Talks & Events
KICP Colloquia: 2014
Dark Energy Survey: Early Results
The expansion of the universe is accelerating, a discovery that earned the 2011 Nobel Prize in physics. Is cosmic acceleration due to "dark energy," or do we need to modify Einstein's General Relativity? If it is a new form of energy, is it constant or changing in time? Addressing these questions is the primary goal of the Dark Energy Survey (DES). After achieving first light in 2012, followed by months of commissioning and science verification, DES has just completed its first season of science observations at the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile. The DES Collaboration built a new 570-megapixel digital imager, the Dark Energy Camera (DECam), to carry out a deep, wide survey over the course of five (5) years---observing thousands of Type-Ia supernovae and hundreds of millions of galaxies. The thick, red-sensitive imager will allow us to see more supernovae and galaxies at higher redshift than previous surveys, like the Sloan Digital Sky Survey (SDSS). These observations will provide a suite of cosmological signatures: the Supernova Hubble diagram, galaxy cluster number counts, large-scale galaxy clustering and weak gravitational lensing. With this data, we will probe both the cosmic expansion history and the growth of large-scale structures, and thus explore the nature of dark energy. I will discuss the motivation for DES, the first years of operation and early results.
News from the Extreme Energy Cliff
Thanks to giant extensive air-showers observatories, such as the Pierre Auger Observatory and the Telescope Array, we now know that the sources of ultrahigh energy cosmic rays (UHECRs) are extragalactic. We also know that either they interact with the CMB as predicted or they run out of energy at the same energy scale of the CMB interactions! Their composition is either surprising (dominated by heavier nuclei at the highest energies) or the hadronic interactions at 100 TeV are not a standard extrapolation of LHC interaction energies. Hints of anisotropies begin to appear as energies reach 60 EeV, just when statistics become very limited.
Basic questions remain unanswered: What generates such extremely energetic particles that reach above 10^20 eV (100 EeV)? Where do they come from? How do they reach these energies? What are they? How do they interact on their way to Earth and with the Earth's atmosphere?
To answer these questions larger statistics at the highest energies is necessary. Space-based observatories can significantly improve the exposure to these extremely energetic particles. The first step to answer these questions is to place a wide field UV telescope at the International State Station to monitor the Earth's atmosphere from above. This is the goal of the JEM-EUSO mission: the Extreme Universe Space Observatory (EUSO) at the Japanese Experiment Module (JEM).
Taking the Measure of Dark Energy with DESI
Exciting results from BICEP2
A Tale of Two Collaborations: A New Precise Measurement of Cosmological Parameters Using Type Ia Supernovae
Do WIMPs Rule? The LUX Experiment and the Search for Cosmic Dark Matter
The search for dark matter in the form of Weakly Interacting Massive Particles, or WIMPs, has been ongoing for nearly thirty years. Steady progress has been made through the development and use of novel particle detectors aimed at low energy threshold and low radioactive backgrounds. After touching on the cosmological and astrophysical underpinnings, I will discuss the experimental challenges in searching for WIMPs and how we are attempting to meet them with the LUX experiment. LUX, the Large Underground Xenon experiment, is a time projection chamber that uses 250 kg of liquified xenon as a WIMP target. The detector is housed in the Sanford Underground Research Facility at the former Homestake goldmine in South Dakota. I will report on the first science run, which was completed in 2013, as well as upcoming plans. I will also describe the proposed follow-up LZ experiment, to be carried out by a merger of the LUX and Zeplin-3 collaborations.
Searches for Particle Dark Matter
Dark Matter is all around us, a clear sign of physics beyond the Standard Model, and yet we will have not understood what it is and how it fits into the larger picture. In this talk, I will discuss what we know about dark matter and how different kinds of searches, including searches for its collision with heavy nuclei, production at accelerators, and signs of its annihilation in our galaxy, combine together to give us information about how it (doesn't) interact with ordinary matter. The picture that will emerge is one where different searches complement each other, offering rich opportunities to understand the nature of dark matter in the near future.
The GeV Excess in the Inner Galaxy: Pulsars or Dark Matter?
Lessons from two success stories
Our present understanding of Nature is based on the Concordance Model of gravity and cosmology and on the Standard Model for the constituents of matter and their non-gravitational interactions. Their amazing successes --and puzzles-- may carry some important lessons for our quest of a truly unified theory of space, time, and matter.
Gravitational wave astrophysics with LIGO
Gravitational waves were first predicted by Einstein almost a century ago, and the Laser Interferometer Gravitational wave Observatory (LIGO) should be finally on the verge of directly detecting these waves. The most likely sources are the inspirals and mergers of stellar mass binary systems, such as pairs of neutron stars and/or black holes. In addition to being extraordinarily loud in gravitational waves, these coalescences may be associated with short gamma-ray bursts, and thus hold out the promise of multi-messenger astronomy: combining gravitational wave and electromagnetic observations to elucidate the physics and astrophysics of the sources. We present estimates for the event rate of binary systems, showing that LIGO can expect the first detections within months of operation. We examine the sky localization of LIGO sources, and explore some of the results that can be expected from gravitational wave astronomy, including shedding light on the process of black hole formation and precision measurements of the Hubble constant. We also discuss the loudest gravitational wave sources, and the potential to use these for internal calibration as well as for science. The era of gravitational-wave astronomy is rapidly approaching; a revolutionary new probe of our Universe awaits.
Cosmological Imprints of Dark Matter Produced During Inflation
Dark matter produced during inflation can naturally leave observable isocurvature imprints in the inhomogeneities of our universe. I survey the progress in theoretically cataloging such imprints, along with their connections with high energy theory and observations.
Two milestones in the history of the Universe: last scattering surface and black body photosphere of the Universe
The Fermi Gamma-Ray Space Telescope: An Update
The Fermi Gamma-Ray Space Telescope was launched in 2008. After 6 years in orbit, Fermi continues to bring new insights into the sources of high-energy radiation in the Galaxy and beyond. In this talk, I will describe upgrades to the science performance of Fermi (aka Pass 8) and highlights of recent discoveries.
Do WIMPs Rule? The LUX & LZ Experiments and the Search for Cosmic Dark Matter
Dark Matter remains a profound mystery at the intersection of particle physics, astrophysics, and cosmology. One of the leading candidates, the Weakly Interacting Massive Particle, or WIMP, may be detectable using terrestrial particle detectors. Recent technological advances are enabling very rapid increases in sensitivity in the search for these particles. I will talk about the LUX experiment, a liquid xenon time projection chamber, which currently holds the best upper limit over much of the mass range. I will also discuss plans for a larger follow up experiment, LZ, which will just begin to measure a background neutrino signal that will set a fundamental limit our ability to search for WIMP dark matter.