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RESEARCH
COSMOLOGY AND GRAVITATION
Physicists at Perimeter combine recent
developments at the interface of fundamental physics
and astrophysics to shed light on some of the major puzzles
in the field: What is causing the observed cosmic acceleration?
What is the nature of dark matter? What can be learned from the
microwave background and large-scale structure observations about
theories of fundamental physics? Is inflation the correct paradigm of early-
universe cosmology? What drives some of the most energetic events
in nature? What happens in the vicinity of black holes, and how do they
behave in more than three dimensions?
IS
THE
CONVENTIONAL
PICTURE
OF
THE
EARLY
UNIVERSE
CORRECT
?
At the centre of modern cosmology is the theory of cosmological inflation – the idea that the early
universe experienced a brief burst of accelerated expansion. Recently, Faculty member Latham
Boyle and Distinguished Research Chair (DRC) Paul Steinhardt proposed an observational
test that could confirm this theory beyond a reasonable doubt.
The test involves the Cosmic Microwave Background (CMB), ancient radiation that permeates
every corner of the cosmos. It was generated when the universe was a mere few hundred
thousand years old. Cosmologists can infer detailed information about the first instants after
the Big Bang by studying variations in the CMB. If inflation is correct, the universe would have
“stretched” by an enormous factor during the early burst of expansion, and then “unstretched” by
precisely the same factor during the billions of years since. Forthcoming CMB observations will
yield independent estimates for both the “stretch” and “unstretch” factors. Boyle and Steinhardt
argue that if these estimates match one another, it will amount to persuasive evidence that the
theory of inflation is really on the right track.
WHAT
HAPPENS
WHEN
SINGULARITIES
ARE
NOT
HIDDEN
BEHIND
BLACK
HOLES
?
What happens inside a black hole stays inside a black hole. Or so one might hope.
A hypothesis called “cosmic censorship” addresses the question of how the extreme conditions
within a black hole can exist in a universe whose physical laws they seem to defy.
A black hole contains a “singularity” – a region with energy density so high, it tears up spacetime
itself and Einstein’s equations cease to be valid. The effects of such singularities would be felt
across the universe, were they not hidden inside black holes. Black holes “censor” singularities,
enabling outside observers to do meaningful physics without having to deal with the chaotic
effects within.