Axions and axion-like particles are well-motivated dark matter candidates whose relic abundance is often attributed to the standard misalignment mechanism. After briefly reviewing the conventional picture, I will discuss several non-minimal realizations of axion dark matter, including trapped misalignment, bubble misalignment, and level crossing in multi-axion systems, which can qualitatively...
Gamma ray data from distant sources shows evidence of gamma ray
cascades initiated by cosmic rays. Furthermore, the neutrinos observed
from NGC 1068 can be explained by the effects of cosmic-ray nuclei. I will
discuss these multimessenger connections and their implications for models
of blazars, high-energy cosmic rays, and intergalactic magnetic fields.
Changes in the shape of the spectrum of cosmic rays, such as the "knee" in the 2-5 PeV range, have long been a clue to questions of their origin and propagation. For this energy regime, we will discuss experiments now exploring not only the cosmic ray energy spectrum, but also the particles' nuclear composition and potential multimessenger associations.
The LUX-ZEPLIN (LZ) dark matter search experiment, a dual-phase xenon time projection chamber operating at the Sanford Underground Research Facility in Lead, South Dakota, USA, has demonstrated the world's leading sensitivity to searches for Weakly Interacting Massive Particles (WIMPs). It comprises 7 tonnes of liquid xenon as an active target viewed by photomultiplier tubes (PMTs), xenon Skin...
The Einstein Probe (EP) is a space X-ray observatory designed to detect mainly high-energy transient and variable sources in the universe. It features a lobster-eye wide-field X-ray monitor with unprecedented sensitivity and spatial resolution in the soft X-ray band, and a conventional X-ray telescope to perform quick onboard follow-up observations. EP is a project led by the Chinese Academy...
The SVOM mission is a French-Chinese cooperation successfully launched in June 2024. The SVOM multi-wavelength space payload is composed by two wide field gamma-ray instruments (ECLAIRs and GRM), and two narrow field instruments, MXT and VT, operating in the X-ray and visible domains.
The space segment is complemented by dedicated robotic telescopes operated from China and Mexico.
In this...
Imaging Atmospheric Cherenkov Telescopes (IACTs) have opened a new window on the very-high-energy gamma-ray sky, delivering unprecedented sensitivity at the lowest energies accessible from the ground. While these instruments are primarily designed for astrophysical studies, they also provide a powerful — yet still underutilized — laboratory for fundamental physics.
In this contribution, I...
Ten years after their first direct detection, the catalog of gravitational-wave sources has grown to over 300 candidate events, including all possible combinations of merging black holes and neutron stars. New data from the fourth observing run (O4) of the LIGO-Virgo-KAGRA detectors have revealed events containing black holes at both extremes of the mass distribution, events of likely...
Core-collapse supernovae (CCSNe) are promising multi-messenger sources, potentially emitting neutrinos and electromagnetic radiation across a wide range of timescales and energies. For very extended stellar envelopes, relativistic jets launched in the explosion may fail to escape the progenitor star, forming so-called choked jets. While these systems are invisible in gamma rays, they can be...
Observations in the MeV gamma-ray band provide enormous potential for obtaining fundamental results on topics ranging from nucleosynthesis via studies of nuclear emission lines to multimessenger astrophysics (MMA) through detections of gamma-ray bursts (GRBs) and other transients. Due to the challenges of operating in the MeV band (~0.1-100 MeV), it is one of the least explored regions of the...
Active galactic nuclei (AGN) are among the most powerful persistent sources of high-energy electromagnetic radiation in the Universe. The combination of large energy reservoirs, dense radiation fields and ionized plasma in AGN coronae, and relativistic plasma flows in AGN jets makes these systems prime candidates for the production of high-energy neutrinos. Indeed, most of the astrophysical...
Photons, gravitational waves, neutrinos and cosmic rays carry complementary information about individual cosmic sources and their populations, offering an exceptionally powerful tool for probing the properties of the Universe. In the extreme energy regime, above $10^{17}$ eV, the Pierre Auger Observatory plays a leading role in multimessenger astronomy, owing to its capability to discriminate...
Cosmic rays and neutrinos provide access to particle interactions at energies and densities beyond the reach of terrestrial experiments. Combined with gamma rays, they offer a multimessenger view of extreme astrophysical environments and a window onto relics from the early Universe. Here I will discuss how these messengers can be used to search for new physics, with emphasis on the cosmic...
High-energy neutrinos have become a quantitative probe of non-thermal processes in the universe. Over the past decade, cubic-kilometer scale detectors have established a diffuse astrophysical neutrino flux from the TeV to PeV range and identified candidate events reaching the PeV–EeV energies. Recent highlights include the first >5σ discovery of Galactic neutrino emission, indications of...
The Large High Altitude Air Shower Observatory (LHAASO) has ushered in a new era of ultra-high-energy (UHE, typically above 100 TeV) gamma-ray astronomy, providing unprecedented insights into the most powerful particle accelerators in the Milky Way. In this talk, I will review recent progress in the identification and characterization of Galactic PeVatron candidates, highlighting LHAASO’s...
The WIMP paradigm, in which dark matter particles are assumed to interact with the Standard Model and to have been thermalized in the early universe, remains one of the most compelling scenarios. It provides robust and testable predictions across a variety of interaction channels. Driven by significant experimental advances in both direct and indirect detection, increasingly precise...
Ultra-high-energy cosmic rays (UHECRs) are the most energetic particles known - and yet their origin is still an open question. However, with the precision and accumulated statistics of the Pierre Auger Observatory and the Telescope Array, in combination with advancements in theory and modeling - especially of the Galactic magnetic field - it is now possible to set solid constraints on the...
Recent observations in the ultrahigh-energy (UHE) gamma-ray band have revealed an abundance of source populations in our Galaxy that operate as efficient particle accelerators. These sources include microquasars, pulsar wind nebulae, young star clusters, and supernova remnants. Although not yet fully understood, the spectra, morphologies, and temporal variabilities of these sources carry...
The origin of Galactic cosmic rays (CRs) above the PeV scale, particularly around the knee of the all-particle spectrum, remains a fundamental open question in high-energy astrophysics. Recent developments of air shower arrays, such as Tibet AS$\gamma$, HAWC, and LHAASO, opened up a new era by detecting ultra-high-energy (UHE; E>100 TeV) gamma rays. These UHE sources are possible candidates of...
