Talks & Events
KICP Friday Noon Seminars
Current & Future KICP Seminars
Past KICP Seminars
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.
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.
Mass' not the only thing: Secondary effects in the galaxy-halo connection
Yao-Yuan Mao, University of Pittsburgh
Dark matter halos are the building blocks of our universe. The story we have been telling is that the galaxies live in halos, and that brighter galaxies live in bigger halos. This story is mostly consistent with our observation and hydrodynamical simulations, and has shed light on our understandings of galaxy formation and evolution. However, it is also clear that this simple, zeroth-order galaxy-halo connection is not the whole story. The assembly history of halos affects the galaxies reside in, and also affects the clustering properties of halos. This effect, usually known as "assembly bias," has brought new challenges to our ability to accurately model the galaxy-halo connection. A class of galaxy-halo connection models that take assembly bias into account has emerged, but it at the same time highlights the complex nature of assembly bias. In this talk I will discuss a few different aspects of assembly bias, focusing on how it affects the galaxy-halo connection and also its implications.
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.
The impact of massive neutrinos on cosmological observables
Francisco Villaescusa-Navarro, Center for Computational Astrophysics
Neutrinos are one of the most mysterious particles in nature. The discovery that they are massive has revolutionized our understanding of fundamental physics. Unfortunately, we still don't know their nature, masses or hierarchy. A worldwide effort is underway trying to answer these questions through laboratory experiments. In this seminar I will show how neutrino's unique nature leaves signatures on many different cosmological observables such as the properties of matter, halos, galaxies, voids, redshift-space distortions, the Lya-forest, baryonic acoustic oscillations and 21cm. I will discuss how those signatures can be used to weigh neutrinos and what are the main problems to obtain an unbiased measure of their masses.
Project 8: Towards a Direct Measurement of the Neutrino Mass with Tritium Beta Decays
Noah S Oblath, Pacific Northwest National Laboratory
Cyclotron Radiation Emission Spectroscopy, a frequency-based method for deter- mining the energy of relativistic electrons, has recently been demonstrated by the Project 8 collaboration. Applying this technique to the tritium endpoint provides a new avenue for measuring the absolute mass-scale of the neutrino. The proof of principle was done in a small waveguide detector using gaseous 83mKr as a source of monoenergetic electrons. As the next step towards a neutrino mass measurement, we are upgrading the existing detector to operate using a molecular tritium source, and to have enhanced radiofrequency properties. These upgrades are the next research and development steps needed to design a larger scale experiment that will approach the existing neutrino mass limits. I will discuss the expected physics reach of this second phase of Project 8 with molecular tritium, based on data from its commissioning with 83mKr. I will also present the plans for Phases III and IV, and the challenges being addressed for each phase.
Innovations in Big Data and HPC for Cosmology
Deborah Bard, NERSc, LBNL
Cosmological ''big data'' problems go beyond the simple volume of data stored on disk. Our observations of the universe are necessarily finite, and the challenge we face is how we can extract the maximum amount of information from the observations and simulations we have available to us.
High Performance Computing (HPC) is increasingly being used to enable complex analyses that were previously inaccessible to scientists. NERSC is the mission computing center for the DOE Office of Science, and we sit at the intersection of HPC, algorithmic development and cutting-edge science. I will discuss some of the cosmology projects we lead in this space, such as Galactos (calculating the anisotropic three-point correlation function for 20 billion galaxies), Celeste (cataloguing the visible universe through Bayesian inference using Julia), CosmoGAN (developing a cosmological emulator using generative adversarial networks) and CosmoFlow (learning the structure of the universe through 3D deep learning techniques).
These projects showcase a combination of computer science, HPC advances and real problems in cosmology, with the overarching theme of how we can scale computing tools (including machine learning and inference) to enable new techniques in data analysis, and to accelerate time-to-discovery.
Galaxy Cluster Cosmology with the Dark Energy Survey
Yuanyuan Zhang, Fermilab
Constraining LambdaCDM cosmology with galaxy cluster abundance is one of the fundamental goals of the Dark Energy Survey (DES). Many thousands of clusters out to redshift 0.65 have been identified in DES data. Weak lensing and multi-wavelength studies with X-ray and cosmic microwave background observations are performed to provide inputs to the cosmology analysis. A cosmology pipeline that considers various systematic effects such as cluster projections and mis-centering is used to derive constraints on LambdaCDM cosmology parameters. In this talk, I will present current progress on DES galaxy cluster cosmology analyses as well as discuss future improvements.
Primordial Black Holes in the era of Planck and LIGO
Yacine Ali-Haimoud, New York University
Simulating structure formation in different environments and the applications
Chi-Ting Chiang, C.N. Yang Institute for Theoretical Physics/Stony Brook University