The calculation of the branching ratio for the inclusive decay $\bar{B} \rightarrow X_s \gamma$ has been an active field of research for multiple decades, yielding results that work very well as a standard candle of the Standard Model of Particle Physics (SM). In this work, we calculate the remaining pieces for the branching ratio of the four-body decay of a b quark into an s quark, a photon $\gamma$ and two additional quarks $q\bar{q}$ at NLO in the strong coupling $\alpha_s$. This calculation involves the one-loop process $b \rightarrow s q \bar{q} \gamma$, with a virtual gluon, as well as the tree-level contribution to $b \rightarrow s q \bar{q} g \gamma$. In this talk, I will highlight the challenges that arise in the computation of the contribution and present a result which allows for a reduction of the theory uncertainty in the $\bar{B} \rightarrow X_s \gamma$ decay rate.

In the ΛCDM cosmological model the Universe is assumed to be isotropic and homogeneous when averaged on large scales. That the Cosmic Microwave Background (CMB) has a dipole anisotropy is interpreted as due to our peculiar (non-Hubble) motion because of local inhomogeneity. There must then be a corresponding dipole in the sky distribution of sources at high redshift. Using catalogues of radio sources and quasars we find that this expectation is rejected at >5σ, i.e. the distribution of distant matter is not isotropic in the 'CMB frame’. This calls into question the standard practice of boosting to this frame to analyse cosmological data, in particular to infer acceleration of the Hubble expansion rate using Type Ia supernovae, which is then interpreted as due to a Cosmological Constant Λ. We find that the inferred acceleration is in fact anisotropic (in the direction of the CMB hotspot) and likely illusory because of our being embedded in a coherent bulk flow, rather than due to dark energy.

One of the prime questions in modern astrophysics is the origin and evolution of chemical elements. Why is the chemical composition so vastly (as of today, ~8 orders of magnitude) different for various astronomical objects, such as the Sun, Galactic stars and their planetary companions? How can one explore the full history of the evolution of elements, from the Big Bang to the present? I will review recent progress in studying the chemical enrichment of the Milky Way galaxy. I will focus on advances in determining solar and stellar chemical composition, driven by new observations and new theoretical models. These models rely on the physics of non-local thermodynamic equilibrium (NLTE) and 3D radiation-hydrodynamics simulations of stellar convection. I will touch upon the key science topics: - how 3D NLTE solar abundances have advanced our understanding of the structure of the Sun and its neutrino fluxes, - how evidence for non-standard supernova Ia explosions has emerged from 3D NLTE abundances of iron-group elements, - how constraints on the properties of neutron star mergers can be obtained from observations of the heavy neutron-capture elements in stellar spectra. I will conclude with a brief summary of the prospects for studies of stars using 3D NLTE modelling and next-generation large astronomical surveys.

Quantum sensing based on nitrogen-vacancy (NV) centers in diamond is a disruptive technology with immense scientific and technological potential. These sensors can detect faint magnetic fields from nuclear spins for NMR applications [1] and monitor ion interactions in battery cells [2]. To date, however, the most outstanding scientific results have been achieved in complex laboratory setups, whose size and complexity limit the deployment of quantum sensing in industry-relevant fields such as medical technology, automotive, or aerospace. Recognizing this challenge, the scientific community has begun developing portable quantum sensors [3]. A major hurdle is that while lab-based systems allow for full control over all parameters affecting sensitivity, enabling remarkable magnetic field sensitivities of < pT/√Hz, portable sensors inherently lack this level of control, leading to inferior performance. Our research focuses on a specific class of portable devices: endoscopic based quantum sensors with a diamond crystal integrated onto the tip of an optical fiber. This design faces the particular challenge of limited photon collection efficiency through the fiber. To overcome this limitation, we have investigated a novel approach utilizing a multi-core optical fiber design. In our setup, one core is dedicated to the 532 nm laser excitation of the NV centers, while the remaining cores are used exclusively for collecting the emitted fluorescence of the phonen side band. This separation of excitation and collection paths has enabled us to achieve a magnetic field sensitivity of ~150 pT/√Hz. To the best of our knowledge, this result represents a significant improvement over the state-of-the-art for endoscope-based quantum sensors (typically in the nT/√Hz range) and marks a critical step towards practical, high-performance quantum sensing applications. Furthermore, we were able to integrate all required electronic in optical components in a small box, which makes the quantum sensor truly portable. [1] Jonas Meinel et al., High-resolution nanoscale NMR for arbitrary magnetic fields, Communications Physics 6, 302 (2023) [2] Maximilian Hollendonner et al., Quantum Sensing of electric field distributions of liquid electrolytes with NV-centers in nanodiamonds, New J. Phys. 25, 093008 (2023) [3] A. J. Newman et al., Endoscopic diamond magnetometer for cancer surgery, Phys. Rev. Applied 24, 024029 (2025)