The exploration of the universe has recently entered a new era thanks to the multi-
messenger paradigm, characterized by a continuous increase in the quantity and quality of …

The existence of a fundamental scale, a lower bound to any output of a position
measurement, seems to be a model-independent feature of quantum gravity. In fact, different …

Quantum gravity poses the problem of merging quantum mechanics and general relativity,
the two great conceptual revolutions in the physics of the twentieth century. The loop and …

We can no longer speak of the behaviour of the particle independently of the process of
observation. As a final consequence, the natural laws formulated mathematically in quantum …

The goal of this review is to present an introduction to loop quantum gravity—a background-
independent, non-perturbative approach to the problem of unification of general relativity …

We study the operator that corresponds to the measurement of volume, in non-perturbative
quantum gravity, and we compute its spectrum. The operator is constructed in the loop …

A stochastic background of gravitational waves could be created by the superposition of a
large number of independent sources. The physical processes occurring at the earliest …

The problem of describing the quantum behavior of gravity, and thus understanding
quantum spacetime, is still open. Loop quantum gravity is a well-developed approach to this …

We study light propagation in the picture of semiclassical space-time that emerges in
canonical quantum gravity in the loop representation. In such a picture, where space-time …

A new functional calculus, developed recently for a fully non-perturbative treatment of
quantum gravity, is used to begin a systematic construction of a quantum theory of geometry …