EFI Colloquia
A monthly series of presentations on topics of interest to the Institute. Talks are typically held the first Monday of the month in the LASR Conference Room 162 (933 E. 56th St., Room 162), Mondays at 4:15pm. Cookies, coffee and tea will be available starting at 4pm.
Next Colloquium:
"A Celebration of Roger Hildebrand"
Speakers: James Cronin, Tom Fields, John Boyer, Giles Novak, and Stan Whitcomb
Date/Time: 4:15 pm, Monday, May 7, 2012
Location: Kersten Auditorium, KPTC 106
Cookies and Coffee will be served in KPTC 206 at 4pm
Abstract: Come help us celebrate our beloved colleague Roger Hildebrand as he celebrates his 90th birthday! Our speakers will highlight Roger's many achievements -- his science, his mentorship, and service to the community -- in a series of brief presentations.
Future Colloquia:
Speaker: TBA
Date/Time: 4:15 pm, Monday
Location: LASR Conference Room
Past Colloquia:
"Mars: Planet or Embryo?"Speaker: Nicolas Dauphas
Date: Monday, October 3, 2011
Abstract: Terrestrial planets are thought to have formed through collisions between large planetary embryos of diameter ~1,000-5,000 km. For Earth, the last of these collisions involved an impact by a Mars-size embryo that formed the Moon 50-150 million years (Myr) after the birth of the Solar System. Although model simulations of the growth of terrestrial planets can reproduce the mass and dynamical parameters of the Earth and Venus, they fall short of explaining the small size of Mars. One possibility is that Mars was a planetary embryo that escaped collision and merging with other embryos. To assess this idea, it is crucial to know Mars' accretion timescale. I will show that Mars accreted very rapidly, which is consistent with a stranded planetary embryo origin.
"The chemistry of galaxy formation"
Speaker: Andrey Kravtsov
Date: Monday, November 7, 2011
Abstract: I will discuss the current state of modeling galaxy formation in cosmological context of LCDM model and review both success and challenges of such modeling. Recent progress shows that we are quite close to understanding the main features of galaxy formation and origin of observed properties of galaxies, such morphology, baryon and dark matter connection, etc. I will argue that recent modeling results indicate that correct modeling of galaxy formation requires the right "chemistry" - a non-trivial mix of nonlinear processes - to be treated correctly. To this end, I will present a novel model of star formation based on non-equilibrium treatment of molecular hydrogen in self-consistent cosmological simulations of galaxy formation, including effects of self-shielding and shielding by dust. The model predicts strong dependence of the global Kennicutt-Schmidt star formation relation on the metallicity of the interstellar medium of galaxies (and a weaker dependence on the interstellar UV field) and can explain recent results indicating inefficient star formation in high-redshift Damped Lyman alpha galaxies at z~3. General considerations and some preliminary simulation results indicate that low efficiency of star formation at high redshifts can have significant implications for galaxy formation and may help resolve many of the main problems and puzzles of galaxy formation within hierarchical CDM scenario. I will also present ongoing efforts to understand the mechanisms which can make stellar feedback efficient with globally inefficient star formation.
"A Quest for Brightness"
Speaker: Kwang-Je Kim
Date/Time: 4:15 pm, Monday, December 5, 2011
Location: LASR Conference Room (933 E. 56th St., Room 162)
Abstract: The brightness -- phase space density -- plays an important role in particle and radiation beam applications. The spectacular increase in x-ray beam brightness during the last few decades, from synchrotron radiation devices to free electron lasers, was possible due to the increase in the electron beam brightness from storage rings to linear accelerators. This talk will give an overview of these technological developments, as well as the need for a more basic understanding of the brightness based on an entropy concept.
"The COUPP Dark Matter Search -- Results from the First Year of Deep Underground Running at SNOLAB"
Speaker: Eric Dahl
Date/Time: 4:15 pm, Monday, January 9, 2012
Abstract: Precision cosmology tells us that most of the matter in the universe is dark, non-baryonic and non-relativistic. Whatever makes up this dark matter must lie outside the standard model of particle physics. The leading candidate for the dark matter is an undiscovered, stable Weakly Interacting Massive Particle (WIMP) which, if it is the dark matter, would be detectable in terrestrial detectors as the particles elastically scatter off atomic nuclei, The COUPP Collaboration uses bubble chambers to search for this elusive signal, and in the summer of 2010 deplyed a 4kg bubble chamber 6800' below ground at SNOLAB in Sudbury, Ontario. I will present results from the first year of data from this detector, including the world-leadin limit on the spin-dependent WIMP-proton cross section. With an ongoing campaign that will increase our WIMP sensitivity by an order of magnitude every year, COUPP may soon lead the field across the board in the hunt for WIMP dark matter and, if WIMPs exist, could make the first detection of particles outside the standard model.
"Probing fundamental physics by measuring the cosmic microwave background from over 17,000 feet "
Speaker: Michael Niemack
Date/Time: 4:15 pm, Monday, February 6, 2012
Abstract: Probing fundamental physics by measuring the cosmic microwave background from over 17,000 feet.
Recent measurements of the cosmic microwave background (CMB) have played a major role in the development of the "standard model" of cosmology: a universe dominated by dark energy and dark matter. However, fundamental aspects of the cosmos remain elusive, such as the nature of dark energy and dark matter and whether an inflationary epoch occurred in the first ~10^(-30) seconds after the big bang. We are helping to address these issues with high precision and high resolution measurements of the CMB temperature and polarization.
The 6-meter Atacama Cosmology Telescope (ACT) is located at 17,030 feet (5190 meters) in northeastern Chile, and was used to observe the CMB temperature fluctuations on arcminute scales for three arrays of superconducting transition-edge sensor bolometers (operated at 148, 218, and 277 GHz) in 2008. These measurements led to improved constraints on cosmological parameters, the first detection of the CMB gravitational lensing power spectrum, and the discovery of new galaxy clusters. We are now deploying two polarization-sensitive instruments at the ACT site to probe the CMB on both large and small angular scales using new superconducting polarimeter arrays developed at NIST with the Truce Collaboration (including members of the ACT, ABS, and South Pole Telescope teams). The Atacama B-mode Search (ABS) will probe GUT energy scales by searching for the "smoking gun of inflation" - the signature of inflationary gravity waves in the CMB polarization. The ACTPol receiver will add polarization sensitivity to ACT (as well as ~4x the temperature sensitivity) enabling a wealth of new science objectives. By making precision measurements of the polarization anisotropy power spectra and gravitational lensing of the CMB, ACTPol will provide strong constraints on the inflationary potential, the sum of the neutrino masses, and early dark energy. Cross-correlating these measurements with optical observations will strengthen constraints on the nerutrino mass sum and dark energy, in addition to providing optical counterparts for the >10^3 galaxy clusters detected by ACTPol. I will also discuss plans for next generation observatories, including the balloon-borne deLensing Inflation by Tomography Experiment (deLITE), that will map the dark matter distribution via CMB lensing and search for inflationary gravity waves with unprecedented precision. I will describe the science, observations, and new technologies, including developments towards observatories of the future.
"Current state and prospects for LIGO"
Speaker: Rainer Weiss
Date/Time: 3:30 pm, Wednesday, March 7, 2012
Abstract: This talk will be an overview of the Laser Interferometer Gravitational Wave Observatory (LIGO). The talk will include a description of the initial instrument and results from the science runs. We will describe the current instrument upgrade, and discuss the prospects for the detection of gravitational waves. We will also discuss future directions, including an international wave detections, and future delvelopments of the instrument in response to detections.
"Scientific Discovery Through Large-Scale Computer Simulations: Type Ia Supernovae and High Energy Density Physics Experiments"
Speaker: Don Lamb
Date/Time: 415 pm, Monday, April 2, 2012
Abstract: The Flash Center for Computational Science is the developer of FLASH, a highly capable, fully modular and extensible radiation-hydrodynamics/MHD community code that scales to well over a hundred thousand processors. FLASH is currently being used to simulate phenomena range of scientific fields, including astrophysics, cosmology, computational fluid dynamics, plasma physics, and high energy density physics (HEDP). I first describe the challenges of exascale computing, and the Center?s strategic plan for taking FLASH to the exascale. I then describe the Center?s discovery of an entirely new explosion mechanism for Type Ia (thermonuclear-powered) supernovae, and its program to validate current models of these events using simulations and high-quality observational data from the SDSS Supernova Survey and the Dark Energy Survey. Finally, I describe the Center?s collaboration with the High Energy Density Laboratory Astrophysics Group at the University of Oxford to use FLASH to help design, execute, and analyze HEDP experiments that are transforming our understanding of the generation and amplification of cosmic magnetic fields, and the properties of matter in the interiors of planets.