Dear Colleagues,

The cosmos provides us with a continuous influx of cosmic rays ranging from the tiniest quanta of energy, such as the yet undetected cosmic background neutrinos, up to the most energetic single-particle events ever observed by humanity. In this rising age of gravitational wave observatories, neutrino telescopes, and exquisitely precise photon detectors, it is essential that we exploit this information through a truly interdisciplinary approach to multi-messenger astronomy. This entails an enormous spectrum of new opportunities across all frontiers, ranging from the exploration and characterization of cosmic sources, charting the decomposition, origin, and evolution of the universe all the way to the exploration of elementary particle properties themselves.

Important lessons are to be learned, for example, about our cosmic neighborhood, the spectrum of binary black holes, as well as the possibility of primordial black holes as well motivated candidates for astrophysical dark matter. At the same time, particle dark matter searches are running with unprecedented sensitivities and will soon reach the neutrino floor, allowing for detection of coherent elastic neutrino-nucleus scattering. Furthermore, a new stage of cosmic microwave background experiments will afford probes of cosmic inflation, primordial gravitational waves, and novel dark sectors which have the ability to provide crucial insights into scenarios of grand unification, string theory, and extra dimensions.

All of which live at scales out of the reach of any future Earth-based collider.

Altogether, the unique laboratory of particle cosmology offers extraordinary possibilities for particle physics at all scales, allowing us to address the most profound questions we have about nature, such as the origin of matter and dark matter, the cosmological Hubble tension, the large separation of electroweak and Planck scales, as well as the origin and size of neutrino masses.

This Special Issue is open to contributions on all frontiers of particle cosmology in and beyond the standard models of both particle physics and cosmology. We are especially welcoming of new and groundbreaking ideas, formal and phenomenological considerations, as well as contributions aiding efforts in ongoing observations and experiments.

Dr. Paolo Maestro
Dr. Andreas Trautner
Dr. Toby Opferkuch
Guest Editors

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• gravitational waves
• black holes
• dark matter
• beyond the standard model
• cosmic neutrinos