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Abstract

This thesis focuses on studying small-scale dark matter structures. On the one hand, we study very small dark matter structures within the solar system formed by two primary candidates, axions and WIMPs. Exploring how these particles may cluster and produce signals, we test their detectability in light of current and future ground-based experiments. On the other hand, we also study the density profiles of small dark matter halos to address the core-cusp problem, placing these dark matter structures in the broader context of dark matter's distribution on cosmic scales.

For axions, we study the detection of axion miniclusters via haloscope measurements to determine their gravitational potential and density. Our method allows us to measure the axion-photon coupling and the dark matter density separately from a single experiment. We also examine quantum states of axion dark matter, focusing on axion-nucleus interactions and the origin of relevant oscillation frequencies, in particular, on how the quantum state of axions influences observables in experiments. We focus on spin interactions using a Jaynes-Cummings approach and discuss suitable observables for experiments like CASPEr. Nonetheless, the insights gained in our approach can be extrapolated to other experimental setups, such as haloscope cavities.

For WIMPs, we analyze the time-structure signatures of small-scale dark matter clumps, comparing spectral densities of homogeneous versus clumpy distributions. This helps characterize potential time-dependent signals of clumps and estimate detectability in light of future experiments like XENONnT, DARWIN, and future extensions. Finally, looking into small-scale structures, yet larger than the local scale, we explore how exothermic processes in warm dark matter, specifically self-annihilations of SIMPs and ELDERs, impact density profiles of dark matter halos in dwarf galaxies, particularly focusing on how $2 \rightarrow 2$ and $3 \rightarrow 2$ reactions flatten these profiles, offering insights into dark matter's role on slightly larger scales.

This work provides new insights into the detection and characterization of axion and WIMP dark matter, contributing to understanding their role in the cosmic structure and local distribution.