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Stefan Hild for the GEO600 team 16th ILIAS WG1 meeting, July 2008, Birmingham Holographic Noise in GEO600?

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Stefan HildILIAS WG1, March 2008Slide 2 Articles on Holographic Noise available on arXiv: arXiv: v2 arXiv: v2 arXiv: v1 arXiv: v2 arXiv:astro-ph/ v4

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Stefan HildILIAS WG1, March 2008Slide 3 Published article on Holographic Noise

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Stefan HildILIAS WG1, March 2008Slide 4 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 …

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Stefan HildILIAS WG1, March 2008Slide 5 Spacetime Space time is not continuous, but quantized. Assumption:smallest length is the Planck wavelength This gives a fundamental limit for measurements

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Stefan HildILIAS WG1, March 2008Slide 6 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.

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Stefan HildILIAS WG1, March 2008Slide 7 Indeterminancy of transverse Positions Angles are indeterminate at Planck scale: Relative Transverse Positions are uncertain. Uncertainty increases at larger separation:

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Stefan HildILIAS WG1, March 2008Slide 8 Holographic shear noise PRD 77,

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Stefan HildILIAS WG1, March 2008Slide 9 Characteristic of a random walk The spectrum of a random walk is 1/f in ASD. Time series of a random walkPSD of random walk time series

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Stefan HildILIAS WG1, March 2008Slide 10 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 …

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Stefan HildILIAS WG1, March 2008Slide 11 Craigs Predictions from arXiv: v2 Zero-parameter estimates GEO600: LIGO: f < 550Hz f > 550Hz f > 150Hz f < 150Hz

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Stefan HildILIAS WG1, March 2008Slide 12 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 …

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Stefan HildILIAS WG1, March 2008Slide 13 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…

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Stefan HildILIAS WG1, March 2008Slide 14 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 …

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Stefan HildILIAS WG1, March 2008Slide 15 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

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Stefan HildILIAS WG1, March 2008Slide 16 Noise projection including Holographic Noise Using Holographic noise prediction from arXiv: v2 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.

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Stefan HildILIAS WG1, March 2008Slide 17 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…

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Stefan HildILIAS WG1, March 2008Slide 18 Projection including increased BS 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.

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Stefan HildILIAS WG1, March 2008Slide 19 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 …

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Stefan HildILIAS WG1, March 2008Slide 20 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

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Stefan HildILIAS WG1, March 2008Slide 21 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

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Stefan HildILIAS WG1, March 2008Slide 22 EXTRA SLIDES

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Stefan HildILIAS WG1, March 2008Slide 23 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)

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Stefan HildILIAS WG1, March 2008Slide 24 L-shape versus triangle arXiv: v2

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