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 is focused on a variety of projects, ranging from pure theory such as exotic models of dark energy and their possible interactions with dark matter, to more observational like cosmology with large scale structure surveys. 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 favourite 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. This means that they can decay to one another, for example. Together with collaborators, I discovered a new class of models that only involves momentum exchange and 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 favourite observational research topics is 21-cm intensity mapping. 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. I am also working on the construction, parametrization and observational signatures of Interacting Dark Energy theories.

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

International Collaborations

  • SKA

Undergraduate teaching and supervision

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

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

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