Exotic orbits due to spin-spin coupling around Kerr black holes

We report exotic orbital phenomena of spinning test particles orbiting around a Kerr black hole, i.e., some orbits of spinning particles are asymmetrical about the equatorial plane. When a nonspinning test particle orbits around a Kerr black hole in a strong field region, due to relativistic orbital precessions, the pattern of trajectories is symmetrical about the equatorial plane of the Kerr black hole. However, the patterns of the spinning particles' orbit are no longer symmetrical about the equatorial plane for some orbital configurations and large spins. We argue that these asymmetrical patterns come from the spin-spin interactions between spinning particles and Kerr black holes, because the directions of spin-spin forces can be arbitrary, and distribute asymmetrically about the equatorial plane.Comment: 15 pages, 20 figure

Improving sustainability performance through supplier relationship management in the tobacco industry

Purpose: The purpose of this study is to explore how tobacco manufacturing companies can improve their sustainability performance via effective supplier relationship management (SRM). Design/methodology/approach: This study has adopted a single case study of an international tobacco company. The primary data involved semi-structured interviews with participants from the case company who are familiar with sustainable SRM in the tobacco industry and are engaging in various techniques to improve sustainability performance. Findings: The drivers for sustainable SRM commonly identified in literature are observable within the case company. There is also clear evidence of integrating sustainability in its SRM processes. However, the perception of sustainability as a requirement to meet stringent regulations limits its scope and drive in pursuing sustainable SRM. It has also limited supplier sustainability evaluation and performance metrics. Furthermore, the findings of this paper reinforce the importance of a procurement team’s ability to work with other functional teams in implementing sustainable SRM. The findings also contribute to the emerging literature on the impact of sustainability on supplier segmentation and multi-tier supplier management. Research limitations/implications: This study provides insight into the varying SRM methods used in the tobacco industry to ensure compliance and improve sustainability performance. However, further research is required to explore the generalisability of the findings of this study derived from a single case study. Originality/value: The tobacco industry is an under-researched industry, particularly in terms of sustainable operations and supply chain management practices. The findings of this study seem to be relevant to those comparable industries with stringent regulations as well

Essays in Climate Change and Finance

My first paper studies how firms' environmental performances affect cross-sectional expected stock returns and investments. Using a third-party ESG score, I find that greener stocks have lower expected returns. This greenium remains significant after controlling for systematic and idiosyncratic risks. Green stocks hedge climate-related disasters, contributing to the greenium. A macro-finance integrated assessment model featuring time-varying climate damage intensity, recursive preferences, and investment frictions quantitatively explains the empirical findings. The model implies a positive covariance between climate damages and consumption, which justifies a high discount rate and a low present value of carbon emission. The second paper is a joint work with Shasha Li, a former colleague at Bocconi University who is now an assistant professor at the Halle Institute for Economic Research. We study how the attention allocation of green-motivated investors changes information asymmetry in financial markets and thus affects firms' financing costs. To guide our empirical analysis, we propose a model where an investor with green taste endogenously allocates attention to market or firm-specific shocks. We find that more green-motivated investors tend to give more attention to green firm-level information instead of market-level information. Thus higher green taste leads to less category learning behavior and reduces the information asymmetry. Furthermore, it suggests that higher green taste results in lower leverage and lower cost of capital of green firms. The last paper is a proposal that applies the information theory on climate change. I study how a better information about climate evolution and feedback in the future affects current actions to mitigate carbon emissions. This proposal improves previous studies on the precautionary principal, by extending the traditional method to rank information structures by Blackwell (1966) to a less strict but more versatile method by Lehmann (1988). This study could help policymaker better decide the timing of climate mitigation when facing decreased future uncertainty