Cosmology

Working from the standard model of the "Big Bang" some 14 billion years ago, we are investigating the early epoch of inflation and the nature and role of dark matter in the evolution of structure in the Universe. We also seek to understand the nature and properties of the "dark energy" that is speeding up the expansion of the Universe.

Extragalactic Surveys

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Bootes

Viewed in X-rays the night sky glows brightly and uniformly in all directions. The origin of this 'cosmic X-ray background' was one of two great puzzles set by the very first observations of X-rays from beyond the Solar System by Riccardo Giacconi and his team back in 1963. (For which Giacconi won the Nobel Prize in Physics in 2002 (see:Riccardo Giacconi .) To solve the puzzle required sensitive X-ray telescopes, culminating in the Chandra X-ray Observatory .

Baryon Acoustic Oscillations

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In the first million years after the Big Bang, the cosmic plasma rings with sound waves excited by the initial inflationary(?) perturbations. The radiation pressure from the cosmic microwave background keeps the ionized gas from clustering; this pressure leads to relativistic sound waves that propagate until the Universe becomes neutral at redshift 1000. These sound waves lead to the dramatic acoustic oscillations seen in cosmic microwave background anisotropy data, but they also leave a faint imprint in the clustering of galaxies and matter today.

Large Scale Structure

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Up until the latter part of the 20th Century astronomers thought, in the words of the eminent astronomer Edwin Hubble, that the universe was "sensibly uniform." As a result of redshift surveys of large samples of galaxies we now know that the galaxies around us are distributed in an incredible tapestry of filamentary and sheet-like structures called the cosmic web. Massive clusters of galaxies lie at major "intersections" in this web. Galaxies like our own Milky Way are usually found in groups which often lie on the outskirts of clusters or superclusters.

The Accelerating Universe

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The last decade has undergone a renaissance in our knowledge of the values of the basic cosmological parameters. Three new measurements combine to give a new picture of the Universe. In 1998, Adam Riess and Brian Schmidt using Type Ia supernovae measured the first indication of an accelerating expansion of the Universe (Riess 1998), the dark energy which creates the acceleration is 74% of the contents of the Universe.

21cm Cosmology

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reionization in 21cm radiation generated from a simulation (

From the time the Universe was just four-hundred thousand years old to when it was one-billion years old, most of its hydrogen was neutral. Neutral hydrogen produces 21cm radiation, and the amount of information in this signal dwarfs that of all other cosmological probes. TA scientists are part of the team which is operating the Mileura Widefield Array (MWA), a large radio interferometer being built in Western Australia to observe this signal.

Fundamental Symmetries

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Hydrogen Maser Lab

AMP research on atomic clocks and quantum optics includes precise tests of fundamental symmetries of physics (Lorentz invariance) linked to questions about the origin and fate of the universe. In particular, these measurements can be used to test the standard models of physics, with profound implications for cosmology.

Early Universe

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structures in the early universe

Within a second or two after the Big Bang, protons and neutrons start to combine into atomic nuclei (hydrogen, helium, and traces of lithium, beryllium, and boron). Roughly 300,000 years later, the Universe became cold enough for electrons to combine with atomic nuclei and form atoms.

Large-Scale Structure Formation

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simulation of the dark matter structure

Very small quantum fluctuations in the first 10^-30th of a second in the universe seeded small density inhomogeneities. These inhomogeneities grew with time, eventually becoming the galaxies, clusters of galaxies, and super-clusters that are observed in the local universe.

Dark Energy & Dark Matter

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LSST Telescope

Ninety-five percent of the energy in the universe is of unknown origin, and is classified as either "dark energy" or "dark matter". Dark energy is a mysterious repulsive energy that is accelerating the expansion of the Universe, and its mere existence is considered the biggest outstanding problem in all of theoretical physics.

Gravitational Lensing

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The gravitational lens system PG1115+080

The phenomenon at the root of gravitational lensing is the deflection of light by gravitational fields predicted by Einstein's general relativity, in the weak-field limit. The deflection has well-known observable effects, such as multiple images, magnification of images, and time delays for propagation of light along the paths forming different images.

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