Scientific Series

Although we will never get the same level of details for exoplanets as we do for Solar System bodies, the large diversity of exoplanets revealed by exoplanet hunting missions, e.g. Kepler and TESS, provide thousands of study cases to refine formation and evolution pathways as well as theories of how their climate is shaped by their environment. Particularly amenable for atmospheric characterization, short-period exoplanets with dayside blasted with stellar radiation are some of the best-characterized exoplanets to this day. Due to their synchronous rotation, they exhibit large day-to night difference, and their observation can be difficult to interpret without a full understanding of their “3D-ness”. In the past 2 decades, a suite of observational techniques along with new space-based (e.g. JWST) and ground-based observatories with exquisite precision that now allows us to reveal the inhomogeneous nature of these exoplanets and provide a more comprehensive view into their atmosphere, or lack thereof. In this talk, I will present what we have learned from observations of a variety of close-in planets ranging from scorching hot exoplanets and how these observational techniques are now used to study temperate rocky planets to investigate their habitability.

The theory of quiver varieties provides a fundamental bridge between representation theory, enumerative geometry, and physics. From 3d mirror symmetry, any quiver variety comes with a dual variety known as the Coulomb branch. A conjecture proposed by Bullimore-Dimofte-Gaiotto-Hilburn-Kim and, independently, Okounkov, asserts that the cohomology of the moduli space of quasimaps to a quiver variety admits a canonical action by the quantized coordinate ring of the dual BFN Coulomb branch. In this talk, I will report on progress on refining this conjecture and proving it. The construction relies on a -1 shifted symplectic structure on the moduli space of quasimaps and the theory of cohomological Hall algebras. Based on work in preparation with Spencer Tamagni.

In the search for a consistent and renormalizable quantum theory of gravity, a conservative possibility is that gravity admits a field-theoretic description valid up to arbitrarily high energies. This amounts to going beyond the perturbative non-renormalizability of general relativity and it can be achieved following different strategies. One is to abandon Lorentz invariance as a fundamental symmetry to gain power-counting renormalizability, as in Hořava Gravity. In Asymptotically Safe Gravity, ultraviolet completeness instead arises from a non-perturbative renormalization group fixed point, preserving spacetime symmetries. In both cases, the peculiar UV structure of the theory reflects in its low-energy description, with a particular imprint on black hole physics. In this talk, I will explore these two scenarios as UV description of gravity. I will focus both on their high-energy description, reviewing some recent developments, and on the possible low-energy physics stemming from each assumption.

Neutron stars are ultra-dense remnants of massive stellar cores, observable across the electromagnetic spectrum. Their emission reflects a delicate interplay of magnetic, thermal, and structural processes under extreme conditions of density, temperature, and magnetic fields—regimes unattainable in terrestrial laboratories. Among neutron stars, magnetars stand out, hosting the strongest magnetic fields in the Universe. Their intense X-ray activity, recurrent outbursts, and unusually slow rotation point to powerful interior dynamics, yet the origin of the large-scale dipolar fields that drive their long spin periods remains a longstanding mystery. In this talk, I will introduce MATINS, a new open-access 3D code for modeling the coupled magneto-thermal evolution of isolated neutron stars. Focusing on the evolution of magnetic fields in magnetar interiors, I will discuss the key mechanisms operating under these extreme conditions, in particular the chiral magnetic effect—a phenomenon arising from the chiral anomaly that enables the conversion between magnetic helicity and electron chiral asymmetry. I will present simulations for both non-zero and vanishing initial magnetic helicity, the latter reflecting realistic conditions at the birth of a proto–neutron star. Our results show that the chiral magnetic effect can naturally transfer energy from small-scale magnetic fields at birth into the large-scale dipolar fields observed in magnetars without requiring external energy input. This provides a compelling mechanism for magnetar formation.

Axions are some of the best-motivated beyond the Standard Model particle candidates at present. These ultralight particles may account for the cosmological dark matter and explain other outstanding problems in nature, such as the strong-CP problem; they also are now known to emerge generically in string theory.  Axions are expected to couple ultra-weakly with ordinary matter, which complicates their detection. However, thanks to recent theoretical, experimental, and observational progress these particles may be discovered or ruled out within the near future. I will review some of the recent ideas that may soon play a role in axion discovery, including computing the evolution of axions in the early universe using supercomputers and novel observational signatures of axions that emerge in extreme astrophysical environments such as supernovae.

Studying low-redshift analogues of phenomena in the early Universe is an established method for getting a closer look at intriguing physics. However, determining when a local analogue functions well to represent distant systems, and what limitations need to be kept in mind, can be challenging. Notably, low redshift examples often reveal complexity that gets hidden when looking at high redshift objects. For distant objects, limited spatial and spectral resolution and reduced sensitivity can lead to extraordinary claims that do not hold up over time. I'll discuss specific examples of local analogues that reveal complexity that should be considered when studying distant objects, focussing on local compact galaxy groups and super Eddington-accreting active galactic nuclei.

The range of possible masses of particle dark matter spans over many orders of magnitude. The extremes of the mass range -- so-called ''superheavy'' and ''ultralight'' dark matter candidates -- are increasingly attracting attention due to their novel phenomenology and new developments in production mechanisms. In this talk I will discuss the complementary nature of superheavy and ultralight dark matter, starting from the production during cosmic inflation, using examples from the string theory axiverse and from a QCD-like dark sector.