Spectroscopic investigations are essential to understand intriguing phenomena in many areas of physics.  In particular, recent advanced spectroscopic tools such as resonant inelastic x-ray scattering and photoemission spectroscopy play an important role in condensed matter physics.  While research on thin-films or superlattices is expected to reveal hidden novel physical properties, previous inelastic spectroscopic investigations have been unable to detect these properties due to the small cross-section.

In this colloquium, I will discuss advanced inelastic light scattering (Raman spectroscopic) studies of two-magnon dynamics in Sr₂IrO₄ thin-films as functions of strain and temperature.  Recent experimental studies of Sr₂IrO₄ thin-films have contradicted the widely-accepted Glazer description of octahedral tilting and rotation in perovskite oxides.  However, our experimental observations and density functional theory calculations show that the multi-orbital nature of the J_eff = ½ state is crucial to understanding the magnetic and electronic properties of 5d transition-metal oxides.  This study demonstrates how advanced spectroscopic tools improve our fundamental understanding of strongly correlated, spin-orbit coupled electrons, enabling us to explore the novel phase diagrams of these systems.

Dualities are a powerful concept in quantum field theory, helping us to identify the correct low energy degrees of freedom. In this talk several old and many new dualities in 2+1 dimensions will be shown to all follow from one conjectural base pair, with potential applications to the physics of the quantum Hall effect.  

Host: Sumit Das

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