Chris Orban (OSU Physics) with David Weinberg (OSU Astronomy)

1. Self-similar Bumps and Wiggles: Isolating the Evolution of the BAO Peak with Power-law Initial Conditions Chris Orban (OSU Physics) with David Weinberg (OSU Astronomy) Clustering Time Scale

2. Background Early Universe Late Universe Eisenstein et al. 2005 credit: SDSS credit: WMAP Problem: How does the BAO signature change over cosmic time? How “standard” is this standard ruler? Opportunity: Largest “ruler” ever discovered – very useful for distance scale, dark energy Anchored to CMB (not LMC!) Challenge: Need to observe large cosmological volumes! Need sub-percent accurate theory for any w(z)!

3. Strongly non-linear regime Clustering Time Linear regime Scale Initial Conditions Fourier Transform Clustering Scale Scale-1 Chris Orban – Self-similar Bumps and Wiggles

4. Non-linear structure formation Chris Orban – Self-similar Bumps and Wiggles

5. Simplifying the Problem Chris Orban – Self-similar Bumps and Wiggles

6. rbao / Lbox = 1 / 20 Self-similar Bumps! !!! rbao / Lbox = 1 / 10 • Comparing results from rbao x2 simulations (e.g. rbao = 200 h-1Mpc) to previous results !!! • Because of self-similarity the bump evolution should be exactly the same as a scaling of the previous results • Can’t do this with CDM initial conditions! • Numerical effects may break self-similarity – a test more powerful and more general than convergence testing rbao / np1/3 = 100/8

8. Fourier-space phenomenology Non-linear spectrum Small-scale model Damping PNL(k) = exp(-2k2/2) PL(k/) + A(k) Initial spectrum shift!

9. Beyond linear-order • Many groups developing beyond-linear-order perturbation theory methods to describe BAO evolution • If successful BAO evolution for arbitrary w(z) can be computed without N-body simulations • Powerlaw setup is problematic for many of these methods – may point to better schemes PT breaks down PT valid 1-loop SPT predictions! 1-loop SPT predictions from publically-available code: http://mwhite.berkeley.edu/Copter/ (Carlson, White, & Padmanabhan 2009) Chris Orban – Self-similar Bumps and Wiggles

10. Future Plans • Run “powerlaw” setup with   0 • Explore the broadening of the BAO feature in the halo clustering • Run simulations with a different N-body code (PKDGRAV instead of Gadget2) • Compare and develop phenomenological models to describe non-linear evolution Chris Orban – Self-similar Bumps and Wiggles