From B-Modes to Quantum Gravity and Unification of Forces∗

Lawrence M. Krauss
Department of Physics and School of Earth and Space Exploration,
Arizona State University,
PO BOX 871404 Tempe, AZ 85287-1404, USA
and
Mount Stromlo Observatory,
Research School of Astronomy and Astrophysics,
Australian National University,
Weston, ACT, Australia, 2611)y
Frank Wilczek
Department of Physics, MIT, Cambridge MA 02139z
(Dated: March 31, 2014)

It is commonly anticipated that gravity is subject to the standard principles of quantum mechan-
ics. Yet some { including Einstein { have questioned that presumption, whose empirical basis is
weak. Indeed, recently Freeman Dyson has emphasized that no conventional experiment is capable
of detecting individual gravitons. However, as we describe, if in
ation occurred, the Universe, by
acting as an ideal graviton ampli er, a ords such access. It produces a classical signal, in the form
of macroscopic gravitational waves, in response to spontaneous (not induced) emission of gravitons.
Thus recent BICEP2 observations of polarization in the cosmic microwave background will, if con-
rmed, provide rm empirical evidence for the quantization of gravity. Their details also support
quantitative ideas concerning the uni cation of strong, electromagnetic, and weak forces, and of all
these with gravity.