Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 216 for “"Spacetime"”.
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Constructing quantum spacetime
… relative describes gravity as a dynamical spacetime, which is curved by matter and whose curvature determines the motion of matter. On the other hand we have quantum field theory, in form of the standard model of particle physics, where particles interact via the remaining interactions - …
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Conformal Properties of Spacetime
… of quantum gravity. In an asymptotically flat spacetime, this property, which we call the Penrose property, is satisfied if for any two endless timelike curves λ, ν in the same domain of outer dependence, there exists a future directed timelike curve from λ to ν. Penrose showed that this …
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Adaptive unstructured spacetime meshing for four-dimensional spacetime discontinuous Galerkin finite element methods
We describe the spacetime discontinuous Galerkin method, a new type of finite-element method which promises dramatic improvement in solution speed for hyperbolic problems. These methods require the generation of spacetime meshes that satisfy a special causality constraint. This work focuses on the …
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Spacetime meshing of stratified spaces for spacetime discontinuous Galerkin methods in arbitrary spatial dimensions
We introduce the spacetime discontinuous Galerkin method and motivate the need for supporting spacetime meshing on meshes comprised of multiple manifolds. We first discuss preliminary concepts behind simplices, simplicial complexes, and the generalization to oriented simplicies. Using these ideas, …
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Spacetime Meshing for Discontinuous Galerkin Methods
… to construct an unstructured simplicial spacetime mesh over an arbitrary simplicial space domain. Our algorithm is the first adaptive spacetime meshing algorithm suitable for efficient solution of nonlinear phenomena using spacetime discontinuous Galerkin finite element methods. Given a …
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Stochastic congruence equations for spacetime fluctuations
… the effects of curvature fluctuations on spacetime thermodynamics. This is done by examining the evolution equations for time-like and null congruences, and recasting them as stochastic differential equations. The purpose of viewing the congruence evolution equations as stochastic is in …
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Framing spacetime in the mapping of aerotory
… of the continuum of space and time, an entity of spacetime. However, when it comes to dominant modern measurement of maps, space and time are two discrete ideas. Unlike the ideology of solidity and isolation silently fueled by the modern approach to measurement, which is predicated on the autonomy …
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Geometric aspects of gauge and spacetime symmetries
… of these groups to physical properties of the spacetimes. We then make group deformation local, generalising deformed special relativity (DSR) by describing gravity as a gauge theory of the de Sitter group. We find that in our construction Minkowski space has a connection with torsion; physical …
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Obtaining the spacetime metric from cosmological observations
The Copernican principle asserts homogeneity on very large scales, however, this scale is still not well defined; and in reality homogeneity is assumed. Recent galaxy redshift surveys have brought in a large amount of cosmological data out to redshift 0.3 or more, that is now available for …
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Spacetime structure of the very early universe
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 1985.
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Noncommutative gauge theory and the kappa-deformed spacetime
Feldtheorien auf nichtkommutativen (NC) Raeumen werden untersucht als realistische Erweiterungen des Standardmodells der Elementarteilchenphysik. Vor allem werden zwei Modelle mit nicht vertauschenden operatorwertigen Koordinaten betrachtet: Kanonisch NC Raeume und der kappa-deformierte Raum. Diese …
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Asymptotically Safe Gravity: from spacetime foliation to cosmology
… gravity in terms of the geometric properties of spacetime. Nevertheless, the quantum nature of matter and the existence of regimes in which the classical description of gravity breaks down suggest that the short-distance behavior of spacetime may require a more fundamental quantum theory for the …
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Tensorial spacetime geometries and background-independent quantum field theory
Famously, Einstein read off the geometry of spacetime from Maxwell's equations. Today, we take this geometry that serious that our fundamental theory of matter, the standard model of particle physics, is based on it. However, it seems that there is a gap in our understanding if it comes to the …
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A Spacetime Discontinuous Galerkin Method for Hyperbolic Conservation Laws
The basic SDG approximation is a simple Bubnov-Galerkin projection that is not prone to global patterns of spurious oscillations. However, it does require stabilization to eliminate local overshoot and undershoot in the immediate vicinity of shocks and other discontinuous solution features. We …
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Analysis of a Spacetime Discontinuous Galerkin Method for Elastodynamics
We prove error estimates for the case of both element-wise and patch-wise causal partitions.
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Four-dimensional anisotropic mesh adaptation for spacetime numerical simulations
… solution features, a fully unstructured coupled spacetime approach has been shown to be useful in reducing the cost of the overall simulation. However, for the simulation of unsteady three-dimensional partial differential equations (PDEs), a four-dimensional mesh adaptation tool is needed. This …
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Tensorial spacetime geometries carrying predictive, interpretable and quantizable matter dynamics
… fields G on a smooth manifold M can serve as a spacetime structure? In the first part of this thesis, it is found that only a severely restricted class of tensor fields can provide classical spacetime geometries, namely those that can carry predictive, interpretable and quantizable matter …
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Colliding branes and formation of spacetime singularities in superstring theory.
A systematic study of space-times containing two timelike colliding branes is made, in the framework of 10-dimensional string theory. After developing the general formulas to describe such events, we study several classes of exact solutions and space-time singularities in both the (D+d)-dimensional …
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A Spacetime Discontinuous Galerkin Finite-Element Method for Elastodynamic Analysis
We use the new spacetime discontinuous Galerkin finite element model to investigate a series of elastodynamic problems in both one and two spatial dimensions. The first study focuses on the problems that exhibit discontinuities or shocks. The new method delivers high accurate results. The second …
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