Seminar archive 2016

Raw date Event date Title Speakers Host Summary Links
20160111 Jan. 11, 2016, 2:00 am Fast Radio Bursts I will report on the discovery of a new fast radio burst with a detection of Faraday rotation, wavelength-dependent scattering, and scintillation. The data imply source location in the dense central region of its host galaxy or the presence of magnetized material associated with the source itself. The burst was detected with GBT at 800MHz.... More »
20160125 Jan. 25, 2016, 2:00 am Advances in millimeter-wavelength instrumentation with the South Pole Telescope The Cosmic Microwave Background (CMB) is a powerful cosmological tool, containing the imprint of signals from both the early and late universe. Over the past few years, CMB experiments made significant technological advances that led to the first detection of the extremely faint B-mode polarization signal. Using this signal, experiments have the potential to constrain... More »
20160201 Feb. 1, 2016, 2:00 pm Quantum Twists of Space The talk will review theoretical arguments that if space and time emerge from a quantum system at the Planck scale, there should be nonlocal exotic quantum correlations of positions of massive bodies, even on scales much larger than the Planck length. In relational theories with no fixed background space, these could take the form of... More »
20160208 Feb. 8, 2016, 2:00 pm Helical Magnetic Fields in the Cosmos It is often necessary to study cosmological phase transitions, such as inflation and thermal symmetry-breaking phenomena, through the relics that they leave behind. In this sense, the cosmological magnetic field may be a powerful probe of the early universe, which has yet to be tapped. In this talk, I will survey various topics related to... More »
20160215 Feb. 15, 2016, 2:00 pm CRESST: A direct search for (light) dark matter particles Today, many observations on various astronomical scales provide compelling evidence for the existence of dark matter. Its underlying nature, however, remains an open question of present-day physics. Direct searches aim to find the answer by observing dark matter particles interacting in their detectors. One of the numerous experiments around the globe is CRESST-II, the only... More »
20160222 Feb. 22, 2016, 2:00 pm Pulsar timing limit on gravitational waves necessitates re-assessment of binary supermassive black hole population Mergers of massive galaxies are thought to form binary supermassive black holes, which coalesce through losses of energy and angular momentum to gravitational radiation. For the last decade, collaborations worldwide have been searching for signatures of these gravitational waves in radio timing measurements of millisecond pulsars. The intended sensitivities of these experiments, based on theoretical predictions,... More »
20160229 Feb. 29, 2016, 2:00 pm Chameleon dark energy If dark energy consists of a light scalar field, it might be detectable as a “fifth force” between ordinary-matter objects, in potential conflict with precision tests of gravity. Chameleon fields and other theories with screening mechanisms, however, can evade these tests by suppressing the forces in regions of high density, such as the laboratory. The... More »
20160307 March 7, 2016, 2:00 pm New Cosmological Results from Type Ia Supernovae Type Ia Supernovae play a critical role in measuring dark energy as well as the Hubble Constant. I will go over the latest results from each of these important measurements. I will also discuss the latest interpretations about possible `tension’ in these measurements from different probes including BAO and CMB. I will show what role... More »
20160314 March 14, 2016, 2:00 pm Always in the Last Place You Look: Three New Directions for Dark Matter Detection Searches for dark matter over the last two decades have mainly focused on the Weak-scale mass range. With no detection yet, either in underground searches or the LHC, our best hope going forward is to expand our search to cover as many types of dark matter as possible. I will discuss three budding direct detection... More »
20160321 March 21, 2016, 2:00 pm Next Generation Cosmological Constraints on the Dark Sector and Gravity A rich portfolio of upcoming complementary cosmological experiments will be producing data in the next 5-10 years. I will discuss the goals of the LSST Dark Energy Science Collaboration and the challenges faced to achieve them. I will also discuss ways in which LSST and the other surveys can be used in conjunction to extract... More »
20160328 March 28, 2016, 2:00 pm TBA
20160328 March 28, 2016, 2:00 pm Joining Forces against the Dark Side of the Universe: From the Cosmic Microwave Background to the Large Scale Structure Despite tremendous recent progress, gaps remain in our knowledge of our understanding of the Universe. We have not yet pinned down the properties of dark energy, nor have we confirmed Einstein’s theory of Gravity at the largest scales. Current and upcoming large sky surveys of the Cosmic Microwave Background (CMB), Large Scale Structure (LSS) in... More »
20160404 April 4, 2016, 2:00 pm From Detector to Observatory On September 14, 2015 LIGO made the first direct detection of gravitational waves, marking the transition of the LIGO instruments from detectors to observatories, and the beginning of the era of gravitational wave astronomy. GW150914 provided the first observational proof that binary black holes not only exist, but that they exist in large numbers and... More »
20160411 April 11, 2016, 2:00 pm Special Colloquium (Title TBD) TBD
20160418 April 18, 2016, 2:00 pm Baryogenesis via Particle-Antiparticle Oscillations CP violation, which is crucial for producing the baryon asymmetry of the Universe, is enhanced in particle-antiparticle oscillations. We study particle-antiparticle oscillations (of a particle with mass O(100 GeV)) with CP violation in the early Universe in the presence of interactions with O(ab-fb) cross-sections. We show that, if baryon-number-violating interactions exist, a baryon asymmetry can... More »
20160425 April 25, 2016, 2:00 pm Stellar-Dynamical Inferences about Dark Matter in the Smallest Galaxies The Local Group’s dwarf galaxies include the nearest, smallest, oldest, darkest and least chemically-enriched galaxies known. I will summarize recent results – and present new ones – regarding the amount and spatial distribution of dark matter within these systems. Implications range from tests of the standard `cold dark matter’ model of cosmological structure formation to... More »
20160502 May 2, 2016, 2:00 pm Cosmological Seed Magnetic Field from Inflation A cosmological magnetic field of nG strength on Mpc length scales could be the seed magnetic field needed to explain observed few microG large-scale galactic magnetic fields. I first briefly review the observational and theoretical motivations for such a seed field, two galactic magnetic field amplification models, and some non-inflationary seed field generation scenarios. I... More »
20160511 May 11, 2016, 2:00 pm Resolving the Isotropic Gamma-Ray Background in the Search for Dark Matter The presence of all-sky, diffuse gamma-ray emission has been known for several decades, but its origins remain an open question. While astrophysical sources such as Active Galactic Nuclei and star-forming galaxies almost certainly contribute to this Isotropic Gamma-Ray Background (IGRB), dark-matter annihilation may also leave an imprint. Therefore, resolving the components of the IGRB is... More »
20160511 May 11, 2016, 2:00 pm Resolving the Isotropic Gamma-Ray Background in the Search for Dark Matter The presence of all-sky, diffuse gamma-ray emission has been known for several decades, but its origins remain an open question. While astrophysical sources such as Active Galactic Nuclei and star-forming galaxies almost certainly contribute to this Isotropic Gamma-Ray Background (IGRB), dark-matter annihilation may also leave an imprint. Therefore, resolving the components of the IGRB is... More »
20160516 May 16, 2016, 2:00 pm Searching for Dark Matter with Sounding Rockets High-resolution X-ray spectrometers onboard suborbital sounding rockets can search for dark matter candidates that produce X-ray lines, such as decaying keV-scale sterile neutrinos. Even with exposure times and effective areas far smaller than XMM and Chandra observations, high-resolution, wide field-of-view observations with sounding rockets have competitive sensitivity to decaying sterile neutrinos. We analyze a subset... More »
20160523 May 23, 2016, 2:00 pm Simulations of Strong Gravitational Lensing Gravitational lensing is one of the most powerful tools for investigating the dark side of the Universe. Strong gravitational lensing in particular provides a unique probe of the cores of massive dark matter halos. However, understanding this phenomena based upon observational data alone is complicated; high-fidelity simulations are required for robust cosmological interpretations. To fulfill... More »
20160523 May 23, 2016, 2:00 pm Simulations of Strong Gravitational Lensing Gravitational lensing is one of the most powerful tools for investigating the dark side of the Universe. Strong gravitational lensing in particular provides a unique probe of the cores of massive dark matter halos. However, understanding this phenomena based upon observational data alone is complicated; high-fidelity simulations are required for robust cosmological interpretations. To fulfill... More »
20160606 June 6, 2016, 2:00 pm Galaxy Cluster Cosmology with the South Pole Telescope Measurements of the abundance of galaxy clusters are an established cosmological probe and a promising tool for measuring the properties of dark energy and cosmic structure formation. To achieve the required level of accuracy, a clean survey selection and robust mass calibration from various observables is crucial. In this talk, I will review the cluster... More »
20160627 June 27, 2016, 2:00 pm Interpreting Observations of Galaxy Cluster Outskirts A variety of astrophysical processes affect the evolution of the intracluster medium (ICM) and corresponding observational signatures. While gas in the cluster core is most sensitive to cooling and feedback processes, gas in cluster outskirts is most sensitive to physical processes driven by accretion. I will present cosmological simulations of galaxy cluster formation that follow... More »
20160718 July 18, 2016, 2:00 pm Observations and Simulations of Galaxy Clusters: Cluster Radio Galaxies and their Implications on SZE Signal, Simulated Pressure Profiles and SZE Mass-Observable Relation We study the overdensity of point sources in the direction of X-ray-selected galaxy clusters from the Meta-Catalog of X-ray detected Clusters of galaxies (MCXC; ⟨z⟩ = 0.14) at South Pole Telescope (SPT) and Sydney University Molonglo Sky Survey (SUMSS) frequencies. Flux densities at 95, 150 and 220 GHz are extracted from the 2500 deg2 SPT-SZ... More »
20160815 Aug. 15, 2016, 2:00 pm The multiple effects of AGN feedback in galaxy clusters TBA
20160912 Sept. 12, 2016, 2:00 pm Scintillating bubble chambers: Results from a 35-gram prototype xenon bubble chamber In both direct WIMP dark matter search and coherent neutrino-nucleus elastic scattering experiments, discriminating low-energy nuclear recoils from all the other backgrounds is the key to detector performance. The bubble chambers developed by the PICO collaboration for dark matter detection feature both unmatched electron-recoil background rejection and the unique ability to work with a variety... More »
20160919 Sept. 19, 2016, 2:00 pm Neutrino Decay and Non-Unitary Effects in Neutrino Oscillations Discussion on current bounds on the neutrino lifetime, along with a more general parameterization of “general decay” effects in neutrino flavor oscillation.
20160926 Sept. 26, 2016, 2:00 pm Early Reionization Science from 21cm Experiments and the Path Towards a New Cosmological Probe 21 cm cosmology — the concept of using radio telescopes to observe the highly redshifted 21 cm line of neutral hydrogen on cosmological scales — is a field on the verge of a breakthrough.   The first generation of 21 cm cosmology experiments (LOFAR, MWA, and PAPER, among others) have been operating for several years,... More »
20160926 Sept. 26, 2016, 2:00 pm Early Reionization Science from 21cm Experiments and the Path Towards a New Cosmological Probe 21 cm cosmology — the concept of using radio telescopes to observe the highly redshifted 21 cm line of neutral hydrogen on cosmological scales — is a field on the verge of a breakthrough. The first generation of 21 cm cosmology experiments (LOFAR, MWA, and PAPER, among others) have been operating for several years, and... More »
20161010 Oct. 10, 2016, 2:00 pm Searches for New Physics with X-ray data A discussion on searches for new physics using ultra-deep X-ray observations of the central Active Galactic Nucleus of the Perseus galaxy cluster. We find two anomalies at high significance that we are unable to account for through conventional instrumental or astrophysical processes. I will outline interpretations of these anomalies from axion-photon mixing and from a... More »
20161017 Oct. 17, 2016, 2:00 pm Soft Limits, Asymptotic Symmetries and Inflation in Flatland There has been much recent interest in soft limits, both of flat space S-Matrix elements and of cosmological correlation functions. We will discuss the physics probed by soft limits in cosmology and explore the connection between cosmological soft theorems and asymptotic symmetries. These ideas will be illustrated by a simple example: inflation in 2+1 dimensions.
20161031 Oct. 31, 2016, 2:00 pm Recent Results from the PandaX- II experiments The Particle and Astrophysical Xenon (PandaX) project is a series of xenon-based ultra-low background experiments in the China JinPing Underground Laboratory (CJPL) targeting the unknown physics of dark matter and neutrinos. The first and second stage experiments (PandaX-I and II) both utilize dual-phase xenon time projection chamber (TPC) to carry out direct search for the... More »
20161107 Nov. 7, 2016, 2:00 pm Baryon Component Covariance and Stacked Spectroscopic Masses of Galaxy Clusters This talk will cover recent improvements to the characterization of the cosmic population of massive halos. After briefly reviewing an underlying statistical model for multi-property counts and conditional statistics, I will present preliminary observational confirmation of the “closed box” baryonic nature of massive halos predicted by simulations, then follow up with total mass scaling relations... More »
20161114 Nov. 14, 2016, 2:00 pm Recent Results from APTpol:CMB Polarization on Small (and Large) Scales The temperature and polarization of the cosmic microwave background (CMB) have been measured in exquisite detail by space-based probes such as WMAP and Planck over the full sky on large and intermediate scales. However, a healthy community of ground-based and balloon-borne experiments continue probing the CMB at both large and small scales with ever higher... More »
20161121 Nov. 21, 2016, 2:00 pm Accelerating the Search for Dark Matter Axions with Quantum Technology The axion is a hypothetical dark matter particle and many searches rely on its presumed coupling to electromagnetism. Indeed, these experiments amount to looking for an excess of microwave photons in a cryogenic microwave cavity. If all sources of technical noise can be tamed, the sensitivity is ultimately limited by fundamental quantum fluctuations of the... More »
20161128 Nov. 28, 2016, 2:00 pm Search for Dark Matter in Terms of Dark Bound States Understanding the nature of dark matter is an open question of central importance to particle physics and cosmology. In this talk, I discuss a model where the dark matter is a fermion charged under a dark U(1) gauge symmetry and its interactions are mediated by a massive dark photon. I will summarize the current status... More »
20161205 Dec. 5, 2016, 2:00 pm A Monodromy from London A description of large field inflation in terms of a dual massive gauge theory
20161212 Dec. 12, 2016, 2:00 pm New Directions in Dark Matter Detection Observational bounds currently permit the existence of a large number of dark matter candidates, ranging from ultra-light axions with masses ~ 10^(-22) eV to MACHOs with mass as large as 10^(24) gm. It is important to develop experimental methods to constrain this vast range of parameters. In this talk, I will describe new experimental methods... More »