An Evaluation of Design Rule Spaces as Risk Containers

It is well understood that software development can be a risky enterprise and industrial projects often overrun budget and schedule. Effective risk management is, therefore, vital for a successful project outcome. Design Rule Spaces (DRSpaces) have been used by other researchers to understand why implemented software is error-prone. This industrial case study evaluates whether such spaces are durable, meaningful, and isolating risk containers. DRSpaces were created from UML class diagrams of architectural design artefacts. In our study, object orientated metrics were calculated from the UML diagrams, and compared to the error-proneness of the DRSpace implementation, to determine whether architectural coupling translated into implementation difficulties. A correlation between architectural coupling and error-proneness of DRSpaces was observed in the case study. Software developers were asked to identify DRSpaces they found difficult to implement, in order to understand which factors, other than architectural coupling, were also important. The qualitative results show agreement between the code areas developers found difficult to implement and the error-prone DRSpaces. However, the results also show that architectural coupling is just one risk factor of many. The case study suggests that architectural DRSpaces can be used to facilitate a targeted risk review prior to implementation and manage risk

A rough end for smooth microstate geometries

Supersymmetric microstate geometries with five non-compact dimensions have recently been shown by Eperon, Reall, and Santos (ERS) to exhibit a non-linear instability featuring the growth of excitations at an "evanescent ergosurface" of infinite redshift. We argue that this growth may be treated as adiabatic evolution along a family of exactly supersymmetric solutions in the limit where the excitations are Aichelburg-Sexl-like shockwaves. In the 2-charge system such solutions may be constructed explicitly, incorporating full backreaction, and are in fact special cases of known microstate geometries. In a near-horizon limit, they reduce to Aichelburg-Sexl shockwaves in $AdS_3 \times S^3$ propagating along one of the angular directions of the sphere. Noting that the ERS analysis is valid in the limit of large microstate angular momentum $j$, we use the above identification to interpret their instability as a transition from rare smooth microstates with large angular momentum to more typical microstates with smaller angular momentum. This entropic driving terminates when the angular momentum decreases to $j \sim \sqrt{n_1n_5}$ where the density of microstates is maximal. We argue that, at this point, the large stringy corrections to such microstates will render them non-linearly stable. We identify a possible mechanism for this stabilization and detail an illustrative toy model.Comment: 22 pages, 1 figure. v2: JHEP version with references adde

Many body effects in the excitation spectrum of a defect in SiC

We show that electron correlations control the photophysics of defects in SiC through both renormalization of the quasiparticle bandstructure and exciton effects. We consider the carbon vacancy, which is a well-identified defect with two possible excitation channels that involve conduction and valence band states. Corrections to the Kohn-Sham ionization levels are found to strongly depend on the occupation of the defect state. Excitonic effects introduce a red shift of 0.23 eV. The analysis unambigiously re-assigns excitation mechanism at the thresholds in photo-induced paramagnetic resonance measurements [J. Dashdorj \emph{et al.}, J. Appl. Phys. \textbf{104}, 113707 (2008)]

Journey to the Center of the Fuzzball

We study two-charge fuzzball geometries, with attention to the use of the proper duality frame. For zero angular momentum there is an onion-like structure, and the smooth D1-D5 geometries are not valid for typical states. Rather, they are best approximated by geometries with stringy sources, or by a free CFT. For non-zero angular momentum we find a regime where smooth fuzzball solutions are the correct description. Our analysis rests on the comparison of three radii: the typical fuzzball radius, the entropy radius determined by the microscopic theory, and the breakdown radius where the curvature becomes large. We attempt to draw more general lessons.Comment: 22 pages, 1 figur

The complement of the open orbit for tame quivers

Let Q be a tame quiver and d a prehomogeneous dimension vector. We consider the complement of the open orbit of the representation space Rep (Q; d) and generalise the idea of A. Schofield to obtain for each irreducible component of codimension greater than one an ideal in the polynomial ring k [Rep (Q; d)] whose zero set is this component. Moreover, we compare our result with the one of K. Baur and L. Hille, who found for each irreducible component some defining rank conditions in case Q is the equioriented Dynkin quiver of type An

Enhancement of particle trapping in the wave-particle interaction

The saturated dynamics of a Single-Pass Free Electron Laser is considered within a simplified mean-field approach. A method is proposed to increase the size of the macro-particle, which is responsible for the oscillations of the intensity of the wave. This approach is based on the reconstruction of invariant tori of the dynamics of test particles. To this aim a dedicated control term is derived, the latter acting as a small apt perturbation of the system dynamics. Implications of these findings are discussed in relation to the optimization of the laser source

Group behavior impact on an opportunistic localization scheme

In this paper we tackled the localization problem from an opportunistic perspective, according to which a node can infer its own spatial position by exchanging data with passing by nodes, called peers. We consider an opportunistic localization algorithm based on the linear matrix inequality (LMI) method coupled with a weighted barycenter algorithm. This scheme has been previously analyzed in scenarios with random deployment of peers, proving its effectiveness. In this paper, we extend the analysis by considering more realistic mobility models for peer nodes. More specifically, we consider two mobility models, namely the Group Random Waypoint Mobility Model and the Group Random Pedestrian Mobility Model, which is an improvement of the first one. Hence, we analyze by simulation the opportunistic localization algorithm for both the models, in order to gain insights on the impact of nodes mobility pattern onto the localization performance. The simulation results show that the mobility model has non-negligible effect on the final localization error, though the performance of the opportunistic localization scheme remains acceptable in all the considered scenarios

Phase-dependent molecular requirements for memory reconsolidation: differential roles for protein synthesis and protein kinase A activity

After consolidation, a process that requires gene expression and protein synthesis, memories are stable and highly resistant to disruption by amnestic influences. Recently, consolidated memory has been shown to become labile again after retrieval and to require a phase of reconsolidation to be preserved. New findings, showing that the dependence of reconsolidation on protein synthesis decreases with the age of memory, point to changing molecular requirements for reconsolidation during memory maturation. We examined this possibility by comparing the roles of protein synthesis (a general molecular requirement for memory consolidation) and the activation of protein kinase A (PKA) (a specific molecular requirement for memory consolidation), in memory reconsolidation at two time points after training. Using associative learning in Lymnaea, we show that reconsolidation after the retrieval of consolidated memory at both 6 and 24 h requires protein synthesis. In contrast, only reconsolidation at 6 h after training, but not at 24 h, requires PKA activity, which is in agreement with the measured retrieval-induced PKA activation at 6 h. This phase-dependent differential molecular requirement for reconsolidation supports the notion that even seemingly consolidated memories undergo further selective molecular maturation processes, which may only be detected by analyzing the role of specific pathways in memory reconsolidation after retrieval