Cooperon propagator description of high temperature superconductivity

A phenomenological description of the high-Tc superconductors based on the Cooperon propagator is presented. This model allows one to study the effects of local pairing correlations and long-range phase fluctuations on the same footing, both above and below Tc. Based on numerical calculations, it is shown that the two types of correlations contribute to the gap/pseudogap in the single-particle excitation spectra. The concourse of these two effects can induce low energy states, which should be observable in underdoped materials at very low temperature.Comment: LaTeX, 6 pages, 2 EPS figures; paper presented at New^3SC-3, Hawaii, 01/2001. To appear in Physica

Low-Frequency Optical Conductivity in Inhomogeneous d-wave Superconductors

Motivated by the recent optical conductivity experiments on Bi_2Sr_2CaCu_2O_{8+delta} films, we examine the possible origin of low-frequency dissipation in the superconducting state. In the presence of spatial inhomogeneity of the local phase stiffness rho_s, it is shown that some spectral weight is removed from omega=0 to finite frequencies and contribute to dissipation. A case where both rho_s and the local normal fluid density are inhomogeneous is also considered. We find an enhanced dissipation at low frequency if the two variations are anti-correlated.Comment: To appear in Phys. Rev.

The mass of the graviton and the cosmological constant

We show that the graviton acquires a mass in a de Sitter background given by $m_{g}^{2}=-{2/3}\Lambda.$ This is precisely the fine-tuning value required for the perturbed gravitational field to mantain its two degrees of freedom.Comment: Title changed and few details added, without any changes in the conclusio

Models for Enhanced Absorption in Inhomogeneous Superconductors

We discuss the low-frequency absorption arising from quenched inhomogeneity in the superfluid density rho_s of a model superconductor. Such inhomogeneities may arise in a high-T_c superconductor from a wide variety of sources, including quenched random disorder and static charge density waves such as stripes. Using standard classical methods for treating randomly inhomogeneous media, we show that both mechanisms produce additional absorption at finite frequencies. For a two-fluid model with weak mean-square fluctuations <(d rho_s)^2 > in rho_s and a frequency-independent quasiparticle conductivity, the extra absorption has oscillator strength proportional to the quantity <(d rho_s)^2>/rho_s, as observed in some experiments. Similar behavior is found in a two-fluid model with anticorrelated fluctuations in the superfluid and normal fluid densities. The extra absorption typically occurs as a Lorentzian centered at zero frequency. We present simple model calculations for this extra absorption under conditions of both weak and strong fluctuations. The relation between our results and other model calculations is briefly discussed

Assessing the Impact of Anger State on the Three Attentional Networks With the ANT-I

Anger is a negative and highly aroused emotion. Previous research has revealed that a high level of arousal can induce the participant in a physical preparation and self-awareness. The aim of this research was to study the influence of anger on the attentional network using the Attention Network Test-Interactions (ANT-I). This test has been developed in order to assess 3 attentional networks: alerting, orienting, and executive control. Here, participants were induced in anger using the autobiographic recall procedure or in a neutral mood before the realization of the ANT-I. As expected, the results showed a better alerting score for the angry group. The possible origin of this alerting gain related to the high level of arousal is discussed. The results obtained should enlighten the interaction between emotion and the functioning of the attentional system. They also may be relevant for applied fields related to anger. (PsycINFO Database Record (c) 2014 APA, all rights reserved)

Intact Semantic Priming of Critical Lures in Alzheimer&#039;s Disease: Implications for False Memory

OBJECTIVES: The present study examines the question of the activation of the critical lure (CL) in Alzheimer\u27s patients with a Deese-Roediger-McDermott (DRM)-like task. More precisely, older adults and Alzheimer\u27s patients performed a lexical decision task in which they were asked to categorize strings of letters as words or nonwords. Contrary to the DRM paradigm in which the activation of the CL is inferred from its production at recall, such a lexical decision task does not require the joint use of intentional recovery strategies and source-monitoring processes that are known to be particularly impaired in Alzheimer\u27s patients. The performance at the lexical decision therefore reflects the activation of the CL without contamination from such strategic processes. METHOD: Twenty-nine older adults and 25 Alzheimer\u27s patients performed a lexical decision task with DRM lists intermixed with neutral words and nonwords. RESULTS: Analysis indicated that older adults as well as Alzheimer\u27s patients showed shorter lexical decision latencies for CLs than for other types of words. DISCUSSION: Contrary to the existing literature, our results suggest that the activation of the CL is preserved in Alzheimer\u27s patients at mild to moderate stages of the disease

Deformation of a nearly hemispherical conducting drop due to an electric field: theory and experiment

We consider, both theoretically and experimentally, the deformation due to an electric field of a pinned nearly-hemispherical static sessile drop of an ionic fluid with a high conductivity resting on the lower substrate of a parallel plate capacitor. Using both numerical and asymptotic approaches we find solutions to the coupled electrostatic and augmented Young–Laplace equations which agree very well with the experimental results. Our asymptotic solution for the drop interface extends previous work in two ways, namely to drops that have zero-field contact angles that are not exactly π/2 and to higher order in the applied electric field, and provides useful predictive equations for the changes in the height, contact angle and pressure as functions of the zero-field contact angle, drop radius, surface tension and applied electric field. The asymptotic solution requires some numerical computations, and so a surprisingly accurate approximate analytical asymptotic solution is also obtained