College of Arts and Sciences

Some folk think that there are four types of force. Napoleon thought there were two. I am going to talk about three types. Of these, the most interesting by far is the entropic force, which is the one that drives us to explore the unknown. Along the way, we will reach some remarkable conclusions. But will they stand up to scrutiny? As a clue we mention that the word scrutiny itself comes from the Latin for “those who search through piles of trash in the hope of finding something of value.” Do come and scrute with us at the last colloquium of the semester.

Continue reading… Can that really be so? A light-hearted look at the concept of force in classical, quantum, and statistical mechanics – Philip Taylor

A variety of direct and indirect searches for dark matter are currently underway, a number of which have even reported observations which could be interpreted as hints of a signal. In this talk, I will discuss why particle physicists think that dark matter is likely to be made up of WIMPs, and how experiments are finally reaching the sensitivities needed to test the WIMP-hypothesis. If dark matter is, in fact, made up of WIMPs, then it seems likely that at least some of the search strategies being employed will be successful in the coming few years. If not, their null results are going to make it increasingly difficult to build viable particle dark matter models.

Continue reading… Closing In On Dark Matter – Dan Hooper

As Feynman noted, rules of chemistry are determined “in principle” by physics, but just as knowing the rules of chess do not immediately make one a great chess player, deriving chemistry from physics has challenged scientists for the past century. To predict thermodynamic properties of matter depends on two branches of physics: quantum mechanics, which governs the energetics and dynamics of elementary constituent particles; statistical mechanics, which deals with interactions of many particles and introduces the concept of temperature. This talk surveys new developments in computational thermodynamics that allow prediction of alloy phase diagrams and crystal structures truly from first principles.

Continue reading… Computational Thermodynamics: First Principles Prediction of Crystal Structures and Alloy Phase Diagrams – Michael Widom

Nearly two-thirds of all cancer patients in the U.S. receive radiation therapy to treat their illness. Many advanced technologies have been developed to create precise and optimized ionizing radiation treatments where patients are modeled as static objects. All current radiotherapy technology, however, has a major shortcoming: it cannot determine where the radiation is actually being delivered in a patient’s body while the treatment beam is on. This is because patients aren’t static objects; they’re people, and their bodies naturally and inherently move. This movement is often significant enough to cause the radiation to miss the intended target and unnecessarily irradiate healthy tissue,

Continue reading… Development of a magnetic-resonance-imaging-guided radiation-therapy device to treat cancer patients – James Dempsey

The pseudogap phase of cuprate oxides is one of the most perplexing phases in condensed matter physics; it is a poor metal that, at lower temperatures, becomes one of the best superconductors. Recently [1], the peculiarities of the pseudogap phase were beautifully captured by STM data on Bi2Sr2CaCu2O8+x in the form of an inhomogenious spatial pattern of density of states. From these pseudogap patterns, we construct liquid crystalline order parameter fields to quantify the symmetry breaking features [2,3]. These fields reveal two properties of the pseudo gap phase. It has a net anisotropy (nematic ordered) over at least 100 nm length scales and the anisotropy is locally disturbed by imperfections in another element of the pseudo gap pattern: a stripe-like (smectic ordered) pattern.

Continue reading… Electronic liquid crystal correlations in the pseudogap phase of high Tc cuprates – Michael Lawler

Thin-films are used in a variety of applications ranging from semiconductor technology to industrial coatings, sensors, and photovoltaic devices. In addition, understanding thin-film growth is a challenging scientific and technical problem which requires an understanding of surface and interface physics. After a brief review of some applications, I will discuss some new simulation techniques, including the kinetic Monte Carlo method as well as temperature-accelerated dynamics (TAD) and parallel TAD (parTAD) which have allowed us to make substantial progress. I will then discuss the application of these methods to study submonolayer and multilayer metal epitaxial growth. In particular, the results of simulations we have carried out in order to understand strain relaxation and “vacancy”

Continue reading… Temperature-accelerated dynamics and kinetic Monte Carlo simulations of thin-film growth – Jacques Amar

We constructed a corpus of digitized texts containing about 4 per cent of all books ever printed. Analysis of this corpus enables us to investigate cultural trends quantitatively. We survey the vast terrain of ‘culturomics,’ focusing on linguistic and cultural phenomena that were reflected in the English language between 1800 and 2000. We show how this approach can provide insights about fields as diverse as lexicography, the evolution of grammar, collective memory, the adoption of technology, the pursuit of fame, censorship, and historical epidemiology. Culturomics extends the boundaries of rigorous quantitative inquiry to a wide array of new phenomena spanning the social sciences and the humanities.

Continue reading… Culturomics: Quantitative Analysis of Culture Using Millions of Digitized Books – Erez Liebermann-Aiden

To understand how quantum mechanics works, it is useful to imagine alternative “foil” theories that work differently. Modal quantum theory is a discrete toy model that is similar in structure to ordinary quantum theory, but based on a finite field instead of complex amplitudes. The interpretation of this theory involves only the “modal” concepts of possibility and impossibility rather than quantitative probabilities. Despite its very simple structure, our toy model nevertheless includes many of the key features of actual quantum physics: interference, complementarity, entanglement, teleportation, the impossibility of cloning, pseudo-telepathy games, nonclassical computation, and more.

Continue reading… Almost Quantum Mechanics – Benjamin Schumacher

Dr. Denning will describe what actually happened in the Fukushima accident and provide an evaluation of the failure in safety practices that led to severe fuel damage. He will also discuss the expected health, environmental, and economic consequences of the event. Risk studies indicate that a similar ”station blackout” accident could occur in the U.S. but at a very low probability. Dr. Denning will describe some differences in the capabilities of U.S. plants similar in design to the Japanese plants to mitigate the consequences of such an event. The NRC has issued their 90-day report with recommendations regarding upgrades that could be required in operating plants in the U.S.

Continue reading… Fukushima and the Future of Nuclear Energy in the U.S. – Richard Denning

The foundations of quantum mechanics have been plagued by controversy throughout the 85 year history of the field. It is argued that lack of clarity in the formulation of basic philosophical questions leads to unnecessary obscurity and controversy and an attempt is made to identify the main forks in the road that separate the most important interpretations of quantum theory. The consistent histories formulation, also known as ”consistent quantum theory”, is described as one particular way (favored by the author) to answer the essential questions of interpretation. The theory is shown to be a realistic formulation of quantum mechanics, in contrast to the orthodox or Copenhagen formulation which will be referred to as an operationalist theory.

Continue reading… Why are there so many interpretations of quantum mechanics? – Pierre Hohenberg