Dr Alkistis Pourtsidou

Dr Alkistis Pourtsidou

Lecturer in Cosmology
School of Physics and Astronomy
Queen Mary, University of London
327 Mile End Road, London, E1 4NS

Telephone: 0207 882 3463
Room: GO Jones 507

Theoretical and Observational Cosmology

My research spans a wide variety of projects in theoretical and observational cosmology. My favourite current topics include: 

  • Construction, parametrization, and observational signatures of interacting dark energy models
  • Non-linear effects of dark energy and modified gravity.
  • Radio cosmology with the innovative 21-cm intensity mapping technique.
  • Observational cosmology with optical and radio surveys such as Euclid, LSST, and the SKA.

I am a member of large international collaborations of scientists. This means that I have the opportunity to work on some of the most interesting problems in Cosmology together with colleagues from all over the world! 

One of my main theoretical research topics is interacting dark energy. This usually means that dark energy is taken to be an evolving field in time (dubbed "quintessence") that is allowed to have a non-gravitational coupling with dark matter. Together with collaborators, I discovered a new class of models that only involves momentum exchange; this is very interesting as it can reconcile current "tensions" we see between data from the Cosmic Microwave Background and low redshift probes such as weak lensing. In Fig. 1, you can see how these models can reconcile this tension (basically the coloured contours corresponding to the momentum exchange models overlap better than the black one, which is the standard cosmological model, with the PlanckSZ and CFHTLens data).

Fig. 1: Reconciling the CMB-LSS tension with dark energy interactions (Pourtsidou & Tram 2016).

One of my main observational research topics is cosmology with the 21-cm intensity mapping technique. This is an innovative method to perform cosmological measurements: it does not require the detection of individual galaxies but instead it measures the collective neutral hydrogen (HI) emission from large regions (see Fig. 2). The end product is a set of temperature maps, similar to the CMB but in 3D, i.e. across the sky and along time. I am particularly interested in  cross-correlations of intensity mapping with optical and CMB surveys in order to probe the evolving history of the Universe, study dark energy and inflation, and mitigate systematic effects. 

Fig.2: From individual galaxies (Left) to intensity maps (Right).

International collaborations

  • SKA (Square Kilometre Array)
  • EUCLID Consortium
  • LSST (Large Synoptic Survey Telescope)

Undergraduate teaching and supervision

My teaching for this year includes:

  • Tutor for Synoptic Physics (Semester A)
  • Lecturer for Physical Cosmology (SPA 6311, Semester B)
  • Supervision of undergraduate projects
  • Supervision of MSc projects

An up-to-date list of my publications from the INSPIRE database can be found here.

Co-I in "SA-DISCNet: A collaborative data science training network across southern Africa and southern UK". There are 13 Co-Is in total, from institutes across South Africa and the UK. The grant, funded by the STFC, is for creating a collaborative data science training network across SA and UK, part of SEPNET and AIMS (African  Institute of Mathematical Science). It involves an intensive school for African students in machine learning,  statistics, and high performance computing, followed by an 8-week data science workshop. An internship scheme for the students will follow. The budget is 100,000 GBP for 1 year.

This is not an exhaustive list and I would be happy to discuss other project possibilities.