Postdoctoral Researcher - The Cosmic Microwave Background as a New Probe of Dark Matter Production

Organisation/Company Adam Mickiewicz University, Poznań Research Field Physics Researcher Profile Recognised Researcher (R2) Positions Postdoc Positions Final date to receive applications 31 Aug 2026 - 23:59 (Europe/Warsaw) Country Poland Type of Contract Temporary Job Status Full-time Hours Per Week 40 Offer Starting Date 1 Oct 2026 Is the job funded through the EU Research Framework Programme? Not funded by a EU programme Reference Number UMO-2025/59/D/ST2/ Is the Job related to staff position within a Research Infrastructure?

No

The project is devoted to dark matter (DM). In many popular models, DM appears as a weakly interacting massive particle (WIMP), whose presence should give rise to characteristic experimental signals. The absence of such signals indicates the need to consider less conventional scenarios. In particular, DM may interact very feebly with Standard Model (SM) particles or have its mass significantly above the electroweak scale, remaining beyond the reach of conventional experimental methods.

On the one hand, such scenarios often predict a dependence of the DM relic abundance on the reheating dynamics, in particular on the reheating temperature, TR. On the other hand, there is a relation between CMB observables and TR (for a given model of inflation).

The aim of the project is to develop theoretical and phenomenological methods for investigating such DM scenarios using observations of the Cosmic Microwave Background (CMB). This approach complements conventional search methods and enables tests of DM models that may remain beyond their reach.

The project builds on a recently developed framework that uses CMB data both to test models of cosmological inflation and to investigate scenarios beyond the SM that depend on TR. The planned research includes further development of this framework and its application to specific TR-sensitive DM models, such as Higgs portal models or supersymmetric models.

In our previous work, we demonstrated that constraints on TR derived from CMB observations enable tests of otherwise elusive freeze-in scenarios. These results were obtained within a standard one-parameter effective description of perturbative reheating, in which the inflaton decay width is the only free parameter, while the constant equation-of-state parameter is fixed by the dynamics of the oscillating inflaton.

• Applying the CMB-based approach to test the TR-sensitive freeze-in mechanism in axion-portal scenarios, in which the axion acts as a mediator connecting the SM to a hidden DM sector.
• Extending the developed framework to TR-sensitive freeze-out scenarios; applying it to concrete models such as those outlined above.
• Investigating the impact of the non-perturbative phase of inflaton decay (in alpha-attractor models) on the possibility of testing DM models using CMB observations, employing semi-analytical methods as well as numerical evolution of the inflaton field using lattice simulations.
• Determining the significance of non-instantaneous thermalisation of inflaton decay products (which affects both DM production and the TR–CMB link) for CMB tests of TR-sensitive DM models.
• codes are well documented and overseeing their use and further development by a PhD student.

• Independently surveying the literature, studying in detail selected papers and accurately reproducing the analytical and numerical results.
• Developing, testing and maintaining analytical and numerical codes for calculating dark-matter cross sections, solving Boltzmann equations and performing parameter scans, ensuring that these
• Contributing to the preparation of manuscripts.
• Participating in regular group meetings and reporting on the progress of the assigned research tasks.
• Disseminating the project results by preparing and giving talks at international conferences and local seminars held at Polish institutions.

Research Field Physics Education Level PhD or equivalent

Skills/Qualifications

The competition is open to individuals who meet the requirements specified in Article 113 of the Law on Higher Education…