Physics of the Early Universe
Observations of the CMB anisotropy provide more than a snap shot of the matter
and energy distribution at about 300,000 years after the initial Big Bang.
This snap shot is useful not only because it provides the initial conditions
Origin of Large Scale Structure
but also because it provides information about the processes that produce
these "seeds" of large scale structure.
Probe of Inflation and/or Quantum Gravity
In the Big Bang model the Universe has a finite age and that the further
away in distance and thus the further back in time one observes,
the more and more various regions of the Univerese are isolated
from each other by causality.
This is referred to as the
since regions separated by distances greater than light can travel
in the time since the start of the Big Bang are not causally connected and
therefore cannot be synchronized.
It is thus difficult to explain the overall uniformity and homogeneity
of the Universe and the existence of the very large scale structures
(ripples in the fabric of space-time) discovered by COBE.
At present the concept of inflation
is the only mechanism that we have
that provides a means to explain this phenomen.
It is possible that some form of Quantum Gravity with quantum tunneling
in the very early epoch or related mechanism that leads to the accelerating
formation of space-time will be found to overcome the standard causality limit.
Test of Cosmological Defects
It is thought that at very early times the fundamental forces were unified.
As the Universe expanded and cooled a series of phase changes
(such as steam to water, water to ice)
occurred and the forces spontaneously lost their symmetry.
Due to the same horizon problem issue of causal connectedness,
such a spontaneous symmetry breaking cannot be coordinated in widely separated
regions thoughout the Universe.
As a result there are topological defects generated.
These defects have "dimensions" set by the order of the symmetry that is broken:
monopoles, strings, domain walls, textures are examples in order of increasing dimension.
At the moment essentially all classes of defects, except domain walls, have champions
advocating that they exist from the GUT (Grand Unified Theory) scale (10^16 GeV) and
are the seeds of large scale structure formation and account for the observered
CMB anisotropies. They do predict a significantly different CMB anisotropy pattern
and power spectrum than do the adiabatic perturbations predicted from inflation models.
Measurement of the Cosmological Constant
Probe of the Nature of Dark Matter
Probe of the Baryonic Content of the Universe
Return to the Science Goals Page
On the Smoot Group page
you can read about the experiments and observations of the CMB such as the
COBE satellite and its instruments, the MAX/MAXIMA/BOOMERANG
balloon-borne instrument, and the Planck satellite (now approved
by the European Space Agency).
Revised 29 May 1996; email@example.com