A characterization of the central shell-focusing singularity in spherical gravitational collapse

We give a characterization of the central shell-focusing curvature singularity that can form in the spherical gravitational collapse of a bounded matter distribution obeying the dominant energy condition. This characterization is based on the limiting behaviour of the mass function in the neighbourhood of the singularity. Depending on the rate of growth of the mass as a function of the area radius R, the singularity may be either covered or naked. The singularity is naked if this growth rate is slower than R, covered if it is faster than R, and either naked or covered if the growth rate is same as R.Comment: 12 pages, Latex, significantly revised version, including change of title. Revised version to appear in Classical and Quantum Gravit

How to serve our ethnic minority communities better

On Jan 9, 2017, Theresa May, the British Prime Minister, gave a speech about “the burning injustice of mental illness”, mentioning “injustices in the way black people with mental ill health in particular are treated”, and promising that politicians would “take action to put things right.” In response to three decades of UK research on ethnic differences in mental health, such emotionally charged rhetoric has been commonplace, but has rarely produced meaningful change. Mental health care in ethnic minorities is complex, and needs dispassionate and objective scrutiny of evidence and its limitations, with careful disentanglement of the interactions between ethnicity, culture, community histories, legacies of racism, and the labyrinthine service structures that people with mental illness and their families must navigate to get appropriate help. In The Lancet Psychiatry, Phoebe Barnett and colleagues present findings from a systematic review and meta-analysis of ethnicity and legal detention of people with mental illness, an impressive attempt at providing just such scrutiny. Although the findings are not strikingly different from what is known, this comprehensive paper is a timely reminder of how far we are from fully understanding the problem—let alone solving it—and why the stated political intention to put things right might be easy to promise but hard to deliver

Black and minority ethnic people are more likely to be detained under the Mental Health Act 1983 : no clear evidence why

Question: Compared with White people, how frequently are people from Black and Minority Ethnic groups detained under the Mental Health Act 1983? Outcomes: Rates of compulsory detention under the Mental Health Act. METHODS Design: Systematic review with meta-analysis. Data sources: MEDLINE, EMBASE, CINAHL, PsycINFO, ASSIA, SIGLE, HMIC, Web of Science, Cochrane database and the National Research Register; 1984 to April 2005. CD-ROM for the British National Bibliography was also searched for relevant literature. Study selection and analysis: English language studies relating to compulsory detention under the Mental Health Act 1983 and including terms related to mental illness or forensic psychiatry, and with inclusion of 2 ethnic groups (any non-White). Odds of compulsory detention of people from Black and Minority Ethnic (BME) groups compared with White groups were combined using a fixed effects meta-analysis. Meta-regression was then used to explore reasons for heterogeneity between studies. It was based on subgroup analyses according to episode (first, second, etc), patient type (for example, civil or forensic), study quality, and year of publication. The authors then narratively discuss the possible theories for the difference in detention rates

Singlet axial-vector coupling constant of the nucleon in QCD without instantons

We have analyzed axial-vector current-current correlation functions between one-nucleon states to calculate the singlet axial-vector coupling constant of the nucleon. The octet-octet and the octet-singlet current correlators, investigated in this work, do not require any use of instanton effects. The QCD and hadronic parameters used for the evaluation of correlators have been varied by (10 - 20)%. The value of the singlet axial-vector coupling constant of the nucleon obtained from this analysis is consistent with its current determination from experiments and QCD theory.Comment: A slightly modified version to be published in Physics Letters B; 14 pages with 6 figures and 1 tabl