The Sen Limit

F-theory compactifications on elliptic Calabi-Yau manifolds may be related to IIb compactifications by taking a certain limit in complex structure moduli space, introduced by A. Sen. The limit has been characterized on the basis of SL(2,Z) monodromies of the elliptic fibration. Instead, we introduce a stable version of the Sen limit. In this picture the elliptic Calabi-Yau splits into two pieces, a P^1-bundle and a conic bundle, and the intersection yields the IIb space-time. We get a precise match between F-theory and perturbative type IIb. The correspondence is holographic, in the sense that physical quantities seemingly spread in the bulk of the F-theory Calabi-Yau may be rewritten as expressions on the log boundary. Smoothing the F-theory Calabi-Yau corresponds to summing up the D(-1)-instanton corrections to the IIb theory.Comment: 41 pp, 1 figure, LaTe

Iterative criteria-based approach to engineering the requirements of software development methodologies

Software engineering endeavours are typically based on and governed by the requirements of the target software; requirements identification is therefore an integral part of software development methodologies. Similarly, engineering a software development methodology (SDM) involves the identification of the requirements of the target methodology. Methodology engineering approaches pay special attention to this issue; however, they make little use of existing methodologies as sources of insight into methodology requirements. The authors propose an iterative method for eliciting and specifying the requirements of a SDM using existing methodologies as supplementary resources. The method is performed as the analysis phase of a methodology engineering process aimed at the ultimate design and implementation of a target methodology. An initial set of requirements is first identified through analysing the characteristics of the development situation at hand and/or via delineating the general features desirable in the target methodology. These initial requirements are used as evaluation criteria; refined through iterative application to a select set of relevant methodologies. The finalised criteria highlight the qualities that the target methodology is expected to possess, and are therefore used as a basis for de. ning the final set of requirements. In an example, the authors demonstrate how the proposed elicitation process can be used for identifying the requirements of a general object-oriented SDM. Owing to its basis in knowledge gained from existing methodologies and practices, the proposed method can help methodology engineers produce a set of requirements that is not only more complete in span, but also more concrete and rigorous

Tachyon kinks on non BPS D-branes

We consider solitonic solutions of the DBI tachyon effective action for a non-BPS brane. When wrapped on a circle, these solutions are regular and have a finite energy. We show that in the decompactified limit, these solitons give Sen's infinitely thin finite energy kink -- interpreted as a BPS brane -- provided that some conditions on the potential hold. In particular, if for large $T$ the potential is exponential, $V = e^{-T^a}$, then Sen's solution is only found for $a<1$. For power-law potentials $V = 1/T^b$, one must have $b>1$. If these conditions are not satisfied, we show that the lowest energy configuration is the unstable tachyon vacuum with no kinks. We examine the stability of the solitons and the spectrum of small perturbations.Comment: 16 pages, 2 figure

Late-Breaking Papers of EuroGP-99

This booklet contains the late-breaking papers of the Second European Workshop on Genetic Programming (EuroGP’99) held in G"oteborg Sweden 26–27 May 1999. EuroGP’99 was one of the EvoNet workshops on evolutionary computing, EvoWorkshops’99. The purpose of the late-breaking papers was to provide attendees with information about research that was initiated, enhanced, improved, or completed after the original paper submission deadline in December 1998. To ensure coverage of the most up-to-date research, the deadline for submission was set only a month before the workshop. Late-breaking papers were examined for relevance and quality by the organisers of the EuroGP’99, but no formal review process took place. The 3 late-breaking papers in this booklet (which was distributed at the workshop) were presented during a poster session held on Thursday 27 May 1999 during EuroGP’99. Authors individually retain copyright (and all other rights) to their late-breaking papers. This booklet is available as a technical report SEN-R9913 from Centrum voor Wiskunde en Informatica, Kruislaan 413, NL-1098 SJ Amsterdam http://www.cwi.nl/static/publications/reports/reports.htm

STRING STRING DUALITY CONJECTURE IN SIX DIMENSIONS AND CHARGED SOLITONIC STRINGS

It has recently been conjectured that the type IIA string theory compactified on K3 and the heterotic string theory compactified on a four dimensional torus describe identical string theories. The fundamental heterotic string can be regarded as a non-singular soliton solution of the type IIA string theory with a semi-infinite throat. We show that this solution admits 24 parameter non-singular deformation describing a fundamental heterotic string carrying electric charge and current. The charge is generated due to the coupling of the gauge fields to the anti-symmetric tensor field, and not to an explicit source term. This clarifies how soliton solutions carrying charge under the Ramond-Ramond fields can be constructed in the type IIA theory, and provides further support to the string string duality conjecture. Similarly, the fundamental type IIA string can be regarded as a non-singular solution of the heterotic string theory with a semi-infinite throat, but this solution does not admit any deformation representing charged string. This is also consistent with the expectation that a fundamental type IIA string does not carry any charge that couples to the fields originating in the Ramond-Ramond sector.Comment: 17 pages, LaTeX fil

Open/Closed Duality, Unstable D-Branes, and Coarse-Grained Closed Strings

At the final stage of unstable D-brane decay in the effective field theory approach, all energy and momentum of the initial state are taken up by two types of fluids, known as string fluid and tachyon matter. In this note, we compare motion of this fluid system to that of macroscopic collection of stretched closed strings and find a precise match at classical level. The string fluid reflects low frequency undulation of the stretched strings while the tachyon matter encodes the average effect of high frequency oscillations turned on those strings. In particular, the combined fluid system has been known to have a reduced speed of light, depending on the composition, and we show that this property is exactly reproduced in classical motion on the closed string side. Finally we illustrate how the tachyon matter may be viewed as an effective degrees of freedom carrying high frequency energy-momentum of Nambu-Goto strings by coarse-graining the dynamics of the latter.Comment: LaTeX, 29 pages, 4 figure file

Benford's Law Detects Quantum Phase Transitions similarly as Earthquakes

A century ago, it was predicted that the first significant digit appearing in a data would be nonuniformly distributed, with the number one appearing with the highest frequency. This law goes by the name of Benford's law. It holds for data ranging from infectious disease cases to national greenhouse gas emissions. Quantum phase transitions are cooperative phenomena where qualitative changes occur in many-body systems at zero temperature. We show that the century-old Benford's law can detect quantum phase transitions, much like it detects earthquakes. Therefore, being certainly of very different physical origins, seismic activity and quantum cooperative phenomena may be detected by similar methods. The result has immediate implications in precise measurements in experiments in general, and for realizable quantum computers in particular. It shows that estimation of the first significant digit of measured physical observables is enough to detect the presence of quantum phase transitions in macroscopic systems.Comment: v1: 3 pages, 2 figures; v2: 6 (+epsilon) epl pages, 5 figures, significant additions, previous results unchange

StoryDroid: Automated Generation of Storyboard for Android Apps

Mobile apps are now ubiquitous. Before developing a new app, the development team usually endeavors painstaking efforts to review many existing apps with similar purposes. The review process is crucial in the sense that it reduces market risks and provides inspiration for app development. However, manual exploration of hundreds of existing apps by different roles (e.g., product manager, UI/UX designer, developer) in a development team can be ineffective. For example, it is difficult to completely explore all the functionalities of the app in a short period of time. Inspired by the conception of storyboard in movie production, we propose a system, StoryDroid, to automatically generate the storyboard for Android apps, and assist different roles to review apps efficiently. Specifically, StoryDroid extracts the activity transition graph and leverages static analysis techniques to render UI pages to visualize the storyboard with the rendered pages. The mapping relations between UI pages and the corresponding implementation code (e.g., layout code, activity code, and method hierarchy) are also provided to users. Our comprehensive experiments unveil that StoryDroid is effective and indeed useful to assist app development. The outputs of StoryDroid enable several potential applications, such as the recommendation of UI design and layout code