Internal Gravity Waves Modulate the Apparent Misalignment of Exoplanets around Hot Stars

We propose that the observed misalignment between extra-solar planets and their hot host stars can be explained by angular momentum transport within the host star. Observations have shown that this misalignment is preferentially around hot stars, which have convective cores and extended radiative envelopes. This situation is amenable to substantial angular momentum transport by internal gravity waves (IGW) generated at the convective-radiative interface. Here we present numerical simulations of this process and show that IGW can modulate the surface rotation of the star. With these two- dimensional simulations we show that IGW could explain the retrograde orbits observed in systems such as HAT-P-6 and HAT-P-7, however, extension to high obliquity objects will await future three- dimensional simulations. We note that these results also imply that individual massive stars should show temporal variations in their v sini measurements.Comment: 6 pages, 2 figures, Accepted for publication in ApJ

Carbon Rich Extremely Metal Poor Stars: Signatures of Population-III AGB stars in Binary Systems

We use the Cambridge stellar evolution code STARS to model the evolution and nucleosynthesis of zero-metallicity intermediate-mass stars. We investigate the effect of duplicity on the nucleosynthesis output of these systems and the potential abundances of the secondaries. The surfaces of zero-metallicity stars are enriched in CNO elements after second dredge up. During binary interaction, such as Roche lobe overflow or wind accretion, metals can be released from these stars and the secondaries enriched in CNO isotopes. We investigate the formation of the two most metal poor stars known, HE 0107-5240 and HE 1327-2326. The observed carbon and nitrogen abundances of HE 0107-5240 can be reproduced by accretion of material from the companion-enhanced wind of a seven solar star after second dredge-up, though oxygen and sodium are underproduced. We speculate that HE 1327-2326, which is richer in nitrogen and strontium, may similarly be formed by wind accretion in a later AGB phase after third dredge-up.Comment: 16 pages, 1 figure, 7 tables, accepted by MNRA

Fronthaul-Constrained Cloud Radio Access Networks: Insights and Challenges

As a promising paradigm for fifth generation (5G) wireless communication systems, cloud radio access networks (C-RANs) have been shown to reduce both capital and operating expenditures, as well as to provide high spectral efficiency (SE) and energy efficiency (EE). The fronthaul in such networks, defined as the transmission link between a baseband unit (BBU) and a remote radio head (RRH), requires high capacity, but is often constrained. This article comprehensively surveys recent advances in fronthaul-constrained C-RANs, including system architectures and key techniques. In particular, key techniques for alleviating the impact of constrained fronthaul on SE/EE and quality of service for users, including compression and quantization, large-scale coordinated processing and clustering, and resource allocation optimization, are discussed. Open issues in terms of software-defined networking, network function virtualization, and partial centralization are also identified.Comment: 5 Figures, accepted by IEEE Wireless Communications. arXiv admin note: text overlap with arXiv:1407.3855 by other author

Research Shows a Majority of People in Hong Kong Support Gay and Lesbian Couples’ Rights, Not Necessarily Marriage

Briefing Paper, Centre for Comparative and Public Law (University of Hong Kong); UNC Legal Studies Research Paper No. 2374875Discussions in Hong Kong about same-sex couples’ rights often focus on the issue of same-sex marriage. However, marriage is not the only way the government could extend rights to same-sex couples. In other parts of the world, governments have conferred rights upon gay and lesbian couples without legalising same-sex marriage. Some governments have developed programs that grant same-sex couples a subset of the rights that married heterosexual couples enjoy, for example the right to hospital visitation, the right to inheritance, and the right to sue in cases of fatal accidents. Other governments have developed programs that give same-sex couples access to all the rights that married heterosexual couples have, without using the word “marriage”. These compromise legal solutions have been given a variety of different names, such as “registered domestic partnerships”, “civil unions”, and “civil partnerships.”1 We conducted a public opinion survey to investigate Hong Kong people’s attitudes towards granting same-sex couples a variety of rights, including but not limited to the right to marry. We found that only 27% of the public completely agreed that same-sex couples should be permitted to marry, and 12% said that they somewhat agreed. However, when we asked about rights more generally, our findings were substantially different: 74% of the public supported granting samesex couples either all or some of the rights that are accorded to heterosexual couples. The remainder of this briefing paper proceeds in two steps. We first provide background on our survey and present our findings. Afterwards, we explore the public policy implications of our research.preprin