Past Events

  • Condensed Matter Seminar: "Formation of a hexagonal limit-periodic structure"

    David Rittenhouse Laboratory, A4

    Josh Socolar, Duke University

    A limit-periodic structure consists of a union of periodic patterns with no largest lattice constant.  The discovery of an aperiodic monotile -- a single tile that forces hexagonal limit-periodic pattern in the same way that the two Penrose tiles force a quasicrystalline pattern -- has opened a new path to the theory of formation of a limit-periodic phase and to its possible physical realization.  A renormalization analysis shows that the limit-periodic ground state can be reached in a slow quench through an infinite sequence of phase transitions, and numerical studies indi

  • Astro Seminar: "The Relationship Between Quasar Activity and Diffuse Cool Halo Gas -- Feeding or Feedback?"

    David Rittenhouse Laboratory, A4

    Sean Johnson (Princeton/Carnegie)

    The growth and evolution of galaxies is fueled by gas accretion from circum-/intergalactic gas reservoirs. In turn, gas accretion and cooling is regulated by outflows and heating from supernovae and active galactic nuclei. These outflows enrich the intergalactic medium with heavy elements and produce massive baryon reservoirs in the form of diffuse halo gas. Consequently, the diffuse gas of the inter- and circum-galactic medium (IGM/CGM) represent a sensitive laboratory for studying the accretion and feedback processes that regulate galaxy evolution.

  • Eli Burstein Lecture: "Confinement & Tunneling, Pillars of Nanoscience"

    Glandt Forum (3rd Floor), Singh Center for Nanotechnology, 3205 Walnut Street

    Emilio Mendez: Director of Energy Science and Technology, Brookhaven National Laboratory and Professor of Physics, Stony Brook University

    The properties of materials are in general determined by chemical composition and structure, but at the nanoscale they depend on size as well. As one or more dimensions of a material become increasingly smaller, not only can it inhabit ever smaller spaces; also its surface to volume ratio increases, and at a small enough size (typically well below 100 nm) a number of the material’s properties become governed by quantum mechanics.

  • Math-Bio seminar: "Phenotypic plasticity promotes balanced polymorphism and recombination modification in periodic environments"

    318 Carolyn Lynch Laboratory

    Davorka Gulisija, University of Pennsylvania

    Phenotypic plasticity is known to arise in varying habitats where it diminishes harmful environmental effects. How plasticity shapes genetic architecture of traits under varying selection is unknown. Using an analytic approximation and Monte Carlo simulations, we show that balanced polymorphism and recombination modification arise simultaneously as a consequence of epistatic plastic modification in periodic environments.

  • Special Condensed Matter Seminar: "Nano-electrodynamics with graphene plasmons"

    David Rittenhouse Laboratory, A4

    Mark Lundeberg, Institute of Photonic Sciences (Castelldefels, Spain).

    I will review my recent work on plasmons in graphene, a naturally appropriate material for studying electron motion at terahertz and mid-infrared frequencies. Graphene plasmons are extremely confined propagating waves (with wavelengths 100 times smaller than light) which have lifetimes up to 500 fs at room temperature, and which can be probed by near field microscopy. Various aspects of these plasmons will be discussed: in-situ tuning and guiding with gate voltages, electrical detection of plasmons, and tuning by the dielectric environment around the graphene.

  • Department Colloquium: "Results from the New Horizons Flyby of Pluto"

    David Rittenhouse Laboratory, A8

    Marc Buie (Southwest Research Institute) hosted by Mariangela Bernardi

    July 2015 saw the culmination of decades of work to get a detailed look at a distant and intriguing world.  As of late 2016, the transmission of all data from the encounter was completed and the project is now turning its attention to the upcoming extended mission flyby of 2014MU69 on 2019 Jan 1.  The encounter was crucial for pinning down seemingly simple quantities such as size and albedo but opened the door to much more in-depth studies of the origin and evolution of Pluto and its constraints on the history of our solar system.

  • Math-Bio seminar: "A flexible inference of complex population histories and recombination from multiple genomes"

    318 Carolyn Lynch Laboratory

    Champak Reddy, CUNY Graduate Center

    Analyzing whole genome sequences provides an unprecedented resolution of the historical demography of populations. In the process, most inferential methods either ignore or simplify the confounding effects of recombination and population history on the observed polymorphism. Going further, we build upon an existing analytic approach that partitions the genome into blocks of equal (and arbitrary) size and summarizes the polymorphism and linkage information as blockwise counts of SFS types (bSFS).

  • Special Condensed Matter Seminar: "Manipulating Charge Carriers for Quantum Transport in Van der Waals Materials Nanostructures"

    David Rittenhouse Laboratory, A4

    Ke Wang, Harvard University

    Since the discovery of graphene via mechanical exfoliation, it has been shown that the electronic properties of solids can undergo dramatic change when the material thickness is reduced to the atomic limit. Recently, the quality of these 2-dimensional (2D) electronic systems has been significantly improved by hexagonal boron nitrides encapsulation, enabling the electron mean free path only limited by the size of the samples. However, mesoscopic transport studies in these systems are relatively unexplored due to the challenges in the device fabrication processes.

  • Special Condensed Matter Seminar: "A Berry Phase Switch in Circular Graphene Resonators"

    David Rittenhouse Laboratory, A4

    Fereshte Ghahari Kermani, National Institute of Standards and Technology

    Berry phase is an example of anholonomy, where the phase of a quantum state may not return to its original value after its parameters cycle around a closed path; instead the quantum system’s wave function may acquire a real, measurable phase difference, known as Berry phase. Berry phase is connected with the geometry of the quantum system having intriguing physical consequences in systems with topological singularities, such as graphene.

  • Astro Seminar: "Massive Neutrinos and Large-scale Structure: Forecasts for SKA"

    David Rittenhouse Laboratory, A4

    Francisco Villaescusa-Navarro (Simons CCA)

    In the first part of the seminar I will discuss some of the effects that massive neutrinos induce on the large-scale structure of the Universe, from their impact on the clustering of halos, galaxies and voids to their signatures on the BAO. In the second part of the seminar I will discuss the possibility of using the hydrogen 21cm line to study cosmology.