Academic year 2014-2015 Colloquium Series - Preparation Page
Autumn 2014

Committee: Luca Grandi, Young-Kee Kim (chair), Dam Son, David Schuster

Colloquium at 4pm, followed by a reception (KPTC 206)

Winter 2015 program: go to this page
Spring 2015 program: go to this page

October 2, 2014
  1. Title: The proton and the future of particle physics
  2. Speaker: Richard Hill, the University of Chicago
  3. Abstract: The venerable proton continues to play a central role in fundamental particle physics. Neutrinos scatter from protons in neutrino oscillation experiments, Weakly Interacting Massive Particles (WIMPs) are expected to scatter from protons in dark matter searches, and electrons or muons are bound by protons in precision atomic spectroscopy. Our understanding of the proton is an obstacle to the success of next generation experiments hoping to discover CP violation in the lepton sector and determine the neutrino mass hierarchy, discover the particle nature of dark matter, or reveal new interactions such as those that violate lepton universality. In this talk I present (i) an overview of the current state of knowledge in the neutrino sector, and theoretical advances that will determine a crucial missing ingredient in the predicted signal process of neutrino-nucleus scattering at a Long Baseline Neutrino Facility (ii) the first complete calculation of the scattering cross section of a proton on a static electroweak source, which determines WIMP-nucleus scattering rates at underground direct detection experiments and (iii) the status of the proton radius puzzle, whose most "mundane" resolution requires a 5 standard deviation shift in the value of the Rydberg constant. I describe how each of these problems has spurred the development of powerful new methods in effective quantum field theory.
  4. Faculty Host: Carlos Wagner
October 9, 2014
  1. Title: A colloidal dance: synchronizing motion of brownian particles
  2. Speaker: Tom Witten, University of Chicago (website)
  3. Abstract: Watch a small flake of plastic gradually sink in a glass of water. The asymmetric flake pivots into a preferred orientation and then rotates steadily as it sinks. The origin of this rotational response to gravity is independent of length scale; thus it applies to microscopic colloidal objects as well. Analogous responses occur under other forces, eg from electric fields. The response is governed by a 3x3 matrix called the twist matrix that depends on the object's shape and its mass distribution. The twist matrix controls the motion in much the same way as the (symmetric) inertia tensor controls the free tumbling motion of a body. However, the twist matrix gives a richer response because it is not symmetric. In this talk we explore ways to use this rotational response to organize a sample of objects so that they all rotate in unison, with the same orientation. This complete orientation can be achieved without using interaction between the particles; instead we exploit the transient pivoting response before the object settles into a fixed rotational axis. We demonstrate two types of programmed, time-dependent forcing that bring a set of randomly-oriented particles into a common orientation. The first is a simple alternating rocking motion. The second is a rotating force analogous to the rotating magnetic field in an NMR device. Once oriented, the objects must respond identically to further forcing; they translate and rotate in unison.
  4. Faculty Host: David Schuster
October 16, 2014
  1. Title: The future of high-energy colliders (experimental particle physics)
  2. Speaker: Fabiola Gianotti, CERN
  3. Abstract: Recent results from the LHC, including the groundbreaking discovery of the Higgs boson, and other facilities have had a significant impact on the landscape of particle physics. However, many crucial, exciting questions remain unanswered. The strategy to address them is briefly summarised. The expected role and options for future high-energy colliders, historically one of the main tools for exploration, are discussed.
  4. Faculty Host: Young-Kee Kim
  5. Visiting Period: October 16 (Thursday) - 17 (Friday)
  6. Friday, October 17
    • 9:00am-10:00am    Breakfast meeting with physics majors
    • 11:30am-1:30pm    Women in Science Conversation with PSD faculty, postdocs and graduate students
    • 2:00pm-3:00pm      Round-table discussions with ATLAS junior scientists (postdocs and students)
    • 3:00pm-4:00pm      Round-table discussions with ATLAS senior scientists
    • 4:30pm-8:30pm      Mini phenomenology-experiment workshop for LHC Run II (dinner included)
October 23, 2014
  1. Title: Frontiers of Fundamental Physics
  2. Speaker: David Gross, UCSB
  3. Abstract: At the frontiers of physics we search for the principles that might unify all the forces of nature and we strive to understand the origin and history of the universe. In this lecture I shall describe some of the questions that we ask and some of the proposed answers. I shall also discuss what it might mean to have a final theory of fundamental physics and whether we are capable of discovering it.
  4. Faculty Host: Young-Kee Kim
  5. Visiting Period: Evening, Oct. 22 - Afternoon, Oct. 23
October 30, 2014
  1. Title: New Exciting Approaches to Scattering Amplitudes
  2. Seaker: Henriette Elvang, University of Michigan
  3. Abstract: The scattering cross-section is the key observable in particle physics experiments, such as the Large Hadron Collider at CERN. In quantum field theory, the cross-section is expressed in terms of the scattering amplitude, which traditionally is calculated as a sum of Feynman diagrams. When many particles are involved in a process -- as for example in multi-gluon scattering -- the Feynman diagram approach becomes very difficult, even at leading order (tree-level). In recent years, it has been realized that amplitudes possess a very interesting mathematical structure that can be exploited to find more efficient calculational methods. Surprisingly, it also turns out that some amplitudes have interpretations as volumes of certain abstract geometric objects. Not assuming prior knowledge of quantum field theory or Feynman rules, I will review the background and recent progress in this exciting field of research.
  4. Faculty Host: Jeff Harvey and Daniel Holz
  5. Visiting Period: October 30 (Thursday) - October 31 (Friday)
November 6, 2014
  1. Title: The Hunt for Millisecond Pulsars
  2. Speaker: Vicky Kaspi, McGill University
  3. Abstract: The continued search for more of nature's most perfect clocks --millisecond radio pulsars -- has recently taken a more urgent turn given the potential of these objects to detect and study gravitational waves from a variety of potential sources, most likely merging supermassive black holes. Additionally, their discovery has invariably led to surprising and interesting astrophysical results as novel binary MSPs are revealed and studied. Such bonuses include constraints on the equation-of-state of dense matter, tests of theories of gravity, as well as surprises in binary evolution. Most recently, the hunt for millisecond pulsars has led to a new, serendipitous discovery, the so-called `Fast Radio Bursts,' few-ms single pulses of unknown origin, from apparently cosmological distances. Here I describe ongoing millisecond pulsar searches and their recent bounty, as well as plans for future study of these objects, as well as of single-burst sources.
  4. Faculty Host: Angela Olinto and Don Lamb
November 13, 2014
  1. Title: Granular Streams
  2. Speaker: Heinrich Jaeger, University of Chicago
  3. Abstract: Streams of accelerated particles are important tools for probing atomic or molecular collision processes. In this talk I will show how particle streams also offer unique opportunities to investigate interactions in granular media, where the particles are much more macroscopic. Motivated by experiments on dense jets of particles that exhibit liquid-like breakup into droplets, we developed an experiment to investigate the evolution of a stream of granular media accelerated by gravity. This has opened up possibilities to resolve minute inter-particle forces and gain direct access to dynamic collision processes at the single particle level. The results have provided a host of new insights into the fundamental processes by which athermal particle aggregates break apart, they have revised our understanding of the origin of collisional charging in dielectrics, and they have provided a first glimpse at the creation of ‘granular molecules’ from individual particles via collide-and-capture events.
  4. Faculty Host: Sidney Nagel
November 20, 2014
  1. Title: Science at the Timescale of the Electron: Tabletop X-ray Lasers and Applications in Nanoscience and Nanotechnology
  2. Speaker: Margaret Murnane, University of Colorado, Boulder
  3. Abstract: Ever since the invention of the laser 50 years ago, scientists have been striving to extend coherent laser-like beams into the X-ray region of the spectrum. Very recently, we used tabletop mid-infrared femtosecond lasers to achieve this goal, and create bright X-ray beams at wavelengths spanning from the UV to <10Å (T. Popmintchev et al., Science 336, 1287, 2012). The X‑ray supercontinua that are generate represent a coherent version of the Rontgen X-ray tube in the soft X-ray region. X-rays are powerful probes of the nanoworld. They penetrate thick samples and can image small objects with spatial resolution near the wavelength limit. Interest in this research area is booming worldwide, because of the critical need for better tools for a host of applications in science and technology. Moreover, the limits of this new light source are not yet known.
  4. Faculty Host: Jon Simon
  5. Visiting Period: November 20 (Thursday)
  6. Comments: Argonne Colloquium on Friday, November 21
December 4, 2014
  1. Title: Building a quantum computer using silicon quantum dots.
  2. Speaker: Sue Coppersmith, University of Wisconsin, Madison
  3. Abstract: It has been shown theoretically that by exploiting the nature of quantum physics, quantum computers can solve certain computational problems much more efficiently than classical computers can. To build a quantum computer that is large enough to provide such an advantage, fundamental physics advances are required. This talk will discuss the challenges involved in building a large-scale quantum computer as well as progress that we have made in developing a quantum computer using quantum dots in silicon/silicon-germanium heterostructures.
  4. Visiting Period: December 2 (Tuesday) - 5 (Friday)
  5. Schedule
    • Tuesday, Dec. 2: Women-in-Science event (11:30 am - 12:50 pm) at GCIS 301W - hosted by Young-Kee Kim
    • Wednesday, Dec. 3: JFI seminar (12:15 - 1:30 pm) at KPTC 206 - hosted by Leo Kadanoff
    • Thursday, Dec. 4: Physics colloquium (4 - 5pm) at KPTC 106 and reception (5 - 6pm) at KPTC 206
December 5, 2014
  1. Title: Daya Bay neutrino experiment and the future
  2. Speaker: Yifang Wang, Institute of High Energy Physics, Beijing, China
  3. Abstract: Recently reactor neutrino experiments have made important contributions to the neutrino oscillation. I will introduce the Daya Bay experiment which observed for the first time the neutrino mixing angle, theta-13, with a statistical significance of 5.2 sigma. The concept of the experiment, the detector construction and data analysis will be described. The next generation reactor neutrino experiment, JUNO, is about to start the construction in China. This experiment can determine the neutrino mass hierarchy and improve the precision of neutrino mixing parameters by one order of magnitude. It is also sensitive to supernova neutrinos, geoneutrinos and many others. I will also describe a new idea of neutrino beam for CP phase determination.
  4. Faculty Host: LianTao Wang / Young-Kee Kim
  5. Visiting Period: December 5 (Friday)
  6. Schedule