Longitudinal variations, the opposition effect and monochromatic albedos for Mars

Magnitude at zero phase, phase coefficient, and monochromatic albedo computed for Mars as function of wavelengt

Truncated unity functional renormalization group for multiband systems with spin-orbit coupling

Although the functional renormalization group (fRG) is by now a well-established method for investigating correlated electron systems, it is still undergoing significant technical and conceptual improvements. In particular, the motivation to optimally exploit the parallelism of modern computing platforms has recently led to the development of the "truncated-unity" functional renormalization group (TU-fRG). Here, we review this fRG variant, and we provide its extension to multiband systems with spin-orbit coupling. Furthermore, we discuss some aspects of the implementation and outline opportunities and challenges ahead for predicting the ground-state ordering and emergent energy scales for a wide class of quantum materials.Comment: consistent with published version in Frontiers in Physics (2018

Using molecular mechanics to predict bulk material properties of fibronectin fibers

The structural proteins of the extracellular matrix (ECM) form fibers with finely tuned mechanical properties matched to the time scales of cell traction forces. Several proteins such as fibronectin (Fn) and fibrin undergo molecular conformational changes that extend the proteins and are believed to be a major contributor to the extensibility of bulk fibers. The dynamics of these conformational changes have been thoroughly explored since the advent of single molecule force spectroscopy and molecular dynamics simulations but remarkably, these data have not been rigorously applied to the understanding of the time dependent mechanics of bulk ECM fibers. Using measurements of protein density within fibers, we have examined the influence of dynamic molecular conformational changes and the intermolecular arrangement of Fn within fibers on the bulk mechanical properties of Fn fibers. Fibers were simulated as molecular strands with architectures that promote either equal or disparate molecular loading under conditions of constant extension rate. Measurements of protein concentration within micron scale fibers using deep ultraviolet transmission microscopy allowed the simulations to be scaled appropriately for comparison to in vitro measurements of fiber mechanics as well as providing estimates of fiber porosity and water content, suggesting Fn fibers are approximately 75% solute. Comparing the properties predicted by single molecule measurements to in vitro measurements of Fn fibers showed that domain unfolding is sufficient to predict the high extensibility and nonlinear stiffness of Fn fibers with surprising accuracy, with disparately loaded fibers providing the best fit to experiment. This work shows the promise of this microstructural modeling approach for understanding Fn fiber properties, which is generally applicable to other ECM fibers, and could be further expanded to tissue scale by incorporating these simulated fibers into three dimensional network models

Truncated-Unity Parquet Equations: Application to the Repulsive Hubbard Model

The parquet equations are a self-consistent set of equations for the effective two-particle vertex of an interacting many-fermion system. The application of these equations to bulk models is, however, demanding due to the complex emergent momentum and frequency structure of the vertex. Here, we show how a channel-decomposition by means of truncated unities, which was developed in the context of the functional renormalization group to efficiently treat the momentum dependence, can be transferred to the parquet equations. This leads to a significantly reduced numerical effort scaling only linearly with the number of discrete momenta. We apply this technique to the half-filled repulsive Hubbard model on the square lattice and present approximate solutions for the channel-projected vertices and the full reducible vertex.Comment: Consistent with published version in Phys. Rev.

The MAHB, the Culture Gap, and Some Really Inconvenient Truths

Humanity's failure to take adequate actions to stem a likely environmental collapse calls for extraordinary measures to understand and alter human behavior, argues Paul Ehrlich. His Millennium Assessment of Human Behavior (MAHB) aims to chart the path to a sustainable future

The process of irreversible nucleation in multilayer growth. II. Exact results in one and two dimensions

We study irreversible dimer nucleation on top of terraces during epitaxial growth in one and two dimensions, for all values of the step-edge barrier. The problem is solved exactly by transforming it into a first passage problem for a random walker in a higher-dimensional space. The spatial distribution of nucleation events is shown to differ markedly from the mean-field estimate except in the limit of very weak step-edge barriers. The nucleation rate is computed exactly, including numerical prefactors.Comment: 22 pages, 10 figures. To appear in Phys. Rev.

Lattice Effects in Crystal Evaporation

We study the dynamics of a stepped crystal surface during evaporation, using the classical model of Burton, Cabrera and Frank, in which the dynamics of the surface is represented as a motion of parallel, monoatomic steps. The validity of the continuum approximation treated by Frank is checked against numerical calculations and simple, qualitative arguments. The continuum approximation is found to suffer from limitations related, in particular, to the existence of angular points. These limitations are often related to an adatom detachment rate of adatoms which is higher on the lower side of each step than on the upper side ("Schwoebel effect").Comment: DRFMC/SPSMS/MDN, Centre d'Etudes Nucleaires de Grenoble, 25 pages, LaTex, revtex style. 8 Figures, available upon request, report# UBFF30119

Gravitational Waves: Just Plane Symmetry

We present some remarkable properties of the symmetry group for gravitational plane waves. Our main observation is that metrics with plane wave symmetry satisfy every system of generally covariant vacuum field equations except the Einstein equations. The proof uses the homothety admitted by metrics with plane wave symmetry and the scaling behavior of generally covariant field equations. We also discuss a mini-superspace description of spacetimes with plane wave symmetry.Comment: 10 pages, TeX, uses IOP style file

Book Reviews

Book 1 Book Title: Basic EpidemiologyBook Authors: R. Beaglehole, R. Bonita & T. KjellströmPp. viii + 174. (in English, French and Spanish in preparation). $19,40. Geneva: WHO. 1993. Order No. 1150395. ISBN 92-4-154446-5.Book 2Book Title: A Pocket Book of Social and Community PaediatricsBook Author: Jo SibertPp. viii + 164. London: Edward Arnold. 1992. ISBN 0-340-54929-7.Book 3Book Title: Knowledge Beats CancerBook Author: Albert Stegmann AlbertsPp. 226. Illustrated. R55,45. Pretoria: Haum Tertiary. 1993. ISBN 0-7986-3196-1.Book 4Book Title: AIDS and Your ResponsePp. vi + 226. R49,50. ISBN 0-620-17319-X.Book 5Book Title: Principles for Evaluating Chemical Effects on the Aged Population. Enviromnental Health Criteria. No. 144Book Author: W.H.O.Pp. 159. (English only).$20,50. Geneva: WHO. 1993. Order No. 1160144. ISBN 92-4-1571446.Book 6Book Title: The Guide to Heart Sounds: Normal and AbnormalBook Authors: Donald W. Novey, Marcia Pencak & John M. StangAudio-cassette narrated by: Donald W. Novey. pp. xi + 74. Illustrated. Florida: CRC Press. 1988. ISB J 0-8493-0153X.Book 7Book Title: Propachlor. Enviromnental Health Criteria. No. 147Book Author: W.H.O.Pp. 110. (English, French and Spanish summaries). $17,30. Geneva: WHO. 1993. Order TO. 1160147. ISBN 92-4-157147-0.Book 8Book Title: Quality Assurance in Health Care: A HandbookBook Authors: Roger Ellis & Dorothy WhittingronLondon: Edward Arnold. 1993. ISBN 0-340-55273-5.Book 9Book Title:  Rehabilitation after Cardiovascular Diseases, with Special Emphasis on Developing CountriesReport of a WHO expert committee. Technical Report Series No 831. Pp. viii + 122 (available in English, French and Spanish in preparation). Geneva: WHO. 1993. ISBN 92-4-120831-7

Rigid Singularity Theorem in Globally Hyperbolic Spacetimes

We show the rigid singularity theorem, that is, a globally hyperbolic spacetime satisfying the strong energy condition and containing past trapped sets, either is timelike geodesically incomplete or splits isometrically as space $\times$ time. This result is related to Yau's Lorentzian splitting conjecture.Comment: 3 pages, uses revtex.sty, to appear in Physical Review