Talks & Events
KICP Colloquia: 2012
Large-scale clustering of BOSS galaxies
I'll discuss latest results on clustering of galaxies on scales from 100 kpc to 100 Mpc in the Baryonic Oscillations Spestroscopic Survey (BOSS). Results are compared with predictions of the LCDM model.
The Interplay of Supermassive Black Hole Growth and Galaxy Evolution
The growth of black holes over billions of years releases energy that may quench star formation ("feedback"). Tracing the cosmic history of black hole growth with multiwavelength surveys, we find that most AGN are heavily obscured and that obscuration is more common in the young Universe and in low-luminosity AGN. Most black hole growth takes place in moderate luminosity AGN rather than quasars, and feedback in these systems affects far more galaxies than do quasars. At z~1ÿÿ2, we see evidence that AGN may help quench star formation (which is not the case at z~0). Perhaps surprisingly, most moderate luminosity AGN are hosted in disky galaxies, out to z~2, suggesting that major mergers do not trigger most black hole growth. Finally, we find an intriguing dependence of AGN activity on host galaxy morphology which is not yet fully explained.
The Fate of the False Vacuum in the Era of the LHC and Precision Cosmology
The LHC guarantees to grant us insight into the origin of electroweak symmetry breaking. When combined with precision cosmological data, this will allow for a partial reconstruction of a new rung in the historical ladder of early universe cosmology, particularly regarding how the universe transitioned from the electroweak symmetry preserving false vacuum to the true vacuum that we live in today. In addition to the electroweak phase transition, I examine what other phase transition related information we may hope to obtain in the foreseeable future. The topics discussed from this perspective will include electroweak baryogenesis, dark matter, dark energy, gravity waves, and the implications of the recent hint of the Higgs boson at 125 GeV.
Hot on the Trail of Warm Planets Orbiting Cool M Dwarfs
Just three years ago the prospect of finding temperate, rocky worlds around other stars was still the subject of science fiction: none had been found and reasonable estimates put us years or decades away from such a momentous discovery. All of that has changed very recently on the heels of the extraordinarily successful NASA Kepler mission. By searching for the tiny diminutions of starlight indicative of an eclipsing planet, Kepler has produced thousands of new planet candidates orbiting distant stars. Careful statistical analyses have shown that the majority of these candidates are bona fide planets, and the number of planets increases sharply toward Earth-sized bodies. Even more remarkably, many of these planets are orbiting right "next door," around tiny red dwarf stars, several of them residing the the Goldilock's zone where temperatures are amenable to the existence of liquid water. I will describe our multi-telescope campaign to validate and characterize these micro planetary systems, and present some early, exciting results that point the way to the first detection of the first Earth-sized planet in the habitable zone of a star.
Inflation, or What?
Inflation has emerged as the leading model for the very early universe, not least because of the theory's remarkably successful prediction for the form of the CMB anisotropy. I ask the question: is inflation the only way to match the data? If not, what do the possible alternatives look like?
Probing the Transient Universe with Gravitational Waves
The Laser Interferometer Gravitational-wave Observatory (LIGO) and its sister project Virgo aim to achieve, within this decade, the first direct detection of gravitational waves and tune in to the gravitational-wave soundtrack of the Universe. The information from gravitational waves, complementary to the multi-wavelength electromagnetic spectrum, neutrinos and cosmic rays, will contribute to a more complete, understanding of some of the most violent and energetic events in the universe, such as gamma-ray bursts, soft-gamma repeaters, supernovae, and glitching pulsars. In this talk I will give an overview of ongoing efforts towards the realization of this new gravitational wave astrophysics, and of how electromagnetic and neutrino observations and the theoretical understanding of source dynamics are coupled into gravitational wave analysis. I will present selected results from the initial generation of LIGO and Virgo data and outline prospects for discovery in the advanced detector era, with particular focus on transient signatures.
The Other Side of Galaxy Formation: modeling gas in and around galaxies
Much observational work has focused on measuring the star formation rate in galaxies and its cosmic evolution. However, the supply rate of fuel for star formation (cold dense gas), the internal processes that regulate its conversion into stars, and the feedback processes that regulate star formation, all remain poorly understood both theoretically and observationally. I will discuss recent attempts to build more sophisticated theoretical models to predict the multi-phase gas content of galaxies, which in particular will allow us to make connections between galaxies as observed via stellar emission, emission in CO or HI, and in absorption.
Diffuse Supernova Neutrino Background
The diffuse supernova neutrino background (DSNB) is the weak glow of MeV neutrinos and antineutrinos from distant core-collapse supernovae. The DSNB has not been detected yet, but the Super-Kamiokande upper limit on the electron antineutrino flux is close to predictions, now quite precise, based on astrophysical data. If SK is modified with dissolved gadolinium to reduce detector backgrounds, then it should detect the DSNB at a rate of a few events per year, providing a new probe of supernova neutrino emission and the cosmic core-collapse rate. Neutrino astronomy, while uniquely powerful, has proven extremely difficult - only the Sun and the nearby Supernova 1987A have been detected to date - so the promise of detecting new sources soon is exciting indeed.
Status of SUSY and SUSY Dark Matter
Weak-scale supersymmetry has long been a dominant paradigm for physics beyond the standard model and particle dark matter, but it is now being challenged by a wealth of experimental data. I will begin by reviewing attempts to quantify naturalness in supersymmetry, stressing the many subjective choices that impact the results both quantitatively and qualitatively. I then summarize experimental results that most directly challenge weak-scale supersymmetry, including recent results from the LHC. Some models are excluded or under great tension, while others remain perfectly viable. For the latter, I will outline the key features, current status, and implications for colliders and dark matter searches.
The Search for Dark Matter with XENON
We know that most of the matter in the Universe is Dark Matter, but we don't know what Dark Matter is made of. Current and upcoming detectors have the sensitivity to detect or exclude Weakly Interacting Massive Particles (WIMPs) as candidates for Dark Matter. In this talk, I will review the basics of the direct search for WIMPs and give a quick overview of the current status of the field. The XENON100 experiment in particular is a leading experiment in this search and will be presented in some detail, together with recent results from a search in 225 live days of data. An outlook on where we are headed in the next few years will be given.
From cosmology to cold atoms: observation of Sakharov acoustic oscillations in quenched atomic superfluids
Sakharov oscillation, conventionally discussed in the context of early universe evolution and the anisotropy of cosmic microwave background radiation, is the manifestation of interfering acoustic waves generated in an ideal fluid. We report a laboratory observation of Sakharov oscillations in a quenched atomic superfluid. We quench the interactions between atoms and monitor the subsequent density fluctuations at different time and length scales. Sakharov oscillations are identified as the multi-peak structure in the density power spectrum, resembling that of the cosmic microwave background radiation.
From the oscillations, we determine the sonic horizon, providing new perspectives to extend quantum simulation to other intriguing cosmological and gravitational phenomena
Direct Detection of WIMP dark matter: the nitty-gritty
I'll present an update on the status of dark matter direct detection experiments, with particular emphasis on details that the non-experimentalist may ignore, or the experimentalist may hide. I will also focus on local activities in this area (COUPP, CoGeNT, DAMIC, and dedicated calibration experiments for a number of target materials).
Modified gravity from the micron to the megaparsec
The observed cosmic acceleration hints at a low-energy modification to General Relativity which could give rise to fifth forces and new particles. After describing f(R), chameleon, and symmetron models, I will discuss constraints on the resulting fifth forces from laboratory torsion pendulum experiments, the stability of stars, and the dynamics of large-scale cosmic structure. In particular, laboratory experiments are on the verge of testing interesting classes of chameleon and symmetron fifth forces. I will also show how new particles predicted by these models, which might be produced through photon interactions in stars or the laboratory, can be used to constrain modifications to gravity.