Artykuły w czasopismach na temat „Glass transition, statistical mechanics, disorder system”

Spin-models in random fields (RFs) are good representations of many impure materials. Their macroscopic collective behaviour is dominated by the fluctuations in the random fields which accumulate on large scales even if the local field is arbitrarily small. This feature is shared by other weakly disordered models, like flux lines or domain walls in random media. We review some of the main theoretical attempts to describe such systems. A modification of Harris’ argument demonstrates that at the critical point the RF disorder is relevant and that (hyper)scaling must be changed. A domain argument invented by Imry and Ma shows that long-range order is not destroyed by weak RFs in more than d=2 dimensions. This result is supported both by a more refined treatment of the domain argument and by considering the roughness of an isolated domain wall due to the randomness. The wall (or flux line) becomes rough due to disorder but if d>2 the wall remains a well-defined object in RF systems. Different approaches are used to calculate the roughness exponent ζ for walls and lines. Some applications of ζ for the description of type-II superconductors and incommensurate systems are given. More detailed calculations are possible for one-dimensional, Bethe-lattice or the hierarchical Dyson model systems, which confirm as a rule the more approximate treatment of the other sections. In one dimension there is an interesting relation between the statistical mechanics of these models and nonlinear dynamics. Non-classical critical behaviour occurs in RF systems for d<6 and is determined in general by three independent exponents which fulfil certain inequalities. The new exponent θ≡yJ>0 is related to the violation of conventional hyperscaling and is determined by the energy ~H0ξ0 of a correlated region of size ξ. In a renormalization group treatment, the temperature T turns out to be a (dangerous) irrelevant variable which is the most prominent property of the systems considered in this review. The irrelevance of thermal fluctuations on large scales produces metastability and hysteresis effects both in the transition region and in the ordered phase, only briefly considered here. These features occur also in other systems with a disordered T=0 fixed point like in the ordered phase of a spin-glass.

In this paper, we study the phase transition in a face-centered-cubic antiferromagnet with Ising spins as a function of the concentration p of ferromagnetic bonds randomly introduced into the system. Such a model describes the spin-glass phase at strong bond disorder. Using the standard Monte Carlo simulation and the powerful Wang–Landau flat-histogram method, we carry out in this work intensive simulations over the whole range of p. We show that the first-order transition disappears with a tiny amount of ferromagnetic bonds, namely p ~ 0.01, in agreement with theories and simulations on other 3D models. The antiferromagnetic long-range order is also destroyed with a very small p (≃5%). With increasing p, the system changes into a spin glass and then to a ferromagnetic phase when p > 0.65. The phase diagram in the space (Tc, p) shows an asymmetry, unlike the case of the ±J Ising spin glass on the simple cubic lattice. We calculate the relaxation time around the spin-glass transition temperature and we show that the spin autocorrelation follows a stretched exponential relaxation law where the factor b is equal to ≃1/3 at the transition as suggested by the percolation-based theory. This value is in agreement with experiments performed on various spin glasses and with Monte Carlo simulations on different SG models.

A model binary alloy Ax B1−x where A and B represent ferromagnetic and paramagnetic transition metal respectively is considered within the framework of periodic Anderson model, and the effects of d-level disorder and variation of electron concentration due to alloying on the magnetic properties are investigated. The phase boundary, thermal behavior of magnetization and susceptibility of the alloy are obtained using HF approximation for the Coulomb interaction and the virtual crystal approximation for d-level disorder. The ferromagnetic state of alloy vanishes at a critical concentration xc which depends on d-band width, strength of s-d hybridization and the Coulomb interaction. The re-entrant magnetic phase is found within a small region of x for alloy with narrow d-band. For x≲xc, the magnetic properties resemble that of spin-glass system. For x≪xc, the alloy behaves like a Pauli paramagnet. The re-entrant and spin-glass-like phases are associated with the increase in d-level population as temperature decreases. Local moment for x≃1 decreases with temperature up to Tc whereas the reverse is the situation for alloy exhibiting spin-glass-like behavior.

The time correlation functions associated with the Onsager phenomenological coefficients for isothermal matter transport have been calculated by Monte Carlo simulation for a binary system (A,B) at the equiatomic composition according to the Kikuchi-Sato model of an order-disorder alloy with vacancy transport mechanism. The diagonal (AA) time correlation functions are positive, decay monotonically to zero, and exhibit a long time tail where they vary as t-n where t is time; the exponent n varies weakly with temperature at high temperatures and more rapidly as the temperature is lowered through the order-disorder transition temperature. In the region of short-range order the off-diagonal (AB) time correlation function is negative but otherwise shows similar behaviour to the diagonal one, although as the transition temperature is approached n varies more rapidly. At the transition temperature and below, the off-diagonal time correlation function increases from an initial negative value to a maximum where it is positive and then, at later times, decreases to zero. The implications of these observations for approximate theoretical calculations of the phenomenological coefficients are briefly indicated.Key words: diffusion, non-equilibrium phenomena, statistical mechanics, transport properties.

Silane-coated glass microspheres randomly embedded in an epoxy polymer matrix have been employed as a model system to investigate the degradation of disordered composite materials by water, and to test various models of deformation and fracture. Numerous composites containing sodalime (A) glass in the range 0 to 25% by volume were tested dry and immersed in saturated NaCl at 40 °C for periods up to 70 days before testing. Enhanced osmotic water uptake due to percolating interface damage was observed for composites containing more than 15% glass. The electrical resistance of similar composites filled with conducting spheres confirmed the existence of a percolation transition, though with high resistance values implying no direct contact of the spheres. Tensile measurements conducted on dry material at a nominal strain rate of about 10−3 s−1 showed an increase in elastic modulus and a decrease in the fracture strength with increasing glass content. New detail was apparent in these curves and confirmed by statistical analyses. For wet specimens, in addition to a general embrittlement effect of water absorption, there was a distinct plateau or small peak in fracture strength in the range 9 to 12% glass, and an abrupt drop between 12 and 15%. The plateau can be related to favorable crack interaction effects between disconnected clusters of interfaces just below the percolation threshold. The steep increase in elastic modulus with glass content seen in the dry material vanished entirely in wet material, which behaved like a porous polymer above 6% glass, owing to osmotic interface damage within particle clusters.

A glassy phase in disordered two dimensional (2D) electron systems may exist at low temperatures for electron densities lying intermediate between the Fermi liquid and Wigner crystal limits. The glassy phase is generated by the combined effects of disorder and the strong electron-electron correlations arising from the repulsive Coulomb interactions. Our approach here is motivated by the observation that at low electron densities the electron pair correlation function, as numerically determined for a non-disordered 2D system from Monte Carlo simulations, is very similar to the pair correlation function for a 2D classical system of hard discs. This suggests that theoretical approaches to 2D classical systems of hard discs may be of use in studying the disordered, low density electron problem. We use this picture to study its dynamics on the electron-liquid side of a glass transition. At long times the major relaxation process in the electron-liquid will be a rearrangement of increasingly large groups of the discs, rather than the movement of the discs separately. Such systems have been studied numerically and they display all the characteristics of glassy behaviour. There is a slowing down of the dynamics and a limiting value of the retarded spatial correlations. Motivated by the success of mode-coupling theories for hard spheres and discs in reproducing experimental results in classical fluids, we use the Mori formalism within a mode-coupling theory to obtain semi-quantitative insight into the role of electron correlations as they affect the time response of the weakly disordered 2D electron system at low densities.

A broad range of quantum optimization problems can be phrased as the question of whether a specific system has a ground state at zero energy, i.e., whether its Hamiltonian is frustration-free. Frustration-free Hamiltonians, in turn, play a central role for constructing and understanding new phases of matter in quantum many-body physics. Unfortunately, determining whether this is the case is known to be a complexity-theoretically intractable problem. This makes it highly desirable to search for efficient heuristics and algorithms to, at least, partially answer this question. Here we prove a general criterion—a sufficient condition—under which a local Hamiltonian is guaranteed to be frustration-free by lifting Shearer’s theorem from classical probability theory to the quantum world. Remarkably, evaluating this condition proceeds via a fully classical analysis of a hardcore lattice gas at negative fugacity on the Hamiltonian’s interaction graph, which, as a statistical mechanics problem, is of interest in its own right. We concretely apply this criterion to local Hamiltonians on various regular lattices, while bringing to bear the tools of spin glass physics that permit us to obtain new bounds on the satisfiable to unsatisfiable transition in random quantum satisfiability. We are then led to natural conjectures for when such bounds will be tight, as well as to a novel notion of universality for these computer science problems. Besides providing concrete algorithms leading to detailed and quantitative insights, this work underscores the power of marrying classical statistical mechanics with quantum computation and complexity theory.

The random first order transition theory (RFOT) describing the transition from a supercooled liquid to an ideal glass has been actively developed over the last twenty years. This theory is formulated in a way that allows a description of the transition from the initial equilibrium state to the final metastable state without considering any kinetic processes. The RFOT and its applications for real molecular systems (multicomponent liquids with various intermolecular potentials, gel systems, etc.) are widely represented in English-language sources. However, these studies are practically not described in any Russian sources. This paper presents an overview of the studies carried out in this field. REFERENCES 1. Sanditov D. S., Ojovan M. I. Relaxation aspectsof the liquid—glass transition. Uspekhi FizicheskihNauk. 2019;189(2): 113–133. DOI: https://doi.org/10.3367/ufnr.2018.04.0383192. Tsydypov Sh. B., Parfenov A. N., Sanditov D. S.,Agrafonov Yu. V., Nesterov A. S. 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AbstractWe study the properties of an ODE description of schools of fish (B. Birnir, An ODE model of the motion of pelagic fish, J. Stat. Phys. 128(1/2) (2007), 535–568.) and how they change in the presence of a random acceleration. The model can be reduced to one ODE for the direction of the velocity of a generic fish and another ODE for its speed. These equations contain the mean speed $\bar{v}$ and a Kuramoto order parameter $r$ for the phases of the fish velocities. In this paper, we give a complete qualitative analysis of the system for large number of particles. We show that the stationary solutions of the ODEs consist of an incoherent unstable solution with $r\!\!=\!\!\bar{v}\!\!=\!\!0$ and a globally stable solution with $r\!=\!1$ and a constant $\bar{v}\!>\!0$. In the latter solution, all the fish move uniformly in the same direction with $\bar{v}$ and the direction of motion determined by the initial configuration of the school. This is called the “migratory solution”. In the second part of the paper, the directional headings of the particles are perturbed, in two distinct ways, and the speeds accelerated in order to obtain two distinct classes of non-stationary, complex solutions. We show that the perturbed systems have similar behavior as the unperturbed one, and derive the resulting constant value of the average speed, verifying the numerical observations. Finally, we show that the system exhibits a similar bifurcation to that in Vicsek and Czirok (T. Vicsek, A. Czirók, E. Ben-Jacob, I. Cohen and O. Shochet, Novel type of phase transition in a system of self-driven particles, Phys. Rev. Lett. 75(6) (Aug 1995), 1226–1229.) between phases of synchronization and disorder. Either increasing the variance of the Brownian angular noise, or decreasing the turning rate, or coupling between the particles, cause a similar phase transition. These perturbed models represent a more realistic view of schools of fish found in nature. We apply the theory to compute the order parameter for a simulation of the Chile-Peru anchovy fishery.

ABSTRACTDespite significant atomic-scale heterogeneity, bulk metallic glasses well below their glass transition temperature exhibit a surprisingly robust elastic regime and a sharp elastic-to-plastic transition with a yield stress that depends approximately linearly on temperature. The present work attempts to understand these features within the framework of thermally activated plasticity. The presented statistical thermal activation model, in which the number of available structural transformations scales exponentially with system size, results in two distinct temperature regimes of deformation. At temperatures close to the glass transition temperature thermally activated Newtonian plastic flow emerges, whilst at lower temperatures the deformation properties fundamentally change due to the eventual kinetic freezing of the available structural transformations. In this regime, a linear temperature dependence emerges for the stress which characterises the elastic to plastic transition. For both regimes the transition to macroscopic plastic flow corresponds to a transition from a barrier energy dominated to a barrier entropy dominated statistics. The work concludes by discussing the possible influence that kinetic freezing might have on the low temperature heterogeneous and high temperature homogeneous plasticity of bulk metallic glasses.

We study the statistical mechanics of supercooled liquids when the system evolves at a temperature TT with a field \epsilonϵ linearly coupled to its overlap with a reference configuration of the same liquid sampled at a temperature T_0T0. We use mean-field theory to fully characterize the influence of the reference temperature T_0T0, and we mainly study the case of a fixed, low-T_0T0 value in computer simulations. We numerically investigate the extended phase diagram in the (\epsilon,T)(ϵ,T) plane of model glass-forming liquids in spatial dimensions d=2d=2 and d=3d=3, relying on umbrella sampling and reweighting techniques. For both 2d2d and 3d3d cases, a similar phenomenology with nontrivial thermodynamic fluctuations of the overlap is observed at low temperatures, but a detailed finite-size analysis reveals qualitatively distinct behaviors. We establish the existence of a first-order transition line for nonzero \epsilonϵ ending in a critical point in the universality class of the random-field Ising model (RFIM) in d=3d=3. In d=2d=2 instead, no phase transition is found in large enough systems at least down to temperatures below the extrapolated calorimetric glass transition temperature T_gTg. Our results confirm that glass-forming liquid samples of limited size display the thermodynamic fluctuations expected for finite systems undergoing a random first-order transition. They also support the relevance of the physics of the RFIM for supercooled liquids, which may then explain the qualitative difference between 2d2d and 3d3d glass-formers.

ABSTRACTWe have analyzed a non-randomly frustrated spin model which exhibits behavior remarkably similar to the phenomenology of structural glasses. The high-temperature disordered phase undergoes a strong first-order transition to a long-range ordered structure. Using Monte Carlo simulations, we have studied the behavior of the supercooled state by quenching to temperatures below this transition temperature. For a range of supercooling, the system remains ergodic and exhibits dynamics characteristic of supercooled liquids. Below a certain characteristic temperature, however, the system freezes into a “glassy” phase. In this phase, the system is non-ergodic and evolves through a distribution of traps characterized by a power-law distribution of trapping times. This change in the dynamic behavior is concurrent with the appearance of a shear instability.

Abstract We revisit the Haake-Lewenstein-Wilkens (HLW) approach to Edwards-Anderson (EA) model of Ising spin glass [Phys. Rev. Lett. 55, 2606 (1985)]. This approach consists in evaluation and analysis of the probability distribution of configurations of two replicas of the system, averaged over quenched disorder. This probability This approximate result suggest that qEA > 0 at 0 < T < Tc in 3D and 4D. The case of 2D seems to be a little more subtle, since in the present approach energy increase for a domain wall competes with boundary/edge effects more strongly in 2D; still our approach predicts spin glass order at sufficiently low temperature. We speculate, how these predictions confirm/contradict widely spread opinions that: i) There exist only one (up to the spin flip) ground state in EA model in 2D, 3D and 4D; ii) There is (no) spin glass transition in 3D and 4D (2D). This paper is dedicated to the memories of Fritz Haake and Marek Cieplak.

This paper develops a finite element (FE) model of the single fibre fragmentation test designed for direct comparison with experimental results on an E-glass/epoxy system by McCarthy et al. (2015). Interface behaviour is modelled via a cohesive surface, and stochastic Weibull fibre strengths (determined by independent experiments) assigned at random to the elements along the fibre. Predictions from the model agree with experiment for a range of outputs: The evolution of the number of fibre breaks with strain is similar and breaks occur at random locations as required. The model also captures a transition to a Uniform (rather than Weibull) statistical distribution of break locations at later stages of the test consistent with recent experiments. The evolution of the cumulative distribution of fragment lengths is also similar to that of the experiment. In addition, fibre axial stress and interfacial shear stress distributions conform with experimental observation. Correct model predictions of break locations confirm the approach taken on assigning stochastic (Weibull) strengths along the fibre. The effectiveness of the FE model in capturing a number of key aspects of the fragmentation phenomenon suggest its usefulness as a tool in analysing and interpreting fibre fragmentation tests, including back-calculation of interfacial shear strength.

Three-dimensional steady-state Arnold–Beltrami–Childress (ABC) flow has a chaotic Lagrangian structure, and also satisfies the Navier–Stokes (NS) equations with an external force per unit mass. It is well known that, although trajectories of a chaotic system have sensitive dependence on initial conditions, i.e. the famous ‘butterfly effect’, their statistical properties are often insensitive to small disturbances. This kind of chaos (such as governed by the Lorenz equations) is called normal-chaos. However, a new concept, i.e. ultra-chaos, has been reported recently, whose statistics are unstable to tiny disturbances. Thus, ultra-chaos represents higher disorder than normal chaos. In this paper, we illustrate that ultra-chaos widely exists in Lagrangian trajectories of fluid particles in steady-state ABC flow. Moreover, solving the NS equation when $Re=50$ with the ABC flow plus a very small disturbance as the initial condition, it is found that trajectories of nearly all fluid particles become ultra-chaotic when the transition from laminar to turbulence occurs. These numerical experiments and facts highly suggest that ultra-chaos should have a relationship with turbulence. This paper identifies differences between ultra-chaos and sensitivity of statistics to parameters. Possible relationships between ultra-chaos and the Poincaré section, ultra-chaos and ergodicity/non-ergodicity, etc., are discussed. The concept of ultra-chaos opens a new perspective of chaos, the Poincaré section, ergodicity/non-ergodicity, turbulence and their inter-relationships.

"Interactivity implies two agencies in conversation, playfully and spontaneously developing a mutual discourse" -- Sandy Stone (11) I. On Interactivity The difference between interactivity as it is performed across the page and the screen, maintains Sandy Stone, is that virtual texts and virtual communities can embody a play ethic (14). Inserted like a mutation into the corporate genome, play ruptures the encyclopaedic desire to follow seamless links to a buried 'meaning' and draws us back to the surface, back into real-time conversation with the machine. Hypertext theorists see this as a tactic of resistance to homogenisation. As we move across a hypertextual reading space, we produce the text in this unfolding now, choosing pathways which form a map in the space of our own memories: where we have been, where we are, where we might yet be. Play is occupying oneself with diversions. II. Space, Time and Composition Reading in time, we create the text in the space of our own memories. Hypertext theorists maintain that the choices we make around every corner, the spontaneity and contingency involved in these choices, are the bringing into being of a (constantly replaced) electronic palimpsest, a virtual geography. The dislocation which occurs as we engage in nodal leaps draws us back to the surface, rupturing our experience of the narrative and bringing us into a blissful experience of possibility. III. War against the Line There is the danger, on the one hand, of being subsumed by the passive subject position demanded by infotainment culture and the desire it encourages to seek the satisfaction of closure by following seamless links to a buried 'meaning'. On the other hand, we risk losing efficiency and control over the unfolding interaction by entering into an exchange which disorientates us with infinite potential. We cannot wildly destratify. The questions we ask must seek to keep the conversation open. In order to establish a new discursive territory within which to understand this relationship, we should view the interface not simply as a transparency which enables interaction with the machine as 'other', but as a text, a finely-wrought behavioural map which "exists at the intersection of political and ideological boundary lands" (Selfe & Selfe 1). As we write, so are we written by the linguistic contact zones of this terrain. Hypertext is thus a process involving the active translation of modes of being into possible becomings across the interface. The geographic 'space' we translate into a hypertext "is imaginational... . We momentarily extend the linear reading act into a third dimension when we travel a link" (Tolva 4). A literal spatial representation would break from the realm of hypertext and become a virtual reality. Thus, the geographic aspect is not inherent to the system itself but is partially translated into the geometry of the medium via our experience and perception (the 'map'), a process describing our 'line of flight' as we evolve in space. Directional flows between time and its traditional subordination to space in representation implode across the present-tense of the screen and time literally surfaces. Our experience of the constantly-replaced electronic palimpsest is one of temporal surrender: "we give in to time, we give way to time, we give in with time"(Joyce 219). In other words, the subject of hypertext subverts the traditional hierarchy and writes for space, producing the 'terrain' in the unfolding now in the Deleuzian sense, not in space as desired by the State. Johnson-Eilola aligns the experience of hypertext with the Deleuzian War Machine, a way of describing the speed and range of virtual movement created when the animal body splices into the realm of technology and opens an active plane of conflict.. The War Machine was invented by the nomads -- it operates by continual deterritorialisation in a tension-limit with State science, what we might call the command-control drive associated with geometric, dynamic thought and the sedentary culture of the Line. It "exemplifies" the avant-garde mentality that hypertext theorists have been associating with the electronic writing space (Moulthrop, "No War Machine" 1). Playing outside. The State desires an end to the resistance to totalisation promulgated by contingent thought and its thermodynamic relationship to space: the speed which assumes a probabilistic, vortical motion, actually drawing smooth space itself. The war machine is thus an open system opposed to classical mechanics via its grounding in active contingencies and spatio-temporal production. The nomad reads and writes for space, creating the temporal text in the space of her own memory, giving way to time and allowing existent points to lapse before the trajectory of flight. Nomad thought is not dependent on any given theory of relationship with the medium, but works via disruption and (re)distribution, the gaps, stutterings and gasp-like expressions experienced when we enter into conversation with the hypertext. The danger is that the war machine might be appropriated by the State, at which point this light-speed communication becomes of the utmost importance in the war against space and time. As speed and efficient retrieval replace real-space across the instantaneity and immediacy of the terminal, the present-time sensory faculties of the individual are marginalised as incidental and she becomes "the virtual equivalent of the well-equipped invalid" (Virilio 5). In other words, as the frame of real-space and present-time disappears, the text of the reader/writer becomes "sutured" into the discourse of the State, the only goal to gain "complete speed, to cover territory in order for the State to subdivide and hold it through force, legislation or consent" (Virilio, qtd. in Johnson-Eilola). This is when the predetermined geometry of hypertext becomes explicit. The progressive subsumption (or "suturing") of the multiple, nomadic self into the discourse of the computer occurs when "the terms of the narrative are heightened, as each 'node' in the hypertext points outwards to other nodes [and] readers must compulsively follow links to arrive at the 'promised plenitude' at the other end of the link" (Johnson-Eilola 391). When we no longer reflect on the frame and move towards complete speed and efficiency, when we stop playing on the surface and no longer concern ourselves with diversion, the war machine has been appropriated by the State. In this case, there is no revolutionary 'outside' to confront in interaction, as all has been marshalled towards closure. Keeping the conversation open means continuously reflecting on the frame. We cannot wildly destratify and lose control entirely by moving in perpetual bewilderment, but we can see the incompleteness of the story, recognising the importance of local gaps and spaces. We can work with the idea that the "dyad of smooth/striated represents not a dialectic but a continuum" (Moulthrop, "Rhizome" 317) that can be turned more complex in its course. Contingency and play reside in the intermezzo, the "dangerous edges, fleeting, attempting to write across the boundaries between in-control and out-of-control" (Johnson-Eilola 393). The war machine exists as at once process and product, the translation between smooth-striated moving in potentia: the nomadic consciousness can recognise this process and live flux as reality itself, or consistency. In sum, we avoid subsumption and appropriation by holding open the function of the text as process in our theorising, in our teaching, in our reading and writing across the hypertextual environment. We can either view hypertext as a tool or product which lends itself to efficient, functional use (to organise information, to control and consume in an encyclopaedic fashion), or we can view it as a process which lends itself to nomadic thought and resistance to totalisation in syncopated flows, in cybernetic fits and starts. This is our much-needed rhetoric of activity. IV. An Alternative Story No matter their theoretical articulation, such claims made for hypertext are fundamentally concerned with escaping the logocentric geometry of regulated time and space. Recent explorations deploying the Deleuzian smooth/striated continuum make explicit the fact that the enemy in this literary 'war' has never been the Line or linearity per se, but "the nonlinear perspective of geometry; not the prison-house of time but the fiction of transcendence implied by the indifferent epistemological stance toward time" (Rosenberg 276). Although the rhizome, the war machine, the cyborg and the nomad differ in their particularities and composition, they all explicitly play on the dislocated, time-irreversible processes of chaos theory, thermodynamics and associated 'liberatory' topological perspectives. Rosenberg's essay makes what I consider to be a very disruptive point: hypertext merely simulates the 'smooth', contingent thought seen to be antithetical to regulated space-time and precise causality due to its fundamental investment in a regulated, controlled and (pre)determined geometry. Such a deceptively smooth landscape is technonarcissistic in that its apparent multiplicity actually prescribes to a totality of command-control. Hypertext theorists have borrowed the terms 'multilinear', 'nonlinear' and 'contingency' from physics to articulate hypertext's resistance to the dominant determinist episteme, a framework exemplified by the term 'dynamics', opposing it to "the irreversible laws characteristic of statistical approximations that govern complex events, exemplified by the term, 'thermodynamics'" (Rosenberg 269). This resistance to the time-reversible, non-contingent and totalised worldview has its ideological origins in the work of the avant-garde. Hypertext theorists are fixated with quasi-hypertextual works that were precursors to the more 'explicitly' revolutionary texts in the electronic writing space. In the works of the avant-garde, contingency is associated with creative freedom and subversive, organic logic. It is obsessively celebrated by the likes of Pynchon, Joyce, Duchamp and Cage. Hypertext theorists have reasoned from this that 'nonlinear' or 'multilinear' access to information is isomorphic with such playful freedom and its contingent, associative leaps. Theorists align this nonsequential reasoning with a certain rogue logic: the 'fluid nature of thought itself' exemplified by the explicitly geographic relationship to space-time of the Deleuzian rhizome and the notion of contingent, probabilistic 'becomings'. Hypertext participates fully in the spatio-temporal dialectic of the avant-garde. As Moulthrop observes, the problem with this is that from a topological perspective, 'linear' and 'multilinear' are identical: "lines are still lines, logos and not nomos, even when they are embedded in a hypertextual matrix" ("Rhizome" 310). The spatio-temporal dislocations which enable contingent thought and 'subversive' logic are simply not sustained through the reading/writing experience. Hypertextual links are not only reversible in time and space, but trace a detached path through functional code, each new node comprising a carefully articulated behavioural 'grammar' that the reader adjusts to. To assume that by following 'links' and engaging in disruptive nodal leaps a reader night be resisting the framework of regulated space-time and determinism is "to ignore how, once the dislocation occurs, a normalcy emerges ... as the hypertext reader acclimates to the new geometry or new sequence of lexias" (Rosenberg 283). Moreover, the searchpath maps which earlier theorists had sensed were antithetical to smooth space actually exemplify the element of transcendent control readers have over the text as a whole. "A reader who can freeze the text, a reader who is aware of a Home button, a reader who can gain an instant, transcendent perspective of the reading experience, domesticates contingencies" (Rosenberg 275). The visual and behavioural grammar of hypertext is one of transcendent control and determined response. Lines are still lines -- regulated, causal and not contingent -- even when they are 'constructed' by an empowered reader. Hypertext is thus invested (at least in part) in a framework of regularity, control and precise function. It is inextricably a part of State apparatus. The problem with this is that the War Machine, which best exemplifies the avant-garde's insurgency against sedentary culture, must be exterior to the State apparatus and its regulated grid at all times. "If we acknowledge this line of critique (which I think we must), then we must seriously reconsider any claims about hypertext fiction as War Machine, or indeed as anything en avant" (Moulthrop, "No War Machine" 5). Although hypertext is not revolutionary, it would be the goal of any avant-garde use of hypertext to find a way to sustain the experience of dislocation that would indicate liberation from the hegemony of geometry. I would like to begin to sketch the possibility of 'contingent interaction' through the dislocations inherent to alternative interfaces later in this story. For the time being, however, we must reassess all our liberation claims. If linearity and multilinearity are identical in terms of geometric relations to space-time, "why should they be any different in terms of ideology", asks Moulthrop ("Rhizome" 310). V. On Interactivity Given Rosenberg's critique against any inherently revolutionary qualities, we must acknowledge that hypermedia "marks not a terminus but a transition," Moulthrop writes ("Rhizome" 317). As a medium of exchange it is neither smooth nor striated, sophist nor socratic, 'work' nor 'text': it is undergoing an increasingly complex phase transition between such states. This landscape also gives rise to stray flows and intensities, 'Unspecified Enemies' which exist at the dangerous fissures and edges. We must accept that we will never escape the system, but we are presented with opportunities to rock the sedentary order from within. As a group of emerging electronic artists see it, the dis-articulation of the point'n'click interface is where interaction becomes reflection on the frame in fits and starts. "We believe that the computer, like everything else, is composed in conflict," explain the editors of electronic magazine I/O/D. "If we are locked in with the military and with Disney, they are locked in not just with us, but with every other stray will-to-power" (Fuller, Interview 2). Along with Adelaide-based group Mindflux, these artists produce hypertext interfaces that involve sensory apparatus and navigational skills that have been marginalised as incidental in the disabling interactive technologies of mainstream multimedia. Sound, movement, proprioception, an element of randomness and assorted other sensory circuits become central to the navigational experience. By enlisting marginalised senses, "we are not proposing to formulate a new paradigm of multimedial correctness," stresses Fuller, "but simply exploring the possibility of more complicated feedback arrangements between the user and the machine" (Fuller, qtd. in Barnet 48). The reader must encounter the 'lexias' contained in the system via the stray flows, intensities, movements, stratas and organs that are not proper to the system but shift across the interface and the surface of her body. In Fuller's electronic magazine, the reader is called upon to converse with the technology outside of the domesticated circuits of sight, dislocating the rigorous hierarchy of feedback devices which privilege the sight-machine and disable contingent interaction in a technonarcissistic fashion. The written information is mapped across a 'fuzzy' sound-based interface, sensitive at every moment to the smallest movements of the reader's fingers on the keys and mouse: the screen itself is black, its swarm of links and hotspots dead to the eye. The reader's movements produce different bleeps and beats, each new track opening different entrances and exits through the information in dependence upon the fluctuating pitch and tempo of her music. Without the aid of searchpaths and bright links, she must move in a state of perpetual readjustment to the technology, attuned not to the information stored behind the interface, but to the real-time sounds her movements produce. What we are calling play, Fuller explains, "is the difference between something that has a fixed grammar on the one hand and something that is continually and openly inventing its own logic on the other" (Fuller & Pope 4). The electronic writing space is not inherently liberatory, and the perpetual process of playing with process across the interface works to widen the 'fissures across the imperium' only for a moment. According to Fuller and Joyce, the 'process of playing with process' simply means complicating the feedback arrangements between the user's body and the machine. "We need to find a way of reading sensually ... rather than, as the interactive artist Graham Weinbren puts it, descending 'into the pit of so-called multimedia, with its scenes of unpleasant 'hotspots,' and 'menus' [that] leaves no room for the possibility of a loss of self, of desire in relation to the unfolding'" remarks Joyce (11). Interactivity which calls upon a mind folded everywhere within the body dislocates the encyclopaedic organisation of data that "preserves a point of privilege from where the eye can frame objects" by enlisting itinerant, diffuse desires in an extended period of readjustment to technology (Fuller & Pope 3). There are no pre-ordained or privileged feedback circuits as the body is seen to comprise a myriad possible elements or fragments of a desiring-machine with the potential to disrupt the flow, to proliferate. Mainstream multimedia's desire for 'informational hygiene' would have us transcend this embodied flux and bureaucratise the body into organs. Information is fed through the circuits of sight in a Pavlovian field of buttons and bright links: interactivity is misconceived as choice-making, when 'response' is a more appropriate concept. When the diffuse desire which thrives on disruption and alternative paradigms is written out in favour of informational hygiene, speed and efficient retrieval replace embodied conversation. "Disembodied [interaction] of this kind is always a con... . The entropic, troublesome flesh that is sloughed off in these fantasies of strongly male essentialism is interwoven with the dynamics of self-processing cognition and intentionality. We see computers as embodied culture, hardwired epistemology" (Fuller 2). Avant-garde hypertext deepens the subjective experience of the human-computer interface: it inscribes itself across the diffuse, disruptive desires of the flesh. Alternative interfaces are not an ideological overhaul enabled by the realm of technê, but a space for localised break-outs across the body. Bifurcations are enacted on the micro level by desiring-machines, across an interface which seeks to dislocate intentionality in conjunction with the marginalised sensory apparatus of the reader, drawing other minds, other organs into localised conversation with command-control. "The user learns kinesthetically and proprioceptively that the boundaries of self are defined less by the skin than by the [local] feedback loops connecting body and simulation in a techno-bio-integrated circuit" (Hayles 72). She oscillates between communication and control, play and restraint: not a nomad but a "human Deserter assuming the most diverse forms" (ATP, 422). VI. Desire Working from across the territory we have covered, we might say that electronic interaction 'liberates' us from neither the Line nor the flesh: at its most experimental, it is nothing less than reading embodied. References Barnet, Belinda. "Storming the Interface: Mindvirus, I/O/D and Deceptive Interaction." Artlink: Australian Contemporary Art Quarterly 17:4 (1997). Deleuze, Gilles, and Felix Guattari. A Thousand Plateaus: Capitalism & Schizophrenia. Minneapolis: U of Minnesota P, 1987. Fuller, Matt and Simon Pope. "Warning: This Computer Has Multiple Personality Disorder." 1993. 11 Dec. 1998 <http://www.altx.com/wordbombs/popefuller.php>. ---, eds. I/O/D2. Undated. 11 Dec. 1998 <http://www.pHreak.co.uk/i_o_d/>. Hayles, Katherine N. "Virtual Bodies and Flickering Signifiers" October Magazine 66 (Fall 1993): 69-91. Johnson-Eilola, Johndan. "Control and the Cyborg: Writing and Being Written in Hypertext." Journal of Advanced Composition 13:2 (1993): 381-99. Joyce, Michael. Of Two Minds: Hypertext, Pedagogy and Poetics. Ann Arbor: U of Michigan P, 1995. Moulthrop, Stuart. "No War Machine." 1997. 11 Dec. 1998 <http://raven.ubalt.edu/staff/moulthrop/essays/war_machine.php>. ---. "Rhizome and Resistance: Hypertext and the Dreams of a New Culture." Hyper/Text/Theory. Ed. George P. Landow. Baltimore: Johns Hopkins UP, 1994. 299-319. Rosenberg, Martin E. "Physics and Hypertext: Liberation and Complicity in Art and Pedagogy." Hyper/Text/Theory. Ed. George Landow. Baltimore: Johns Hopkins UP, 1994. 268-298. Selfe, Cynthia L., and Richard J. Selfe. "The Politics of the Interface: Power and Its Exercise in Electronic Contact Zones." College Composition and Communication 45.4: 480-504. Stone, Allucquére Roseanne. The War of Desire and Technology. London: MIT Press, 1996. Tolva, John. "Ut Pictura Hyperpoesis: Spatial Form, Visuality, and the Digital Word." 1993. 11 Dec. 1998 <http://www.cs.unc.edu/~barman/HT96/P43/pictura.htm>. Virilio, Paul. "The Third Interval: A Critical Transition." Rethinking Technologies. Ed. Verena Conley. London: U of Minnesota P, 1993. 3-12. Citation reference for this article MLA style: Belinda Barnet. "In the Garden of Forking Paths: Contingency, Interactivity and Play in Hypertext." M/C: A Journal of Media and Culture 1.5 (1998). [your date of access] <http://www.uq.edu.au/mc/9812/garden.php>. Chicago style: Belinda Barnet, "In the Garden of Forking Paths: Contingency, Interactivity and Play in Hypertext," M/C: A Journal of Media and Culture 1, no. 5 (1998), <http://www.uq.edu.au/mc/9812/garden.php> ([your date of access]). APA style: Belinda Barnet. (1998) In the garden of forking paths: contingency, interactivity and play in hypertext. M/C: A Journal of Media and Culture 1(5). <http://www.uq.edu.au/mc/9812/garden.php> ([your date of access]).