9/14/15 Matthieu Wyart NYU

The memory of sand
Complex systems are characterized by an abundance of meta-stable states. To describe such systems statistically, one must understand how states are sampled, a difficult task in general when thermal equilibrium does not apply.  This problem arises in various fields of science,  and here I will focus on a simple example, sand. Sand can flow until  one jammed configuration (among the exponentially many possible ones) is reached. I will argue that at least in popular simplified models of granular materials, these dynamically-accessible configurations are atypical, implying that in its solid phase the material "remembers"  that it was flowing just before it jammed. As a consequence, it is stable, but barely so. I will argue that this marginal stability offers a new perspective on long-standing questions both  on the solid and liquid phase of granular materials, in particular on dense suspension flows near jamming.

9/21/15 Scott Hughes MIT
Tides, resonances, and precession: Understanding and visualizing the dynamics of black holes in binary systems.
The past decade has seen spectacular advances in our ability to model binary systems in general relativity.  Both numerical and analytic techniques have now produced tools that make it possible to track many thousands of orbits of compact bodies — neutron stars and black holes — as they orbit one another and spiral inward due to the backreaction of gravitational waves on the binary.  Much of the research in this field now focuses on studying these systems and seeing what can be learned from studies and observations of general relativistic binaries.  In this talk, I will describe examples of the phenomena that we find characterize systems containing black holes: Tidal distortions of black hole event horizons, resonances between orbital frequencies, and precessions of the spins of binary members.  Each of these phenomena is likely to play an important role in future gravitational wave measurements.  I will show that these effects can be understood in very simple terms, albeit usually with some kind of special “twist” owing to the special nature of very strong gravity in general relativity.
9/28/15 Eric Mazur Harvard University
Less is More: Extreme Optics with Zero Refractive Index
Nanotechnology has enabled the development of nanostructured composite materials (metamaterials) with exotic optical properties not found in nature. In the most extreme case, we can create materials which support light waves that propagate with infinite phase velocity, corresponding to a refractive index of zero. This zero index can only be achieved by simultaneously controlling the electric and magnetic resonances of the nanostructure. We present an in-plane metamaterial design consisting of silicon pillar arrays, embedded within a polymer matrix and sandwiched between gold layers. Using an integrated nano-scale prism constructed of the proposed material, we demonstrate unambiguously a refractive index of zero in the optical regime. This design serves as a novel on-chip platform to explore the exotic physics of zero-index metamaterials, with applications to super-coupling, integrated quantum optics, and phase matching.
10/5/2015 David Weitz Harvard University
Universal correlation between stiffness and volume for living cells
The stiffness of cells is commonly assumed to depend on the stiffness of their surrounding: bone cells are much stiffer than neurons, and each exists in surrounding tissue that matches the cell stiffness.  In this talk, I will discuss new measurements of cell stiffness, and show that that cell stiffness is strongly correlated to cell volume.  This affects both the mechanics and the gene expression in the cell, and even impacts the differentiation of stem cells.  To probe the effects of gene expression, I will discuss lab-on-a-chip developments that provide a full gene expression analysis at the level of individual cells.  Finally, I will also discuss new measurement techniques that probe the consequences of the cell stiffness on internal cell dynamics.
10/19/2015 Robert Caldwell Dartmouth College
A new twist on cosmic fields
An unresolved problem of cosmology is to determine the physical origin of the accelerated expansion of the universe. One explanation is a cosmological constant, but this is widely regarded as a placeholder until a deeper understanding can be attained. A leading alternative theory invokes a cosmic scalar field, slowly rolling down its potential energy hill. This is more in tune with known physics, like the recently discovered Higgs; perhaps the universe is in the process of undergoing a phase transition. A similar process may also explain an inflationary period in the early universe. But now comes a new possibility, that the accelerated expansion is caused by a relic from the early universe in the form of a frozen triplet of fields, a flavor-space locked gauge field. In this case, the dynamics of the gauge field is more like a spinning top than a ball rolling down a hill.  We will explore the consequences of a cosmological scenario with these fields and show that it leads to some unusual but testable predictions for the cosmic microwave background, primordial gravitational waves, and the expansion of the universe.
10/26/15 Liang Fu MIT
Symmetry-Protected Topological Matter
It has long been known that properties of solids depend crucially on symmetry. For example, diamond and graphite, both made of carbon atoms, have vastly different properties due to the difference in crystal symmetry; a ferromagnet differs from a paramagnet in the spontaneous breaking of spin rotational symmetry. In the last decade, it has come to be recognized that quantum materials having the same symmetry can still be in distinct phases due to the difference in the topology of quantum wavefunctions. In this talk, I will describe the general concept of symmetry-protected topological matter and its prime examples including topological insulators, topological crystalline insulators and topological superconductors. Their material realizations, unique electronic properties (which can be tuned by symmetry breaking) and potential device applications will be discussed. 
11/2/2015 Leonid Glazman Yale University
Nonlinear Quantum Liquids in One Dimension
The conventional description of one-dimensional quantum fluids is based on the Luttinger liquid theory. In that theory, the true energy-momentum relation of particles making up the fluid is replaced by a linear one. This simplification is crucial for the theory, and abandoning it has proven to be difficult. The talk presents a breakthrough which allows one to circumvent the difficulty. The new theory describes dynamic responses  of a fluid consisting of particles with a generic spectrum. It also provides a pathway for developing kinetic theory of a quantum fluid. The developed new description is applicable to a diverse group of systems, including, for example, electrons in quantum wires, one-dimensional spin liquids, and cold atomic gases in one-dimensional traps.
11/9/2015 Jordan Goodman University of Maryland
First Results from the HAWC Gamma Ray Observatory
The High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory in the high mountains of Mexico was completed in March of 2015 and is now giving us a new view of the TeV sky. HAWC is 15 times more sensitive than the previous generation of EAS gamma-ray instruments (Milagro and ARGO) and is able to detect the Crab nebula at >5.5σ with each daily transit. In a year of operation, HAWC will have a 5σ detection sensitivity for a source of ~50mCrab. Unlike Imaging Atmospheric Cherenkov Telescopes (IACTs), HAWC operates 24hrs/day with over a 95% on-time and observes the entire overhead sky (~2sr).  HAWC’s peak energy sensitivity is 2-10 TeV which is ~10x higher than IACTs such as VERITAS and HESS, which makes their observations quite complementary. This talk will describe the science of gamma-ray astronomy; describe the HAWC detector and its construction as well as showing preliminary results from the first 6 months of operation.
11/16/2015 Vidya Madhaven University of Illinois at Urbana-Champaign
Massless and Massive Electrons: Relativistic Physics in Condensed Matter Systems
Electrons in free space have a well-defined mass. Recently, a new class of materials called topological insulators were discovered, where the low energy electrons have zero mass. In fact, these electrons can be described by the same massless Dirac equation that is used to describe relativistic particles travelling close to the speed of light. In this talk I will describe our recent experimental and theoretical investigations of a class of materials called Topological Crystalline Insulators (TCIs) [1]. TCIs are recently discovered materials [2,3] where topology and crystal symmetry intertwine to create linearly dispersing Fermions similar to graphene. To study this material we used a scanning tunneling microscope [3,4,5]. With the help of our data, I will show how zero-mass electrons and massive electrons can coexist in the same material. I will discuss the conditions to obtain these zero mass electrons as well the method to impart a controllable mass to the particles and show how our studies create a path to engineering the Dirac band gap and realizing topological quantum phenomena in TCIs.
[1] L. Fu, Topological Crystalline Insulators. Phys. Rev. Lett. 106, 106802 (2011).
[2] T. H. Hsieh et al., Topological crystalline insulators in the SnTe material class. Nat.Commun. 3, 982 (2012).
[3] Y. Okada, et al., Observation of Dirac node formation and mass acquisition in a topological crystalline insulator, Science 341, 1496-1499 (2013)
[4] Ilija Zeljkovic, et al., Mapping the unconventional orbital texture in topological crystalline insulators, Nature Physics 10, 572–577 (2014)
[5] Ilija Zeljkovic, et al., Dirac mass generation from crystal symmetry breaking on the surfaces of topological crystalline insulators, Nature Materials 14, 318–324 (2015) 
11/23/2015 Carlton Caves University of New Mexico
Quantum-limited measurements: One physicist's crooked path from quantum optics to quantum information
Quantum information science has changed our view of quantum mechanics. Originally viewed as a nag, whose uncertainty principles restrict what we can do, quantum mechanics is now seen as a liberator, allowing us to do things, such as secure key distribution and efficient computations, that could not be done in the realistic world of classical physics. Yet there is one area, that of quantum limits on high-precision measurements, where the two faces of quantum mechanics remain locked in battle. I will trace the history of quantum-limited measurements, from the use of nonclassical light to improve the phase sensitivity of an interferometer, to the modern perspective on how quantum entanglement can be used to improve measurement precision, and finally to current ideas on quantum limits on detecting a force.
11/30/2015 Ayana Arce Duke University

Revealing hidden structure at the Large Hadron Collider
A simple model of matter and forces, formulated over four decades ago, allows us to precisely predict the results of contemporary high-energy particle collision experiments, including the hundreds of measurements carried out during Run 1 of the Large Hadron Collider (LHC). Nevertheless, this simple Standard Model is known to be incomplete. Run 2 of the LHC, which began this spring with a higher collision energy, will test whether the fundamental particles of the Standard Model actually hide more complex structures of matter -- or even of space.  I will describe how new developments in the study of jets, which are fascinating structures emerging from the Standard Model strong force, have led to more sensitive measurements with the LHC experiments, and how the information hidden in these jets might be the key to revealing what lies beyond the Standard Model.

2/1/2016 S.J. Gates, Jr. University of Maryland

Could SUSY Be a Sign of an Evolutionary Legacy in The Fundamental Laws of Nature
The concept of supersymmetry (SUSY) was discovered near to the end of the 1960's by physicists. Thus, there has never existed a deep fundamental understanding of its origins. This presentation describes how pursuit of such questions led to the discovery of roles for a new class of discrete graphs, a role for error-correcting codes, Coxeter Groups and other mathematical structures. The answer to the question of why these occur points toward a new possibility, the laws of Nature might have evolved.

2/15/2016 Mark Messier Indiana University
Next Questions in Neutrino Physics and the NOvA Experiment
The discovery of neutrino mass in 1998 spawned a world-wide effort to better understand neutrino properties using neutrinos from the Sun, the atmosphere, reactors, and from accelerators. While much has been learned since then, several important questions remain: which neutrino is heaviest? Are there new symmetries in neutrino mixing? Do neutrinos break the symmetry between matter and antimatter? Is the framework we use to understand neutrinos complete or is there more? The NOvA experiment is designed to address each of these remaining questions and has recently begun operations. I will summarize the important factors that guided the NOvA design, show some highlights from construction, and present the first results from measurements of muon neutrino disappearance and electron neutrino appearance from the experiment.
2/29/2016 George Becker University of California, Riverside
From Reionization to Dark Matter with Quasar Absorption Lines
The majority of matter in the Universe, both baryonic and dark, resides in a vast filamentary network that pervades deep space.  While dark matter dominates by mass, it is currently observed only through its gravitational effects.  The baryons, in contrast, can be studied in rich detail, and their properties tell us about the interaction between galaxies and their environments, as well as the nature of the underlying dark matter.  I will describe how absorption lines in the spectra of distant quasars reveal the properties of intergalactic baryons over more than 90% of cosmic history, and how this allows us to address a variety of astrophysical and cosmological questions.  In particular, I will focus on our attempts to answer (1) How and when were the baryons in deep space (re-)ionized by the first galaxies? and (2) How cold (or warm) is dark matter?  These projects combine data from the largest optical telescopes with advanced numerical simulations, and promise to complement next-generation efforts to study the earliest stages of cosmic galaxy and structure formation.
3/7/2016 Liam McAllister Cornell University
Inflation, String Theory, and the CMB
Two decades of progress in experimental cosmology have revealed an astonishingly sharp picture of the first moments of cosmic history.  All observations agree with the broad-brush predictions of inflationary theories, and strongly suggest that quantum fluctuations of an inflation field formed the seeds for the structure in the universe.  Phenomenological models of inflation are well-established, but the microphysical laws underlying inflation are unknown, and are necessarily rooted in a theory of quantum gravity, such as string theory.  This connection to the physics of the Planck scale is particularly powerful in theories that give rise to detectable primordial B-mode polarization in the CMB: the B-modes are the imprint of quantum fluctuations of the gravitational field during a period of inflation at energy densities of order the GUT scale. I will describe the successes and limitations of inflation, then explain the role of quantum gravity in the study of the very early universe.
3/21/2016 Leo Radzihovsky University of Colorado
Critical matter, chiral symmetry breaking and emergent Higgs mechanism
The upshot of extensive studies of fluctuations is that their qualitative importance typically confined to isolated critical points of continuous transitions between phases of condensed matter. This conventional wisdom also predicts the number of low energy Goldstone modes based on the pattern of symmetry breaking. I will discuss condensed matter systems, that violate this standard paradigm via an emergent Higgs mechanism. Even more spectacularly, these systems exhibit “critical” ordered phases, with universal power-law properties reminiscent of continuous phase transition, but without any fine-tuning and extending throughout the ordered phase. The most interesting recent example is the twist-bend nematic liquid crystal —— a homogeneous liquid that spontaneous breaks chiral symmetry.
4/4/2016 AO Williams Lecture: David Gross, University of California, Santa Barbara
The frontiers of fundamental physics

 At the frontiers of physics we search for the principles that might unify all the forces of nature and we strive to  understand the origin and history of the universe. In this lecture I shall describe some of the the questions that we ask and some of the proposed answers. I shall also discuss what it might mean to have a final theory of fundamental physics and whether we are capable of discovering it.

4/11/2016 Slava Rychkov CERN
The conformal bootstrap approach to criticality in 3 and 2+1 dimensions

The nonperturbative conformal bootstrap has re-emerged in recent years as a powerful technique to compute properties of the critical state of matter. Starting from the key assumption - that the critical theory possesses conformal symmetry - and other experimentally justifiable assumptions like the internal symmetry group and the number of relevant (in the RG sense) couplings, the conformal bootstrap allows to find allowed regions in the parameter space of the CFT data. These constraints are universal - they should be satisfied by any microscopic theory satisfying the assumptions. For some universality classes like that of the 3d Ising model and the O(N) model the constraints are surprisingly sharp, for reasons which are as yet mysterious. They provide the world’s most precise determinations of the critical exponents and transport coefficients for these models. We will review the method, which has its roots in high energy physics, and the fruitful interplay now taking place with the condensed matter physics.

4/13/2016 Barry Barish CalTech
Black Holes, Gravitational Waves and LIGO

Einstein predicted the existence of gravitational waves 100 years ago.  They have been recently observed from a pair of merging Black Holes by the Laser Interferometer Gravitational-wave Observatory (LIGO).   The physics of gravitational waves, the detection technique, the observation and its implications will all be discussed.

4/18/2018 Xiaoxing Xi Temple University
Building Nanoscale Oxide Thin Films and Interfaces One Atomic Layer at a Time

Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show that atomic layer-by-layer laser molecular-beam epitaxy significantly advances the state of the art in constructing oxide materials with atomic layer precision. Using Sr1+xTi1-xO3 and Ruddlesden–Popper phase Lan+1NinO3n+1 (n = 4) as examples, we demonstrate the effectiveness of the technique in producing oxide films with stoichiometric and crystalline perfection. By growing LaAl1+yO3 films of different stoichiometry on TiO2-terminated SrTiO3 substrate at high oxygen pressure, we show that the behavior of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface can be quantitatively explained by the polar catastrophe mechanism. In LaNiO3 films on LaAlO3 substrate with LaAlO3 buffer layer, we observed the metal insulator transition in 1.5 unit cells, which is driven by oxygen vacancies in addition to epitaxial strain and reduced dimensionality.

5/2/1026 Joe Howard Yale University
Swimming of micro-organisms: Collective motion driven by molecular motors

The beating patterns of sperm flagella and the breast-stroke like swimming strokes of cilia are driven by the molecular motor dynein. This motor protein generates sliding forces between adjacent microtubule doublets within the axoneme, the motile cytoskeletal structure. To create regular, oscillatory beating patterns, the activities of the dyneins must be coordinated, both spatially and temporally. It is thought that coordination is mediated by stresses or strains that build up within the moving axoneme, but it is not known which components of stress or strain are involved, nor how they feed back on the dyneins. To answer this question, we have measured the beating patterns of isolated, reactivate axonemes of the unicellular alga Chlamydomonas reinhardtii. We compared the measurements in wild-type and mutant cells with models derived from different feedback mechanisms. We found that regulation by changes in axonemal curvature was the only mechanism that accords with the measurements.







9/8/14 Hirosi Ooguri Caltech Spradlin
  "The Power of Topology in Superstring Theory" (Video)
Superstring theory is the leading candidate for the ultimate unified theory of all the matters and forces in nature. It postulates that fundamental building blocks are not point particles but strings, and it is defined in (9+1)-dimensional spacetime. The rich structure in particle physics in our (3+1) dimensions, such as quark and lepton flavors, gauge forces, and the Higgs boson to break the gauge symmetry, is expected to emerge from the geometry of the extra 6 (= 9 - 3) dimensions, called a Calabi-Yau space. We want to derive quantitative predictions on our universe from the geometry of the Calabi-Yau space. However, the Calabi-Yau space is so complicated that we do not even know an expression for its metric, namely how to measure the distance between two points on the space. Given this limitation, what can we do? In this talk, I will describe techniques we have developed to overcome this difficulty and applications of these techniques to problems in physics and mathematics.
9/15/14 Seth Lloyd MIT Lowe
  "Quantum life" (Video)
Nature is the great nanotechnologist: life is based on a myriad of interlinked mechanisms that operate at the molecular scale.   The dynamics of these mechanisms are governed by quantum mechanics.   Quantum mechanics famously exhibits strange and counterintuitive effects based on quantum coherence and entanglement.   Does such `quantum weirdness' play a role in the functioning of living systems?   Recent experimental investigations of photosynthesis indicate that quantum coherence may play an important role in optimizing energy transport in photosynthetic complexes.    This talk presents a general theory that shows how quantum coherence can dramatically enhance energy transport in photosynthesis and in artificial systems.   Optimal energy transport takes place at the point where the timescales for dynamic and static disorder converge, a phenomenon called the quantum Goldilocks effect.
9/22/14 Vijay Balasubramanian  UPenn Spradlin
  "The Maps Inside Your Head" (Video)
How do our brains make sense of a complex and unpredictable world? In this talk, I will discuss a physicist's approach to the neural topography of information processing in the brain. First I will review the brain's architecture, and how neural circuits map out the sensory and cognitive worlds. Then I will describe how highly complex sensory and cognitive tasks are carried out by the cooperative action of many specialized neurons and circuits, each of which has a simple function. I will illustrate my remarks with one sensory example and one cognitive example. For the sensory example, I will consider the sense of smell ("olfaction"), whereby humans and other animals distinguish vast arrays of odor mixtures using very limited neural resources. For the cognitive example, I will consider the "sense of place", that is, how animals mentally represent their physical location. Both examples demonstrate that brains have evolved neural circuits that exploit sophisticated principles of mathematics - principles that scientists have only recently discovered.
9/29/14 David Goldhaber-Gordon Stanford University Feldman

"Novel Phenomena Driven by Interactions and Symmetry-breaking in Graphene" (Video)
Ten years ago, it was amazing that a single atomic layer of carbon -- graphene -- could conduct electricity. Recent developments have led to graphene in which electrons flow more freely at room temperature than in any semiconductor 2D electron system. At low temperature, electrons can travel more than 10 microns without being deflected [1,2]. In these ultraclean samples, interactions and substrate-induced symmetry breaking lead to novel phenomena . I will speak about a few examples of such phenomena, including:


* Insulating behavior at the charge neutrality point at zero magnetic field [3]
* Spin-selective equilibration of quantum Hall edge states [4]
* A large set of fractional quantum Hall states, at denominators up to 9, with unexpected patterns of stability and spin polarization [5]
* The role of screening by a nearby gate electrode

[1] C. R. Dean, A. F. Young, I.Meric, C. Lee, L. Wang, S. Sorgenfrei, K. Watanabe, T. Taniguchi, P. Kim, K. L. Shepard and J. Hone, "Boron nitride substrates for high-quality graphene electronics," Nature Nanotechnology 5 , 722 - 726 (2010) 
[2] Lei Wang, Inanc Meric, Pinshane Y. Huang, Qun Gao, Yuanda Gao, Helen Tran, Taniguchi Takashi, Watanabe Kenji, Luis M. Campos, David A. Muller, Jing Guo, Philip Kim, James Hone, Ken L. Shepard, Cory R. Dean “One-Dimensional Electrical Contact to a Two-Dimensional Material"Science 342, 614-617 (2013).
[3] F. Amet, J. R. Williams, K. Watanabe, T. Taniguchi, D. Goldhaber-Gordon, "Insulating Behavior at the Neutrality Point in Single-Layer Graphene" Physical Review Letters 110, 216601 (2013).
[4] F. Amet, J. R. Williams, K. Watanabe, T. Taniguchi, D. Goldhaber-Gordon, "Gate control of spin and valley polarized quantum Hall edge states in graphene," arXiv:1307.4408. To be published in PRL.
[5] F. Amet, A. J. Bestwick, J. R. Williams, K. Watanabe, T. Taniguchi, D. Goldhaber-Gordon Composite Fermions and Broken Symmetries in Graphene. Under review.

10/6/14  Valerie Connaughton NASA Koushiappas

"Terrestrial Gamma-Ray Flashes: Particle accelerators in our atmosphere" (Video)
Terrestrial gamma-ray flashes (TGFs) were discovered in 1991 by the Burst And Transient Source Experiment (BATSE) on the Compton Gamma-ray Observatory as mysterious bursts of high-energy radiation appearing to come from areas of thunderstorm activity.  Since then, they have been detected on three additional satellite experiments including the Gamma-Ray Burst Monitor (GBM) on-board the Fermi satellite.  Our understanding of the relationship between TGFs and coincident Very Low Frequency (VLF) radio signals has evolved considerably in the Fermi GBM era, with some VLF signals coming from lightning associated with the TGFs and others from the TGFs themselves.  This has given us new insights into the physical processes responsible for TGFs and their relationship to lightning processes in general.   I will discuss the Fermi GBM TGF observations, with special attention to their association with VLF radio signals detected on the ground.



In terms of visiting with faculty, I would be interested in meeting with anyone who is interested in meeting with me!  I have interest in but not expertise in elementary particle experiments and theory.  In addition to working in space-based gamma-ray astrophysics I am also involved in the Cherenkov Telescope Array and I think there would be some common interests with Prof. Gaitskell in the area of dark matter detection and with Prof. Koushiappas because of our common interest in Fermi.

10/20/14 Valery Pokrovsky  Texas A&M University Feldman

"Bose-­Einstein condensation of spin waves in YIG" (Video)
In 2006 the experimental group from University of Münster (Germany) had discovered the phenomenon of Bose-­‐Einstein condensation of spin waves (magnons) in a ferromagnet YIG (Yttrium-­‐Iron garnet) at room temperature. They pumped low-­‐energy magnons with external electro-­‐ magnetic field in GHz range of frequency in a film of YIG. More recently (2012) the same group discovered a low-­‐contrast interference pattern in the intensity of signal generated by the condensed magnons. This interference demonstrates the coherence between two condensates corresponding to two minima of magnons energy. Surprisingly, the oscillations displayed very low contrast that had no explanation in the framework of existing theories. In the work by Fuxiang Li, W.M. Saslow and VLP [Scientific Reports 3, 01372 (2013)] we proposed a theory explaining the coherence and low level of contrast. Our theory predicts that in thinner films it is possible to observe a different state of condensates with 100% contrast. The transition between the two states can be driven by a weak magnetic field. We predict the phase trapping between two condensates with two possible states 0 and π. Its experimental observation is feasible with traditional means (Brilloin scattering of light). Theory also predicts a new type of low-­‐energy
collective oscillations.

10/27/14  Nandini Trivedi Ohio State University Valles
   "Quantum Fluctuations and Phase Transitions" (video)
I will discuss the role of quantum fluctuations in driving phase transitions and contrast them with the better understood thermally driven phase transitions. I will show how standard paradigms break down and novel phases of matter emerge in the context of superconductor-insulator phase transitions and discuss our predictions for experimental probes through local spectroscopies and dynamics. These concepts have overlaps with cold atoms and AdS/CFT that I will illustrate.
[1] Bouadim, Loh, Randeria and Trivedi, “Single- and two-particle energy gaps across the disorder-driven superconductor–insulator transition”, Nature Physics 7, 884 (2011).
[2] Swanson, Loh, Randeria and Trivedi, “Dynamical Conductivity across the Disorder-Tuned Superconductor-Insulator Transition”, Phys. Rev. X 4, 021007 (2014)
11/3/14 Scott Watson Syracuse University Koushiappas
  "Cosmology as a Probe of Physics Beyond the Standard Model" (video)
Abstract: Cosmological observations provide overwhelming evidence that our universe is almost entirely comprised of dark energy and dark matter, both of which have no theoretical explanation within the standard model of particle physics. The former is responsible for a current period of cosmic acceleration, much like that which occurred in the earliest moments of the universe. The early period of cosmic acceleration, known as inflation, was vital in providing the primordial seeds from which galaxies and clusters formed, whereas the late time acceleration could eventually lead to the vanishing of most structure in the universe. The driving force behind cosmic acceleration, as well as dark matter, still remains elusive from the point of view of a microscopic theory. Combined with fundamental questions, such as the origin of particle mass and how electroweak symmetry is broken, these conundrums require physics beyond the standard model. In this talk I will review both the theoretical and observational status of these issues with an emphasis on the excitement surrounding current and upcoming experiments.
11/10/14 Patrick Lee  MIT Feldman
  "Emergence from frustration: spin liquid and high temperature superconductivity" (video)
I shall describe some recent development in frustrated spin systems and show that these are prime examples of the notion of emergence: novel particles and fields not present in the original Hamiltonian emerging at low energy. I then show that some of these ideas may be applied to understand the pseudo-gap phase of high temperature superconductors.  
11/17/14 Eric Mazur (MIT) - CANCELLED 
11/24/14 James Olsen Princeton University Landsberg
  "Nature of the New Boson: a lonely Higgs, or one of many cousins?" (video)
Recent measurements from the ATLAS and CMS experiments indicate that the new boson discovered in 2012 at the Large Hadron Collider (LHC) at CERN is a Higgs boson.  In the standard model of particle physics, one Higgs boson is sufficient to give mass to the W and Z particles, as well as the fundamental fermions (quarks and leptons), while also ensuring that the photon remains massless.  Although this is the most economical scenario that explains electroweak symmetry breaking and the origin of fundamental particle masses, motivated extensions of the standard model predict multiple Higgs bosons with a rich phenomenology that could be detectable at the LHC.  In this colloquium I will present an overview of what we have learned about the Higgs boson from measurements based on the 2011-2012 data run, discuss the status of searches for additional Higgs particles, and close with a brief summary of prospects for the coming LHC run at higher energy scheduled to begin in spring, 2015.
12/1/14 Savvas Koushiappas   Brown University Valles

"The structure of the universe as a link between cosmology and dark matter physics"
Cosmological structure formation gives rise to a distribution of dark matter that is set by the complex processes of non-linear collapse. Dark matter searches are inextricably linked to the details of this cosmological structure formation. I will review how large scale structure gives rise to our present expectations for the dark matter particle, and how experimentally-motivated theorists try to bridge the gap between fundamental cosmological ideas and dark matter detection experiments. 



Carlton Caves 

University of New Mexico



Cancelled - Rescheduled for 11/23/15


Vidya Madhavan

U. of Illinois at Urbana-Champaign



Cancelled - Rescheduled for 11/16/15


David Weitz 




Cancelled - Rescheduled for 10/5/15


Jané Kondev 




"The Physical Genome"  (Video)
Every day there seems to be a story in the news about DNA and some gene that it encodes. While this abstraction of DNA as an information storage device is useful, in this talk I will consider the physical nature of DNA, namely the fact that it is a long, flexible, and charged molecule. This is important because the physical properties of DNA affect a number of critical functions that it performs in the cell. One such function is to turn on and off the production of proteins, which are the building blocks of the cell,  in response to different physical and chemical ques. Another is to repair itself when breaks occur. In this talk I will describe how simple physics models combined with experiments on cells and single molecules are being used to develop a quantitative understanding of the physical genome.


Julio Navarro

University of Victoria



"Dwarf Galaxies as Cosmological Probes" (Video)
A prime challenge to our understanding of galaxy formation concerns the scarcity of dwarf galaxies compared with the numerous low-mass halos expected in the current ΛCDM paradigm. This is usually accounted for by assuming that energetic feedback from evolving stars confines dwarf galaxy formation to relatively massive halos spanning a narrow mass range. I will highlight a number of observations that may be used to test this assumption and discuss the puzzles and challenges that arise from this analysis. I will also discuss a number of challenges that ΛCDM faces on the scale of dwarf galaxies and their possible resolutions.


Benjamin Wandelt

Sorbonne University



“The Physics of the Cosmos: from the Big Bang to the Cosmic Web” (Video)
The cosmic microwave background (CMB) carries a cosmic message, preserved through time, written in its anisotropies. The Planck mission has just revealed a new chapter of this message using high-resolution nearly all-sky information of the polarization anisotropies for the first time, in addition to upgrading from the nominal mission to the full mission data set. These data provide new insights into several open questions related to the nature of the primordial fluctuations that seeded all structure; the global properties of the universe; neutrinos; dark matter; dark energy; atomic physics; and gravity. Beyond the CMB I will describe how new physics-based analysis methods of astronomical data sets allow us explore our cosmic past on and off the light cone and understand the origin and evolution of large scale structure of the Universe in unprecedented detail.


Tiziano Camporesi




"Elementary ! Is this the right answer ?" (Video) 
With the discovery of the Higgs Boson, Quantum field theory has established itself as the theoretical framework to address the fundamental questions and elementary particle physics the way to confirm it experimentally.  Paradoxically this success of the Standard Model is also highlighting the fundamental questions which we have difficulty to answers: the problems in including gravitation in the Standard model framework, the issue of understanding the nature of the elusive Dark Matter or the failure to explain why there is only Baryons and not Anti-Baryons in our universe are clear evidence that our description of nature is incomplete.  In this colloquium, after recollecting the recent successes of Elementary particle physics through the achievements of one of the large experiments at the LHC accelerator, CMS, I will show what can be expected from the future runs: in a few weeks the LHC will break a new energy frontier when it will restart with protons colliding at 13 TeV center of mass energy and this will allow a new exciting run with the potential to access new physics phenomena in the near future.  The CERN council has also approved a long term plan which will be extending the operation of the LHC for the next 20 years providing a program which will increase the luminosity of the Accelerator by factor of 5 and creating the intensity frontier program of the future: I will also show examples of what can be achieved from this long term program.


Gary Horowitz

UC Santa Barbara



"The Remarkable Power of General Relativity" (Video)
This is the 100th anniversary of Einstein's discovery of general relativity.  This theory has been very successful in reproducing a wide range of gravitational phenomena. I will briefly review this success, and then explain how general relativity can describe other areas of physics as well, including aspects of particle physics and condensed matter physics. This is a result of the gauge/gravity duality that emerged from string theory. I will explain this remarkable development and show how general relativity reproduces properties of QCD and superconductivity.


William Irvine

University of Chicago



"The life of a vortex knot: Linking coiling and twisting across scales"  
Can you take a vortex loop - akin to a smoke ring in air - and tie it into a knot or a link? The possibility of such knottiness in a fluid has fascinated physicists and mathematicians ever since Kelvin¹s 'vortex atom' hypothesis, in which the atoms of the periodic table were hypothesized to correspond to closed vortex loops of different knot types.  More recently, the knottiness (Helicity) of a fluid has re-emerged as a conserved quantity in many idealized situations (such as Euler fluids and ideal plasmas) offering the potential for new fundamental insights. In the real physical counterparts to these systems progress has however been hindered by lack of accessible experimental systems. I will tell of how to make a vortex knot and link in water, in the wave function of a superfluid (on a computer) and of what happens thence. In particular I will talk about how linking coiling and twisting interplay across scales.


Sumit Das

University of Kentucky



Over the last couple of decades it has become clear that in many situations gravity can be thought of as an emergent, "dual" description of non-gravitational gauge theories in lower number of dimensions. This realization is a key ingredient in our current understanding of the quantum physics of black holes in terms of the properties of the underlying gauge theory. In the other direction, this duality has been used to address difficult issues in strongly coupled field theories, by mapping them to classical problems in gravity. This talk will discuss the physical origins of this duality and its modern applications to the understanding of far from equilibrium properties of strongly coupled systems, and attempts to uncover the mysteries of big-bang like singularities.

AO Williams Lecture


Rolf Heuer

Director-General, CERN

AO Williams Lecture


“Breaking the wall of the hidden universe - what the discovery of the Higgs boson tells us about Physics, Mankind and the Universe“ (Video)
With the start of the Large Hadron Collider (LHC) at CERN, particle physics entered a new era. The LHC will provide a deeper understanding of the universe and the insights gained could change our view of the world, and the talk will present some of the reasons for the excitement surrounding the LHC. The LHC is expected to yield insights into the origin of mass, the nature of dark matter and into many other key questions. This lecture will address the exciting physics prospects offered by the LHC, discuss in particular the recent discovery of the Higgs-Boson, and present a look forward




9/9/13 Stephon Alexander Dartmouth College Valles & Jevicki
  "Observational and Theoretical Implications of a Parity Violating Universe"
So far, only the weak interaction maximally violates parity symmetry.  In this colloquium, after a pedagogical overview of modern cosmology, we will explore the possibility that the gravitational force may also violate parity.  I show that in the context of early universe cosmology, this parity violation, revealed through gravitational waves during the epoch of cosmic inflation, can explain the observed cosmic matter-anti matter asymmetry.  I also discuss current and future CMB polarization experiments which will attempt to detect the signals of cosmic parity violation.
9/16/13 Baylor Fox-Kemper Brown University Marston
  "Modeling the Earth:  Physics, Dynamics, and Numerics"
Not so long ago, the modeling of the atmosphere, ocean, cryosphere, and other components of the Earth System were carried out by distinct groups of investigators with relatively narrow research goals in understanding their own "sphere."  However, the drive to understand the climate, and particularly human influences on climate now and in possible future scenarios has led to climate modeling of much grander scope and ambition.  I will present the ingredients of a climate model, from the simplest planetary energy balance models to a schematic of the present day models.  I will present some of my own work in improving these models and present prospects for future improvements, through better computers and through better understanding.
9/23/13 Steven Carlip UC Davis Lowe
  "Spontaneous Dimensional Reduction?"
The general theory of relativity tells us that what we call gravity is really a manifestation of the geometry of space and time.  The basic unsolved problem of quantum gravity is to understand the structure of this spacetime at the smallest scales.
Several recent lines of evidence hint that spacetime at very small distances may undergo "spontaneous dimensional reduction," behaving as if it had only two dimensions rather than four.  I will summarize some of the evidence for this strange behavior, and discuss a further argument based on the effect of quantum fluctuations on light cones.  If this description proves to be correct, it suggests an unexpected relationship between small-scale quantum spacetime and the behavior of cosmology near a "typical" big bang.
9/30/13 Christoph Boehme University of Utah Mitrovic
  "Promises and Challenges of Organic Spintronics"
While the term “Spintronics" was originally introduced as label for technologies that represent information through spin states rather than charge states, it is nowadays oftentimes used solely in the context of spin-polarization, spin-injection, and spin-transport effects for which spin-orbit interaction plays an important role. Silicon and carbon based semiconductors display only weak spin-orbit coupling and - in the case of organic semiconductors - charge transport via hopping through strongly localized states. These materials appear at first glance therefore to be entirely unsuitable for spintronics. However, they also exhibit spin related effects not seen in materials with strong spin-orbit coupling which can be used for alternative, different approaches to spintronics based on spin-permutation symmetry states of charge carrier pairs rather than spin-polarization states. Reading spin-permutation symmetry is straight forward when pronounced spin-selection rules exist1,2. In contrast to spin-polarization, permutation symmetry does not depend directly on temperature and magnetic field strength3. Furthermore, the absence of spin-orbit coupling can also allow for long spin-coherence times and thus, the possibility to connect spintronics to an all spin based memory which may be applicable to spin-based quantum information4 concepts and for similar reasons, it allows for magnetic resonance based spin-manipulation schemes. Crucial for the successful implementation of organic spintronics will be a fundamental understanding of the microscopic electronic processes which are aimed to be utilized for this new technology, a requirement which has only partially achieved. Developing this understanding will be among the most important challenges of this field5. In this talk, our work on the development of this organic spintronics will be presented and the issues at hand as well as the progress made will be discussed.
[1]       D. R. McCamey, H. A. Seipel, S. Y. Paik, M. J. Walter, N. J. Borys, J. M. Lupton, and C. Boehme, Nature Materials, 7, 723 (2008).
[2]       D. R. McCamey, K. J. van Schooten, W. J. Baker, S.-Y. Lee, S.-Y. Paik, J. M. Lupton, and C. Boehme, Phys. Rev. Lett. 104, 017601 (2010).
[3]       W. J. Baker, K. Ambal, D. P. Waters, R. Baarda, H. Morishita, K. van Schooten, D. R. McCamey, J. M. Lupton, and C. Boehme, Nature Commun. 3, 898 (2012).
[4]       W. J. Baker, T. L. Keevers, J. M. Lupton. D. R. McCamey, and C. Boehme,  Phys. Rev. Lett. 108, 267601 (2012).
[5]       C. Boehme and J. M. Lupton, Nature Nano. 8, 612 (2013).
10/7/13 Benjamin Wandelt Sorbonne University Tucker
  Professor Wandelt is Professor and International Chair of Theoretical Cosmology at the Paris Institute for Astrophysics (IAP) at the Université Pierre et Marie Curie, Sorbonne University.

"Cosmic Past, Present, Future: Planck and Beyond"
How can we learn what banged at the Big Bang? We use astronomical observations to probe the epoch in the very early Universe where quantum fluctuations imprinted the seeds of cosmic structure. I will summarize the main results of the analysis of the cosmic microwave background temperature anisotropies as seen by the Planck mission data released in March 2013, with special emphasis on the non-Gaussianity analysis which resulted in the highest precision tests to date of physical mechanisms for the origin of cosmic structure. Then I will turn to the future and highlight the challenges and opportunities of the next generation of probes of the large scale structure of the universe aiming to piece together the outstanding puzzles of cosmic past, present, and future - with some glimpses onto the lab bench of innovative approaches that are now emerging.

10/21/13 Nina Emery Brown University (Department of Philosophy) Marston
  "Simplicity and Skepticism in Quantum Mechanics"
On a straightforward ontological reading of all viable, realist interpretations of quantum mechanics, we do not inhabit the familiar three-dimensional space of our everyday experience. Instead we inhabit a very high-dimensional configuration space. I examine the arguments for and against this sort of straightforward ontological reading, and compare the resulting theories with more familiar skeptical hypotheses, like the hypothesis that we are in the Matrix, or the hypothesis that we are part of a computer simulation.
10/28/13 Marc Kamionkowski John Hopkins University Koushiappas
  "Cosmic Beauty and Blemishes"
The vast majority of the wealth of cosmological information we have has come from power spectra (or equivalently, two-point correlation function, for the CMB temperature and for the mass distribution in the Universe today.  But there is far more that can be sought in the future with the deluge of data from current and forthcoming surveys.  I will discuss how the data can be used to look for new fields during inflation; to test geometrically for their properties; to seek parity breaking in the early and late Universe; to look for exotic dark-energy physics; to inquire about nontrivial cosmic topologies; to identify preferred-frame effects; etc.  I will also then comment on a possible surprise in the CMB data.
11/4/13 Richard Gaitskell Brown University Valles

Professor Gaitskell will present and discuss the first results from the LUX (Large Underground Xenon) dark matter detector experiment at the Sanford Underground Research Facility in Lead, SD. Video

11/11/13 Andreas Ludwig UC Santa Barbara Feldman
  "Topological Insulators and Superconductors" (Video)
Topological Insulators (and Superconductors) are quantum phases of non-interacting Fermions which are electrical (or thermal) insulators in the bulk, but whose boundaries conduct electrical current (or heat) like a metal. These boundaries are very special and unusual conductors in that they are ("holographically") protected by the topological nature of the quantum state of the bulk material. The first examples of such phases were theoretically predicted less than a decade ago and were discovered experimentally shortly thereafter in two- and three-dimensional electronic systems. Topological Insulators have attracted significant interest as fundamentally novel electronic phases. They can be viewed as generalizations of the Two-Dimensional Integer Quantum Hall effect to systems in different dimensions and with different symmetry properties. For example, they can occur in three dimensions and in the absence of a time-reversal breaking magnetic field. - Here we give an introduction to these systems, and will explain the basic ideas underlying an exhaustive classification scheme of all Topological Insulators (and Superconductors), which links these systems of relevance for Condensed Matter laboratory experiments to a variety of general notions in Theoretical Physics and Mathematics.
11/18/13 Lyderic Bocquet Institut Lumière Matière, Université Lyon Stein

"Fluid transport at the nanoscales and application to osmotic energy harvesting" (Video)
"There is plenty of room at the bottom". This visionary foresight of R. Feynman, introduced during a lecture at Caltech in 1959, was at the root of numerous scientific and technological developments, taking benefit of the "strange phenomena" occurring at the smallest scales. There remains however a lot to explore, in particular in the context of fluids at the nanoscales and their specific transport properties. The great efficiency of biological nanopores, such as aquaporins, in terms of permeability or selectivity is definitely a great motivation to foster research in this direction. How to reach such efficiency in artificial nano-systems, and build new devices taking benefit of the strange transport behavior of fluids at nanoscales is still an open question.
I will discuss several results obtained in our group on the fluid transport at the nanoscales, in particular inside nanopores, nanochannels and nanotubes. I will then focus on the study of transport inside a single Boron-Nitribe nanotube. Using a nano-assembly route with nanostructures as building block, we have built a dedicated trans-membrane nanofluidic device allowing to study fluid and ionic  transport across a single nanotube. Experiments show unprecedented energy conversion from salt concentration gradients. Applications in the field of osmotic energy harvesting will be discussed.
"Giant osmotic energy conversion measured in a single transmembrane boron-nitride nanotube", A. Siria, P. Poncharal, A.-L. Biance, R. Fulcrand, X. Blase, S. Purcell, and L. Bocquet, Nature 494 455-458 (2013)
"Optimizing water permeability through the hourglass shape of aquaporins",
S. Gravelle, L. Joly, F. Detcheverry, C. Ybert, C. Cottin and L. Bocquet, Proc. Nat. Acad. Sci. USA 110 16367 (2013)   
"Soft nanofluidic transport in a soap film", O. Bonhomme, O. Liot, A.-L. Biance, and L. Bocquet, Phys. Rev. Lett. 110 054102 (2013)

11/25/13 Chandrasekhar Ramanathan Dartmouth College Mitrovic
  "Quantum simulation with nuclear spins" (Video)
It has been three decades since Feynman showed that a quantum computer is required to efficiently simulate a quantum system.  While building a quantum computer remains a grand challenge, our improved ability to manipulate and control quantum systems has led to a resurgence of interest in quantum simulations that could help tackle problems in diverse areas such as condensed-matter physics, cosmology and quantum chemistry.    In this talk I will discuss how to build quantum simulators using nuclear magnetic resonance (or NMR) techniques.  While we can perform any small-scale simulation using liquid state NMR, the highly-coupled spin networks in solids allow us to perform a more limited set of large-scale analog quantum simulations.  These solid state spin systems are excellent platforms on which to study the coherent dynamics of large quantum systems.   I will illustrate these ideas with experimental examples, and discuss the key challenges to developing large scale, general purpose quantum simulators.
12/2/13 Cornelia Dean Brown University/The New York Times Valles
  "The Physics of The New York Times"  (Video)
In modern times, few realms dominate science -- and the popular imagination -- like physics and cosmology. For more than 100 years, The New York Times has attempted to bring these fields to life for its readers. Cornelia Dean, a science writer and former Science Editor of the newspaper will discuss this coverage in a colloquium on 12/2/13. Ms. Dean, the editor of a new collection of Times articles on physics and astrophysics, will discuss how some notable stories came to be, the difficulties of writing about highly technical subjects for a lay audience, and the difficulties that lie ahead for coverage of science.
1/27/14 George Zweig MIT Landsberg

"Concrete Quarks - The Beginning of the End" (Video)
A short history of the physics of strongly interacting particles is presented. Events leading to the discovery, and eventual acceptance, of concrete quarks are described.

2/10/14 Joao Guimaraes de Costa Harvard University Narain

"A Closer Look at the Higgs Boson with the Large Hadron Collider" (Video)
Scientists at CERN have been exploring the high energy frontier with the Large Hadron Collider since March 2010. The substantial dataset accumulated thus far, albeit at lower energy than initially foreseen, already yielded a Nobel prize award for the discovery of the Higgs Boson.
The new boson, discovered in 2012 by the ATLAS and CMS collaborations, has been shown to behave very much like the long-sought-after Higgs Boson, and hence it completes the discovery of the Standard Model of Particle Physics.  Remarkably, no other deviations from the Standard Model have been found, neither in precision measurements nor in direct searches for new particles. The LHC will resume operations in 2015, after a 2-year shutdown, with increased center of mass energy, and thus, with increased potential for new discoveries. In this talk, I will review recent measurements at the LHC, with a focus on the study of the properties of the newly discovered boson, and will briefly discuss what we expect to learn from the future LHC data.

2/24/14 David Pine New York University Stein

"Colloids with directional interactions" (Video)
We have developed new kinds of colloidal particles with either geometrical or chemical patches that give rise to directional interactions.  These interactions allow colloids to interact with each other more like atoms, which in turn are used to build up structures that are not possible with isotropic interactions.  These directional interactions are being developed to make self-replicating colloidal motifs and new colloidal crystals.

3/3/14 Raymond Brock Michigan State University Heintz

"That Spin 0 Boson at CERN Changes Everything: The Future of the Energy Frontier in Particle Physics" (Video)
I’ll argue that the "Higgs Boson" discovery requires us to think differently about planning for the future of Particle Physics. While the decades-long confirmation of the Standard Model itself an historic episode in the history of physics, as a model of nature it is unhelpful as a clear guide to the future. I’ll review the features of the Standard Model that make it superb, I’ll point out why it’s frustrating, and I’ll describe the hints that motivate us in the coming decades. Last year the particle physics community went through a self-study of future opportunities. I’ll review some of the “Snowmass Workshop” especially as it pertains to the future of collider physics.

3/10/14 Joshua Winn MIT Tucker

"Spin-Orbit Interactions for Exoplanets" (Video)
In the Solar system, the planets follow orbits that are aligned with the Sun's equatorial plane to within a few degrees.  But what about planets around other stars?  Recently we have measured the spin-orbit angles of about 50 stars with exoplanets, using a technique first theorized in the 19th century, as well as several new techniques based on data from the NASA Kepler spacecraft.  Many exoplanetary systems have good alignment, as in the Solar system -- but there are also many surprises.  I will discuss these results and their implications for theories of planet formation, and tidal spin-orbit interactions.  I will also describe the Transiting Exoplanet Survey Satellite, a NASA mission that will improve upon Kepler by discovering exoplanets around stars that are brighter, closer to the Earth, and easier to study.

3/17/14 Raul Jimenez University of Barcelona Koushiappas

"Large scale structures, their statistics, neutrino masses and fundamental Physics" (Video)
Mapping the large scale structure of the Universe has provided us with an exquisite 3D view of the development and growth of structure since the Big Bang. Now that we have a well established standard cosmology model (LCDM), it is possible to learn fundamental physics from the statistics of large scale structures. In this talk I will describe how we can learn about neutrino physics (in particular about the absolute mass scale and its hierarchy), axion physics, dark energy and dark matter. In summary: the Universe provides an outstanding tool to learn about how nature has decided to extend the standard model of particle physics; I will discuss new developments on this front as well.

3/31/14 Igor Herbut Simon Fraser University Mitrovic

"Fundamental physics with two-dimensional carbon" (Video)
The two-dimensional form of carbon, also known as graphene, has been hailed as wonder material promising, and already delivering, many useful applications.  This is not the only reason, however, why many theoretical physicists have been fascinated with this new material over the last ten years. The reason is also that the electronic structure of graphene provides an unusually simple and affordable playground for studies of some of the basic concepts of modern quantum physics. In this lecture I will attempt to give an elementary discussion of  three of these: 1) Mott-insulator (or "Higgs")  quantum phase transition, and the emerging relativity, 2) the spontaneous braking of "chiral" symmetry, and the "Dirac masses" of graphene, and 3) the Jackiw-Rebbi zero-modes, topological defects, and their (Clifford) algebras. 

4/7/14 Robert Meyer Brandeis University Pelcovits

Arthur O. Williams Lecture: "Ancient Roman Technology: The Stability of Vaulted Masonry Structures” (Video) (poster)
In imperial Rome, the use of vaulted structures, arches, domes and other forms of vaults, built of stone and concrete, was developed to a degree never seen before.  Bridges and aqueducts were built throughout the empire.  Vast spaces could be enclosed with an economy of material, for use as temples, baths, meeting places, markets, and palaces.  This lecture seeks to develop an understanding of the principles determining the stability of some of these structures, which served as the basis for later developments, including the great cathedrals of the Middle Ages and the Renaissance.

4/14/14 Juan Restrepo University of Arizona Marston

"Estimation Challenges in Climate and the Geosciences" (Video)
Accounting for uncertainties has also led us to alter our expectations of what is predictable and how such predictions compare to nature: in effect, to take on a more Bayesian approach to scientific research as well as to embrace more seamlessly the statistical and deterministic realms.  I will enumerate a few important geoscience problems that live in the realm of the deterministic and the statistical and describe, briefly, our  Group's approach and progress on these.  Among these I will choose a time series analysis project to provide more details on the methods we use to pursue this Bayesian research program.


4/21/14 Ian Fisher Stanford University Mitrovic

"Electronic nematic phases in high temperature superconductors" (Video)
In recent years, anisotropic electronic phases have been discovered in a variety of strongly correlated quantum materials. Borrowing language from the field of soft condensed matter physics, such phases are referred to as electronic nematic phases when they break a discrete rotational symmetry of the crystal lattice without further breaking translational symmetry. The physical origin of electronic nematic order is unclear, as are the implications for other broken symmetry states, including superconductivity, motivating the development of tools and techniques that probe electronic nematicity. In this talk I'll outline a new technique that measures an associated quantity, the nematic susceptibility, which provides important insight to nematic fluctuations in a material. Measurements of this quantity directly reveal the presence of an electronic nematic phase transition in a family of high temperature superconductors, and an associated quantum phase transition near optimal doping (i.e. the doping that yields the maximum critical temperature of the superconductor). I'll explain the possible significance of this observation.

9/17/12 Rouven Essig SUNY, Stony Brook Koushiappas
  "The Hunt for Dark Matter"
Dark matter makes up 80% of the matter in our Universe, but we have yet to learn its identity. Astrophysical probes are becoming powerful enough to inform us on some of its fundamental properties and a wide array of experiments are probing its non-gravitational interactions with ordinary matter.  In this talk, I will review the astrophysical evidence for dark matter and give a broad overview of current and future direct and indirect detection experiments, as well as collider probes.  I will also discuss some of the hints for dark matter at currently running experiments.
9/24/12 Robert Hallock University of Massachusetts, Amherst Valles
  "Is Solid Helium-4 an Example of a 'Supersolid'?  Come, Listen, and See What You Think"
About 40 years ago it was predicted that it might be possible for solid helium to display some of the properties of a superfluid, thus there might be a 'supersolid'.  Experiments in the mid to late 1970’s were negative and the prediction languished.  Then in 2004 an experiment was done that was interpreted as positive evidence for the presence of a 'supersolid' in solid helium.  But, the interpretation has been very controversial and other evidence has complicated the picture.  After a review of some background and a few key experiments, experiments will be described that are conceptually different from all the others. These provide direct evidence to that it is possible to pass helium through a sample cell filled with solid helium .  Some of the recent predictions for 'supersolid' behavior due to theorists differ substantially from the original theory of 40 years ago and these are rather consistent with our observations.  This will be an experimentally oriented talk, designed to be accessible to all.
10/1/12 Brendan Casey Fermilab Heintz
  "The Next Muon g-2 Experiment"
There is a discrepancy between the measured and expected values of an intrinsic property of the muon, its anomalous magnetic dipole moment, aka g-2.  The discrepancy could be an indication of new physics beyond the current standard model of particle physics and leads to predictions that new particles will be found at the LHC.  As an example, within weeks of the discovery of the Higgs at the LHC, papers were submitted correlating the Higgs to gamma gamma branching fraction with the g-2 anomaly.   An extraordinary opportunity has arisen with the successful completion of the Tevatron program at Fermilab.  The infrastructure used to create antiprotons can readily be repurposed to create muons.  The Fermilab accelerator complex will be able to produce close to twenty times more muons than recorded by the last experiment at Brookhaven in less than two years allowing us to measure g-2 to a precision of 140 parts per billion. I will discuss the motivation for the new experiment, the technical difficulties involved in the prediction and measurement, and the progress towards mounting the new experiment.
10/10/12 Greg Landsberg Brown University  
  Special Colloquium:  "Discovery of the Higgs Boson(?) at the Large Hadron Collider"
On July 4th, 2012 the ATLAS and CMS Collaborations at the Large Hadron Collider announced a discovery of a new boson with the mass of 125 GeV, a likely candidate for a long-sought Higgs boson. In this special colloquium I'll give an inside track of the events that lead to this fundamental discovery, explain its importance, and discuss the next steps in uncovering the true nature of the new particle.
10/15/12 Douglas Finkbeiner Harvard University Koushiappas
  "The Galactic Center 130 GeV Line:  WIMP or Artifact?"
The recent claims of a gamma-ray line in the Galactic center at 130 GeV has generated excitement, not least because it could be a signal of dark matter annihilation.  I will summarize the current state of the observations of the Galactic center, clusters, and unassociated halo objects, and speculate about models of particle dark matter that could
explain the data.
10/22/12 David Griffiths Reed College Valles
  "Hidden Momentum"
Electromagnetic fields carry energy, momentum, and even angular momentum. The momentum density is ε_0 (E×B), and it accounts (among other things) for the pressure of light. But even static fields can harbor momentum, and this would appear to contradict a general theorem: if the center of energy of a closed system is at rest, then its total momentum must be zero.  Evidently in such cases there lurks some other momentum, not electromagnetic in nature, which cancels the field momentum. But finding this “hidden momentum” can be surprisingly subtle. I’ll discuss a particularly cute example.
11/5/12 Geralyn Zeller Fermilab Heintz
  "Neutrino Physics: This Decade and Beyond"
Neutrinos are one of nature's strangest and most elusive particles. For more than 50 years, they have surprised us: not only by their mere presence, but also by the revelation that these ghostlike particles can oscillate from one type to another. This stunning discovery has opened up a host of new questions about neutrinos and their properties; questions which we will be trying to answer in the next decade and beyond. In this talk, a survey of recent experimental results will be presented, along with projections for what the future holds. If history is any indication, we are in store for an exciting ride.
11/12/12 David Hammer Tufts University Valles
  "What do the students need?"
The instruction we offer students, at any level, presumably reflects what we believe will help them understand physics.  But we don’t often subject our beliefs to scrutiny.  Most physics instructors work from common sense assumptions about what students need—clear explanations, demonstrations, motivation and practice.  As in physics, however, common sense ideas (e.g. 'objects move because they are pushed') aren't always correct.  I will present evidence that these usual assumptions are insufficient and offer an expanded set of possibilities, focusing in particular on how students understand knowledge and learning.  In many cases what students most need is help taking a different approach to learning, to start thinking of science as a “refinement of everyday thinking” (Einstein, 1936) rather than as a body of new information to memorize.
11/19/12 Stuart Raby Ohio State University Koushiappas
  "The Puzzle of Charge and Mass"     
Beginning with the seminal work of Rutherford, Geiger and Marsden in 1911, physicists have investigated the atom using particle beams  (alpha particles, and protons) as probes. They developed new detection methods; the geiger counter, scintillators, cloud and then bubble chambers.  This new paradigm for probing matter and new detectors led to many discoveries.  To make a long story short, by 1974 the chaos of discovery lead to the Standard Model describing all observed particle phenomena in terms of three fundamental forces (4 including gravity) and the fundamental building blocks of matter, quarks and leptons.  Only now, after the dust of this chaotic discovery settles, are we able with hindsight to recognize the underlying principles which define the theory we call the Standard Model.  It is these principles and their logical extension which I will attempt to describe in this talk.
11/26/12 Joshua Frieman University of Chicago/Fermilab Dell'Antonio
  "The Dark Energy Survey"
The Nobel Prize in Physics for 2011 was awarded for the discovery that the expansion of the Universe is accelerating. Yet the physical origin of cosmic acceleration remains a mystery. The Dark Energy Survey (DES) aims to address the questions: why is the expansion speeding up? Is cosmic acceleration due to dark energy or does it require a modification of General Relativity? If dark energy, is it the energy density of the vacuum (Einstein's cosmological constant) or something else? The Dark Energy Survey will address these questions by measuring the history of cosmic expansion and of the growth of structure through four complementary techniques: galaxy clusters, large-scale galaxy clustering, weak gravitational lensing, and supernovae. The DES collaboration has built and will employ a new, 570-megapixel, digital camera on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory in Chile to carry out a deep, wide-area sky survey of 300 million galaxies and a narrower, time-domain survey that will discover 4000 supernovae over 525 nights starting in late 2012. I will overview the DES project, which achieved`first light' in September 2012, describe results from commissioning and science verification of the instrument, and discuss the plans and goals of the survey.
12/3/12 Eric Siggia Rockefeller University Ling
  "Geometry and Genetics"
Developmental genetics has been very successful in attaching a function to thousands of genes whose mutation can lead to developmental defects. This makes the task of quantitative modeling effectively impossible. We have instead used geometric methods from dynamical systems theory plus genetics to posit simple models of phenotype that collapse the activity of many genes onto a few parameters.
2/11/13 John D. Monnier University of Michigan Tucker
  "Imaging the Surfaces of Stars"
Under even the best atmospheric conditions, telescope diffraction fundamentally limits the angular resolution for astronomical imaging. Using interferometry, we can coherently combine light from widely-separated telescopes to overcome the single-telescope diffraction limit to boost our imaging resolution by orders of magnitude. I will review recent technical and scientific breakthroughs made possible by the Michigan Infrared Combiner of the CHARA Array on Mt. Wilson, CA, with baselines of 330 meters allowing near-infrared imaging with sub-milli-arcsecond resolution. I will present the first resolved images of main sequence stars besides the Sun, focusing on the oblate and gravity-darkened photospheres of rapidly rotating stars.  We can now also resolve the interacting components of close binary stars for the first time and I will highlight the recent remarkable eclipse of epsilon Aurigae as viewed by CHARA.   
2/25/13 Scott Ransom NRAO Dell'Antonio
  "Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars"
The first millisecond pulsar was discovered in 1982. Since that time their use as highly-accurate celestial clocks has improved continually, so that they are now regularly used to measure a variety of general relativistic effects and probe a variety of topics in basic physics, such as the equation of state of matter at supra-nuclear densities. One of their most exciting uses though, is the current North American (NANOGrav) and international (the International Pulsar Timing Array) efforts to directly detect nanohertz frequency gravitational waves, most likely originating from the ensemble of supermassive black hole binaries scattered throughout the universe. In this talk I’ll describe how we are using an ensemble of pulsars to try to make such a measurement, how we could make a detection within the next 5-10 years, and how we get a wide variety of very interesting secondary science from the pulsars in the meantime.
3/4/13 Rajan Gupta Los Alamos National Laboratory Guralnik
  "India's Energy [In]Security, China's Growing Consumption, Spain's Options"
Energy security, economic development and climate security are three urgent, pressing and interconnected goals.  This talk will examine how different regions of the world aim to meet their energy needs, and sustain development. This presentation will then focus on three major regions, China, India and Europe (using Spain as an example) to illustrate challenges and opportunities. Finally, it will end with some philosophical thoughts on climate change and sustainable development.
3/11/13 Mehran Kardar MIT Valles
  "Levitation by Casimir Forces In and Out of Equilibrium"
A generalization of Earnshaw's theorem constrains the possibility of levitation by Casimir forces in equilibrium. The scattering formalism, which forms the basis of this proof, can be used to study fluctuation-induced forces for different materials, diverse geometries, both in and out of equilibrium. In the off-equilibrium context, I shall discuss non-classical heat transfer, and some manifestations of the dynamical Casimir effect.
3/18/13 Harry Themann Brookhaven National Laboratory Gaitskell
  "Observation of Electron-antineutrino Disappearance at Daya Bay Nuclear Reactor Neutrino Experiment"
At the Daya Bay Reactor Neutrino Experiment we have measured the last unknown neutrino mixing angle, θ13, to be non-zero at the 6.2σ level, this is the most precise measurement to date. This was done using a careful optimization of the detector systems, the measurement technique and choice of experimental site.  I will give a short introduction to neutrinos, what we know about them and how we know these things. I will then talk of the mathematical formalism of neutrino mixing and how we might measure the parameters of mixing.  At Daya Bay we use the technique of far/near relative measurement to make a significant reduction of the systematic errors that have been a problem for previous measurements. I will describe this technique and how this drove the design of the hardware of our experiment.  Lastly I will describe the backgrounds to our measurement and how they are dealt with and then, of course, the final result.  If there is time I hope to discuss the implication of our measurement and what’s in store for neutrino physics.
4/1/13 Lia Krusin-Elbaum City College of New York Mitrovic
  “Searching for topological superconductivity of disordered Dirac fermions”
 In the last few years there has been an explosive development in materials’ science – the discovery of a new class of insulators in three dimensions (3D) having a fully insulating electronic gap in the bulk but with metallic Dirac states on their surfaces which can carry spin/charge currents that are topologically protected against (time-reversal-invariant) disorder and perturbations. This discovery launched the search for a topological superconducting analogue characterized by a fully gapped odd parity (p-wave) pairing state that could support Majorana bound states. Such a superconducting phase has important implications for a fault-tolerant quantum computing owing to the non-Abelian exchange statistics obeyed by Majorana fermions. Recently, superconductivity below ~4 K was reported in two 2nd generation 3D topological insulators (TIs): in Bi2Se3 doped with copper and in Bi2Te3 under ~6 GPa pressure. In both cases, however, the topological nature of the superconducting phase has not yet been proved. In my talk I will discuss our most recent results on another 2nd generation TI, Sb2Te3, where we have discovered superconductivity with Tc = 8.3 K, the highest transition temperature among the TIs reported thus far.  This state is obtained when the material is synthesized under modest pressure (in the MPa range) in the narrow dome-like pressure range, reminiscent of quantum criticality in other exotic superconductors. The diamagnetic state of this new superconductor is very unusual, since even in the normal state the system supports large orbital currents, while robust van Vleck-like spin response of the disordered Dirac fermions still persists in the superconducting state. We will discuss our observations in the context of recent ideas of how arbitrarily weak disorder can assist fluctuation superconductivity and turn Dirac semimetal into a superconductor.
4/8/13 Gunther Roland MIT Heintz
  "Trillion Degree Matter"
In this talk I will discuss a very simple question: What are the properties of matter at extremely high temperature, in excess of several trillion Kelvin? Experiments at large particle colliders like RHIC at Brookhaven Lab and LHC at CERN have shown that such temperatures can be achieved in collisions of heavy nuclei, creating a plasma of quarks and gluons resembling the universe shortly after the Big Bang. We have found that the produced state of matter exhibits fascinating and somewhat surprising properties: Although its density exceeds that of water by 16 orders of magnitude, the quark-gluon plasma behaves like a near-perfect liquid.  I will review the most striking observations made in recent LHC data and discuss the unexpected connections to strongly coupled systems in other areas of physics, ranging from string theory to ultra-cold atoms.
4/22/13 Lord Martin Rees University of Cambridge Gaitskell
  Arthur O. Williams Lecture:  “From Mars to the Multiverse” (video)
Astronomers have made astonishing progress in probing our cosmic environment. We can trace cosmic history from some mysterious 'beginning' nearly 14 billion years ago, and understand in outline the emergence of atoms, galaxies, stars and planets.
Unmanned spacecraft have visited the other planets of our Solar System (and some of their moons), beaming back pictures of varied and distinctive worlds. An exciting development in the last decade has been the realization that many other stars are orbited by retinues of planets -- some resembling our Earth.
Looking further afield, we are understanding galaxies and their nuclei in fuller detail, and can check models of their evolution by detecting objects all the way back to an epoch only a billion years after the 'big bang'.  Indeed we can trace pre-galactic history with some confidence back to a nanosecond after the 'big bang'.
But the key parameters of our expanding universe -- the expansion rate, the geometry and the content -- were established far earlier still, when the physics is still conjectural but can be pinned down by future observations. These advances pose new questions: What does the long-range future hold? Should we be surprised that the physical laws permitted the emergence of complexity? and Is physical reality even more extensive than the domain that our telescopes can probe? This illustrated lecture will attempt to address such issues.