Motivated by conceptual problems in quantum theories of gravity, the gravitational eikonal
approach, inspired by its electromagnetic predecessor, has been successfully applied to the …

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 …

Strings may be explored, through a scattering process at planckian energies, down to
distances of the order of the string size. We show that this is possible if the energy is not so …

The high-energy behavior of string scattering amplitudes is studied to all orders in
perturbation theory, with the aim of exploring the short-distance structure of string theory. It is …

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 …

We discuss a Gedanken experiment for the measurement of the area of the apparent
horizon of a black hole in quantum gravity. Using rather general and model-independent …

We review versions of the Generalized Uncertainty Principle (GUP) obtained in string theory
and in gedanken experiments carried out in quantum gravity. We show how a GUP can be …

A possible definition of path integrals for string theory is studied, based on a discretized
version of Polyakov's generating functional. The finite resolution of string theory, as opposed …

According to a number of arguments in quantum gravity, both model-dependent and model-
independent, Heisenberg's uncertainty principle is modified when approaching the Planck …

We show that a deformation of the Heisenberg algebra which depends on a dimensionful
parameter κ is the algebraic structure which underlies the generalized uncertainty principle …