Kerr black hole quasinormal frequencies

Black-hole quasinormal modes (QNM) have been the subject of much recent attention, with the hope that these oscillation frequencies may shed some light on the elusive theory of quantum gravity. We compare numerical results for the QNM spectrum of the (rotating) Kerr black hole with an {\it exact} formula Re$\omega \to T_{BH}\ln 3+\Omega m$, which is based on Bohr's correspondence principle. We find a close agreement between the two. Possible implications of this result to the area spectrum of quantum black holes are discussed.Comment: 3 pages, 2 figure

A note on quasinormal modes: A tale of two treatments

There is an apparent discrepancy in the literature with regard to the quasinormal mode frequencies of Schwarzschild-de Sitter black holes in the degenerate-horizon limit. On the one hand, a Poschl-Teller-inspired method predicts that the real part of the frequencies will depend strongly on the orbital angular momentum of the perturbation field whereas, on the other hand, the degenerate limit of a monodromy-based calculation suggests there should be no such dependence (at least, for the highly damped modes). In the current paper, we provide a possible resolution by critically re-assessing the limiting procedure used in the monodromy analysis.Comment: 11 pages, Revtex format; (v2) new addendum in response to reader comments, also references, footnote and acknowledgments adde

Numerical analysis of quasinormal modes in nearly extremal Schwarzschild-de Sitter spacetimes

We calculate high-order quasinormal modes with large imaginary frequencies for electromagnetic and gravitational perturbations in nearly extremal Schwarzschild-de Sitter spacetimes. Our results show that for low-order quasinormal modes, the analytical approximation formula in the extremal limit derived by Cardoso and Lemos is a quite good approximation for the quasinormal frequencies as long as the model parameter $r_1\kappa_1$ is small enough, where $r_1$ and $\kappa_1$ are the black hole horizon radius and the surface gravity, respectively. For high-order quasinormal modes, to which corresponds quasinormal frequencies with large imaginary parts, on the other hand, this formula becomes inaccurate even for small values of $r_1\kappa_1$. We also find that the real parts of the quasinormal frequencies have oscillating behaviors in the limit of highly damped modes, which are similar to those observed in the case of a Reissner-Nordstr{\" o}m black hole. The amplitude of oscillating ${\rm Re(\omega)}$ as a function of ${\rm Im}(\omega)$ approaches a non-zero constant value for gravitational perturbations and zero for electromagnetic perturbations in the limit of highly damped modes, where $\omega$ denotes the quasinormal frequency. This means that for gravitational perturbations, the real part of quasinormal modes of the nearly extremal Schwarzschild-de Sitter spacetime appears not to approach any constant value in the limit of highly damped modes. On the other hand, for electromagnetic perturbations, the real part of frequency seems to go to zero in the limit.Comment: 9 pages, 7 figures, to appear in Physical Review

Analytic calculation of quasi-normal modes

We discuss the analytic calculation of quasi-normal modes of various types of perturbations of black holes both in asymptotically flat and anti-de Sitter spaces. We obtain asymptotic expressions and also show how corrections can be calculated perturbatively. We pay special attention to low-frequency modes in anti-de Sitter space because they govern the hydrodynamic properties of a gauge theory fluid according to the AdS/CFT correspondence. The latter may have experimental consequencies for the quark-gluon plasma formed in heavy ion collisions.Comment: 33 pages, prepared for the proceedings of the 4th Aegean Summer School on Black Holes, Mytilene, Greece, September 200

Connecting Numerical Relativity and Data Analysis of Gravitational Wave Detectors

Gravitational waves deliver information in exquisite detail about astrophysical phenomena, among them the collision of two black holes, a system completely invisible to the eyes of electromagnetic telescopes. Models that predict gravitational wave signals from likely sources are crucial for the success of this endeavor. Modeling binary black hole sources of gravitational radiation requires solving the Eintein equations of General Relativity using powerful computer hardware and sophisticated numerical algorithms. This proceeding presents where we are in understanding ground-based gravitational waves resulting from the merger of black holes and the implications of these sources for the advent of gravitational-wave astronomy.Comment: Appeared in the Proceedings of 2014 Sant Cugat Forum on Astrophysics. Astrophysics and Space Science Proceedings, ed. C.Sopuerta (Berlin: Springer-Verlag

Effect of summer grazing on welfare of dairy cows reared in mountain tie-stall barns

Traditional mountain farms have an important economic, social and environmental role. The Alps management system for dairy cows consists of animals kept indoors from autumn to spring, mostly in tie-stalls, and moved to mountain pasture in summer. The aim of our study was to assess the effect of mountain summer grazing on the welfare of dairy cows housed in tie-stall barns. Twenty-four farms were considered. In twelve of them, animals were reared in tie-stalls and moved to mountain pasture for three months in summer; they were visited three times: (i) four weeks before grazing during the indoor period in the stall; (ii) about three weeks after the start of grazing; and (iii) in the stall, in autumn, at least three weeks after returning from grazing. The other twelve farms kept the animals in tie-stalls all year; they were visited once in autumn. Data were collected following a protocol that considers animal-based measures and structure information on the basis of Quality Welfare Consortium® indications. Data allowed the calculation of both the Animal Needs Index score (ANI 35L) and an overall assessment of the cows' welfare obtained from three general aspects: housing, animal's physical condition, and animal's behaviour. Summer grazing had a significant positive effect on injuries, lameness and animal's rising duration but a negative effect on faeces consistency. Moreover, a reduction of tongue playing was observed. The ANI 35L and the overall assessment did not show significant differences linked to summer grazing, which tended to have a positive but temporary effect on animal behaviour

Functional neuroanatomy of speech signal decoding in primary progressive aphasias

This work was supported by the Alzheimer’s Society (AS-PG-16-007), the National Institute for Health Research University College London Hospitals Biomedical Research Centre (CBRC 161), the UCL Leonard Wolfson Experimental Neurology Centre (PR/ ylr/18575), and the Economic and Social Research Council (ES/ K006711/1). Individual authors were supported by the Medical Research Council (PhD Studentship to CJDH; MRC Clinician Scientist Fellowship to JDR), the Wolfson Foundation (Clinical Research Fellowship to CRM), the National Brain AppealeFrontotemporal Dementia Research Fund (CNC), Alzheimer’s Research UK (ARTSRF2010-3 to SJC), and the Wellcome Trust (091673/Z/10/Z to JDW)

Whole-genome sequencing reveals host factors underlying critical COVID-19

Critical COVID-19 is caused by immune-mediated inflammatory lung injury. Host genetic variation influences the development of illness requiring critical care1 or hospitalization2,3,4 after infection with SARS-CoV-2. The GenOMICC (Genetics of Mortality in Critical Care) study enables the comparison of genomes from individuals who are critically ill with those of population controls to find underlying disease mechanisms. Here we use whole-genome sequencing in 7,491 critically ill individuals compared with 48,400 controls to discover and replicate 23 independent variants that significantly predispose to critical COVID-19. We identify 16 new independent associations, including variants within genes that are involved in interferon signalling (IL10RB and PLSCR1), leucocyte differentiation (BCL11A) and blood-type antigen secretor status (FUT2). Using transcriptome-wide association and colocalization to infer the effect of gene expression on disease severity, we find evidence that implicates multiple genes—including reduced expression of a membrane flippase (ATP11A), and increased expression of a mucin (MUC1)—in critical disease. Mendelian randomization provides evidence in support of causal roles for myeloid cell adhesion molecules (SELE, ICAM5 and CD209) and the coagulation factor F8, all of which are potentially druggable targets. Our results are broadly consistent with a multi-component model of COVID-19 pathophysiology, in which at least two distinct mechanisms can predispose to life-threatening disease: failure to control viral replication; or an enhanced tendency towards pulmonary inflammation and intravascular coagulation. We show that comparison between cases of critical illness and population controls is highly efficient for the detection of therapeutically relevant mechanisms of disease

Towards an acceptable past? Variable reflections of the Italian Resistance 1945-1995

Available from British Library Document Supply Centre-DSC:DXN044099 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Herbage intake handbook

SIGLELD:83/O1293(Herbage) / BLDSC - British Library Document Supply CentreGBUnited Kingdo