Observation of an optical non-Fermi-liquid behavior in the heavy fermion state of YbRh2_{2}Si2_{2}

We report far-infrared optical properties of YbRh$_{2}$Si$_{2}$ for photon energies down to 2 meV and temperatures 0.4 -- 300 K. In the coherent heavy quasiparticle state, a linear dependence of the low-energy scattering rate on both temperature and photon energy was found. We relate this distinct dynamical behavior different from that of Fermi liquid materials to the non-Fermi liquid nature of YbRh$_{2}$Si$_{2}$ which is due to its close vicinity to an antiferromagnetic quantum critical point.Comment: 5 pages, 4 figures. submitte

How are affective word ratings related to lexicosemantic properties?:evidence from the Sussex Affective Word List

Emotional content of verbal material affects the speed of visual word recognition in various cognitive tasks, independently of lexicosemantic variables. However, little is known about how the dimensions of emotional arousal and valence interact with the lexicosemantic properties of words such as age of acquisition, familiarity, and imageability, that determine word recognition performance. This study aimed to examine these relationships using English ratings for affective and lexicosemantic features. Eighty-two native English speakers rated 300 words for emotional valence, arousal, familiarity, age of acquisition, and imageability. Although both dimensions of emotion were correlated with lexicosemantic variables, a unique emotion cluster produced the strongest quadratic relationship. This finding suggests that emotion should be included in models of word recognition as it is likely to make an independent contribution

Effects of valence and arousal on written word recognition:Time course and ERP correlates

Models of affect assume a two-dimensional framework, composed of emotional valence and arousal. Although neuroimaging evidence supports a neuro-functional distinction of their effects during single word processing, electrophysiological studies have not yet compared the effects of arousal within the same category of valence (positive and negative). Here we investigate effects of arousal and valence on written lexical decision. Amplitude differences between emotion and neutral words were seen in the early posterior negativity (EPN), the late positive complex and in a sustained slow positivity. In addition, trends towards interactive effects of valence and arousal were observed in the EPN, showing larger amplitude for positive, high-arousal and negative, low-arousal words. The results provide initial evidence for interactions between arousal and valence during processing of positive words and highlight the importance of both variables in studies of emotional stimulus processing. Crown Copyright (C) 2012 Published by Elsevier Ireland Ltd. All rights reserved

Low-temperature thermopower study of YbRh2Si2

The heavy-fermion compound YbRh2Si2 exhibits an antiferromagnetic (AFM) phase transition at an extremely low temperature of TN = 70 mK. Upon applying a tiny magnetic field of Bc = 60 mT the AFM ordering is suppressed and the system is driven toward a field-induced quantum critical point (QCP). Here, we present low-temperature thermopower S(T) measurements of high-quality YbRh2Si2 single crystals down to 30 mK. S(T) is found negative with comparably large values in the paramagnetic state. In zero field no Landau-Fermi-liquid (LFL) like behavior is observed within the magnetically ordered phase. However, a sign change from negative to positive appears at lowest temperatures on the magnetic side of the QCP. For higher fields B > Bc a linear extrapolation of S to zero clearly evidences the recovery of LFL regime. The crossover temperature is sharply determined and coincides perfectly with the one derived from resistivity and specific heat investigations.Comment: LT25 conference proceedings in Journal of Physics: Conference Serie

Arousal and emotional valence interact in written word recognition

Behavioural, psychophysiological and neuroimaging studies reveal a prioritisation for emotional material in a variety of cognitive tasks. Although emotion is comprised of two dimensions (valence and arousal), previous research using verbal materials has mostly focused on valence, while controlling level of arousal. The aim of the present study is to investigate the effects of valence and arousal on lexical decision (LD) by manipulating both dimensions while controlling correlated psycholinguistic variables (e.g., word length, frequency, imageability). Results showed that valence and arousal affect word recognition in an interactive way: LD latencies are slower for positive high-arousal and negative low-arousal words compared to positive low-arousal and negative high-arousal words, in line with an approach-withdrawal tendency model. Furthermore, principal component analysis (PCA) on the latencies revealed a unique contribution of a distinct cluster of emotion variables, independent of lexico-semantic variables, to explaining written word recognition. We conclude that the dimensions of valence and arousal both need to be taken into account in studies of emotion word processing as they have an interactive relationship

Gravitating Instantons In 3 Dimensions

We study the Einstein-Chern-Simons gravity coupled to Yang-Mills-Higgs theory in three dimensional Euclidean space with cosmological constant. The classical equations reduce to Bogomol'nyi type first order equations in curved space. There are BPS type gauge theory instanton (monopole) solutions of finite action in a gravitational instanton which itself has a finite action. We also discuss gauge theory instantons in the vacuum (zero action) AdS space. In addition we point out to some exact solutions which are singular.Comment: 17 pages, 4 figures, title has changed, gravitational instanton actions are adde

The HERMES Back Drift Chambers

The tracking system of the HERMES spectrometer behind the bending magnet consists of two pairs of large planar 6-plane drift chambers. The design and performance of these chambers is described. This description comprises details on the mechanical and electronical design, information about the gas mixture used and its properties, results on alignment, calibration, resolution, and efficiencies, and a discussion of the experience gained through the first three years of operation.Comment: 21 pages, LaTex, 16 figures include

Yang-Mills Solutions on Euclidean Schwarzschild Space

We show that the apparently periodic Charap-Duff Yang-Mills `instantons' in time-compactified Euclidean Schwarzschild space are actually time independent. For these solutions, the Yang-Mills potential is constant along the time direction (no barrier) and therefore, there is no tunneling. We also demonstrate that the solutions found to date are three dimensional monopoles and dyons. We conjecture that there are no time-dependent solutions in the Euclidean Schwarzschild background.Comment: 12 pages, references added, version to appear in PR

On sense and reference: examining the functional neuroanatomy of referential processing

In an event-related fMRI study, we examined the cortical networks involved in establishing. reference during language comprehension. We compared BOLD responses to sentences containing referentially ambiguous pronouns (e.g., "Ronald told Frank that he..."), referentially failing pronouns (e.g., "Rose told Emily that he...") or coherent pronouns. Referential ambiguity selectively recruited media[ prefrontal regions, suggesting that readers engaged in problemsolving to select a unique referent from the discourse model. Referential failure elicited activation increases in brain regions associated with mo rp ho -syntactic processing, and, for those readers who took failing pronouns to refer to unmentioned entities, additional regions associated with elaborative inferencing were observed. The networks activated by these two referential problems did not overlap with the network activated by a standard semantic anomaly. Instead, we observed a double dissociation, in that the systems activated by semantic anomaly are deactivated by referential ambiguity, and vice versa. This inverse coupling may reflect the dynamic recruitment of semantic and episodic processing to resolve semantically or referentially problematic situations. More generally, our findings suggest that neurocognitive accounts of language comprehension need to address not just how we parse a sentence and combine individual word meanings, but also how we determine who's who and what's what during language COmprehension. (c) 2007 Elsevier Inc. All rights reserved