The founders of thermodynamics in the 19th century did not find it easy at all to make themselves heard by the scientific community of the day. And it did not help that they themselves did not grasp fully what they had found. That situation provided ample opportunity for misunderstanding which to us, now, in the 21st century, is quite amusing.
At the same time the pioneers of thermodynamics – however imperfect the understanding of their discoveries was – revolutionized science by the discovery of energy and entropy, the dichotomy of natural forces, of which the first one is deterministic and the second one random. They revolutionized everyday life by utilizing energy and by creating methods for the production of fuel. And they rendered traditional philosophy redundant.
References:
I.Müller, W.Weiss, Entropy and Energy – a Universal Competition. Springer Verlag, Heidelberg (2005)
I.Müller, A History of Thermodynamics – the Doctrine of Energy and Entropy. Springer Verlag, Heidelberg (2007)

Learning, plasticity, adaptivity: these occur at the ecological, behavioural, neural and molecular levels amongst others. Yet each level is just a different description of the the same processes. Defined structural relations exist between the levels (networks within networks), and these define causal relations in time.
I will describe how these causal relations are essentially inter-level in nature, consisting of downward 'boundary conditions' and upward 'emergence'. Using them, information can travel from the top to the bottom of the reductionist hierarchy and vice-versa. This opens the possibility of defining new kinds of learning algorithm which exploit inter-level mappings for representational purposes. My main concern is to understand the plasticity of the neuron-to-synapse mapping and thus explain Spike Timing-Dependent synaptic Plasticity (STDP), but I will also present cross-scale observations of the EEG in which cross-frequency phase-amplitude couplings also point towards global networks establishing constraints for local ones, which can then, through emergence, change global activity patterns and behaviour.

The topology of an extended (i.e. non-molecular) crystal structure is conveniently given as a periodic, connected, simple graph ("net"). Of the infinity of such structures only a small finite subset are of special interest in crystal chemistry. Most of these nets admit an infinity of tilings that carry the net, but it will be shown that usually there is just one "natural" tiling. These provide a basis for a taxonomy of nets which in turn provides a rational system for crystal design. Properties of some special nets such as the five regular nets and the seven minimal nets will be described. The use of combinatorial tiling theory to generate "interesting" nets will be mentioned, and some examples of their usefulness in crystal design adduced.

Mathematically exact equations of change in moments of the velocity distribution function readily follow from a Boltzmann-type kinetic equation. The direct use of enlarged subsets of these equations, each corresponding to one of the macroscopic variables to be retained, produces extended MHD models. The first relevant level of closure provides “ten moment” equations in the density ρ, velocity v, scalar pressure p, and the traceless component of the pressure tensor t. The next “thirteen moment” level also includes the thermal flux vector q, and further extended MHD models could be developed by including even higher level basic equations of change. Explicit invariant forms for the tensor t and the heat flux vector defining q follow from their respective basic equations of change. Except in the neighbourhood of a magnetic null, in magnetised plasma these forms may be resolved into known sums of their parallel, cross (or transverse) and perpendicular components. Parallel viscosity and heat flux in an electron-ion plasma are specifically discussed.

The study of stochastic resonance is associated with many fields of physics, meteorology, chemistry, and biology. The rising interest in this phenomenon stems from the counter-intuitive effect that a periodic signal component can be amplified in a non-linear system when subjected to a stochastic forcing. In systems showing intermittency with weak periodic forcing a similar amplification effect is known as noise-free stochastic resonance.
In this talk I will introduce the phenomenon of stochastic resonance and then report on noise-free stochastic resonance in autonomous electronic circuits showing the crisis-induced intermittency. This intermittency results from the merging of two symmetric mono-scroll attractors. Above a critical control parameter value the dynamics is governed by fast oscillations on the sub-attractors and a slow jumping dynamics between them. It will be shown that close to such a crisis small periodic and aperiodic signals can be enhanced by synchronizing the intermittent jumping with the modulation, which can be achieved through variation of the control parameter. In the particular system several maxima of enhancement can be found, which means the occurrence of stochastic multi-resonance.
The experimental data is used to analyze the equivalence and cooperation of stochastic and deterministic chaotic dynamics in stochastic resonance related phenomena. I will address the following key questions: (i) To what extent is the impact of stochastic and chaotic dynamics equivalent? (ii) Can we extend theoretical concept of conventional stochastic resonance to model noise-free and stochastic multi-resonance? (iii) Is there a general mechanism leading to multi-resonance in stochastic and noise-free systems?

 

Heat conduction is an old yet important problem. Since Fourier introduced the law bearing his name two hundred years ago, a first-principle derivation of this law from statistical mechanics is still lacking. Worse still, the validity of this law in low dimensions, and the necessary and sufficient conditions for its validity are still far from clear. In this talk I'll review recent works done on this subject. I'll also report our latest work on asymmetric heat conduction.  The study of heat conduction is not only of theoretical interest but also of practical interest. It'll shed light on the thermal properties of carbon nanotubes. The study of electric current has led to the invention of electric diodes and transistors. The study of heat conduction may also lead to the invention of thermal diodes and transistors in the future.

In the last years the study of many complex systems has taken strong advantage of the development of mathematical methods from the theory of nonlinear dynamical systems. Furthermore, for systems who show "turbulent" behaviour like fluids, the concept of coherent structures, i.e. strongly persistent spatio-temporal structures, has provided an efficient descriptive tool as well as the possibility of lower dimensional representation. A successful technique to find coherent structures is Proper Othogonal Decomposition (POD) and in connection with Galerkin methods can also be the technique leading to useful low-dimensional ODE approximations of PDE models, allowing to take full advantage of dynamical systems theory. The methodology has been used to characterize the transitions to periodic and quasi-periodic behaviour in two-dimensional Navier-Stokes equations, obtaining good reduction results.

 

Thursday, 16 November, 11:00am

"Slow Dynamics via Degenerate Variational Asymptotics"

Dr Georg Gottwald
Lecturer, School of Mathematics & Statistics, University of Sydney

Abstract

 

Friday, 10 November, 11:00am

"Structural Stability of Equilibrium and Confinement Transitions in Plasmas"

Dr Emilia R Solano
Research Physicist, Theory Group
Laboratorio Nacional de Fusion, CIEMAT, Madrid, Spain

Abstract

 

Thursday, 5 October, 11:00am

"Wanted:  A Theory of Model Coupling"

Dr Jay Larson
ANU Supercomputer Facility
ANU

Abstract

 

Thursday, 21 September, 11:00am

"Black Holes, Jets and their Interaction with the Interstellar Medium"

Dr Geoff Bicknell
Research School of Astronomy and Astrophysics
ANU

Abstract

A great deal of the physics of extragalactic radio-emitting jets has been deduced from simulations of jets propagating through homogeneous interstellar media. Nevertheless, the synthetic radio images from such simulations have been frustratingly unrealistic. Over the last few years, Ralph Sutherland and I have conducted simulations of jets in inhomogeneous media, initially with a view to understanding the way in which the jet momentum could be tapped to produce emission lines. The initial 2D work (in collaboration with Curtis Saxton) produced some interesting morphologies and informed us about the way in which the filling factor of the inhomogeneous medium affected the morphology of the radio source. However the most recent synthetic radio images produced by well-resolved three dimensional simulations are more realistic and lead us to conclude that certain morphological features of extragalactic radio sources give us pointers to the history of the radio galaxy. Moreover, they also inform us about the production of extended X-ray emission from powerful radio galaxies such as the famous radio source Cygnus A.

 

Wednesday, 2 August, 11:00am

"Complex Systems Approaches to Space and Fusion Confinement Plasmas"

Prof Sandra Chapman
Head of the Space and Astrophysics Group,
Centre for Fusion, Space and Astrophysics
University of Warwick, United Kingdom

Abstract

The earth’s dynamic magnetosphere is a candidate complex system in that plasma transport occurs via intermittent events that exhibit scaling, with energy release occurring on a wide range of scales up to the system size. Along with this anomalous transport, a further point of contact with laboratory plasmas is that the magnetosphere is a driven, finite sized, confined plasma. A topical paradigm for understanding this anomalous plasma transport in both astrophysical and laboratory confinement plasmas is that of ‘‘sandpile’’ models that dissipate energy by means of avalanches. We have generalized the original self-organized criticality (SOC) avalanche model of Bak, Tang, and Wiesenfeld to include spatially extended ‘fluid- like’ redistribution. The model possesses essentially two regimes of behavior. If the scale of this ‘fluid- like’ transport is of the order of the system size, the system is in the vicinity of a fixed point; in consequence the statistics of energy dissipation and length of avalanches are power law, and the time evolution is intermittent. If this scale is significantly smaller than the system size, the time evolution is quasi regular and follows a limit cycle. The first of these regimes appears relevant to the earth’s magnetosphere, where intermittent, bursty transport and large scale reconfiguration (substorms) are observed. In this case the avalanche statistics and anomalous scaling properties are inferred from observations of patches of intensity in POLAR UVI images of the aurora, and in fluctuations in the long (tens of years) timeseries of geomagnetic indices that are derived from magnetometer measurements beneath the auroral oval; which may map to energy dissipation events in the magnetotail. The second regime displays significant links to the observed confinement phenomenology of magnetic fusion plasmas, corresponding to a broader range of model parameter space. For example, there is correlation between sandpile profiles, stored energy, and edge steepening on the one hand, and the control parameter on the other. The predictions of the model, and comparison with these data will be presented.

We then compare two simple models- that of a system in an SOC state, and the Edwards Wilkinson (EW) model for interface growth, to underline the importance of robustness in these statistical signatures with respect to variability in the drive, and of bursty transport as opposed to intermittent structures, as key signatures of nonlinear complex avalanching systems. Power law statistics of bursty events do not necessarily require an underlying nonlinearity.

 

Wednesday, 2 August, 2:00pm

"Modelling the Noah and Joseph Effects in Space Plasma Time Series using Fractional Lévy Motion"

Dr Nicholas Watkins
Project Leader, Natural Complexity Project,
British Antarctic Survey

Abstract

In the 1960s Mandelbrot developed the use of fractals to describe how the shape of many aspects of the natural world depart from the Euclidean. In particular he proposed two kinds of fractal model to capture the way in which natural data is often persistent in time (his ``Joseph effect", common in hydrology and modelled by fractional Brownian motion) and/or prone to heavy tailed jumps (the "Noah effect", typical of economic index time series and modelled by Lévy flights). Both effects are by now well known in measures drawn from the Earth's aurora and also the solar wind which is its ultimate energy source, but modelling them has tended to emphasise one or other of the Noah and Joseph parameters (the tail exponent μ and the temporal exponent β respectively) at the other's expense. This talk will describe recent work (Watkins et al, Space Science Reviews 121, 271 (2005)) with Dan Credgington and co-workers at BAS and Warwick, in which we have applied Mandelbrot's unifying framework of fractional Lévy motion (fLm) to model such data. I will argue that we have resolved some apparent contradictions in earlier papers, where retrospectively one can see that pure Joseph or Noah descriptions had been sought.

Such ``ambivalent" behaviour (in the coinage of [Brockmann et al, Nature 439, 462 (2006)]) is highly topical and usually studied in the paradigm of fractional kinetics and the continuous time random walk (CTRW) rather than fLm. I will say a little about the (to me) surprising and intriguing fact that the scaling extracted from the CTRW differs from that seen in fLm, being a ratio of μ and β rather than an additive function. I will also touch on the use of fLm generator and simple analytic scaling arguments to study the problem of the area between a fractional Lévy curve and a threshold-directly related to the ``burst size" measure introduced by Takalo and Consolini in space physics and studied by Freeman et al [GRL 27, 1367 (2000); PRE 62, 8794 (2000)].

 

Thursday, 20 July, 4:00pm

"Quantitative Modelling of Multiscale Brain Activity"

Prof Peter Robinson
School of Physics
University of Sydney

Abstract

The electrical activity of the brain has been observed for over a century and is widely used to probe brain function and disorders, chiefly through the electroencephalogram (EEG) recorded by electrodes on the scalp. Indirect probes like functional MRI measure activity via its metabolic effects. However, the connections between physiology and measurements have been chiefly qualitative until recently, and most uses of the EEG and fMRI have been based on phenomenological correlations. A quantitative mean-field model of brain electrical activity is described that spans the range of physiological and anatomical scales from microscopic synapses to the whole brain. Its parameters measure quantities such as synaptic strengths, signal delays, cellular time constants, and neural ranges, and are all constrained by independent physiological measurements. Application of standard techniques from wave physics allows successful predictions to be made of a wide range of EEG and fMRI phenomena, including time series, spectra, evoked responses to stimuli and during stimulus processing, correlation properties, seizure dynamics, and measurement effects. Fitting to experimental data also enables physiological parameters to be inferred, giving a new noninvasive window into brain function.

Thursday, 6 July, 11:00am

"Exact Statistical Mechanics and Quantum Mechanics"

Dr Robert Niven
School of Aerospace, Civil and Mechanical Engineering
UNSW@ADFA

Abstract

This seminar examines the main philosophical bases of the entropy concept, in particular: (i) the information-theoretic definition of Szilard and others, in terms of "bits" of information; (ii) the axiomatic definition of Shannon; and (iii) the combinatorial definition, first given by Boltzmann. It is shown that the combinatorial approach is the most fundamental (most primitive) basis of entropy, and provides the means to analyse systems which cannot be examined by the Shannon entropy or Kullback-Leibler cross-entropy measures.
The combinatorial basis is then used to derive the "exact" forms of the Maxwell-Boltzmann (MB), Bose-Einstein (BE) and Fermi-Dirac (FD) entropy functions, without Stirling's approximation; i.e. for systems containing a finite number of entities, N. It is shown that to learn that a boson or fermion is a single particle (N=1) requires the input of information or energy, and so its observation is thermodynamically irreversible. This provides the beginnings of a rational interpretation of the “collapse of the wavefunction” in quantum mechanics, and of the need to destroy a boson or fermion in order to observe it. The new theory has profound implications for quantum mechanics and quantum computing.

Thursday, 2 March, 11:00am

"A brief illustrated history of bushfire research and where to from here?"

Mr Andrew Sullivan
Department of Theoretical Physics and CSIRO

Abstract

Bushfire behaviour research in Australia began in earnest in the late 1950s, driven by the immediate needs of the forestry industry to understand and control forest fires. The research had a hands-on, field-based, approach and produced prediction systems that provided quick practical estimates of likely fire behaviour for a given range of environmental conditions. The systems produced in the mid-1960s are largely still in use today by rural fire authorities, with improvements made over the years. This talk will discuss the phenomenon of bushfires in Australia, detail some of the research that has been done to date and explore some of the critical questions of fire behaviour, as illustrated by recent catastrophic events, that remain unanswered.

Monday, 20 February, 2:00pm

"Magnetic Reconnection"

Dr Daniela Grasso
Burning Plasma Research Group
Politecnico di Torino, Italy

Abstract

The process of magnetic field line reconnection is at the heart of many events in our solar system (solar flares) and in laboratory plasma (sawtooth crashes). High temperature plasmas, such as the ones in the solar corona or in the present-day tokamak experiments, are characterised by very low value of the resistivity. Under these conditions the motion of the magnetic field lines is frozen into the plasma motion, but for those regions, close to nulls of the magnetic field, where resistivity, or other effects, can play a role. In these regions the motion of the magnetic field lines is allowed to decouple from the plasma motion. Magnetic field lines can tear and reconnect changing their topology. Here we give a description of this phenomena on the basis of the MagnetoHydroDynamic (MHD) model and illustrate the typical problems related to this process.

 

Tuesday 24 January,11:00am

"Global Kinetic Ballooning Modes"

Dr Rajaraman Ganesh
Institute for Plasma Research, Bhat, Gandhinagar,
INDIA

Abstract

It is well-known that pressure-gradient-driven high-n ideal MHD Ballooning Modes (BM) limit β values in a tokamak operation. When magnetic shear is finite, Standard Ballooning Formalism (SBF) [1] is used to describe these short perpendicular wavelength modes, which are known to be stabilised by negative shear [2]. In the limit of zero shear, where SBF is known to fail [3], low-n ballooning modes called Infernal Modes [4] were numerically identified using a global MHD formalism.

Present-day tokamaks routinely attain large temperature values and strong spatial gradients which tend to kinetically decouple magnetic field lines and the plasma fluid (defreeze). Kinetic processes such as Landau damping (finite parallel E-field), finite Larmor radius, transit/trapped particle drift dynamics and their resonances then become important. Using a global linear gyrokinetic model, we identify two new global branches of BMs namely low-n Kinetic Ballooning Modes and Kinetic Infernal Modes [5].  In this talk, various elements of the model and the results obtained will be discussed.

 

2005 SEMINAR ABSTRACTS

Friday, 16 December, 11:00am

"Ergodic pumping: a mechanism to drive biomolecular conformation change"

Professor Robert MacKay, FRS
Director of Mathematical Interdisciplinary Research
Mathematics Institute
University of Warwick, UK

Abstract

Biomolecular machines are complex open systems par excellence. Many of them turn the free energy of hydrolysis of ATP into useful functions, like shortening muscle, advancing a transcription bubble along DNA, and pumping ions across membranes. Yet how can free energy decreases get turned into anything useful in an unconscious thermal bath of biomolecules? It is proposed that a significant contribution to the power stroke of myosin and some conformation changes in other biomolecules is the osmotic pressure of a single molecule (e.g. a phosphate ion) expanding a trap. Necessary conditions to achieve this efficiently are given, and the elements of a mathematical justification. It is proposed as a design principle for nanobiotechnology. Joint work with D.J.C. MacKay.

 

Thursday, 15 December, 11:00am

"Examples of how mathematics can be useful (even essential) for understanding complex systems (closed and open)"

Professor Robert MacKay, FRS
Director of Mathematical Interdisciplinary Research
Mathematics Institute
University of Warwick, UK

Abstract

I will present four examples, from my own and others' work, to demonstrate that mathematics is useful and essential for understanding complex systems, both closed and open:

• Adding new road capacity can increase travel time for everyone;
• Self-sustaining clusters can emerge even when it appears death rate exceeds reproduction;
• Everlasting self-localised excitations can occur even when linear theory would suggest they would radiate away, and media which are insulating for linear theory can be conducting nonlinearly;
• Indecomposable spatially extended deterministic systems (as well as stochastic ones) can exhibit non-unique probabilistic behaviour and sensitivity to boundary conditions.

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Wednesday, 7 December, 11:00am

"Dynamics of Multidimensional Nonlinear Wave Structures of Soliton and Vortex Types in Dispersive Media"

Professor Vasily Yu. Belashov
Kazan State Power Engineering University
51 Krasnosel'skaya, Kazan 420066, Russia

Abstract

The theory and numerical simulations of nonintegrable equations and sets of equations admitting locally stationary solutions (exactly), such as the 3D Generalized Kadomtsev-Petviashvili (GKP), Derivative Nonlinear Schoedinger (DNLS), and the Euler and corresponding integro-differential equations, are considered. Results of theoretical and numerical studies on the structure, evolution, stability and the interaction dynamics of multimensional (2D and 3D) nonlinear wave structures of soliton and vortex types in plasma and other complex dispersive media are given. Special attention is given to various applications of studies of the dynamics of multidimensional nonlinear waves and solitons, and also vortex structures, to plasmas (such as ion acoustic and magnetosonic waves and streams of charged particles in the ionosphere), to atmospheres (synoptical cyclonic eddies and tornado-like vortexes), and to hydrospheres (hydrodynamic vortex movements in channels).

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Thursday, 4 August, 2:00pm

"So You Want to Become a Wall Street Rocket Scientist?"

Dr Glenn Kentwell
Global Rates and Structuring
Citigroup

Abstract

Between the idea
And the reality
Between the motion
And the act
Falls the shadow

T.S. Elliot

As hinted by T.S. Elliot, there is a 'strange force' acting between an initial idea and the eventual realization of the idea (the reality). In this talk I will discuss, based on my experience, how financial product development works in practics and how we deal with this very real issue. I will also offer my views of the relevance of recent trends in financial methematics research and, to a lesser extent, econopysics.

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Wednesday, 3 August, 11:00am

"Equilibrium and Dynamics of Vortices in 2D Euler Flow"

Prof. Dan Dubin
Vice Chair for Undergraduate Education
Dept of Physics , Mayer Hall Rm 3130
UC San Diego La Jolla CA 92093-0319, USA

Abstract

Turbulent dynamics in 2D fluids has been an active research topic for decades, with applications in geophysics, planetary physics (eg. the great red spot) and plasma physics to name a few examples. Magnetically confined electron columns evolve as nearly incompressible 2D fluids, allowing quantitative study of vortices and self-organization in freely relaxing turbulence. The electron density is proportional to the vorticity (the curl of the velocity field) and can be accurately measured at any time using a phosphor screen and a high-resolution camera. This talk will discuss various experiments on 2D fluid dynamics using a pure electron plasma, and the theory work these experiments have provoked.
For example, initially turbulent states consisting of 50-100 vortices are observed to relax through chaotic vortex-merger and filamentation processes, typically resulting in a single large vortex. However, some initial conditions result in the formation of ordered patterns of vortices ("vortex crystals") rigidly rotating within a weaker background vorticity(1). Such "phalanxes of tornadoes" have never been previously observed to form from turbulent initial states.
Recent 2D vortex in cell simulations have reproduced the vortex crystal states and have helped clarify the underlying mechanisms in the formation process(2). Other analytic and numerical work has focused on the interaction between vortices and a weak background vorticity. Surprisingly, many characteristics of the final vortex crystal states can be predicted by maximization of entropy subject to integral constraints(3); here the entropy is that of the incompressible background, described by Fermi statistics.
* Supported by grants from the NSF and ONR. Work performed in collaboration with C. F. Driscoll, T. M. O'Neil, D. A. Schecter, and D. Z. Jin.

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Thursday, 9 June, 11:00am

"Entropy production and the second law of thermodynamics: a general review and applications in low-temperature plasma physics"

Adjunct Prof. Robert Robson
Research School of Physical Sciences & Engineering
The Australian National University
Canberra 0200

Abstract

Most naturally occurring systems are in non-equilibrium states and undergo irreversible transformations, which are describable macroscopically only through non-equilibrium thermodynamics, a subject which is quite distinct from classical thermostatics, and which is still to find its full potential in analysis of complex systems. Of central importance is the entropy production, which according to the second law can never be negative, and which exhibits an extremal nature under certain circumstances. Variational principles such as these perhaps hold out the best hope of understanding the behaviour of some complex systems in the most straightforward way, an idea which Paltridge pursued some time ago in the study of the global climate.
In this talk we review the essential features of non-equilibrium thermodynamics, including Onsager reciprocity and Prigogine's theorem of minimum entropy production, and go on to discuss application to two examples in low temperature plasma physics.

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Thursday, 5 May, 11:00am

"A Micromechanical Continuum Theory for Densely Packed Granular Media"

Dr Antoinette Tordesillas
Department of Mathematics & Statistics
The University of Melbourne
Victoria 3010

Abstract

Our past research program focused on the modelling of granular-solid interaction systems from a Contact Mechanics perspective. Of primary interest was the soil-tyre interaction system in which a classical plasticity model was used to represent the soil. The study yielded a new modelling approach that obviated the need for a-priori information on the contact properties (i.e. contact area, and forces and displacements of points therein). In the past, it was common practice to adopt simplifying assumptions on these properties – effectively limiting the predictive capabilities of the interaction model. From the constitutive viewpoint, we learnt an important lesson: classical plasticity models of granular media do not provide reliable predictions of the interaction process for two reasons: (a) such models have no length scale to accommodate key microstructural mechanisms known to govern bulk behaviour of soils, (b) the associated boundary value problems are ill-posed (i.e. non-unique solutions) and, consequently, finite element simulations of the interaction process suffered severe mesh sensitivity (i.e. mesh size and alignment dependence).
In this talk, we describe advancements from our current research program aimed at the development of a micromechanical continuum theory for densely packed granular media. The methodology being developed weaves together Thermomechanical and Micropolar principles and techniques. With guidance from experiments and discrete element (DEM) simulations, we developed a new breed of constitutive models with several distinct advantages over past models. The models have ‘high-resolution’ predictive capability for both local behaviour (e.g. critical microstructures like shear bands) and global behaviour, due to the underlying homogenisation scheme, devised on the scale of only a few particles (i.e. a particle and its first ring of neighbours). The models can account for the most influential mechanisms governing granular deformation, including particle rotations, rolling resistance, and evolution of force and contact anisotropies. Moreover, these models are expressed in terms of physical properties of the particles and their interactions (e.g. particle size, stiffness coefficients, rolling resistance and sliding friction), thus enabling direct comparison of model predictions with those from DEM simulations.
Despite these promising advances, many critical problems remain. Our existing micromechanical models are mainly confined to small deformations of two-dimensional assemblies of uniformly sized circular particles. Studies on the effects of particle size distribution and angularity are in its nascent stages. Ongoing efforts to address these problems, as well as recent results from finite element (FEM) implementations of our existing models to benchmark experiments, will be presented. A comparison between the FEM and DEM predictions will be made.

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Wednesday, 30 March, 11:00am

"Nusselt Number Scaling in Plasma and Fluid Turbulence"

Professor Sadruddin Benkadda
Equipe Dynamique des Systèmes Complexes, UMR 6633
CNRS­Université de Provence
Marseille, France

Abstract

Anomalous heat transport caused by ion temperature gradient (ITG) driven turbulence in tokamak plasmas is evaluated from numerical simulations of the two dimensional (2D) partial-differential equations of the ITG model and of a reduced one-dimensional (1D) version derived from a quasilinear approximation. In the strongly turbulent state, intermittent bursts of thermal transport are observed in both cases. In the strongly turbulent regime, the reduced model as well as the direct numerical simulation (DNS) show that the Nusselt number Nu (normalized heat flux) scales with the normalized ion pressure gradient K_i as Nu ~ K_i^1/3. Since the Rayleigh number for ITG turbulence is proportional to K_i, the Nusselt number scaling for ITG turbulence is thus similar to the classical thermal transport scaling for Rayleigh­Bénard convection in neutral fluids.

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Thursday, 24 March, 11:00am

"Complex Networks: Dynamics, Optimization and Control"

Professor David J. Hill, Federation Fellow
Department of Information Engineering, Building 115
Research School of Information Sciences and Engineering, ANU

Abstract

Complex networks such large power grids, the Internet, transportation networks and co-operation networks of all kinds provide many challenges for scientists and engineers. In particular, advanced societies have become dependent on large infrastructure networks to an extent beyond our capability to plan and control them. The recent spate of collapses in power grids and virus attacks on the Internet illustrate the need for research on modelling, analysis of behaviour, systems theory, planning and control in such networks. This seminar will describe some progress in these directions and plans for an ARC Federation Fellowship project with the same title as the seminar, which has just begun in RSISE.

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Thursday, 10 February 2005, 11:00am

"Modelling the Effects of Anaesthesia on Human-Brain Electrical Activity"

Dr David Liley
Centre for Intelligent Systems and Complex Processes
Swinburne University of Technology
Melbourne, Australia

Abstract

Despite many decades of research into the mechanisms underlying general anaesthesia there are surprisingly few integrated theories attempting to explain this remarkable phenomenon. This has been largely due to the fact that there has been no real agreement on what macroscopic observable or observables of anaesthetic action are to be modelled that quantitatively reflect the hypnotic (unconsciousness) state. However the recent development of a number of successful clinical depth-of-anaesthesia monitoring approaches now clearly indicates that the macroscopic consequences of general anaesthesia correlate well with EEG activity. Here we outline an integrated theory of general anaesthetic (GA) action based on a physiologically motivated continuum theory of cortical electrorhythmogenesis. This theory establishes a mesoscopic link between the well characterised effects of GAs on the subcellular and molecular machinery of inter-neuronal communication with the GA induced electroencephalographic changes.

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2004 SEMINAR ABSTRACTS

Friday, 24 September 2004, 11:00am

"Transport, Dissipation and Fluctuations"

Dr M.P. Das
Department of Theoretical Physics
Research School of Physical Sciences and Engineering
The Australian National University

Abstract

Physics of carrier transport in low dimensional confined structures has an enormous theoretical and experimental literature. Particularly the statistical mechanics of a driven system has many nontrivial unsolved issues.
After giving a general introduction I shall discuss conductance and fluctuations in mesoscopic open quantum devices. Quantum point contact and quantum wire devices will be analysed as test cases. These systems will be compared and contrasted in two different conceptual paradigms, namely Landauer approach and Boltzmann-Landau theory. I shall demonstrate what the experiments have to say ultimately.

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Wednesday, 1st September 2004, 11:00am

"Quantum mechanics and the Riemann zeros"

Professor Sir Michael Berry, FRS
Department of Physics
Bristol University

Abstract

The Riemann hypothesis can be interpreted as stating that the prime numbers contain 'music', whose component frequencies are the Riemann zeros. The question "Frequencies of what?" leads to tantalizing connections with the energy levels of quantum systems whose corresponding classical motion is chaotic. At the level of statistics, predictions for the Riemann zeros based on semiclassical quantum asymptotics (with primes as periods of classical trajectories) have reached a high degree of accuracy and refinement. For the zeros themselves, the Riemann-Siegel formula and its improvements lead to new ways of calculating quantum levels.

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Thursday, 22nd July 2004, 11:00am

"Exploring Complex Networks and Prospective Applications"

Professor Jin-Qing Fang
Research Professor
China Institute of Atomic Energy
Beijing China Fellow
City University of Hong Kong
Hong Kong, China

Abstract

Complex networks are studied across many fields of science and technology, from physics to biology, and from nature to society, they pervade everywhere. Great progress in this field has been made since 1998, such as Small-world effect, Scale-free and Super-family. Small-worlds research and related fields study a set of network structures with well-defined properties. This new area has been gaining momentum recently. Theoretical studies have advanced our understanding of such networks while empirical studies have shown these networks to be ubiquitous in both nature and society. In particular, systems that appear to be well modeled by such networks include World Wide Web documents, Internet routers, the cellular metabolic network, ecological food webs, social networks, and many others. Growing references describe the research being undertaken in this burgeoning field. In this seminar , we will survey and review current main progresses and associated issues through a discussion of the field of small-worlds research with numerous examples, including our works. Finally, we point out some research outlooks and possible prospective for applications in the future.

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2003 SEMINAR ABSTRACTS

Thursday, 6th November, 11:00am

"What can Complexity Science offer the new specialisation of Integration and Implementation Sciences?"

Dr Gabriele Bammer
National Centre for Epidemiology and Population Health, ANU

Abstract:

The developing specialisation of Integration and Implementation Sciences draws together six key theoretical and methodological strands: research transfer, translation and transformation; inter- and trans-disciplinarity; systems thinking; participatory methods; complexity science; and diverse epistemologies. The specialisation is a response to increasing appreciation by researchers, funders and research end-users that new research skills must be developed if human societies are to be more effective in tackling the complex problems that confront us. Researchers must collaborate and integrate across traditional boundaries both within and outside the research sphere, as well as become more involved in the implementation of their research in policy, product and action. There is now a critical mass of researchers who have been developing theory and methods to deal with complexity, uncertainty, change and imperfection in order to integrate across disciplines, 'knowledges', cultures, organisations, and between research and its implementation.
The seminar will briefly describe the new specialisation of Integration and Implementation Sciences and focus on discussion of the role of complexity sciences as part of the specialisation.

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Friday, 24th October, 4:00pm

"Simulating Human Evolution"

Dr Ken Wessen
Link Building Seminar room RSPhysSE

Abstract

Recent times have seen a great deal of activity and progress in human origins research, from the advent of molecular methods in the 1960s, to the many important fossil Hominid discoveries of the last few years. Nevertheless, the debate over whether particular fossil species are direct human ancestors or not, and whether the fossil record and molecular results support a recent African origin, or multiregional continuity continues to rage. There is clearly a substantial need for fundamental work studying the methods employed in interpretation of these data.

The primary aim of my research is to begin to address this need by means of direct computer modelling and simulation of the many underlying and interacting processes, and by so doing make a significant contribution to the approach of such studies. At the same time, since the impact of computer methods in evolutionary studies continues to increase in importance, it is also important to enlighten some of the "black box" aspects of these methods, and thus help ensure that their frequent use for data analysis is not without sufficient attention to their inherent simplifications and limitations.

In this talk I will outline two related, but distinct, simulations, each designed to model important aspects of evolution in general, and the origin and evolution of humans in particular. The first simulation, Specialist, models the evolution of species over millions of years, modelling both hereditary and non-hereditary character change, and uses the resulting data to construct phylogenies, that may then be compared to the true phylogeny. The second simulation, Genie, models several generations of individuals in up to three populations, and analyses the results in the light of coalescent theory for the purely paternal and maternal genealogies (corresponding to Y chromosome and mtDNA inheritance), as well as the "biological" genealogy, or pedigree, where lineages are traced back through both parents simultaneously.

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Thursday, 30th October, 11:00am

"Random Evolution of Idiotypic Networks: Dynamics and Architecture"

Dr Markus Brede
CSIRO Centre for Complex Systems Science

ABSTRACT

The talk deals with modelling a subsystem of the immune system, the so-called idiotypic network. Idiotypic networks, a concept conceived by N.K. Jerne in 1974, are functional networks of interacting antibodies and B-cells. In principle, Jernes’ framework provides solutions to many issues in immunology, such as immunological memory, mechanisms for antigen recognition and the question of self/non-self discrimination. Explaining the interconnection between the elementary components’ local dynamics, network formation and architecture, and possible modes of global system function appears to be an ideal playground of statistical mechanics. We present a simple cellular automaton model based on a graph representation of the system. From a simplified description of idiotypic interactions rules for the random evolution of networks of occupied and empty sites on these graphs are derived. In certain biologically relevant parameter regimes the resultant dynamics lead to stationary states. A stationary state is found to correspond to a typical pattern of network organisation. It turns out that even these very simple rules give rise to a multitude of different kinds of patterns. In the talk methods are presented to characterise such stationary state networks. Based on this description, ‘static’ and ‘dynamic’ network patterns are distinguished. The observed types of stationary state networks are related to possible operational modes of real idiotypic networks. A type of ‘dynamic’ network is found that displays many features of real idiotypic networks and could explain transitions in the network structure if changes in essential parameters occur, e.g., the influx of new idiotypes from bone-marrow.

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2002 SEMINAR ABSTRACTS

Monday April 29 2002, 2:00 pm

What a tangled web – the network model of complexity

Professor David G. Green
Professor of Information Science, Complex Systems Group
Charles Sturt University

Link Building Seminar Room, RSPhysSE

ABSTRACT

Connections matter. Sheer size does not make a system complex; interactions do. Graphs and networks underlie both the structure and behaviour of all complex systems.This fundamental result has far-reaching implications for systems of all kinds. It's effects include both criticality and modularity. This overview explores the network model and some of its implications to physical, biological, social, economic and computational systems.

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Thursday August 1 2002, 11:00 am

The Game of Life

Professor John H Conway
Professor of Finite Mathmatics, Princeton University

Link Building Seminar Room, RSPhysSE

ABSTRACT

The Game of Life, invented by John Conway in 1970, is probably the most often programmed computer game in existence. Life provides one of the simplest examples of emergent complexity and self-organization. In this seminar John Conway will give his own personal perspective on the Game of Life.

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Monday, 9th December, 2002

Joint Centre for Complex Systems/ACT ANZIAM Annual Meeting

Link Building Seminar Room, RSPhysSE

Schedule of talks

2.00 "Control of Chaos by Time-Delayed Feedback: Theory and Applications"
Hartmut Benner, Institut fuer Festkoerperphysik, Darmstadt, Germany

3.00 Afternoon tea

3.30 Series of short talks (each approx 10-15 mins)

"Modelling Human Ecosystems with Agents"
Pascal Perez, CIRAD, RSPAS

"From 2d hyperbolic tilings to n-dimensional euclidean networks"
Stephen Hyde, Applied Maths, RSPhysSE

"Coverings from hyperbolic space to euclidean space and hyperbolic groups"
Vanessa Robins, Applied Maths, RSPhysSE

"An approach to model selection"
Mike Osborne, CMA, MSI

"Sparse grids and complex systems"
Markus Hegland and Steve Roberts, MSI

"Up and Down in Disordered Graphs"
Tomaso Aste, Applied Maths, RSPhysSE

"An interest rates cluster analysis"
Tiziana Di Matteo, Applied Maths, RSPhysSE

"Probability modelling in complexity"
Daryl Daley, CMA, MSI

"Dissipative solitons"
Nail Akhmediev, Optical Sciences Centre, RSPhysSE

"Modelling stromatolites"
Murray Batchelor, Theoretical Physics, RSPhysSE & CMA, MSI

5.50 Annual General Meeting of ACT ANZIAM

6.00 BBQ