January 9, 2019 | 3:30 PM | ERC 161 | Wednesday colloquium How many numbers does it take to determine our Universe? Michael Turner, KICP
Video Since 2013, the Planck Surveyor team has made a good case that it takes six numbers to describe the whole Universe (fewer than the ten digits in a phone number), based upon their all-sky map of the CMB. Others have different opinions: zero, one, two, six (a different), and nine to describe our Universe. As I will discuss, the choice of numbers reveals much about what we know and our aspirations, as well as how we think about the Universe. After exploring the landscape, I will advocate for zero numbers and discuss the path and strategy to get there.
January 16, 2019 | 3:30 PM | ERC 161 | Astronomy Colloquium Cosmic Reionization Nick Gnedin, University of Chicago/Fermilab
Cosmic reionization - ionization of the bulk of cosmic gas by ultraviolet radiation from first galaxies and quasars - is the least explored epoch in cosmic history. While significant progress has been made recently with the HST Frontier Fields program, the major breakthrough is still in the future, but not a distant one. The launch of JWST will start a revolution in studies of cosmic reionization, and other advanced observational probes will follow soon. As observers are preparing for the flood of new data, theorists are currently busy revamping their tools to stay on par with future observations. This fortunate match between theory and observations will lead to a major breakthrough in this last cosmic frontier.
January 23, 2019 | 3:30 PM | ERC 161 | Wednesday colloquium A New Frontier in the Search for Dark Matter Gordan Krnjaic, Fermilab
Note: Reception at 4:30 PM in the ERC 401.
The gravitational evidence for the existence of dark matter is overwhelming; observations of galactic rotation curves, the CMB power spectrum, and light element abundances independently suggest that over 80% of all matter is "dark" and beyond the scope of the Standard Model. However, its particle nature is currently unknown, so discovering its potential non-gravitational interactions is a major priority in fundamental physics. In this talk, I will survey the landscape of light dark matter theories and and introduce an emerging field of fixed-target experiments that are poised to cover hitherto unexplored dark matter candidates with MeV-GeV masses. These new techniques involve direct dark matter production with proton, electron, and *muon* beams at various facilities including Fermilab, CERN, SLAC, and JLab. Exploring this mass range is essential for fully testing a broad, predictive class of theories in which dark matter abundance arises from dark-visible interactions in thermal equilibrium in the early universe.
January 30, 2019 | 3:30 PM | ERC 161 | Astronomy Colloquium TBA Ian Crossfield, MIT
Note: Refreshments served at 4:45 PM, Hubble Lounge
February 6, 2019 | 3:00 PM | ERC 161 | Wednesday colloquium The Planck last release Jean-Loup Puget, IAS Université Paris-sud
Note: Reception at 4:30 PM in the ERC 401.
The Planck High frequency maps improvements will be described together with some of their associated cosmology results. Implications for future experiments will also be discussed.
February 13, 2019 | 3:30 PM | ERC 161 | Astronomy Colloquium TBA Roger Blandford, Stanford University
Note: Refreshments served at 4:45 PM, Hubble Lounge
January 11, 2019 | 12:00 PM | ERC 401 | Friday noon seminar Searching for the aftermath of binary neutron star mergers Michael W Coughlin, California Institute Of Technology
Binary neutron star mergers provide one of the richest laboratories for studying physics with ground-based interferometric gravitational-wave detectors such as advanced LIGO and Virgo. After such a merger, a compact remnant is left over whose nature depends primarily on the masses of the inspiralling objects and on the equation of state of nuclear matter. We will discuss the search for short and intermediate-duration post-merger signals from GW170817, as well as all-sky, all-time searches for the same. In addition, we will describe ongoing searches for the detection of transients like GW170817 in electromagnetic wavelengths. With the Zwicky Transient Facility recently achieving first light, it is now fruitful to use its unprecedented combination of depth, field of view, and survey cadence to perform Target of Opportunity observations. Using the 50 square degree field of view of the instrument, it is possible to follow-up events from systems like the Fermi Gamma-Ray Burst Monitor, where it can be necessary to cover thousands of square degrees. We will demonstrate on short gamma-ray bursts how it is possible to use this system to do follow-up on this scale.
January 18, 2019 | 12:00 PM | ERC 401 | Friday noon seminar Inflation with Spooky Correlations Craig Hogan, The University of Chicago
Famous "information paradoxes" in black hole theory can be solved if quantum information on horizons is delocalized or "spooky", like states of entangled particles. Similar spooky correlations on the inflationary horizon are estimated to produce curvature perturbations with a dimensionless power spectral density given by the inflationary expansion rate H in Planck units, larger than standard inflaton fluctuations. Current measurements of the spectrum are used to derive constraints on parameters of the effective potential in a slow-roll background. A distinctive and robust new prediction, in the sense of being insensitive to the details of specific spooky models, is an exact directional antisymmetry, traceable directly to the nonlocality and directional correlation of initial conditions on the horizon, which is forbidden in standard models. Signatures of this primordial antisymmetry might already be measured in CMB anisotropy, and if they are indeed due to nearly-scale-invariant primordial spookiness, should also be observable in large scale 3D galaxy surveys, possibly even in existing data. DES may be the first dataset capable of detecting this direct signature of Planck scale quantum physics.
January 25, 2019 | 12:00 PM | ERC 401 | Friday noon seminar New Directions for Direct Detection of MeV-Scale Dark Matter Noah Kurinsky, Fermi National Accelerator Laboratory
While the case for dark matter continues to strengthen from the astrophysical side, particle dark matter has so far eluded the current generation of experiments, designed to probe the SUSY-motivated mass range of GeV-TeV scale dark matter. Meanwhile, the LHC has ruled out the simpler SUSY models, and the simple picture of a weak-scale, 30 GeV supersymmetric dark matter particle has begun to fade. In this talk, I will discuss recent advances in the search for Sub-GeV dark matter down to MeV-scale masses, and the path forward to new technologies capable of probing down to keV-scale mass fermionic dark matter scattering and meV-scale mass bosonic dark matter absorption. These include, but are not limited to, the use of superconductors as well as novel semiconductors as the target medium and readout stages. The energy resolution required to search for low-mass dark matter makes these technologies interesting as general imaging techniques for infrared and UV astronomy, as well as for coherent neutrino scattering and other low-energy rare event search experiments, and I will briefly touch on applications of these new technologies to those fields.
February 1, 2019 | 12:00 PM | ERC 401 | Friday noon seminar Scalar fields and strong-field gravity: spontaneous scalarization of compact objects Hector Okada da Silva, Montana State University
February 8, 2019 | 12:00 PM | ERC 401 | Friday noon seminar Testing Self-Interacting Dark Matter with Galaxy Warps Kris Pardo, Princeton University
February 15, 2019 | 12:00 PM | ERC 401 | Friday noon seminar Early Dark Energy and the Hubble Tension Tanvi Karwal, Johns Hopkins University
Although the standard Lambda-CDM model of cosmology is in excellent agreement with the observed cosmic microwave background (CMB) power spectrum, its prediction for the current rate of expansion H0 of the Universe is in tension with observations of the local universe at > 3 sigma, with local measurements preferring a higher value. Systematic causes have been investigated and not found to be the culprit. Could this then indicate new physics?
My talk will present a new-physics solution to the Hubble tension that modifies the early expansion history of the Universe through the addition of an early dark energy (EDE) component. This behaves like a cosmological constant at early times and then dilutes quickly with redshift after some critical time. It therefore only influences the Universe over a small range in redshift.
This solution is successful because the Hubble tension can be translated into an equivalent tension in the size of the sound horizon.
If such an EDE becomes dynamical before recombination, it increases the pre-recombination expansion rate and decreases the sound horizon, shifting the expected peaks in the CMB power spectrum to smaller angular scales. These can be brought back in agreement with observations by an increase in the predicted value of H0, reducing the Hubble tension.
I will present two physical scalar-field models for such an EDE, and their success with resolving the Hubble tension while still finding a good fit to most cosmological datasets.
February 22, 2019 | 12:00 PM | ERC 401 | Friday noon seminar kSZ Cosmology without the optical depth degeneracy Mathew S Madhavacheril, Princeton University
March 1, 2019 | 12:00 PM | ERC 401 | Friday noon seminar The Population of Binary Black Holes from Gravitational-wave Observations Chris Pankow, Northwestern University
I will present the current inventory of binary black holes (BBH) collected during the first and second observing runs of the LIGO/Virgo gravitational-wave interferometer network. The ten BBH observed to date provide the means to resolve questions about their formation and population properties. As such, I will also present new estimates of the mass, spin, and merger rate distributions of stellar mass BBH. All analyses consistently find merger rate distributions over the primary mass which predict almost no black holes above 45 solar masses. We also find that probes of the rate evolution with redshift prefer inclining or flat models. The inferred spin magnitude distribution strongly disfavors high spin magnitudes when the component spins are aligned to the orbital angular momentum. Finally, I will describe prospects for what the future might hold for BBH in future observing runs.
March 22, 2019 | 12:00 PM | ERC 401 | Friday noon seminar TBD Zhong-Zhi Xianyu, Harvard University