Macroscopic Physics Research Articles

Direct multiscale coupling of a transport code to gyrokinetic turbulence codes

Direct coupling between a transport solver and local, nonlinear gyrokinetic calculations using the multiscale gyrokinetic code TRINITY [M. Barnes, “TRINITY: A unified treatment of turbulence, transport, and heating in magnetized plasmas,” Ph.D. thesis, University of Maryland, 2008 (eprint arXiv:0901.2868)] is described. The coupling of the microscopic and macroscopic physics is done within the framework of multiscale gyrokinetic theory, of which we present the assumptions and key results. An assumption of scale separation in space and time allows for the simulation of turbulence in small regions of the space-time grid, which are embedded in a coarse grid on which the transport equations are implicitly evolved. This leads to a reduction in computational expense of several orders of magnitude, making first-principles simulations of the full fusion device volume over the confinement time feasible on current computing resources. Numerical results from TRINITY simulations are presented and compared with experimental data from JET [M. Keilhacker, Plasma Phys. Controlled Fusion 41, B1 (1999)] and ASDEX Upgrade [O. Gruber, Nucl. Fusion 47, S622 (2007)] plasmas.

Observing the spontaneous breakdown of unitarity

During the past decade, the experimental development of being able to create ever larger and heavier quantum superpositions has brought the discussion of the connection between microscopic quantum mechanics and macroscopic classical physics back to the forefront of physical research. Under equilibrium conditions this connection is in fact well understood in terms of the mechanism of spontaneous symmetry breaking, while the emergence of classical dynamics can be described within an ensemble averaged description in terms of decoherence. The remaining realm of individual-state quantum dynamics in the thermodynamic limit was addressed in a recent paper proposing that the unitarity of quantum mechanical time evolution in macroscopic objects may be susceptible to a spontaneous breakdown. Here we will discuss the implications of this theory of spontaneous unitarity breaking for the modern experiments involving truely macroscopic Schrödinger cat states.

First Demonstration of Collisionless Driven Reconnection in a Multi-Hierarchy Simulation

A multi-hierarchy simulation model for magnetic reconnection studies is developed in which macroscopic and microscopic physics are expressed consistently and simultaneously. We are the first to have successfully demonstrated collisionless driven reconnection in the framework of a multi-hierarchy model. Magnetic reconnection is found to occur in a micro-hierarchy upon plasma injection from a macro-hierarchy.

Feature article - Polymeric HVDC cable design and space charge accumulation. Part 2: insulation interfaces

The electric field distribution of cable insulation systems under HVDC can be affected significantly at interfaces due to space charge build-up. In this article, the second part of a three-article series, face and space charge accumulation are analyzed first in terms of macroscopic physics, then through approximate mathematical models that will be used to fit experimental data obtained for model cables having two insulation layers and constituting cylindrical interfaces.

Continuum mesoscopic framework for multiple interacting species and processes on multiple site types and/or crystallographic planes

While recently derived continuum mesoscopic equations successfully bridge the gap between microscopic and macroscopic physics, so far they have been derived only for simple lattice models. In this paper, general deterministic continuum mesoscopic equations are derived rigorously via nonequilibrium statistical mechanics to account for multiple interacting surface species and multiple processes on multiple site types and/or different crystallographic planes. Adsorption, desorption, reaction, and surface diffusion are modeled. It is demonstrated that contrary to conventional phenomenological continuum models, microscopic physics, such as the interaction potential, determines the final form of the mesoscopic equation. Models of single component diffusion and binary diffusion of interacting particles on single-type site lattice and of single component diffusion on complex microporous materials' lattices consisting of two types of sites are derived, as illustrations of the mesoscopic framework. Simplification of the diffusion mesoscopic model illustrates the relation to phenomenological models, such as the Fickian and Maxwell-Stefan transport models. It is demonstrated that the mesoscopic equations are in good agreement with lattice kinetic Monte Carlo simulations for several prototype examples studied.

Dynamic Rupture in a 3-D Particle-based Simulation of a Rough Planar Fault

An appreciation of the physical mechanisms which cause observed seismicity complexity is fundamental to the understanding of the temporal behaviour of faults and single slip events. Numerical simulation of fault slip can provide insights into fault processes by allowing exploration of parameter spaces which influence microscopic and macroscopic physics of processes which may lead towards an answer to those questions. Particle-based models such as the Lattice Solid Model have been used previously for the simulation of stick-slip dynamics of faults, although mainly in two dimensions. Recent increases in the power of computers and the ability to use the power of parallel computer systems have made it possible to extend particle-based fault simulations to three dimensions. In this paper a particle-based numerical model of a rough planar fault embedded between two elastic blocks in three dimensions is presented. A very simple friction law without any rate dependency and no spatial heterogeneity in the intrinsic coefficient of friction is used in the model. To simulate earthquake dynamics the model is sheared in a direction parallel to the fault plane with a constant velocity at the driving edges. Spontaneous slip occurs on the fault when the shear stress is large enough to overcome the frictional forces on the fault. Slip events with a wide range of event sizes are observed. Investigation of the temporal evolution and spatial distribution of slip during each event shows a high degree of variability between the events. In some of the larger events highly complex slip patterns are observed.

A New Graph Language for Representing the Macroscopic Formalism in Physicochemistry and Physics

A new way for representing algebraic equations used in macroscopic physics and physico-chemistry is proposed. Based on oriented graph built in accordance with the properties of energy in a system, it uses state variables as nodes and constitutive system properties as connections, together with space-time properties. The ordering introduced by topology reveals common structures between mechanics, electrodynamics, physico-chemistry and all domains in which energy is quantified. Among numerous interesting consequences, two new concepts, energetic path and energetic mode, shed interesting physical meaning on transfer processes: The energetic path conveys the nature, conserved and/or dissipated, of transferred energy in a process. The energetic mode depicts the proportion of conserved vs. dissipated energy. Semi- infinite transient diffusion appears as an equilibrated process conserving fifty percent and dissipating the other part of its energy, while fractal or anomalous diffusion, identified with a fractional exponent, can be seen as conserving the energy in the proportion given by this exponent.

Hydrophobic hydration from small to large lengthscales: Understanding and manipulating the crossover

Small and large hydrophobic solutes exhibit remarkably different hydration thermodynamics. Small solutes are accommodated in water with minor perturbations to water structure, and their hydration is captured accurately by theories that describe density fluctuations in pure water. In contrast, hydration of large solutes is accompanied by dewetting of their surfaces and requires a macroscopic thermodynamic description. A unified theoretical description of these lengthscale dependencies was presented by Lum, Chandler, and Weeks [(1999) J. Phys. Chem. B 103, 4570-4577]. Here, we use molecular simulations to study lengthscale-dependent hydrophobic hydration under various thermodynamic conditions. We show that the hydration of small and large solutes displays disparate dependencies on thermodynamic variables, including pressure, temperature, and additive concentration. Understanding these dependencies allows manipulation of the small-to-large crossover lengthscale, which is nanoscopic under ambient conditions. Specifically, applying hydrostatic tension or adding ethanol decreases the crossover length to molecular sizes, making it accessible to atomistic simulations. With detailed temperature-dependent studies, we further demonstrate that hydration thermodynamics changes gradually from entropic to enthalpic near the crossover. The nanoscopic lengthscale of the crossover and its sensitivity to thermodynamic variables imply that quantitative modeling of biomolecular self-assembly in aqueous solutions requires elements of both molecular and macroscopic hydration physics. We also show that the small-to-large crossover is directly related to the Egelstaff-Widom lengthscale, the product of surface tension and isothermal compressibility, which is another fundamental lengthscale in liquids.

Simplification d'images 3D de matériaux poreux en vue de leur caractérisation physique

ABSTRACT Predicting the physical properties of porous materials is difficult due to the complexity of the underlying microstructure that determines physics at the macroscopic scales of interest to the practitioner. The study of the relation between macroscopic physics and the microstructure can be largely facilitated if simplified and physically relevant representations of the microstructure are available. Herein, it is to reduce the structural complexity of a 3D digital image of an actual sample to the only rules describing the association of pore throat sizes and shapes to adjacent pores. Such rules, shown by a variety of independent approaches to govern the main part of flow and transport are measured by image analysis and expressed in the form of a pore network model. Relying on a random model of porous microstructures, the approach can be applied to isotropic porous materials whose observation by imagery is limited to 2D due to the small spatial resolution of the porosity.

Continuous quantum measurement and the quantum to classical transition

While ultimately they are described by quantum mechanics, macroscopic mechanical systems are nevertheless observed to follow the trajectories predicted by classical mechanics. Hence, in the regime defining macroscopic physics, the trajectories of the correct classical motion must emerge from quantum mechanics, a process referred to as the quantum to classical transition. Extending previous work [Bhattacharya, Habib, and Jacobs, Phys. Rev. Lett. 85, 4852 (2000)], here we elucidate this transition in some detail, showing that once the measurement processes that affect all macroscopic systems are taken into account, quantum mechanics indeed predicts the emergence of classical motion. We derive inequalities that describe the parameter regime in which classical motion is obtained, and provide numerical examples. We also demonstrate two further important properties of the classical limit: first, that multiple observers all agree on the motion of an object, and second, that classical statistical inference may be used to correctly track the classical motion.

Microscopic and Macroscopic Physics of Non-equilibrium Steady States Near and Far from Equilibrium

Microscopic and Macroscopic Physics of Non-equilibrium Steady States Near and Far from Equilibrium

Editor's Note: Relativistic Hydrodynamics

The general theory of relativity may be viewed as the completion of classical macroscopic field physics. Since this theory identifies gravitation with some aspects of the metric of spacetime, and because the metric and its connection enter all parts of physics as basic prerequisites, the task arose to adapt all branches of classical physics to the generalized spacetime structure, and to investigate whether the modifications lead to new, possibly observable consequences. This holds, in particular, for hydrodynamics, the significance of which in this context is enhanced by the following facts. Due to an elementary argument by Max von Laue [1], relativistic causality implies that any extended body has infinitely many degrees of freedom, and the results of Karl Schwarzschild [2] and of subsequent authors show that Einstein’s gravitational field equation is incompatible with the representation of bodies as points endowed with a positive mass. Therefore, in general relativity bodies such as stars and planets have to be modelled, at least in principle, in terms of hydroor elastomechanics. In addition, the development of high-energy astrophysics shows that large-scale flows of matter with relativistic speeds in relativistic gravitational fields do occur in nature. Prime examples are supernovae, jets associated with active galactic nuclei, accretion flows

Harry Lee Morrison

Harry Lee Morrison, a professor of physics at the University of California, Berkeley (UCB), for 22 years and an assistant dean of the College of Letters & Science, died following a heart attack on 14 January 2002 at his home in Berkeley.Born on 7 October 1932 in Arlington, Virginia, Morrison attended the Catholic University of America in Washington, DC, from which he received a BA in chemistry in 1955 and a PhD in chemistry 1960. His thesis, “Theoretical Investigation of Linear H3“ was prepared under the guidance of his adviser, Virginia Griffing, one of the few women in the US at that time to hold a senior faculty position in the sciences.In 1961, Morrison was called to active military service as a first lieutenant at the US Air Force Academy. As an assistant professor, he taught physics there until 1964, when he joined the staff of the Lawrence Livermore National Laboratory (LLNL) as a theoretical physicist, and worked on quantum fluids and statistical physics. He applied his knowledge to a direct derivation of the Landau theory of quantum hydrodynamics and interacting Bose systems. The UCB physics department added Morrison to its ranks as an associate professor in 1972; he became a full professor in 1977.Morrison chose a research area that was not particularly popular but was profound and fundamental: statistical mechanics and the many-body problem. He focused on the relationship between microscopic physics and macroscopic physics. In particular, he concentrated on the theory of superfluid helium, to which he devoted most of his research life. He was especially interested in the phenomenon of spontaneous symmetry breaking in superfluid helium. Morrison was fascinated by the deep connection between mathematics on the one hand, which seems to have nothing to do with the real world, and physics on the other hand, which does. He approached his research with a passionate curiosity that was contagious to his students and colleagues. He had deep physical insights into the meaning of mathematical structures and made explicit the many hidden connections between physics and mathematics.Perhaps his best-known contribution to physics was his 1972 demonstration of the absence of long-range order in quantum systems in two dimensions, such as in thin superfluid helium films, that resulted from the breaking of a continuous symmetry. He did this work in collaboration with John Garrison and Jack Wong, both of LLNL; it was one of the most successful applications of algebraic quantum field theory to the analysis of physical systems. Their analysis put the earlier work of Pierre Hohenberg, N. David Mermin, and Hermann-Friedrich Wagner for 2D phase transitions on a firm mathematical footing.During the late 1970s, Morrison applied the theory of current algebra, developed earlier by Roger Dashen and David Sharp for elementary particle physics, to the geometry of macroscopic quantum flows in superfluid helium. With his postdoc, James Lindesay, and student, Uwe Albertin, he showed that the excitations of the superfluid naturally divided into two types, a longitudinal type corresponding to quasiparticles associated with quantized sound waves and a transverse type corresponding to pseudoparticles associated with vortices, tiny quantum whirlpools in the superfluid. Morrison thus established a deep connection between microscopic and macroscopic physics. In 1970, Morrison helped to found the Mathematics, Engineering, Science Achievement (MESA) program, which was created to boost minority undergraduate enrollment in science and engineering in the US. He also was one of the founding members (in 1973) of the National Society of Black Physicists and one of the first members to obtain the status of fellow in that organization. During the 1970s, Morrison served as a visiting professor at the University of Colorado, Howard University in Washington, DC, and MIT.In 1985, Morrison was appointed as assistant dean of the College of Letters & Science. He retired from the UCB faculty in 1994, but continued to serve as an assistant dean in the College of Letters & Science for 11 more years.Morrison was devoted to his family, the practice of theoretical physics, the development of scientific talent in the African American community, and the life of an intellectual. He strongly encouraged minorities and women to pursue math-based majors as undergraduates at UCB. He also contributed greatly to the physics department through his scientific achievements, leadership, and personal warmth.Harry Lee MorrisonU. OF CALIFORNIA, BERKELEYPPT|High resolution© 2002 American Institute of Physics.

Superfluid3HeJosephson weak links

Josephson weak links between samples of macroscopic quantum systems such as superconductors, superfluids, and Bose-Einstein condensates provide a unique tool with which to explore quantum mechanics and an opportunity to create applications based on macroscopic quantum physics. In this review we describe the development of the field of weak links in superfluid ${}^{3}\mathrm{He}.$ We review the basic techniques used to study this system and then describe the experimental and theoretical milestones that have led to our present understanding.

Purely perturbative Boltzmann equation for hot non-Abelian gauge theories

In the perturbation theory, trasnport phenomena in hot non-Abelian gauge theories like QCD are often plagued with infrared singularities or nonperturbative effects. We show, in the context of the Kadanoff & Baym formalism, that there are certain nonequilibrium processes which are free from such difficulties. For these processes, due to an interplay between the macroscopic and microscopic physics, characteristic time scale (the mesoscale) naturally enters as an infrared cutoff and purely perturbative description by the Boltzmann equation is valid.

On the ability of a class of random models to portray the structural features of real, observed, porous media in relation to fluid flow

The description of transport processes is practically accomplished at the macroscopic scale compatible with our ability to observe, and measure processes. The macroscopic description requires to faithfully account for the effects of the detailed inter-phase boundaries on the microscopic level (the micro-structure) in the expression for macroscopic transport coefficients such as permeability. Herein, the porous descriptors held to express macroscopic coefficients are the porosity and the autocorrelation function (ACF) measured directly on a 2-D finite digital image of the porous material. The flow-relevance of the selected porous descriptors will be eventually demonstrated if synthetic porous media generated through a random model from measured porosity and ACF yield the same transport properties than the actual media. Towards that goal, synthetic 2-D numerical porous micro-structures are generated from measured porosity and ACF on two types of natural mechanical aggregates: an Upper Shoreface and a Tidal Channel Sandstone. The achieved synthetic porous media are shown to include all the geometrical features of the real, observed, natural aggregates. Such agreement between synthetic and actual media is demonstrated to be the consequence of: (1) the richness of the structural information carried out by the ACF and, (2) a structural noise produced by the “practical use” of the random model. The requirement to account for the impact on macroscopic physics of this structural noise is emphasized. Extension of the approach to artificial aggregates such as cement, mortars or concrete is shown to be a promising avenue.

PHYSICAL-SCIENCE KNOWLEDGE AND PATTERNS OF ACHIEVEMENT AT THE PRIMARY-SECONDARY INTERFACE PART 1. GENERAL STUDENT POPULATION

In primary Greek schools, physics and chemistry are part of the integrated science programme which is taught in the final two grades, fifth and sixth. Nine hundred and seventy-six seventh and eighth-grade students (age 11.5-13.5), from nine urban and semi-urban Greek lower secondary schools, each answered one out of three similar tests, in an investigation of basic physics and chemistry knowledge and patterns of student achievement at the primary-secondary interface. The mean overall achievement in all three tests (17.2% for the seventh and 21.5% for the eighth grade) was low. The older students achieved higher than the younger ones in all three tests. This is surprising given that the knowledge tested was taught in fifth and sixth grades, and was less immediate for the eighth-grade students. Achievement on macroscopic physics topics was higher than macroscopic chemistry topics. Submicroscopic topics (referring to corpuscular matter) proved much more difficult than macroscopic topics. As expected critical-thinking questions were much harder than questions demanding simple recall or recognition of knowledge. In all cases, boys achieved higher than girls; however, there was a drop in the gender gap from the seventh to the eighth grade. The implications of the findings are discussed. [Chem. Educ. Res. Pract. Eur.: 2001, 2, 241-252]

Cosmological Singularity and the Creation of the Universe

One of the most important and most frequently discussed theological problems related to cosmology is the creation problem. Unfortunately, it is usually considered in a context of a rather simplistic understanding of the initial singularity (often referred to as the Big Bang). This review of the initial singularity problem considers its evolution in twentieth‐century cosmology and develops methodological rules of its theological (and philosophical) interpretations. The recent work on the “noncommutative structure of singularities” suggests that on the fundamental level (below the Planck's scale) the concepts of space, time, and localization are meaningless and that there is no distinction between singular and nonsingular states of the universe. In spite of the fact that at this level there is no time, one can meaningfully speak about dynamics, albeit in a generalized sense. Space, time, and singularities appear only in the transition process to the macroscopic physics. This idea, explored here in more detail, clearly favors an atemporal understanding of creation.

Radiative phonon polaritons in semiconductor double heterostructures: A continuum approach

A recently reported continuum approach, based on the laws of macroscopic physics, is applied to a calculation of the virtual oscillatory modes of radiative phonon polaritons in the case of a semiconductor double heterostructure of nanometric scale. The obtained results are in the form of TE and TM waves propagating along the structure. We take advantage of the general formulation already presented in a previous paper [Phys. Rev. B 56, 4115 (1997)] in order to display the analytical expressions for the phonon mechanical displacement field $\stackrel{\ensuremath{\rightarrow}}{u}$ and the associated electromagnetic fields $\stackrel{\ensuremath{\rightarrow}}{E}$ and $\stackrel{\ensuremath{\rightarrow}}{B},$ as well as the different dispersion relations of the modes. In this treatment a full account is taken of the electromechanical character of the oscillations, and the matching problem is consistently applied. We also calculate the optical coefficients (reflection, absorption, and transmission) for the incident ir radiation field. A detailed discussion of the results is made, including comparisons with earlier works on the same subject.

The extension of classical dynamics for unstable Hamiltonian systems

Classical dynamics can be formulated in terms of trajectories or in terms of statistical ensembles whose time evolution is described by the Liouville equation. It is shown that for the class of large nonintegrable Poincaré systems (LPS), the two descriptions are not equivalent. Practically all dynamical systems studied in statistical mechanics belong to this class. The basic step is the extension of the Liouville operator L H outside the Hilbert space to functions singular in their Fourier transformation. This function space plays an important role in statistical mechanics as functions of the Hamiltonian, and therefore equilibrium distribution functions belong to this class. Physically, these functions correspond to situations characterized by “persistent interactions” as they are realized in macroscopic physics. Persistent interactions are introduced in contrast to “transient interactions” studied in quantum mechanics by the S-matrix approach (asymptotically free in and out states). The eigenvalue problem for the Liouville operator L H is solved in this generalized function space for LPS. We obtain a complex, irreducible spectral representation. Complex means that the eigenvalues are complex numbers, whose imaginary parts refer to the various irreversible processes such as relaxation times, diffusion.… Irreducible means that these representations cannot be implemented by trajectory theory. As the result, the dynamical group of evolution splits into two semigroups. Moreover, the laws of classical dynamics take a new form as they have to be formulated on the statistical level. They express “possibilities” and no more “certitudes”. Two examples of typical classical systems, i.e., interacting particles and anharmonic lattices are studied.