On the checkerboard pattern and the autocorrelation of photoemission data in high temperature superconductors

In the pseudogap state the spectrum of the autocorrelation of angle resolved photoemission (AC-ARPES) data of Bi2212 presents non-dispersive peaks in momentum space which compare well with those responsible of the checkerboard pattern found in the density of states by Scanning Tunneling Microscopy. This similarity suggests that the checkerboard pattern originates from peaks in the joint density of states, as the dispersive peaks found in the superconducting state do. Here we show that the experimental AC-ARPES spectrum can be reproduced within a model for the pseudogap with no charge-ordering or symmetry breaking. We predict that, because of the competition of superconductivity and pseudogap, in the superconducting state, the AC-ARPES data of underdoped cuprates will present both dispersive and non-dispersive peaks and they will be better observed in cuprates with low critical temperature. We finally argue that the AC-ARPES data is a complementary and convenient way to measure the arc length.Comment: 5 pages, 3 eps figure

Social capital and sports clubs

Book synopsis: This volume provides a collection of critical new perspectives on social capital theory by examining how social values, power relationships, and social identity interact with social capital. This book seeks to extend this theory into what have been largely under-investigated domains, and, at the same time, address long-standing, classic questions in the literature concerning the forms, determinants, and consequences of social capital. Social capital can be understood in terms of social norms and networks. It manifests itself in patterns of trust, reciprocity, and cooperation. The authors argue that the degree to which and the different ways in which people exhibit these distinctively social behaviours depend on how norms and networks elicit their values, reflect power relationships, and draw on their social identities. This volume accordingly adopts a variety of different concepts and measures that incorporate the variety of contextually-specific factors that operate on social capital formation. In addition, it adopts an interdisciplinary outlook that combines a wide range of social science disciplines and methods of social research. Our objective is to challenge standard rationality theory explanations of norms and networks which overlook the role of values, power, and identity. This volume appeals to researchers and students in multiple social sciences, including economics, sociology, political science, social psychology, history, public policy, and international relations, that employ social capital concepts and methods in their research. It can be seen as a set of new extensions of social capital theory in connection with its themes of social values, power, and identity that would advance the scholarly literature on social norms and networks and their impact on social change and public welfare

Chemical modification and pharmacological evaluation of the antimalarial natural product totarol

Includes bibliographical references

Evolution of the gaps through the cuprate phase-diagram

The actual physical origin of the gap at the antinodes, and a clear identification of the superconducting gap are fundamental open issues in the physics of high-$T_c$ superconductors. Here, we present a systematic electronic Raman scattering study of a mercury-based single layer cuprate, as a function of both doping level and temperature. On the deeply overdoped side, we show that the antinodal gap is a true superconducting gap. In contrast, on the underdoped side, our results reveal the existence of a break point close to optimal doping below which the antinodal gap is gradually disconnected from superconductivity. The nature of both the superconducting and normal state is distinctly different on each side of this breakpoint

Social capital and social ties in organisations: a case study of two voluntary sports clubs

Purpose – If social capital is understood as the ability to access resources through social ties, it is clearly important to understand how people form social ties and what types of ties they form. Research has sought to do this, but it has seldom directly examined how organisations shape these processes and outcomes. This paper aims to do so. Design/methodology/approach – In-depth, comparative case study research was conducted at two voluntary sport organisations in the UK, involving 23 in-depth interviews and participant observation over a 15-month period. Findings – The case studies showed how key organisational practices structured, in meaningful ways, people’s opportunities for interaction and the nature of that interaction, shaping the ways in which they formed ties and exchanged resources. The organisations fostered the formation of both strong and weak ties, but also ‘compartmentally intimate’ ties. Research limitations/implications – The research challenges individualistic, rational-choice accounts of tie formation, highlighting the role of organisations as brokers. In addition, interviewees’ accounts challenge well-accepted distinctions between strong and weak ties, by demonstrating the importance of ongoing, context-specific interaction. Originality/value – This research offers a rare, direct insight into the role of organisations in shaping people’s ongoing social relationships. In doing so, it problematises existing conceptualisations of social capital and social ties and highlights an alternative, organisationally-embedded, process-based perspective on social capital