A Cosmological Super-Bounce

We study a model for a non-singular cosmic bounce in N=1 supergravity, based on supergravity versions of the ghost condensate and cubic Galileon scalar field theories. The bounce is preceded by an ekpyrotic contracting phase which prevents the growth of anisotropies in the approach to the bounce, and allows for the generation of scale-invariant density perturbations that carry over into the expanding phase of the universe. We present the conditions required for the bounce to be free of ghost excitations, as well as the tunings that are necessary in order for the model to be in agreement with cosmological observations. All of these conditions can be met. Our model thus provides a proof-of-principle that non-singular bounces are viable in supergravity, despite the fact that during the bounce the null energy condition is violated.Comment: 38 pages, 13 figures, v3: typos correcte

Cosmological Perturbations Through a Non-Singular Ghost-Condensate/Galileon Bounce

We study the propagation of super-horizon cosmological perturbations in a non-singular bounce spacetime. The model we consider combines a ghost condensate with a Galileon term in order to induce a ghost-free bounce. Our calculation is performed in harmonic gauge, which ensures that the linearized equations of motion remain well-defined and non-singular throughout. We find that, despite the fact that near the bounce the speed of sound becomes imaginary, super-horizon curvature perturbations remain essentially constant across the bounce. In fact, we show that there is a time close to the bounce where curvature perturbations of all wavelengths are required to be momentarily exactly constant. We relate our calculations to those performed in other gauges, and comment on the relation to previous results in the literature.Comment: 28 pages, 16 figures, v2: references adde

Treating the Whole Child: Recognizing and Addressing Depression in Children with Physical Disabilities

The purpose of this scholarly project was to develop a tool that would assist occupational therapy practitioners working with children with physical disabilities in recognizing and addressing symptoms of depression in that population. Ailey (2003) reported that symptoms of depression in children with developmental disabilities are frequently attributed incorrectly to a child\u27s primary diagnosis, rather than depression. Because occupational therapists typically see these children more frequently than primary care physicians, they are in a prime position to assist in the screening and referral processes related to depression. This project involved a comprehensive review of the literature, including data on the prevalence of psychosocial dysfunction, needs of affected individuals, impact on families, available screening tools, programs addressing needs, the related role of occupational therapy, and the integration of occupational therapy theory. The available literature supported the hypothesis that children with physical disabilities have at least the same, if not greater, risk of psychosocial dysfunction as their non-disabled peers (Ailey, 2003; Cadman, Boyle, Szatmari, & Offord, 1987; Kokkonen, Kokkonen, & Moilanen, 2001). The author informally consulted with other occupational therapists working with children with physical disabilities to determine their perceived needs related to addressing psychosocial issues in a physical disabilities setting. Theories and models of practice in occupational therapy were reviewed, and the Model of Human Occupation, by Gary Kielhofner and Kirsty Forsyth, was selected to guide the development of this project, due to its holistic nature and having both physical and psychosocial applications. A reference manual was developed to meet the needs identified by occupational therapy practitioners working with children with physical disabilities. Included in the manual is information related to the prevalence of depression in children with physical disabilities, information related to the need to assess and address psychosocial skills in the context of traditional pediatric settings, a listing of symptoms of depression in children, summative information on a variety of available screening tools for depression in children, and a reproducible assessment tool to enable screening of some children to begin right away. Examples of treatment activities which address both psychosocial and physical needs are also included

The Rwenzori Mountains, a Paleoproterzoic crustal shear belt crossing the Albertine rift system

This contribution discusses the development of the Paleoproterozoic Buganda-Toro belt in the Rwenzori mountains and its influence on the western part of the East African Rift System in Uganda. The Buganda-Toro belt is composed of several thick-skinned nappes consisting of Archaean Gneisses and Palaeoproterozoic cover units that are thrusted northwards. The high Rwenzori mountains are located in the frontal unit of this belt with retrograde greenschist facies gneisses towards the north, which are unconformably overlain by metasediments and amphibolites. Towards the south the metasediments are overthrust by the next migmatitic gneiss unit that belongs to a crustal scale nappe. The southwards dipping metasedimentary and volcanic sequence in the high Rwenzori mountains shows an inverse metamorphic grade with greenschist facies conditions in the north and amphibolite facies conditions in the south. Early D1 deformation structures are overgrown by cordierite, which in turn grows into D2 deformation, representing the major northwards directed thrusting event. We argue that the inverse metamorphic gradient develops because higher grade rocks are exhumed in the footwall of a crustal scale nappe whereas the exhumation decreases towards the north away from the nappe leading to a decrease in metamorphic grade. The D2 deformation event is followed by a D3 E-W compression, a D4 with the development of steep shear zones with a NNE-SSW and SSE-NNW trend including the large Nyamwamba shear followed by a local D5 retrograde event and D6 brittle inverse faulting. The Paleoproterozoic Buganda-Toro belt is relatively stiff and crosses the NNE-SSW running rift system exactly at the node where the highest peaks of the Rwenzori mountains are situated and where the lake George rift terminates towards the north. Orientation of brittle and ductile fabrics show some similarities indicating that the cross-cutting Buganda-Toro belt influenced rift propagation and brittle fault development within the Rwenzori mountain and that this stiff belt may form part of the reason why the Rwenzori mountains are relatively high within the rift. Keywords: East African Rift, Basement, Buganda Toro, Inverse Metamorphic Gradient, Microtectonics, Rwenzori mountain

Higher-Derivative Chiral Superfield Actions Coupled to \u3cem\u3eN\u3c/em\u3e = 1 Supergravity

We construct N = 1 supergravity extensions of scalar field theories with higher-derivative kinetic terms. Special attention is paid to the auxiliary fields, whose elimination leads not only to corrections to the kinetic terms, but to new expressions for the potential energy as well. For example, a potential energy can be generated even in the absence of a superpotential. Our formalism allows one to write a supergravity extension of any higher-derivative scalar field theory and therefore has applications to both particle physics and cosmological model building. As an illustration, we couple the higher-derivative Dirac-Born-Infeld action describing a 3-brane in six dimensions to N = 1 supergravity. This displays a number of new features including the fact that in the regime where the higher-derivative kinetic terms become important, the potential tends to be everywhere negative

Ghost Condensate in \u3cem\u3eN\u3c/em\u3e = 1 Supergravity

We present the theory of a supersymmetric ghost condensate coupled to N=1 supergravity. This is accomplished using a general formalism for constructing locally supersymmetric higher-derivative chiral superfield actions. The theory admits a ghost condensate vacuum in de Sitter spacetime. Expanded around this vacuum, the scalar sector of the theory is shown to be ghost-free with no spatial gradient instabilities. By direct calculation, the fermion sector is found to consist of a massless chiral fermion and a massless gravitino. By analyzing the supersymmetry transformations, we find that the chiral fermion transforms inhomogeneously, indicating that the ghost condensate vacuum spontaneously breaks local supersymmetry with this field as the Goldstone fermion. Although potentially able to get a mass through the super-Higgs effect, the vanishing superpotential in the ghost condensate theory renders the gravitino massless. Thus local supersymmetry is broken without the super-Higgs effect taking place. This is in agreement with, and gives an explanation for, the direct calculation

DBI Inflation in \u3cem\u3eN\u3c/em\u3e = 1 Supergravity

It was recently demonstrated that, when coupled to N = 1 supergravity, the Dirac-Born-Infeld (DBI) action constructed from a single chiral superfield has the property that when the higher-derivative terms become important, the potential becomes negative. Thus, DBI inflation cannot occur in its most interesting, relativistic regime. In this paper, it is shown how to overcome this problem by coupling the model to one or more additional chiral supermultiplets. In this way, one obtains effective single real scalar field DBI models with arbitrary positive potentials, as well as multiple real scalar field DBI inflation models with hybrid potentials

Higher-Derivative Chiral Superfield Actions Coupled to N=1 Supergravity

We construct N=1 supergravity extensions of scalar field theories with higher-derivative kinetic terms. Special attention is paid to the auxiliary fields, whose elimination leads not only to corrections to the kinetic terms, but to new expressions for the potential energy as well. For example, a potential energy can be generated even in the absence of a superpotential. Our formalism allows one to write a supergravity extension of any higher-derivative scalar field theory and, therefore, has applications to both particle physics and cosmological model building. As an illustration, we couple the higher-derivative DBI action describing a 3-brane in 6-dimensions to N=1 supergravity. This displays a number of new features-- including the fact that, in the regime where the higher-derivative kinetic terms become important, the potential tends to be everywhere negative.Comment: 37 pages, v2: references adde