A New Symmetry for QED

We demonstrate that QED exhibits a previously unobserved symmetry. Some consequences are discussed.Comment: 9 pages, MZ-TH/93-02, DIAS-STP-93-0

The embodiment of "good" and "bad" via vertical space : an investigation of conceptual metaphor in impression formation

A popular notion in psychology today is that cognition is embodied, such that the physical body and its interaction with the environment actively shape cognitive processes. According to one theory of embodied cognition, Conceptual Metaphor Theory (Lakoff & Johnson, 1980; 1999), people understand abstract concepts in terms of more concrete, physical domains. A conceptual metaphor that has been examined empirically is the GOOD IS UP conceptual metaphor (e.g., Meier & Robinson, 2004). This conceptual metaphor consists of an association between valence (good and bad) and verticality (up and down). The current project aimed to investigate whether the GOOD IS UP conceptual metaphor influences impression formation processes. This project consisted of four experiments in which reaction time, memory, and target evaluations were measured as dependent variables. Experiment 1 examined whether the vertical location of behavioural information influenced reaction time, memory, and target evaluations. Experiment 2A examined whether the vertical location of trait words influenced reaction time. Experiment 2B examined whether the vertical location of trait words influenced memory and target evaluations. Experiment 3 examined the reproducibility of Meier and Robinson’s (2004) original effect. Across the set of experiments, I hypothesised that the vertical location of the stimuli would influence reaction time, memory, and target evaluations in metaphor-consistent ways. However, this hypothesis was not supported. The current climate in psychological science is now beginning both to emphasise the importance of negative results and to encourage replication. The findings of the present project are discussed within this changing climate, which will better serve the development and refinement of Conceptual Metaphor Theory. Despite the negative results (i.e., p > .05), the four experiments are informative and provide direction for future research on conceptual metaphor and embodied cognition

Comparison of optimal performance at 300keV of three direct electron detectors for use in low dose electron microscopy

Low dose electron imaging applications such as electron cryo-microscopy are now benefitting from the improved performance and flexibility of recently introduced electron imaging detectors in which electrons are directly incident on backthinned CMOS sensors. There are currently three commercially available detectors of this type: the Direct Electron DE-20, the FEI Falcon II and the Gatan K2 Summit. These have different characteristics and so it is important to compare their imaging properties carefully with a view to optimise how each is used. Results at 300 keV for both the modulation transfer function (MTF) and the detective quantum efficiency (DQE) are presented. Of these, the DQE is the most important in the study of radiation sensitive samples where detector performance is crucial. We find that all three detectors have a better DQE than film. The K2 Summit has the best DQE at low spatial frequencies but with increasing spatial frequency its DQE falls below that of the Falcon II

Quantumness in decoherent quantum walk using measurement-induced disturbance

The classicalization of a decoherent discrete-time quantum walk on a line or an n-cycle can be demonstrated in various ways that do not necessarily provide a geometry-independent description. For example, the position probability distribution becomes increasingly Gaussian, with a concomitant fall in the standard deviation, in the former case, but not in the latter. As another example, each step of the quantum walk on a line may be subjected to an arbitrary phase gate, without affecting the position probability distribution, no matter whether the walk is noiseless or noisy. This symmetry, which is absent in the case of noiseless cyclic walk, but is restored in the presence of sufficient noise, serves as an indicator of classicalization, but only in the cyclic case. Here we show that the degree of quantum correlations between the coin and position degrees of freedom, quantified by a measure based on the disturbance induced by local measurements (Luo, Phys. Rev. A 77, 022301 (2008)), provides a suitable measure of classicalization across both type of walks. Applying this measure to compare the two walks, we find that cyclic quantum walks tend to classicalize faster than quantum walks on a line because of more efficient phase randomization due to the self-interference of the two counter-rotating waves. We model noise as acting on the coin, and given by the squeezed generalized amplitude damping (SGAD) channel, which generalizes the generalized amplitude damping channel.Comment: 8 pages with 8 figures, Published versio

Physical charges in QED and QCD

Talk given at the International Workshop on QCD Green's Functions, Confinement and Phenomenology, September 7-11 2009, ECT Trento, Italy. 8 pages, 3 pdf figures. V2: references added, to appear in PoSWe show that the `dressing' approach, which describes physical charges as gauge invariant composites of matter and clouds of gauge bosons, arises naturally in gauge theories. We give perturbative examples of dressings for both asymptotic charges and for states in which the fields are confined to a compact volume as is required, for example, by causality in pair creation. In QCD, we use dressed states to demonstrate explicitly how Gribov copies obstruct the non-perturbative construction of colour charges