Voids are perhaps the most salient feature of the spatial distribution of galaxies and occupy most of the volume of the present-epoch universe. The properties of voids and the few objects that lie within them provide tests of structure formation theories that are complementary to studies of higher-density regions. Galaxy surveys such as the SDSS and 2dFGRS now cover sufficient volume to accurately quantify the voids. New simulation methods offer the dynamic range necessary for comparison with these data. Topics for this workshop will include both observational and theoretical aspects of voids, including the observational status of voids and their contents, statistical measures of the void distribution, future surveys to study void evolution, dynamics and formation of voids, formation of structure within voids, use of voids as tests of structure formation models, and advances in simulation methods.
A Panoramic View of Galaxy Evolution: Understanding how galaxies have formed and evolved to their present-day diversity of properties remains a grand-theme of contemporary astrophysics research. During the past decade, a number of extragalactic surveys, both space-borne and ground-based, have extensively probed galaxy properties as a function of cosmic time. Large efforts have been spent to explore complementary volumes of the observable parameter space, and to build large, multi-wavelength database, often publicly available, of images and spectra suitable to study a wide range of problems in galaxy evolution.
The 2006 Summer Aspen Workshop plans to bring together observers and
theoreticians to discuss the key results from all the large surveys -- of both
the nearby and distant universe -- and develop a consensus on general trends
of galaxy evolution. The workshop will review key observational and
theoretical/interpretative results, as well as key measures (at any redshift)
used to probe galaxy evolution, including galaxy star-formation rates, stellar
masses, physical properties of the stellar populations, and morphologies. It
will also address how galaxies' environment, and feedback from nuclear and
star-formation activity affect their evolution.
Andreev, Lifshitz, Chester, and Leggett suggested in about 1970 that a quantum crystal such as bulk 4He under pressure might show both crystallinity and superfluid behavior. Experiments within the last two years have found indications for such a supersolid phase. The theoretical explanation of superflow in a crystal assumed vacancies, however, they have not been seen experimentally and computer simulations do not find stable vacancies. Most microscopic calculations do not show superfluid response, but they are limited to equilibrium samples of small crystals. It is possible that defects such as grain boundaries, dislocations or impurities are an essential part of the mechanism leading to the supersolid signature observed. The ACP workshop will examine the lastest experimental and theoretical work on supersolids.
Structures in the Universe are thought to form hierarchically, through the accretion and destruction of smaller systems. This workshop aims to confront this picture with the latest observations of Local Group galaxies, compare these constraints with those imposed by higher redshift galaxy samples and discuss future prospects for local studies. The nearby Universe is the one place where galaxies might be deconstructed to examine the nature of the building blocks - age, size, gas, stellar populations and dark matter content - from which they were built. This offers the tantalizing possibility of reconstructing their histories from their present state and directly testing galaxy formation models.
Magnetic fields are an important component of astrophysical objects as diverse as the moons of Jupiter, planets, stars, accretion discs, galaxies and clusters. One of the striking features of magnetic fields in astrophysical bodies and laboratory experiments is
their large scale coherence and structure. It is remarkable that such structure can coexist with chaotic flows and multi-scale turbulence. Many of the key questions regarding the origin of magnetic field structuring remain to be answered. This workshop will address the physics of magnetic field organization: the processes that lead to magnetic field growth, field structuring and the roles of reconnection, instabilities and dissipation.
Key physics questions to be discussed are:
How are the processes of flux generation, flux conversion, and flux transport related in realistic laboratory and astrophysical situations? What is the nature of the transition between kinetically dominated (e.g. a classical turbulent dynamo) and magnetically dominated (e.g. a sawtooth event in a RFP) dynamos. What is the role of magnetic reconnection in dynamos?
How it is magnetic structure formed in turbulent plasmas and fluids? Does the turbulence enhance dynamo processes or hinder them? What specific flow characteristics are necessary to explain the observed structure? Is the structure during the kinematic growth phase of the magnetic field different from the structure in the saturated nonlinear state?Packing problems, such as how densely solid objects occupy space, have fascinated people since the dawn of civilization, and continue to intrigue scientists because of their connection to a host of problems that arise in the physical sciences, mathematics and materials science. While optimal packing problems are intimately related to ground states of condensed matter, disordered "jammed" sphere packings have been employed to model the glassy state of matter. Sphere packings in high dimensions have relevance in communications theory. Discrete geometers have a longstanding interest in packing problems. There are many open questions. What are the best packings of spheres in dimension greater than three? Can upper and lower bounds on the maximal densities aid in identifying the optimal arrangements in high dimensions? What are the densest packings of nonspherical objects in two and three dimensions? What is the precise connection between symmetry and optimal packings? Can random packings ever occupy space more densely than ordered packings? Can "randomness" be quantified in a meaningful and precise manner? Can the rigorous study of the hard-sphere model shed light on disorder/order phase transitions? Can the study of minimum energy configurations of interacting particles give insight into fundamental aspects of optimal packings? Examples of the cross-fertilization between the physical sciences and mathematics on packing problems abound. The aim of the workshop is to continue to foster the interchange of ideas between different fields by bringing together a diverse group of physicists, chemists, and mathematicians who work on packing problems.
Mesoscopic systems can broadly be defined as condensed matter systems which are both large enough to be engineered like the common macroscopic machines of everyday life but small enough to display the quantum-mechanical behavior usually found for the motion of microscopic particles such as electrons. Mesoscopic systems therefore bridge the gap between the macroscopic and the microscopic world. Mesoscopic physics provides the basic understanding behind the development of "quantum machines", machines that actively exploit the superposition principle and entanglement, rather than just using materials whose properties are passively and /a posteriori /explained by quantum mechanics.
There has been tremendous recent progress in this field. Four key topics we expect to be of particular interest are:
1. Electrons in disordered metallic mesoscopic systems.
2. Spins and charges in semiconductor quantum dots.
3. Quantum mechanics and quantum optics of superconducting
electrical circuits and nano-mechanical systems.
4. Quantum noise, amplification, detection, control and counting
statistics.
The workshop will focus on insights into particle physics and gauge theory dynamics from string theory. The proposed activities will concentrate on aspects of string vacua, both from the perspective of flux compactifications and D-brane gauge dynamics, as well as new insights into strong gauge dynamics from string theory. Given the recent progress and continued central interest in these research directions, we expect to have an exciting program. We also plan to keep the door open for any other exciting developments in string theory which may arise in the coming year and which touch on the themes of the current planned program.
Driven by both intellectual challenges and funding opportunities, there is now an unprecedented movement of physicists and physics departments into the biological arena. At the same time, there is also a fair bit of frustration among mainstream physicists due to the fact that in many cases, including even some of the Aspen workshops, physics appears to be taking the backseat, as an instrument in service of biology. In this meeting physicists will be working on PHYSICS of biological systems. It will be as broad as possible in terms of the biological subjects, but the common theme will be physics.
Some specific problems, which we hope to address, include (but are not limited to): Coulomb effects in molecular biological systems (protein-DNA in various combinations, collective behavior of large assemblies of strongly charged molecules and colloidal particles, structure of chromatin, structure and formation of viruses, etc); diffusion and transport in molecular biology (non-classical diffusion, active transport involving molecular motors, DNA translocation through the membrane pores, DNA reptation from the virus head, unzipping of dsDNA etc); statistical physics of macromolecules (bridging the insights of folding theory with the problems of evolution of proteins in both sequence space and in structure space, viral RNA as branched polymer, statistical mechanics models, involving coupled evolution in sequence and structure space of proteins, recently termed the "biological Big Bang"); self-organization (e.g., of virus particles in close relation to Coulomb effects and the statistical physics of macromolecules); ion channels (how Nature reduces the electrostatic barrier for ions crossing the membrane, the physics of selectivity of channel transport, etc).
There has been remarkable progress in the past few years developing new models of particle physics beyond the Standard Model and in developing innovative ways for testing these models in experiment. Much of the theoretical progress has been stimulated by more formal developments, leading to an increased collaboration and synergy between more formal and more phenomenological theorists. The goal of this workshop is to bridge the gap between theory and phenomenology by bringing together physicists with diverse expertise. We intend to bring together experts on the Standard Model (particularily collider phenomenologists), beyond the Standard Model (supersymmetry, extra dimensions), and string theorists with an interest in phenomenology. We expect that the collaborations fostered at this workshop would lead to new directions in model building, to studies of experimental signatures of new models, and to the development of new techniques for studying strongly coupled physics relevant for particle experiments.
For more information, please go to: http://wingate.uoregon.edu/Anticipation.html
Many of the most intriguing problems in solid and fluid mechanics involve systems in which key physical parameters are very large (or small), or in which unusual geometries constrain the behavior of systems in surprising ways. Thus, in granular systems the rigidity of the particles is in marked contrast to their softness at a macroscopic level. In some soft biological systems of recent physics interest, the macroscopic elastic properties are both non-linear and tunable in ways that can shed new light on solid/continuum mechanics. In fluid mechanics, free boundary problems such as drop snap-off and related phenomena combine familiar hydrodynamic phenomena in counter-intuitive (and often aesthetically pleasing) ways. This workshop will cover this timely subject, which can fairly be termed"extreme mechanics."
The past few years have seen interesting progress on a variety of fronts related to our understanding of black holes in string theory. Work on supertubes, black rings, non-singular geometries for microstates, small black holes, and connections to topological string theories, all pertain to the same basic problem, but these directions have not yet been well integrated since they are comparatively new. This workshop will bring together workers in these areas to exchange ideas, focus on the important open problems that may now be solvable, and identify new and promising avenues of research in the study of stringy black holes. We expect this to result not only in progress on black holes but also in our understanding of cosmology, nonperturbative string theory, and matter/gravity duality.