The Experts below are selected from a list of 206247 Experts worldwide ranked by ideXlab platform
Martin Bach - One of the best experts on this subject based on the ideXlab platform.
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Open Guided Waves: online platform for ultrasonic guided wave measurements:
Structural Health Monitoring-an International Journal, 2018Co-Authors: Jochen Moll, Jens Kathol, Claus-peter Fritzen, Maria Moix-bonet, Marcel Rennoch, Michael Koerdt, Axel S. Herrmann, Markus G. R. Sause, Martin BachAbstract:Ultrasonic guided waves have been used successfully in structural health monitoring systems to detect damage in isotropic and composite materials with simple and Complex Geometry. A limitation of c...
David Andriot - One of the best experts on this subject based on the ideXlab platform.
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string theory flux vacua on twisted tori and generalized Complex Geometry
2010Co-Authors: David AndriotAbstract:This thesis is devoted to the study of flux vacua of string theory, with the ten-dimensional space-time split into a four-dimensional maximally symmetric space-time, and a six-dimensional internal manifold M, taken to be a solvmanifold (twisted torus). Such vacua are of particular interest when trying to relate string theory to supersymmetric (SUSY) extensions of the standard model of particles, or to cosmological models. For SUSY solutions of type II supergravities, allowing for fluxes on M helps to solve the moduli problem. Then, a broader class of manifolds than just the Calabi-Yau can be considered for M, and a general characterization is given in terms of Generalized Complex Geometry: M has to be a Generalized Calabi-Yau (GCY). A subclass of solvmanifolds have been proven to be GCY, so we look for solutions with such M. To do so, we use an algorithmic resolution method. Then we focus on specific new solutions: those admitting an intermediate SU(2) structure. A transformation named the twist is then discussed. It relates solutions on torus to solutions on solvmanifolds. Working out constraints on the twist to generate solutions, we can relate known solutions, and find a new one. We also use the twist to relate flux vacua of heterotic string. Finally we consider ten-dimensional de Sitter solutions. Looking for such solutions is difficult, because of several problems among which the breaking of SUSY. We propose an ansatz for SUSY breaking sources which helps to overcome these difficulties. We give an explicit solution on a solvmanifold, and discuss partially its four-dimensional stability.
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new supersymmetric flux vacua of type ii string theory and generalized Complex Geometry
Protein Science, 2009Co-Authors: David AndriotAbstract:We study Minkowski supersymmetric flux vacua of type II string theory. Based on the work by M. Grana, R. Minasian, M. Petrini and A. Tomasiello, we briefly explain how to reformulate things in terms of Generalized Complex Geometry, which appears to be a natural framework for these compactifications. In particular, it provides a mathematical characterization of the internal manifold, and one is then able to find new solutions, which cannot be constructed as usual via T-dualities from a warped T6 solut ion. Furthermore, we discuss how, thanks to a specific change of variables, one can ease the resolution of the orientifold projection constraints pointed out by P. Koerber and D. Tsimpis. One is then able to find new solutions with intermediate SU(2) structure. This contribution is mainly based on references [1] and [2]. Due to size constraints, several details and some citations are missing. For completeness, please have a look at [1].
Joel H Ferziger - One of the best experts on this subject based on the ideXlab platform.
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a ghost cell immersed boundary method for flow in Complex Geometry
Journal of Computational Physics, 2003Co-Authors: Yuheng Tseng, Joel H FerzigerAbstract:An efficient ghost-cell immersed boundary method (GCIBM) for simulating turbulent flows in Complex geometries is presented. A boundary condition is enforced through a ghost cell method. The reconstruction procedure allows systematic development of numerical schemes for treating the immersed boundary while preserving the overall second-order accuracy of the base solver. Both Dirichlet and Neumann boundary conditions can be treated. The current ghost cell treatment is both suitable for staggered and non-staggered Cartesian grids. The accuracy of the current method is validated using flow past a circular cylinder and large eddy simulation of turbulent flow over a wavy surface. Numerical results are compared with experimental data and boundary-fitted grid results. The method is further extended to an existing ocean model (MITGCM) to simulate geophysical flow over a three-dimensional bump. The method is easily implemented as evidenced by our use of several existing codes.
Jochen Moll - One of the best experts on this subject based on the ideXlab platform.
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Open Guided Waves: online platform for ultrasonic guided wave measurements:
Structural Health Monitoring-an International Journal, 2018Co-Authors: Jochen Moll, Jens Kathol, Claus-peter Fritzen, Maria Moix-bonet, Marcel Rennoch, Michael Koerdt, Axel S. Herrmann, Markus G. R. Sause, Martin BachAbstract:Ultrasonic guided waves have been used successfully in structural health monitoring systems to detect damage in isotropic and composite materials with simple and Complex Geometry. A limitation of c...
Bernd Siebert - One of the best experts on this subject based on the ideXlab platform.
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From real affine Geometry to Complex Geometry
Annals of Mathematics, 2011Co-Authors: Mark Gross, Bernd SiebertAbstract:We construct from a real ane manifold with singularities (a tropical manifold) a degeneration of Calabi-Yau manifolds. This solves a fundamental problem in mirror symmetry. Furthermore, a striking feature of our approach is that it yields an explicit and canonical order-by-order description of the degeneration via families of tropical trees. This gives complete control of the B-model side of mirror symmetry in terms of tropical Geometry. For example, we expect that our deformation parameter is a canonical coordinate, and expect period calculations to be expressible in terms of tropical curves. We anticipate this will lead to a proof of mirror symmetry via tropical methods.
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From real affine Geometry to Complex Geometry
arXiv: Algebraic Geometry, 2007Co-Authors: Mark Gross, Bernd SiebertAbstract:We construct from a real affine manifold with singularities (a tropical manifold) a degeneration of Calabi-Yau manifolds. This solves a fundamental problem in mirror symmetry. Furthermore, a striking feature of our approach is that it yields an explicit and canonical order-by-order description of the degeneration via families of tropical trees. This gives complete control of the B-model side of mirror symmetry in terms of tropical Geometry. For example, we expect our deformation parameter is a canonical coordinate, and expect period calculations to be expressible in terms of tropical curves. We anticipate this will lead to a proof of mirror symmetry via tropical methods. This paper is the key step of the program we initiated in math.AG/0309070.
