Stability of spin-0 graviton and strong coupling in Horava-Lifshitz theory of gravity

In this paper, we consider two different issues, stability and strong coupling, raised lately in the newly-proposed Horava-Lifshitz (HL) theory of quantum gravity with projectability condition. We find that all the scalar modes are stable in the de Sitter background, due to two different kinds of effects, one from high-order derivatives of the spacetime curvature, and the other from the exponential expansion of the de Sitter space. Combining these effects properly, one can make the instability found in the Minkowski background never appear even for small-scale modes, provided that the IR limit is sufficiently closed to the relativistic fixed point. At the fixed point, all the modes become stabilized. We also show that the instability of Minkowski spacetime can be cured by introducing mass to the spin-0 graviton. The strong coupling problem is investigated following the effective field theory approach, and found that it cannot be cured by the Blas-Pujolas-Sibiryakov mechanism, initially designed for the case without projectability condition, but might be circumvented by the Vainshtein mechanism, due to the non-linear effects. In fact, we construct a class of exact solutions, and show explicitly that it reduces smoothly to the de Sitter spacetime in the relativistic limit.Comment: Some points regarding to strong coupling are further clarified, and typos corrected. revtex4, 9 figures. Version to appear in Physical Reviews

Boltzmann Equations for Spin and Charge Relaxations in Superconductors

In a superconductor coupled with a ferromagnetic metal, spin and charge imbalances can be induced by injecting spin-polarized electron current from the ferromagnetic metal. We theoretically study a nonequilibrium distribution of quasiparticles in the presence of spin and charge imbalances. We show that four distribution functions are needed to characterize such a nonequilibrium situation, and derive a set of linearized Boltzmann equations for them by extending the argument by Schmid and Sch\"{o}n based on the quasiclassical Green's function method. Using the Boltzmann equations, we analyze the spin imbalance in a thin superconducting wire weakly coupled with a ferromagnetic electrode. The spin imbalance induces a shift $\delta\mu$ ($- \delta \mu$) of the chemical potential for up-spin (down-spin) quasiparticles. We discuss how $\delta \mu$ is relaxed by spin-orbit impurity scattering.Comment: 16 pages, 2 figure

‘Teachers’ to ‘academics’: the implementation of a modernisation project at one UK post-92 university

Among the many external forces that have impacted upon institutions, league tables have been the dynamic to which universities across the world are now responding. Following the appointment of a new vice-chancellor at one post-92 UK university, a modernisation project was introduced aimed at maximising the institutions’ research standing. For the institutional actors, the university’s lecturers, this modernisation project demanded a change in their working practices from one which had focused on teaching related activities to a situation where an emphasis was to be placed upon research. This study examines how university teachers at this institution understood and responded to the modernisation project to acquire research skills and provides an insight into a path-breaking strategic plan that was enacted within an historically dependent setting. It muses on the dialectics of institutional path dependency and the path breaking effect of a modernisation project that was stimulated by new managerialism

Colliding branes and formation of spacetime singularities in string theory

Colliding branes without $Z_{2}$ symmetry and the formation of spacetime singularities in string theory are studied. After developing the general formulas to describe such events, we study a particular class of exact solutions first in the 5-dimensional effective theory, and then lift it to the 10-dimensional spacetime. In general, the 5-dimensional spacetime is singular, due to the mutual focus of the two colliding 3-branes. Non-singular cases also exist, but with the price that both of the colliding branes violate all the three energy conditions, weak, dominant, and strong. After lifted to 10 dimensions, we find that the spacetime remains singular, whenever it is singular in the 5-dimensional effective theory. In the cases where no singularities are formed after the collision, we find that the two 8-branes necessarily violate all the energy conditions.Comment: revtex4, 13 figures. Some typos were corrected, and new refereeces added. Final version to appear in JHE

Historia de un campamento del Horizonte Medio de Huarmey, Perú (PV35-4)

Se presenta el estudio de un campamento temporal del Horizonte Medio situado en el desierto costero peruano al norte del valle de Huarmey. Se ha excavado la parte central del mismo pues presentaba la mayor cantidad de basura y dos fogones. Se ha podido establecer a base de la cerámica encontrada, que el sitio corresponde al Horizonte Medio 3. Los artefactos hallados son muy pocos, lo que es lógico dada la corta ocupación del sitio. Sin embargo se ha podido estudiar los abundantes restos botánicos y animales así como los fecales de llama que estaban acumulados en el lugar. También se ha encontrado coprolitos humanos. De ambos se ha realizado el examen polínico. Además de los excrementos humanos se ha efectuado el análisis del contenido de plantas y animales así como el parasitológico.Cet article étudie un campement temporaire de l’Horizon Moyen situé dans le désert côtier péruvien au nord de la vallée de Huarmey. La partie centrale du site a été choisie pour les fouilles car elle offrait la plus grande quantité de déchets ainsi que deux foyers. Il a été établi que le site correspondait à l’Horizon Moyen 3 grâce à la céramique qui y fut trouvée. Peu d’outillage a été trouvé en raison de la courte occupation du site, mais les restes abondants d’animaux et botaniques ainsi que les restes fécaux de llamas et humains accumulés sur le site ont fourni de précieuses indications. Les résultats des examens polliniques des coprolithes ainsi que les analyses du contenu de plantes, animaux et parasytes présents dans les coprolithes humains sont présentés ici.This is a study of a Middle Horizon temporary campsite located in the peruvian north coastal desert of the Huarmey Valley. The excavation was undertaken in the central part of the site since it contained the largest quantity debris and evidence of two bonfires. Its age was established using pieces of ceramic found on the site. A few artifacts were founded, probably due to the brief occupancy of the site, but were able to study the abundant botanical and animal remains, as well as llama and human coprolites. We present the results of tests for pollen in both the llama and human coprolites, as well as of tests for plant, animal, and parasite content in the human fecal remains are presented here

Age, anticoagulants, hypertension and cardiovascular genetic traits predict cranial ischaemic complications in patients with giant cell arteritis

\ua9 Author(s) (or their employer(s)) 2024. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ on behalf of EULAR.Objectives: This project aimed to determine whether cranial ischaemic complications at the presentation of giant cell arteritis (GCA) were associated with pre-existing cardiovascular (CV) risk factors, CV disease or genetic risk of CV-related traits. Methods: 1946 GCA patients with clinicodemographic data at GCA presentation were included. Associations between pre-existing CV-related traits (including Polygenic Risk Scores (PRS) for CV traits) and cranial ischaemic complications were tested. A model for cranial ischaemic complications was optimised using an elastic net approach. Positional gene mapping of associated PRS was performed to improve biological understanding. Results: In a sample of 1946 GCA patients (median age=71, 68.7% female), 17% had cranial ischaemic complications at presentation. In univariable analyses, 10 variables were associated with complications (likelihood-ratio test p≤0.05). In multivariable analysis, the two variables with the strongest effects, with or without PRS in the model, were anticoagulant therapy (adjusted OR (95% CI)=0.21 (0.05 to 0.62), p=4.95 710-3) and age (adjusted OR (95% CI)=1.60 (0.73 to 3.66), p=2.52 710-3, for ≥80 years versus <60 years). In sensitivity analyses omitting anticoagulant therapy from multivariable analysis, age and hypertension were associated with cranial ischaemic complications at presentation (hypertension: adjusted OR (95% CI)=1.35 (1.03 to 1.75), p=0.03). Positional gene mapping of an associated transient ischaemic attack PRS identified TEK, CD96 and MROH9 loci. Conclusion: Age and hypertension were risk factors for cranial ischaemic complications at GCA presentation, but in this dataset, anticoagulation appeared protective. Positional gene mapping suggested a role for immune and coagulation-related pathways in the pathogenesis of complications. Further studies are needed before implementation in clinical practice