Zachary Slepian: Bio

Curriculum Vitae 

Publications List

My work is in cosmology on a range of topics from theoretical to methodological and observational. At Harvard, my primary focus has been assessing whether there is a systematic offset in the Baryon Acoustic Oscillation standard ruler due to an imprint of baryon-dark matter relative velocities on galaxy clustering today. I have computed the relative velocity effect on the 2 and 3-point galaxy correlation functions and developed a novel, ultra-fast algorithm for measuring the 3-point correlation function, with a Fourier version suitable for upcoming large-scale structure surveys such as Euclid, LSST, and DESI.

I have applied the 3-point algorithm to the SDSS DR12 CMASS sample of ~800,000 Luminous Red Galaxies, making the largest-ever measurement of the 3-point function in both galaxy number and maximum physical scale. This measurement was reported both in a compressed basis where one triangle side is integrated out and in the full 3-D parameter space. The latter enabled the first high-significance detection of the BAO in the 3PCF (4.5sigma) and a 1.7% precision measurement of the cosmic distance scale from the 3PCF alone. We also placed a 0.5% precision constraint on the baryon-dark matter relative velocity’s coupling to the BOSS Luminous Red Galaxies, meaning any shift in the BAO scale in this survey is 0.3% or smaller.

In analytic work supporting these observational constraints, I developed a configuration-space model for the 3PCF including redshift space distortions, the analog of the Kaiser/Hamilton formulae for the 2PCF.  I have also developed an algorithm to use Fourier transforms to evaluate a pairwise defined line of sight for measurements of the anisotropic 2-point correlation function. Another work involved building a simple analytic model for the linear growth of structure showing how the BAO scale emerges in the matter transfer function.  

My previous work has concentrated on physically-motivated parametrizations for the dark energy equation of state (with JR Gott) and on testing thermalized bosonic dark matter against observational constraints (with Jeremy Goodman).

I received my BA from Princeton in 2011, a master's in philosophy of physics from Oxford in 2012, and my PhD from Harvard in 2016 working with Daniel J. Eisenstein.