NITheP cordially invites you to a seminar by:

Simone Aiola

University of Pittsburgh

Date: Tuesday, 14th October 2014 Time: 14h00 – 15h00

Venue: NITheP Seminar Room, H-Block, 3rd Floor

TITLE: Extreme-Value Statistics for Testing Dark Energy

ABSTRACT:
The accelerated expansion of the universe leaves an imprint in the cosmic microwave background (CMB) temperature fluctuations on large angular scales, known as the late-time integrated Sachs-Wolfe effect (ISW). A detection of this signal has been claimed at 4.4-sigma significance by stacking temperature patches aligned with superstructures identified in the Sloan Digital Sky Survey. Recently, several authors have argued that this strong detection is in tension with the standard Lambda-CDM model at more than a 3-sigma level. I will present estimates of the expected signal by
computing extreme-value statistics on Gaussian random realizations of the microwave sky temperature fluctuations. Such simulations are realistic representations of the CMB sky, which account for the correlations between various temperature components. In addition, they are simpler and more efficient to construct than large-scale structure simulations. I will compare such theoretical estimates with a reanalysis of the CMB data, using WMAP and Planck full-sky maps. Finally, I will also discuss prospects for using the weak gravitational lensing of the CMB as tracer of ISW peaks, and the possibility of constraining properties of dark energy using this extreme-value statistics.

Coffee and biscuits will be served after the talk