For the first time, astronomers have probed the physical environment of repeating X-ray outbursts near monster black holes thanks to data from NASA’s NICER (Neutron star Interior Composition Explorer) and other missions.

Satellite communication is an indispensable part of sixth generation of mobile communication systems (6G) given its global coverage and long-distance propagation. Energy consumption and channel acquisition are two critical issues in satellite communication systems. On the one hand, with the rapidly increasing energy wastage in wireless systems, green communication technology has attracted extensive attentions and energy efficiency (EE) becomes the key performance indicator in the transmission scheme design of satellite communications. On the other hand, channel state information (CSI) is well required in designing the beamforming, but it is infeasible for gateway (GW) to acquire accurate CSI at the transmitter (CSIT) due to the long-distance delay. Most of the existing work focused on maximizing the total EE (TEE) or minimum EE (MEE) while tradeoff between TEE and MEE has not been investigated in the satellite communication systems. However, it is of both great theoretical and practical significance for satellite systems to investigate the tradeoff between the TEE and MEE so as to balance the total system performance and the fairness in terms of EE.

Ever since general relativity pointed to the existence of black holes, the scientific community has been wary of one peculiar feature: the singularity at the center — a point, hidden behind the event horizon, where the laws of physics that govern the rest of the universe appear to break down completely. For some time now, researchers have been working on alternative models that are free of singularities. A new paper published in the Journal of Cosmology and Astroparticle Physics (JCAP), the outcome of work carried out at the Institute for Fundamental Physics of the Universe (IFPU) in Trieste, reviews the state of the art in this area. It describes two alternative models, proposes observational tests, and explores how this line of research could also contribute to the development of a theory of quantum gravity.