The dynamics of bodies on eccentric orbits largely determines the evolution of planetary systems and stars near massive black holes. In this talk I will review eccentric dynamics and demonstrate wide-ranging implications  such as the orbital clustering of Kuiper Belt objects in the outer solar system (which motivates the planet nine hypothesis),  `double’ galactic nuclei, and the tidal disruptions of stars by massive black holes. 

For decades, jets have served as the tool of choice at colliders around the world. They have been used to search for new particles and to probe the inner workings of Quantum Chromodynamics. The jet community continues to innovate and thrive, responding to the experimental and theoretical challenges posed by the TeV scale beam energies at the Large Hadron Collider and the extreme backgrounds produced in the quark gluon plasma. Similarly, the advent of polarized proton beams at the Relativistic Heavy Ion Collider (RHIC)  at the turn of the century motivated the adaptation of jet reconstruction techniques for spin dependent measurements. Close collaboration between theory and experiment has produced a wealth of new data on spin topics ranging from the gluon helicity distribution to novel new probes of transverse momentum distributions. An overview of recent RHIC jet results, as well as new techniques developed for spin measurements will be presented.  The implications for further measurements at RHIC and at a future Electron-Ion-Collider will be discussed

Host : Brad Plaster

Neutrinos exist but we don’t know some of their most basic properties.  Dark matter exists but we don’t know what it is.  New experiments are being devised to solve these mysteries.  Theory is important to guide searches in the most promising directions and to enable precision measurements that are critical to next generation discovery potential.  I discuss theoretical tools to address the “neutrino interaction problem” for long baseline neutrino experiments, and mention related applications to precision measurements with muons.  I describe recent theoretical developments that tightly constrain the possible interactions of dark matter particles with nuclei in underground detectors

Host: Susan Gardner

How to modify Kelvin's theory (1887) of the ship wake to describe the effect of an obstacle on a current sheet in a two-dimensional conductor.

Host: Ganpathy Murthy

While nuclear structure is dominated by the strong interaction, life as we

experience it happens at the electromagnetic scale of hierarchy.  I discuss

my own electromagnetic wanderings in experiments to characterize the effects

of the weak interaction on hadronic structure, nuclear deacy, and static

electromagnetic moments, and possibly discover new physics at higher energy

scales.

Host: Brad Plaster

In quantum field theory, massless fermions must segregate into left- and right-handed populations that do not ever mix. Chiral symmetry (handedness) is a protected global symmetry. However, coupling of the fermion fields to a vector gauge field ruins the symmetry. The resulting axial current that flows is known as the chiral anomaly. The first example appeared in the theory of the ultrafast decay of neutral pions into photons (Adler Bell Jackiw anomaly). In the ensuing 5 decades, anomalies have appeared at every energy scale, from QCD to gravitation physics. In 1983, Nielsen and Ninomiya predicted that the chiral anomaly should be observable as well in bulk semimetals that feature protected 3D Dirac cones. The axial current appears as an enhanced conductance in parallel electric and magnetic fields. I will describe experiments on Na3Bi and GdPtBi which show the dramatic emergence of the anomaly when carriers are confined to the lowest Landau level. Tests to distinguish this quantum effect from (classical) artifacts caused by “current jetting” will be described.

Host: Joe Brill

The deep gravitational potential wells of clusters of galaxies should capture fair samples of the total baryon fraction of the Universe, unless other physical processes drive baryons out of clusters. Thus precision measurements of the baryon fraction, particularly as a function of cluster mass, can reveal the history of baryon flux into and out of clusters. How those baryons are then apportioned between stars and intracluster gas---the star formation efficiency---informs models of cluster assembly and massive galaxy evolution, as well as efforts to use the cluster gas fraction to constrain the mass density and dark energy equation of state parameters. Even the partitioning of the stellar baryons alone, in and out of galaxies, tests models of cluster galaxy evolution, as intracluster stars are the final, unambiguous signature of stars stripped from cluster galaxies during tidal encounters. We have discovered that intracluster stars are a significant part of the stellar baryons in clusters and poorer groups of galaxies. I will present new work characterizing the properties of this previously unexplored component, as well as the consequences for the cluster baryon budget and its relationship to the Universal value.

Ironically, our understanding of dark matter is hampered in large part by the presence of baryonic matter. The measured mass profile of pristine dark matter halos would provide clear indications of whether the dark matter is truly cold or warm or interacting. Finding such halos has, in part, motivated the search for the lowest mass galaxies because these are the most dark matter dominated systems known. I will describe a new way to find even lower mass halos than those identified so far, as well as a new class of massive galaxy that may provide massive analogs of nearly pure dark matter halos.