In the ΛCDM cosmological model the Universe is assumed to be isotropic and homogeneous when averaged on large scales. That the Cosmic Microwave Background 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 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.

Gravitational wave (GW) observations have opened new avenues for probing Beyond Standard Model (BSM) physics. While most detections involve typical black hole (BH) or neutron star (NS) mergers, events like GW190814, GW190425, and GW230529 observed by the LIGO-Virgo-KAGRA (LVK) collaboration include at least one compact object whose nature—either a binary neutron star (BNS) or a low-mass black hole (LMBH)—remains uncertain. One possible formation channel for such LMBHs involves dark matter (DM) capture and accumulation in NSs, leading to a collapse-induced transmutation of the NS into a BH of comparable mass. I will discuss how DM capture in NSs can lead to the formation of LMBHs, highlighting the relevant parameter space that governs this process. I will also show how current GW observations can constrain portions of this DM parameter space. In the second part, I will focus on the gravitational waveforms of BNS mergers versus LMBH mergers, examining their distinguishing features and assessing the capability of current and future detectors to differentiate between these two scenarios.

The quest to probe the Standard Model more deeply and to search for physics beyond its current limits continues to drive the development of future particle colliders. Numerous ambitious proposals, both linear and circular designs, and lepton and hadron colliders, aim to push the frontiers of energy and luminosity to unprecedented levels. This seminar will present an overview of the main collider concepts, examining their scientific motivations, design strategies, and individual strengths. In addition, the technological challenges these proposed machines face will be discussed, along with potential synergies and complementarities among the different proposals.