The origin and maintenance of magnetic fields is an outstanding question of modern cosmology and astrophysics. Dynamo and compression mechanisms during gravitational collapse accompanying the structure formation can only amplify existing magnetic fields, but cannot explain their genesis. The need for a “seed” field motivates the investigation of primordial origin of magnetic fields. The search for primordial magnetic fields is further inspired by recent gamma-ray observations of distant blazars (highly energetic active galactic nuclei with jets pointing toward Earth), which set lower limits on the magnetic field strength and suggest the existence of magnetic fields in intergalactic voids.
Primordial magnetic fields could have been produced either during inflation, a brief period of extremely rapid expansion that occurred fractions of a second after the Big Bang, or during subsequent cosmological phase transitions. Such fields could provide a natural explanation for the magnetic fields in the intergalactic medium, and also serve as a powerful probe of high-energy physics in the early universe. However, generating large-scale magnetic fields during inflation remains challenging, as they typically dilute or decay with the universe's expansion.
The goal of this project is to investigate a theoretically well-motivated scenario of magnetogenesis during axion inflation, where the axion, a pseudoscalar field commonly arising in high-energy theories, is coupled to Standard Model gauge fields. This coupling can lead to a strong amplification of gauge-field fluctuations, thereby improving the prospects for producing observable primordial magnetic fields. Specifically, the project focuses on the case where the axion couples to non-Abelian gauge fields (SU(2)), which possess self-interactions that can lead to qualitatively new phenomena in the early universe. We perform detailed analytical and numerical studies of the axion-SU(2) system to identify viable magnetogenesis scenarios, further investigating how key early-universe effects influence the generation of magnetic fields, and determine how these processes relate to the generation of primordial gravitational-wave signals, a complementary probe of inflationary physics.
By combining expertise in early-universe cosmology, high-energy theory, astrophysics, and advanced numerical tools, the project delivers precision predictions for the spectra of primordial magnetic fields and gravitational waves. These predictions will serve as theoretical templates for upcoming observational missions, facilitating direct confrontation between theory and observation. Beyond its scientific contributions, the project provides open-access computational tools for simulating gauge-field dynamics coupled to axions, empowering the broader research community to explore new aspects of the early universe and potentially uncover novel physics.
