January 10, 2018 | 3:30 PM | ERC 161 From Emergent Gravity to Dark Energy and Dark Matter Erik P. Verlinde, University of Amsterdam
Video The observed deviations from the laws of gravity of Newton and Einstein in galaxies and clusters can logically speaking be either due to unseen dark matter or due to a change in the way gravity works. Until recently there was little reason to doubt that general relativity correctly describes gravity in these circumstances. In the past few years insights from black hole physics and string theory have lead to a new theoretical framework in which the gravitational laws are derived an underlying microscopic quantum description of spacetime. An essential ingredient in the derivation of the Einstein equations is that the quantum entanglement of the vacuum obeys an area law, a condition that is known to hold in Anti-de Sitter space. In a Universe that is dominated by positive dark energy, like de Sitter space, the microscopic entanglement entropy contains, in addition to the area law, a volume law contribution whose total contribution equals the Bekenstein-Hawking entropy associated with the cosmological horizon. We will argue that this extra volume law contribution leads to modifications in the emergent laws of gravity, and provide evidence for the fact that these modifications explain the observed phenomena in galaxies and clusters currently attributed to dark matter. We end with a discussion of the possible implications for early cosmology, the CMB and structure formation.
January 24, 2018 | 3:30 PM | ERC 161 Citizen Science Frontiers: Efficiency, Engagement, and Serendipitous Discovery with Human-Machine Systems Laura Trouille, The Adler Planetarium and Northwestern University Note: Reception at 4:30 PM in the ERC 401.
The Zooniverse is the world's largest and most successful scientific crowdsourcing platform, engaging more than 1.6 million volunteers in tasks including classifying galaxies, discovering planets, transcribing artist’s notebooks, and tracking resistance to antibiotics. Processing our increasingly large datasets poses a bottleneck for producing real scientific outcomes. Citizen science – engaging the public in research – provides a solution, particularly when coupled with machine learning algorithms and sophisticated task allocation. Faced with a rapidly growing demand for citizen science projects, Zooniverse launched its ‘Project Builder’ which allows you, the researcher, to build your own project in-house for free using the Zooniverse infrastructure and tools. In this talk I will discuss the frontiers of citizen science, including Zooniverse innovations in human-machine integration coupled with community engagement -- and the related open questions. I will also provide a brief tutorial on building your own crowdsourcing project.
February 7, 2018 | 3:30 PM | ERC 161 TBA Peter Adshead, University of Illinois at Urbana-Champaign
March 14, 2018 | 3:00 PM | ERC 161 Dark Matter in the Universe Katherine Freese, University of Michigan Note: Reception at 4:30 PM in the ERC 401.
â€śWhat is the Universe made of?â€ť This question is the longest outstanding problem in all of modern physics, and it is one of the most important research topics in cosmology and particle physics today. The bulk of the mass in the Universe is thought to consist of a new kind of dark matter particle, and the hunt for its discovery in on. I'll start by discussing the evidence for the existence of dark matter in galaxies, and then show how it fits into a big picture of the Universe containing 5% atoms, 25% dark matter, and 70% dark energy. Neutrinos only constitute Â˝% of the content of the Universe, but much can be learned about neutrino properties from cosmological data. Leading candidates for the dark matter are Weakly Interacting Massive Particles (WIMPs), axions, and sterile neutrinos. WIMPs are a generic class of particles that are electrically neutral and do not participate in strong interactions, yet have weak-scale interactions with ordinary matter. There are multiple approaches to experimental searches for WIMPS: at the Large Hadron Collider at CERN in Geneva; in underground laboratory experiments; with astrophysical searches for dark matter annihilation products, and upcoming searches with the James Webb Space Telescope for Dark Stars, early stars powered by WIMP annihilation. Current results are puzzling and the hints of detection will be tested soon. At the end of the talk I'll briefly turn to dark energy and its effect on the fate of the Universe.
January 12, 2018 | 12:00 PM | ERC 401 Topics in weak lensing Patricia Larsen, Argonne National Laboratory
Gravitational weak lensing has emerged in recent years as a powerful probe of cosmology, giving important constraints on both dark and luminous matter. This has led to a number of ambitious future surveys, which promise to revolutionise the field if theoretical challenges can be met. In this talk I will discuss some of my recent work in the field of weak lensing, spanning a range of topics including combined probe analysis, intrinsic alignment contamination and delensing.
January 19, 2018 | 12:00 PM | ERC 401 Discussion on old and new mechanisms of leptogenesis Jessica M Turner, Fermi National Accelerator Laboratory
In the first half of the talk, I will present preliminary results which indicate the scale of thermal leptogenesis may be several orders of magnitude lower than previously thought.
In the second half of this talk I will present a mechanism of leptogenesis which is based on the vacuum CP-violating phase transition. This approach differs from classical thermal leptogenesis as a specific seesaw model, and its UV completion, need not be specified. The lepton asymmetry is generated via the dynamically realised coupling of the Weinberg operator during the phase transition. This
mechanism provides strong connections with low-energy neutrino experiments.
January 26, 2018 | 12:00 PM | ERC 401 Mass' not the only thing: Secondary effects in the galaxy-halo connection Yao-Yuan Mao, University of Pittsburgh
February 2, 2018 | 12:00 PM | ERC 401 High redshift 21cm intensity mapping Past, Present, and Future Daniel Jacobs, Arizona State University
The redshifted 21 cm line from neutral hydrogen provides a direct, cosmological scale, probe of the epochs of reionization and heating. In the past decade, multiple experimental arrays have worked towards detection and characterization of this spectral line signal at redshifts 6 and higher. HERA is a second generation instrument probing 21cm emission and absorption at redshifts from 6 to 20. The use of large static dishes provides sensitivity which is predicted to be roughly an order of magnitude larger than first generation experiments while advances in instrumentation and technique aim for reduced foreground contamination. The raw sensitivity provided by dishes is high enough that forecasts of astrophysical parameter constraint precision is limited mainly by model uncertainty not sensitivity, and that for the first time direct imaging of features is theoretically possible. HERA is proceeding with construction while observing in parallel with new dishes being added as they become available. The 2017-2018 observing season with 40 dishes is forecasted to have roughly double the sensitivity of previous experiments. Here we report the ongoing commissioning of this array and present early results of experiments in calibration and imaging.
February 9, 2018 | 12:00 PM | ERC 401 The impact of massive neutrinos on cosmological observables Francisco Villaescusa-Navarro, Center for Computational Astrophysics
January 17, 2018 | 3:30 PM | ERC 161 WFIRST: Where Things Stand with the First Exoplanet Direct Imaging Flight Mission Maggie Turnbull, SETI
The WFIRST mission will be the first demonstration of exoplanet coronagraphy in space, and is intended to demonstrate several key technologies that are on the critical path to larger missions that will eventually find and spectrally characterize planets that could be habitable to life as we know it. WFIRST entered Phase A in January of 2016, and is expected to enter Phase B in April of this year. This talk will describe the entertaining story of how this mission came to be, where things currently stand in terms of predicted imaging performance, the potential for a starshade rendezvous mission, and what to expect for guest observer opportunities. I'll also describe how the two coronagraph science teams are working to maximize the scientific output of what is categorized as a "technology demonstration" instrument. Finally, I'll offer some of my personal take-aways from the experience of watching such a large and challenging mission come together.
January 31, 2018 | 3:30 PM | ERC 161 TBA Ellen Zweibel, University of Wisconsin-Madison Note: Refreshments served at 4:30 PM, Hubble Lounge
February 14, 2018 | 3:30 PM | ERC 161 TBA Tim Heckman, Johns Hopkins University Note: Refreshments served at 4:30 PM, Hubble Lounge
February 28, 2018 | 3:30 PM | ERC 161 TBA Enrico Ramirez-Ruiz, University of California, Santa Cruz Note: Refreshments served at 4:30 PM, Hubble Lounge
March 7, 2018 | 3:30 PM | ERC 161 TBA Bekki Dawson, Pennsylvania State University Note: Refreshments served at 4:30 PM, Hubble Lounge
January 16, 2018 | 12:00 PM | ERC 576 Surveying Spotted Stars with Photometric, Spectroscopic, and Interferometric Observations Rachael Roettenbacher, Stockholm University
For stars with convective outer layers, stellar magnetism manifests as dark starspots -- localized regions of stifled convection. Starspots affect measurements of fundamental stellar parameters, including temperature and radius, which lead to inaccurate estimates of age and mass. Additionally, starspots have been shown to mimic and obscure detections of planets. By imaging stellar surfaces, we begin to disentangle the signatures of stellar magnetism. The imaging efforts discussed here feature aperture synthesis imaging using interferometric data collected with the Michigan Infrared Combiner (MIRC) at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array with sub-milliarcsecond resolution. We characterize active RS CVn binary systems and detect magnetic structures across the surface of the giant primary stars. We compare the results to simultaneous Doppler and light curve inversion imaging. The observed global regions of suppressed convection likely affect stellar parameter estimates by altering the structure of the photosphere. Extensions of this study will survey spotted stars in order to understand how stellar magnetism affects stellar parameters, impacts the evidence of companions and their characterization, accounts for long-term changes in the flux of active stars, and differs from the Sun for stars with large convective envelopes.