanations?

stefan said...

Hi Neil,

concerning the "Cosmological Gravitational-Wave Background", the recent LIGO paper Matt has mentioned is this one: "An upper limit on the stochastic gravitational-wave background of cosmological origin". You can access a preprint of the paper as "LIGO Document P080099-v3" from the LIGO document server.

Actually, to my knowledge, the GW background is stronger at longer wavelengths, or lower frequencies, so GEO with its comparatively shorter arms may be less sensitive to it than the installations in Hanford and Louisiana.

Best, Stefan

Phil Warnell said...

Hi Bee,

I must tell you the most interesting thing I find about all this, is that we appear to have once again entered a period where theory holds more sway than experimental evidence. The fact is since the first running of all these experiments, there has been no detection of gravitational waves. Instead of them then being seen as less likely to exist, it is trumpeted as a triumph, sighting that it tells us more about their nature and that of the universe. Looking at the paper on all this, it appears to me the number of credited researchers involved far exceeds the amount of meaningful data contained.

If we look back more than a century ago, with the Michelson-Morley experiments not discovering the ether, there where many like Lorentz, Poincare and Fitzgerald that took a similar position; where it was only Einstein who looked straight into the mirror of reality to consider what this might be telling us. Despite this experience it appears to me that science has demonstrated itself in this respect to be no different than any other human endeavour, where not only is evidence ignored as to have preserved what we believe to be true, yet also the lessons of history.

Best,

Phil

Phil Warnell said...

Hi Bee,

Just as a postscript to what I said earlier.

Einstein was on a roll in 1905, with realizing that things of substance are limited in their speed of propagation and that light having an undeniable particle component. A lot since has come out of those two realizations, which I not only see as a challenge to his modern contemporaries, yet also as a lesson as to how they are achieved.

Best,

Phil

Plato said...

While considering the standard model and the integration of gravity within that context, it is not an un-noble thing to "find a time" where all four forces are considered one?

Best,

Matt said...

Stefan,

You are correct that the GW background is stronger in the lower frequencies, though I cannot recall the exact reason why. What I can say is that the low frequency (<40Hz) noise of large scale GW interferometers is dominated by seismic noise. This noise is heavily attenuated by passive isolation systems (springs & dampers) as well as active feedback loops, but there are still avenues for improvement.

GEO600 is undergoing an upgrade which includes some complicated suspension systems that are to further isolate the mirrors from ground motion. Virgo already has an advanced design of these suspensions installed, and its noise curve is noticeably better at low frequencies. Rai Weiss gave a talk at Fermilab this past spring, partially discussing what it would take to build an interferometer to look for Hogan's noise source. If my memory serves me correctly, it would not need to be a full scale (4km) machine, but with FANTASTIC (better than current incarnations) low frequency isolation.