Loop quantum gravity: the first twenty five years

This is a review paper invited by the journal "Classical ad Quantum Gravity" for a "Cluster Issue" on approaches to quantum gravity. I give a synthetic presentation of loop gravity. I spell-out the aims of the theory and compare the results obtained with the initial hopes that motivated the early interest in this research direction. I give my own perspective on the status of the program and attempt of a critical evaluation of its successes and limits.Comment: 24 pages, 3 figure

Generalized Uncertainty Principle and Self-dual Black Holes

The Generalized Uncertainty Principle suggests corrections to the Uncertainty Principle as the energy increases towards the Planck value. It provides a natural transition between the expressions for the Compton wavelength below the Planck mass and the black hole event horizon size above this mass. It also suggests corrections to the the event horizon size as the black hole mass falls towards the Planck value, leading to the concept of a Generalized Event Horizon. Extrapolating below the Planck mass suggests the existence of a new class of black holes, whose size is of order the Compton wavelength for their mass. Such sub-Planckian black holes have recently been discovered in the context of loop quantum gravity and it is possible that this applies more generally. This suggests an intriguing connection between black holes, the Uncertainty Principle and quantum gravity