Short-coherence length superconductivity in the Attractive Hubbard Model in three dimensions

We study the normal state and the superconducting transition in the Attractive Hubbard Model in three dimensions, using self-consistent diagrammatics. Our results for the self-consistent $T$-matrix approximation are consistent with 3D-XY power-law critical scaling and finite-size scaling. This is in contrast to the exponential 2D-XY scaling the method was able to capture in our previous 2D calculation. We find the 3D transition temperature at quarter-filling and $U=-4t$ to be $T_c=0.207t$. The 3D critical regime is much narrower than in 2D and the ratio of the mean-field transition to $T_c$ is about 5 times smaller than in 2D. We also find that, for the parameters we consider, the pseudogap regime in 3D (as in 2D) coincides with the critical scaling regime.Comment: 4 pages, 5 figure

Transport anomalies in a simplified model for a heavy electron quantum critical point

We discuss the transport anomalies associated with the development of heavy electrons out of a neutral spin fluid using the large-N treatment of the Kondo-Heisenberg lattice model. At the phase transition in this model the spin excitations suddenly acquire charge. The Higgs process by which this takes place causes the constraint gauge field to loosely ``lock'' together with the external, electromagnetic gauge field. From this perspective, the heavy fermion phase is a Meissner phase in which the field representing the difference between the electromagnetic and constraint gauge field, is excluded from the material. We show that at the transition into the heavy fermion phase, both the linear and the Hall conductivity jump together. However, the Drude weight of the heavy electron fluid does not jump at the quantum critical point, but instead grows linearly with the distance from the quantum critical point, forming a kind of ``gossamer'' Fermi-liquid.Comment: 15 pages, 3 figures. Small change in references in v

Investigations into the Sarcomeric Protein and Ca2+-Regulation Abnormalities Underlying Hypertrophic Cardiomyopathy in Cats (Felix catus).

Hypertrophic cardiomyopathy (HCM) is the most common single gene inherited cardiomyopathy. In cats (Felix catus) HCM is even more prevalent and affects 16% of the outbred population and up to 26% in pedigree breeds such as Maine Coon and Ragdoll. Homozygous MYBPC3 mutations have been identified in these breeds but the mutations in other cats are unknown. At the clinical and physiological level feline HCM is closely analogous to human HCM but little is known about the primary causative mechanism. Most identified HCM causing mutations are in the genes coding for proteins of the sarcomere. We therefore investigated contractile and regulatory proteins in left ventricular tissue from 25 cats, 18 diagnosed with HCM, including a Ragdoll cat with a homozygous MYBPC3 R820W, and 7 non-HCM cats in comparison with human HCM (from septal myectomy) and donor heart tissue. Myofibrillar protein expression was normal except that we observed 20–44% MyBP-C haploinsufficiency in 5 of the HCM cats. Troponin extracted from 8 HCM and 5 non-HCM cat hearts was incorporated into thin filaments and studied by in vitro motility assay. All HCM cat hearts had a higher (2.06 ± 0.13 fold) Ca2+-sensitivity than non-HCM cats and, in all the HCM cats, Ca2+-sensitivity was not modulated by troponin I phosphorylation. We were able to restore modulation of Ca2+-sensitivity by replacing troponin T with wild-type protein or by adding 100 μM Epigallocatechin 3-gallate (EGCG). These fundamental regulatory characteristics closely mimic those seen in human HCM indicating a common molecular mechanism that is independent of the causative mutation. Thus, the HCM cat is a potentially useful large animal model

Staggered Flux Phase in a Model of Strongly Correlated Electrons

We present numerical evidence for the existence of a staggered flux (SF) phase in the half-filled two-leg t-U-V-J ladder, with true long-range order in the counter-circulating currents. The density-matrix renormalization-group (DMRG) / finite-size scaling approach, generalized to describe complex-valued Hamiltonians and wavefunctions, is employed. The SF phase exhibits robust currents at intermediate values of the interaction strength.Comment: Version to appear in Phys. Rev. Let

Trajectories of loneliness and objective social isolation and associations between persistent loneliness and self-reported personal recovery in a cohort of secondary mental health service users in the UK

Background: Loneliness is a frequent and distressing experience among people with mental health problems. However, few longitudinal studies have so far investigated the trajectories of loneliness and objective social isolation, and the extent to which both issues may impact mental health outcomes among mental health service users. Therefore, this study aims to describe the trajectories of loneliness and objective social isolation and their associations with self-rated personal recovery among people leaving crisis resolution teams (CRTs). Methods: A total of 224 participants receiving care from CRTs (recruited for a large multi-site randomised controlled trial) were included in this longitudinal cohort study. They completed the eight-item University of California at Los Angeles Loneliness Scale (ULS-8), Lubben-Social Network Scale (LNSN-6), and the Questionnaire about the Process of Recovery (QPR) (primary outcome) at baseline, 4- and 18-month follow-up, as well as baseline sociodemographic and clinical variables. Results: We compared groups who were persistently lonely (at all time points), intermittently lonely (at one or two time points) and never lonely. After adjusting for all potential confounders and baseline predictive variables, persistent severe loneliness was associated with worse personal recovery at 18-month follow-up compared with the never lonely (reference group) (coef. = − 12.8, 95% CI -11.8, − 3.8, p < .001), as was being intermittently lonely (coef. = − 7.8, 95% CI -18.8, − 6.8, p < .001). The persistently objectively social isolated group (coef. = − 9.8, 95% CI -15.7, − 3.8, p = .001) also had poorer self-rated recovery at 18-month follow-up than those who were not socially isolated at any timepoint (i.e., reference category). Conclusion: Results suggest that both persistent loneliness and objective social isolation are associated with poorer self-rated recovery following a crisis, compatible with a causal relationship. These findings suggest a potential role for interventions aimed at alleviating loneliness and objective social isolation in improving recovery outcomes for people with mental health symptoms. Increased awareness of both issues among health practitioners is also warranted

Direct Statistical Simulation of Jets and Vortices in 2D Flows

In this paper we perform Direct Statistical Simulations of a model of two-dimensional flow that exhibits a transition from jets to vortices. The model employs two-scale Kolmogorov forcing, with energy injected directly into the zonal mean of the flow. We compare these results with those from Direct Numerical Simulations. For square domains the solution takes the form of jets, but as the aspect ratio is increased a transition to isolated coherent vortices is found. We find that a truncation at second order in the equal-time but nonlocal cumulants that employs zonal averaging (zonal CE2) is capable of capturing the form of the jets for a range of Reynolds numbers as well as the transition to the vortex state, but, unsurprisingly, is unable to reproduce the correlations found for the fully nonlinear (non-zonally symmetric) vortex state. This result continues the program of promising advances in statistical theories of turbulence championed by Kraichnan