# UMICH-2015: CMB-Lensing break-out session 2

From CMB-S4 wiki

## Delensing Details

Questions for discussion

- Experiment design
- Can we combine different experiments, and is it worth having two different noise levels on two experiments (high-res + low-res)

- Algorithms - Quadratic Estimator / Iterative / Sampling
- What is the best algorithm to use?
- How low ell do we use/need for reconstruction?

- Systematics and Delensing
- Dust foregrounds and sources - how do they propagate through the delensing procedure? How much do they matter?
- Instrumental systematics, higher order biases, LSS non-Gaussianity - any concerns for delensing?

- Analysis of Delensed Maps
- What are the statistical and noise properties of the delensed maps? How to construct likelihoods?

## CMB Lensing Cross-correlations

Questions for discussion:

- weak lensing calibration: cross-correlations with LSST / Euclid / ... weak lensing
- how precise are the correlations?
- is this level of multiplicative bias calibration interesting?
- are intrinsic alignments a limiting factor?

- clustering from correlations with DESI/Euclid/LSST galaxies / quasars / ...
- how well can biases be modeled and constrained?
- can these observables be used cleanly and powerful enough to detect neutrino mass?
- what are the key science drivers in extragalactic astrophysics?

- other surveys
- would overlap with external datasets gain from a northern site?
- is there a way to make use of cross-correlations with Ly-alpha or intensity mapping, or are the modes they probe too different?
- prospects and challenges for cluster mass calibration with CMB lensing?