254,693 research outputs found
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
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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
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