Quantum inequalities in two dimensional Minkowski spacetime

We generalize some results of Ford and Roman constraining the possible behaviors of renormalized expected stress-energy tensors of a free massless scalar field in two dimensional Minkowski spacetime. Ford and Roman showed that the energy density measured by an inertial observer, when averaged with respect to that observers proper time by integrating against some weighting function, is bounded below by a negative lower bound proportional to the reciprocal of the square of the averaging timescale. However, the proof required a particular choice for the weighting function. We extend the Ford-Roman result in two ways: (i) We calculate the optimum (maximum possible) lower bound and characterize the state which achieves this lower bound; the optimum lower bound differs by a factor of three from the bound derived by Ford and Roman for their choice of smearing function. (ii) We calculate the lower bound for arbitrary, smooth positive weighting functions. We also derive similar lower bounds on the spatial average of energy density at a fixed moment of time.Comment: 6 pages, no figures, uses revtex 3.1 macros, to appear in Phys Rev D. Minor revisions and generalizations added 7/16/9

Making molehills into mountains: Adult responses to child sexuality and behaviour

Sexual behaviour among children can be perplexing for adults as they negotiate a spectrum of ideas relating to abuse and natural curiosity. In the search for understandings, adults can act in ways that close opportunities for children to explore and describe meanings for the behaviour. This article invites practitioners to check their assumptions in this kind of work, and to take a stance that opposes abusive actions – while taking up a position of enquiry to support the multiple stories that make up children’s lives

Ethical beginnings: Reflexive questioning in designing child sexuality research

Counselling young children referred for sexualised behaviour can challenge therapists’ ideas about childhood and sexuality. This area of practice is complex and sensitive, and calls upon collaboration with a range of significant adults in children's lives. Purpose: This paper examines a researcher's process of movement from counselling practice into qualitative research practice, and the use of reflexive questioning to explore ethical issues within the study. Design: Shaped by social constructionist ideas and discourse theory, ethical questions are outlined within the design stage of a doctoral research project on sexuality in children's lives in Aotearoa New Zealand. Limitations: This paper explores ethics in the design of a current study: there are no results or conclusions

A Unified Framework for Linear-Programming Based Communication Receivers

It is shown that a large class of communication systems which admit a sum-product algorithm (SPA) based receiver also admit a corresponding linear-programming (LP) based receiver. The two receivers have a relationship defined by the local structure of the underlying graphical model, and are inhibited by the same phenomenon, which we call 'pseudoconfigurations'. This concept is a generalization of the concept of 'pseudocodewords' for linear codes. It is proved that the LP receiver has the 'maximum likelihood certificate' property, and that the receiver output is the lowest cost pseudoconfiguration. Equivalence of graph-cover pseudoconfigurations and linear-programming pseudoconfigurations is also proved. A concept of 'system pseudodistance' is defined which generalizes the existing concept of pseudodistance for binary and nonbinary linear codes. It is demonstrated how the LP design technique may be applied to the problem of joint equalization and decoding of coded transmissions over a frequency selective channel, and a simulation-based analysis of the error events of the resulting LP receiver is also provided. For this particular application, the proposed LP receiver is shown to be competitive with other receivers, and to be capable of outperforming turbo equalization in bit and frame error rate performance.Comment: 13 pages, 6 figures. To appear in the IEEE Transactions on Communication

The effects of isotopic separation on closed nuclear fuel cycles

This paper investigates the potential benefits to the fuel cycle outcomes of removing a single isotope during separation processes. Two strategies for managing the removed isotope are considered. The first strategy looks at removal of a short to intermediate lived isotope from a mass stream to be recycled and subsequently recycling its decay daughter in a transmuting reactor. The second investigates the effect of removing a long lived fission product from high level waste and recycling it into the transmuting reactor. This analysis shows that the removal of Cm-244 using the first strategy provides a marked benefit to several fuel cycle metrics. The second strategy benefits the long term radioactivity measured from the high level waste from isotopes including Zr-93 and Cs-137.Mechanical Engineerin