1. TR33 in the Light of the US- Dark Energy Task Force Report Thomas Reiprich Danny Hudson Oxana Nenestyan Holger Israel Emmy Noether Research Group Argelander-Institut für Astronomie Universität Bonn http://www.dark-energy.net

2. US-Dark Energy Task Force (DETF) Established to advise DoE, NASA, and NSF on future of dark energy research. Members: Kolb, Albrecht, Bernstein, Cahn, Freedman, Hewitt, Hu, Huth, Kamionkowski, Knox, Mather, Staggs, Suntzeff. US - why care? Useful calculations, trendsetter.

3. Introductory Remarks DE one of most important problems in all physical sciences. Most critical component of any approach to DE problem is improvement in experimental constraints. Clear steps can be taken to drive significant progress.

4. Four Main Techniques Baryon Acoustic Oscillations (BAO; new, less affected by astrophysical uncertainties but least statistical power). Galaxy Cluster (CL) surveys (MF, statistical power to exceed BAO and SN but currently largest systematic uncertainties). Supernova (SN) surveys (at present most powerful). Weak Lensing (WL) surveys (new, if systematics under control as currently predicted then most powerful technique ). No primary CMB. GRBs and GW unclear.

5. Four Stages I: Known today. II: Known after completion of ongoing projects. III: Currently proposed near term projects. IV: LST, SKA, JDEM.

6. Recommendations Multiple techniques at every stage, at least one sensitive to growth of structure. Stage III projects should achieve factor 3 gain over stage II projects. Stage IV factor 10. High priority for near term funding for studies of systematic efffects.

7. Goals, Figure of Merit Accelerated expansion due to cosmological constant? If not, constrain w(a) (= w 0 +(1-a)w a ). Check for inconsistency between w(a) from cosmic expansion and growth of structure (i.e., possible failure of general relativity). Figure of merit: 1/area of 95% error ellipse in w 0 /w a plane.

8. Direct Relation to TR33 All observational methods included! –BAO: B8 –CL: B4, B6, B7 (optical, SZ, X-ray, lensing) –SN: B3 –WL: B5

9. Direct Relation to TR33 “Our inability to forecast systematic error levels reliably is the biggest impediment to judging the future capabilities of the techniques.” => Use results with care. => Test systematics.

10. Direct Relation to TR33 TR includes (almost?) all mentioned primary tests for systematics for all techniques: –BAO: better theoretical understanding of non- linear regime and bias (B8, C1). –CL: observational constraints from lensing, SZ, and X-rays on observable-mass relation (B6, B7). –SN: detailed observations of nearby SN to study dependence of peak luminosities (and spectra) on observational parameters (B3). –WL: observational calibration of photo-z technique (also for BAO) and study feasibility of corrections for intrinsic galaxy shapes and PSF (~B5, B8?).

11. Direct Relation to TR33 Involvement in –JDEM? –LST? –SKA?