Past Events

High Energy Seminar: "Large N Tensor Models"
April 10, 2017  2:00 pm
David Rittenhouse Laboratory, 2N36
Igor Klebanov (Princeton University)
We review the double line notation for the Feynman diagram expansion of N by N matrix models. In the ‘t Hooft large N limit only the planar diagrams survive, and the dual graphs may be thought of as discretized random surfaces. We proceed to theories where the dynamical degrees of freedom are rank3 tensors with distinguishable indices, each of which takes N values. Their Feynman diagrams may be drawn using colored triple lines (red, blue, green), while the dual graphs are made out of tetrahedra glued along their triangular faces.

Diversity and Inclusion in Physics :"Women in Physics: Understanding and Overcoming Biases and Barriers"
April 7, 2017  4:00 pm
David Rittenhouse Laboratory, A4
Amy Graves (Swathmore)
Physics is phenomenally successful at taking data on sexless, raceless objects and transforming that information into mathematical laws with highly accurate predictive power. Why, therefore, should gender be an issue among physicists – so that there is a paucity of women in physics, at all professional levels and in virtually all nations? It is a tenet of gender studies that one should avoid attributing complicated effects to a single cause. (Gender studies is a field guaranteed to annoy the physicist.

Condensed Matter Seminar: "Metal chalcogenide semiconductors: Synthesis, electronic structure, lightmatter interactions"
April 5, 2017  4:00 pm  5:00 pm
David Rittenhouse Laboratory, A4
Peter Sutter, University of Nebraska
Metal chalcogenides have received attention as twodimensional (2D) materials beyond graphene. Semiconducting chalcogenides are particularly attractive since they exhibit novel physics such as strongly bound excitons and valley polarization, and may enable nextgeneration electronics benefiting from confinement, high carrier mobility, flexibility and bendability. While transition metal dichalcogenides (particularly MoS2) have been investigated as prototype systems, other materials, especially those incorporating normal metals or metalloids, remain much less studied.

Astro Seminar: "Investigation of Keplerlike Laws of Galactic Dynamics In Dispersionsupported Spherical Galaxies and Test of Dark Matter and Modified Gravity Theories"
April 5, 2017  2:00 pm
David Rittenhouse Laboratory, A4
KyuHyun Chae (Sejong University)
Whether dynamical systems such as galaxies, galaxy clusters and the universe itself are controlled by Einstein’s theory of gravity in conjunction with yettobeidentified dark matter/energy or alternatively by modified gravity is an outstanding current problem of astrophysics and fundamental physics.

High Energy Seminar: "Black Holes in Massive Gravity: TimeDependent Solutions"
April 5, 2017  12:00 pm  1:00 pm
DRL 2N36
Rachel A. Rosen (Columbia University)
When starting with a static, sphericallysymmetric ansatz, there are two types of black hole solutions in massive gravity: (i) exact Schwarzschild solutions which exhibit no Yukawa suppression at large distances and (ii) solutions which contain coordinateinvariant singularities at the horizon. In this talk, I will present new black hole solutions which have a nonsingular horizon and can potentially be matched to Yukawa asymptotics at large distances. These solutions recover Schwarzschild black holes in the limit of zero graviton mass and are thus observationally viable.

MathBio seminar: " The mathematical foundation of a landscape theory for living matters and life"
April 3, 2017  4:00 pm  5:00 pm
Carolyn Lynch Laboratory, 318
Hong Qian (University of Washington)
The physicists' notion of energy is derived from Newtonian mechanics. The theory of thermodynamics is developed based on that notion, and the realization of mechanical energy dissipation in terms of heat. Since the work of L. Boltzmann, who trusted that atoms were real as early as in 1884, the heat became intimately related to the stochastic motion of the invisible atoms and molecules.

High Energy Seminar: "Modular spacetime and Metastring theory"
April 3, 2017  2:00 pm  3:00 pm
DRL 2N36
Djordje Minic (Virginia Tech)
In this talk we review our recent work on metastring theory and its habitat, a new form of quantum spacetime, called modular spacetime. We emphasize that the geometry underlying modular spacetime, i.e. the background geometry ofmetastring theory, is also the geometry underlying generic representations of quantum theory as formulated in terms of Aharonov's modular variables. Thus the metastring sheds light on the foundations of quantum theory, andit represents a new formulation of string theory and quantum gravity based on the principle of relative locality. 
Condensed Matter Seminar: "Atomic Crystals with New Twists"
March 29, 2017  4:00 pm  5:00 pm
David Rittenhouse Laboratory, A4
Jiwoong Park, Cornell University
Chiral materials possess left and righthanded counterparts linked by mirror symmetry, with applications in physics, chemistry and biology. In atomic crystals such as graphene, chiral symmetry emerges naturally as a consequence of the honeycomb lattice. In this talk, I will discuss two recent studies where the interaction between graphene and another surface breaks this chiral symmetry. The first example is chiral twisted bilayer graphene, a twoatomthick chiral film, with giant circular dicrhoism.

Astro Seminar: "LargeScale Structure Tests of Galaxy Formation and Modified Gravity"
March 29, 2017  2:00 pm  3:00 pm
David Rittenhouse Laboratory, A4
Ying Zu (Ohio State University).
I will present novel tests of galaxy formation theories and the nature of gravity, using largescale structure measurements from the Sloan Digital Sky Survey (SDSS). I will first introduce the iHOD model, a probabilistic framework for mapping galaxy properties to their underlying dark matter halos. By modelling the color dependence of galaxy clustering and weak gravitational lensing, iHOD reveals a surprisingly simple picture for "galaxy quenching", i.e., the cessation of starformation activities within galaxies.

*Special* High Energy Seminar: "Monopoleantimonopole Creation and Other Numerical Studies"
March 28, 2017  11:00 am
DRL 4N12
Tanmay Vachaspati (Arizona State University)
I will describe magnetic monopoles, their properties, and recent numerical work on their creation from particles.