Missions

You will work at the Institut d'Astrophysique de Paris (IAP) within the research group led by F. Leclercq and G. Lavaux, as part of the INFOCW project funded by the French National Research Agency (ANR). The project aims to develop innovative forward modelling and Bayesian inference methods for the analysis of cosmological data, particularly from the ESA's Euclid mission. We are particularly interested in the implementation and optimisation of models simulating galaxy surveys, the definition and improvement of relevant statistical summaries, and the application of implicit (simulation-based) inference techniques to constrain cosmological parameters.

You will be responsible for defining and implementing research projects within this framework, in collaboration with team members at IAP, partners of the Aquila consortium, and the "Learning the Universe" collaboration. You will contribute to producing independent and original research within the team, exploring new approaches and publishing your results in peer-reviewed scientific journals.

Activities

You will propose and carry out a research project in numerical cosmology aligned with the missions described above and consistent with the project's objectives. Your activities may include:
* Software development (C, C++, Python, JAX) and high-performance optimisation on various architectures (CPU, GPU).
* Testing and validation of algorithms and codes on simulation sets.
* Implementation and improvement of Bayesian inference algorithms.
* Analysis of Euclid DR1/DR2 data (galaxy catalogues) by applying the developed pipelines.
* Scientific writing (articles, working notes, documentation) and presentation of results at international meetings and conferences.
* Collaboration with research group coordinators and other team members.

Skills

* Knowledge/Expertise: physics, cosmology/astrophysics, numerical techniques, numerical modelling, statistics and Bayesian formalism. Experience with machine learning algorithms will be appreciated.
* Technical skills: programming (experience in at least one programming language among: C, C++, Python, JAX). High-performance computing (HPC) skills will be appreciated. Scientific communication (article writing, oral presentations).
* Interpersonal skills: autonomy, rigor, initiative, scientific ethics, ability to work in a team, openness to new scientific and technical advances.
* Languages: professional written and oral English required; French is not a requirement.
* Profile sought: The candidate must have received their PhD in astrophysics, physics, statistics, computer science, or a related field by the date of the appointment, with 0 to 4 years of postdoctoral experience.
* Application instructions: Please submit a CV, a list of publications, a cover letter, and a research project of approximately 3 pages via the CNRS portal. Have up to 3 letters of recommendation uploaded by researchers familiar with your work using the following link: https://shlink.aquila-consortium.org/postdoc-infocw-letters. For full consideration, application materials (including reference letters) should be received by 15 January 2026. Informal inquiries about the position are welcome.

Work Context

Located in the heart of Paris, the Institut d'Astrophysique de Paris (IAP) is one of the leading laboratories in cosmology and astrophysics. It brings together more than 60 permanent researchers and has a total of approximately 150 members. The "Large scale structures and the distant universe" research group, to which F. Leclercq and G. Lavaux belong, comprises about twenty permanent researchers specialising in cosmological analysis of cosmic microwave background data, galaxy surveys (notably from the Euclid mission), and measurements of gravitational lensing effects.

IAP's research themes cover a broad spectrum of major questions in modern cosmology, ranging from galaxy formation to gravitational wave astrophysics, including primordial Universe models.
You will benefit from access to high-performance computing resources, such as the Horizon/Infinity cluster (~5,600 CPU cores, ~13 V100/H100 GPUs). Funding is available for travel, visitors, and computing in accordance with ANR-funded project rules.

The CNRS has obtained the European "HR Excellence in Research" label. We are committed to equal opportunities and diversity and encourage applications from varied backgrounds. All applications will be reviewed without distinction of gender, origin, disability, or age.