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 Scale Time

Background Early Universe Late Universe credit: SDSS credit: WMAP Eisenstein et al 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)!

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

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

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

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

Fourier-space phenomenology P NL (k) = exp(-  2 k 2 /2) P L (k/  ) + A(k) Damping Non-linear spectrum Small-scale model Initial spectrum shift!

Beyond linear-order 1-loop SPT predictions! PT valid PT breaks down 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 Chris Orban – Self-similar Bumps and Wiggles 1-loop SPT predictions from publically-available code: (Carlson, White, & Padmanabhan 2009)

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