86 research outputs found
The Unity of Cosmological Attractors
Recently, several broad classes of inflationary models have been discovered
whose cosmological predictions are stable with respect to significant
modifications of the inflaton potential. Some classes of models are based on a
non-minimal coupling to gravity. These models, which we will call
-attractors, describe universal cosmological attractors (including Higgs
inflation) and induced inflation models. Another class describes conformal
attractors (including Starobinsky inflation and T-models) and their
generalization to -attractors. The aim of this paper is to elucidate
the common denominator of these models: their attractor properties stem from a
pole of order two in the kinetic term of the inflaton field in the Einstein
frame formulation, prior to switching to the canonical variables. We point out
that - and universal attractors differ in the subleading corrections to
the kinetic term. As a final step towards unification of and
attractors, we introduce a special class of -attractors which is fully
equivalent to -attractors with the identification . There is no theoretical lower bound on in this class of models.Comment: 6 pages 1 figure, Refs + minor clarifications adde
Pole Inflation - Shift Symmetry and Universal Corrections
An appealing explanation for the Planck data is provided by inflationary
models with a singular non-canonical kinetic term: a Laurent expansion of the
kinetic function translates into a potential with a nearly shift-symmetric
plateau in canonical fields. The shift symmetry can be broken at large field
values by including higher-order poles, which need to be hierarchically
suppressed in order not to spoil the inflationary plateau. The herefrom
resulting corrections to the inflationary dynamics and predictions are shown to
be universal at lowest order and possibly to induce power loss at large angular
scales. At lowest order there are no corrections from a pole of just one order
higher and we argue that this phenomenon is related to the well-known extended
no-scale structure arising in string theory scenarios. Finally, we outline
which other corrections may arise from string loop effects.Comment: twocolumn, 9 pages, 1 figure; v2: clarifications and refs added, JHEP
layout, 19 page
Time Driven Priority Router Implementation and First Experiments
This paper reports on the implementation of Time-Driven Priority (TDP) scheduling on a FreeBSD platform. This work is part of a TDP prototyping and demonstration project aimed at showing the implications of TDP deployment in packet-switched networks, especially benefits for real-time applications. This paper focuses on practical aspects related to the implementation of the technology on a Personal Computer (PC)-based router and presents the experimental results obtained on a testbed network. The basic building blocks of a TDP router are described and implementation choices are discussed. The relevant results achieved and here presented can be categorized into two types: qualitative results, including the successful integration of all needed blocks and the insight obtained on the complexity related to the implementation of a TDP router, and quantitative ones, including measures of achievable network utilization and of jitter experienced on a fully-loaded TDP network. The outcome demonstrates the effectiveness of the presented implementation while confirming TDP points of strengt
A multi-decision makers approach to select the maintenance plan for a multi-component system.
A multi-objective approach to solid waste management
The issue addressed in this paper consists in the localization and dimensioning of transfer stations, which constitute a necessary intermediate level in the logistic chain of the solid waste stream, from municipalities to the incinerator. Contextually, the determination of the number and type of vehicles involved is carried out in an integrated optimization approach. The model considers both initial investment and operative costs related to transportation and transfer stations. Two conflicting objectives are evaluated, the minimization of total cost and the minimization of environmental impact, measured by pollution. The design of the integrated waste management system is hence approached in a multi-objective optimization framework. To determine the best means of compromise, goal programming, weighted sum and fuzzy multi-objective techniques have been employed. The proposed analysis highlights how different attitudes of the decision maker towards the logic and structure of the problem result in the employment of different methodologies and the obtaining of different results. The novel aspect of the paper lies in the proposal of an effective decision support system for operative waste management, rather than a further contribution to the transportation problem. The model was applied to the waste management of optimal territorial ambit (OTA) of Palermo (Italy)
Multistage Switching Architectures for Software Routers
Software routers based on personal computer (PC) architectures are becoming an important alternative to proprietary and expensive network devices. However, software routers suffer from many limitations of the PC architecture, including, among others, limited bus and central processing unit (CPU) bandwidth, high memory access latency, limited scalability in terms of number of network interface cards, and lack of resilience mechanisms. Multistage PC-based architectures can be an interesting alternative since they permit us to i) increase the performance of single software routers, ii) scale router size, iii) distribute packet manipulation and control functionality, iv) recover from single-component failures, and v) incrementally upgrade router performance. We propose a specific multistage architecture, exploiting PC-based routers as switching elements, to build a high-speed, largesize,scalable, and reliable software router. A small-scale prototype of the multistage router is currently up and running in our labs, and performance evaluation is under wa
- …