PhD student in Theoretical Physics: Theoretical Cosmology of the Early Universe

Project description

Subject area: Theoretical Physics

What laws of nature governed the early universe, and how can we learn about them from experiments and astronomical observations? We invite applications for a PhD position in theoretical physics at the intersection of high-energy particle physics and cosmology. The goal of the project is to tackle some of the most profound open questions in fundamental physics.

As a PhD student, you will develop the theory, cosmology, and phenomenology of well-motivated extensions of the Standard Model. You will devise and explore new solutions to puzzles such as the nature of dark matter, the origin of cosmic structure, and the dynamics of the early universe, and you will confront these theories with observations and experiments from astroparticle physics, cosmology and particle physics.

One exciting direction for this PhD project is the study of cosmic phase transitions in the early universe. Recent work from our group has shown that first-order phase transitions can modify field-theory parameters (e.g., by shifting gauge couplings), leading to dramatic cosmological consequences. For example, such phase transitions can result in stable “relic pockets” of false vacuum, offering a new theory of dark matter distinct from conventional paradigms. Moreover, such phase transitions can generate powerful gravitational-wave signals that can be tested using Pulsar Timing Arrays or upcoming gravitational-wave detectors. This work connects theoretical cosmology, quantum and classical field theory, particle physics model building, and astroparticle physics.

Over the course of the PhD, additional questions within cosmological inflation, dark matter physics, baryogenesis, string theory & cosmology, and axion physics may be explored. The scope of this work will be influenced by the candidate’s interests, strengths, and the evolving research landscape.

As part of the Cosmology, Particle Astrophysics and Strings division at Stockholm University, you will work within the Oskar Klein Centre alongside over 100 researchers spanning theory and observation. Our location at the AlbaNova campus, shared with Nordita (the Nordic Institute for Theoretical Physics), KTH, and multiple SU research groups, offers the possibility for daily interactions with experts across theoretical physics, cosmology, and astrophysics through joint seminars, informal discussions, and collaborative projects. We foster a supportive, inclusive environment that emphasises creativity and mentorship, helping you build both technical depth and the independence essential for a successful research career.

We typically receive many dozens of applications for each available place in this group. The successful candidate is likely to have a strong track record in theoretical physics at the undergraduate and Master’s levels, including coursework or projects in quantum field theory and cosmology. We evaluate applications holistically and recognise that strong candidates come from diverse educational paths and backgrounds. We welcome applications from all qualified candidates and work actively to promote diversity and equal treatment.

Ref. No. SU FV-4658-25

Closing date: 2 March 2026

Complete information here