The dynamic clustering of globular particles in suspensions exhibiting competing short-range attraction and long-range repulsion such as in protein solutions has gained a lot of interest over the past years. We investigate theoretically the influence of clustering on the dynamics of globular particle dispersions [1]. To this end, we systematically explore various pair potential models by a combination of state-of-the-art analytic methods in conjunction with computer simulations where the solvent-mediated hydrodynamic interactions are likewise included. Our theoretical results show that the cluster peak (intermediate-range-order peak) is present also in the hydrodynamic function characterizing the short-time dynamics, in accord with experimental data [2]. Enhanced short-range attraction leads to a smaller self-diffusion coefficient and a larger dispersion viscosity. The behavior of the (generalized) sedimentation coefficient is more intricate, e.g. showing non-monotonic interaction strength dependence.

 [1] J. Riest and G. Nägele, Short-time dynamics in dispersions with competing short-range attraction and long-range repulsion, Soft Matter 11, 9273 (2015).

[2] Collaboration with D. Godfrin (MIT), Y. Liu (NIST) and N. Wagner (UDEL), work in progress.

 

The progress in neutrino physics over the past fifteen years has been tremendous: we have learned that neutrinos have mass and change flavor. This discovery won the 2015 Nobel Prize. I will pick out one of the threads of the story-- the measurement of flavor oscillation in neutrinos produced by cosmic ray showers in the atmosphere, and further measurements by long-baseline beam experiments. In this talk, I will present the latest results from the Super-Kamiokande and T2K (Tokai to Kamioka) long-baseline experiments, and will discuss how the next generation of high-intensity beam experiments will address some of the remaining puzzles.

Outermost occupied electron shells of chemical elements resemble monopoles, dipoles, quadrupoles, and octupoles corresponding to filled s-, p-, d-, and f-atomic orbitals. Theoretically, elements with hexadecapolar outer shells could also exist, but none of the known stable elements have filled g-orbitals. On the other hand, the research paradigm of “colloidal atoms” displays complexity of physical behavior of colloidal particles exceeding that of their atomic counterparts, allowing for switching between colloidal elastic dipole and quadrupole configurations using weak external stimuli. This lecture will describe colloidal elastic hexadecapoles formed by polymer microspheres dispersed in a liquid crystal, a nematic fluid of orientationally ordered molecular rods. The solid microspheres locally perturb the uniform molecular alignment of the nematic host, inducing hexadecapolar and other elastic multipoles that drive highly anisotropic colloidal interactions. We uncover physical underpinnings behind the spontaneous formation of colloidal elastic hexadecapoles and describe the ensuing particle bonding inaccessible to colloids studied previously. The lecture will conclude with discussion of practical applications that can be enabled by combining unique properties of metal and semiconductor nanoparticles with facile switching of self-assembled ordered superstructures that they exhibit in nematic hosts.

 TBA

 TBA

The IceCube Neutrino Observatory has reported a diffuse flux of TeV-PeV astrophysical neutrinos in three years of data. The observation of tau neutrinos in the astrophysical neutrino signal is of great interest in determining the nature of astrophysical neutrino oscillations. Tau neutrinos become distinguishable from other flavors in IceCube at energies above a few hundred TeV, when the particle shower from the initial charged current interaction can be separated from the cascade from the tau decay: the two cascades are called a "double bang" signature. I will discuss the search for tau neutrinos in IceCube, including an analysis which uses the digitized signal from individual IceCube sensors to resolve the two showers, in order to be sensitive to taus at as low an energy as possible. This is the first IceCube search to be more sensitive to tau neutrinos than to any other flavor. I will present the results and prospects for future high energy tau neutrino searches in IceCube and beyond.

In this talk, I will summarize recent results from the South Pole Telescope 2500 deg^2 survey. This mass-limited survey has discovered hundreds of new galaxy clusters at 0 < z < 1.7, allowing an unprecedented view of galaxy cluster evolution. Using follow-up observations from Spitzer, Hubble, Chandra, XMM-Newton, Magellan, VLT, ALMA, ATCA, and Gemini, we are able to study the evolution of the stars, gas, and dark matter in these massive systems. Based on these data, we constrain the evolution of cluster galaxies, the central AGN, the cooling ICM, the heavy metal abundance of the ICM, the dynamical state of the cluster, and various other cluster properties. Looking forward, I will present several new and ongoing surveys which will dramatically change the landscape of galaxy cluster research in coming years.

The field of active matter is the result of applying statistical physics to the motion of biological and biomimetic systems, from animal flocks to the cell's cytoskeleton and from robotic swarms to self-propelled colloids. Unlike bird flocks, which can move around freely, cells inside an organism or filaments inside a cell move in a very confined space bounded by curved walls. What is more, the shape of the boundaries can affect the dynamics in dramatic ways. Recently my focus has been on building a theoretical framework to study such problems by combining the concepts of active matter with those of the geometry of curved surfaces. I will discuss what such an approach can teach us about the way active systems respond to the geometry of their environment and what I hope it can teach us about the way such systems deform their environment and regulate their own shape.