Letters of Intent received in 2019

LoI 2021-2061
Consensus Cosmic Shear in the 2020s

Date: 16 August 2021 to 27 August 2021
Location: BEXCO, Busan, Republic of Korea, Korea, Rep of
Contact: Nicolas Martinet (nicolas.martinet@lam.fr)
Coordinating division: Division J Galaxies and Cosmology
Other divisions:
Co-Chairs of SOC: Nicolas Martinet (Laboratoire d'Astrophysique de Marseille)
Angus Wright (Ruhr University Bochum)
Chair of LOC: Prof. Hyesung Kang (Pusan National University)



- Current weak lensing surveys
- Tensions in cosmology
- Weak-lensing systematics
- Redshift calibration
- Modelling extensions to LCDM
- Non-standard lensing probes
- Future weak-lensing analyses



Recent measurements of the Hubble constant and (to a lesser extent) of the density and clustering strength of matter, hint at the possibility that cosmological parameters estimated at high- and low-redshift are inconsistent. Such a finding could be a sign that the highly successful Lambda CDM standard model of cosmology does not fully describe the true nature of our Universe, or could simply be a reflection of unrecognised systematics within one or more of these analyses. As a result, recent studies of low redshift probes utilising, in particular, the gravitational lensing of large scale structures (i.e. cosmic shear) have been particularly focused on the exploration and mitigation of systematic effects. At the sensitivity of current surveys, the community’s understanding of cosmic shear systematics is largely acceptable. However with the immense statistical power of next generation cosmic shear surveys, it will soon become paramount for the community to understand these systematics with unprecedented accuracy; particularly before proposing extensions to the standard LCDM paradigm: i.e. via dark energy, modified gravity, massive neutrinos, etc. Moreover, with LSST's first light in 2020, and the launch of Euclid in 2022, the IAU General Assembly 2021 is an extremely timely opportunity to address these questions. The aim of this symposium is therefore to bring together experts from the ongoing and future lensing surveys, thereby fostering collaboration between traditionally competitive teams, in order to build a consensus regarding cosmic shear methodologies and identify the key systematics and cosmological models that will need to be tested in the 2020's.

With these goals in mind, we have compiled lists below that contain: planned topics to be covered at the symposium, possible SOC members, possible review talk speakers, and possible invited speakers. In all of our example selections, we put a strong focus on maintaining equity and diversity of speakers/members across gender, career, and geographical lines. For our SOC, we have compiled a list of (predominantly senior) members of the community who we feel will have a good insight into who is performing cutting edge research relevant to the symposium in each of their subjects and locations. The SOC maintains a high level of gender equity and geographical diversity, to ensure an unbiased selection of speakers. The SOC will compile a list of review speakers and standard invited talks, for which we have provided suggestions below. We have planned the symposium in a format whereby members of the community who may not be experts in all aspects of cosmic shear will still be able to engage with, and provide a valuable contribution to, every session. As such, the review speakers will be selected with two priorities in mind: expert knowledge of the subject contained within the session, and a high proficiency at delivering engaging and informative talks. Additional talks will be focused on early- and mid-career researchers, who will play a pivotal role in the success of these surveys. We provide a list of example invited speakers, who would give more specific detailed talks about difficulties faced in each subject area, and proposed solutions to these problems. Formatted in this way, we believe that the symposium will be a fantabulous addition to the 2021 IAU General Assembly in Busan.

Possible SOC (not contacted yet):
- Nicolas Martinet (co-chair, LAM, France)
- Angus Wright (co-chair, Ruhr University Bochum, Germany)
- Chris Blake (Swinburne University, Australia)
- Zuhui Fan (Peking University, China)
- Catherine Heymans (ROE, UK)
- Elisabeth Krause (Steward Observatory, USA)
- Clotilde Laigle (IAP, France)
- Alexie Leauthaud (Santa Cruz University, USA)
- Peter Schneider (AIfA, Bonn, Germany)
- Masahiro Takada (IPMU Tokyo, Japan)

Possible reviewers (not contacted yet):
- Current weak lensing surveys: Chihway Chang (Chicago, USA)
- Tensions in cosmology: Hendrik Hildebrandt (Ruhr University Bochum, Germany)
- Weak-lensing systematics: Rachel Mandelbaum (Carnegie, USA)
- Redshift calibration: Peter Capak (Caltech, USA)
- Modelling extensions to LCDM: Tamara Davis (Queensland University, Australia)
- Non-standard lensing probes: Tomasz Kacprzak (ETH Zurich, Switzerland)
- Future weak-lensing analyses: Henk Hoekstra (Leiden University, Netherlands)

Possible invited talks (not contacted yet):
- Current weak lensing surveys: Marika Asgari (ROE, UK), Michael Troxel (Columbus, USA), Chiaki Hikage (Kavli Tokyo, Japan)
- Tensions in cosmology: Sherry Suyu (MPIA Garching, Germany), James Bartlett (APC, France)
- Weak-lensing systematics: Tim Schrabback (Bonn, Germany)
- Reshift calibration: Romain Buchs (Stanford, USA)
- Modelling extensions to LCDM: Shahab Joudaki (Oxford, UK)
- Non-standard lensing probes: Carlo Giocoli (Bologna University, Italy), Eric Jullo (LAM, France)
- Future weak-lensing analyses: Xiangkun Liu (Peking University, China), Risa Wechsler (Stanford, USA)