Postdoctoral Researcher in Differentiable Modelling and Cosmological Inference for Rubin/LSST in Astroparticule et Cosmologie (APC, CNRS) – France

Summary

The AstroDeep project, a joint effort between the Astroparticule et Cosmologie (APC) and CosmoStat at CEA Paris‑Saclay, seeks a postdoctoral researcher to develop differentiable cosmological models and inference methods for the LSST survey. The two‑year fixed‑term position in Paris involves creating forward‑modelling frameworks, applying them to simulations and precursor data, integrating tools into LSST pipelines, and publishing open‑source code. Candidates must hold a PhD (or be near completion) in a relevant field, possess strong Python and collaborative development skills, and be proficient in English. The role offers a gross monthly salary of €3,132.83–€4,343.20, generous leave, health coverage, transport reimbursements, and remote‑work options, within an inclusive, international research environment.

Key Facts

Department	Astroparticule et Cosmologie (APC)
Position Type	Postdoctoral Researcher
Discipline	Cosmology, Astrophysics, Statistics, Data Science
Research Area	Differentiable Modelling and Cosmological Inference for Rubin/LSST
Degree Required	PhD (or expected shortly) in astrophysics, cosmology, physics, statistics, or related field
Salary	Gross monthly salary between €3,132.83 and €4,343.20, depending on experience
Funding	Salary
Contract Duration	Fixed-term, 24 months
Language	English
Deadline	2026-10-29
Required Documents	Application submitted through the CNRS Employment Portal (offer reference: UMR7164-KEVVEL-059)

About the Project

AstroDeep aims to exploit the full information content of Phase IV imaging surveys by building a unified, probabilistic, and differentiable framework for cosmological analysis. The project focuses on forward modelling of large‑scale structure and weak gravitational shear, linking cosmological parameters to observables through automatically differentiable simulations, and applying these tools to LSST data within the LSST DESC collaboration.

Key Responsibilities

• Develop and validate differentiable cosmological models for large‑scale structures and shear observables
• Develop inference methods using model gradients to assess biases, uncertainties, and systematic effects
• Apply the workflow to realistic simulations and precursor survey data, preparing for LSST Y1 analysis
• Integrate tools into LSST pipelines and validate them on representative survey volumes
• Document and release open‑source code and disseminate results via publications and presentations

Required Skills

• PhD (or expected shortly) in astrophysics, cosmology, physics, statistics, or related field
• Good command of at least one of: cosmological simulations, large‑scale structure evolution, weak gravitational shear, differentiable modelling, Bayesian inference, gradient‑based inference
• Experience with automatic differentiation frameworks such as JAX or PyTorch (advantageous)
• Strong Python programming skills and experience with collaborative development (Git/GitHub, CI/CD, open‑source practices)
• Ability to conduct research independently while contributing to an interdisciplinary team
• Excellent scientific communication skills in English, both written and spoken
• Experience in cosmological data analysis or large astronomical collaborations (e.g., DES, LSST DESC) is an asset

Who Should Apply

Early‑career researchers with a PhD (or near completion) in astrophysics, cosmology, physics, statistics or a related discipline who have strong Python programming skills and can work independently in an interdisciplinary, international team.

Benefits

• Gross monthly salary €3,132.83–€4,343.20 depending on experience
• 44 days of annual leave and RTT
• Comprehensive health cover
• Subsidised meals
• Optional French language courses
• Public transport costs reimbursed at 75% plus up to €300 mobility allowance
• Remote‑working practice and compensation

About the Employer

Astroparticule et Cosmologie (APC) is a joint research unit of Université Paris Cité and CNRS located in Paris, France. It focuses on cosmology, astrophysics, statistics and data science and participates in major international projects such as Euclid and the LSST DESC.

Frequently Asked Questions

What is the contract length?

Fixed‑term for 24 months.

What is the salary range?

Gross monthly salary between €3,132.83 and €4,343.20.

When is the application deadline?

October 29, 2026.