Events

It is well known that the dimension of conserved currents is determined simply from dimensional analysis. However, a recent proposal is that what is strange about the conserved currents in the strange metal in the cuprate superconductors is that they carry anomalous dimensions. The basic model invoked to exhibit such behaviour is a holographic dilatonic one in which the field strength couples to the radial coordinate. I will show that the anomalous dimension in such cases arises from a fractional electromagnetism that can be thought of as a general loop-hole in Noether's second theorem.

Our characterization of cancer is advancing rapidly through the ever-increasing ability to make quantitative measurements of the cancerous tissues with new tools and technologies.

In a recent paper, the MIT group led Pablo Jarillo-Herrero has found that doping twisted bi-layer graphene can generate strongly correlated insulating states and superconductivity at particular twist angles called magic angles.  

This problem has excited the condensed matter community because it establishes that graphene, normally viewed as a weakly  interacting system, is a new platform for strongly correlated physics.   

Physics 301 has been flagged as a challenging course in the department for a myraid of reasons.  First, this is one of the first “advanced” physics courses.  While the content is largely familiar, students must integrate ideas from previous physics and math courses and utilize a coordinated set of tools when solving problems.  Secondly, the class is comprised of 160-180 students from a variety of programs, with variations in prerequisite courses and incoming abilities.  This talk will cover how we’ve utilized the active learning theater (Henn200) to promote collaboration

We show that when the bare cosmological constant in the Einstein field equations takes large negative values, the average distance between any two nearby geodesics moving in the spacetime sourced by quantum fields vacuum would gradually increase at a slow accelerating rate due to the weak parametric resonance effect caused by the fluctuations of the quantum vacuum energy density.

ABSTRACT: The study of brown dwarfs with effective temperatures less than 500 K can offer important insights into the complex physics of ultracool atmospheres, the shape of the initial mass function, and the low-mass limit of star formation. We have been using the Wide-field Infrared Survey Explorer (WISE) to search for just such a population of brown dwarfs and have identified roughly twenty cool browns dwarfs that populate a new spectral class, dubbed 'Y'.

My research program is motivated by fascination with bird flight. My laboratory group uses a multi- disciplinary approach that includes biomechanics, physiology, and neuroscience to examine flight ability. Our current research is organized around two topics: 1) how birds morph their wings and what benefits this provides; and 2) how optic flow signals are encoded in the avian brain and used to guide their flight. As we gain understanding of flight mechanisms, we further endeavor to apply comparative approaches that provide deeper insight into avian ecology and evolution.

Topological insulators are electronic systems with an insulating bulk and topologically protected boundary states. Conventional 2D topological insulators induce 1D edge states. Recent studies indicate that lower-dimensional topological states are also possible in electronic systems through higher-order topology, which, however, has been confirmed only in Bismuth in experiments [1]. In this talk, I will show that lower-dimensional topological wave trapping can be achieved in photonic and acoustic systems through several different mechanisms.

Please join us before the Colloquium in Hennings 318 for coffee, tea and snacks at 2:45 pm

The advent of space-based telescopes that provide high-precision time-series photometry, such as CoRoT and Kepler/K2, have revealed a zoo of stellar variability on timescales from minutes to months. In this talk, I will focus on classes of objects whose light curves show distinctive "dips" that can tell us a surprising amount about planet formation, evolution, and death. These include disintegrating planets, young dipper systems, likely exocomets, and unlikely alien megastructures.

The non-zero mass of neutrinos suppresses the growth of cosmic structure on small scales. Since the level of suppression depends on the sum of the masses of the three active neutrino species, the evolution of large-scale structure is a promising tool to constrain the total mass of neutrinos and possibly shed light on the mass hierarchy. I will discuss recent progress and future prospects to constrain the neutrino mass sum with cosmology.

Thesis Abstract:
In this thesis, I investigate the behavior of particles dressed by quantum field excitations and random interactions.

Superconductivity is more than 100 years old, and the established theory of conventional superconductors is more than half as old. But how established is it, and how conventional are the 'old' superconductors? This talk will provide a brief summary of the “state-of-the-art” of superconductivity, and discuss one aspect of pairing that has received some attention lately — “kinetic-energy-induced” pairing. A parable that describes the chemistry of the Helium atom will be used to explain this idea, and how this concept ties in to possible experimental signatures.

It is common to think of strains in solids in a somewhat passive sense, simply as the response of a material to external forces. However, for certain types of electronic order, strains of a specific symmetry can have much more important roles to play, acting as longitudinal, and even transverse, fields for the order parameter. In this talk, I will first describe how antisymmetric strain can act as a longitudinal field for electronic nematic order. I'll then go on to describe appropriate transverse fields for nematic order, including orthogonal antisymmetric

The effort to design and build quantum computers in the laboratory is now a billion dollar enterprise. But might we, ourselves, be quantum computers? Most scientists think that in the warm wet brain, this is highly unlikely; and certainly it would be at variance with what the medical profession believes. My strategy is one of reverse engineering, seeking to identify the biochemical substrate and mechanisms that could host such putative quantum processing.

Using the background-field method we demonstrate the Becchi-Rouet-Stora-Tyutin (BRST) structure of counterterms in a broad class of gauge theories. Put simply, we show that gauge invariance is preserved by renormalization in local gauge field theories whenever they admit a sensible background-field formulation and anomaly-free path integral measure. This class encompasses Yang--Mills theories and relativistic gravity, including both renormalizable and non-renormalizable (effective) theories.

The physics of soft materials is distinct from hard matter, as the weaker intermolecular bonds can result in a large response to external stresses. In recent years, there has been a significant interest in understanding the interaction between a liquid’s surface tension and a solid’s elasticity: elastocapillarity. In particular, liquids can generate significant deformations of highly compliant materials.

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.

Every night, telescopes around the world obtain a flood of new data as parts of deep and wide surveys. This amount of data will steeply rise once upcoming sureys such as the Large Synoptic Survey Telescope (LSST), which will image the entire visible sky every few nights, start their operation. To investigate this huge amount of data, machine-learning algorithms are absolutely necessary for image analysis, classification of sources, time-series analysis and also structure finding.

The fact that neutrinos have mass and change flavors means that we can learn a great deal about them by studying what are effectively interference patterns that arise after neutrinos propagate over hundreds of kilometers. The DUNE experiment will measure these interference patterns over a broad neutrino energy range after neutrinos have propagated 1300km. In addition, DUNE will use a detector technology that provides exquisite detail about the interactions that make up the interference pattern.

I investigate the dynamics of multi-state central systems coupled bilinearly to an external oscillator bath within the noninteracting-blip approximation. I focus on both a 3-site configuration, as well as a 2-site model for the central systems of interest.

Physicists have been exploring techniques for the controlled manipulation of large collections of quantum objects.  A valuable strategy has been placing collections of laser-cooled atoms in optical cavities.  I will review the state of the field, some of the underlying physics, and the outlook.