A Methodology for Evaluating and Enhancing C4I Networks

This effort focuses on expanding the bottleneck links of an existing C4I network to meet projected demands. The minimum cost-maximum flow algorithm is used to identify bottlenecks. A decision analysis approach enables the mapping of performance objectives for a network expansion into measurable attributes within the structure of a value hierarchy. A multi-attribute value function combines these measures into an overall system effectiveness measure. This allows for an evaluation of the impact of potential upgrade components on the system. A knapsack model imposes budgetary constraints on the selection of components. This methodology allows for the design of an optimized system upgrade based on system effectiveness, while offering an indication of the \u27value\u27 of the increased information flow through the network

Cosmic Strings, Zero Modes and SUSY breaking in Nonabelian N=1 Gauge Theories

We investigate the microphysics of cosmic strings in Nonabelian gauge theories with N=1 supersymmetry. We give the vortex solutions in a specific example and demonstrate that fermionic superconductivity arises because of the couplings and interactions dictated by supersymmetry. We then use supersymmetry transformations to obtain the relevant fermionic zero modes and investigate the role of soft supersymmetry breaking on the existence and properties of the superconducting strings.Comment: 12 pages, RevTex, submitted to Phys. Rev.

Compatibility of the chameleon-field model with fifth-force experiments, cosmology, and PVLAS and CAST results

We analyse the PVLAS results using a chameleon field whose properties depend on the environment. We find that, assuming a runaway bare potential $V(\phi)$ and a universal coupling to matter, the chameleon potential is such that the scalar field can act as dark energy. Moreover the chameleon field model is compatible with the CAST results, fifth force experiments and cosmology.Comment: 4 pages, title change, comments added, version to appear in Physical Review Letter

Local Axion Cosmic Strings from Superstrings

Axionic cosmic string solutions are investigated in a superstring motivated model with a pseudo-anomalous U(1) gauge symmetry. The inclusion of a gauge field and spatially varying dilaton allow local defect solutions with finite energy per unit length to be found. Fermion zero modes (whose presence is implied by supersymmetry) are also analysed. The corresponding fermion currents suggest strong cosmological bounds on the model. It is shown that the unusual form of the axion strings weakens these bounds. Other cosmological constraints on the underlying theory are also discussed.Comment: 17 page

Holistic Ethnography: Embodiment, Emotion, Contemplation, and Dialogue in Ethnographic Fieldwork

This paper theorizes holistic ethnography—an ethnographic method of inquiry that is similar to an embodied meditation practice—a conscious awareness of experience in which the researcher intentionally and variously focuses her attention on physical sensations, emotions, contemplation, and dialogue to contribute to deep sensemaking and critical examination. We illustrate this using an historical ethnographic field project as example. Only when we have immersed ourselves into our research within and beyond can we work toward a more dialogic understanding of the experience we are studying. We discuss how entering the experience through narrative requires us to focus on the embodiment of smell, taste, touch, sound, and sight of the phenomena we are studying; moving the story into our heart bids us to feel it deeply and unite with it at a place that transcends words and pulls us into the experiences; contemplating with our minds frees us to reflect on the experience and find meaning in it; and engaging dialogically invites us to discuss, connect, and voice each other and the experience into being. This approach to interpretation is messy yet thorough and provides a deep level of introspection and understanding. We end with a discussion of how this process can be used in the higher education classroom. By adding embodiment, emotion, contemplation, and dialogue to fieldwork and coursework, we suggest we are better able to critically examine cultural and social phenomena

Chiral Vortons and Cosmological Constraints on Particle Physics

We investigate the cosmological consequences of particle physics theories that admit stable loops of current-carrying string - vortons. In particular, we consider chiral theories where a single fermion zero mode is excited in the string core, such as those arising in supersymmetric theories with a D-term. The resulting vortons formed in such theories are expected to be more stable than their non-chiral cousins. General symmetry breaking schemes are considered in which strings formed at one symmetry breaking scale become current-carrying at a subsequent phase transition. The vorton abundance is estimated and constraints placed on the underlying particle physics theories from cosmological observations. Our constraints on the chiral theory are considerably more stringent than the previous estimates for more general theories.Comment: minor corrections made. This version will appear in PR

Brane World Cosmology Without the Z_2 Symmetry

The Friedmann equation for a positive tension brane situated between two bulk spacetimes that posses the same 5D cosmological constant, but which does not posses a Z2 symmetry of the metric itself is derived, and the possible effects of dropping the Z2 symmetry on the expansion of our Universe are examined; cosmological constraints are discussed. We show the effect of this is an inflation-like period at very early times. The global solutions for the metric in the infinite extra dimension case are found and comparison with the symmetric case is made. We show that any brane world senario of this type must revert to a Z2 symmetric form at late times, and hence rule out certain proposed scenarios

Fermionic Zero Modes of Supergravity Cosmic Strings

Recent developments in string theory suggest that cosmic strings could be formed at the end of brane inflation. Supergravity provides a realistic model to study the properties of strings arising in brane inflation. Whilst the properties of cosmic strings in flat space-time have been extensively studied there are significant complications in the presence of gravity. We study the effects of gravitation on cosmic strings arising in supergravity. Fermion zero modes are a common feature of cosmic strings, and generically occur in supersymmetric models. The corresponding massless currents can give rise to stable string loops (vortons). The vorton density in our universe is strongly constrained, allowing many theories with cosmic strings to be ruled out. We investigate the existence of fermion zero modes on cosmic strings in supergravity theories. A general index theorem for the number of zero modes is derived. We show that by including the gravitino, some (but not all) zero modes disappear. This weakens the constraints on cosmic string models. In particular, winding number one cosmic D-strings in models of brane inflation are not subject to vorton constraints. We also discuss the effects of supersymmetry breaking on cosmic D-strings.Comment: 33 page

The Dilaton and Modified Gravity

We consider the dilaton in the strong string coupling limit and elaborate on the original idea of Damour and Polyakov whereby the dilaton coupling to matter has a minimum with a vanishing value at finite field-value. Combining this type of coupling with an exponential potential, the effective potential of the dilaton becomes matter density dependent. We study the background cosmology, showing that the dilaton can play the role of dark energy. We also analyse the constraints imposed by the absence of violation of the equivalence principle. Imposing these constraints and assuming that the dilaton plays the role of dark energy, we consider the consequences of the dilaton on large scale structures and in particular the behaviour of the slip functions and the growth index at low redshift.Comment: 14 pages, 4 figure