When will LIGO be sensitive enough to detect gravitational wave background?

[petergreat]

Advanced LIGO, scheduled to start in 2014, is believed to be able to detect gravitational waves from stellar sources. According to our best current models, does Advanced LIGO stand any chances of detecting the stochastic GW wave background? And even measure its temperature? (No more than 0.9K according to The Early Universe.)

 

[nicksauce]

Hi,

This past Friday actually I went to a talk about LIGO and advanced LIGO. The answer given to this question was "I wouldn't bet on it".

Edit: I guess to be more specific, I think what he said was that there might be certain cases of models for which you would see something, but you probably won't for the usual models. My memory is a bit hazy though. There is also a future project called Big Bang Observer which would look for that sort of thing, although it is highly speculative right now.

 

[A/4]

It's my understanding the LIGO itself is just on the cusp of possible detection, let alone aLIGO. The instrumentation has been tuned to within an order of magnitude of the predicted strain introduced by the polarization modes (about 10^-23 m or so). If you ask LIGO people what is the most likely first detection source, they'll tell you: any of them!

 

[marcus]

It's my understanding the LIGO itself is just on the cusp of possible detection,...

Just to be very clear, I don't think the original poster Peter was asking about LIGO's ability to detect gravitational waves from any of various sources. But your post sounds as if you think he was asking that kind of general question and as if you are responding.

Unless I'm mistaken, Peter was asking specifically about the ability to detect background GW.

That is, GW analogous to the microwave background----but from an even earlier era, nearer the start of expansion.

 

[petergreat]

It's my understanding the LIGO itself is just on the cusp of possible detection, let alone aLIGO. The instrumentation has been tuned to within an order of magnitude of the predicted strain introduced by the polarization modes (about 10^-23 m or so).

Measure a displacement of 10^-23 meters? Are you sure you are right? This is way shorter than the equivalent length scale of the LHC energy, which is around 10^-19 m if I'm correct.

I also want to know some technical details about LIGO. How many times does the laser beam go across the 4km vacuum tube? (I suppose they do use multiple reflection as in Michaelson-Morley?)

Thanks for answering.

P.S @Marcus Yes I'm asking about GW background, since its temperature contains information about the degree of freedom at Planck scales, which will tightly constrain, or even test, GUT and quantum gravity theories.