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3D map of the large-scale distribution of dark matter, recon-structed from measurements of weak gravitational lensing with the Hubble Space Telescope. Credit: NASA/ESA/Richard Massey (California Institute of Technology)

Dept of Physics & AstronomyUniversity of Utah

201 James Fletcher Bldg.115 South 1400 East

Salt Lake City, UT 84112-0830(801) 581-6901

www.physics.utah.eduwww.astro.utah.edu

Theoretical High Energy

Physics &Astrophysics

Dark MatterAbout 96% of the Universe is not made of any substance we have found in nature. Part of this mysterious stuff (the dark matter) concentrates around galaxies; the other part (the dark energy) smoothly pervades the whole Universe. Scientists have only ideas and speculations about the nature and origin of the “dark sector”.

Astrophysicists at the University of Utah are devising ways to figure out their na-ture. We compare theories of dark matter particles with data from experiments that seek to detect them in the laboratory or through rare cosmic particles or at par-ticle accelerators like the Large Hadron Collider. We use Hubble Space Telescope images to search for the gravitational pull of concentrated dark matter objects dis-torting light from far away stars. We study how particle dark matter affects black holes and stars, leading for example to exotic objects like “dark stars’’ powered by dark matter instead of nuclear fusion.

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The Early Universe...

High-energy physicists investigate the most fundamen-tal elements and interactions in nature. Astrophysicists study celestial bodies such as stars and galaxies by observing their light emissions and particles. These two fields operate on very different scales: one deals with subatomic particles, the other with the Universe at large. Yet they intertwine when addressing some of our most profound scientific questions:

• What is the origin & fate of the universe? • How was the universe created? • Are there other planets in the universe that support life? • What exactly is “dark matter” & how does it influence the formation, rotation, & evolution of galaxies? • What is the nature of the dark energy that drives the accelerating expansion of the universe?

Researchers at the University of Utah’s Department of Physics & Astronomy are carrying out large-scale computer calculations to recreate the conditions of the quark-gluon plasma. We are able to study the formation of protons and neutrons as the Universe cooled. Such information is vital to our understanding of how the Universe came into being.

Holography, Quantum Gravity & The Origin of

Dark EnergyRecent observations tell us our Universe is not only expanding, but the expansion is accelerat-ing, as though from a gravitationally repulsive source called “dark energy”. It makes up about 70% of the total mass/energy of our present Universe. Its origin is one of the greatest scien-tific mysteries today. String theory, a possible unification of gravity and quantum theory, may help us understand it.

Astrophysicists at the University of Utah are studying a novel idea in string theory called holography. This sophisticated idea is not yet fully understood. However, it may hold the key to better understanding string theory, which in turn could lead to a profound change in the way we look at the universe, including a real understanding of the origin of dark energy and perhaps the state of the very early universe as well.

Planet FormationAs the Universe cooled, eventually galaxies and stars formed, and later life arose. Astrophysicists at the University of Utah are performing computer simulations to determine how common or rare Earth-like planets are around neighboring stars. Preliminary work shows that the formation of Earth-like planets at life-sup-porting distances from their host star is highly likely under a wide range of circumstances. However, observation now tells us that large Jupiter-like planets tend to migrate closer to their host stars. In so doing, they may have disrupted the orbits of smaller, possibly habitable planets. To answer the burning question of whether life exists elsewhere in the universe, we need to know the details. In our own solar system, the migration of Jupiter, Sat-urn, Uranus, and Neptune may not have affected the Earth’s orbit, but could have moved distant icy comets to deliver life-giving water here on our home planet.

Present observations suggest that the Universe began from an extremely hot and dense concentration of matter that expand-ed and then cooled. Conditions in the early Universe were very different from today. There were no galaxies, no stars, no planets, and no elements, not even nuclei as we know them. Quarks, antiquarks, and gluons moved in a massive plasma. These condi-tions do not occur naturally today, except possibly in the cores of very dense stars, but we can try to recreate them in a microcosm through experiments and computer calculations.

To learn more about the High Energy Astrophysics program, visit:

www.physics.utah.edu