No-go for tree-level R-symmetry breaking

We show that in gauge mediation models with tree-level R-symmetry breaking where supersymmetry and R-symmetries are broken by different fields, the gaugino mass either vanishes at one loop or finds a contribution from loop-level R-symmetry breaking. Thus tree-level R-symmetry breaking for phenomenology is either no-go or redundant in the simplest type of models. Including explicit messenger mass terms in the superpotential with a particular R-charge arrangement is helpful to bypass the no-go theorem, and the resulting gaugino mass is suppressed by the messenger mass scale.Comment: 8 pages, 7 figures; v2: discussion on Driac gauginos and references added; v3: a section on bypassing the no-go added, R-charge notation changed; v4: typos, EPJC pre-published versio

The class of shareholdings and its impacts on corporate performance: a case of state shareholding composition in Chinese publicly listed companies.

Does the class of shareholdings matter for corporate performance? To address the question, our paper starts by classifying shareholdings on the basis of the principle of ultimate ownership. At present, the shareholding structure of Chinese quoted companies is state-dominant in that 84% of public companies ultimately are found controlled by the state, compared with 16% of non-statecontrolled ones. In contrast to our identified shareholdings, the Chinese official shareholding record only reports the state and the legal person share classes that are inevitably ambiguous for the identification of ultimate owners of public corporations, which in turn has misled many previous studies in assessing the impact of shareholding classes on performance. Based on our newly established shareholding classes, we make a nested performance comparison between these different classes, such as the state direct control versus the state indirect control, and find significant evidence from the Chinese data that the class of shareholdings does matter for company performance. The least inefficient shareholding class is the holding companies that are wholly listed and have focused industrial business through the state indirect control of the downstream public corporations. This finding provides ground for us to think more about how the corporate control mechanism could be further improved in China’s current corporate governance reform

Topological invariants for holographic semimetals

We study the behavior of fermion spectral functions for the holographic topological Weyl and nodal line semimetals. We calculate the topological invariants from the Green functions of both holographic semimetals using the topological Hamiltonian method, which calculates topological invariants of strongly interacting systems from an effective Hamiltonian system with the same topological structure. Nontrivial topological invariants for both systems have been obtained and the presence of nontrivial topological invariants further supports the topological nature of the holographic semimetals.Comment: 39 pages, 11 figures, 1 table; v2: match published versio

Topological nodal line semimetals in holography

We show a holographic model of a strongly coupled topological nodal line semimetal (NLSM) and find that the NLSM phase could go through a quantum phase transition to a topologically trivial state. The dual fermion spectral function shows that there are multiple Fermi surfaces each of which is a closed nodal loop in the NLSM phase. The topological structure in the bulk is induced by the IR interplay between the dual mass operator and the operator that deforms the topology of the Fermi surface. We propose a practical framework for building various strongly coupled topological semimetals in holography, which indicates that at strong coupling topologically nontrivial semimetal states generally exist.Comment: 21 pages, 5 figures; v2: match published versio