Michele Maggiore

A generalized uncertainty principle in quantum gravity

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 considerations we find a generalized uncertainty principle which agrees with a similar result obtained in the framework of string theories. The result indicates that a minimum length of the order of the Planck length emerges naturally from any quantum theory of gravity, and that the concept of black hole is not operationally defined if the mass is smaller than the Planck mass.

The algebraic structure of the generalized uncertainty principle

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 in quantum gravity. The deformed algebra and therefore the form of the generalized uncertainty principle are fixed uniquely by rather simple assumptions. The string theory result is reproduced expanding our result at first order in Δp/MPL. We also briefly comment on possible implications for Lorentz at the Planck scale.

Nonlocal gravity and dark energy

We study the cosmological consequences of a recently proposed nonlocal modification of general relativity, obtained by adding a term

THE HALO MASS FUNCTION FROM EXCURSION SET THEORY. II. THE DIFFUSING BARRIER

m^2R\,\Box^{-2}R

Gravitational waves from electroweak phase transitions

to the Einstein-Hilbert action. The model has the same number of parameters as

Nonlocal theory of massive gravity

\Lambda

Zero-point quantum fluctuations and dark energy

CDM, with

Cosmological dynamics and dark energy from nonlocal infrared modifications of gravity

m

Apparent ghosts and spurious degrees of freedom in non-local theories

replacing

Phantom dark energy from nonlocal infrared modifications of general relativity

\Omega_{\Lambda}