College of Arts and Sciences

In the hunt for Majorana particles, originally proposed in the context of particle physics, recent investigations have led to exciting prospects in superconducting wires, including possible experimental detection. This colloquium will first discuss how Majorana fermions can be present in ‘topological’ superconductors. Then, the rich interplay between potential landscapes and superconductivity will be explored in this context. As one instance, it is known that lattices subject to quasiperiodic potentials can give rise to beautiful Hofstadter butterfly patterns in phase space; these patterns can form the backdrop from which regimes containing Majorana fermions emerge. As another instance, in the presence of disorder,

Continue reading… Spotting Majorana Fermions amidst Hofstadter butterflies and disordered landscapes – Smita Vishveshwara

The observation that the three types of neutrino flavor oscillate among themselves led to the realisation that neutrinos have a very small but non-zero mass. This is extremely important because the supremely successful Standard Model of particle physics had expected, and indeed needed, the neutrinos to have exactly zero mass. Since the discovery of neutrino oscillations over the last 15 years, the parameters of the oscillations have been sufficiently well measured to turn neutrino oscillations into a tool for learning more about the elusive neutrino. I will explain the concept of neutrino oscillations, and report on the recent results from around the world in context with the new challenges now facing researchers of inferring the remaining unknown neutrino properties.

Continue reading… Neutrino Oscillations at Work – Jenny Thomas

What Can We Learn about Language by Reading Millions of Books? (A Baker-Nord Digital Humanities Event) The dramatic growth of linguistic corpora enables the quantitative study of language

The dramatic growth of linguistic corpora enables the quantitative study of language on a scale that would have been unimaginable even five years ago. In this talk I will describe what we might learn about language and its evolution from such studies, using the regularization of verbs as a concrete example.

Continue reading… Physics and Language – Harsh Mathur

Supersymmetry, and other theories that go beyond the Standard Model of particle physics, often predict the existence of new particles and interactions that act as sources of time-reversal violation. These, in turn, induce asymmetries in the charge distribution of electrons. In this colloquium, I will describe the stringent constraints on such new physics that were recently imposed by precise measurements with the thorium monoxide molecule (ACME Collaboration: Science, Jan 17, 2014). I will explain how polar molecules amplify the miniscule asymmetries of an electron’s charge distribution, how these molecules provide a useful suite of tools for experimenters, and the details of how we made the measurement.

Continue reading… Constraining supersymmetry using molecules – Amar Vutha

Hybrid organic/inorganic halide perovskites such as methylammonium lead iodide, (MA)PbI3, have recently burst on the solar cell scene with record efficiencies after only a few years of development. In this colloquium I will discuss some of the unique properties of these and related inorganic materials, such as CsSnI3 and their relation to their success in solar cell applications. I will show how the key feature of their electronic band structure results in a number of unusual properties. They are excellent hole conductors, they have an anomalous dependence of the band gap on temperature, strong optical absorption and their gap can be fine tuned with chemical substitutions.

Continue reading… Halide perovskites: their unusual combination of properties and its impact on solar cell applications – Walter Lambrecht

Ultracold Neutrons (UCN) provide an excellent laboratory for precision studies of the Standard Model of particle physics, and can be used as a unique tool to probe the properties of other materials. The Ultracold Neutron facility at the Los Alamos Neutron Science Center has developed one of the brightest sources of UCN in the world. This facility is home to major experimental efforts to use UCN to determine the neutron beta decay lifetime, the angular correlations of the neutron spin with the decay proton and electron, the shape of the electron energy spectrum, and a new search for the electric dipole moment of the neutron.

Continue reading… The Standard Model and Beyond with Ultracold Neutrons – Leah Broussard

In standard (textbook) quantum mechanics, “measurement” provides an essential link between the formalism and its physical interpretation, but physical measurements cannot be analyzed in fully quantum mechanical terms (the infamous “measurement problem”). The (consistent or decoherent) histories interpretation employs fundamental quantum principles that apply universally to all quantum processes, including measurements, but make no reference to “measurement” as a fundamental concept. This approach provides a resolution of all the standard quantum enigmas (double slit, wave function collapse, etc.) as well as resolving the quantum measurement problem. The talk will provide an overview of the histories approach and indicate some of the objections to it.

Continue reading… Quantum Mechanics Without Measurements – Robert Griffiths

Some 40 years ago Hawking found a remarkable contradiction: if we accept the standard behavior of gravity in regions of low curvature, then the evolution of black holes will violate quantum mechanics. Resolving this paradox would require a basic change in our understanding of spacetime and/or quantum theory. In recent years the paradox has found an interesting resolution through string theory. While quantum gravity is normally expected to be important only at distances of order planck length, the situation changes when a large number N of particles are involved, as for instance in the situation where we make a large black hole.

Continue reading… The black hole information paradox and its resolution in string theory – Samir Mathur

Technology has been long understood to play a central role in limiting the proliferation of nuclear weapons. Over the last thirty years, however, systematic improvements in information, design, modeling, and manufacturing tools have eased that challenge. Could developing countries, or even small engineering firms, soon make nuclear weapons on their own? There is evidence that this transition has already occurred. This talk examines routes to the bomb that require only technologies already within reach of nearly any country without foreign assistance or access to export-controlled equipment or materials. It reports on a study of twenty historical nuclear programs, technical analyses,

Continue reading… Building Nuclear Bombs in Your Basement: the technology of nuclear proliferation – R. Scott Kemp

Although fewer daily papers keep reporters on the science beat, science reporting is still thriving online, from large news organizations to popular science magazines to news stories from scientific institutions. I’ll tell you about what I have observed as a reporter and de facto press officer about getting research stories into these outlets. However, the web also allows researchers and science communicators to speak directly to the public. My personal favorite method is the rap video, so you will hear about a few of those, but many researchers write blogs, discuss science on social media, or participate in online outreach events.

Continue reading… Getting research news out: connecting with the press and DIY communication – Kate McAlpine