Missions

We are pleased to invite applications for a post-doctoral fellowship in theoretical high-energy multi-messenger astrophysics at APC (Astroparticule & Cosmologie, CNRS - Université Paris-Cité). The preferred start date for this position is Fall 2026, with an initial appointment of two years and the possibility of renewal for up to three years. This fellowship is part of the ANR-funded HENBoS (High-Energy Neutrinos from Black Hole Systems) project, which seeks to characterise with unprecedented accuracy massive black hole systems as cosmic accelerators and sources of very high-energy photons, cosmic rays and neutrinos.
The post-doctoral fellow will conduct high-performance GR-MHD numerical simulations of accreting supermassive black holes using the latest version of the GRAMRVAC code, developed in-house. The primary focus of these simulations will be on identifying and investigating the particle acceleration processes in these extreme environments. To this effect, the post-doctoral fellow will contribute to the development and application of the hybrid simulation code mPIC-GRAVAC in general relativity. This code integrates a magnetohydrodynamic (MHD) description of the thermal plasma with a Particle-In-Cell (PIC) modelling of supra-thermal particles, enabling cutting-edge simulations of the immediate vicinity of supermassive black holes. These simulations constitute the core task of the HENBoS project and will be complemented by theoretical studies to establish definitive predictions for multi-messenger emission.
We are seeking highly motivated individuals with robust expertise in computational plasma astrophysics (MHD, GRMHD or PIC) and post-PhD research experience. The ability to work effectively in a collaborative team environment is essential.
The HENBoS project, led by Martin Lemoine, brings together a team of experts in multi-messenger theory, GR-MHD simulations, and VHE multi-messenger data analysis. The post-doctoral fellow will collaborate closely with Fabien Casse and Peggy Varniere, developers of the mPIC-GRAVAC code, and will have the opportunity to engage with other project collaborators. APC is a vibrant research unit of CNRS and Université Paris-Cité, actively involved in major experimental and theoretical projects in cosmology, multi-messenger astrophysics, and particle physics. The post-doctoral fellow will have access to excellent computing facilities, including a local cluster and national supercomputing centers.

Activities

- Contribute to the development and application of the hybrid simulation code mPIC-GRAVAC in general relativity.
- Conduct high-performance GR-MHD numerical simulations of accreting supermassive black holes.
- Identify relevant sites of energy dissipation into high-energy particles and participate in the modelling of the ensuing radiative signatures.

Skills

Robust expertise in computational plasma astrophysics (MHD, GRMHD or PIC) and post-PhD research experience.

Work Context

The post-doctoral fellowship will take place in the framework of the ANR funded HENBoS project (2025 – 2029), which seeks to describe with unprecedented accuracy and scope massive black hole systems as cosmic accelerators. Our vision and our understanding of supermassive black hole systems have indeed known dramatic progress over the last decade. In particular, they have shown that these objects behave as accelerators of very high energy particles (VHE) and that they are likely sources of (VHE) neutrinos. Understanding where and how particles are accelerated in these extreme environments has thus become a key question, with far-reaching consequences for multi-messenger astrophysics and black hole astronomy. The HENBoS project is part of this rapidly developing context. The strategy is based on high-performance numerical simulations using a GRMHD-PIC technique, which allows to track VHE ions on the fly. These simulations will be supplemented by cutting-edge analytical methods for injecting particles onto the grid, and convolved with advanced radiative codes to calculate fluxes and multi-messenger spectra. The overarching goal of this ambitious program is to describe the acceleration process across length scales for different accretion regimes and types of sources, to carry out specific studies for certain sources, and establish detection forecasts for future multi-messenger detectors.

Constraints and risks

No particular risks.
Travel within France and abroad is to be expected.