Physics and Astronomy - Colloquium Schedule

Colloquia are presented on Thursdays at 3:45 pm in Room 245 of the Physics Building, unless otherwise noted.

Refreshments are served at 3:30 pm.



2018-2019 Schedule


WINTER 2019



Friday, January 11, 2019

NOTE SPECIAL DAY AND TIME:  FRIDAY at 3:15 PM

     Speaker: Ryan Hayes, University of Michigan

     Title: Developing Multisite lambda Dynamics for Computational Protein Design

     Abstract:  Protein design holds great promise in green chemistry, biotechnology,
and medicine. Current computational protein design methods have been
widely successful, but sometimes fail due to insufficient accuracy.
Alchemical free energy methods based in statistical mechanics offer a
more accurate alternative to current protein design methods, and have
already found broad use in computer-aided drug design. Multisite
lambda dynamics (MSLD) is an emerging alchemical method that can
efficiently characterize combinatorial chemical spaces from multiple
perturbations, which makes it uniquely suited for protein design,
where design spaces routinely exceed 10^100 sequences. In this talk I
will highlight recent developments that enable MSLD to be applied to
protein design, including repurposing Potts models from big data
applications in proteomics to expand the sequence spaces that can be
characterized by MSLD. Two protein design projects will be presented:
a proof-of-concept, retrospective study of T4 lysozyme and a
prospective study of ribonuclease H chimeras.


Tuesday, January 15, 2019

NOTE SPECIAL DAY AND TIME:  TUESDAY at 3:00 PM

     Speaker: Lior Shamir, Lawrence Institute of Technology

     Title: Data science in the era of astronomical digital sky surveys

     Abstract:  Digital sky surveys have been becoming increasingly more important in the field of astronomy, and that trend is bound to continue. As these sky surveys are becoming more powerful, and future ventures such as the Large Synoptic Survey Telescope (LSST) are expected generate the world's largest scientific databases, they also introduce new challenges in the analysis of these large and complex data, and turning them into knowledge and scientific discoveries. Data science is a new discipline that combines elements from computer science, applied math, and statistics to turn data into insights. In this presentation I will describe novel methodology designed to close the gap between the existing algorithmic foundations and the needs of digital sky surveys. Such methodology can be used to turn raw astronomical data into structured data products, detect rare astronomical objects, and analyze the structure of the local universe in a manner that was not possible in the pre-information era. I will also show how the methodology leads to scientific discoveries in other disciplines by profiling physiological processes, identifying sources of clinical conditions, characterizing the communication of animals, and analyzing human creations such as music and visual art in a quantitative manner.


Thursday, January 17, 2019

NOTE SPECIAL TIME:  10:30 AM

     Speaker: Nicolas Ross, University of Edinburgh

     Title: Contemporary Astrophysics and Big Data: Quasars as Tools and Laboratories for 2020 Cosmology

     Abstract:  Contemporary astrophysics, especially in the field of observational cosmology, is "Big Data". Cosmology surveys such as the Sloan Digital Sky Survey (SDSS) and the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) are the forerunners to the Dark Energy Spectroscopic Instrument (DESI) and the Large Synoptic Survey Telescope (LSST). DESI and LSST will deliver very large datasets probing the largest volumes of the Universe ever mapped. These datasets are geared towards gaining an understanding of Dark Matter and Dark Energy.

In this talk, I will explain how quasars — accreting supermassive black holes at the centers of galaxies — have become key tools and laboratories for extragalactic cosmological investigations. I will discuss some of the challenges and opportunities in an astronomical big data and data science setting, outlining the key paths forward and how the field will make substantial progress.

I have recent and direct experience for developing algorithms and code for analysis of large time-series data sets. These types of data science problems and solutions will be necessary for engaging and using all of the available survey and data products to maximize scientific output and directly address our key scientific questions on the nature of black holes, accretion physics, dark matter and dark energy.


Thursday, January 17, 2019

     Speaker: Yacine Mehtar-Tani, Brookhaven National Laboratory

     Title: Novel aspects of QCD dynamics at high energy:  Jet evolution in the quark-gluon plasma and wave turbulence

     Abstract:  The phenomenon of jet quenching in ultra-relativistic heavy ion collisions reveals the effect of substantial final state interactions that cause QCD jets to lose energy to the quark-gluon plasma (QGP). The energy spectrum of jet constituents exhibits a scaling behavior, akin to wave turbulence,  characterized by a constant flow of energy from the forward energetic patrons towards low momentum gluons down to the temperature of the plasma. I will discuss in this talk how jet energy is dissipated in QCD plasmas and review recent theoretical developments and their phenomenological implications in the study of jet structure in heavy ion collisions. 


Thursday, January 24, 2019        CANCELLED

     Speaker: Kate Scholberg, Duke University

     Title: Detecting the Tiny Thump of the Neutrino

     Abstract: Neutrinos interact only rarely with matter.   Coherent elastic neutrino-nucleus scattering (CEvNS) was first predicted in 1974; it's a process in which a neutrino scatters off an entire nucleus.  By neutrino standards, CEvNS occurs frequently, but it is tremendously challenging to see. The only way to observe it is to detect the minuscule thump of the nuclear recoil.  CEvNS was measured for the first time by the COHERENT collaboration using the unique, high-quality source of neutrinos from the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory.   This talk will describe COHERENT's recent measurement of CEvNS, the status and plans of COHERENT's suite of detectors at the SNS, and the physics we will learn from the measurements.


Friday, February 1, 2019

NOTE SPECIAL DAY AND TIME:  FRIDAY at 10:30 AM

     Speaker: Ioanna Zoi, University of Arizona

     Title: Design, Reengineering and Electric Field Calculations of Enzymes

     Abstract:  The details of how enzymes catalyze biological reactions remain elusive,  and progress towards understanding them is crucial for progress in protein design. The traditional static view of catalysis focuses on the electrostatic environment of the active site, but recently an emerging consensus stresses the importance  of fast protein motions that are coupled to the catalytic event. The femtosecond timescale of the chemical step in catalysis makes  direct experimental probing difficult.  We use Transition Path Sampling (a Monte Carlo method in trajectory space)  to computationally study the catalytic event in full atomistic detail.  In this talk, I will present recent computational work that  reveals how subpicosecond local catalytic site protein motions play a crucial role  in catalysis and how we used this information for enzyme design.


Tuesday, February 5, 2019

NOTE SPECIAL DAY AND TIME:  TUESDAY at 3:45 PM

     Speaker: Antonio Ruotolo, City University of Hong Kong

     Title: Optical excitation of spin-currents

     Abstract: The spin-Hall effect allows excitation of pure spin-currents, i.e. the flow of angular momentum without net charge transfer [1]. A less-explored way to generate a spin-current is through optical excitation of carriers at the interface between semiconductors and metals with large spin-orbit coupling.

Here we show that unpolarised light can excite a spin-current at the interface between an ultra-thin metallic film and a magnetic semiconductor. The excited electrons are spin-polarized because of ferromagnetic proximity effect. If the metallic film has a strong spin orbit coupling, a transverse voltage is generated because of inverse spin-Hall effect [2,3]. In addition, we found that the proximized metal shows an anisotropic magneto-resistance that is a function of the light intensity [4]. We named this effect photo-magnetoresistance.

If the semiconductor is non-magnetic while the metal is, photo-excited carriers are subject to spin-orbit coupling in the magnetic metal. A photo-induced anomalous Hall effect arises that can be used as a new magneto-metric technique to reconstruct the in-plane magnetization loop of metallic thin films [4,5]. By using nickel as a magnetic metal, we show that the voltage-loop in sweeping magnetic field of nickel thin films mimics the magnetization loop as measured by a magnetometer.

[1] S. O. Valenzuela and M. Tinkham, Nature 442, 176 (2006).
[2] E. Saitoh et al., App. Phys. Lett. 88, 182509 (2006).
[3] D. Ellsworth et al., Nat. Phys. 12, 861 (2016).
[4] D. Li and A. Ruotolo, Appl. Phys. Lett. 111, 182404 (2017).
[5] T. A. Fasasi, A. Ruotolo, et al, Appl. Phys. Lett. under review (2019).


Thursday, February 7, 2019

     Speaker: Qian Wang, Rice University

     Title: To cooperate or not to cooperate: Collective motions of motor proteins in intracellular transport

     Abstract:  Motor  proteins, also known as biological molecular motors, play the key role in intracellular transport. The transport process involves collective behaviors of motor proteins at different scales. On one hand, a motor protein needs to self-coordinate its two motor heads in order to maintain a processive stepping pattern on cytoskeletons; on the other hand, multiple motor proteins usually cooperate together to transport a single cargo. The molecular details of these phenomena remain not well understood. In this talk, I will describe my recent studies on two important motor proteins, cytoplasmic dynein and  kinesin, by multi-scale theoretical  methods. Combining  analytical modeling and molecular dynamic simulations, I elucidate the molecular mechanism of the interhead coordination in cytoplasmic dyneins, as well as the cooperativity between two mechanical coupled kinesins. These findings provide the structural basis to understand the collective behaviors of motor proteins, which facilitates the study of intracellular transport.


Thursday, February 12, 2019

NOTE SPECIAL DAY AND TIME:  TUESDAY at 3:45 PM

     Speaker: Joseph Sklenar, University of Illinois Urbana-Champaign

     Title: New Magnetic Orders, and Phase Diagram Exploration in Artificial Spin Systems

     Abstract:  One path towards realizing an artificial spin system involves nanostructuring thin magnetic films into single magnetic domain elements or islands.  In the simplest form, these islands behave as giant Ising (binary) spin states which can be mapped onto spin-lattice models.  The earliest example of such a nanomagnet system was the so-called artificial spin ice system, where an artificial spin system was designed to promote geometric frustration and simulate real spin ice materials.  However, as interest in artificial spin ice grew, other areas of inquiry developed.  Three areas of interest to me are: 1) What are the best strategies to thermally equilibrate artificial spin systems into true groundstates?  2)  Can we experimentally manipulate the microstate of an artificial spin system into any arbitrary state? 3)  Can artificial spin systems beyond the Ising models (Potts, Heisenberg) be fabricated?  Upon summarizing progress in these research directions, I will discuss my recent experimental results motivated by these interests.  I will describe a new artificial spin system where the quadrupole configurations of the system can order into different configurations when thermally active in the absence or presence of an external field.  These experiments allow us for the first time to map the phase diagram and study field-induced phase transitions in artificial spin ice-type systems.  I will conclude my talk discussing future directions where the disorder dimension of the phase diagram can be probed in a controllable manner so that a random bond Ising model, a precursor to an artificial spin glass, is realized.  I will also discuss a perspective where I envision artificial spin systems as a platform for neuromorphic computing.


Thursday, February 14, 2019

     Speaker: Van Ngo, Los Alamos National Lab

     Title: Molecular Dynamics Simulations: An Atomic-Resolution Microscope to Unravel Molecular Mechanisms of Biological Systems

     Abstract:  In this talk, I will present the latest state-of-the-art of using molecular dynamics (MD) simulations to probe protein complexes. I will show a Bird's-eye view of what MD modelling can do and will be able to achieve by solving Newton's equations for million- to billion-atom systems. I hope to convince you that the whole bold games for MD simulations might have been just getting started. As an example, I will demonstrate how a voltage-dependent anion channel (VDAC) "gates" via its N-terminal amino acids, and some key charged side-chains that could act like a switch between open and closed states for monitoring the translocation of metabolites ATP and ADP in and out of mitochondria. For VDAC, we collected hundred microseconds of data from Anton2 supercomputer, and identified for the first time what a closed state of VDAC would look like. In another example, I will show how an actin-bundling protein, L-plastin can also act like a switch upon the binding or unbinding of calcium ions. These types of protein switches are abundant in cellular systems. Particularly, L-plastin can influence T-cell motility and activation; thus, targeting the switching mechanism of L-plastin can be helpful to develop effective immunotherapeutics.


Tuesday, February 19, 2019

NOTE SPECIAL DAY AND TIME:  TUESDAY at 3:00 PM

     Speaker: Derek Meyers, UC Berkeley

     Title: Forging next generation materials through atomic layer engineering

     Abstract:  Throughout history, technological and scientific advancements have been driven by mankind's ability to craft the world around us into functional technologies. In this talk, we will explore one of the modern realizations of this rich tradition, creating artificial crystalline structures of complex oxides with unprecedented properties that promise next generation functionalities. Pulsed laser deposition allows stacking of single atomic layers of disparate materials with sharp interfaces and high crystalline quality. To directly probe these nanoscale interfaces, advanced synchrotron X-ray characterization will be introduced as a powerful tool for investigating the strongly entangled lattice, orbital, charge, and magnetic degrees of freedom exhibited by these artificial structures. Some of the fascinating physical phenomena derived from strongly correlated electrons, such as unconventional superconductivity and 2D magnetism, will be showcased as recent paragons of this growth and characterization methodology. In particular, the role of electron-phonon coupling in the recent SrTiO3-based superconductors and the magnetic behavior of isolated strongly spin-orbit coupled SrIrO3 layers will be discussed. We will conclude this talk with a discussion of the promising future applications for this class of materials, with an emphasis on topological phenomena and quantum information science.


Wednesday, February 20, 2019

NOTE SPECIAL DAY AND TIME:  WEDNESDAY at 3:45 PM

     Speaker: Halyna Hodovanets, University of Maryland

     Title: Tuning of magnetism in 4f-based correlated electron systems

     Abstract: Rare-earth elements in the intermetallic compounds display wealth of fascinating properties. Among these compounds, Ce- and Yb-based systems are of particular interest because they often show anomalous electronic and magnetic properties. The competition between Ruderman-Kittel-Kasuya-Yosida interaction and Kondo effect leads to variety of ground states including exotic magnetism and unconventional heavy-fermion superconductivity. The antiferromagnetic ground state of these compounds can be tuned through a quantum phase transition into a heavy-fermion state by chemical substitution, magnetic field and application of pressure. Heavy-fermion materials involve the dense lattice analog of single-ion Kondo effect and are often called Kondo lattice compounds. [1] The common knowledge is that the Kondo lattice state is easily suppressed once the Ce-sublattice is diluted with La. I will discuss La dilution of Kondo lattice CeCu2Ge2 as an example of chemical substitution tuning where we discovered remarkably low (only 9% of Ce) percolation limit for the Kondo lattice and single-ion Kondo effect. [2]

Most recently, rare-earth intermetallics were theoretically predicted to host new physics. Specifically, CeAlGe and PrAlGe were proposed as new potential candidates of Weyl semimetals that break both inversion and time-reversal symmetries. In this regard, I will present the first single crystal investigation of magnetic, thermodynamic and transport properties of CeAlGe and discuss whether CeAlGe fits this prediction. [3]

[1] S. Doniach, Physica B 91, 231 (1977)
[2] H. Hodovanets et al., Phys. Rev. Lett. 114, 236601 (2015)
[3] H. Hodovanets et al., Phys. Rev. B 98, 245132 (2018)


Thursday, February 21, 2019  

     Speaker: Yizeng Li, Johns Hopkins University

     Title: Hydraulic Resistance Accelerates Cell Migration through Water Flux

     Abstract: Cells in vivo live in diverse physical environments that provide mechanical cues for cells to deform, migrate, and carry out their biological function. For example, cell migration on 2D surfaces is mostly driven by forces from actin polymerization and focal adhesions, whereas cells in confined geometries can be driven by water permeation. I have developed a two-phase mathematical model that describes the motion of the cytosol and the actin-network components during cell migration. I explore the interplay of actin-driven and water-driven cell migration, and show that the former mechanism is important on 2D substrates while the later mechanism is more important in confined spaces. The transition from actin-driven to water-driven cell migration depends on the external hydraulic resistance, which varies with the mechanical properties of the external fluid and the geometry of the cell surroundings. On the experimental side, increasing the hydraulic resistance in the cell environment increases cell speed, as predicted by the model. In addition, perturbation of ion channels on the cell membrane or ionic contents in the cell medium leads to speed reduction. This work has implications on early embryonic development, morphogenesis, and cancer cell metastasis.


Tuesday, February 26, 2019

NOTE SPECIAL DAY AND TIME:  TUESDAY at 3:45 PM

     Speaker: Eric Arturo Montoya, University of California, Irvine

     Title: Planar Hall torque

     Abstract: Spin-orbit torques in bilayers of ferromagnetic (FM) and nonmagnetic (NM) materials create potential for energy efficient spintronic devices. Previously studied spin Hall [1] and Rashba [2] torques originate from spin-orbit interactions within the NM layer and at the FM/NM bilayer interface, respectively. In this talk, we report a SOT arising from planar Hall current in the FM material of the bilayer [3]. This planar Hall torque exhibits novel biaxial symmetry in the plane defined by the bilayer normal and the applied electric field and can act as positive or negative damping. The unusual symmetry of PHT can be deduced from the angular dependence of the planar Hall current in the FM layer and is distinctly different from the uniaxial symmetry of the spin Hall torque (SHT). We fabricate 40-50 nm wide nanowires from Al203(0001)/Ta(3.0 nm)/NM/FM/Ta(4.0 nm), where FM = [Co(0.85 nm)/Ni(1.28 Nm)]2/Co(0.85 nm) and NM=Au, Pd, or Pt. We characterize spin orbit torques by means of torque ferromagnetic resonance (ST-FMR) measurements. The antidamping component of the SOTs is deduced from the dependence of the ferromagnetic resonance linewidth ΔH on direct current density Jdc applied to the nanowire. We find that the magnitude of PHT is similar to that of the giant SHT of Pt and that strong PHT can be present in a system with negligibly small SHT (e.g. FM/Au). Finally, we demonstrate that the planar Hall torque is large enough to excite auto-oscillations of the FM layer, allowing one to create a planar Hall nano-oscillator [4,5]. The discovery of PHT [6] expands the class of materials for energy efficient manipulation of magnetization by giant SOTs.

[1] L. Liu, et al., Science 336, 555-558 (2012)
[2] I. M Miron. et al., Nature 476, 189-193 (2011)
[3] T. Taniguchi et al., Phys. Rev. Appl. 3, 1-18 (2015)
[4] A. Slavin et al., IEEE Trans. Magn. 45, 1875-1918 (2009)
[5] S. I. Kiselev et al., Nature 425, 380-383 (2003)
[6] Safranski, C., Montoya, E. A. & Krivorotov, Nat. Nanotechnol. 14, 27–30 (2019).


Thursday, February 28, 2019  

     Speaker: Yu-ming Mindy Huang, University of California, San Diego

     Title: The computational microscope of biomolecules: Molecular diffusion study through molecular dynamics and Brownian dynamics

     Abstract: Molecular diffusion, a main mechanism of transport of materials within cells, plays a fundamental role in a vast array of biological processes. Molecular dynamics (MD) and Brownian dynamics (BD) are computational simulation techniques used to model the diffusional encounter of two molecules in solution. In this talk, I will introduce the recent advances of these simulation tools. By applying MD, we were able to reveal the atomistic details of different molecular association pathways, which directly contribute to the ligand binding kinetics in the human immunodeficiency virus (HIV) protease. Moreover, BD enabled us to explore biological processes that are long timescale events. Through the simulation, we illustrated the driving forces of molecular encounter that play a role in the efficient operation of a small molecule (3'-5'-cyclic adenosine monophosphate) binding to a protein (phosphodiesterase). Finally, I will present a novel model that focuses on ligand-receptor surface reactions in a large-scale system.

 


Thursday, March 7, 2019  

     Speaker: Jonathan Trump, University of Connecticut

     Title: TBA

     Abstract: TBA


Thursday, March 28, 2019   Vaden Miles Lecture

     Speaker: Linda Spilker, Cassini Project Scientist, Jet Propulsion Laboratory

     Location:  Partrich Auditorium (Law School)

     Title: Surprises in the Saturn System: Cassini Mission Highlights

     Abstract: The Cassini mission's findings revolutionized our understanding of Saturn, its complex rings, the amazing assortment of moons and the planet's dynamic magnetic environment.  The robotic spacecraft arrived in 2004 after a 7-year flight from Earth, dropped a parachuted probe named Huygens to study the atmosphere and surface of Saturn's big moon Titan, and commenced making astonishing discoveries until the mission ended with a fiery plunge into Saturn's atmosphere on 15 September 2017. 

Key discoveries include icy jets shooting from the tiny moon Enceladus from a liquid water ocean beneath its icy crust, and lakes of liquid hydrocarbons and methane rain on Saturn's giant moon Titan.  These Cassini findings have fundamentally altered many of our concepts of where life might be found in our own solar system and beyond.  This presentation highlights the Cassini mission's most intriguing discoveries.

    Bio:  Dr. Linda Spilker is a planetary scientist at NASA's Jet Propulsion Laboratory who has participated in NASA and international planetary missions for over 40 years.  Spilker's mission roles include mission leadership as well as design, planning, operation and scientific data analysis. As Cassini Project Scientist Dr. Spilker leads a team of over 300 international scientists. She has worked in a science role on the Cassini project for 30 years and is a Co-I with the Cassini Composite Infrared Spectrometer team.  She previously worked on the Voyager mission for 12 years.  She also conducts independent research on the origin and evolution of planetary ring systems and supports proposals and concept studies for new missions to the outer planets.   She enjoys yoga and hiking in National Parks, including her favorite park, Yosemite.  She is married, with three daughters and seven grandchildren.

Spilker received her PhD summa cum laude from UCLA in 1992 in Geophysics and
Space Physics while also working at JPL. She has received a number of awards including a NASA Outstanding Public Leadership Medal and two NASA Exceptional Service Medals.



FALL 2018



Thursday, September 13, 2018

     Speaker: Lu Li, University of Michigan

     Title: Quantum Oscillations of Electrical Resistivity in an Insulator

     Abstract: In metals, orbital motions of conduction electrons are quantized in magnetic fields, which is manifested by quantum oscillations in electrical resistivity. This Landau quantization is generally absent in insulators, in which all the electrons are localized. Here we report a notable exception in an insulator — ytterbium dodecaboride (YbB12). The resistivity of YbB12, despite much larger than that of usual metals, exhibits profound quantum oscillations under intense magnetic fields. This unconventional oscillation is shown to arise from the insulating bulk, instead of conducting surface states. The large effective masses indicate strong correlation effects between electrons. Our result is the first discovery of quantum oscillations in the electrical resistivity of a strongly correlated insulator, and will bring crucial insight to the understanding of the ground state in gapped Kondo systems.


Thursday, September 20, 2018

     Speaker: Prashant Padmanabhan, Los Alamos National Lab

     Title: From plasmons to skyrmions: the ultrafast dynamics and control of novel excitations and materials

     Abstract: Over the last several decades, advances in ultrafast spectroscopy have enabled us to investigate fundamental phenomena associated with the electronic, lattice, and spin degrees of freedom in condensed matter systems at their intrinsic time-scales. Moreover, intense femtosecond pulses allow us to drive materials far from equilibrium. This provides us with access to states that are often difficult, or even impossible, to probe under normal thermodynamic conditions. As such, we can now examine the subtleties of exotic excitations, elucidate the microscopic coupling mechanisms between competing subsystems, and transiently manipulate the fundamental properties of novel materials. This talk will focus on such efforts in systems spanning prototypical semiconductors to quantum materials. Specific topics include massless collective excitations of multi-component plasmas, hole scattering dynamics in incipient ferroelectrics, and the optical control of low energy excitations in topologically protected spin textures.


Thursday, September 27, 2018

     Speaker: Nagesh Kulkarni, Quarkonics Inc.

     Title: From PhD to CEO: an Entrepreneurial Journey

     Abstract: A Physics education provides general skills in problem solving, teamwork, and knowledge in cutting--edge technologies.  Add some business skills and a physicist can become an entrepreneur.  I will talk about my entrepreneurial journey and share my experiences and thoughts on how scientists can play significant role in shaping the global economy, change the game, and create tremendous value for society by leveraging their unique analytical thinking and problem solving skills, networking, and specialized knowledge.


Thursday, October 4, 2018

     Speaker: Yaqiong Xu, Vanderbilt University

     Title: Carbon-Based Nanomaterials for Biosensing

     Abstract: Carbon-based nanomaterials, such as carbon nanotubes (CNTs) and graphene, have gained significant interest as one of the most promising materials in biological applications due to their unique physical and chemical properties. Recently we have developed an optoelectronic probing system, combining CNT/graphene transistors with scanning photocurrent measurements, fluorescence microscopy, and optical trapping techniques to investigate the molecular interface between CNTs/graphene and biological systems. We have directly measured the binding force between a single DNA molecule and a CNT in the near-equilibrium regime, where two aromatic rings spontaneously attract to each other due to the noncovalent forces between them. We have also integrated graphene-based scanning photocurrent microscopy with microfluidic platforms to investigate the electrical activities of individual synapses of primary hippocampal neurons. I will conclude by summarizing the remaining research challenges that must be surmounted in order to bring carbon-based nanomaterials into future biological applications.


Thursday, October 11, 2018

     Speaker: Sergio E. Ulloa, Ohio University

     Title: Putting Things on Top of Other Things (Proximity effects in 2D materials)

     Abstract:

Proximity effects such as those produced when depositing graphene on a transition metal dichalcogenide substrate are expected to change the dynamics of the electronic states in graphene, inducing spin orbit coupling and staggered potential effects.  Putting things on top of other things is promising and going strong in 2D materials!
In this talk, I will describe some of the expectations of combining different layered materials.  In particular, I will show how an effective Hamiltonian that describes different symmetry breaking terms in graphene, while preserving time reversal invariance, shows that a new topological insulator may be created by stacking "trivial" materials and applying strong electric fields.  These new systems may exhibit quantum spin Hall and valley Hall effects in different conditions [1].

 [1] A.M. Alsharari, M.M. Asmar and S.E. Ulloa, Phys. Rev. B 94, 241106(R) (2016); and Phys. Rev. B 97, 241104(R) (2018).


Thursday, October 18, 2018

     Speaker: Igor Žutić, University at Buffalo

     Title: Proximity Effects in van der Waals Materials

     Abstract: Advances in heterostructures and atomically thin van der Waals materials, such as graphene, suggest a novel approach to systematically design materials. A given material can be transformed through proximity effects whereby it acquires properties of its neighbors, for example, becoming superconducting, magnetic, topologically nontrivial, or with an enhanced spin–orbit coupling [1]. Such proximity effects not only complement the conventional methods of designing materials by doping or functionalization, but also can overcome their various limitations. In proximitized materials, it is possible to realize properties that are not present in any constituent region of the considered heterostructure. While the focus is on magnetic proximity effects with their applications in spintronics [2-4], the outlined principles also provide a broader framework for employing other proximity effects to tailor materials and realize unexplored phenomena.

1. I. Žutić et al., Mater. Today, (2018), arxiv:1805.07942, https://doi.org/10.1016/j.mattod.2018.05.003
2. P. Lazić et al., Phys. Rev. B 93, 241401(R) (2016)
3. B. Scharf et al., Phys. Rev. Lett. 119, 127403 (2017)
4. J. Xu et al., Nat. Commun. 9, 2869 (2018)


Thursday, October 25, 2018

     Speaker: TBA

     Title: TBA

     Abstract:

 


Thursday, November 1, 2018

     Speaker: Weihong Qiu, Oregon State University

     Title: Kinesin-14s: Moving into a New Paradigm

     Abstract: Kinesin-14s are microtubule-based motor proteins that play important roles in cell division. They were originally thought to be minus-end-directed nonprocessive motors that exhibit directional preference toward the microtubule minus ends in multi-motor ensembles but are unable to generate processive (continuous) motility on single microtubules as individual motors. During the past five years, we and others have discovered several "unconventional" kinesin-14 motors that all contain the ability to generate processive motility as individual motors on single microtubules. In this talk, I will present a series of unexpected yet exciting findings from my lab that have markedly expanded current view of the design and operation principles of kinesin-14 motors.


Tuessday, November 27, 2018  -- Note special day!

     Speaker: Ron Soltz, Lawrence Livermore National Lab

     Title: Evaluating the Iran Nuclear Deal

     Abstract: The Iran Nuclear Deal evokes strong reactions.  It has been called "The Worst Deal Ever" as well as "The best option for preventing Iran from obtaining a nuclear weapon.  Otherwise known as the "Joint Comprehensive Plan of Action", the JCPOA has led to much debate, even if little of it has been substantive.  Put into effect in 2015, the JCPOA continues to influence the behavior of 6 of the 7 signatories, the seventh having formally withdrawn 2018, reimposing sanctions in May and November.  In the history of international agreements, it is truly unique, but as it stands at the intersection of science and policy, it is also a valuable teaching tool for the role that science can play in formulating good policy, while also providing an opportunity to review a few basic concepts in nuclear physics.

 


Thursday, November 29, 2018

     Speaker: Gerald Gabrielese, Northwestern University

     Title: Stringent Tabletop Tests of the Standard Model:  A Tale of the Electron's Electric and Magnetic Dipole Moments

     Abstract: The standard model's most precise prediction -- of the size of the electron magnetic moment -- is tested using a single electron suspended by itself for months at a time in a tabletop-sized measurement.   Also, a new measurement of the electrons's other moment -- its electric dipole moment - was just completed in a very different tabletop measurement.  The standard model and proposed alternatives/additions differ sharply in their predictions of the size of this moment. 


Thursday, December 6, 2018

     NOTE LOCATION:  Lecture in Danto auditorium in Danto Engineering Building

     Speaker: Francis Halzen, Wisconsin IceCube Particle Astrophysics Center and Department of Physics, University of Wisconsin–Madison

     Title: IceCube: Opening a New Window on the Universe from the South Pole.

     Abstract:  The IceCube project has transformed a cubic kilometer of natural Antarctic ice into a neutrino detector. The instrument detects more than 100,000 neutrinos per year in the GeV to PeV energy range. Among those, we have isolated a flux of high-energy neutrinos of cosmic origin. We will explore the IceCube telescope and the significance of the discovery of cosmic neutrinos. We recently identified their first source: alerted by IceCube on September 22, 2017, several astronomical telescopes pinpointed a flaring galaxy powered by an active supermassive black hole, as the source of a cosmic neutrino with an energy of 290 TeV. Most importantly, the large cosmic neutrino flux observed implies that the Universe's energy density in high-energy neutrinos is close to that in gamma rays, suggesting that the sources are connected and that a multitude of astronomical objects await discovery.



2017-2018 Schedule


WINTER 2018


Thursday, January 18, 2018

     Speaker: Shanshan Cao, Wayne State University

     Title: Probing the Quantum Chromodynamic fluid with relativistic nuclear collisions

     Abstract: Nuclear matter is heated beyond two trillion degrees in relativistic heavy-ion collisions and becomes a strongly coupled plasma of quarks and gluons. This highly excited quark-gluon plasma (QGP) matter displays properties of perfect fluid and is believed similar to the state of the early universe microseconds after the big bang. In this talk, high-energy particles and jets are utilized to probe the QGP properties. A linear Boltzmann transport coupled to hydrodynamic model is established to describe the strong interaction between energetic partons and the QGP. This includes diverse microscopic processes for both massless and massive parton scatterings, and provides a simultaneous description of the nuclear modification of heavy and light flavor hadrons observed at the RHIC and LHC experiments. To precisely extract transport coefficients of the QGP, a statistical analysis framework that includes machine learning and Bayesian methods is developed, which brings a paradigm shift in statistical comparisons between theory and experiment.


Thursday, January 25, 2018

     Speaker: ChunNing (Jeanie) Lau, Ohio State University

     Title: Spin, Charge and Heat Transport in Low-Dimensional Materials

     Abstract: Low dimensional materials constitute an exciting and unusually tunable platform for investigation of both fundamental phenomena and electronic applications. Here I will present our results on transport measurements of high quality few-layer phosphorene devices, the unprecedented current carrying capacity of carbon nanotube "hot dogs", and our recent observation of robust long distance spin transport through the antiferromagnetic state in graphene.

     About the speaker: Dr. Chun Ning (Jeanie) Lau is a Professor in the Department of Physics at The Ohio State University. She received her BA in physics from University of Chicago in 1994, and PhD in physics from Harvard in 2001. She was a research associate at Hewlett Packard Labs in Palo Alto from 2002 to 2004, before joining University of California, Riverside in 2004 as an assistant professor. She was promoted to associate professor in 2009 and full professor in 2012. Starting January 2017 she moved to The Ohio State University. Her research focuses on electronic, thermal and mechanical properties of nanoscale systems, in particular, graphene and other two-dimensional systems.


Tuesday, January 30, 2018 (NOTE SPECIAL DATE)

     Speaker: Vladimir Skokov, Brookhaven National Lab

     Title: Quantum ChromoDynamics in extreme conditions

     Abstract: In my talk, I discuss two landscapes of Quantum ChromoDynamics (QCD), the theory of strong interactions, in extreme conditions. I start with hot and dense QCD, which can be probed in the collisions of heavy-ions at high energy. The goal of the heavy-ion program is to map and study the QCD phase diagram and establish the existence of a conjectured critical point in QCD. The identification of this prominent landmark in the phase diagram is possible owing to its unique signature. I argue that recent experimental measurements agree with the theoretical expectations and, if confirmed, may lead to the discovery of a QCD critical point. I then turn to the landscape of cold QCD to be probed at a future Electron-Ion Collider. I discuss one of the exciting features which is the linear polarization of strong quasi-classical gluon fields in an unpolarized nucleus. 


Thursday, February 1, 2018

     Speaker: Li Yan, McGill University

     Title: A droplet of QGP in the little bang

     Abstract: One of the fundamental questions in high energy nuclear physics is how to understand the dynamics of matter systems dominated by strong interactions. Especially, in systems where temperatures are comparable to the QCD energy scale (~10^12 K), such as the universe in the first microseconds after Big Bang, or in high energy heavy-ion collisions carried out at RHIC and the LHC (the Little Bang), our interest is in a novel state of matter -- quark-gluon plasma (QGP). One of the significant properties of QGP is its perfect fluidity. Actually, the value of shear viscosity over entropy density ratio of QGP has been found to be very close to a theoretical lower bound. The fluidity the QGP plays an essential role in the present studies of heavy-ion experiments. QGP evolution dominates the observed correlation behaviors of the produced particles in nucleus-nucleus collisions (large colliding systems), proton-lead and even proton-proton collisions (small colliding systems). In this talk, I will demonstrate how the idea of QGP fluidity emerges from the observed phenomena in experiments. I will also explain how a "standard model" of heavy-ion collisions based on relativistic hydrodynamics is challenged by the fluid behavior in recent small colliding systems.


Thursday, February 8, 2018

     Speaker: Chun Shen, Brookhaven National Lab

     Title: Going with the flow — the nuclear phase diagram at the highest temperatures and densities

     Abstract: The nuclear matter has a complex phase structure, with a deconfined Quark-Gluon Plasma (QGP) expected to be present under conditions of extreme pressure and temperature. The hot QGP filled the universe about few microseconds after the Big Bang. This hot nuclear matter can be generated in the laboratory via the collision of heavy atomic nuclei at high energy. I will review recent theoretical progress in studying the transport properties the QGP. Recently, the Relativistic Heavy-Ion Collider (RHIC) conducted the beam energy scan experiments. It offered a unique opportunity to study the nuclear phase diagram in a hot and baryon-rich environment. I will focus on the development of a comprehensive framework that is able to connect the fundamental theory of strong interactions with the RHIC experimental observables. This dynamical framework paves the way for quantitative characterization of the QGP and for locating the critical point in the nuclear phase diagram. These studies will advance our understanding of strongly interacting many-body systems and build interconnections with other areas of physics, including string theory, cosmology, and cold atomic gases.


Thursday, February 15, 2018

     Speaker: Mauricio Guerrero, North Carolina State University

     Title: Out of equilibrium dynamics: Lessons from Nuclear Collisions

     Abstract: The current knowledge of the universe is highly constrained without understanding the formation of baryonic matter widely observed today. It is then required to know the precise details of the transition where a highly dense plasma composed by quarks, antiquarks, and gluons combine to form hadrons. Ultrarelativistic heavy ion experiments can recreate non-equilibrium extreme conditions of the early universe by colliding heavy nuclei moving nearly at the speed of light. One of the major scientific discoveries of this century is the observation of a tiny, short-lived quark-gluon plasma (QGP). This extreme state of matter behaves like a liquid with a very small viscosity. Recently,  we have learned that the perfect fluidity property, observed first in nucleus-nucleus collisions, also extends to proton-nucleus and proton-proton collisions. The  "nearly perfect liquid" behavior of the QGP has opened up a new avenue for studying transport properties of strongly interacting systems. Nonetheless, these experimental findings challenge the theorists to develop better models which include the non-equilibrium evolution of the expanding nuclear matter created in those collisions. In this talk, I will review the 'standard model picture' of heavy ion collisions and present some recent theoretical studies which attempt to explain the unreasonable phenomenological success of fluid dynamical models in far from local equilibrium situations. I shall pose several unanswered questions about the QGP which emerge from these new theoretical developments and discuss how in the next few years, future experimental programs at large baryon densities and energy regimes will herald a new era of discovery and unraveling of the secrets of QGP.


Thursday, February 22, 2018

     Speaker: Hong Guo, McGill University

     Title: Electronic States of the Moiré superlattice

     Abstract: Two-dimensional (2D) van der Waals (vdW) heterostructures have attracted great attention in the past five years. By stacking different 2D materials to bond via the vdW force, these artificial heterostructures provide interesting and new material phase space for exploration. In this talk I shall focus on one aspect of the 2D vdW materials: the Moiré pattern. In visual arts, Moiré pattern is an optical perception of a new pattern formed on top of two similar stacking patterns. In 2D vdW heterostructures, the Moiré pattern is a physical superlattice which brings about novel electronic properties. To theoretically predict the physical properties of the Moiré superlattice, systems containing more than ten thousand atoms often need to be analyzed by first principles. In this talk I shall begin by briefly discussing how one may break the "size limit" so that very large first principles simulations within the density functional theory can be carried out. Afterward, I shall present and discuss some of the calculated novel properties of the Moiré superlattice: the emergence of a secondary Dirac cone, the suppression of the carrier mobility, and the formation of multiple helical valley currents, on various 2D vdW heterostructure materials. Some of these properties can well be the basis of potential applications.

     About the speaker: Dr. Hong Guo obtained B.Sc. in Physics at the Sichuan Normal University in China and Ph.D. in theoretical condensed matter physics at the University of Pittsburgh. In 1989, he joined the faculty of the Physics Department, McGill University in Montreal Canada. He is currently a James McGill Professor of Physics. His research includes quantum transport theory, nanoelectronic device physics, nonequilibrium phenomena, materials physics, density functional theory, mathematical and computational physics. He was elected to Fellow of the American Physical Society in 2004, and Fellow of the Royal Society of Canada (Academy of Sciences) in 2007. He received the Killam Research Fellowship Award from the Canadian Council for the Arts in 2004; the Brockhouse Medal for Excellence in Experimental or Theoretical Condensed Matter Physics of the Canadian Association of Physicists in 2006; and the CAP-CRM Prize in Theoretical and Mathematical Physics from Canadian Association of Physicists in 2009.


Friday, March 2, 2018 (Note Special Colloquium Date)

     Speaker: David Ceperley, University of Illinois at Urbana-Champaign, and member of the National Academy of Sciences

     Title: How can we model the hydrogen inside Jupiter and Saturn?

     Abstract: Jupiter, Saturn and a host of newly discovered exoplanets are thought to be composed largely of hydrogen and helium. To understand the planets, we need properties of hydrogen and helium under the extreme conditions of temperature and pressure inside those planets, conditions hardly accessible to laboratory measurements. I will describe how we use high performance computers to calculate those properties and thus help understand some of the most important objects in the Universe.

     About the speaker: Dr. David Ceperley is the Founder and Blue Waters Professor of Physics at University of Illinois Urbana-Champaign, and a member of the National Academy of Sciences. He received his BS in physics from the University of Michigan in 1971 and his Ph.D. in physics from Cornell University in 1976. After one year at the University of Paris and a second postdoc at Rutgers University, he worked as a staff scientist at both Lawrence Berkeley and Lawrence Livermore National Laboratories. In 1987, he joined the Department of Physics at Illinois. He was a staff scientist at the National Center for Supercomputing Applications from 1987 until 2012. Professor Ceperley is a Fellow of the American Physical Society and a member of the American Academy of Arts and Sciences, and was elected to the National Academy of Sciences in 2006. He has received many honors and awards; see https://physics.illinois.edu/people/directory/profile/ceperley


Tuesday, March 6, 2018 (NOTE SPECIAL DATE AND TIME: 2:30pm)

     Speaker: LongGang Pang, Lawrence Berkeley National Laboratory

     Title: Exploring the quantum chromodynamics phase transition with deep learning 

     Abstract: The state-of-the-art pattern recognition method in machine learning (deep convolution neural network) has been used to classify two different phase transitions between normal nuclear matter and hot-dense quark gluon plasma. Big amount of training data is prepared by simulating heavy ion collisions with the most efficient relativistic hydrodynamic program CLVisc. High level correlations of particle spectra in transverse momentum and azimuthal angle learned by the neural network are quite robust in deciphering the transition type in the quantum chromodynamics phase diagram. Through this study we demonstrated that there is a traceable encoder of the phase structure that survives the dynamical evolution and exists in the final snap shot of heavy ion collisions and one can exclusively and effectively decode these information from the highly complex output using machine learning.


Thursday, March 8, 2018

     Speaker: Christoph Naumann, Indiana University - Purdue University Indianapolis

     Title: Probing membrane protein organization and dynamics in planar model membranes using single molecule-sensitive confocal detection techniques 

     Abstract: The organization and distribution of proteins in the plasma membrane is widely known to influence membrane protein functionality. However, it remains challenging to decipher the underlying mechanisms that regulate membrane protein properties in the complex environment of cellular membranes. To overcome these challenges, an experimental strategy is discussed, in which the distribution, oligomerization state, and mobility of membrane proteins can be explored in a planar polymer-tethered lipid bilayer of well-defined lipid compositions using single molecule-sensitive confocal detection strategies. Results from such model membrane experiments are presented, which explore the influence of native ligands, bilayer asymmetry, and cholesterol content on the sequestration/oligomerization of urokinase plasminogen activator receptors (uPAR) and integrins [1-4]. Moreover, dual-color confocal experiments are described, which provide information about the formation and composition of uPAR-integrin complexes and the role of membrane cholesterol therein. Polymer-tethered lipid bilayer systems, comprised of phospholipids and lipopolymers, are also characterized by remarkable materials properties, which make them suitable as cell surface-mimicking substrates for the analysis of adhesion and spreading of plated cells. To illustrate the feasibility of such an application, we discuss the assembly of cadherin chimera into clusters on the surface of a polymer-tethered lipid bilayer substrate to form stable cell-substrate cadherin linkages underneath migrating C2C12 myoblasts [5]. Cluster tracking experiments reveal the cytoskeleton-regulated long-range mobility of cell-substrate linkages, thereby displaying remarkable parallels to the dynamics of cadherin-based cell-cell junctions.

[1] A. P. Siegel et al. (2011) Biophys. J. 101, 1642.
[2] N. F. Hussain et al. (2013) Biophys. J. 104, 2212.
[3] Y. Ge et al. (2014) Biophys. J. 107, 2101.
[4] Y. Ge et al. (2018) Biophys. J. 114, 158.
[5] Y. Ge et al. (2016) Soft Matter 12, 8259.


Thursday, March 15, 2018

     No Colloquium - Spring break


Thursday, March 22, 2018

     Speaker: W.J. Llope, Wayne State University

     Title: How to give a great talk - tips for success and traps to avoid

     Abstract: Whether your future lies in academia or industry, you will have opportunities to present your recent work while standing in front of an audience of interested people. Giving a good talk is a very powerful advertisement of you and your efforts, and, if you can properly enthuse the audience during your talk, the subsequent discussions can be very helpful for your future work. Great talks come in many forms, but all share a few key positive aspects and all avoid some (unfortunately rather common) pitfalls. This colloquium will share some tips from what I've learned over the years while watching thousands of talks, and giving a few myself. This presentation is specifically aimed at our students and postdocs, although the faculty are of course welcome to share their insights as well. The atmosphere will be informal and an open discussion, especially with our younger colleagues, will be encouraged.


Thursday, March 29, 2018

     Speaker: Vladimir Chernyak, Department of Chemistry, Wayne State University

     Title: Integrability in Non-Equilibrium Quantum Dynamics

     Abstract: Nonequilibrium quantum dynamics, i.e., quantum evolution with time-dependent Hamiltonians, iħ ∂Ψ(t)/∂t = Ĥ(t)Ψ(t), as of today draws considerable attention, both in experimental and theoretical research. The simplest model with Ĥ(t)=A+Bt, and A and B being 2×2 real hermitian matrices, known as the Landau-Zener (LZ) problem has an exact solution in special functions, with the scattering matrix S, expressed in term of Gaussians and Euler Gamma-function. In the general N-dimensional case, known as Multilevel LZ (MLZ) problem, exact solutions are not available. However, for a certain class of MLZ problems that satisfy certain phenomenologically determined "integrability" conditions, including, but not limited to Demkov-Osherov (DO), Generalized Bow-Tie (GBT), and Tavis-Cummings (TC), the scattering matrix can be represented in a factorized form, with the elementary scattering events being represented in terms of the standard LZ matrix, which is the first aspect of integrability; in other words the semiclassical expressions become exact.
     In this talk we reveal the reason that stands behind the aforementioned factorization: Each integrable MLZ problem can be embedded into a system of M linear first-order differential equations with respect to M-dimensional time, that satisfy the consistency conditions, the latter having a form of the zero-curvature conditions, which is the second and dynamical aspect of integrability.
     We further apply our approach to obtain an exact solution for the BCS model that does not belong to the MLZ class, but rather describes decay of the initial strongly correlated state of Ns quantum spins (in the thermodynamic Ns→∞ limit the model becomes a non-trivial field theory) into an uncorrelated counterpart when the spin-spin interaction is switched of, and generally in a non-adiabatic fashion. The obtained exact solution shows an amazing property: The ground state in the strongly correlated phase "dissociates" into a Gibbs distribution in a completely integrable way, without any chaos or bath involved. We demonstrate that the aforementioned result is a third aspect of integrability, which is natural appearance of the structures, usually associated with quantum integrability in a form of algebraic Bethe Ansatz, including the Yang-Baxter-Zamolodchikov (YBZ) equation, Artin's Braid Group, and quantum group SUq(2).
     The presentation will be given in an intuitive fashion, all mathematical structures involved will be explained using the terms, which are common for a broad physics audience.


Thursday, April 5, 2018

     Speaker: Prof. Aaron Pierce, Director of the Leinweber Center for Theoretical Physics at the University of Michigan

     Title: Dark Matter: WIMPS and Beyond

     Abstract: The identity of the Dark Matter that dominates the matter density of the universe remains a mystery.  Increasingly sophisticated experiments have begun to probe some of the best motivated models of dark matter.  I will review the theoretical status of one such paradigm, so-called Weakly Interacting Massive Particle (WIMP) Dark Matter, with particular emphasis on the implications of direct detection experiments.  We will see that while the paradigm is alive and well, it is under non-trivial pressure, particularly in specific implementations, such as supersymmetry. This warrants searches for other types of Dark Matter.  I will very briefly discuss a few such searches, including a new possibility of using the LIGO gravitational wave detector as a dark matter detector.


Thursday, April 12, 2018

     No Colloquium -- Graduate Research Day


Thursday, April 19, 2018 (Vaden Miles Lecture)

     Speaker: J. Michael Kosterlitz, Brown University (2016 Nobel Prize in Physics)

     Location: Spencer M. Partrich Auditorium, Wayne State University Law School

     Title: Topological Defects and Phase Transitions - A Random Walk to the Nobel Prize

     Abstract: This talk is about my path to the Nobel Prize and reviews some of the applications of topology and topological defects in phase transitions in two-dimensional systems for which Kosterlitz and Thouless split half the 2016 Physics Nobel Prize. The theoretical predictions and experimental verification in two dimensional superfluids, superconductors and crystals will be reviewed because they provide very convincing quantitative agreement with topological defect theories.

     About the speaker: Dr. J. Michael Kosterlitz is a theoretical physicist recognized for his work with David J. Thouless on the application of topological ideas to the theory of phase transitions in two-dimensional systems with a continuous symmetry. The theory has been applied to thin films of superfluid 4He, superconductors and to melting of two-dimensional solids. This work was recognized by the Lars Onsager prize in 2000, membership in the AAAS 2007, and by the 2016 Nobel Prize in Physics. Dr. Kosterlitz graduated from Cambridge University earning a BSc in physics in 1965, an MA in 1966, and received a D. Phil. from Oxford in 1969. He was a postdoctoral fellow at Torino University, Italy, in 1970 and at Birmingham University, U.K., from 1970-73. There he met David Thouless and together they did their groundbreaking work on phase transitions mediated by topological defects in two dimensions. He was a postdoctoral fellow at Cornell in 1974, on the faculty at Birmingham 1974-81, Professor of Physics at Brown University 1982 – present, and elected to the National Academy of Sciences in 2017.

 


 

FALL 2017


Thursday, September 7, 2017

     Speaker: Victor Yakovenko, University of Maryland

      Title: Economic inequality from a statistical physics point of view

      Abstract: By analogy with the probability distribution of energy in statistical physics, the probability distribution of money among the agents in a closed economic system is expected to follow the exponential Boltzmann-Gibbs law, as a consequence of entropy maximization.  Analysis of empirical data shows that income distributions in the USA, European Union, and other countries exhibit a well-defined two-class structure.  The majority of the population (about 97%) belongs to the lower class characterized by the exponential ("thermal") distribution.  The upper class (about 3% of the population) is characterized by the Pareto power-law ("superthermal") distribution, and its share of the total income expands and contracts dramatically during booms and busts in financial markets.  Such a two-class distribution can be obtained analytically for a combination of additive and multiplicative stochastic processes.  Globally, data analysis of energy consumption (and CO2 emission) per capita around the world in the last 30 years shows decreasing inequality and convergence toward the exponential probability distribution, in agreement with the maximal entropy principle.  All papers are available at http://physics.umd.edu/~yakovenk/econophysics/.


Thursday, September 14, 2017 (Note special location)

     Speaker: Kip Thorne

     Location:  Spencer M. Partrich Auditorium, Wayne State University Law School

      Title: Geometrodynamics: Exploring the nonlinear dynamics of curved spacetime via computer simulations and gravitational wave observations

      Abstract:  A half century ago, John Wheeler challenged his students and colleagues to explore Geometrodynamics:  the nonlinear dynamics of curved spacetime. How does the curvature of spacetime behave when roiled in a storm, like a storm at sea with crashing waves. Dr. Thorne and collaborators tried to explore this, and the failed. Success eluded us until two new tools became available: computer simulations, and gravitational wave observations. Dr. Thorne will describe what these have begun to teach us, and he will offer a vision for the future of Geometrodynamics.

About the speaker: Kip Thorne is the Richard P. Feynman Professor of Theoretical Physics, Emeritus, at the California Institute of Technology in Pasadena, California. He is a theoretical physicist specializing in the astrophysical effects of Einstein's General Theory of Relativity, especially black holes and gravitational waves. He was one of the founding members of the Laser Interferometer Gravitational Wave Observatory (LIGO) in 1984. The goal of LIGO is to observe gravitational waves from extreme astrophysical events. Gravitational waves were first predicted by Albert Einstein one-hundred years ago this year. While there is good indirect evidence for gravitational waves based on the behavior of binary pulsars, the first direct measurement of a gravitational wave was announced by the LIGO team on February 11, 2016. Two independent laser interferometers in Livingston, Louisiana and Hanford, Washington observed a gravitational wave on September 14, 2015. Analysis of the signal indicates the wave was produced by the collision of two black holes more than one-billion light years away. Professor Thorne is an accomplished author of books for scientists and the general public, and he was the scientific consultant and Executive Producer of the film Interstellar.

A video of this colloquium may be found HERE (YouTube)


Thursday, September 21, 2017

     Speaker: Boris Yakobson, Rice University

      Title: Predictive modeling of low-dimensional materials, nanotubes, graphene, and beyond

      Abstract: Comprehensive tools of materials modeling are derived from the principles of physics and chemistry, empowered by high performance computing. Together, this allows one to make verifiable predictions of novel physical structures with specific, often useful or even extraordinary, properties. Nanotubes offer one such lesson [1], where atomic makeup and defects dynamics lead to the understanding of their strength and failure physics on one hand, while also reveal the origins of chiral symmetry in nano-carbon synthesis [2]. A second, very recent, example is the prediction of pure mono-elemental 2D boron, its particular structures to form on Ag(111), which culminated in recent experimental confirmations. We may also mention, if time permits, its physical properties like new 2D-superconductor [3], now-detected Dirac cone dispersion, still-sought 2D-plasmonics, and catalysis.

[1] M. Davenport, Chemical & Engineering News, 93, 10 (2015) || B.I. Yakobson and R.E. Smalley, American Scientist, 85, 324-337 (1997).

[2] F. Ding et al. Proc. Natl. Acad. Sci., 106, 2506 (2009) || V. Artyukhov et al. Proc. Natl. Acad. Sci. 109, 15136 (2012) || V. Artyukhov et al. Phys. Rev. Lett. 114, 115502 (2015) || V. Artyukhov - E. Penev, et al. Nature Comm. 5, 489 (2014).

[3] Z. Zhang et al. Nature Chem. 8, 525 (2016) || Z. Zhang et al. Angewandte Chemie Int. Ed. 54, 13022 (2015) || E. Penev - A. Kutana et al. Nano Lett. 16, 2522 (2016) || Z. Zhang et al. Nano Lett. 6, 6622 (2016) || A. Brotchie, Nature Reviews, doi:10.1038/natrevmats.2016.83 (2016) || S. Shirodkar, Y. Huang et al. (unpublished) || Y. Liu et al. Nature Energy 2, 17127 (2017).


Thursday, September 28, 2017

     Speaker: Michael Murray, University of Kansas

      Title: There and Back Again: A Journey from classical physics to quantum mechanics and back to classical fields.

      Abstract: When the nucleus was discovered it appeared to be a massive classical charged sphere at the heart of atom. Later protons and neutrons were discovered inside the nucleus. Later still it was found that  protons and neutrons are themselves made up of quarks held together by gluons. Such objects are described by quantum field theories. As the energy of our colliders has increased we have found more and more gluons inside the nucleus. At some point we expect the gluons to fuse together into a glass like state called the Color Glass Condensate. This new state of quantum matter may actually behave like a classical field.


Thursday, October 5, 2017

     Speaker: Chris Adami, Michigan State University

      Title: What quantum optics can tell us about black holes

      Abstract: Black holes are astrophysical objects whose reality is beyond doubt. However, many aspects of them remain mysterious because observations are difficult and experiments are impossible. Research in the last two decades has revealed a remarkable analogy between the mathematics of quantum black holes and certain quantum optical systems, which makes it possible to study "black hole analogues" in the lab, and to better understand some of the seemingly paradoxical features of black holes. I review recent breakthroughs in black hole physics that were inspired by the quantum optics analogy, and that have removed some of the paradoxes surrounding black holes. 

      About the speaker: Dr. Adami is Professor for Microbiology and Molecular Genetics & Physics and Astronomy at Michigan State University in East Lansing, Michigan. As a computational biologist, Dr. Adami's main focus is Darwinian evolution, which he studies theoretically, experimentally, and computationally, at different levels of organization (from simple molecules to brains). He has pioneered the application of methods from information theory to the study of evolution, and designed the "Avida"" system that launched the use of digital life (mutating and adapting computer viruses living in a controlled computer environment) as a tool for investigating basic questions in evolutionary biology. He was also a Principal Scientist at the Jet Propulsion Laboratory where he conducted research into the foundations of quantum mechanics and quantum information theory. Dr. Adami earned a BS in physics and mathematics and a Diplom in theoretical physics from the University of Bonn (Germany) and MA and PhD degrees in theoretical nuclear physics from the State University of New York at Stony Brook. He wrote the textbook "Introduction to Artificial Life" (Springer, 1998) and is the recipient of NASA's Exceptional Achievement Medal. He was elected a Fellow of the American Association for the Advancement of Science (AAAS) in 2011.


Thursday, October 12, 2017

     Speaker: Pushpa Bhat (FNAL)

      Title: Fifty Years of Particle Physics and Discoveries at Fermilab

      Abstract: Fermilab, the premier laboratory for elementary particle physics and accelerator research in the U.S., has been at the forefront of fundamental discoveries for the past fifty years.  It has had the distinction of discovering three fundamental particles – the bottom and top quarks, and the tau neutrino, as well as leading the detailed exploration of the Standard Model, and making major advances in the pursuit of the Higgs boson.  The home of the highest energy proton accelerator and particle collider in the world until the end of the last decade, Fermilab has also led the development of enabling technologies for powerful accelerator facilities.  In this talk, I will present the highlights of the past fifty years of particle physics at Fermilab and discuss its future program and role in the new global enterprise of particle physics.

     About the speaker: Pushpa Bhat is a senior scientist at Fermi National Accelerator Laboratory (Fermilab), Deputy Head of Fermilab Program Planning, and an Adjunct Professor and graduate faculty at Northern Illinois University. After receiving her Ph.D. in physics from Bangalore University, India, in 1982 and a brief stint as a scientific officer at the Eindhoven University Cyclotron Lab in the Netherlands, she moved to the U.S. and carried out postdoctoral work in experimental high energy physics at Duke University and Fermilab.  Her research career has spanned applied physics, nuclear physics and experimental particle physics, from keV energies to the energy frontier. Bhat is a Fellow of the American Physical Society (APS) and the American Association for the Advancement of Science (AAAS).  She has served as the Chair of the APS Forum on Physics and Society (FPS) and as Chair of several committees.  She currently serves on the APS Council and on the APS Board of Directors, and as Secretary for the International Committee on Future Accelerators (ICFA).


Thursday, October 19, 2017

     Speaker: Zhi-Feng Huang, Wayne State University

      Title: Exploring microstructures and dynamics of complex systems: Ordering, chirality, defects, and scale coupling

      Abstract: One of the long-lasting challenges in the study of advanced materials is how to effectively tackle vast complexity of the system that is of nonequilibrium nature and involves multiple spatial and temporal scales. Of particular importance is the bridging between material microstructural details and mesoscopic characteristics such as surface patterns or interfacial structures, for which much of recent theoretical effort has been put on the development of novel density-field based approaches across different scales. In this talk I will discuss some recent advances in this field for modeling material microstructures and dynamics and some of the ongoing challenges. Sample topics include the emergence of ordering phases, the control of 2D structure or pattern chirality and chiral elastic properties, structures and collective dynamics of topological defects in binary 2D materials such as h-BN, and the interface lattice pinning effect during material growth due to the coupling between micro and meso spatial scales.


Thursday, October 26, 2017

     Speaker: Christopher Kelly, Wayne State University

      Title: Nanoscale membrane curvature revealed by polarized localization microscopy

      Abstract: Many essential biological processes depend on the interaction of lipids, proteins, and carbohydrates at length scales that are unresolvable by conventional optical microscopes. We have combined super-resolution microscopy methods to create polarized localization microscopy (PLM). With PLM, we have measured membrane curvature as small as 20 nm radii, measured curvature-induced molecular sorting, and a local change in the local membrane viscosity. Further, we have discovered that cholera toxin subunit B self-assembles to form nanoscale membrane buds in quasi-one component bilayers to facilitate its immobilization and internalization into cells. We will discuss the physics of PLM and the mechanisms by which cholera toxin bends membranes.


Thursday, November 2, 2017

     No Colloquium (Fall Get-Together)


Thursday, November 9, 2017

     Speaker: Ken Ritchie, Purdue University

      Title: High-speed single molecule tracking of proteins in E. coli

      Abstract: All living cells are encapsulated by an outer envelope, which contains a fluid phospholipid-based membrane that structurally delineates the inside of the cell from its environment. Embedded within this membrane is the machinery (proteins) required for the cell to sense and interact with its environment. As such, one expects that there are mechanisms in place to control the location and mobility of the membrane proteins in the fluid membrane in order to perform complex and critical tasks. In this talk, I will present our group's recent single molecule mobility studies into the (dynamic) organization of the cellular membranes of E. coli bacteria performed at acquisition rates up to 1 kHz. Examples will include the structure of the polar region of the inner membrane as seen by the serine chemoreceptor Tsr and investigations into interactions of the iron transporter FepA in the E. coli outer membrane with the inner membrane protein TonB.

      About the speaker: Dr. Ritchie is a professor and the Associate Head of Department of Physics and Astronomy at Purdue University. He obtained his PhD at University of British Columbia in Vancouver in 1998, and was the Group Leader in the Kusumi Membrane Organizer Project in Nagoya, Japan in 1998-2005 and an assistant professor at Nagoya University in 2000-2005. He joined Purdue University in 2005 as a professor of physics and is the associate head of the department since 2015.


Thursday, November 16, 2017

     No Colloquium -- UG Research Day


Thursday, November 23, 2017

     No Colloquium -- Thanksgiving


Thursday, November 30, 2017

     Speaker: Jenny Thomas, University College London

      Title: An alternative future for neutrino physics

      Abstract: Neutrino Oscillations have provided a new insight into the properties of neutrinos since their discovery almost 20 years ago. There are a number of experiments presently providing new results pointing to a future direction in the field. One fundamental and overarching difficulty associated with any kind of measurements of neutrinos is that they only interact with the weak interaction, making their observation rather rare. This leads to very long wait times for results and the need for larger and larger detectors which eventually break the bank. It is time for a paradigm shift in the way neutrino physics is carried out, without the need for 1000 people for each experiment, sums of money that take your breath away and detectors that are so small they need 20 years to make the next fundamental step. I will give an introduction to the physics, the recent results in the field and then talk about an alternative future where we can make measurements quickly with huge detectors at a fraction of the cost of presently planned experiments.


Thursday, December 7, 2017

     Speaker: Oleg D. Lavrentovich, Kent State University

      Title: Using liquid crystals to command swimming bacteria

      Abstract: Self-propelled bacteria are marvels of nature. If we can control their dynamics, we could use it to power dynamic materials and microsystems of the future. Unfortunately, bacterial swimming is mostly random in isotropic liquids such as water and is difficult to control by factors other than transient gradients of nutrients. We propose to command the dynamics of bacteria by replacing water with water-based liquid crystals. The long-range orientational order of the liquid crystal can pre-patterned into various structures by a plasmonic photoalignment technique [1]. The experiments demonstrate that the liquid crystals command the dynamics of bacteria, namely, the trajectories of swimming, polarity of motion, and distribution of bacteria in space [2]. The study of bacteria-liquid crystal system might result in approaches to harness the energy of collective motion for micro-robotic, biomechanical, and sensing devices, as well as micro-mixing and transport of micro-cargo. The work is supported by NSF grants DMR-1507637 and DMS-1729509.

[1] C. Peng, Y. Guo, T. Turiv, M. Jiang, Q.-H. Wei, O.D. Lavrentovich, Patterning of Lyotropic Chromonic Liquid Crystals by Photoalignment with Photonic Metamasks, Advanced Materials 2017, 1606112 (2017).

[2] C. Peng, T. Turiv, Y. Guo, Q.-H. Wei, O.D. Lavrentovich, Command of active matter by topological defects and patterns, Science 354, 882 (2016).

      About the speaker: Oleg D. Lavrentovich received his Ph.D. (1984) and Doctor of Science (1990) degrees in Physics and Mathematics from the Ukrainian Academy of Sciences for his research on topological defects in liquid crystals. In 1992 he joined the Liquid Crystal Institute at Kent State University. He served as the director of Institute in 2003-2011. He is currently a Trustees research professor affiliated with the Department of Physics, Chemical Physics Interdisciplinary program and the Liquid Crystal Institute at Kent State. His current research focuses on electro-optics of liquid crystals, topological defects, hybrid colloid-liquid crystal systems, liquid crystals as active matter and liquid crystals as nonlinear electrolytes. He is the editor of Liquid Crystals Reviews (Taylor & Francis), associate editor of Soft Matter (Royal Society of Chemistry), Fellow of APS and SPIE.


WSU colloquia from years past may be found here.