The Quantum Structure of Space and Time (293 pages)

246 The Quantum Structure of Space and Time

6.3.2 Renata Kallosh: Inflationary models as a test of string the-

ory

Our Universe is an Ultimate Test of the Fundamental Physics. High-energy ac-
celerators will probe the scale of energies way below GUT scales. Cosmology and
astrophysics are the only known sources of data in the gravitational sector of the
fundamental physics (above GUT, near Planck scale). After the supernovae obser-

Early Universe Inflation Late-time Acceleration

Near de Sitter space Near de Sitter space

13.7 billion years ago Now

During sec During few billion years

v - H~M; v - H~M;

0, a(t) - eHt

vations and particularly after the release of the 1st year WMAP data on CMB in

2003 it become clear that any fundamental theory which includes gravity as well as

particle physics has to address these data. The theory is expected to explain the
origin of the near de Sitter space both during inflation as well as during the cur-
rent acceleration. The most recent new observations from the Boomerang [l] are in
agreement with the so-called standard cosmological model supported by the first set

of WMAP data. This is ACDM model, in which the universe is spatially flat, it has

a mysterious combination of matter we know it (- 5%), cold dark matter (- 25%)

and dark energy (- 70%). The model is using just few parameters to explain the

large amount of cosmological observations. These parameters are suggested by the

inflationary cosmology [2] which plays a significant role in ACDM standard model.

The model also incorporates the current acceleration of the universe, see Table I.

String theory is the best candidate for the unified theory of all fundamental

interactions. It has been realized over the last few years that the long standing dif-

ficulties in explaining cosmological observations may be resolved due to the current

progress in string theory.