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| 2014Sergio Conti and Geog Dolzmann
Relaxation of a model energy for the cubic to tetragonal phase transformation in two dimensions
Math. Models. Metods App. Sci., 24(14): 2929-2942 2014
http://dx.doi.org/10.1142/S0218202514500419
Abstract: We consider a two-dimensional problem in nonlinear elasticity which corresponds to the cubic-to-tetragonal phase transformation. Our model is frame invariant and the energy density is given by the squared distance from two potential wells. We obtain the quasiconvex envelope of the energy density and therefore the relaxation of the variational problem. Our result includes the constraint of positive determinant. |
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| Patrick Diehl and Marc A. Schweitzer
Efficient Neighbor Search for Particle Methods on GPUs
In M. Griebel and M. A. Schweitzer, editor, Meshfree Methods for Partial Differential Equations VII, Volume 100 of Lecture Notes in Computational Science and Engineering
Chapter 5, page 81-95.
Publisher: Springer International
2014
http://dx.doi.org/10.1007/978-3-319-06898-5_5
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| Landry Fokoua Djodom, Sergio Conti and Michael Ortiz
Optimal Scaling in Solids undergoing Ductile Fracture by Void Sheet Formation
Arch. Ration. Mech. Anal., 212(1): 331-357 2014
http://dx.doi.org/10.1007/s00205-013-0687-8
Abstract: This work is concerned with the derivation of optimal scaling laws, in the sense of matching lower and upper bounds on the energy, for a solid undergoing ductile fracture. The specific problem considered concerns a material sample in the form of an infinite slab of finite thickness subjected to prescribed opening displacements on its two surfaces. The solid is assumed to obey deformation-theory of plasticity and, in order to further simplify the analysis, we assume isotropic rigid-plastic deformations with zero plastic spin. When hardening exponents are given values consistent with observation, the energy is found to exhibit sublinear growth. We regularize the energy through the addition of nonlocal energy terms of the strain-gradient plasticity type. This nonlocal regularization has the effect of introducing an intrinsic length scale into the energy. Under these assumptions, ductile fracture emerges as the net result of two competing effects: whereas the sublinear growth of the local energy promotes localization of deformation to failure planes, the nonlocal regularization stabilizes this process, thus resulting in an orderly progression towards failure and a well-defined specific fracture energy. The optimal scaling laws derived here show that ductile fracture results from localization of deformations to void sheets, and that it requires a well-defined energy per unit fracture area. In particular, fractal modes of fracture are ruled out under the assumptions of the analysis. The optimal scaling laws additionally show that ductile fracture is cohesive in nature, that is, it obeys a well-defined relation between tractions and opening displacements. Finally, the scaling laws supply a link between micromechanical properties and macroscopic fracture properties. In particular, they reveal the relative roles that surface energy and microplasticity play as contributors to the specific fracture energy of the material. |
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| Landry Fokoua Djodom, Sergio Conti and Michael Ortiz
Optimal scaling laws for ductile fracture derived from strain-gradient microplasticity
J. Mech. Phys. Solids, 62: 295-311 2014
http://dx.doi.org/10.1016/j.jmps.2013.11.002
Abstract: This work is concerned with the derivation of optimal scaling laws, in the sense of matching lower and upper bounds on the energy, for a solid undergoing ductile fracture. The specific problem considered concerns a material sample in the form of an infinite slab of finite thickness subjected to prescribed opening displacements on its two surfaces. The solid is assumed to obey deformation-theory of plasticity and, in order to further simplify the analysis, we assume isotropic rigid-plastic deformations with zero plastic spin. When hardening exponents are given values consistent with observation, the energy is found to exhibit sublinear growth. We regularize the energy through the addition of nonlocal energy terms of the strain-gradient plasticity type. This nonlocal regularization has the effect of introducing an intrinsic length scale into the energy. Under these assumptions, ductile fracture emerges as the net result of two competing effects: whereas the sublinear growth of the local energy promotes localization of deformation to failure planes, the nonlocal regularization stabilizes this process, thus resulting in an orderly progression towards failure and a well-defined specific fracture energy. The optimal scaling laws derived here show that ductile fracture results from localization of deformations to void sheets, and that it requires a well-defined energy per unit fracture area. In particular, fractal modes of fracture are ruled out under the assumptions of the analysis. The optimal scaling laws additionally show that ductile fracture is cohesive in nature, that is, it obeys a well-defined relation between tractions and opening displacements. Finally, the scaling laws supply a link between micromechanical properties and macroscopic fracture properties. In particular, they reveal the relative roles that surface energy and microplasticity play as contributors to the specific fracture energy of the material. |
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| Miguel Escobedo and Juan J. L. Velázquez
Finite time blow-up and condensation for the bosonic Nordheim equation
Inventiones mathematicae, 200(3): 761-847 2014
http://dx.doi.org/10.1007/s00222-014-0539-7
Abstract: The homogeneous bosonic Nordheim equation is a kinetic equation describing the dynamics of the distribution of particles in the space of moments for a homogeneous, weakly interacting, quantum gas of bosons. We show the existence of classical solutions of the homogeneous bosonic Nordheim equation that blow up in finite time. We also prove finite time condensation for a class of weak solutions of the kinetic equation. |
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| Miguel Escobedo and Juan J. L. Velázquez
On the Blow Up and Condensation of Supercritical Solutions of the Nordheim Equation for Bosons
Communications in Mathematical Physics, 330(1): 331-365 2014
http://dx.doi.org/10.1007/s00220-014-2034-9
Abstract: In this paper we prove that the solutions of the isotropic, spatially homogeneous Nordheim equation for bosons with bounded initial data blow up in finite time in the L ∞ norm if the values of the energy and particle density are in the range of values where the corresponding equilibria contain a Dirac mass. We also prove that, in the weak solutions, whose initial data are measures with values of particle and energy densities satisfying the previous condition, a Dirac measure at the origin forms in finite time. |
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| Patrik L. Ferrari and René Frings
Perturbed GUE Minor Process and Warren’s Process with Drifts
J. Stat. Phys., 154(1): 356-377 2014
http://dx.doi.org/10.1007/s10955-013-0887-5
Abstract: We consider the minor process of (Hermitian) matrix diffusions with constant diagonal drifts. At any given time, this process is determinantal and we provide an explicit expression for its correlation kernel. This is a measure on the Gelfand–Tsetlin pattern that also appears in a generalization of Warren’s process (Electron. J. Probab. 12:573–590, 2007), in which Brownian motions have level-dependent drifts. Finally, we show that this process arises in a diffusion scaling limit from an interacting particle system in the anisotropic KPZ class in 2+1 dimensions introduced in Borodin and Ferrari (Commun. Math. Phys., 2008). Our results generalize the known results for the zero drift situation. |
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| Irene Fonseca, Aldo Pratelli and Barbara Zwicknagl
Shapes of Epitaxially Grown Quantum Dots
Archive for Rational Mechanics and Analysis, 214(2): 359-401 2014
http://dx.doi.org/10.1007/s00205-014-0767-4
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| Fabian Franzelin, Patrick Diehl and Dirk Pflüger
Non-intrusive Uncertainty Quantification with Sparse Grids for Multivariate Peridynamic Simulations
In M. Griebel and M. A. Schweitzer, editor, Meshfree Methods for Partial Differential Equations VII, Volume 100 of Lecture Notes in Computational Science and Engineering
Chapter 7, page 115-143.
Publisher: Springer
2014
http://dx.doi.org/10.1007/978-3-319-06898-5_7
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| Véronique Gayrard and Adéla Švejda
Convergence of clock processes on infinite graphs and aging in Bouchaud's asymmetric trap model on $\mathbbZ^d$
Lat. Am. J. Probab. Math. Stat., 11(2): 78-822 2014
http://alea.impa.br/articles/v11/11-35.pdf
Abstract: Using a method developed by Durrett and Resnick, [23], we establish general criteria for the convergence of properly rescaled clock processes of random dynamics in random environments on infinite graphs. This extends the results of Gayrard, [27], Bovier and Gayrard, [20], and Bovier, Gayrard, and Svejda, [21], and gives a unified framework for proving convergence of clock processes. As a first application we prove that Bouchaud's asymmetric trap model on \(\mathbb{Z}^d\) exhibits a normal aging behavior for all \(d \geq 2\). Namely, we show that certain two-time correlation functions, among which the classical probability to find the process at the same site at two time points, converge, as the age of the process diverges, to the distribution function of the arcsine law. As a byproduct we prove that the fractional kinetics process ages. |
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| Michael Griebel, Jan Hamaekers and Frederik Heber
A bond order dissection ANOVA approach for efficient electronic structure calculations
In Extraction of Quantifiable Information from Complex Systems, Volume 102 of Lecture Notes in Computational Science and Engineering
Chapter 11, page 211-235.
Publisher: Springer International
2014
http://dx.doi.org/10.1007/978-3-319-08159-5
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| Michael Griebel and Alexander Hullmann
Dimensionality Reduction of High-Dimensional Data with a NonLinear Principal Component Aligned Generative Topographic Mapping
SIAM J. Sci. Comput., 36(3): A1027-A1047 2014
http://dx.doi.org/10.1137/130931382
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| Michael Griebel and Helmut Harbrecht
On the convergence of the combination technique
In Sparse grids and Applications, Volume 97 of Lecture Notes in Computational Science and Engineering
page 55-74.
2014
http://dx.doi.org/10.1007/978-3-319-04537-5_3
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| Michael Griebel and Alexander Hullmann
A Sparse Grid Based Generative Topographic Mapping for the Dimensionality Reduction of High-Dimensional Data
In Modeling, Simulation and Optimization of Complex Processes - HPSC 2012
page 51-62.
2014
http://dx.doi.org/10.1007/978-3-319-09063-4_5
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| Michael Griebel and Jens Oettershagen
Dimension-adaptive sparse grid quadrature for integrals with boundary singularities
In Sparse grids and Applications, Volume 97 of Lecture Notes in Computational Science and Engineering
page 109-136.
2014
http://dx.doi.org/10.1007/978-3-319-04537-5_5
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| Michael Griebel and Jan Hamaekers
Fast Discrete Fourier Transform on Generalized Sparse Grids
In Sparse grids and Applications, Lecture Notes in Computational Science and Engineering Vol. 97, Springer, Volume 97 of Lecture Notes in Computational Science and Engineering
page 75-108.
2014
http://dx.doi.org/10.1007/978-3-319-04537-5_4
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| Thomas Hangelbroek, Francis J. Narcowich, Christian Rieger and Joseph D. Ward
An inverse theorem on bounded domains for meshless methods using localized bases
2014
http://arxiv.org/pdf/1406.1435v1
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| Aicke Hinrichs and Jens Oettershagen
Optimal point sets for quasi-Monte Carlo integration of bivariate periodic functions with bounded mixed derivatives
2014
http://arxiv.org/pdf/1409.5894v1
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| Martin Huesmann
Optimal transport between random measures
Annales de l’Institut Henri Poincaré (B) 2014
http://arxiv.org/abs/1206.3672
Abstract: We study couplings q∙ of two equivariant random measures λ∙ and μ∙ on a Riemannian manifold (M,d,m). Given a cost function we ask for minimizers of the mean transportation cost per volume. In case the minimal/optimal cost is finite and λω≪m we prove that there is a unique equivariant coupling minimizing the mean transportation cost per volume. Moreover, the optimal coupling is induced by a transportation map, q∙=(id,T)∗λ∙. We show that the optimal transportation map can be approximated by solutions to classical optimal transportation problems on bounded regions. In case of Lp−cost the optimal transportation cost per volume defines a metric on the space of equivariant random measure with unit intensity. |
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| Herbert Koch, Hart F. Smith and Daniel Tataru
Sharp $L^p$ bounds on spectral clusters for Lipschitz metrics
Amer. J. Math., 136(6): 1629-1663 2014
http://dx.doi.org/10.1353/ajm.2014.0039
Abstract: We establish Lp bounds on L2 normalized spectral clusters for self-adjoint elliptic Dirichlet forms with Lipschitz coefficients. In two dimensions we obtain best possible bounds for all 2 ≤ p ≤ ∞, up to logarithmic losses for 6 < p ≤ 8. In higher dimensions we obtain best possible bounds for a limited range of p. |
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