In this colloquium, I will give an overview of some of the nano optics related projects we have pursued in my laboratory over the past few years. The main focus will be on the properties of metal nanostructures, which possess electromagnetic resonances at optical wavelengths. These resonances, known as localized surface plasmon resonances, act to concentrate light into nano-scale hotspots, where the intensity can be enhanced by several orders of magnitude. I will discuss how we are taking advantage of this effect in two different research projects. The first of these is our use of metal nanoparticles to enhance the nonlinear optical properties on thin films by taking advantage of the fact that the efficiency of nonlinear optical effects increases with intensity. In the second project, we are working to create well-ordered assemblies of nanoparticles, akin to regular molecules, but with nanoparticles instead of atoms. The underlying principle is to use the plasmon resonances to locally modify the surface properties of metal structures to transform the hotspots into particle-to-particle binding sites. I will also describe ongoing projects aimed at deep microscopic imaging inside turbid media, and at creating a new class of nanophotonic devices based on actuatable polymer films.

According to computer simulations, the slowest, largest-scale harmonic motions of solvated biomolecules and the relaxation times of water occur on the picosecond regime. Experimental methods for the characterization of these collective vibrational modes, however, have been severely lacking. In response, I have developed the world's highest precision, highest sensitivity and highest frequency dielectric spectrometer. Operating over the frequency range from 65 GHz up to 1 THz, this spectrometer provides an unparalleled ability to probe the dynamics of water and aqueous proteins over the 100 fs to 10 ps timescale. Using this spectrometer to characterize the collective dynamics of solvated lysozyme I find that the collective vibrational modes of this protein are characterized by a hitherto unrecognized cutoff at 250 GHz (corresponding to 0.6 ps) arising due to the finite size of the molecule. Employing an effective medium approximation to describe the complex dielectric response of the protein in solution I find that each molecule is surrounded by a tightly held layer of 164 ± 5 water molecules that behave as if they are an integral part of the protein. Following studies of the spectra of water and of aqueous salt solutions I identify three Debye relaxations with the characteristic times of 8.56, 1.1 ps and 179 fs (at 25°C). Of note, while the relative strengths of these relaxation modes depend in a systematic way on solute concentration, their relaxation times do not. The observation sheds new light on the femtosecond to picosecond collective dynamics of water and solvated biomolecules.

[1]. N. Q. Vinh, et al., JACS 113, 8942 (2011)

Gamma-ray bursts are incredible machines capable of accelerating an Earth's mass of plasma to relativistic speed in a blink of an eye and to release in just a few seconds more electromagnetic radiation than the Sun can in 10 billion years. I will review the slow investigative process that led to our understanding of these extreme objects through 40 years of blunders, insight, and intuitions. Coming to the present day, I will delve into the exciting technological and theoretical advances that we have seen in the last few years to describe our current understanding of the bursts' physics, its observational foundations, and the challenges that await ahead.

Early universe cosmology is entering a new phase thanks to more precise measurements constraining the primordial density inhomogeneities. The Planck satellite and current and near future Large Scale Structure surveys are pursuing statistics of the inhomogeneities beyond the well-measured power spectrum. The potential of these new statistics has changed the way we think about theories of the primordial universe, including inflation. I will present the current understanding of how new data may decode the particle physics of inflation and provide more compelling tests of the theoretical framework for the primordial universe.

Capitalizing on rising energy prices, growing concern about global warming, interest in reducing reliance on fossil fuels, and a favourable political climate, the nuclear industry is working to achieve a renaissance around the world. Worldwide interests particularly focus on generation IV and fusion reactor systems. Both advanced fission and fusion energy systems require the development of materials able to resist to high operating temperatures, high neutron exposure levels, and high thermo-mechanical stresses. In addition, the transmutation products generated in structural materials by the high energy neutrons produced in the deuterium-tritium plasma in nuclear reactors can also drastically change the microstructure evolution in these structural materials, and consequently their mechanical behaviours.

Many efforts have been deployed to develop irradiation-damage-resistant alloys. Certain features, which can improve irradiation-damage resistance have been identified such as (a) a high, stable dislocation sink strength, and a high number density of nanometer scale precipitates which act as trap sites for He bubbles to avoid their swelling and to protect grain boundaries against embrittlement, and (b) fine grain size and high dislocation densities to ensure high creep strength to allow their operation at temperatures above the atomic displacement regime.

Prior works on this topic show that a high-number density of nanoscale Y-Ti-O clusters can improve creep resistance. It is also believed that the Y-Ti-O clusters, in addition to impeding dislocations and reducing grain-boundary mobility, act as traps for insoluble helium that would be generated in fusion reactor structural components. However, many questions exist related to the formation, structure and thermal stability of these Y-Ti-O nanoparticles that affect the optimal processing method and their performance in extreme environments. For example, it is necessary to understand their kinetic pathway of precipitation during an anisothermal heat treatment in order to develop improved processing methods and fully understand their atomic-scale structure and composition. Kinetic Monte Carlo techniques provide the ability to understand the kinetic paths controlling the precipitation of nanoclusters at the atomistic scale.

In our study, we provide insight into how oxides nanoclusters form in Fe-Ti-O and Fe-Y-O ternary alloys, shedding light on the complex kinetic pathway to precipitation in Fe-Y-Ti-O quaternary alloys. Then, we make the link between the microstructure evolution and the mechanical properties. We will conclude by highlighting a number of ongoing problems relative to the improvement of nanostructured ferritic alloys.

I will discuss possible uses of neutrinos in (very) long range communication and the Search for Extra-Terrestrial Intelligence. I will also give a brief introduction to the so-called Fermi Question/Paradox.

The discovery of the string / gauge theory duality known as the AdS/CFT correspondence revolutionized our ideas about gauge theories, gravity and space-time. For example it showed that, by changing the strength of certain interactions a theory can develop new dimensions and gravity can emerge. It has also suggested new connections between general relativity, the physics of fluids and condensed matter physics. In this talk I will describe the main ideas behind this duality and its applications borrowing examples from my recent work, in particular describing recent results related to the study of shock waves in strongly coupled plasmas.

In this colloquium I will summarize the work done by the Virginia Tech group comprised of Lay Nam Chang, Zack Lewis, Djordje Minic, Tatsu Takeuchi and Chia Tze, on the generalization of the reigning framework of physics, to wit, quantum theory. I will illustrate the uses of such a superquantum theory in some of the major problems of physics: the formulation of quantum gravity, the nature of the initial state and the problem of the vacuum (or dark) energy.

Quantum field theories arise as low energy effective descriptions for gapless states in condensed matter systems. In this talk, I will discuss about examples where non-perturbative tools shed some light on emergent phenomena in strongly coupled gapless states. In the first part, I will talk about a 2+1 dimensional lattice model where emergent superconformal symmetry enables one to understand a strongly interacting critical point non-perturbatively. In the second part, a 2+1 dimensional chiral non-Fermi liquid state will be discussed where a matrix/string theory emerges in the low energy limit.

The object seen in the CMS and Atlas experiments referred to as Higgs boson is now much closer to final confirmation. The latest results on cross sections, spin-parity and couplings all continue to be consistent with the Standard Model Higgs. The low mass of this object may indicate that a rich spectrum of particles exist at relative low masses one of which may be the dark matter candidate.

Engineered biological circuits expressed in living cells are becoming increasingly attractive as a technology, but the rational design of biological circuits has been hindered by a relative scarcity of robust design principles. Synthetic biology offers one solution to this problem by testing design principles in smaller circuits with known components. In this talk, I outline the exploration of design principles in three separate synthetic settings (oscillators, queueing systems, and multicellular environments) where the origin of robust dynamic behavior has been linked to simple but sometimes ignored interactions.

The $\Lambda$CDM cosmological model successfully describes the Universe at large scales. But it fares less well in accounting for some crucial galactic dynamics, specifically the observed flat galactic rotation curves and the Tully-Fisher relation. In stark contrast, the scheme of Modified Newtonian Dynamics works well at the scale of galaxies, but is less successful at larger scales. C.M. Ho, D. Minic and I combine the salient features of both paradigms by proposing the concept of MONDian dark matter, which behaves like cold dark matter at cluster and cosmic scales but emulates MOND at galactic scales. In our approach, the connection between global physics and local galactic dynamics is apparent. I will also argue that the quanta of MONDian dark matter (as well as dark energy) obey infinite statistics, rather than the familiar Bose or Fermi statistics.

One of the key challenges in nanoscience/medicine is to design carrier system for drug delivery or imaging that selectively binds to target cells without binding to healthy cells. A common strategy is to end-functionalize the polymers coating of the delivery device with specific ligands that bind strongly to overexpressed receptors. However such devices are usually unable to discriminate between receptors found on benign and malignant cells. We demonstrate, theoretically, how one can achieve selective binding to target cells by using multiple physical and chemical interactions. We study the effective interactions between a polymer decorated nanosized micelle or solid nanoparticle with model lipid layers. The polymer coating contains a mixture of two polymers, one neutral (e.g., polyethylene glycol) for protection and the other a polybase with a functional end-group to optimize specific binding and electrostatic interactions with the charged lipid head-groups found on the lipid surface. The strength of the binding for the combined system is much larger than the sum of the independent electrostatic or specific ligand-receptor binding. Moreover, it is found that the molecular organization of the polymer coating is qualitatively different in the combined system. This is manifested in the strength of the binding and also in a regime of distances where the addition of two repulsions leads to an attraction.

The search for optimal binding conditions lead to the finding of the non-trivial and highly non-additive coupling that exists in systems where chemical equilibrium, like acid-base reactions and ligand-receptor binding, molecular organization, and physical interactions are coupled together.

In this talk, I will outline recent progress in connecting string theory (a consistent quantum theory of gravity) with contemporary particle physics. This will include new results on two long-standing challenges in string constructions. The first is a large scale, algorithmic study of ways to geometrically realize the Standard Model of particle physics in string theory. The second is a presentation of new tools, which prevent unphysical massless particles from arising in the low energy physics of a string solution.

Charged lepton flavor violation is a more or less universal feature of physics models beyond the Standard Model, and fact that no such violation has ever been observed already places significant constraints on such models. From the experimental standpoint, it's particularly attractive to search for the conversion into an electron of a muon which has been captured on a nucleus, via the exchange of a virtual neutral particle. This is related to the search for the muon to decay to an electron and a photon, but is sensitive to a broader range of physics. It also has the striking experimental signature of a mono-energetic electron with no Standard Model background. The Mu2e experiment has been proposed to search for this conversion at a sensitivity almost four orders of magnitude beyond existing limits. This talk will discuss the physics goals and experimental technique, as well as the plan for modifying the Fermilab accelerator complex to provide the required beam intensity and structure.

Self-assembly plays a central role in producing ordered superstructures. The crucial question is to identify the necessary features that a macromolecular monomer must have in order to drive self-assembly into a desired complex structure. In this talk I will present our recent work on the self-assembly of model microtubules. The model monomer has a wedge-shape with lateral and vertical binding sites. Using MD simulations, we calculated a diagram of the self-assembled structures from these monomers. A modified Flory-Huggins theory was developed to predict the boundaries between different structures that match well with simulation results. We found that to form tubules the interaction strengths must be in a limited range. In addition, helical tubes are frequently formed even though the monomer is nonchiral. The occurrence of the helical tubes is related to the large overlap of energy distributions for nonhelical and helical tubes. To enhance structural control of the self-assembly, we added chirality and a lock-and-key mechanism to the model. We could control both the pitch of the helicity and the twist deformation of the tube by modifying the locations of the binding sites and their interaction strengths. Our results shed new light on the structure of in vitro microtubules formed with various numbers of protofilaments of tubulins, which also exhibit similar twisted structures and various pitches, and have determined the fundamental features of macromolecular monomers for self-assembly into a tubular structure.

Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

In this talk, I will discuss two topics that are synergistic within the context of developing the next generation of scientists: (1) explicit, and early instruction in scientific reasoning and science process skills, and (2) application of these skills within an interdisciplinary undergraduate research group. I am a materials scientist with an interdisciplinary research program and a science education researcher with an agenda that focuses on the underlying aspects of science that connect all disciplines. This blended talk will highlight both programs, with the underlying theme being undergraduate research. Specifically, I will discuss the implementation and assessment of a freshman first-year experience for physics majors titled "Models in Physics," where the foundation is an explicit approach to scientific process and reasoning. Labs go far beyond traditional approaches, instead utilizing "authentic research experiences" where students not only construct new content knowledge, but also reflect on their own processes for developing new knowledge. These skills are also practiced and reinforced through participation in directed research in my electronic materials lab, sometimes starting as early as the second-semester of the freshman year. My undergraduate research group has been developing and testing phenomenological electron transport models for ultraviolet illuminated surfaces of wide band-gap films, nanomaterials, and bulk. These models make predictions that students can test, with cross-disciplinary applications in chemical catalysis, biological and environmental remediation, and device engineering. As a teacher/scholar, I see no distinction between the activity within my undergraduate electronic materials research group and good teaching, specifically with respect to developing science process skills, and learning how to develop and test physical models. These types of skills should be introduced early, and reinforced often.

From the simple rules that determine how a material behaves, novel effects can arise. In this talk, we examine a prototypical example of this phenomenon. Some materials have spin degrees of freedom which are geometrically frustrated. This geometric frustration can interfere with the formation of a typical ordered state leaving instead an exotic spin liquid which is topologically ordered; manipulating topologically ordered states may be a key step in building quantum computers. Such emergent phenomena are often difficult to understand analytically. We will see how sophisticated algorithms allow us to compute properties and deepen our understanding of materials. Emphasis will be placed both on explaining the physics as well as the numerical approaches we use.

Organic functional materials based on pi-conjugated molecules and polymers are candidates for the next generation flexible electronics and renewable energy technologies. Their attractiveness is rooted in their flexibility and the promise of low-cost, large-scale fabrication. The diversity of molecular motifs ensures a broad configuration space for the design and synthesis of new materials. Organic materials exhibit unique behavior such as the presence of self-trapped localized charges ("polarons") and the localization of electronic excitations ("excitons"). Organic-based interfaces, in particular, play a central role in enabling the exciton dissociation processes that is fundamentally important to organic photovoltaics. I will describe theoretical investigations of self-trapped localized hole polarons, optical excitations, interface energy level alignment, and interface dipoles in an array of organic assemblies that enlists molecular crystals, oligomers, inorganic/organic hybrids, and organic molecule/fullerene interfaces. I will highlight an investigation combining theory and experiment of the charge separation process at a donor/acceptor interface. I will discuss theoretical challenges in the first-principles electronic-structure treatment of localized excitations and interfacial electronic structures. I will outline future directions in the computational design of organic polymers for photovoltaic applications requiring high efficiency and photochemical stability.

Recent experiments on the conductance of thin, narrow superconducting strips have found periodic fluctuations, as a function of the perpendicular magnetic field, with a period corresponding to approximately two flux quanta per strip area [A. Johansson et al., Phys. Rev. Lett. 95, 116805 (2005)]. We argue that the low-energy degrees of freedom responsible for dissipation correspond to vortex motion. Using vortex/charge duality, we show that the superconducting strip behaves as the dual of a quantum dot, with the vortices, magnetic field, and bias current respectively playing the roles of the electrons, gate voltage, and source-drain voltage. In the bias-current vs. magnetic- field plane, the strip conductance displays what we term "Weber blockade" diamonds, with vortex conductance maxima (i.e., electrical resistance maxima) that at small bias-currents correspond to the fields at which strip states of N and N + 1 vortices have equal energies.

Gravitational waves sap orbital angular momentum and energy from a black hole--neutron star (BH-NS) binary, driving it to inspiral and merge. In the violence of merger, the NS may tidally disrupt and form a hot accretion disk with the collimated magnetic fields necessary to launch jets, providing the central engine for one of the most energetic phenomena in the Universe: a gamma-ray burst (GRB). We assess the feasibility of this scenario with numerical relativity simulations of magnetized BH-NS binary mergers, seeding the NS with magnetic fields and exploring their effects on the remnant disk and the gravitational waves. We find that the gravitational waves are likely to be detectable by Advanced LIGO if the merger occurs within ~100Mpc, though the effects of magnetic fields on the waveforms are likely negligible. Further, we find that a GRB central engine may form if large-scale poloidal magnetic fields anchored in the disk are accreted onto the BH after the NS disrupts.

The class of spacetimes with event horizons contain some of the most fascinating solutions to the equations of general relativity. Over the past few years, numerical simulations of the field equations have begun to reveal some of the more dynamical, strong-field solutions not amenable to exact analytical or perturbative treatments. In this talk, I will describe 3 such scenarios. First, the inspiral and merger of two black holes, which is thought to occur frequently in the universe. Such events are powerful emitters of gravitational waves, and a concerted world-wide effort is currently underway to observe the universe through gravitational waves. Second, I will discuss the ultra-relativistic collision of two solitons. Arguments suggest that at sufficiently high velocities gravity dominates the interaction, causing a black hole to form. These arguments underlie claims that the Large Hadron Collider will produce black holes in speculative large extra dimension scenarios. Finally, I will show results elucidating the fate of a black string in 5 dimensions, subject to the Gregory-Laflamme instability. Rather remarkably, the event horizon exhibits dynamics akin to a low viscosity fluid stream suffering the Raleigh-Plateau "beading" instability. In the gravitational process arbitrarily large spacetime curvatures are revealed to an external observer, culminating in naked singularities. This is therefore a generic example of cosmic censorship violation in higher dimensional Einstein gravity.

Linear polymers are flexible chain molecules containing many chemical repeat units. The motion of individual polymers in a dense polymer liquid (molten plastic) is severely constrained by surrounding chains, and by the fact that chains cannot cut through one another. Effectively, polymers may be considered as being confined inside a tube-like region. The tube diameter, or the entanglement length, is the key parameter needed by the standard molecular theory for polymer rheology. But a molecular understanding of the origin of the tube diameter is still lacking. We approach this problem by closing polymers into rings, in order to obtain a system with well-defined, permanent topology, and using tools from the mathematical theory of knots to identify and count topological entanglements. For simulated polymer melts, this approach enables us to get a tube diameter value that is based on topological considerations alone, and that agrees with values obtained by more heuristic methods. We use this approach to study the effects of chain flexibility and addition of diluents upon the tube diameter.

Another consequence of the unique chain-like structure of polymers is the presence of composition fluctuations at the length scale of a polymer coil size. These composition fluctuations can be measured by small angle neutron and X-ray scattering. Understanding these fluctuation phenomena is important for understanding the structure and self-assembly behavior of multi-component polymeric systems. We show that composition fluctuations in systems of diblock copolymers can be accurately described by a statistical mechanical theory that we developed, by comparing its predictions with simulation results.

On February 23, 1987 we collected 24 neutrinos from the explosion of a blue super-giant star named Sanduleak in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, confirming the basic paradigm of core-collapse supernova. During the 26 years we have been waiting for a repeat of that momentous day, the number and size of neutrino detectors around the world has grown considerably. If the neutrinos from the next supernova in our Galaxy arrive tomorrow we shall collect tens of thousands of events and with so much data we ought to be able to discover much more about the inner workings of the explosions. But it is also now apparent that the message is much more complex than previously thought because many time, energy and flavor dependent features are imprinted upon the signal either at emission or by the passage through the outer layers of the star. To decode the message and extract quantitative information that can be used to test simulations we have to understand how all these features arise and how they depend upon the explosion dynamics. In this talk I present our current expectations of the time, energy and flavor dependent evolution of the neutrino signal from the next Galactic supernova and our recent efforts to self-consistently suture together the various transformation effects that can occur.

Physical aging was introduced to physics in Struik's ground-breaking experiments on reproducible and universal properties in glasses. Since then, spontaneously occurring relaxations in numerous many-body systems far from equilibrium have been systematically investigated. It has turned out that physical aging can be characterized by the simultaneous properties of (i) slow relaxation, (ii) breaking of time-translation-invariance and (iii) dynamical scaling. A survey on systems undergoing physical aging will be given, which will concentrate on non-glassy systems. Particular emphasis will be laid on the similarities and differences of the aging behavior of systems with or without an equilibrium stationary state. The one-dimensional Kardar-Parisi-Zhang equation will serve as paradigmatic example.

I will give an overview of modern efforts to link string theory, a theory of quantum gravity, to experimental physics. I will begin the talk by providing an introduction to the field, outlining some of the successes and problems of this approach to high energy physics. I will then describe the state of the art in this research area, emphasizing what has been achieved and what still remains to be accomplished. Finally, I will briefly discuss the future prospects of this attempt to link string theory to measurable physical phenomena.

Recent advances in microfabrication of graphitic samples that are only a few carbon layers thick allow one to test some of the theoretical predictions made in the context of the strong coupling Quantum Electrodynamics. The electronic band structure of graphene-like materials is characterized by a pair of nodal points, in the vicinity of which the low-energy quasiparticle excitations can be described as 2+1-dimensional massless Dirac fermions with a physical spin 1/2 and an additional orbital quantum number. However, in degenerate semimetals, such as graphene, the Coulomb interactions are expected to play an important role, largely due to their poor screening, so that they might generate a finite spectral gap due to emergent charge or spin ordering. In this talk, we review some theoretical predictions based on this scenario and their current status.

Quantum Gravity and non equilibrium thermodynamics explore vastely different realm of physics. There is however growing evidence that they might be deeply related. In this talk we review to what is the evidence in favor of a thermodynamical interpretation of gravity, what light in brings to non equilibrium thermodynamics and more importantly what lessons non equilibrium theromodynamics can teach us about gravity.

Observations have confirmed that the Universe has only matter and no anti-matter. Since laws of physics seem to be dominantly symmetric between matter and anti-matter, a major puzzles of present day cosmology is to understand where this asymmetry came from. In 1966, Andrei Sakharov suggested a framework, where, if certain conditions are satisfied by the laws governing the world of sub-atomic physics, this asymmetry could be understood. However no convincing working model existed. An interesting recent development is that theoretical attempts to understand the unrelated observation that neutrinos have mass, has provided models with all the right ingredients for this purpose and optimism seems to be growing that an understanding of the cosmic riddle of matter-anti-matter asymmetry, may finally be at hand. Extension of the same ideas could also unravel the more puzzling mystery of dark matter in the Universe. This pedagogical talk will introduce the field and summarize this physics, which if confirmed will have profound ramifications for cosmology and for physics beyond the standard model of forces.

The physical properties of nanoscale materials are known to differ significantly from their counterparts in bulk materials, when they exist. This is also to be expected for thermal conductivity. However, there is very little data concerning thermal conductivity, principally because the measurements are extremely difficult at this scale due to competing or "parasitic" thermal conduction in realistic test structures. I will describe a nanofabricated electrothermal test structure for directly measuring the thermal conductivity of aluminum nanowires near room temperature. Nanowires studied are 100 nm thick with 75, 100, and 150 nm widths. Thermal conductivity and electrical resistivity vary significantly across this range. We find that the Wiedemann-Franz law relating thermal and electrical conductivities is still useful provided the phonon contribution to the total thermal conductivity is taken into account.

In the next 5 years, ground-based interferometers such as advanced LIGO and Virgo are likely to provide the first direct detections of gravitational waves. This will constitute a major scientific discovery, as it will permit a new kind of observation of the cosmos, quite different from today's electromagnetic and particle observations. In this talk I will review the current effort at developing accurate waveform models, so that we can take full advantage of the sensitivity of the detectors when searching for gravitational waves from coalescing binary systems composed of neutron stars and/or black holes.