Factors influencing the pricing of applications in the Apple App Store: A developers\u2019 perspective

Many know how Apple Inc. owes its success in Mobile Commerce to the introduction of the new \u201cApp Store\u201d business model. This new market is characterized by the opening to third party mobile apps, which are distributed to consumers through the App Store. This paper investigates factors that might influence the pricing of applications in the Apple Mobile Application Store. By reviewing the existing literature on the issue and analyzing the strategic features characterizing the App Store, we detect three main factors that could influence prices for apps, that is the number of developed apps, the presence of two-sided network externalities and developer\u2019s specialization. An empirical analysis on data from 68,220 apps downloaded from the Italian App Store is used to test the hypotheses. Regression results support our hypotheses. We argue, that even if the research here presented can be considered as a started analysis to the pricing problem in such markets, this work may have important managerial implication for the thousands of developers that are competing in this emerging market

Decision Procedure for Entailment of Symbolic Heaps with Arrays

This paper gives a decision procedure for the validity of en- tailment of symbolic heaps in separation logic with Presburger arithmetic and arrays. The correctness of the decision procedure is proved under the condition that sizes of arrays in the succedent are not existentially bound. This condition is independent of the condition proposed by the CADE-2017 paper by Brotherston et al, namely, one of them does not imply the other. For improving efficiency of the decision procedure, some techniques are also presented. The main idea of the decision procedure is a novel translation of an entailment of symbolic heaps into a formula in Presburger arithmetic, and to combine it with an external SMT solver. This paper also gives experimental results by an implementation, which shows that the decision procedure works efficiently enough to use

Coulomb drag between two strange metals

We study the Coulomb drag between two strange-metal layers using the Einstein-Maxwell-Dilaton model from holography. We show that the low-temperature dependence of the drag resistivity is $\rho_D \propto T^4$, which strongly deviates from the quadratic dependence of Fermi liquids. We also present numerical results at room temperature, using typical parameters of the cuprates, to provide an estimate of the magnitude of this effect for future experiments. We find that the drag resistivity is enhanced by the plasmons characteristic of the two-layer system.Comment: 5 pages, 3 figure

Social Dilemmas and Cooperation in Complex Networks

In this paper we extend the investigation of cooperation in some classical evolutionary games on populations were the network of interactions among individuals is of the scale-free type. We show that the update rule, the payoff computation and, to some extent the timing of the operations, have a marked influence on the transient dynamics and on the amount of cooperation that can be established at equilibrium. We also study the dynamical behavior of the populations and their evolutionary stability.Comment: 12 pages, 7 figures. to appea

The synergistic effect between positivity, socio-demographic factors and smoking cessation: results of a cohort study

OBJECTIVE: To examine the extent to which a effect does exist between Positivity (POS), smoking and socio-demographic factors in determining quitting smoking in subjects participating in a Group Counselling Program (GCP) for smoking cessation.METHODS: 481 subjects were contacted through a telephone call. A logistic regression analysis was carried out. Possible interaction between sociodemographic variables and POS level was tested using the Synergism Index (SI).RESULTS: For individuals with a POS level over or equal to 3.4 the odds of being smoker was significantly higher among females (OR = 1.55), who smoked at home (OR = 2.16) and lower if there had children at home (OR = 0.53). For individuals with a POS level under 3.4, the only significant variable associated with smoking was beinga female (OR = 2.58). As far concerns the synergistic effect between the variables considered does exist between POS levels and having children at home (SI=1.13) and female gender (SI = 2.8).CONCLUSIONS: The synergistic effect between POS and sociodemographic factors adds evidence on the use of POS as possible determinants of individual happiness

Evolution of Coordination in Social Networks: A Numerical Study

Coordination games are important to explain efficient and desirable social behavior. Here we study these games by extensive numerical simulation on networked social structures using an evolutionary approach. We show that local network effects may promote selection of efficient equilibria in both pure and general coordination games and may explain social polarization. These results are put into perspective with respect to known theoretical results. The main insight we obtain is that clustering, and especially community structure in social networks has a positive role in promoting socially efficient outcomes.Comment: preprint submitted to IJMP

The Tree Width of Separation Logic with Recursive Definitions

Separation Logic is a widely used formalism for describing dynamically allocated linked data structures, such as lists, trees, etc. The decidability status of various fragments of the logic constitutes a long standing open problem. Current results report on techniques to decide satisfiability and validity of entailments for Separation Logic(s) over lists (possibly with data). In this paper we establish a more general decidability result. We prove that any Separation Logic formula using rather general recursively defined predicates is decidable for satisfiability, and moreover, entailments between such formulae are decidable for validity. These predicates are general enough to define (doubly-) linked lists, trees, and structures more general than trees, such as trees whose leaves are chained in a list. The decidability proofs are by reduction to decidability of Monadic Second Order Logic on graphs with bounded tree width.Comment: 30 pages, 2 figure

Approximate Consistency Condition from Running Spectral Index in Slow-Roll Inflationary Models

Density perturbations generated from inflation almost always have a spectral index n_s which runs (varies with the wavelength). We explore a running spectral index scenario in which the scalar spectral index runs from blue (n_s >1) on large length scales to red (n_s<1) on short length scales. Specifically, we look for a correlation between the length scale at which n_s-1=0 and the length scale at which tensor to scalar ratio T/S reaches a minimum for single field slow roll inflationary models. By computing the distribution of length scale ratios, we conclude that there indeed is a new approximate consistency condition that is characteristic of running spectral index scenarios that run from blue to red. Specifically, with strong running, we expect 96% of the slow roll models to have the two length scales to be within a factor of 2, with the length scale at which the tensor to scalar ratio reaching a minimum longer than the wavelength at which n_s-1=0.Comment: 18 pages, 2 figure

Food safety risk analysis from the producers' perspective: prioritisation of production process stages by HACCP and TOPSIS

[EN] From the manufacturers perspective, the Hazard Analysis and Critical Control Point (HACCP) system nowadays represents the mainly way to implement the food safety risk management in food industries. Nevertheless, the identification and prioritization of hazards as the outcome of the first principle of HACCP is not sufficient to identify production process stages that more significantly and critically contribute to the consumer¿s risks. With this recognition, the present paper proposes a Quantitative Risk Assessment (QRA) approach based on HACCP and Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to individuate production process phases on which implementing corrective actions to improve the consumers¿ safety. The designed methodological approach is implemented on the smoked salmon manufacturing process of a real Sicilian industry.Certa, A.; Enea, M.; Galante, G.; Izquierdo Sebastián, J.; La Fata, CM. (2018). Food safety risk analysis from the producers' perspective: prioritisation of production process stages by HACCP and TOPSIS. International Journal of Management and Decision Making. 17(4):396-414. https://doi.org/10.1504/IJMDM.2018.095720S39641417