Recent developments in the study of quantum gravity have revealed a surprising and beautiful connection between quantum entanglement and the geometry of spacetime. This discovery offers a new perspective on old puzzles concerning black holes, and may lead to a profoundly new way of thinking about the emergence of spacetime from fundamental quantum-mechanical building blocks. I will describe these developments, explaining along the way the necessary background in quantum gravity and quantum information theory.

Host: Pranjal Nayak

In science, new advances and insights often emerge from the confluence of different ideas coming from what appeared to be disconnected research areas. The theme of my colloquium will review an ongoing collision between the three topics listed in my title which has been generating interesting new insights about the nature of quantum gravity, as well as variety of other fields, eg, condensed matter physics and quantum field theory.

In addition to carrying a quantized electrical charge, electrons also possess a quantized angular momentum, or spin.  In ordinary charge-based electronics, the spins are usually randomly oriented and they do not play a role in device function.  However, in the last ten years there have been significant advances in understanding how to control electron spins in useful ways.  Spin currents can now be used, for example, to apply torques within magnetic memory devices that are more than 1000 times stronger than charge-current-generated magnetic fields.  I will discuss some of this progress, with an emphasis on recent discoveries that magnetic devices can be manipulated with record-breaking efficiencies using strong spin-orbit coupling in heavy metals and topological insulators.

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 imminent advent of 30-m class telescopes and Stage-4 cosmic microwave background observatories promises to give us precision measurements of key parameters which are set in the very early universe. For example, we may soon know to fair precision the amount of relic relativistic energy and the deuterium and helium abundances set during the time when the neutrinos fall out of thermal and chemical equilibrium. Given the excitement and ferment right now surrounding new ideas in dark matter, dark sector, and other beyond standard model (BSM) physics, we would very much like to leverage these coming measurements into deeper insights into this epoch, in effect turning the early universe into a precision BSM physics laboratory. Doing so, however, requires theorists to "raise their game” in modeling the neutrino decoupling epoch. We will discuss these issues and reveal some surprising features of the universe when it was roughly one second in age.

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. 

Host: Isaac Shlosman

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

The pyrochlore lattice, a network of corner-sharing tetrahedra, is one of the most pervasive crystalline architectures in nature that supports geometrical frustration.  We and others have been interested in a family of rare earth pyrochlore magnets, that can display quantum S=1/2 magnetism on such a lattice.  The ground states for these materials may be described by a model known as "spin ice", a model with the same frustration and degeneracy as solid ice (the kind you skate on), as well as by a quantum version of this model known as "quantum spin ice" that possesses an emergent quantum electrodynamics.  I'll describe how this comes about and how we can understand these materials, with an emphasis on modern neutron scattering.  I'll also briefly discuss how fragile some of these quantum ground states seem to be with respect to weak quenched disorder, which is hard to avoid in real materials.

Host: Ribhu Kaul

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