Generic Action Research Articles

A NOTE ON TWO-DIMENSIONAL DILATON GRAVITY WITH NON-SMOOTH POTENTIALS

Recent interest in brane world models motivates the investigation of generic first-order dilaton gravity actions, with potentials having some non-smoothness. We consider two different types of δ-like contributions in the action and analyse their effects on the solutions. Furthermore a second source of non-smoothness arises due to the remaining ambiguities in the solutions in the separated smooth patches, after fixing all other constants by matching and asymptotic conditions. If moreover staticity is assumed, we explicitly construct exact solutions. With the methods described, for example models with point like sources or brane world models (where the second source of non-smoothness becomes crucial), can now be treated as non-smooth dilaton gravity theories.

Supertubes versus superconducting tubes

In this paper we show the relationship between cylindrical D2-branes and cylindrical superconducting membranes described by a generic effective action at the bosonic level. In the first case the extended objects considered, arose as blown up type IIA superstrings to D2-branes, named supertubes. In the second one, the cosmological objects arose from some sort of field theories. The Dirac–Born–Infeld action describing supertubes is shown to be equivalent to the generic effective action describing superconducting membranes via a special transformation.

Quadratic metric‐affine gravity

AbstractWe consider spacetime to be a connected real 4‐manifold equipped with a Lorentzian metric and an affine connection. The 10 independent components of the (symmetric) metric tensor and the 64 connection coefficients are the unknowns of our theory. We introduce an action which is (purely) quadratic in curvature and study the resulting system of Euler–Lagrange equations. In the first part of the paper we look for Riemannian solutions, i.e. solutions whose connection is Levi‐Civita. We find two classes of Riemannian solutions: 1) Einstein spaces, and 2) spacetimes with pp‐wave metric of parallel Ricci curvature. We prove that for a generic quadratic action these are the only Riemannian solutions. In the second part of the paper we look for non‐Riemannian solutions. We define the notion of a “Weyl pseudoinstanton” (metric compatible spacetime whose curvature is purely of Weyl type) and prove that a Weyl pseudoinstanton is a solution of our field equations. Using the pseudoinstanton approach we construct explicitly a non‐Riemannian solution which is a wave of torsion in a spacetime with Minkowski metric. We discuss the possibility of using this non‐Riemannian solution as a mathematical model for the neutrino.

Quadratic metric-affine gravity

We consider spacetime to be a connected real 4-manifold equipped with a Lorentzian metric and an affine connection. The 10 independent components of the (symmetric) metric tensor and the 64 connection coefficients are the unknowns of our theory. We introduce an action which is (purely) quadratic in curvature and study the resulting system of Euler–Lagrange equations. In the first part of the paper we look for Riemannian solutions, i.e. solutions whose connection is Levi-Civita. We find two classes of Riemannian solutions: 1) Einstein spaces, and 2) spacetimes with pp-wave metric of parallel Ricci curvature. We prove that for a generic quadratic action these are the only Riemannian solutions. In the second part of the paper we look for non-Riemannian solutions. We define the notion of a “Weyl pseudoinstanton” (metric compatible spacetime whose curvature is purely of Weyl type) and prove that a Weyl pseudoinstanton is a solution of our field equations. Using the pseudoinstanton approach we construct explicitly a non-Riemannian solution which is a wave of torsion in a spacetime with Minkowski metric. We discuss the possibility of using this non-Riemannian solution as a mathematical model for the neutrino.

On the dynamics of generic non-Abelian free actions

We investigate some global generic properties of the dynamics associated to non-Abelian free actions in certain special cases. The main properties considered in this paper are related to the existence of dense orbits, to ergodicity and to topological rigidity. We first deal with them in the case of conservative homeomorphisms of a manifold and C 1-diffeomorphisms of a surface. Groups of analytic diffeomorphisms of a manifold which, in addition, contain a Morse-Smale element and possess a generating set close to the identity are considered as well. From our discussion we also derive the existence of a rigidity phenomenon for groups of skew-products which is opposed to the phenomenon present in Furstenberg’s celebrated example of a minimal diffeomorphism that is not ergodic (cf. [Ma]).

Experiences in methods to involve key players in planning protective actions in the case of a nuclear accident.

A widely used method in the planning of protective actions is to establish a stakeholder network to generate a comprehensive set of generic protective actions. The aim is to increase competence and build links for communication and coordination. The approach of this work was to systematically evaluate protective action strategies in the case of a nuclear accident. This was done in a way that the concerns and issues of all key players could be transparently and equally included in the decision taken. An approach called Facilitated Decision Analysis Workshop has been developed and tested. The work builds on case studies in which it was assumed that a hypothetical accident had led to a release of considerable amounts of radionuclides and, therefore, various types of countermeasures had to be considered. Six workshops were organised in the Nordic countries where the key players were represented, i.e. authorities, expert organisations, industry and agricultural producers.

SPICE for SPACE trials, risk analysis, and process improvement

AbstractAs part of a programme for software process improvement sponsored by the European Space Agency (ESA), an ISO 15504 (1998) conformant method for software process assessment has been developed. [Work supported under ESTEC Contract Number 10 662/93/NL/NB CCN5.] Called SPICE for SPACE, or S4S (Völcker and Cass 2002, Cass et al. 2000), the method includes an assessment model based on the ISO/IEC TR 15504 exemplar model with space software practices incorporated.To promote SPICE for SPACE, ESA has sponsored a series of trial assessments using the S4S method. Since February 2000, eight space software suppliers have been assessed in Austria, Belgium, Denmark, Germany, Great Britain, Italy, and Sweden.The first part of this paper describes the trial assessment programme to date, summarising the assessments that have taken place, the assessment results, the improvement efforts initiated in the host organisations, and the feedback gathered to improve the S4S method.The second part of this paper presents a new approach for software process improvement based on a risk analysis of assessment results. Developed within the same initiative, this method sets the basis for integrating process‐oriented risk analysis into the S4S method, where, along with the process and capability dimensions, risk can be considered as a new third dimension. The outcomes of the risk analysis lead to the selection and prioritisation of pre‐defined generic improvement actions. Alternatively, the risk analysis presented here can be applied in the context of supplier evaluation or risk estimation for investors in software organisations. Copyright © 2004 John Wiley & Sons, Ltd.

Quadratic non-Riemannian Gravity

We consider spacetime to be a connected real 4-manifold equipped with a Lorentzian metric and an affine connection. The 10 independent components of the (symmetric) metric tensor and the 64 connection coefficients are the unknowns of our theory. We introduce an action which is quadratic in curvature and study the resulting system of Euler–Lagrange equations. In the first part of the paper we look for Riemannian solutions, i.e. solutions whose connection is Levi-Civita. We find two classes of Riemannian solutions: 1) Einstein spaces, and 2) spacetimes with metric of a pp-wave and parallel Ricci curvature. We prove that for a generic quadratic action these are the only Riemannian solutions. In the second part we look for non-Riemannian solutions. We define the notion of a “Weyl pseudoinstanton” (metric compatible spacetime whose curvature is purely Weyl) and prove that a Weyl pseudoinstanton is a solution of our field equations. Using the pseudoinstanton approach we construct explicitly a non-Riemannian solution which is a wave of torsion in Minkowski space.

Walking a Fine Line: Writing Negative Letters in an Insurance Company

This limited case study examines the situated-language practices associated with the production of negative letters in an insurance company. Using genre and sociocultural theories, the study combines textual analyses of a set of negative letters together with writers’ accounts of producing these letters to identify effective (as defined by the company) strategies for composing this correspondence. These letters are examples of generic action, and they demonstrate that genres function as constellations of regulated, improvisational strategies triggered by the interaction between individual socialization and an organization. Moreover, these constellations of resources express a particular chronotopic relation to space and time, and this relation is always axiological or value oriented. In other words, genres express space/time relations that reflect current social beliefs regarding the placement and actions of human individuals in space and time. The article identifies some of the strategies that characteri...

Weak equivalence of cocycles and Mackey action in generic dynamics

LetR be an equivalence relation generated by a countable ergodic homeomorphism group of a perfect Polish spaceX. We consider cocycles taking values in Polish groups onR modulo meager subsets ofX. Two cocycles are called weakly equivalent if they are cohomologous up to an automorphism ofR. The notion of generic associated Mackey action is introduced, which is an invariant of weak equivalence for cocycles. Regular cocycles with values in an arbitrary Polish group and transient cocycles with values in an arbitrary countable group are completely classified up to weak equivalence.

Quaternionic extension of the double Taub-NUT metric

Starting from the generic harmonic superspace action of the quaternion-Kähler sigma models and using the quotient approach we present, in an explicit form, a quaternion-Kähler extension of the double Taub-NUT metric. It possesses U(1)× U(1) isometry and supplies a new example of non-homogeneous Einstein metric with self-dual Weyl tensor.

Walking a Fine Line

This limited case study examines the situated-language practices associated with the production of negative letters in an insurance company. Using genre and sociocultural theories, the study combines textual analyses of a set of negative letters together with writers’ accounts of producing these letters to identify effective (as defined by the company) strategies for composing this correspondence. These letters are examples of generic action, and they demonstrate that genres function as constellations of regulated, improvisational strategies triggered by the interaction between individual socialization and an organization. Moreover, these constellations of resources express a particular chronotopic relation to space and time, and this relation is always axiological or value oriented. In other words, genres express space/time relations that reflect current social beliefs regarding the placement and actions of human individuals in space and time. The article identifies some of the strategies that characterize effective negative messages in this organization. It also critiques this text type for enacting a set of practices and related chronotopic orientation that are against the interests of its readers and writers.

Adapting to Hostile Architectural Environments

Adapting to Hostile Architectural Environments

Self-duality in super D3-brane action

We establish self-duality of super D3-brane theory as an exact symmetry of the action both in the Lagrangian and Hamiltonian formalisms. In the Lagrangian formalism, the action is shown to satisfy the Gaillard-Zumino condition. This algebraic relation is recognized in our previous paper to be a necessary and sufficient condition for generic action of U(1) gauge field strength coupled with gravity and matters to be self-dual. For the super D3-brane action, SO(22) duality transformation of a world-volume gauge field should be associated with SO(2) rotation of fermionic brane coordinates in the N = 2 SUSY multiplet. This SO(2) duality symmetry is lifted to SL(2, R ) symmetry in the presence of a dilaton and axion background fields. In the canonical formalism, we show that the duality rotation is described by a canonical transformation, and the Hamiltonian of the D3-brane action is invariant under the transformation.

The three–form multiplet in $N = 2$ superspace

We present an N=2 multiplet including a three-index antisymmetric tensor gauge potential, and describe it as a solution to the Bianchi identities for the associated fieldstrength superform, subject to some covariant constraints, in extended central charge superspace. We find that this solution is given in terms of an 8+8 tensor multiplet subject to an additional constraint. We give the transformation laws for the multiplet as well as invariant superfield and component field lagrangians, and mention possible couplings to other multiplets. We also allude to the relevance of the 3--form geometry for generic invariant supergravity actions.

Standards for Soil Contamination: Results of a Federal/State Working Group

The German Soil Protection Legislation (draft) proposes generic soil trigger levels and action levels to assess contaminated sites. This article presents results of a working group set up by the Bundl Länder-Arbeitsgemeinschaft “Bodenschutz” (LABO) and the Länder-Arbeitsgemeinschaft “Abfall” (LAGA). The report on key issues for assessing public health effects of contaminated land for 14 substances of prime importance also has been negotiated with the Arbeitsgemeinschaft der Leitenden Medizinalbeamten der Länder (AGLMB [health service]). The report introduces toxicological reference data indicating a virtually safe body dose and a factor deriving a hazardous body dose, which will be used to calculate soil trigger levels. Calculations are based on exposure estimates covering the inhalative andingestive routes of exposure. Results of the calculations are to be checked against soil background data.

Variational Approach to Relaxation in Complex Free Energy Landscapes: The Polymer Folding Problem

A statistical theory of the folding dynamics of an ensemble of random heteropolymers is developed. The predicted relaxation is consistent with the glassy behavior of quenched disorder and is singled out by a generic least action principle: In processes of increasing difficulty, the logarithmic growth in time of the expected activation barrier yields the fastest relaxation pathway.

A Petri net algorithm for scheduling of generic restoration actions

This paper is concerned with scheduling of the restoration actions. Generic restoration actions (GRAs) have been identified in the authors' previous research based on a variety of restoration strategies used by electric utilities. This paper proposed a scheduling method using the Petri net (PN) techniques. The PN model incorporates the conditions that have to be met before an action can be taken. The time required to perform an action is also modeled in the net. A token passing and a backward search process are used to identify the sequence of restoration actions and their timing. The advantages of the proposed methods are: (1) the time required to restore a subsystem can be estimated; (2) a systematical method is obtained for identification of the sequence of actions. The BN method has been tested with simulation cases.

From generic restoration actions to specific restoration strategies

The results presented here reflect work, extending over several years, to identify features underlying restoration processes that are common to almost all utilities and that can serve as guides for preparing and evaluating restoration plans, for developing expert system programs that will be widely useful, and ultimately for improving the effectiveness of restoration practices. Generality is achieved by identifying constituent elements of the process, namely a "target system", "restoration building blocks (RBBs)", "generic restoration actions (GRAs)", and process constraints, and the factors that distinguish among three clearly demarcated stages. This distillation of the constituent elements of the restoration process provides a basis for development of a comprehensive, knowledge-based restoration expert system appropriate to a broad spectrum of power system utilities.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Sigma models in (4, 4) harmonic superspace

We define the basics of (4, 4) 2 D harmonic superspace with two independent sets of SU(2) harmonic variables and apply it to constructing new superfield actions of (4, 4) supersymmetric two-dimensional sigma models with torsion and mutually commuting left and right complex structures, as well as of their massive deformations. We show that the generic off-shell sigma model action is the general action of constrained analytic superfields q (1,1) representing twisted N = 4 multiplets in (4, 4) harmonic superspace. The massive term of q (1,1) is shown to be unique; it generates a scalar potential the form of which is determined by the metric on the target bosonic manifold. We discuss in detail the (4, 4) supersymmetric group manifold SU(2) × U(1) WZNW sigma model and its Liouville deformation. A deep analogy of the relevant superconformally invariant analytic superfield action to that of the improved tensor N = 2 4 D multiplet is found. We define the (4, 4) duality transformation and find new off-shell dual representations of the previously constructed actions via unconstrained analytic (4, 4) superfields. The main peculiarities of the (4, 4) duality transformation are: (i) it preserves manifest (4, 4) supersymmetry; (ii) dual actions reveal a gauge invariance needed for the on-shell equivalence to the original description; (iii) in the actions dual to the massive ones, 2 D supersymmetry is modified off shell by SU(2) tensor central charges. The dual representation suggests some hints of how to describe (4, 4) models with non-commuting complex structures in the harmonic superspace.