Infrared regularization for spin-1 fields

We extend the method of infrared regularization to spin-1 fields. As applications, we discuss the chiral extrapolation of the rho meson mass from lattice QCD data and the pion-rho sigma term.Comment: 22 pp, 5 fig

Access-Control Policies via Belnap Logic: Effective and Efficient Composition and Analysis

It is difficult to develop and manage large, multi-author access control policies without a means to compose larger policies from smaller ones. Ideally, an access-control policy language will have a small set of simple policy combinators that allow for all desired policy compositions. In [5], a policy language was presented having policy combinators based on Belnap logic, a four-valued logic in which truth values correspond to policy results of grant , deny , conflict , and undefined . We show here how policies in this language can be analyzed, and study the expressiveness of the language. To support policy analysis, we define a query language in which policy analysis questions can be phrased. Queries can be translated into a fragment of first-order logic for which satisfiability and validity checks are computable by SAT solvers or BDDs. We show how policy analysis can then be carried out through model checking, validity checking, and assume-guarantee reasoning over such translated queries. We also present static analysis methods for the particular questions of whether policies contain gaps or conflicts. Finally, we establish expressiveness results showing that all data independent policies can be expressed in our policy language. © 2008 IEEE

Foraging behavior and Doppler shift compensation in echolocating hipposiderid bats, I-Iipposideros bicolor and I-Iipposideros speoris

1. Two hipposiderid bats,H. bicolor andH. speoris, were observed in their natural foraging areas in Madurai (South India). Both species hunt close together near the foliage of trees and bushes but they differ in fine structure of preferred hunting space:H. bicolor hunts within the foliage, especially whenH. speoris is active at the same time, whereasH. speoris never flies in dense vegetation but rather in the more open area (Fig. 1, Table 1). 2. Both species emit CF/FM-sounds containing only one harmonic component in almost all echolocation situations. The CF-parts of CF/FM-sounds are species specific within a band of 127–138 kHz forH. speoris and 147–159 kHz forH. bicolor (Tables 2 and 3). 3. H. speoris additionally uses a complex harmonic sound during obstacle avoidance and during laboratory tests for Doppler shift compensation.H. bicolor consistently emits CF/FM-sounds in these same situations (Fig. 2). 4. Both hipposiderid bats respond to Doppler shifts in the returning echoes by lowering the frequency of the emitted sounds (Fig. 3). However, Doppler compensations are incomplete as the emitted frequencies are decreased by only 55% and 56% (mean values) of the full frequency shifts byH. speoris andH, bicolor, respectively. 5. The differences in Doppler shift compensation, echolocating and hunting behavior suggest thatH. speoris is less specialized on echolocation with CF/FM-sounds thanH. bicolor

Gauge invariance in two-particle scattering

It is shown how gauge invariance is obtained for the coupling of a photon to a two-body state described by the solution of the Bethe-Salpeter equation. This is illustrated both for a complex scalar field theory and for interaction kernels derived from chiral effective Lagrangians.Comment: 16 pages, 2 figures, references added and commented o

Access control via belnap logic: intuitive, expressive, and analyzable policy composition

Access control to IT systems increasingly relies on the ability to compose policies. There is thus bene t in any framework for policy composition that is intuitive, formal (and so \an- alyzable" and \implementable"), expressive, independent of speci c application domains, and yet able to be extended to create domain-speci c instances. Here we develop such a framework based on Belnap logic. An access-control policy is interpreted as a four-valued predicate that maps access requests to either grant, deny, con ict, or unspeci ed { the four values of the Bel- nap bilattice. We de ne an expressive access-control policy language PBel, having composition operators based on the operators of Belnap logic. Natural orderings on policies are obtained by lifting the truth and information orderings of the Belnap bilattice. These orderings lead to a query language in which policy analyses, e.g. con ict freedom, can be speci ed. Policy analysis is supported through a reduction of the validity of policy queries to the validity of propositional formulas on predicates over access requests. We evaluate our approach through rewall policy and RBAC policy examples, and discuss domain-speci c and generic extensions of our policy language

Reliability analysis of dynamic systems by translating temporal fault trees into Bayesian networks

Classical combinatorial fault trees can be used to assess combinations of failures but are unable to capture sequences of faults, which are important in complex dynamic systems. A number of proposed techniques extend fault tree analysis for dynamic systems. One of such technique, Pandora, introduces temporal gates to capture the sequencing of events and allows qualitative analysis of temporal fault trees. Pandora can be easily integrated in model-based design and analysis techniques. It is, therefore, useful to explore the possible avenues for quantitative analysis of Pandora temporal fault trees, and we identify Bayesian Networks as a possible framework for such analysis. We describe how Pandora fault trees can be translated to Bayesian Networks for dynamic dependability analysis and demonstrate the process on a simplified fuel system model. The conversion facilitates predictive reliability analysis of Pandora fault trees, but also opens the way for post-hoc diagnostic analysis of failures

Three-dimensional compressible turbulent computations for a diffusing S-duct

The purpose of the present study was to evaluate the capability of the computational fluid dynamics computer program PARC3D to model flow in a typical diffusing subsonic S-duct, with strong secondary flows. This evaluation is needed to provide confidence in the analysis of aircraft inlets, which have similar geometries. The performance predictions include total pressure profiles, static pressures, velocity profiles, boundary layer data, and skin friction data. Flow in the S-duct is subsonic, and the boundary layers are assumed to be turbulent. The results for both H and O grid solutions, are compared with existing test data

Impact of soil management practices on soil fertility and disease suppressiveness

Soil management practices are targeted to provide adequate crop nutrition and to ensure durable soil fertility and to avoid negative environmental impacts. Soil management also aims to reduce pest and disease pressure on crops. Organic farming is believed to increase soil suppressiveness towards soil-borne diseases as well aerial diseases. In this paper we will discuss the potential of soil manage-ment as a tool to improve disease suppressiveness in practice