| Summary: |
This project will develop new theoretical models for dark matter (DM) that involve multiple dark species, including both new elementary particles/fields and composite objects such as primordial black holes (PBHs).
This proposal has both a theoretical and an experimental motivation. Firstly, the puzzling coincidence between the dark and baryonic matter densities points towards some complexity in the dark sector, since baryons exhibit a matter/anti-matter asymmetry and their mass is mostly determined by non-perturbative effects in QCD. Secondly, the multitude of potential DM candidates in proposed extensions of the Standard Model (SM) of particle physics suggests that at least some of them may give contributions towards the total DM abundance in the cosmos. Also from the experimental side, the lack of evidence for the simplest "thermal WIMP" DM candidates in direct detection experiments, such as LUX or XENON, motivates considering alternative ways of producing DM through non-thermal mechanisms, which typically involve multiple interacting species.
Finally, the interplay between different DM components may potentiate new multi-messenger astrophysical signatures and possibly new ways to search for DM in the laboratory, as our team has already demonstrated in several scenarios.
The proposal is divided into two tasks that will be implemented in parallel by team members given the potential synergies between them.
The first task will be devoted to PBHs, both as a dominant and as a sub-dominant DM component. We aim to investigate, on the one hand, new scenarios for PBH formation in non-standard inflation scenarios, namely warm, thermal and multi-stage inflation. On the other hand, we aim to study the cosmological impact of particle production by PBHs, through both Hawking emission and rotational superradiance, in the genesis of
(sub-)dominant DM particles (including axions, hidden photons and also composite self-gravitating boson stars resul  |
Summary
This project will develop new theoretical models for dark matter (DM) that involve multiple dark species, including both new elementary particles/fields and composite objects such as primordial black holes (PBHs).
This proposal has both a theoretical and an experimental motivation. Firstly, the puzzling coincidence between the dark and baryonic matter densities points towards some complexity in the dark sector, since baryons exhibit a matter/anti-matter asymmetry and their mass is mostly determined by non-perturbative effects in QCD. Secondly, the multitude of potential DM candidates in proposed extensions of the Standard Model (SM) of particle physics suggests that at least some of them may give contributions towards the total DM abundance in the cosmos. Also from the experimental side, the lack of evidence for the simplest "thermal WIMP" DM candidates in direct detection experiments, such as LUX or XENON, motivates considering alternative ways of producing DM through non-thermal mechanisms, which typically involve multiple interacting species.
Finally, the interplay between different DM components may potentiate new multi-messenger astrophysical signatures and possibly new ways to search for DM in the laboratory, as our team has already demonstrated in several scenarios.
The proposal is divided into two tasks that will be implemented in parallel by team members given the potential synergies between them.
The first task will be devoted to PBHs, both as a dominant and as a sub-dominant DM component. We aim to investigate, on the one hand, new scenarios for PBH formation in non-standard inflation scenarios, namely warm, thermal and multi-stage inflation. On the other hand, we aim to study the cosmological impact of particle production by PBHs, through both Hawking emission and rotational superradiance, in the genesis of
(sub-)dominant DM particles (including axions, hidden photons and also composite self-gravitating boson stars resulting from superradiant instabilities), in reheating the Universe after inflation and also in generating a cosmological baryon asymmetry. We will also assess the potential of small evaporating PBHs to probe new physics beyond the SM, particularly in the context of the string axiverse.
The second task will focus on complex dark sectors with multiple particle species and dark gauge interactions, particularly those (partially) mirroring the SM. The PI of this proposal has recently shown that MSSM-like dark sectors can naturally explain the coincidence between dark and baryonic matter densities, even if particles in the dark sector are much heavier than known SM particles due to a larger supersymmetry breaking scale. We plan to investigate the cosmological evolution of heavy dark sectors, which may differ substantially from the "visible" SM sector from inflation to the present day, as well as dark structure formation (including dark compact objects) and feeble interactions between the visible and dark particles, namely dark photons and dark neutrinos, yielding novel detection strategies. We also aim to investigate the possible cosmological roles of dark scalar fields within these sectors, such as potentially driving inflation, the electroweak phase transition (e.g. through Higgs-dark Higgs interactions) or early matter-dominated epochs.
Our goal is not only to theoretically explore these novel aspects of multi-component DM scenarios, from their underlying (quantum) field theory description to their cosmological evolution and phenomenology, but also to find distinctive astrophysical signatures of these scenarios in different channels, including electromagnetic and gravitational radiation in all detectable frequencies, as well as neutrinos, cosmic rays and gravitational microlensing surveys (in the case of compact objects like PBHs). We will use available data from active/past telescopes/detectors (e.g. James Webb Telescope, Chandra, Planck, Fermi-LAT, LHAASO, HAWC, LIGO-Virgo-KAGRA, IceCube, Pierre Auger Observatory) to test and constrain our models, and produce forecasts for planned experiments such as SKAO, AMEGO, LISA, Einstein Telescope or KM3Net. We thus plan to take full advantage of the new opportunities offered by multi-messenger astronomy to test our novel approaches to the DM problem.
This proposal brings together a team of senior and early-career researchers from the universities of Coimbra and Porto, alongside some of their international collaborators, with the multi-disciplinary expertise in cosmology, (astro-)particle physics and gravitation required to achieve the proposed goals. This team has successfully collaborated in implementing the proposal "Exploring the darkest side of dark matter", the outcomes of which uncovered new research avenues that we aim to pursue in this innovative and ambitious proposal. |