{"title":"General Fractal Conservation Laws Arising from a Model of Detonations in Gases","authors":"M. Alfaro, J. Droniou","doi":"10.1093/AMRX/ABR015","DOIUrl":"https://doi.org/10.1093/AMRX/ABR015","url":null,"abstract":"We consider a model of cellular detonations in gases. They consist in conservation laws with a non-local pseudo-differential operator whose symbol is asymptotically |ξ|λ, where 0 < λ ≤ 2; it can be decomposed as the λ/2 fractional power of the Laplacian plus a convolution term. After defining the notion of entropy solution, we prove the well-posedness in the L∞ framework. In the case where 1 < λ ≤ 2 we also prove a regularizing effect. In Appendix, we show that the assumptions made to perform the mathematical study are satisfied by the considered physical model of detonations.","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"16 1","pages":"127-151"},"PeriodicalIF":0.0,"publicationDate":"2011-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87152718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Resonant Uniqueness of Radial Semiclassical Schrödinger Operators","authors":"K. Datchev, Hamid Hezari","doi":"10.1093/amrx/abr017","DOIUrl":"https://doi.org/10.1093/amrx/abr017","url":null,"abstract":"We prove that radial, monotonic, superexponentially decaying potentials in R^n, n greater than or equal to 1 odd, are determined by the resonances of the associated semiclassical Schrodinger operator among all superexponentially decaying potentials in R^n.","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"53 1","pages":"105-113"},"PeriodicalIF":0.0,"publicationDate":"2011-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78745601","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Asymptotic Expansion of the Homogenized Matrix in Two Weakly Stochastic Homogenization Settings","authors":"Ronan Costaouec","doi":"10.1093/AMRX/ABR011","DOIUrl":"https://doi.org/10.1093/AMRX/ABR011","url":null,"abstract":"This article studies some numerical approximations of the homogenized matrix for stochastic linear elliptic partial differential equations in divergence form. We focus on the case when the underlying random field is a small perturbation of a reference periodic tensor. The size of such a perturbation is encoded by a real parameter eta. In this case, it has already been theoretically shown in the literature that the exact homogenized matrix possesses an expansion in powers of the parameter eta for both models considered in this article, the coefficients of which are deterministic. In practice, one cannot manipulate the exact terms of such an expansion. All objects are subjected to a discretization approach. Thus we need to derive a similar expansion for the approximated random homogenized matrix. In contrast to the expansion of the exact homogenized matrix, the expansion of the approximated homogenized matrix contains intrinsically random coefficients. In particular, the second order term is random in nature. The purpose of this work is to derive and study this expansion in function of the parameters of the approximation procedure (size of the truncated computational domain used, meshsize of the finite elements approximation).","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"63 1","pages":"76-104"},"PeriodicalIF":0.0,"publicationDate":"2011-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83163669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"DNA Unzipping via Stopped Birth and Death Processes with Unknown Transition Probabilities","authors":"P. Andreoletti, R. Diel","doi":"10.1093/AMRX/ABS008","DOIUrl":"https://doi.org/10.1093/AMRX/ABS008","url":null,"abstract":"In this paper, we provide an alternative approach to the works of the physicists S. Cocco and R. Monasson about a model of DNA molecules. The aim was to predict the sequence of bases by mechanical stimulations. The model described by the physicists is a stopped birth and death process with unknown transition probabilities. We consider two models, a discrete in time and a continuous in time, as general as possible. We show that explicit formula can be obtained for the probability to be wrong for a given estimator, and apply it to evaluate the quality of the prediction. Also we add some generalizations comparing to the initial model allowing us to answer some questions asked by the physicists.","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"22 1","pages":"184-208"},"PeriodicalIF":0.0,"publicationDate":"2011-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80398115","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Convergence to Homogenized or Stochastic Partial Differential Equations","authors":"G. Bal","doi":"10.1093/AMRX/ABR006","DOIUrl":"https://doi.org/10.1093/AMRX/ABR006","url":null,"abstract":"We consider the behavior of solutions to parabolic equations with large, highly oscillatory, possibly time dependent, random potential with Gaussian statistics. The Gaussian potential fluctuates in the spatial variables and possibly in the temporal variable. We seek the limit of the solution to the parabolic equation as the scale ε at which the random medium oscillates converges to zero. Depending on spatial dimension and on the decorrelation properties of the Gaussian potential, we show that the solution converges, as ε tends to 0, either to the solution of a deterministic, homogenized, equation with negative effective medium potential or to the solution of a stochastic partial differential equation with multiplicative noise that should be interpreted as a Stratonovich integral. The transition between the deterministic and stochastic limits depends on the elliptic operator in the parabolic equation and on the decorrelation properties of the random potential. In the setting of convergence to a deterministic solution, we characterize the random corrector, which asymptotically captures the stochasticity in the solution. Such models can be used to calibrate upscaling schemes that aim at understanding the influence of microscopic structures in macroscopic calculations.","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"270 1","pages":"215-241"},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83714094","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alex Chen, Todd Wittman, A. Tartakovsky, A. Bertozzi
{"title":"Efficient Boundary Tracking Through Sampling","authors":"Alex Chen, Todd Wittman, A. Tartakovsky, A. Bertozzi","doi":"10.1093/AMRX/ABR002","DOIUrl":"https://doi.org/10.1093/AMRX/ABR002","url":null,"abstract":"The proposed algorithm for image segmentation is inspired by an algorithm for autonomous environmental boundary tracking. The algorithm relies on a tracker that traverses a boundary between regions in a sinusoidal-like path. Boundary tracking is done by efficiently sampling points, resulting in a significant savings in computation time over many other segmentation methods. For noisy images, the traversed path is modeled as a change-point detection problem between two states. Change-point detection algorithms such as Page’s cumulative sum procedure are adapted in conjunction with other methods to handle a high level of noise. A modification for the multiple-region case is also presented as a hybrid of a topology-detecting segmentation algorithm and boundary tracking. Applications to high resolution images and large data sets such as hyperspectral are of particular interest. Irregularly shaped boundaries such as fractals are also treated at very fine detail along with accompanying fractal dimension calculations, which follow naturally from the boundary tracking data.","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"12 1","pages":"182-214"},"PeriodicalIF":0.0,"publicationDate":"2011-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83622291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Radial Spreading of a Surfactant on a Thin Liquid Film","authors":"E. Peterson, M. Shearer","doi":"10.1093/AMRX/ABQ015","DOIUrl":"https://doi.org/10.1093/AMRX/ABQ015","url":null,"abstract":"When a surfactant is placed on a layer of fluid, it reduces surface tension locally, creating a surface stress imbalance that sets the fluid in motion. The lubrication approximation is applied to axisymmetric spreading, yielding a coupled system of nonlinear partial differential equation for the height of the fluid free surface and the distribution of the surfactant. For a simplified system ignoring the effects of gravity and capillarity, as well as diffusion of surfactant molecules, the location of the surfactant can be tracked numerically. The free surface height converges quickly to a similarity form [Jensen, “Self-similar, surfactant-driven flows.” Physics of Fluids 6 (1994): 1084–94] away from the origin. Near the origin, a self-similar solution is identified, but it differs qualitatively from long-time numerical solutions. Including nonself-similar terms in an expansion around the origin corrects this inconsistency.","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"35 1","pages":"1-22"},"PeriodicalIF":0.0,"publicationDate":"2010-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86558123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Annular Bose-Einstein Condensates in the Lowest Landau Level","authors":"N. Rougerie","doi":"10.1093/AMRX/ABQ020","DOIUrl":"https://doi.org/10.1093/AMRX/ABQ020","url":null,"abstract":"A rotating superuid such as a Bose-Einstein condensate is usually described by the GrossPitaevskii (GP) model. An important issue is to determine from this model the properties of the quantized vortices that a superuid nucleates when set into rotation. In this paper we address the minimization of a two dimensional GP energy functional describing a rotating annular Bose-Einstein condensate. In a certain limit it is physically relevant to restrict the minimization to the LowestLandau-Level, that is the rst eigenspace of the Ginzburg-Landau operator. Taking the particular structure of this space into account we obtain theoretical results concerning the vortices of the condensate. We also compute the vortices’ locations by a numerical minimization procedure. We nd that they lie on a distorted lattice and that multiple quantized vortices appear in the central hole of low matter density.","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"11 1","pages":"95-121"},"PeriodicalIF":0.0,"publicationDate":"2010-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85036667","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Phase Transitions in a Relaxation Model of Mixed Type with Periodic Boundary Condition","authors":"M. Gander, Ming Mei, E. Schmidt","doi":"10.1093/AMRX/ABM006","DOIUrl":"https://doi.org/10.1093/AMRX/ABM006","url":null,"abstract":"We study the asymptotic behavior of solutions for a 2×2 relaxation model of mixed type with periodic initial and boundary conditions. We prove that the asymptotic behavior of the solutions and their phase transitions are dependent on the location of the initial data and the size of the viscosity. If the average of the initial data is in the hyperbolic region and the initial data does not deviate too much from its average,we prove that there exists a unique global solution and that it converges time-asymptotically to the average in the same hyperbolic region. No phase transition occurs after initial oscillations. If the average of the initial data is in the elliptic region and the initial data does not deviate too much from its average, and in addition if the viscosity is big, then the solution converges to the average in the same elliptic region, and does not exhibit phase transitions after initial oscillations. If, however, the viscosity is small, numerical evidence indicates that the solution oscillates across the hyperbolic and elliptic regions for all time, exhibiting phase transitions. In this case, we conjecture that the solution converges to an oscillatory standing wave (steady-state solution).","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"6 1","pages":"1-34"},"PeriodicalIF":0.0,"publicationDate":"2010-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84919779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Complete Solution of a Differential Game with Linear Dynamics and Bounded Controls","authors":"V. Glizer, V. Turetsky","doi":"10.1093/AMRX/ABM012","DOIUrl":"https://doi.org/10.1093/AMRX/ABM012","url":null,"abstract":"A differential game is an appropriate mathematical model for real-life control problems, which either involve many decision-makers or contain a high degree of uncertainties. There is a rich literature devoted to the theory of differential games (see e.g. [1–5]). A zero-sum finite-horizon differential game with linear dynamics and bounded controls was studied extensively in the literature, because of its considerable meaning both in theory and applications (see e.g. [6–10] and the references therein). Important applications of this game are: a pursuit-evasion problem (see e.g. [11–14]), an airplane landing problem under windshear conditions (see [15] and references therein), and some others. Different versions of this game were analyzed in the literature. A simple example with the ideal dynamics of the players was considered in [6]. The game with a first-order","PeriodicalId":89656,"journal":{"name":"Applied mathematics research express : AMRX","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2010-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84039019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}