12,075 research outputs found
Book review: Sexuality and social justice in Africa: rethinking homophobia and forging resistance
"Sexuality and Social Justice in Africa: Rethinking Homophobia and Forging Resistance." Marc Epprecht. Zed Books. July 2013. --- The persecution of people in Africa on the basis of their homosexual orientation has recently received considerable coverage in the media. However, much of the analysis thus far has been highly critical of African leadership and culture without considering local nuances, historical factors and external influences that are contributing to the problem. In this book, based on pioneering research on the history of homosexualities and engagement with current LGBTI activism, Marc Epprecht aims to provide a sympathetic overview of the issues at play. Clearly written and richly annotated, the book will prove to be a useful guide for academics, social workers, and activists, writes Jia Hui Lee
Macroscopic quantum coherence in antiferromagnetic molecular magnets
The macroscopic quantum coherence in a biaxial antiferromagnetic molecular
magnet in the presence of magnetic field acting parallel to its hard anisotropy
axis is studied within the two-sublattice model. On the basis of instanton
technique in the spin-coherent-state path-integral representation, both the
rigorous Wentzel-Kramers-Brillouin exponent and preexponential factor for the
ground-state tunnel splitting are obtained. We find that the quantum
fluctuations around the classical paths can not only induce a new quantum phase
previously reported by Chiolero and Loss (Phys. Rev. Lett. 80, 169 (1998)), but
also have great influnence on the intensity of the ground-state tunnel
splitting. Those features clearly have no analogue in the ferromagnetic
molecular magnets. We suggest that they may be the universal behaviors in all
antiferromagnetic molecular magnets. The analytical results are complemented by
exact diagonalization calculation.Comment: 6 pages, 1 figur
Superradiantly stable non-extremal Reissner-Nordstrom black holes
The superradiant stability is investigated for non-extremal
Reissner-Nordstrom black hole. We use an algebraic method to demonstrate that
all non-extremal Reissner-Nordstrom black holes are superradiantly stable
against a charged massive scalar perturbation. This improves the results
obtained before for non-extremal Reissner-Nordstrom black holes
Effects of arbitrarily directed field on spin phase oscillations in biaxial molecular magnets
Quantum phase interference and spin-parity effects are studied in biaxial
molecular magnets in a magnetic field at an arbitrarily directed angle. The
calculations of the ground-state tunnel splitting are performed on the basis of
the instanton technique in the spin-coherent-state path-integral
representation, and complemented by exactly numerical diagonalization. Both the
Wentzel-Kramers-Brillouin exponent and the preexponential factor are obtained
for the entire region of the direction of the field. Our results show that the
tunnel splitting oscillates with the field for the small field angle, while for
the large field angle the oscillation is completely suppressed. This distinct
angular dependence, together with the dependence of the tunnel splitting on the
field strengh, provide an independent test for spin-parity effects in biaxial
molecular magnets. The analytical results for the molecular Fe magnet,
are found to be in good areement with the numerical simulations, which suggests
that even the molecular magnet with total spin S=10 is large enough to be
treated as a giant spin system.Comment: 19 pages, 5 figure
Low energy exciton states in a nanoscopic semiconducting ring
We consider an effective mass model for an electron-hole pair in a simplified
confinement potential, which is applicable to both a nanoscopic self-assembled
semiconducting InAs ring and a quantum dot. The linear optical susceptibility,
proportional to the absorption intensity of near-infrared transmission, is
calculated as a function of the ring radius . Compared with the
properties of the quantum dot corresponding to the model with a very small
radius , our results are in qualitative agreement with the recent
experimental measurements by Pettersson {\it et al}.Comment: 4 pages, 4 figures, revised and accepted by Phys. Rev.
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