[Physics-talks] This Wednesday! Special CECI Colloquium by Nobel Laureate Adam Riess

[hai-bo.yu at ucr.edu]

Dear All,

The speaker of our public cosmology lecture, Nobel Laureate Adam Riess,
will give a special CECI colloquium this Wednesday, June 3.

Title: The James Webb Space Telescope and the Distance Network: New
Paths to Understanding the Hubble Tension

Speaker: Adam Riess
Affiliation: Johns Hopkins University
Time: *Starting at 2pm, Wednesday, June 3, 2026*
Venue: *Seminar Room 1110, Multidisciplinary Research Building*

Abstract: One of the most basic questions in cosmology is: How fast is the
Universe expanding today? Two powerful approaches give answers that should
agree but do not. Measurements based on the cosmological model calibrated
by the cosmic microwave background predict one value for the Hubble
constant H0, while direct measurements using the cosmic distance ladder
give a higher value. The difference, now exceeding 5σ, is known as the
Hubble tension and has persisted for more than a decade and challenges
LambdaCDM.

The James Webb Space Telescope (JWST) provides a new way to test the local
distance ladder that underlies the direct measurement of H0. By observing
Cepheid variable stars and other distance indicators in galaxies that host
Type Ia supernovae, and that were previously studied with the Hubble Space
Telescope (HST), JWST allows a direct and independent check of those earlier
measurements at higher resolution. These observations are also part of
a broader effort to build a more robust local distance network, combining
multiple independently calibrated distance indicators across the Milky Way
and nearby galaxies. This network approach allows different rungs of the
distance ladder to cross-check one another and helps expose potential
systematic errors.

I will review several tests of possible systematics. The JWST observations
closely match the HST results across multiple methods and wavelengths,
ruling out several suspected sources of systematic error and strengthening
the case that the Hubble tension is real. In addition, the distance network
results
show that the tension does not depend on any single source, team, or
sample. Rather, it may signal that something important is missing from
our current picture of the Universe.

You are welcome to join us!

Haibo
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