I am a Professor in Cosmology and former Royal Society University Research Fellow in the Jodrell Bank Center for Astrophysics at the University of Manchester, UK. I moved here from the Institute of Astronomy at the University of Cambridge, UK, where I spent my first year as a Royal Society URF. Previously, I was at Johns Hopkins University in Baltimore, USA, working as an Associate Research Scientist with Prof. Dr. Marc Kamionkowski. Before that, I was a Senior Research Associate at the Canadian Institute for Theoretical Astrophysics in Toronto, Canada. I studied physics at the Technical University of Hannover and the Georg-August University in Göttingen, both in Germany, obtaining my Diploma in Physics (equivalent to M. Sc.) in 2001 at the Universitäts Sternwarte Göttingen. In 2005 I finished my Ph. D. at the Max-Planck-Institut für Astrophysik in Garching, Germany under the supervision of Prof. Dr. Rashid Sunyaev, where I continued working as a Post-Doc until fall 2008.

My main research interests include Cosmic Microwave Background science (CMB spectral distortions; cosmological recombination and the ionzation history; cosmological parameter estimation; Sunyaev-Zeldovich effect), atomic physics (two-photon transitions and Raman scattering; helium spectrum; collisional processes), radiative transfer (Lyman-α escape during cosmological recombination; line feedback; line diffusion and partial frequency redistribution; electron scattering), and high energy processes in the early Universe (energy transfer to the IGM by annihilating dark matter and decaying relict particles; thermalization of CMB spectral distortion in the early Universe; double Compton scattering).

My research was primarily funded through the ERC consolidator grant CMBSPEC (No. 725456), as part of the European Union's Horizon 2020 research and innovation program, and the Royal Society. This allowed me to create a big team of researchers at JBCA with a focus on CMB spectral distortion science. We have major involvements in various CMB spectrometer studies (PIXIE, PRISTINE, BISOU) and are members of The Simons Observatory. Most recently, we contributed significantly to several white papers submitted for the NASA Decadal and ESA Voyage 2050 program calls, promoting CMB spectral distortions as a future cosmological probe.

In preparation for the detailed analysis of CMB data from the Planck Satellite I developed CosmoRec, a cosmological recombination code that supersedes the physical model of Recfast. These calculations were important for the recent analysis of Planck data, in particular for the constraints on the spectral index.
In addition, I am investigating observational possibilities in connection with the cosmological recombination spectrum from hydrogen and helium, as well as spectral distortions form early energy release. For this purpose, I developed the cosmological thermalization code CosmoTherm, which can be used to compute tiny spectral distortions of the CMB blackbody caused by energy release or photon injection in the early Universe. At low frequencies, one can look for the hydrogen and helium recombination ripples from redshift ~1000 using arrays of radio antennae. The unique frequency dependence of this signal might allow us to separate it from the much larger foregrounds, an observational challenge that is addressed with the APSERa experiment.

Members of my group

• Sara Evangelista (Erasmus Master student Sept.-Dec. 2024 on spectral distortion anisotropies)
• Dr. Zheng Zhang (ERC-funded Post-doc since Jan. 2024 on AME moment expansion approaches)
• Dr. Eric Rosenberg (SO:UK Post-doc since Sept. 2023 working on SZ and systematics)

Former members

• Dr. Bryce Cyr (now Banting Fellowship @ MIT; former ERC-funded Post-doc since Sept. 2022 - Sept. 2024 on spectral distortion physics)
• Dr. Sandeep Acharya (now PDRA @ Open University of Israel; former Royal Society and ERC-funded Post-doc, Dec. 2020-Aug. 2023 on spectral distortion physics)
• Dr. Elizabeth Lee (now Software Engineer @ TNEI; former Royal Society-funded Ph.D student and ERC-funded PDRA, Oct. 2018-Aug. 2023 on the SZ effect)
• Dr. Thomas Kite (now Data scientist @ Harvard Medical School; former STFC-funded Ph.D student, Oct. 2019-Dec. 2022 working on anisotropic spectral distortions)
• Dr. Inigo Zubeldia (now PDRA @ University of Cambridge; former STFC-funded Post-doc, Nov. 2020-Sept 2022 to work on SZ effect and the Simons Observatory)
• Dr. Aditya Rotti (now researcher @ Zeiss; former ERC-funded Post-doc, March 2018 - Aug 2022, on the modeling of CMB foregrounds and future CMB experiments)
• Dr. Mathieu Remazeilles (now tenured researcher @ IFCA, University of Santander; former ERC-funded Research Fellow/Post-doc, Jan. 2018-Nov. 2021)
• Dr. Andrea Ravenni (now Post-doc @ The University of Padova; former ERC-funded Post-doc, Oct. 2018 - Sept. 2021)
• Marienza Caldarola (now Ph.D student @ IFT Madrid; former joint Master student at the University of Padova, April-Nov. 2021 on spectral distortion physics)
• Jiten Dhandha (now Ph.D student @ University of Cambridge; former Royal Society-funded Summer student, June-Aug. 2021 on 21 cm physics and global signal)
• Dr. Luke Hart (now Software Engineer @ TNEI; former ERC-funded Post-doc [May 2020-July 2021] and Royal Society-funded Ph.D student [Oct. 2016-Apr. 2020])
• Dr. Francesco Pace (now tenure-track @ University of Torino; former ERC-funded Post-doc, April-December 2020)
• Dr. Boris Bolliet (now Lecturer @ University of Cambridge; former ERC-funded Post-doc, Sept. 2017-Aug. 2020)
• Charis Pooney (now Ph.D student @ King's College London; former M.Phys student, Sept. 2019 - May 2020)
• Dr. Abir Sarkar (now College teacher @ Mahishadal Raj College; former ERC-funded Post-doc, Sept. 2017-March 2020)
• Prof. Liang Dai (now Assistant Prof. @ UC Berkeley; former Ph.D student together with Marc Kamionkowski, JHU, Sept. 2012-Aug. 2014)
• Prof. Marzieh Farhang (now Associate Prof. @ Shahid Beheshti University; former Ph.D student together with Dick Bond, CITA, Sept. 2008-Aug. 2012)

Latest News

• Book about the Hubble constant tension has appeared!
• News article about BISOU is moving to Phase A
• Recording of a talk at Cosmology from Home 2024 about Synergistic Opportunities with CMB Spectral Distortions
• Our papers on spectro-spatial evolution of the CMB got published in the JCAP 20th Anniversary Special issue
• The UoM Schuster Colloquium webpage with information about past and upcoming talk: click here
• First CMB spectral distortion Wikipedia page initiated by the CMBSPEC team: click here
• ESA Voyage 2050 report released with mentioning of CMB spectral distortions in L-class category: click here
• Added CSpack git repository: click here
• Released data for spectral distortion limits on large energy injection: click here
• Added a BRpack webpage (work in progress): click here

Highlights and Outputs

• Spectral Distortion Science White paper submitted to the ESA Voyage 2050 call. A copy of the white paper can be found here.
• Spectral Distortion Science White paper submitted for the Astro 2020 Decadal review process.
  A copy of the white paper can be found here and a list of additional endorsers here
• Gruber Cosmology Prize 2018 went to the Planck team! Here one of the many articles about this click here
• Awarded ERC-Consolidator Grant 2016 (2M Euro of funding for my research!).
• Summary of ΛCDM signals made available at: click here

Workshops

• Lorentz Center workshop on Spectro-polarimetry of the Microwave Sky, Oct 31-Nov 4, 2022: click here
• Parallel session on CMB spectral distortions at the Virtual Marcel Grossmann meeting, 2021: click here
• Parallel session on CMB spectral distortions at the Marcel Grossmann meeting, 2018 in Rome: click here
• CERN TH Institute on Probing fundamental physics with CMB spectral distortions in Geneva: click here
• Workshop on Dark Ages and White Nights in Saint Petersburg: click here
• Discussion on CMB spectral distortions from cosmic baryon evolution at RRI in Bangalore: click here
• Workshop on CMB spectral distortions: click here

Software Packages

• My main Git repositories: click here


• The main Git repositories of the CMBSPEC team: click here
• BRpack: fast calculation of electron-ion Gaunt factors: click here
• CosmoSpec: fast calculation of the cosmological recombination radiation: click here
• CosmoRec: Cosmological recombination and high precision computation of hydrogenic atoms and neutral helium: click here
• Recfast++: Simple cosmological recombination code: click here
• The cosmological thermalization code, CosmoTherm: click here
• High precision computation of the SZ effect with SZpack: click here

Invited Lectures

• Lectures at the ICTS School (webpage) on Cosmology - The Next Decade, Jan 3rd-25th, 2019, Bangalore, India
  (Lecture I: pdf and video, Lecture II: pdf and video, Tutorial: video)


• Lectures at the ICCUB School (webpage) on Hot Topics in Cosmology, Oct 2017, Barcelona, Spain
  (Lecture I: pdf, Lecture II: pdf, Lecture III: pdf and Lecture IV: pdf)


• Lectures at the International School of Physics "Enrico Fermi" (webpage) on Gravitational Waves and Cosmology, July 2017, Varenna, Italy
  (Lecture notes: pdf and slides: pdf)


• Lectures at the Les Houches School (webpage) on Cosmology after Planck: what is next?, April 2016, Les Houches, France
  (Lecture I: pdf and Lecture II: pdf)


• Lectures at the ISAPP School on Cosmology (webpage) on CMB Spectral Distortions, June 15th-25th 2015, Paris, France
  (Lecture: pdf)


• CUSO Lectures (webpage) on Science with Spectral Distortions of the Cosmic Microwave Background, Oct 16th- Nov 6th 2014, Geneva, Switzerland
  (Lecture Notes (still incomplete): pdf and associated Slides I, II, III and IV )


• GIF Lectures (webpage) on Spectral Distortions of the CMB, Sept 8th-12th 2014, Paris, France
  (Lecture: pdf)


• Lectures at the School on Cosmology Tools (webpage) on CMB physics (pdf), Recombination physics (pdf) and Recombination codes (pdf),
  Nov. 12-15, 2013, Madrid, Spain


• Lectures at the KEK Workshop on Particle Physics Phenomenology (webpage) on CMB Cosmology and Particle Physics, Sept/Oct 2013, Tsukuba, Japan
  (Lecture I: pdf and Lecture II: pdf)


• Les Houches Lectures (webpage) on The Physics of CMB Spectral Distortions, July/Aug 2013, Les Houches, France
  (Lecture I: pdf and Lecture II: pdf)

Publications

• Articles on astro-ph
• Articles on ADS
• Chapter in book about the Hubble constant tension
• Chapter in book about Recombination to Reionization

Popular Science Articles

• Why the Big Bang’s Light May Have a Tilt, Quanta Magazine article by Maggie McKee on spectral distortions, June 2015
• Next Steps for Cosmology, Perspective published in Science together with Joe Silk, May 2014
• Mapping the Universe with Helium, Scientific American article by George Musser, May 2009
• What can the cosmological recombination radiation tell us about the thermal history of the Universe?, MPA Research Highlight, June 2008
• Cosmological hydrogen recombination lines from redshifts z~1400, MPA Research Highlight, July 2007

Downloads

• Curriculum Vitae (as pdf)
• List of Publications and Talks (as pdf)
• Doctoral Thesis (as pdf)
• Diploma Thesis (as pdf in german)
• Pictures on my private Homepage

Miscellaneous external links