From Black Strings to Black Holes

Using recently developed numerical methods, we examine neutral compactified non-uniform black strings which connect to the Gregory-Laflamme critical point. By studying the geometry of the horizon we give evidence that this branch of solutions may connect to the black hole solutions, as conjectured by Kol. We find the geometry of the topology changing solution is likely to be nakedly singular at the point where the horizon radius is zero. We show that these solutions can all be expressed in the coordinate system discussed by Harmark and Obers.Comment: 6 pages, 5 figures, RevTe

Incorporating the Dual Customer Roles in e-Service Design

E-service involves the delivery of useful services through information technology based service delivery channels such as the Internet. A distinguishing feature of e-service is the active and significant participation of customers in the service co-production process. With increasing customer participation in the e-service co-production process, it is important to incorporate customers’ needs both as a co-producer and as a patron into the design of e-service systems. However, these dual customer roles create a complex decision problem during e-service design. In the current paper we present a customer orientation strategy for e-service design, and propose a corresponding two-stage decision model based upon the customer orientation strategy to evaluate the efficiency and effectiveness of e-service design when the focus of the design is to meet customers’ needs as both co-producers and patrons. The decision model is then applied in an empirical study of the design of e-services of Internet food retailers. Key Words: Service Operations, E-Service, Co-production, Efficiency Analysis, Data Envelopment Analysis

Inflating magnetically charged braneworlds

Numerical solutions of Einstein, scalar, and gauge field equations are found for static and inflating defects in a higher-dimensional spacetime. The defects have $(3+1)$-dimensional core and magnetic monopole configuration in $n=3$ extra dimensions. For symmetry-breaking scale $\eta$ below the critical value $\eta_c$, the defects are characterized by a flat worldsheet geometry and asymptotically flat extra dimensions. The critical scale $\eta_c$ is comparable to the higher-dimensional Planck scale and has some dependence on the gauge and scalar couplings. For $\eta=\eta_c$, the extra dimensions degenerate into a `cigar', and for $\eta>\eta_c$ all static solutions are singular. The singularity can be removed if the requirement of staticity is relaxed and defect cores are allowed to inflate. The inflating solutions have de Sitter worldsheets and cigar geometry in the extra dimensions. Exact analytic solutions describing the asymptotic behavior of these inflating monopoles are found and the parameter space of these solutions is analyzed.Comment: 35 pages, revtex, 18 eps figure

Small Black Holes on Cylinders

We find the metric of small black holes on cylinders, i.e. neutral and static black holes with a small mass in d-dimensional Minkowski-space times a circle. The metric is found using an ansatz for black holes on cylinders proposed in hep-th/0204047. We use the new metric to compute corrections to the thermodynamics which is seen to deviate from that of the (d+1)-dimensional Schwarzschild black hole. Moreover, we compute the leading correction to the relative binding energy which is found to be non-zero. We discuss the consequences of these results for the general understanding of black holes and we connect the results to the phase structure of black holes and strings on cylinders.Comment: 23 pages, 1 figure. v2: typos corrected, introduction expanded, v3: presentation of sections 2 and 3 reordered and improved, explanatory remarks added, refs adde

Curvature Corrections to Dynamics of Domain Walls

The most usual procedure for deriving curvature corrections to effective actions for topological defects is subjected to a critical reappraisal. A logically unjustified step (leading to overdetermination) is identified and rectified, taking the standard domain wall case as an illustrative example. Using the appropriately corrected procedure, we obtain a new exact (analytic) expression for the corresponding effective action contribution of quadratic order in the wall width, in terms of the intrinsic Ricci scalar $R$ and the extrinsic curvature scalar $K$. The result is proportional to $cK^2-R$ with the coefficient given by $c\simeq 2$. The resulting form of the ensuing dynamical equations is obtained in terms of the second fundamental form and the Dalembertian of its trace, K. It is argued that this does not invalidate the physical conclusions obtained from the "zero rigidity" ansatz $c=0$ used in previous work.Comment: 19 pages plain TeX, 2 figures include

Defining the gap between research and practice in public relations programme evaluation - towards a new research agenda

The current situation in public relations programme evaluation is neatly summarized by McCoy who commented that 'probably the most common buzzwords in public relations in the last ten years have been evaluation and accountability' (McCoy 2005, 3). This paper examines the academic and practitioner-based literature and research on programme evaluation and it detects different priorities and approaches that may partly explain why the debate on acceptable and agreed evaluation methods continues. It analyses those differences and proposes a research agenda to bridge the gap and move the debate forward

Strain amplitude response and the microstructure of PA/clay nanocomposites

Polyamide 6/clay nanocomposites (PAn, where n is the mass fraction of clay) with various clay loading were prepared by melt compounding in a twin screw extruder. Exfoliation of clay in a PA matrix was confirmed by X-ray diffraction. Strain amplitude response of PAn in both melt and solution states has been investigated. In the melt state, critical strain amplitude of PAn is sensitive to strain amplitude response and decrease logarithmically with increasing clay loading. The elastic moduli (G′) of PAn are reversible under frequency loop sweeps. Comparisons of strain amplitude response in both melt and solution states have been conducted. Two different responses have been observed: strain thinning in the melt state and weak strain overshoot in the solution state. FTIR studies show that amide II band of PAn shifts toward high wavenumbers, but amide I band and N–H stretching vibration are independent of clay loading. We suggest that two types of strain amplitude response of PAn can be explained: strain thinning which is dominant in PAn caused by physical adsorption and entanglement of PA chains on nanoclays and weak strain overshoot caused by weak bonds between PA chains and nanoclays

Static Axisymmetric Vacuum Solutions and Non-Uniform Black Strings

We describe new numerical methods to solve the static axisymmetric vacuum Einstein equations in more than four dimensions. As an illustration, we study the compactified non-uniform black string phase connected to the uniform strings at the Gregory-Laflamme critical point. We compute solutions with a ratio of maximum to minimum horizon radius up to nine. For a fixed compactification radius, the mass of these solutions is larger than the mass of the classically unstable uniform strings. Thus they cannot be the end state of the instability.Comment: 48 pages, 13 colour figures; v2: references correcte

A universe in a global monopole

We investigate brane physics in a universe with an extra dimensional global monopole and negative bulk cosmological constant. The graviton zero mode is naturally divergent; we thus invoke a physical cut-off to induce four dimensional gravity on a brane at the monopole core. Independently, the massive Kaluza-Klein modes have naturally compactified extra dimensions, inducing a discrete spectrum. This spectrum remains consistent with four dimensional gravity on the brane, even for small mass gap. Extra dimensional matter fields also induce four dimensional matter fields on the brane, with the same Kaluza-Klein spectrum of excited states. We choose parameters to solve the hierarchy problem; that is, to induce the observed hierarchy between particle and Planck scales in the effective four dimensional universe.Comment: 22 pages, 2 eps figures, revte

High-resolution Spectroscopy of [Ne II] Emission from TW Hya

We present high-resolution echelle spectra of [Ne II] 12.81 micron emission from the classical T Tauri star (CTTS) TW Hya obtained with MICHELLE on Gemini North. The line is centered at the stellar radial velocity and has an intrinsic FWHM of 21\pm 4 km/s. The line width is broader than other narrow emission lines typically associated with the disk around TW Hya. If formed in a disk, the line broadening could result from turbulence in a warm disk atmosphere, Keplerian rotation at an average distance of 0.1 AU from the star, or a photoevaporative flow from the optically-thin region of the disk. We place upper limits on the [Ne II] emission flux from the CTTSs DP Tau and BP Tau.Comment: Accepted by ApJ. 18 pages, including 2 figures and 2 table