Events

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Dimitri Mawet: Imaging other worlds

April 29, 2016, 3:30 PM - 4:30 PM

Title: Imaging other worlds

Speaker:Dimitri Mawet, Caltech


Abstract: Thousands of exoplanets have been discovered over the past 20 years. We learned that our solar system is just one example among a mind-boggling variety of architectures: from circumbinary exoplanets, systems with tightly packed inner planets, water-worlds, potential Earth twins, super-Earths, sub- and super-Neptunes, evaporating comet-like planets, planets with giant rings, hazy hot Jupiters all the way to extremely long-period lonely massive objects looking more like failed stars than giant planets. The majority of these planetary systems have been detected by indirect techniques, looking for instance at tiny variations in their host star’s motion and/or brightness. These techniques have ushered in an entirely new branch of astrophysics called comparative exoplanetology, putting the solar system and its planets into a universal perspective. In this talk, I will focus on high contrast imaging, using a slew of state-of-the-art facilities including current large and future extremely large ground-based telescopes as well as dedicated space-based platforms currently in the works. Beyond taking striking pictures, high contrast imaging is the only technique that promises to yield the most detailed measurements of distant worlds, revealing amazing details about their diversity and intimate architecture.

Host: Mel Ulmer

Speaker Schedule

Keywords: Physics, Astronomy, colloquium


Title:  The Stellar Ultrasound: How Asteroseismology Revolutionized Our
Understanding of Stellar Interiors


Speaker: Matteo Cantiello, Kavli Institute for Theoretical Physics


Host: Sourav Chatterjee

Abstract: Internal rotation and magnetism are key ingredients that largely affect explosive stellar deaths (Supernovae and Gamma Ray Bursts) and the properties of stellar remnants (White Dwarfs, Neutron Stars and Black Holes). However, the study of these subtle internal stellar properties was limited to very indirect proxies. In the last couple of years, new exciting asteroseismic results have been obtained by the Kepler satellite. Among these results are 1) the direct measure of the degree of radial differential rotation in many evolved low-mass stars, and 2) the detection of strong (>10^5 G) internal magnetic fields in the cores of thousands of red giant stars. I will explain how asteroseismology is able to probe rotation and magnetism in the internal regions of red giant stars. I will then show how these asteroseismic observations can now be used to test different mechanisms for angular momentum transport and to study the evolution of internal magnetism in stars. I will conclude with a brief discussion of the important consequences of these recent discoveries.

 

 

 

 

 

Keywords: Physics, Astronomy, Astrophysics


Title: Our Increasingly Molecular Universe as Revealed by Radio Astronomy with Laboratory Spectroscopy

Speaker: Lucy Ziurys, University of Arizona

Abstract: Radio astronomy over the past 40 years has revealed regions of interstellar space that are, quite surprisingly, rich in molecular material. Over 160 different chemical compounds have now been identified in interstellar gas, most of which contain carbon. While most of these molecules contain less than 15 atoms, recent discoveries of the fullerenes C60 and C60+ have challenged our notion of the degree of chemical complexity that exists in interstellar space. If C60 is present, what about other carbon clusters, nanostructures, or even biological molecules? Furthermore, molecular material is now appearing in some of the most extreme interstellar environments, such as near dying white dwarf stars or at the edges of our Galaxy. A picture is now emerging of a truly molecular universe. The extent of what can be learned, however, is limited by laboratory spectroscopy, which produces the crucial “fingerprint” for astronomical observations. Such experimental work involves very high sensitivity millimeter/sub-mm and THz spectroscopic techniques, coupled with unusual gas-phase synthetic methods with lasers, electrical discharges, and supersonic expansions. This talk will give an overview of our current understanding of the unexpected molecular universe, as learned from radio astronomy, and the challenges of laboratory work in helping to unravel its secrets.

 

 

Keywords: Physics, Astronomy

 


Title: The role of long-range strain interactions in perovskite metal-insulator transitions


Speaker: Dr. Richard Brierley, Yale University


Abstract: Metal-insulator transitions in manganite and nickelate perovskites depend on the competition between the electron kinetic energy, which favors the metallic phase, and the electron-phonon coupling and Coulomb interaction, which favor localization. The perovskite crystal structure consists of corner-sharing octahedra, which, depending on the chemical composition, can be tilted relative to each other by up to 15 degrees. This is accompanied by changes in the metal-insulator transition temperature over 600K. The significant change in transition temperature is commonly attributed to electronic effects but this relies ignores phonons, which are known to play an important role in the transition. We study how phonon-mediated long-range interactions are changed by the octahedral tilting. Using a simple statistical mechanical model we demonstrate that these changes can lead to variations in the transition temperature similar to those observed in both the manganites and nickelates.

 

Keywords: Physics, Astronomy, CMP


Title: Studying Electron Tunneling into Insulators: Observation of a Long-Range Ordered “Electron Crystal” in a Two-Dimensional Electronic System

Speaker: Ray Ashoori, MIT


Abstract: In a system of free electrons, both the Coulomb repulsion and quantum kinetic energies diminish as the electron density is decreased. Since the kinetic energy diminishes faster than the Coulomb energy, it becomes energetically favorable for electrons to localize into a crystal known as a “Wigner Crystal". In the case of 2D systems, applying a quantizing magnetic field favors crystal formation by further freezing out the kinetic energy into Landau levels. Theory predicts that a Wigner crystal of quasiparticles in a Landau level exists near integer quantum Hall states as an insulating phase with an expected transition temperature in the range of a few hundred millikelvin or below. As the state in insulating, it is very difficult to probe it. Using a refined pulsed tunneling method, capable of probing insulating phases, we are able to measure tunneling current directly into the electronic crystal. I will present high-resolution tunneling measurements that reveal very sharp structure arising from the vibrational spectrum of the spatially ordered electronic structure. This observation conclusively demonstrates the existence of a Wigner Crystal with long correlation length and opens the door to using tunneling to probe and detect a wide variety of ordered electronic phases.

Host: Anupam Garg

Speaker Schedule

Keywords: Physics, Astronomy, colloquium


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Kang-Kuen Ni: Ultracold Molecular Assembler

May 10, 2016, 2:00 PM - 3:00 PM

Title: Ultracold Molecular Assembler 

Speaker: Kang-Kuen Ni, Harvard University

Abstract: Single molecule detection and manipulation have been powerful approaches to study systems without ensemble averaging. We take this inspiration to study chemistry and physics at the ultracold regime where low entropy gas could be prepared and interactions between particles could be individually tuned. To assemble ultracold molecular system from single atoms and single molecules, our approach relies heavily on high fidelity internal and external quantum-state controls of atoms and molecules. I will report on our progress toward assembling a configurable molecular array atom-by-atom.

Keywords: Physics, Astronomy, colloquium


Title: The Discovery Potential of Pulsar Timing Arrays

Speaker: Xavier Siemens, University of Wisconsin-Milwaukee

Abstract: 

For over a decade, the North American Nanohertz Observatory for Gravitational
Waves (NANOGrav) has been using the Green Bank and Arecibo radio telescopes to monitor millisecond pulsars. NANOGrav aims to directly detect low-frequency gravitational waves which cause small changes to the times of arrival of radio pulses. In this talk I will discuss the work of the NANOGrav collaboration and our sensitivity to gravitational waves from astrophysical sources. I will show that a detection is possible in the next few years.

 

Host: Vicky Kalogera

Keywords: Physics, Astronomy, colloquium

 


Pat Stollenwerk
Title TBA

Abstract: TBA
 

Cody Dirks
Title TBA

Abstract: TBA

 

Pizza will be available.


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Bob Buhrman: TBA

May 13, 2016, 3:30 PM - 4:30 PM

Title: TBA

Speaker: Bob Buhrman, Cornell University


Abstract: TBA

Host: Bill Halperin

Speaker Schedule

Keywords: Physics, Astronomy, colloquium


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TEACHx

May 16, 2016, 8:30 AM - 3:30 PM

Andy Rivers will present at TEACHx on May 16.

TEACHx is a celebration of experiments in teaching and learning at Northwestern University. Each presenter will summarize the teaching experiment they performed this academic year; the innovations range from new forms of assessment to the implementation of a new technology to the creation of new materials for their students.


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Wei-Chih Huang: TBA

May 16, 2016, 4:00 PM - 5:00 PM

Title: TBA

 

Speaker: Wei-Chih Huang, Dortmund
 

Abstract: TBA


Title: The Extraordinary Diversity of Super-Earth Mass Planets Revealed with Transit Timing


Speaker: Daniel Jontof-Hutter, Pennsylvania State University


Host: Sourav Chatterjee

Abstract:  

Transit timing variations (TTV) in multi-transiting systems enables precise characterizations of low-mass planets and their orbits. The increase in sensitivity to planetary mass with orbital distance with TTVs provides a sample that complements low mass radial velocity detections, by characterizing transiting planets with lower incident fluxes. This pushes exoplanet characterization to the regime of sub-Earth size planets and out to Venus-like distances. Here we demonstrate the astonishing diversity in the density of super-Earth mass planets. We summarize these and other contributions to exoplanet science from TTVs.

 

 

 

 

 

 

Keywords: Physics, Astronomy, Astrophysics


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Charles Bennett: The Standard Model of Cosmology

May 18, 2016, 12:00 PM - 1:00 PM

Title: The Standard Model of Cosmology

Speaker: Charles Bennett, Johns Hopkins University

Abstract: The Standard Model of Cosmology appears to be simple, but it can also be viewed as strange and not well-understood. After all we have learned during the current “golden age of cosmology” we are confronted by significant questions. I will briefly review the development of the Standard Model of Cosmology with a concentration of the role of the Cosmic Microwave Background (CMB) in probing the universe. I will discuss current observational constraints on the model, and address consistency both between the sets of measurements and between measurements and the Model. After discussing successes and challenges of the Standard Model, I will look forward to what we can hope to learn from measurements coming in the near future.

 

 

Keywords: Physics, Astronomy

 


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Carter Hall : TBA

May 20, 2016, 3:30 PM - 4:30 PM

Title: TBA

Speaker: Carter Hall, Maryland University


Abstract: TBA

Host: Eric Dahl

Speaker Schedule

Keywords: Physics, Astronomy, colloquium


Title: Setting the Stage for the Era of Gravitational Wave Discovery


Speaker: Wen-fai Fong, University of Arizona


Host: Vicky Kalogera, Niharika Sravan, and Fani Dosopoulou

Abstract: 

The first advanced gravitational wave detectors are newly operational and have brought of the most anticipated discoveries of the century: the direct detection of gravitational waves. The premier gravitational wave sources are the mergers of two compact objects, involving either two neutron stars or a neutron star and a black hole. While the gravitational wave signal will give insight to the basic properties of compact objects, a coincident detection at electromagnetic wavelengths will significantly leverage the event by providing precise sky localization and an association to a galaxy. The main challenge will be how to identify the correct electromagnetic counterpart amidst an otherwise dynamic sky. In this talk, I discuss ongoing efforts to characterize the electromagnetic signatures from compact object mergers. In particular, I present observational evidence linking mergers to two distinct counterparts: short-duration gamma-ray bursts (GRBs) and long-lived transients powered by the radioactive decay of heavy elements (kilonovae). I then address how these results can help us develop observing strategies for this revolutionary era of gravitational wave discovery.

 

 

BA

 

 

 

 

Keywords: Physics, Astronomy, Astrophysics


Speakers TBA

 

Pizza will be available.


P&A Complex Systems Seminar

Featured Speaker

 

Douglas Robertson

Fellow emeritus, Cooperative Institute for Research in Environmental Sciences (CIRES)
former Adjunct professor, Dept. of Geological Sciences
University of Colorado, Boulder

 

Title A Quantitative Information-Theoretic Approach to the Philosophy of Science

Abstract 

The computer revolution is arguably the most important event in the history of the human race. I will use quantitative information-theoretic ideas to argue that the computer revolution marks not only the beginning of civilization, but also the beginning of both science and mathematics, all of which are information-limited and none of which can be done effectively without computers. But perhaps the most interesting feature of the computer revolution is that it also marks the beginning of philosophy. Steven Weinberg famously complained about the “unreasonable ineffectiveness of philosophy.” But with information theory we can make philosophy quantitative for the first time, much as Newton’s calculus made physics quantitative for the first time. Classical philosophy of science asked questions of the form: “What do we know and how do we know it?” questions that lack effective and useful answers. With a quantitative philosophy we can instead ask questions such as: “How much do we know? How much can we know? How much do we need to know?” These are questions that actually have answers, quantitative answers that provide insights into topics as varied as Goedel’s incompleteness theorem, Theories of Everything (TOE’s) in physics and mathematics, the nature of scientific methods, and even questions related to consciousness and free will, all of which can be usefully examined as quantitative questions in information theory.


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Roger Melko: TBA

May 27, 2016, 3:30 PM - 4:30 PM

Title: TBA

Speaker: Roger Melko, U Waterloo


Abstract: TBA

Host: David Schwab

Speaker Schedule

Keywords: Physics, Astronomy, colloquium


Title: The Birth and Growth of Supermassive Black Holes: Coming of Age with Space Telescope Imaging Spectrograph Surveys


Speaker: Jonathan Trump, Pennsylvania State University


Host: Daniel Angles-Alcazar

Abstract: The past 20 years have revealed that supermassive black holes play an essential role in the formation and growth of galaxies. Every massive galaxy hosts a supermassive black hole in its center, and the black hole's mass is tightly coupled to the mass of the galaxy. Remarkably, the black hole - galaxy connection has been "self-maintained" from the adolescent universe (z~2) to the current epoch, from Milky-Way progenitors to massive cluster galaxies, governed by coupled black hole accretion and galaxy star formation. Until recently the "chicken-or-egg" birth of galaxies and supermassive black holes has remained mysterious. I will show how imaging spectrograph surveys with the Hubble Space Telescope are revolutionizing our understanding of black hole formation, revealing a fossil record of massive black hole seeds in tiny galaxies. Similar imaging spectrographs are flagship survey instruments on the upcoming JWST, WFIRST, and Euclid space telescopes, enabling an exciting future for understanding the birth of primordial galaxies and their black hole seeds.

 

Keywords: Physics, Astronomy, Astrophysics

Department Conference Room Calendars

Tech F160    Tech F210     Dearborn 23