EE Student Information

The Department of Electrical Engineering supports Black Lives Matter. Read more.

• • • • •

EE Student Information, Spring Quarter through Academic Year 2020-2021: FAQs and Updated EE Course List.

Updates will be posted on this page, as well as emailed to the EE student mail list.

Please see Stanford University Health Alerts for course and travel updates.

As always, use your best judgement and consider your own and others' well-being at all times.

Applied Physics/Physics Colloquium presents "Tension between early and late universe measurements of H0: Hint of new physics?”

Tension between early and late universe measurements of H0: Hint of new physics?
Tuesday, October 29, 2019 - 4:30pm
Hewlett 200
Tommaso Treu (UCLA)
Abstract / Description: 

In the past few years, a tension has emerged between the current expansion rate of the universe (H0) and the value predicted by early universe probes under the assumption of a standard LCDM cosmology. The tension is statistically significant: combinations of local probes are 4-6 sigma away from H0 as inferred by Planck, for example. Efforts to uncover systematic uncertainties are under way, but they have been unsuccessful so far. If the tension is real, most proposals to resolve it require changing the expansion history before recombination in a non-trivial way, possibly as a result of early dark energy, or sterile neutrinos. I will review measurements of H0, including the results of the well known methods based on the local distance ladder and on the cosmic microwave background. I will explain in detail the approach based on gravitational time delays, that have recently reached comparable precision, providing an independent verification of the tension. I will conclude by discussing the prospects of reaching sub-percent precision on multiple independent methods as a way to control systematics, and verify whether indeed this is the first hint of new physics beyond LCDM.

Aut. Qtr. Colloq. committee: R. Blandford (Chair), B. Feldman, A. Kapitulnik, B. Lev and V. Khemani

Location: Hewlett Teaching Center, Rm. 200