Loop Quantum Cosmology

In the last decades, cosmology has developed into a mature science, reaching outstanding observational achievements and making accessible energy scales where the gravitational interaction had never been tested before. Moreover, the recent success in the detection of gravitational waves and the possibility to combine this probe of the cosmos with other astronomical techniques in what is now called multimessenger astrophysics has opened a new window to observe the Universe, offering novel opportunities to investigate gravity in strong regimes and relativistic scenarios. This observational revolution in cosmology and astrophysics has inspired an increasing number of theoretical works that, starting with solid candidate theories for the quantization of gravity, attempt to extract predictions that could ultimately be falsified observationally. Among these top-down approaches, a prominent role is played by Loop Quantum Cosmology, an area of research born from the application of the nonperturbative formalism of Loop Quantum Gravity to cosmological systems.

Loop Quantum Cosmology has provided notable results such as the cure of cosmological singularities by means of a big bounce mechanism that avoids the collapse, has proven capable to solve tensions between the predic-tions from General Relativity and the observations on the Cosmic Microwave Background at large scales within standard inflation, and has shown how quantum phenomena can change our image of classical spacetimes. This special issue aims to address the new exciting developments, proposals, and ideas that are blooming at present in Loop Quantum Cosmology, exploring among other topics the physical consequences in the Very Early Uni-verse, the possible traces left in cosmological observations, the quantum effects that may affect the generation and propagation of gravitational radiation, or the modifications in our view of the formation and fate of black holes.

This Research Topic is open to reviews and research articles in Loop Quantum Cosmology, or related areas of scientific activity in Loop Quantum Gravity and other nonperturbative proposals to quantize the gravitational interaction. Within this framework, the contributions are expected to address problems that cover theoretical, observational, or phenomenological aspects of the following topics:

• Applications and new advances in Quantum Cosmology.
• Formalisms, foundations, and recent progress in Quantum Gravity.
• Quantum black holes.
• Quantum effects in the Very Early Universe.
• Quantum Field Theory in curved cosmological backgrounds.
• Cosmological perturbations in quantum spacetimes.
• Singularity avoidance.
• Bouncing mechanisms in Quantum Cosmology.
• Quantum effects on gravitational waves.
• Predictions from Quantum Gravity.