Past Events

Astro Seminar: "Dark Matter Clustering in the Dissipationless Limit"
March 28, 2018  2:00 pm
David Rittenhouse Laboratory, A4
Michael Joyce (Sorbonne Université, Paris)
An accurate description and understanding of matter clustering in the strongly nonlinear 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 socalled "stable clustering" approximation a relevant one? (3) Are there really "universal" properties of nonlinear clustering?

HET & HEE Joint Seminar: "Cosmological Bounces and Wormholes from Vorticity"
March 27, 2018  1:30 pm
David Rittenhouse Laboratory, 4N12
David Kaplan (John Hopkins University)

High Energy Theory Seminar: (TBA)
March 26, 2018  2:00 pm
David Rittenhouse Laboratory, 2N36
Ted Jacobson (U of Maryland)

Workshop on Imaging Biomarkers
March 23, 2018  9:00 am  4:00 pm
Biomedical Research Building (BRB) II/III Auditorium and Lobby; 421 Curie Boulevard
Welcome to the Fifth Annual CMROI Workshop on Imaging Biomarkers to be held Thursday, March 22

Condensed Matter Seminar: "Geometry and mechanics of feet and fins"
March 21, 2018  4:00 pm  5:00 pm
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 curvatureinduced 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.

High Energy Theory Seminar: "Discrete Superconformal Matter"
March 19, 2018  2:00 pm
David Rittenhouse Laboratory, 2N36
Paul Oehlmann (Virginia Tech)
We construct a novel type of (2,0) discrete charged superconformal matter coupled to 6d supergravity using Ftheory. For this, we consider smooth genusone fibered and compact CalabiYau threefolds quotiented by a freely acting automorphism. The resulting geometries exhibit orbifold singularities in the base with socalled multiple fibers over them which is where the (2,0) discrete charged matter resides. We show this presence to be necessary for anomaly cancellation which we proof in generality.

Astro Seminar: "Insights Into Dark Matter From the Stellar Halos of Galaxies"
March 16, 2018  1:00 pm  2:00 pm
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.

32nd Primakoff Lecture: "Metamaterials and Topological Mechanics"
March 14, 2018  4:00 pm
David Rittenhouse Laboratory, A8
Tom Lubensky (University of Pennsylvania)
Metamaterials are materials engineered to have a property or properties not found in nature, such as a negative optical index of refraction, oneway light or vibration waves, or exotic elastic behavior. Advances in materials processing, like 3D printing and laser cutting, over the last 10 to 15 years have made it possible to fabricate metamaterials with madetoorder structure at length scales as short as a micron.

Astro Seminar: "The Chaotic Life Cycles of Planetary Systems"
March 14, 2018  2:00 pm
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"
March 13, 2018  1:30 pm
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 realworld 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.