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## Holographic Noise in GEO600?

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### Holographic Noise in GEO600?

Contents of this presentationContents of this presentation

Stefan Hild

for the GEO600 team

16th ILIAS WG1 meeting, July 2008, Birmingham

Articles on Holographic Noise available on arXiv:

arXiv:astro-ph/0703775v4

arXiv:0706.1999v2

arXiv:0709.0611v1

arXiv:0710.4153v2

arXiv:0806.0665v2

ILIAS WG1, March 2008

Published article on Holographic Noise

ILIAS WG1, March 2008

Contents of this presentation

- Attempt to explain: “What is holographic noise?”
- Craig’s predictions
- Points we (experimentalists) do not understand
- Comparison of Craig’s prediction with noise measured in GEO600
- How to go on from here …

ILIAS WG1, March 2008

Spacetime

- Space time is not continuous, but quantized.
- Assumption:smallest length is the Planck wavelength
- This gives a fundamental limit for measurements

ILIAS WG1, March 2008

Holographic principle

- Some recent findings suggest that all information of a 3D world can be encoded in a 2D surface at Planck resolution.
- Example: black hole theory suggest that the entropy scales proportional to its area (not its volume!)
- Hypothesis: Quantum geometry (spacetime) has only 2+1 dimesions.

ILIAS WG1, March 2008

Indeterminancy of transverse Positions

- Angles are indeterminate at Planck scale:
- Relative Transverse Positions are uncertain. Uncertainty increases at larger separation:

ILIAS WG1, March 2008

Characteristic of a random walk

Time series of a random walk

PSD of random walk time series

- The spectrum of a random walk is 1/f in ASD.

ILIAS WG1, March 2008

Contents of this presentation

- Attempt to explain: “What is holographic noise?”
- Craig’s predictions
- Points we (experimentalists) do not understand
- Comparison of Craig’s prediction with noise measured in GEO600
- How to go on from here …

ILIAS WG1, March 2008

Craigs Predictions from arXiv:0806.0665v2

- Zero-parameter estimates
- GEO600:
- LIGO:

f < 550Hz

f > 550Hz

f < 150Hz

f > 150Hz

ILIAS WG1, March 2008

Contents of this presentation

- Attempt to explain: “What is holographic noise?”
- Craig’s predictions
- Points we (experimentalists) do not understand
- Comparison of Craig’s prediction with noise measured in GEO600
- How to go on from here …

ILIAS WG1, March 2008

Points we (experimentalists) do not understand

Here should some brainstorming take place …

We could try to assemble a list of open issues we want to discuss with Craig…

For instance:

- Isn’t there any averaging (since we use large amounts of photons)?
- GEO-spectrum of Holo noise: The Signal-Recycling cavity does not really change the storage times of the light…

ILIAS WG1, March 2008

- Attempt to explain: “What is holographic noise?”
- Craig’s predictions
- Points we (experimentalists) do not understand
- Comparison of Craig’s prediction with noise measured in GEO600
- How to go on from here …

ILIAS WG1, March 2008

GEO’s Mystery noise

- For a long time we observe a unexplained noise component in GEO600.
- Shows up as a gap between the sum of all known noises (yellow) and the actual senstivity (black).

- Details available at:
- Mystery-noise-Wiki http://www.sr.bham.ac.uk/dokuwiki/doku.php?id=geonoise:home
- http://www.ego-gw.it/ILIAS-GW/WP1docs/hild_231007.ppt
- http://www.ego-gw.it/ILIAS-GW/WP1docs/hild1_050308.ppt

ILIAS WG1, March 2008

Noise projection including Holographic Noise

- Using Holographic noise prediction from arXiv:0806.0665v2

1.6e-22/sqrt(Hz) for f>550 Hz and 1/f below for f<550 Hz.

- If Holographic noise prediction is correct, it could explain most of the mystery noise.

... but ...

ILIAS WG1, March 2008

Please keep in mind:

- Eventhough we worked very hard to ensure the correctness of the projections, they might not represent the full truth:
- Projections only account for linear noise coupling
- Some projections might underestimate the actual noise contribution (frequency noise)
- Some noise sources might still be undiscovered
- Holographic noise is only one of several potential candidates that might be able to mystery noise…

ILIAS WG1, March 2008

Projection including increasedBS thermo refractive noise

- Using a BS thermo refactive noise 3.4 times higher than we believe it to be seems to explain the mystery noise as well.

ILIAS WG1, March 2008

- Attempt to explain: “What is holographic noise?”
- Craig’s predictions
- Points we (experimentalists) do not understand
- Comparison of Craig’s prediction with noise measured in GEO600
- How to go on from here …

ILIAS WG1, March 2008

How can we go on from here?

- The two main contributor to the GEO sensitivity are mystery noise and shot noise
- We can change the tuning of the Signal-Recycling mirror change the shape of the shot noise.

Shot noise in GEO600 for different SR detunings

ILIAS WG1, March 2008

Statistical analysis

- Need to do noise projections at several SR detunings.
- Derive shape of mystery noise for the different detunings.
- Use Baysian statistics to put a hard number on how well Craigs predictions explain the mystery noise and compare this to numbers how well a 1/f noise or a flat noise can reproduce the mystery noise.

Example of earlier

mystery noise mea-

surements or different

SR detunings

ILIAS WG1, March 2008

Holographic spacetime

- “Relative spacetime positions of events are indeterminate.”
- “Spacetime positions defined to the precision of information propagation and measurement allowed by the capacity of Planck wavelength radiation.”
- (Planck radiation: UV cutoff at Planck kength)

ILIAS WG1, March 2008

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