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國立清華大學天文研究所 NTHU Institute of Astronomy
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2017-05-05 Excessive shift of the CMB acoustic peaks of the Cold Spot area

Time Coordinate: 3:30 pm 5th May 2017 (Friday)

Space Coordinate: NTHU General Building II, R521

Speaker: Dr. Lung-Yih Chiang (ASIAA)

Title: Excessive shift of the CMB acoustic peaks of the Cold Spot area


Measurement of the acoustic peak positions of the cosmic microwave background (CMB) temperature anisotropies has been instrumental in deciding the geometry and content of the universe. Acoustic peak positions vary from patch to patch in different parts of the sky due to statistical fluctuation. We present the statistics of the peak positions of small patches from ESA Planck data. It is found that the peak positions have significantly high variance compared to the 100 CMB simulations with best-fit LambdaCDM model with lensing and Doppler boosting effects included, both of which can significantly shift the peaks of small patches. 

Examining individual patches, we find the one containing the mysterious "Cold Spot", an area near the Eridanus constellation where the temperature is lower than Gaussian theory predicts, displays large synchronous shift of peak positions towards smaller multipole numbers (i.e. larger scales) with significance lower than 1.11 x 10^{-4}. The combination of large synchronous shifts in acoustic peaks and lower than usual temperature at the Cold Spot area results in a 4.73 sigma detection (significance p~1.11 x 10^{-6}) against the LambdaCDM model, prompting us to propose one of the possible accounts for both anomalies: some localised unknown force to stretch the space around the Cold Spot area so that the acoustic peak positions are shifted towards large scales and the temperature is dragged down.