College of Arts and Sciences

Planets Around Nearby Stars

Modern science began with Copernicus speculating that the Earth is a
planet and that all the planets orbit the Sun.  Bruno followed up by
speculating that the Sun is a star, that other stars have planets, and
other planets are inhabited by life.  For this and other heresies,
Bruno was burned at the stake in a public square in Rome in 1600.
Astronomy and extrasolar planets were a really hot field at the time.

Over the past 20 years more than a thousand extrasolar planets have
been found,

Active Brownian particles: From individual to collective behavior

Single self-propelled particles as well as ensembles of self-propelled particles are examples of non-equilibrium states and a topic of the interdisciplinary research at the borderline between physics and biology. Interesting examples of self-moving objects come from biology, these are bacteria, eukaryots, amoeba, insects, fishes and animals etc. But also in physics self-moving objects are known, which are active colloids and moving spots in reaction-diffusion systems.

I will review various models of self-propelled particles from a viewpoint of statistical physics. Special attention is payed to the influence of noise on the dynamics of single particles and on the exhibition of spatial structures in groups of interacting moving particles.

Active Matter: from colloids to living cells

Collections of self-propelled entities, from living cells to engineered microswimmers, organize in a rich variety of active fluid and solid states, with unusual properties. For instance, active fluids can flow with no externally applied driving forces and active gases do not fill their container. In this talk I will describe the behavior of such “active materials”, focusing on two examples of liquid-solid transitions driven by active processes. The first is the formation of cohesive matter with no cohesive forces in collections of purely repulsive active colloids. The second describes the properties of epithelial tissues that exhibit a liquid-solid transition at constant density driven by cell motility,

Origins, Evolution and Biophysics: an Ephemeral Golden Braid

Douglas Hofstradter’s celebrated 1979 book, Gödel, Escher, Bach: An Eternal Golden Braid (“GEB”), presented “a metaphorical fugue on minds and machines in the spirit of Lewis Carroll.”  In this talk we likewise seek to explore implicit themes and hidden connections that unite origins and evolution (in a broad sense) with biophysical principles underlying modern biochemistry and molecular genetics. Three vignettes will be presented in which an evolutionary perspective provides coherence to a clutter of molecular details. Just as GEB sought to decipher how systems acquire meaning despite being made of meaningless elements,

Dark Matter Bound States and Indirect Dark Matter Signals

Most of the mass density in our universe is not composed of the familiar particles that make up atoms. Rather it is something different that goes by the name dark matter. We have considerable evidence for dark matter, for example, through of its gravitational influence on the motion of stars. The current theory of elementary particles has no candidate for the dark matter and it is probably a new type of particle. A number of experiments search for dark matter including the direct detection experiments which look for its scattering off nuclei.  

Can theoretical physics help cancer biology? The case of metastatic spread

In order to spread from the primary tumor to distant sites, cancer cells must undergo a coordinated change in their phenotypic properties referred to as the “epithelial-to-mesenchymal” transition.  We have studied the nonlinear genetic circuits that are responsible for this cellular decision-making progress and propose that the transition actually goes through a series of intermediate states. At the same time, we have formulated motility models that allow for the correlation of state of this network and the cell’s biophysical capabilities. Hopefully, these efforts will help us better understand the transition to metastatic disease and possible treatments thereof.

An Uncooperative Universe: Large Scale Anomalies in the CMB

The Cosmic Microwave Background Radiation is our most important source of information about the early universe. Many of its features are in good agreement with the predictions of the so-called standard model of cosmology — the Lambda Cold Dark Matter Inflationary Big Bang Theory. However, the large-angle fluctuations of the microwave background are uncooperative with “the program” — they continue to exhibit several statistically significant anomalies. On the one hand, if we look at the whole sky the lowest multipoles seem to be correlated both with each other and with the geometry of the solar system.

Harsh Mathur on the prize in Physics; Michael Hinczewski on the prize in Chemistry; and Alan Tartakoff on the prize in Physiology or Medicine. Followed by a reception. 

Abstracts

Quantum Spin Liquids

The search for truly quantum phases of matter is one of the center pieces of modern research in condensed matter physics. Quantum spin liquids are exemplars of such phases. They may be considered “quantum disordered” ground states of spin systems, in which zero point fluctuations are so strong that they prevent conventional magnetic long range order. More interestingly, quantum spin liquids are prototypical examples of ground states with massive many-body entanglement, of a degree sufficient to render these states distinct phases of matter. Their highly entangled nature imbues quantum spin liquids with unique physical aspects,

Nitride Semiconductors: Beyond the Binaries

The binary nitride semiconductors and their alloys have led to transformations in both lighting and power electronics. They have also given us new physics such as polarization-induced topological insulators. But nitride semiconductors can be built of more than two elements. What new science and technology might we expect from such increased complexity?