EXBRIDENTIAL

So today what we're going to do is we're going to pick up where we left yesterday.

And we're going to try to work our way through a real gravitational wave detector.

I'll start off just by explaining some of the key technologies,

but then really today's talk is going to be kind of a tour through all the different data that we have,

how do we make sense with what are the limiting voice sources.

I'm hoping that there's time that we'll start to enter the quantum regime as a kind of gravitational wave detector.

And then tomorrow I think almost entirely, if I'm clear to me, what I'd like to do is to spend my last lecture on

roughly speaking the title would be Optomechanics in Gravitational Analysis.

But just how does optomechanics manifest itself?

Now again I have a great, great luxury of not having to develop any of the theory for you

because that's been done by people far more confident than I.

So I will concentrate on the experiments and as for the forms, please just interrupt the questions.

This is where we kind of left off yesterday.

I showed you that this is what happened in the first phase of LIBOR.

There's the red target sensitivity curve.

Actually I'm really feeling this light obviously in the other room.

And then I promised that I would walk you through what limits us to a curve like the red curve.

And of course the data curves are actually measurements made at the LIBOR detectors.

The blue curve in 2007 and then the green curve in 2010.

And I'll just tell you right off the bat that the main difference between the blue and green curves

was increase in laser power.

You can see that in this region of frequency space of typically about 100 Hz,

these detectors are limited by the shock noise.

Now I look at regularly trying to make connections with some of the theory that you've been hearing.

So you'll notice that in Arshad's lecture, the shock noise, what I refer to as shock noise,

was simply called imprecision.

And what he refers to as back-action, I'll call radiation pressure noise, exactly the same thing.

And Yandere will do that interchangeably too.

So that was the big difference.

Let me take a question over here.

Why is the green noise higher at low frequencies?

So let me just say something about the noise.

This is a snapshot of noise.

Remember these instruments measured for two years.

And it turns out that this low frequency part is pretty non-stationary.

So if I took a snapshot at a different time, it could be different.

And it is.

So you shouldn't pay too much attention to that.

In reality, when we try to do observations and measure H, strain, gravitational wave strain,

we don't do it in terms of spectral density.

We actually have a time series of basically two years of data.

So it's a very different game when we're analyzing.

These are just curves we put out for ourselves and for you guys as a measure of how well are we doing relative to design.

And if they help us, and you'll see this throughout my talk as these kinds of data curves will be showing up a lot,

they help us decide what's bothering our, what's limiting our sensitivity.

So that's a good question.

And in fact, many people ask, what are all these lines?

We also know what most of them are.

Many of them are calibration lines that we put in ourselves.