27,299 research outputs found

    Anomalously small wave tails in higher dimensions

    Full text link
    We consider the late-time tails of spherical waves propagating on even-dimensional Minkowski spacetime under the influence of a long range radial potential. We show that in six and higher even dimensions there exist exceptional potentials for which the tail has an anomalously small amplitude and fast decay. Along the way we clarify and amend some confounding arguments and statements in the literature of the subject.Comment: 13 page

    The Geoff Egan Memorial Lecture 2011. Artefacts, art and artifice: reconsidering iconographic sources for archaeological objects in early modern Europe

    Get PDF
    A first systematic analysis of historic domestic material culture depicted in contemporaneous Western painting and prints, c.1400-1800. Drawing on an extensive data set, the paper proposes to methodologies and hermeneutics for historical analysis and archaeological correspondence

    Representation of Quantum Mechanical Resonances in the Lax-Phillips Hilbert Space

    Get PDF
    We discuss the quantum Lax-Phillips theory of scattering and unstable systems. In this framework, the decay of an unstable system is described by a semigroup. The spectrum of the generator of the semigroup corresponds to the singularities of the Lax-Phillips SS-matrix. In the case of discrete (complex) spectrum of the generator of the semigroup, associated with resonances, the decay law is exactly exponential. The states corresponding to these resonances (eigenfunctions of the generator of the semigroup) lie in the Lax-Phillips Hilbert space, and therefore all physical properties of the resonant states can be computed. We show that the Lax-Phillips SS-matrix is unitarily related to the SS-matrix of standard scattering theory by a unitary transformation parametrized by the spectral variable σ\sigma of the Lax-Phillips theory. Analytic continuation in σ\sigma has some of the properties of a method developed some time ago for application to dilation analytic potentials. We work out an illustrative example using a Lee-Friedrichs model for the underlying dynamical system.Comment: Plain TeX, 26 pages. Minor revision

    An exploration into the client at the heart of therapy : a qualitative perspective

    Get PDF
    Over 50 years ago Eysenck challenged the existing base of research into psychotherapy. Since that time, a large number of investigations have been conducted to verify the efficacy of therapy. Recently however, an increasing number of studies have cast new doubts on this research base. Instead of therapy being a function of the therapist, it is now becoming ever more apparent that the client plays a prime role in the therapeutic process. The qualitative studies presented in this paper provide some examples of research that demonstrates that clients are actively involved in their therapy, even making counselling work despite their counsellor. These studies suggest that clients may not experience therapy as beneficially as traditional outcome studies indicate. This raises a new challenge to researchers to more fully explore the client's experience of therapy, a challenge to which qualitative methods of inquiry would appear well suited

    Searching For Integrated Sachs-Wolfe Effect Beyond Temperature Anisotropies: CMB E-mode Polarization-Galaxy Cross Correlation

    Get PDF
    The cross-correlation between cosmic microwave background (CMB) temperature anisotropies and the large scale structure (LSS) traced by the galaxy distribution, or sources at different wavelengths, is now well known. This correlation results from the integrated Sachs-Wolfe (ISW) effect in CMB anisotropies generated at late times due to the dark energy component of the Universe. In a reionized universe, the ISW quadrupole rescatters and contributes to the large-scale polarization signal. Thus, in principle, the large-scale polarization bump in the E-mode should also be correlated with the galaxy distribution. Unlike CMB temperature-LSS correlation that peaks for tracers at low redshifts this correlation peaks mostly at redshifts between 1 and 3. Under certain conditions, mostly involving a low optical depth to reionization, if the Universe reionized at a redshift around 6, the cross polarization-source signal is marginally detectable, though challenging as it requires all-sky maps of the large scale structure at redshifts between 1 and 3. If the Universe reionized at a redshift higher than 10, it is unlikely that this correlation will be detectable even with no instrumental noise all-sky maps. While our estimates do not guarantee a detection unknown physics related to the dark energy as well as still uncertain issues related to the large angular scale CMB and polarization anisotropies may motivate attempts to measure this correlation using upcoming CMB polarization E-mode maps.Comment: 13 pages; 3 figure panels, JCAP submitte
    • 

    corecore