Phil Bull

Phil Bull

Lecturer in Cosmology at QMUL

I'm a theoretical cosmologist interested in mapping the large-scale structure of the Universe with radio and optical telescopes

Me, staring off into middle distance. Credit: Kiran Joshi. HERA array, with PAPER (foreground) and MeerKAT (background). Credit: Kathryn Rosie (2018).
MeerKAT dishes seen from above. Credit: SKA Africa (2016). LSST at sunset. Credit: Gianluca Lombardi (2018).

About Me.

I'm a lecturer in cosmology at Queen Mary University of London. Before that, I was a postdoc in the Radio Astronomy Lab and BCCP at UC Berkeley from 2017 - 2018, a NASA Postdoctoral Program fellow at JPL/Caltech from 2015 - 2017, and a postdoc in theoretical astrophysics at the University of Oslo from 2013 - 2015. I did my DPhil (PhD) in Astrophysics at the University of Oxford from 2010 - 2013, and my undergraduate degree in Physics with Astrophysics at the University of Manchester from 2006 - 2010. I'm originally from Stoke-on-Trent in the UK.

I'm also a Visiting Senior Researcher at the Centre for Radio Cosmology at the University of the Western Cape, a member of the SKA Cosmology Science Working Group (Core Team) and the HERA collaboration (Executive Board and lead of the Stats working group), a Full Member of the LSST Dark Energy Science Collaboration (where I was formerly co-convener of the Theory and Joint Probes working group), a member of the MeerKLASS radio cosmology collaboration, and was previously a member of the Planck Collaboration as part of the LFI Core Team while in Oslo. I am also a member of the Institute of Applied Data Science at Queen Mary.

Aside from my research interests in theoretical cosmology, I've also been involved in the open source movement. I began contributing to Ubuntu around 2005, before moving on to work on documentation for the GNOME project. My roles have included coordinating the writing of user and developer documentation, training new contributors, and supervising students for the project's Women's Outreach Program. I've also co-authored a couple of books on Ubuntu, published by No Starch Press in 2010 and 2012.

HERA logo LSST DESC logo SKA logo CRC logo


My area of expertise is in theoretical cosmology and general relativity. I'm fascinated by the lumpy, inhomogeneous nature of the Universe that we live in, and how structures evolve and interact on large scales. One of the biggest puzzles in this area is the (relatively) recent finding that the expansion of the Universe appears to be accelerating. This is a very curious result, and I'd like to get to the bottom of it!

Research interests

My technical interests are quite broad, and include:


This is a list of my scientific publications to date. You can also find listings on SPIRES, Google Scholar, and arXiv. My ORCID is 0000-0001-5668-3101. Some of the computer code used in these papers is available online.

Published and submitted papers are listed below, or you can skip to the list of conference proceedings.

  1. Observing relativistic features in large-scale structure surveys -- I: Multipoles of the power spectrum
    C. Guandalin, J. Adamek, P. Bull, C. Clarkson, L.R. Abramo, L. Coates
  2. Searching for dark energy in the matter-dominated era
    P. Bull, M. White, A. Slosar
  3. DAYENU: A Simple Filter of Smooth Foregrounds for Intensity Mapping Power Spectra
    A. Ewall-Wice et al.
  4. Redundant-Baseline Calibration of the Hydrogen Epoch of Reionization Array
    J.S. Dillon et al.
  5. Absolute Calibration for the Hydrogen Epoch of Reionization Array and Its Impact on the 21 cm Power Spectrum
    HERA Collaboration (N.S. Kern et al.)
    ApJ 890, 122 (2020); arXiv:1910.12943
  6. Mitigating Internal Instrument Coupling II: A Method Demonstration with the Hydrogen Epoch of Reionization Array
    HERA Collaboration (N.S. Kern et al.)
    ApJ 888, 70 (2020); arXiv:1909.11733
  7. Electrical and electromagnetic co-simulations of the HERA Phase I receiver system
    HERA Collaboration (N. Fagnoni et al.)
  8. Modified Gravity and Dark Energy models Beyond w(z)CDM Testable by LSST
    LSST Dark Energy Science Collaboration (M. Ishak, T. Baker, P. Bull et al.)
  9. The HERA-19 Commissioning Array: Direction-dependent Effects
    HERA Collaboration (S. Kohn et al.)
    ApJ 882, 58 (2019); arXiv:1802.04151
  10. Core Cosmology Library: Precision Cosmological Predictions for LSST
    LSST Dark Energy Science Collaboration (incl. P. Bull)
    ApJS 242, 2 (2019); arXiv:1812.05995
  11. Cosmology with Phase 1 of the Square Kilometre Array; Red Book 2018: Technical specifications and performance forecasts
    Square Kilometre Array Cosmology Science Working Group (incl. P. Bull)
    PASA 37, E007; arXiv:1811.02743
  12. Testing General Relativity with the Doppler magnification effect
    S. Andrianomena, C. Bonvin, D. Bacon, P. Bull, C. Clarkson, R. Maartens, T. Moloi
    MNRAS 488, 3759 (2019); arXiv:1810.12793
  13. Inflation and Early Dark Energy with a Stage II Hydrogen Intensity Mapping experiment
    Cosmic Visions 21 cm Collaboration (incl. P. Bull)
  14. Fundamental Physics with the Square Kilometre Array
    A. Weltman, P. Bull, S. Camera et al.
    PASA 37, E002 (2020); arXiv:1810.02680
  15. Weak gravitational lensing with CO galaxies
    P. Bull, I. Harrison, E. Huff
    ASP Conf. Ser. 517 (2018) 803; arXiv:1806.08339
  16. Model-independent curvature determination with 21cm intensity mapping experiments
    A. Witzemann, P. Bull, C. Clarkson, M. G. Santos, M. Spinelli, A. Weltman
    MNRAS 477, 1 (2018); arXiv:1711.02179
  17. Line-Intensity Mapping: 2017 Status Report
    E. Kovetz et al.
  18. Mitigating complex dust foregrounds in future CMB polarization experiments
    B. Hensley, P. Bull
    ApJ 853, 127 (2018); arXiv:1709.07897
  19. MeerKLASS: MeerKAT Large Area Synoptic Survey
    Mario G. Santos (Ed.) et al.
  20. Priors on the effective Dark Energy equation of state in scalar-tensor theories
    Marco Raveri, Philip Bull, Alessandra Silvestri, Levon Pogosian
    Phys. Rev. D 96, 083509 (2017); arXiv:1703.05297
  21. A Galaxy-Halo Model for Multiple Cosmological Tracers
    Philip Bull
    MNRAS 471, 12 (2017); arXiv:1610.08948
  22. Dipolar modulation in the size of galaxies: The effect of Doppler magnification
    Camille Bonvin, Sambatra Andrianomena, David Bacon, Chris Clarkson, Roy Maartens, Teboho Moloi, Philip Bull
    MNRAS 472, 4 (2017); arXiv:1610.05946
  23. Science Impacts of the SPHEREx All-Sky Optical to Near-Infrared Spectral Survey
    Olivier Doré, Michael W. Werner (Eds.) et al.
  24. Spatial curvature endgame: Reaching the limit of curvature determination
    C. Danielle Leonard, Philip Bull, Rupert Allison
    Phys. Rev. D 94, 023502 (2016); arXiv:1604.01410
  25. Reconstructing cosmic growth with kSZ observations in the era of Stage IV experiments
    David Alonso, Thibaut Louis, Philip Bull, Pedro G. Ferreira
    Phys. Rev. D 94, 043522 (2016); arXiv:1604.01382
  26. Distinguishing screening mechanisms with environment-dependent velocity statistics
    Magnus Fagernes Ivarsen, Philip Bull, Claudio Llinares, David Mota
    Astron. Astrophys. 595 (2016) A40; arXiv:1603.03072
  27. Beyond ΛCDM: Problems, solutions, and the road ahead
    Philip Bull, Yashar Akrami (Eds.) et al.
    Phys. Dark. Univ. 12, 56 (2016); arXiv:1512.05356
  28. Extending cosmological tests of General Relativity with the Square Kilometre Array
    Philip Bull
    Astrophys. J 817 (2016) 26; arXiv:1509.07562
  29. Weighing neutrinos with cosmic neutral hydrogen
    Francisco Villaescusa-Navarro, Philip Bull, and Matteo Viel
    Astrophys. J 814 (2015) 146; arXiv:1507.05102
  30. A systematic study of Lyman-Alpha transfer through outflowing shells: Model parameter estimation
    Max Gronke, Philip Bull, and Mark Dijkstra
    Astrophys. J 812 (2015) 123; arXiv:1506.03836
  31. Observational signatures of modified gravity on ultra-large scales
    Tessa Baker and Philip Bull
    Astrophys. J 811 (2015) 2, 116; arXiv:1506.00641
  32. Ultra-large scale cosmology with next-generation experiments
    David Alonso, Philip Bull, Pedro G. Ferreira, Roy Maartens, and Mario G. Santos
    Astrophys. J 814 (2015) 145; arXiv:1505.07596
  33. Cosmological performance of SKA HI galaxy surveys
    Sahba Yahya, Philip Bull, Mario G. Santos, Marta Silva, Roy Maartens, Patrice Okouma, and Bruce Bassett
    MNRAS 450, 2251 (2015); arXiv:1412.4700
  34. Cross-correlating 21cm intensity maps with Lyman Break Galaxies in the post-reionization era
    Francisco Villaescusa-Navarro, Matteo Viel, David Alonso, Kanan K. Datta, Philip Bull, and Mario G. Santos
    JCAP 1503 (2015) 03, 034; arXiv:1410.7393
  35. A CMB Gibbs sampler for localized secondary anisotropies
    Philip Bull, Ingunn K. Wehus, Hans Kristian Eriksen, Pedro G. Ferreira, Unni Fuskeland, Krzysztof M. Gorski, and Jeffrey B. Jewell
    ApJS 219, 10 (2015); arXiv:1410.2544
  36. Blind foreground subtraction for intensity mapping experiments
    David Alonso, Philip Bull, Pedro G. Ferreira, and Mario G. Santos.
    MNRAS 447, 400 (2015); arXiv:1409.8667
  37. Quintessence in a quandary: On prior dependence in dark energy models
    David J. E. Marsh, Philip Bull, Pedro G. Ferreira, and Andrew Pontzen
    Phys. Rev. D 90 (2014) 10, 105023; arXiv:1406.2301
  38. Late-time cosmology with 21cm intensity mapping experiments
    Philip Bull, Pedro G. Ferreira, Prina Patel, and Mario Santos
    Astrophys. J. 803 (2015) 1, 21; arXiv:1405.1452
  39. A multi-level solver for Gaussian constrained CMB realizations
    D. S. Seljebotn, K. A. Mardal, J. B. Jewell, H. K. Eriksen, and P. Bull
    ApJS 210, 24 (2014); arXiv:1308.5299
  40. What if Planck's Universe isn't flat?
    Philip Bull and Marc Kamionkowski
    Phys. Rev. D 87, 081301(R) (2013); arXiv:1302.1617
  41. Local and non-local measures of acceleration in cosmology
    Philip Bull and Timothy Clifton
    Phys. Rev. D 85, 103512 (2012); arXiv:1203.4479
  42. The isotropic blackbody CMB as evidence for a homogeneous universe
    Timothy Clifton, Chris Clarkson and Philip Bull
    Phys. Rev. Lett. 109, 051303 (2012); arXiv:1111.3794
  43. The kSZ effect as a test of general radial inhomogeneity in LTB cosmology
    Philip Bull, Timothy Clifton and Pedro G. Ferreira
    Phys. Rev. D 85, 024002 (2012); arXiv:1108.2222

Conference Proceedings

This is a list of my conference proceedings.

  1. Cosmology from HI galaxy surveys with the SKA
    Filipe Batoni Abdalla, Philip Bull, Stefano Camera, Aurelien Benoit-Levy et al.
    PoS AASKA14 (2015) 017; arXiv:1501.04035
  2. Cosmology from a SKA HI intensity mapping survey
    Mario Santos, Philip Bull, David Alonso et al.
    PoS AASKA14 (2015) 019; arXiv:1501.03989
  3. Cross correlation surveys with the Square Kilometre Array
    Donnacha Kirk, Filipe Batoni Abdalla, Aurelien Benoit-Levy, Philip Bull, and Benjamin Joachimi
    PoS AASKA14 (2015) 020; arXiv:1501.03848
  4. HI galaxy simulations for the SKA: number counts and bias
    Mario Santos, David Alonso, Philip Bull, Marta Silva, and Sahba Yahya
    PoS AASKA14 (2015) 021; arXiv:1501.03990
  5. Measuring baryon acoustic oscillations with future SKA surveys
    Philip Bull, Stefano Camera, Alvise Raccanelli, Chris Blake, Pedro Ferreira, Mario Santos, and Dominik J. Schwarz
    PoS AASKA14 (2015) 024; arXiv:1501.04088
  6. Cosmology on the Largest Scales with the SKA
    Stefano Camera, Alvise Raccanelli, Philip Bull, Daniele Bertacca et al.
    PoS AASKA14 (2015) 025; arXiv:1501.03851
  7. Measuring redshift-space distortion with future SKA surveys
    Alvise Raccanelli, Philip Bull, Stefano Camera, Chris Blake et al.
    PoS AASKA14 (2015) 031; arXiv:1501.03821
  8. Foreground Subtraction in Intensity Mapping with the SKA
    Laura Wolz, Filipe B. Abdalla, David Alonso, Chris Blake, Philip Bull et al.
    PoS AASKA14 (2015) 035; arXiv:1501.03823
  9. Synergy between the Large Synoptic Survey Telescope and the Square Kilometre Array
    David Bacon, Sarah Bridle, Filipe B. Abdalla, Michael Brown, Philip Bull et al.
    PoS AASKA14 (2015) 145; arXiv:1501.03977
  10. Euclid & SKA Synergies
    Thomas Kitching, David Bacon, Michael Brown, Philip Bull et al.
    PoS AASKA14 (2015) 146; arXiv:1501.03978


I try to make all of my scientific code, or at least a substantial fraction of it, publicly available. This enables other people to reproduce and check my work if they want to. It also allows them to build off my code and do cool new things, rather than having to spend months solving problems that I may have already solved. That's the theory, anyway. Much of the code is written in Python, C++, and/or Fortran 90, and housed on GitHub or Gitlab.

Here are some of my publicly-available scientific codes:

Research Group.

My research group currently consists of myself, Dr Samir Choudhuri, Dr Hugh Garsden, Dr Mel Irfan (at UWC), and PhD student Fraser Kennedy, plus Masters students Tim Oates, Alex Reedy, and Kabelo Malapane (at UWC). Our main focus is on performing the HERA power spectrum analysis and MeerKAT 21cm calibration, but we also work on other topics in 21cm cosmology, cosmological galaxy surveys, and statistical data analysis.

Phil, Samir, and Fraser in front of one of the HERA test dishes at Lord's Bridge, near Cambridge.

I may be able to recruit another PhD student to start in the 2021/22 academic year, either through an STFC studentship or a QMUL College studentship. The project I'm mostly looking to find someone for is called Unveiling the Cosmic Dawn and the Epoch of Reionisation with HERA. If you're interested, please apply through the normal QMUL Astronomy Unit route (see here for instructions; deadline 31st January 2021, but international students with external funding can apply later). And don't hesitate to get in touch with me if you have questions or want to discuss what's involved.


I'm currently teaching SPA6311 Physical Cosmology (3rd year) and SPA5201 Physics Laboratory (2nd year). I also supervise projects for SPA6776 (Extended Independent Project) and SPA6913 (Physics Review Project), both in the 3rd year.

I'm also directing a new BSc and MSci programme in Physics with Data Science at QMUL, launching in 2021.

Slides on Cosmology with SKA and Pathfinders from the 2016 INAF Scuola Lucchin summer school [20MB].

Slides on Gibbs sampling and Gaussian constrained realisations [7MB].

Research students

Summer research students


I've been involved in public outreach since the very start of my scientific career. Science is an extremely important part of the shared culture of humanity, and I believe that professional scientists have a duty to put their work into the public commons in an effective way, so that everyone can share in our discoveries.

I am not a cosmetologist.

I was the graduate public outreach coordinator at Oxford Astrophysics while I was a DPhil student there. We used to run open evenings for schools and the general public, using the Philip Wetton telescope on the roof of the Denys Wilkinson Building, and various cool Zooniverse projects.

We also initiated a rather successful annual space science festival called Stargazing Oxford, to tie in with the BBC's Stargazing Live programmes.

I've also been interviewed a few times here and there, and occasionally comment on science news stories in the press.

The pinnacle of my media career, however, was when I appeared (for approximately one second) in the 2013 feature documentary Hawking. You can find me at around 40 minutes in, eating soup and waving my hands.


Please feel free to contact me about any aspect of my research, computer code, or otherwise. I prefer email wherever possible.

I'm also on Twitter, and a bunch of other things like that.

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