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This work represents a natural outlet of recent investigation about the well-posed question for the time differential three-phase-lag model of thermoelasticity. We deal with a cylindrical domain filled by an anisotropic and inhomogeneous thermoelastic material and assume that the initial-boundary data as well as the external supply terms that characterize the problem in concern are concentrated in a compact region of the considered volume. Within such a framework, we show the spatial behavior of the solutions in terms of existence of a domain of influence of the assigned data. We will remark that our results are obtained under restrictions involving the constitutive tensors and the delay times that are in complete agreement with the hypotheses that make the time differential three-phase-lag model thermodynamically consistent. The case of a semi-infinite cylindrical domain is also considered. [ABSTRACT FROM PUBLISHER]

This paper presents a numerical regularization approach to the simultaneous determination of multiplicative space- and time-dependent source functions in a nonlinear inverse heat conduction problem with homogeneous Neumann boundary conditions together with specified interior and final time temperature measurements. Under these conditions a unique solution is known to exist. However, the inverse problem is still ill-posed since small errors in the input interior temperature data cause large errors in the output heat source solution. For the numerical discretisation, the boundary element method combined with a regularized nonlinear optimization are utilized. Results obtained from several numerical tests are provided in order to illustrate the efficiency of the adopted computational methodology. [ABSTRACT FROM AUTHOR]

The structural default model of Lipton and Sepp [Credit value adjustment for credit default swaps via the structural default model, J. Credit Risk 5(2) (2009), pp. 123–146] is generalized for a set of banks with mutual interbank liabilities whose assets are driven by correlated Lévy processes with idiosyncratic and common components. The multi-dimensional problem is made tractable via a novel computational method, which generalizes the one-dimensional fractional partial differential equation method of Itkin [Efficient solution of backward jump-diffusion PIDEs with splitting and matrix exponentials, J. Comput. Financ. (2014), forthcoming. Available athttp://arxiv.org/abs/1304.3159] to the two- and three-dimensional cases. This method is unconditionally stable and of the second order of approximation in space and time; in addition, for many popular Lévy models it has linear complexity in each dimension. Marginal and joint survival probabilities for two and three banks with mutual liabilities are computed. The effects of mutual liabilities are discussed, and numerical examples are given to illustrate these effects. [ABSTRACT FROM PUBLISHER]

Themagnetodynamic Maxwell system given in its potential and space/time formulation is a popular model considered in the engineering community. We establish existence of strong solutions with the help of the theory of Showalter on degenerated parabolic problems; using energy estimates, existence of weak solutions are also deduced. [ABSTRACT FROM PUBLISHER]

We construct matrix-valued covariance functions and in ℝ2 and ℝ3, starting from an arbitrary scalar-valued variogram. It is shown that sufficiently smooth random vector fields (RVFs) with these covariance functions have divergence-free and curl-free sample paths, respectively. Conversely, essentially all models with such sample paths can be obtained via our construction. Extensions to space-time RVFs are possible. RVFs with divergence-free and curl-free sample paths can be utilised in meteorological applications e.g. for modelling and interpolating wind fields. [ABSTRACT FROM AUTHOR]

This review considers the hard problem of interstellar travel: overcoming fundamental limits set by the nature of space and time. The prospects for a solution to this problem are discussed in terms of the mathematical form of extensions to the classical equations of electrodynamics and general relativity, extensions which offer some prospect of faster-than-light interstellar travel with terrestrial engineering. This is tantamount to the electromagnetic control of gravity. Extensions are considered which preserve invariance under general coordinate transformations, but which relax Lorentz invariance in the limit of flat spacetimes. Such extensions describe undiscovered couplings between gravity and electromagnetism, and can be understood to unify them at the classical level. Of course, only extensions consistent with past tests of Lorentz invariance are contemplated. Among the suite of effects which arises from coupling between gravity and electromagnetism, at least two are of interest for faster-than-light travel. One is a non-Lorentzian invariant interval with its prospect of spacelike geodesics and a corresponding relaxation of the limiting speed of light. The second effect is control of the coupling constant for mass-energy to warp spacetime, which would seem to be necessary to allow terrestrial engineering of interesting space warps, such as wormholes or Alcubierre warps. Both effects are mediated by as-yet-undiscovered force fields, perhaps just a single scalar field. New forces in the equations of motion, and new sources of stress-energy in the Einstein equations, are auxiliary e ects which may be of interest for falsifying such extensions to general relativity ?? and electrodynamics. An example theory is presented which exhibits such extensions to the laws of gravity and electromagnetism: five-dimensional general relativity, developed between 1920 and 1960. In this theory, the faster-than-light limiting speed and the control of the coupling constant, as well as the extra forces in the equations of motion and the extra stress-energy source, all originate from a single scalar field. There is a particularly alluring identification of electric charge as a sort of momentum in the fifth dimension. It can be perilous to speculate about undiscovered physics, but the discoveries contemplated here will apparently be necessary if our civilization, or any civilization, is to reach the stars and explore the galaxy. [ABSTRACT FROM AUTHOR]

In our recent book (Abraham and Roy 2010) we have repurposed a mathematical model for the quantum vacuum as a model of consciousness. In this model, discrete space and time are derived from a discrete cellular dynamical network. As our model is essentially atomistic, we included in our book a short support chapter on atomism. In this aticle we expand on the few pages of that chapter devoted to the history of atomism, to place the current revival of atomism in a larger context. [ABSTRACT FROM PUBLISHER]

Space-time correlation modelling is one of the crucial steps of traditional structural analysis, since space-time models are used for prediction purposes. A comparative study among some classes of space-time covariance functions is proposed. The relevance of choosing a suitable model by taking into account the characteristic behaviour of the models is proved by using a space-time data set of ozone daily averages and the flexibility of the product-sum model is also highlighted through simulated data sets. [ABSTRACT FROM AUTHOR]

Two aspects of New Economic Geography models are often singled out for criticism, especially by geographers: the treatment of geography, typically as a pre-given, fixed and highly idealized abstract geometric space; and the treatment of history, typically as 'logical' time (the movement to equilibrium in a model's solution space) rather than real history. In this paper we examine the basis for these criticisms, and explore how far and in what ways NEG models might be made more credible with respect to their representation of geography and history, and particularly whether and to what extent the work of geographers themselves provides some insights in this regard. We argue that the conceptualization of space and time is in fact a challenge for both NEG theorists and economic geographers, and that, notwithstanding their ontological and epistemological differences, both groups would benefit from an interchange of ideas on this front. Reinventer les (nouveaux) modeles de geographie economique: comment prendre la geographie et l'histoire plus au serieux Resume Deux aspects particuliers des modeles de la nouvelle geographie economique sont souvent l'objet de critiques, notamment de la part des geographes, a savoir: le traitement de la geographie, generalement comme un espace geometrique abstrait predetermine, fixe et extremement idealise, et le traitement de l'histoire, generalement comme un creneau 'logique' (un mouvement vers l'equilibre dans un espace a solution du modele) et non pas comme l'histoire reelle. Dans la presente communication, nous nous penchons sur le fondement de ces critiques, et nous examinons dans quelle mesure les modeles de la NEG pourraient devenir plus plausibles sur le plan de la facon dont ils representent la geographie et l'histoire, notamment si le travail des geographes apporte de nouveaux elements sur cette question, et dans quelle mesure. Nous soutenons que la conceptualisation de l'espace et du temps constitue, en fait, un defi tant pour les theoriciens de la NEG que pour les geographes economiques, et qu'au-dela de leurs differences ontologiques et epistemologiques, un echange d'idees sur ce sujet serait benefique pour ces deux groupes. Reconsideracion de modelos de (Nueva) Geografia Economica: Tomando mas en serio la geografia y la historia Extracto A menudo, existen dos aspectos particulares de los modelos de Nueva Geografia Economica que reciben criticas, especialmente por parte de los geografos: el tratamiento de la geografia, tipicamente como un espacio geometrico abstracto altamente idealizado, fijo y predeterminado; y, el tratamiento de la historia, tipicamente como un tiempo 'logico' (el movimiento hacia el equilibrio en el espacio de solucion de un modelo), en lugar de como historia real. En este estudio examinamos la base de estas criticas y exploramos hasta que punto y de que formas, los modelos NEG podrian hacerse mas creibles con respecto a su representacion de la geografia e historia, y particularmente, si, y hasta que punto el trabajo de los geografos mismos proporciona algun tipo de vision interna en esta cuestion. Discutimos que la conceptualizacion del espacio y el tiempo es, de hecho, un reto para los teoricos NEG y los geografos economicos, y que, independientemente de sus diferencias ontologicas y epistemologicas, ambos grupos se beneficiarian de un intercambio de ideas en este campo. [image omitted] [ABSTRACT FROM AUTHOR]

Classic time geography is powerful but rigid, admitting only uniform travel velocities. Computational time geographic methods that resolve the uniform velocity assumption through transportation networks or isochrones only partially address this weakness and do not have a rigorous theoretical foundation. This article develops an analytical time geographic theory for the case where travel velocities vary continuously across space. Using the continuous transportation or “urban fields” tradition in quantitative geography and regional science, this article formulates analytical definitions of the space-time path and prism for the case where unobserved components are characterized by minimum cost curves through an inverse velocity field rather than straight line segments through a uniform velocity plane. This provides a geometrically and visually oriented approach to capturing complex velocities that complements existing methods. Time geographic fields also generalize time geography as the classic and isochrone versions are special cases; these now have a rigorous analytical foundation. It also can extend the network approach by treating links as regions with continuously varying velocities. Time geographic fields are also useful for nonnetwork-constrained phenomena such as movement through terrain, water, and air. This article illustrates the approach using a computational implementation based on a lattice approximation. [ABSTRACT FROM AUTHOR]

Constraint-based models and models constructing accessibility measures mainly focus on single agents having only one available transport mode. However, numerous cases exist where multiple agents or groups of individuals with different available transport modes want to participate in a joint activity at a certain location. The aim of this paper is to provide new insights into representing and reasoning about feasible space-time opportunities for multiple agents. Relying on concepts of time geography, we propose a conceptual framework in order to determine interaction spaces for groups of individuals. Besides availability of means of transport and the locations of each individual, minimum activity duration and opening hours of opportunities are taken into account. The reasoning about space and time is visualized in three dimensions using a hybrid (CAD/GIS) system. [ABSTRACT FROM AUTHOR]

A note is presented on tsunami bore front. This tsunami bore front is an old dynamical problem but also a new problem to be understood. The tsunami event on 2004 December 26 has raised this is an urgent problem. The author introduces here a model in order to see a hydrodynamical specific property of the tsunami bore front. This modeling gives us a new understanding about what mechanics is for the interested tsunami bore front, especially, around a coastal zone. This work adds a new understanding about mechanics of water motions as the tsunamis generated by the earthquake undersea at a distant area from the coast. The model in this work points out a specific transitional pattern as a function of time and space of tsunami bore front. This modeling gives what is essential at considering tsunami bore front. [ABSTRACT FROM AUTHOR]

Opinion. Presents the authors' view on dataset for studying the spatial variation of ozone levels. Information about pseudoreplicates; Advantages of space-time datasets.

A three-stage iterative procedure for building space-time models is presented. These models fall into the general class of STARIMA models and are characterized by autoregressive and moving average terms lagged in both time and space. This model class collapses into the ARIMA model class in the absence of spatial correlation. The theoretical properties of STARIMA models are presented and the model building procedure is described and illustrated by a substantive example. [ABSTRACT FROM AUTHOR]

Opinion. Presents the author's view on Carroll and colleagues' paper that considers ambient ozone pollution in Harris County, Texas between 1980 and 1993. Some features of the space-time model that require discussion; Comments about styles of space-time modelling.