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 66 for “"f(R)"”.
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BIANCHI-ICOSMOLOGICALMODEL IN f(R,T) GRAVITY
Cosmology today is often described as being a ‘precision’ science, which reflects that cosmology had not always been seen as such. The enormous theoretical and experimental data from the cosmic microwave background (CMB), type Ia supernovae (SNe Ia), the Wilkinson Microwave Anisotropy Probe (WMAP), …
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A f(R)esh take on gravity
This thesis explores perturbations in f(R) modified gravity theories, with a focus on understanding the growth of large-scale structures in the Universe. Modified gravity models, particularly f(R) theories, offer an alternative explanation for cosmic acceleration without invoking dark energy. The …
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Reconceiving creativity: F. R. Leavis and higher education
The future prospects of higher education are increasingly seen as linked to the future prospects of creativity. However, much prevailing discourse on creativity and higher education sees both in narrowly instrumental terms. The literary critic and educationalist F. R. Leavis (1895–1978) provides a …
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Covariant perturbations in f (R) - gravity of multi-component fluid cosmologies
We study the evolution of scalar cosmological perturbations in the 1+3 Covariant Gauge-Invariant formalism for generic f(R) theories of gravity. Working in the energy frame of the total matter, we give a complete set equations describing the evolution of matter and curvature fluctuations for a …
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Investigating the parameter space of viable models for f(R) gravity
The accelerated expansion of spacetime intuitively points to the existence of new, unknown energy fields pervading the universe, but it is has also spurred the growth of the research field of modified gravity theories. Of these, f(R) theories of gravity is the first and simplest modification to …
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Evolution of matter density perturbations in viable f (R) theories of gravity
In the ΛCDM model, the late-time accelerated expansion of the Universe is explained via a dark energy fluid in the form of a cosmological constant. Such a cosmological constant dominates the energy budget of the Universe today, and yet, it is still a poorly understood species because it is not …
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1+1+2 covariant approach to gravitational lensing in f(R) gravity
In this thesis, we develop the 1 + 1 + 2 formalism, a technique originally devised for General Relativity, to treat spherically symmetric spacetimes in for fourth order theories of gravity. Using this formalism, we derive equations for a static and spherically symmetric spacetime for general f(R) …
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Probing the cosmological dynamics of a logarithmic f (R) theory of gravity
In this thesis we make a contribution in the area of Extended Theories of Gravity (ETG) by studying the dynamics of the R ln R model. We draw attention to the importance of introducing complete alternative theories of gravity and studying the possible geometrical origin of Dark Energy (unknown form …
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Relationship between Aspalathus linearis (Burm. F.) R. Dahlgren (rooibos) growth and soil moisture in a glasshouse and in the DSSAT-CSM crop model
Climate change and drought pose a major threat to agriculture and water resources globally and for rooibos (Aspalathus linearis (Burm. F.) R. Dahlgren) production in the Western Cape province of South Africa. Rooibos is adapted to the coarse, nutrient poor, acidic, well-drained, deep sandy soil of …
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Plant growth, stress tolerant traits and regulation of heat activated proteins in Aspalathus linearis (Burm. f.) R. Dahlgren exposed to elevated temperature and drought
Climate change is increasingly becoming a concern on plant growth, as seen in the increased number of warmer days and nights as well as an increased occurrence of heat waves, and drought periods globally. The Intergovernmental Panel on Climate Change has stated that global surface temperatures are …
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A study of solutions and perturbations of spherically symmetric spacetimes in fourth order gravity.
In this thesis we use the 1+1+2 covariant approach to General Relativity to study exact solutions and perturbations of rotationally symmetric spacetimes in f(R) gravity, one of the most widely studied classes of fourth order gravity. We begin by introducing f(R) theories of gravity and present the …
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Domains of convergence in infinite dimensional holomorphy
For certain subsets F(R) of holomorphic functions on a Reinhardt domain R in a Banach sequence space X, mainly for H_{\infty}(R), P^m(X) and P(X), we give precise descriptions of the domain of convergence dom F(R), i.e. the set of all points of R where the monomial expansion \sum_{\alpha\in …
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Improving the Sensitivity of the VRIN-r Scale on the MMPI-A-RF
<p>When respondents to self-report measures fail to answer in accordance with item content it distorts the accuracy of obtained test scores, degrading the ability of clinicians to use results to make accurate diagnoses and recommendations. The Variable Response Inconsistency (VRIN) scale was …
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Stability and gravitational collapse in extended theories of gravity: from singularities to bouncing scenarios
Einstein theory of General Relativity was well adapted and accepted until limitations in the form of an unexplained form of energy, referred today as Dark Energy, were observed. For this reason, modifications to the standard Theory of General Relativity were proposed: the so-called f(R) theories. …
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A Multi-Method Assessment Approach to the Detection of Malingered Pain: Association with the MMPI-2 Restructured Form
<p>The present study investigated the utility of the MMPI-2-Restructured Form (MMPI-2-RF) over-reporting scales (F-r, Fp-r, Fs, and FBS-r) and the Response Bias Scale (RBS) to detect symptom exaggeration among litigants claiming chronic pain. Utilizing the Bianchini et al. (2005) multi-method …
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Neutron Star Models in Alternative Theories of Gravity
<p>We study the structure of neutron stars in a broad class of alternative theories of gravity. In particular, we focus on Scalar-Tensor theories and <italic>f(R)<italic> theories of gravity. We construct static and slowly rotating numerical star models for a set of equations of state, including a …
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Direct determination of interactions at surfaces
We have obtained for the first time a fairly complete two dimensional picture of interactions between two adatoms on a surface as a function of both the interatomic distance and orientation. Four different combinations of adatoms, Re-Pd, W-Pd, Ir-Ir, and Re-Re, have been investigated on the (110) …
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Cosmological dynamics of exponential gravity
The objective of this thesis is to explore several hotly debated current issues in modern cosmology, with a focus on f(R) gravity. In chapter 1 we present a review of modern theoretical cosmology. We begin by introducing some fundamental cosmological concepts, followed by a discussion of the field …
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An analysis of the psychometric properties of the Pediatric Inventory for Parents — Short Form among caregivers of children diagnosed with autism spectrum disorder.
Pediatric caregiver stress specific to autism spectrum disorder (ASD) is associated with adverse outcomes in both parents and children, including reduced mental and physical well-being and family functioning. The Pediatric Inventory for Parents, short-form (PIP-SF), is a self-report measure of …
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