Oliver Friedrich

    Fraunhofer-Schwarzschild Fellow

    University Observatory Munich

cosmologist working to find

  a point to stand on

I am fascinated by the classical, quantum and Bayesian probability distributions that govern cosmology and cosmic physics. My research aims to understand these three regimes of probability theory in cosmology and their sometimes unexpected connections.

My scientific activities - and the publications resulting from them - can be sorted into the following groups:

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Quantum first:

concrete models of cosmic physics that implement features of quantum gravity

Selected publications:

• Friedrich, Giesel, Kushwaha (2026)
  Area Scaling of Dynamical Degrees of Freedom in Regularised Scalar Field Theory
  arXiv:2602.09100
  NOTE: since 2026 my theoretical papers come with alphabetical author lists; this project was lead by my student Varun Kushwaha who is corresponding author of the paper
• Friedrich, Cao, Carroll, Cheng, Singh (2024)
  Holographic phenomenology via overlapping degrees of freedom
  arXiv:2402.11016   Class. & Quant. Gravity
• Singh, Friedrich (2023)
  Emergence of Gravitational Potential and Time Dilation from Non-interacting Systems Coupled to a Global Quantum Clock
  arXiv:2304.01263   Foundations of Physics
• Friedrich, Singh, Doré (2022)
  Toolkit for Scalar Fields in Universes with finite-dimensional Hilbert Space
  arXiv:2201.08405   Class. & Quant. Gravity

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Probability distribution functions

of cosmic density fields

Selected publications:

• Friedrich, Castiblanco, Halder, Uhlemann (2025)
  Bye binormal: analysing the joint PDF of galaxy density and weak lensing convergence
  arXiv:2507.16957   MNRAS
• Uhlemann, Friedrich et al. (2022)
  It takes two to know one: Computing accurate one-point PDF covariances from effective two-point PDF models
  arXiv:2210.07819   OJA
• Friedrich et al. (2022)
  The PDF perspective on the tracer-matter connection: Lagrangian bias and non-Poissonian shot noise
  arXiv:2107.02300   MNRAS
• Burger, Friedrich, Harnois-Déraps, Schneider et al. (2022)
  KiDS-1000 Cosmology: Constraints from density split statistics
  arXiv:2208.02171   A&A
• Halder, Friedrich, Seitz, Varga (2021)
  The integrated 3-point correlation function of cosmic shear
  arXiv:2102.10177   MNRAS
• Burger, Friedrich, Harnois-Déraps, Schneider (2021)
  A revised density split statistic model for general filters
  arXiv:2106.13214   A&A
• Friedrich et al. (2020)
  Primordial non-Gaussianity without tails -- how to measure fNL with the bulk of the density PDF
  arXiv:1912.06621   MNRAS
• Uhlemann, Friedrich et al. (2020)
  Fisher for complements: Extracting cosmology and neutrino mass from the counts-in-cells PDF
  arXiv:1911.11158   MNRAS
• Gruen, Friedrich et al. (2018)
  Density split statistics: Cosmological constraints from counts and lensing in cells in DES Y1 and SDSS data
  arXiv:1710.05045   Physical Review D
• Friedrich et al. (2018)
  Density split statistics: joint model of counts and lensing in cells
  arXiv:1710.05162   Physical Review D
• Gruen, Friedrich et al. (2016)
  Weak lensing by galaxy troughs in DES Science Verification data
  arXiv:1507.05090   MNRAS

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How certain is cosmological information?

Selected publications:

• Homer, Friedrich, Gruen (2025)
  Simulation-based inference has its own Dodelson-Schneider effect (but it knows that it does)
  arXiv:2412.02311   A&A
• Percival, Friedrich, Sellentin, Heavens (2022)
  Matching Bayesian and frequentist coverage probabilities when using an approximate data covariance matrix
  arXiv:2108.10402   MNRAS
• Friedrich et al. (2021)
  Dark Energy Survey year 3 results: covariance modelling and its impact on parameter estimation and quality of fit
  arXiv:2012.08568   MNRAS
• Friedrich & Eifler (2018)
  Precision matrix expansion - efficient use of numerical simulations in estimating errors on cosmological parameters
  arXiv:1703.07786   MNRAS
• Friedrich et al. (2016)
  Performance of internal covariance estimators for cosmic shear correlation functions
  arXiv:1508.00895   MNRAS