D3-brane Vacua in Stabilized Compactifications

D3-branes feel no force in no-scale flux compactifications of type IIB string theory, but the nonperturbative effects required to stabilize the Kahler moduli break the no-scale structure and generate a potential for D3-brane motion, confining the branes to certain loci. D3-branes away from these loci break supersymmetry spontaneously, by an F-term. We present the general conditions for supersymmetric D3-brane vacua in models with a single Kahler modulus, then explicitly calculate these vacua for D3-branes moving on the tip of the warped deformed conifold. We find both continuous moduli spaces and isolated vacua. In addition, we show that anti-D3-branes and D3-branes are localized to the same regions by the nonperturbative potential, avoiding a potential obstacle to brane inflation. We apply these results to determine whether angular motion of a brane in a throat could play an important role in inflation, and find that any inflation along the angular directions is short-lived because the field space is very small.Comment: 30 pages, LaTeX. v2: references added, typos fixe

Rescued By Design: Enabling Low Resource Communities to Reduce Global Drowning

In recent years Bournemouth University (BU) has witnessed a growth in undergraduate projects aimed at resolving problems in low-resource communities, with an emphasis on sustainability through the use of locally-available resources and production methods. BU academics have also been involved in helping the Royal National Lifeboat Institute (RNLI) to develop product solutions to help prevent global drowning, with an initial focus on the Bangladeshi context. Alongside the potential to enrich or even save lives in the target communities, such projects can offer considerable benefits to a range of domestic stakeholders: from the students and staff themselves to local businesses and non-government organisations (NGO’s). But they can also offer considerable challenges - educationally, ethically and practically – including issues with design validation, the reliability and availability of information, and the barriers of differing cultures and languages.How can educators support low-resource projects successfully? Can students truly gain sufficient understanding of all the relevant issues to design products for an unfamiliar culture, no matter how diverse? And why are low-resource communities looking to designers from the other side of the world to provide low-tech solutions to local problems?Bournemouth University’s low-resource projects have achieved varying degrees of success. By examining some of these - including the RNLI’s Bottle Buoy, which has recently gained international acclaim - the authors explore the complex issues relating to the use of such projects in an educational context, and present a proposal for future success using jugaad strategies and greater collaboration

Probing the Geometry of Warped String Compactifications at the LHC

Warped string compactifications, characterized by non-singular behavior of the metric in the infrared (IR), feature departures from the usual anti-de Sitter warped extra dimensions. We study the implications of the smooth IR cutoff for Randall-Sundrum (RS) type models. We find that the phenomenology of the KK gravitons (including their masses and couplings) depends sensitively on the precise shape of the warp factor in the IR. In particular, we analyze the warped deformed conifold and find that the spectrum differs significantly from that of RS, and present a simple prescription (a mass gap ansatz) which can be used to study the phenomenology of IR modifications to 5-d warped extra dimensions.Comment: 4 pages, 4 figures; v2. typos corrected, references added, improved resolution of Figure

Multifield DBI Inflation and Non-Gaussianities

We analyze the trajectories for multifield DBI inflation, which can arise in brane inflation models, and show that the trajectories are the same as in typical slow roll inflation. We calculate the power spectrum and find that the higher derivative terms of the DBI action lead to a suppression of the contribution from the isocurvature perturbations. We also calculate the bispectrum generated by the isocurvature perturbation, and find that it leads to distinctive features.Comment: 7 pages, 4 figures; v2. references added; v3. typos corrected, matches published versio

Challenges of 3D Printing for Home Users

3D printing is described as the next industrial revolution bringing manufacturing to the home. However, it’s attraction to the home or non-technical user is frustrated by the difficulty in deploying the software and the technology which both need professional understanding and training. Research and innovation in this area has concentrated on technology, not users and usability. Home users can access simple design software tools, best described as good for one task only. Software such as Microsoft word and Excel have been the subject of development for enabling most people to use computers without the need for training or the ability to program. However research in the home users of 3-D printing is very limited. This literature review is concerned is an investigation into home/non-technical use of 3-D printers, their needs and limitations, in order to facilitate the development of effective tools and manuals. An investigation of literature and a survey supported by a focus group of 42 university students aims to understand the way home/non-technical users currently use designs, and how they can to adapt/change their designs for effective use of 3-D printing. This will identify the tools/’apps’ needed for accessible understanding and deployment of the technology

Observing the Geometry of Warped Compactification via Cosmic Inflation

Using DBI inflation as an example, we demonstrate that the detailed geometry of warped compactification can leave an imprint on the cosmic microwave background (CMB). We compute CMB observables for DBI inflation in a generic class of warped throats and find that the results (such as the sign of the tilt of the scalar perturbations and its running) depend sensitively on the precise shape of the warp factor. In particular, we analyze the warped deformed conifold and find that the results can differ from those of other warped geometries, even when these geometries approximate well the exact metric of the warped deformed conifold.Comment: 4 pages, 3 figures. v2: References and clarifications adde

Minimal Simple de Sitter Solutions

We show that the minimal set of necessary ingredients to construct explicit, four-dimensional de Sitter solutions from IIA string theory at tree-level are O6-planes, non-zero Romans mass parameter, form fluxes, and negative internal curvature. To illustrate our general results, we construct such minimal simple de Sitter solutions from an orientifold compactification of compact hyperbolic spaces. In this case there are only two moduli and we demonstrate that they are stabilized to a sufficiently weakly coupled and large volume regime. We also discuss generalizations of the scenario to more general metric flux constructions.Comment: 12 pages, 2 figures, important error in v1 corrected but main result unaltered; v3 sent to PRD; v4 version published in PRD, minor modifications for clarificatio