Past Events

  • Condensed Matter Seminar: "Wisdom of hives and mounds: collective problem solving by super-organisms"

    David Rittenhouse Laboratory, A4

    Lakshminarayanan Mahadevan (Harvard University)

    Social insects are capable of solving complex physiological problems using collective strategies. I will discuss our work on some of these problems  that include the physiology and morphogenesis of termite mounds, and  active mechanisms for ventilation, mechanical adaptation and  thermoregulation  in bee aggregates.

  • Astro Seminar: (TBA)

    David Rittenhouse Laboratory, A4


  • Condensed Matter Seminar: "Ideas on magma motion within the lithosphere: percolation, channelization, and stress-driven segregation"

    David Rittenhouse Laboratory, A4

    Mousumi Roy (University of New Mexico)

    Although we know that magma is generated by partial melting of rocks at depth, we have less of an understanding of the processes that transport magma from great depths (>100-150 km) into the shallower (20-0 km) crustal plumbing systems of volcanic zones.   I shall discuss how interstitial melt migrates via percolative flow, and ideas on how it eventually becomes focused and reorganized into networks.  Field and geochemical observations suggest that these networks are characterized by thermal and chemical disequilibrium between the magma and surrounding rock.  I

  • Astro Seminar: "Dark Matter Clustering in the Dissipationless Limit"

    David Rittenhouse Laboratory, A4

    Michael Joyce (Sorbonne Université, Paris)

    An accurate description and understanding of matter clustering in the strongly non-linear regime, even neglecting baryonic physics, remains a problem which is relevant to cosmology and of fundamental interest. My talk will be structured around three questions about it: (1) How well do current simulations resolve this clustering? (2) Is the so-called "stable clustering" approximation a relevant one? (3) Are there really "universal" properties of non-linear clustering?

  • High Energy Theory Seminar: (TBA)

    David Rittenhouse Laboratory, 2N36

    Ted Jacobson (U of Maryland)

  • Condensed Matter Seminar: "Geometry and mechanics of feet and fins"

    David Rittenhouse Laboratory, A4

    Mahesh M. Bandi (Okinawa Institute of Science and Technology Graduate University)

    The stiffness of propulsive appendages, such as feet and fins, is important in locomotory function. In this talk, I show that curvature-induced stiffness is the common principle underlying the stiffness of both primate feet and rayed fish fins. We use mathematical models, physical models, and biological experiments to arrive at this conclusion. The principle is evident in a drooping dollar bill that significantly stiffens upon slightly curling it in the transverse direction.

  • Astro Seminar: "Insights Into Dark Matter From the Stellar Halos of Galaxies"

    David Rittenhouse Laboratory, A2

    Robyn Sanderson (Caltech)

    Cosmological simulations can now make specific and detailed predictions for the shapes, masses, and substructure fractions in galactic dark matter halos that depend on the dark matter model assumed. Comparing these predictions to the observed mass distributions of galaxies should in principle lead to constraints on the nature of dark matter, but observable dynamical tracers can be scarce in regions where the dark matter distribution is best able to discriminate between models.

  • Astro Seminar: "The Chaotic Life Cycles of Planetary Systems"

    David Rittenhouse Laboratory, A4

    Daniel Tamayo (University of Toronto)

    The past two decades have seen the discovery of thousands of new planetary systems in our galactic neighborhood, many of which look drastically different from our own. However, despite this remarkable observational achievement, we are still struggling to generate theoretical frameworks capable of explaining their divergent evolutionary paths. In particular, a central challenge is modeling the often chaotic orbital evolution of planetary systems over typical lifetimes of billions of years, which sculpts the distribution of orbital architectures that we observe at the present day.

  • HET & HEE Joint Seminar: "Unification from Scattering Amplitudes"

    David Rittenhouse Laboratory, 4N12

    Cliff Cheung (Caltech)

    Scattering amplitudes are fundamental observables that encode the dynamics of interacting particles. In this talk, I describe how to systematically construct these objects without reference to a Lagrangian or an underlying spacetime. The physics of real-world particles like gravitons, gluons, and pions are thus derived from the properties of amplitudes rather than vice versa. Remarkably, the expressions gleaned from this line of attack are marvelously simple, revealing new structures long hidden in plain sight.

  • High Energy Theory Seminar: "Coarse-Graining Holographic Entanglement"

    David Rittenhouse Laboratory, 2N36

    Netta Engelhardt (Princeton)