37 research outputs found
I've Got the World on a Brane
This thesis treats several topics in the study of extra-dimensional models of
the world, concerning Heterotic M-Theory and the dynamics of branes. We
describe a reduction to five dimensions, over a Calabi-Yau manifold, of an
improved version of Heterotic M-Theory, which is valid to all orders in the
gravitational coupling. This provides a starting point for considering the
consequences of the improved theory for the very fruitful phenomenology of the
original. We investigate the singularities formed by the collision of
gravitating branes in scalar field theory. By considering the asymptotic
structure of the spacetime, the properties of the horizons formed and the
growth of the curvature we argue that the singularity is not a black brane, as
one might have expected, but rather a big crunch. Finally, we construct a
restricted class of multi-galileon theories as braneworld models with
codimension greater than one, developing in the process some of the formalism
needed for the general construction.Comment: PhD Thesis, University of Nottingha
Colliding branes and big crunches
We examine the global structure of colliding domain walls in AdS spacetime
and come to the conclusion that singularities forming from such collisions are
of the big-crunch type rather than that of a black brane.Comment: 5 pages, 6 figure
Neoclassical flows in deuterium-helium plasma density pedestals
In tokamak transport barriers, the radial scale of profile variations can be
comparable to a typical ion orbit width, which makes the coupling of the
distribution function across flux surfaces important in the collisional
dynamics. We use the radially global steady-state neoclassical {\delta}f code
Perfect to calculate poloidal and toroidal flows, and radial fluxes, in the
pedestal. In particular, we have studied the changes in these quantities as the
plasma composition is changed from a deuterium bulk species with a helium
impurity to a helium bulk with a deuterium impurity, under specific profile
similarity assumptions. The poloidally resolved radial fluxes are not
divergence-free in isolation in the presence of sharp radial profile
variations, which leads to the appearance of poloidal return-flows. These flows
exhibit a complex radial-poloidal structure that extends several orbit widths
into the core and is sensitive to abrupt radial changes in the ion temperature
gradient. We find that a sizable neoclassical toroidal angular momentum
transport can arise in the radially global theory, in contrast to the local.Comment: 14 pages, 19 figure
I've got the world on a brane
This thesis treats several topics in the study of extra-dimensional models of the world, concerning Heterotic M-Theory and the dynamics of branes.
We describe a reduction to five dimensions, over a Calabi-Yau manifold, of an improved version of Heterotic M-Theory, which is valid to all orders in the gravitational coupling. This provides a starting point for considering the consequences of the improved theory for the very fruitful phenomenology of the original.
We investigate the singularities formed by the collision of gravitating branes in scalar field theory. By considering the asymptotic structure of the spacetime, the properties of the horizons formed and the growth of the curvature we argue that the singularity is not a black brane, as one might have expected, but rather a big crunch.
Finally, we construct a restricted class of multi-galileon theories as braneworld models with codimension greater than one, developing in the process some of the formalism needed for the general construction
I've got the world on a brane
This thesis treats several topics in the study of extra-dimensional models of the world, concerning Heterotic M-Theory and the dynamics of branes.
We describe a reduction to five dimensions, over a Calabi-Yau manifold, of an improved version of Heterotic M-Theory, which is valid to all orders in the gravitational coupling. This provides a starting point for considering the consequences of the improved theory for the very fruitful phenomenology of the original.
We investigate the singularities formed by the collision of gravitating branes in scalar field theory. By considering the asymptotic structure of the spacetime, the properties of the horizons formed and the growth of the curvature we argue that the singularity is not a black brane, as one might have expected, but rather a big crunch.
Finally, we construct a restricted class of multi-galileon theories as braneworld models with codimension greater than one, developing in the process some of the formalism needed for the general construction
Hermes-3: Multi-component plasma simulations with BOUT++
A new open source tool for fluid simulation of multi-component plasmas is
presented, based on a flexible software design that is applicable to scientific
simulations in a wide range of fields. This design enables the same code to be
configured at run-time to solve systems of partial differential equations in
1D, 2D or 3D, either for transport (steady-state) or turbulent (time-evolving)
problems, with an arbitrary number of ion and neutral species. To demonstrate
the capabilities of this tool, applications relevant to the boundary of tokamak
plasmas are presented: 1D simulations of diveror plasmas evolving equations for
all charge states of neon and deuterium; 2D transport simulations of tokamak
equilibria in single-null X-point geometry with plasma ion and neutral atom
species; and simulations of the time-dependent propagation of plasma filaments
(blobs). Hermes-3 is publicly available on Github under the GPL-3 open source
license. The repository includes documentation and a suite of unit, integrated
and convergence tests.Comment: Submitted to Computer Physics Communication