I work as a Royal Society University Research Fellow (proleptic Reader) 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, where I worked as an Associate Research Scientist with 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 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).

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.

My group

• Luke Hart (Royal Society funded Ph.D student since Oct. 2016 on the cosmological recombination era and radiation)
• Abir Sarkar (ERC-funded Post-doc since Sept. 2017 on cosmological thermalization physics)
• Dr. Boris Bolliet (ERC-funded Post-doc since Sept. 2017 on non-standard sources of CMB spectral distortions)
• Dr. Mathieu Remazeilles (ERC-funded Post-doc starting Jan. 2018 on the modeling of CMB foregrounds and future CMB experiments)
• Dr. Aditya Rotti (ERC-funded Post-doc starting March 2018 on the modeling of CMB foregrounds and future CMB experiments)

Latest News

• Summary of ΛCDM signals made available at: click here
• Added a CosmoSpec webpage (work in progress): click here

Workshops

• 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

• 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
• The cosmological thermalization code, CosmoTherm: click here
• High precision computation of the SZ effect with SZpack: click here

Invited Lectures

• 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: 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: 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

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