With the advent of 8-10 meter optical telescopes, multi-wavelength instruments, and space-based observatories, observational astronomy has made extraordinary progress in the past decade. We are now able to study galaxies from when the universe was less than a billion years old to now. However, connecting the points in the timeline to understand how galaxies form and evolve remains a fundamental question in modern astronomy. The standard theoretical paradigm of hierarchical assembly requires that galaxies form via continuous merging of younger, less massive components, but this conflicts with the vast majority of current observations. A viable solution that is gaining support is the merging of galaxies that are already massive and old. I will present examples from my research that conclusively show how many galaxies, in particular the ones that are a hundred times more massive than our own Milky Way, form via galaxy-galaxy merging.

In this informal general talk I would like to summarize a very exciting recent research done here at VT regarding the analytic treatment of one of the most fundamental theories in contemporary physics: the theory of strong interactions, better known as Quantum Chromodynamics, or QCD. I aim to give 1) a pedestrian introduction to pure QCD, 2) discuss its unique features as well as its relevance (both specific and general) and, finally, 3) outline the intuitive path that lead us to the recent exciting analytic results regarding the spectrum of pure QCD.

Most energetic materials are molecular solids having complex crystal structures composed of polyatomic organic molecules. Being exposed to some external stimuli they are capable of undergoing fast chemical decomposition with large energy release. Macroscopic properties of energetic substances are fairly well understood, especially in gas or liquid phases. Microscopic processes and behavior of the explosive solids are poorly known due to complexity of their structures and rapidity of the detonation initiation process. In this presentation, a brief review of results recently obtained from ab initio modeling of defects in a series of energetic materials will be presented. The significant role of defects in changing properties of solids and controlling sensitivity to initiation of chemistry under extreme conditions will be discussed.

We all enjoy sunlight, but can't see the neutrinos streaming from the Sun without special detectors. While the former tells us about energy generated in the Sun 40,000 years ago, the latter only take eight minutes to get here from the center of the Sun. The luminosity of the Sun determined these two ways - via photons and via neutrinos - currently differ by 40% at one sigma. What's going on?

In trying to understand what the neutrino flux is telling us, we've discovered that neutrinos, originally thought to come in three distinct flavors, in fact oscillate from one flavor to another, an oscillation resonantly enhanced deep in the Sun by the MSW effect. However, we still have only directly measured high energy solar neutrinos: less than 90% of the solar neutrino flux.

This colloquium will describe the current situation, and the upcoming experiments designed to get at the lower-energy solar neutrinos. In particular, the Borexino and LENS experiments will be explained, including the pictures you may have seen on the walls showing Borexino being filled with water.

Even though it will be 75 years this December since Pauli first postulated neutrinos, most of our current knowledge is the product of last decade's experimental activity. In the first part of this talk I will review what we learned from solar, atmospheric, reactor and laboratory neutrino experiments as well as cosmological observations. In the second part I will elucidate the role of neutrinos in supernova nucleosynthesis and discuss the complications due to the neutrino interactions. I will conclude with an outlook for the future.

The technique of parity-violating electron scattering has been used in several major experiments at electron acclerators over the past decade. There are two important physics questions being addressed by these experiments. How important is the "sea" of strange quark/anti-quark pairs in the electric and magnetic properties of the proton? Is there any evidence of "new" physics beyond the Standard Model. This talk will describe two experiments (G0 and Qweak at Jefferson Lab) that are using parity-violating electron scattering to answer these questions.

In recent years, a consensus has been built in the physics community that Maxwell's Demon, a being that can reliably violate the 2nd law of Thermodynamics, is impossible. The common lore is that this impossiblity stems from introducing information-theoretic considerations into the picture. More specifically the claim is that Landauer's principle, which states that there is an irreducible entropy cost to the erasure of the information, blocks any possible attempt to break the 2nd law. Recently, though, this claim has been disputed in the philosophical community.

In my talk, I will review these developments in the literature, and I endeavour to demonstrate the question of whether Maxwell's Demon can exist is a thorny one. Instead of a clear 'yes' or 'no' answer, the possibility of the existence of Maxwell's Demon depends on a delicate and nuanced understanding of the 2nd law, how terms like temperature and entropy are understood in the context of statistical mechanics, and whether one can meaningfully introduce information-theoretic notions into the formalism of statistical mechanics. I conclude that the debate over Landauer's principle is largely a red herring, stemming from a set of conceptual confusions and an overemphasis on the particulars of the Szilard engine (the thought experiment on which these arguments are based) that cannot be generalised to preclude all possible demonic setups.

Understanding and predicting the properties of quantum many-particle systems remain an outstanding theoretical and computational challenge. In materials simulations, the standard model is an independent-electron approach in the framework of density-functional theory. In many materials where the effects of electron interaction are strong, this approach is inadequate. Several alternatives are being actively pursued. Among these, we have been developing a many-body, non-perturbative approach using auxiliary fields and stochastic sampling. Our approach takes the form of an ensemble of independent-electron calculations in fluctuating external fields. The different field configurations are "entangled" by random walks, and an approximate many-body wave function is obtained as a linear superposition of independent-electron solutions. I will discuss progress and prospects in the development and application of this approach. Results will be presented on electronic structure computations in atoms, molecules, and bulk materials.

The discovery that neutrinos have nonzero masses has raised a number of very interesting questions. After reviewing what we have learned so far about the neutrinos, we will identify the open questions, explain why they are interesting, and discuss the evolving experimental program to answer them.

I will begin with a brief review of QCD, the theory of the strong interactions, and describe the basic ideas underlying the effective field theory approach to QCD phenomenology. I then describe applications of these methods to topical problems in the physics of hadrons containing charmed quarks. These include the production of J/ψ in collider experiments, elucidating the nature of recently discovered excited charmed strange mesons, the physics of the X(3872), a charmed meson molecule, and doubly charmed baryons.

Historically the term hydrodynamics was synonymous with fluid mechanics and referred to the study of the dynamics of fluids in motion under specified boundary conditions. Today hydrodynamics denotes the description of the collective large-scale dynamics of a wide class of systems, from magnets to crystalline solids, in terms of a small number of conserved and broken symmetry variables. After introducing some of the general ideas behind modern hydrodynamics, I will discuss its application to soft condensed matter and biological systems. I will introduce a new class of soft active complex matter to which energy is continuously supplied by internal and external sources. As an important example of active matter I will describe the structure and mechanical propoerties of the cell cytoskeleton. This is a complex network of long biopolymers crosslinked by motor proteins that act like nanomachines, supplying energy to the filament network and controlling its structure and function.

Dengue fever, a multistrain disease, has four distinct co-existing serotypes (strains). The serotypes interact by antibody-dependent enhancement (ADE), in which infection with a single serotype is asymptomatic, but contact with a second serotype leads to serious illness accompanied by greater infectivity. It has been observed from serotype data that outbreaks of the four serotypes occur asynchronously (Nisalak et al., Am. J. Trop. Med. Hyg. 68: 192). We present a compartmental model for multiple serotypes with ADE, and consider autonomous, seasonally driven, and stochastic versions of the model. For sufficiently small ADE, we find that the number of infectives of each serotype synchronizes, with outbreaks occurring in phase. However, when the ADE increases past a threshold, the system becomes chaotic, and infectives of each serotype desynchronize. Certain primary and secondary infective compartments remain synchronized in the chaotic regime, a result which is explained by our analysis and which may be useful for disease monitoring. Spatial effects are included via coupled patch models and reaction diffusion equations. We observe desynchronization between spatially distinct regions.

Neutrinoless double beta decay has recently become a top priority for the global neutrino physics program. Double beta decay has may resolve the scale of the neutrino mass spectrum, and is also the only practical tool we have for understanding the particle/anti-particle nature of the neutrino. The EXO collaboration is developing sensitive searches for the double beta decay of Xenon-136. Our first experiment, EXO-200, is rapidly being constructed, and will be by far the largest double beta decay experiment ever attempted. We are also pursuing R&D to realize a system to tag the daughter barium nucleus of the decay using the techniques of single-ion spectroscopy. This would eliminate all conventional radioactive backgrounds, resulting in an ideal experiment. This colloquium will summarize the current status of our work.

The positive pion has been observed to decay into positive (anti) muons and neutrinos and rarely into positrons and neutrinos. The measurement of the relative rates has a history longer than 50 years. This history, that includes personalities of many important physicists of the 20th century will be reviewed and a new experiment discussed. The experiment can provide an extremely sensitive test of the Standard Model. Some of the illustrations will be scanned images of journal articles and for a good view sit closer to the screen.

Exchange bias (EB) is a fundamental interface phenomenon in coupled magnetic thin films with significant impact in modern spintronic applications. Atomic proximity of adjacent layers gives rise to exchange coupling at the interface between a ferromagnetic (FM) thin film and a magnetic pinning layer. The latter is conventionally antiferromagnetic (AF) but can also be realized by a hard FM film. In both cases interface coupling induces unidirectional magnetic anisotropy in the FM top layer which causes its hysteresis loop to shift along the magnetic field axis. When cycling the heterostructures through consecutive hysteresis loops a monotonic change of this shift, known as the training effect, is observed. Here I report on the electric and magnetic field control of the EB. Electric control is realized in a Cr₂O₃(111)/(Co/Pt)₃ heterostructures, taking advantage of the magnetoelectric properties of the AF Cr₂O₃ pinning layer. Based on these experimental results novel spintronic applications such as pure voltage control of magnetic configurations in spin valve-type architectures are proposed. In addition, training of the EB effect is studied in novel all FM heterostructures of exchange coupled soft and hard FM thin films. Our experiments show unambiguously that EB training is driven by deviations from the equilibrium spin configuration of the pinning layer. The experimental data show excellent agreement with our theoretical predictions including a subtle dynamic enhancement of the EB training effect.

Over the last few years the potential importance of quasar outflows on the growth of super-massive black holes, enrichment of the intergalactic medium, evolution of the host galaxy and cluster cooling flows has been widely recognized. I will review these new theoretical developments and describe the efforts of our research group to determine the most relevant parameters for these models: Kinetic luminosity and Chemical abundances of observed quasar outflows.

Swift was launched 2004 November 20. Since that time, the Burst Alert Telescope has detected approximately 2 gamma ray bursts (GRBs) per week, and the pointed instruments, including the X-ray Telescope and the Ultraviolet Optical Telescope, have slewed to a large fraction of these bursts with unprecedented speed. The prompt observation of GRB positions has allowed the X-ray telescope to study GRB afterglows at times that are several orders of magnitude earlier than past observations. Many exciting results have emerged, including X-ray afterglow detections of multiple short-hard bursts, ubiquitous flares at late times (100-10000 s) which imply delayed sporadic internal engine activity (increasing the energy requirements of GRB progenitors), a new canonical afterglow light curve that includes the transition from the prompt emission and multiple breaks in the power law-decay slope, very high redshift afterglow measurements that probe the early Universe, as well as other new results. A summary of these recent observations and their implications will be discussed, with particular emphasis on the emergence of new phenomena in the early X-ray afterglows of long bursts.

The recent construction of the VERITAS TeV gamma ray observatory and its possible scientific impact on GRB and blazar jets will also be briefly discussed.

X-ray binaries have a compact primary star (either a black hole or a neutron star) accreting material from a normal secondary donor star, and this mass transfer process generates copious amounts of X-ray emission. For decades X-ray binary stars in the Milky Way have taught us a great deal about the physics of accretion onto compact objects. However, the limited number of X-ray binaries in the Milky Way has set constraints on our progress in understanding black hole binary formation and evolution. Furthermore, only a small percentage of Milky Way X-ray binaries are accreting near the maximum rate allowed before radiation pressure begins to limit the supply of additional material onto the compact object, making it difficult to study accretion in the crucial high mass transfer rate regime. Fortunately, the Chandra and XMM-Newton X-ray observatories are overcoming these limitations and now we have studied large numbers of X-ray binaries in nearby galaxies, many of which are accreting near their maximum limit. In this talk, I will discuss how these data have provided enormous insight into the formation of X-ray binaries. In addition, I will present evidence that the most luminous X-ray binaries may best be explained by accretion onto "intermediate" mass black holes. Such black holes, intermediate in mass between stellar-sized black holes and supermassive black holes at the centers of galaxies, would greatly challenge our notions of black hole formation, since there are no widely accepted theoretical models of how black holes in this mass range can form.

I will explain how the transformation design method works. One begins this design process by imagining a fictitious space with an interesting or useful property, for example, a hole for hiding things, or a dense region that concentrates energy. I will explain how such fictitious spaces can be described mathematically by a coordinate transformation. Then I will explain how the theory of such coordinate transformations and the form invariance of Maxwells equations (also explainedI hope) leads directly to a material specification. This material specification can implement the electromagnetic properties of the interesting fictitious spaces in the boring, approximately "flat", three dimensional space in which we live.

We have used this method to design invisibility cloaks, but the method is quite general and can be used to design a wide variety of interesting devices that guide, concentrate or shape electromagnetic fields in ways that would be difficult to manage with other design methodologies. Applications range from stealth to energy conversion and distribution to wireless communications to biomedical imaging. The drawback of the method is the complexity of the material specifications that it produces, which have particular anisotropy (variation with angle) and inhomogeneity (variation with position). Only with recent advances in the field of metamaterials can these specifications be realized. I will discuss how metamaterials accomplish this and what their limitations are, e.g. bandwidth, absorption, frequency range etc. I will discuss in detail the recent implementation of an invisibility cloak in the microwave spectrum. Unlike, traditional stealth, an invisibility cloak reduces both reflection and shadow. Thus both these ways of detecting an object, (the reflection of electromagnetic waves incident on the front of an object and the blocking of electromagnetic waves originating from behind the object) are weakened. If such a cloak were implemented for visible light (a daunting task), then when one looked at the cloaked object one would see the scene behind it.

Recent advances in String Theory indicate that theories of quantum gravity have equivalent holographic descriptions in terms of non-gravitational theories which live in lower number of dimensions. In this approach, space and time are not fundamental entities, but emergent concepts valid at low energies. This holographic viewpoint has been successfully used to understand puzzling aspects of Hawking radiation from black holes and is beginning to provide insights into the nature of cosmological singularities. This talk will review some aspects of these developments.

The possible existence of light, sterile neutrinos (neutrinos without a weak interaction) has been an open question in particle physics since the discovery of neutrino oscillations in the late 1990's. I will explain the physics motivation for (and against) this odd particle. I will also describe the MiniBooNE experiment, which is designed to test the experimental evidence for the sterile neutrino. The MiniBooNE result, testing the sterile neutrino hypothesis, will be shown and discussed.

Far field microscopy remains an essential tool in biological studies, particularly of live specimens. The availability of a wide range of specific fluorophores (dyes, proteins, Q-dots,...) has made fluorescence microscopy an indispensable tool for cellular dynamics studies. Highly sophisticated microscopic techniques have been developed during the past twenty years (confocal, multi photons,...). As it was about a hundred years ago, the main objective still remains the improvement of the spatial and the temporal resolutions. These two have often non compatible optimal solutions, as better spatial resolution invariably means longer acquisition times.

Digital holographic microscopy can capture 3D information in a single exposure, but cannot be used with fluorescence emission. During the past few years, I have developed a non coherent holographic microscopic method capable of acquiring 3D fluorescence distributions in a single 2D scan. The basic idea is simply to capture the hologram phase in the temporal domain rather than in the spatial domain, thus bypassing the need for any spatial coherence. I will discuss some of the possibilities of the method, and present some preliminary results.

We are used to visualizing space as a stage on which things move and time as a marker for the passage of events. I will describe how Einstein combined space and time into a dynamical entity called “space-time” that can warp and bend in response to matter, giving rise to the force of gravity. I will then discuss the emerging understanding of space and time as simply approximate descriptions of a much more complex underlying reality. In this picture, space and time can appear out of, or disappear into, timeless and spaceless voids.