Welcome

Risa Wechsler KIPAC director

Welcome to Risa Wechsler, who began her appointment as director of the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC). Our tremendous gratitude is due to Tom Abel, whose ably led KIPAC over the past five-years.

The Kavli Institute for Particle Astrophysics and Cosmology, or KIPAC, was inaugurated in 2003 as an independent laboratory of Stanford University to serve as a bridge between the disciplines of astrophysics, cosmology and particle physics. KIPAC's members work in the Physics and Applied Physics Departments on the Stanford campus and at the SLAC National Accelerator Laboratory. Its mission is to bring the resources of modern computational, experimental, observational and theoretical science to bear on our understanding of the universe at large.

Research Highlights

Dec 10, 2018 | The splashback radius— understanding the boundaries of dark matter halos

Simulated dark matter halo from a cosmological N-body simulation. (Credit: By http://en.wikipedia.org/wiki/User:Cosmo0 - English Wikipedia http://en.wikipedia.org/wiki/Image:Dark_matter_halo.png, Public Domain, https://commons.wikimedia.org/w/index.php?curid=4670264.)

Halos are the result of a long sequence of cosmic structure formation. We think it happened like this: The early Universe, after a very short period of rapid expansion called inflation, settled into its current phase of more leisurely general cosmic expansion (or “Hubble flow,” as cosmologists often call it). At the end of inflation, while the density of dark matter—on average—had been smoothed out to become very homogenous on large scales, small quantum perturbations were amplified to more significant density fluctuations—places where there was a tiny bit more, or less, matter. The knots of slightly higher density served as wells of gravitational potential and began to grow further with time by attracting ever more matter through gravity.

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