2,139 research outputs found
Fermionic symmetry-protected topological state in strained graphene
The low-energy physics of graphene is described by relativistic Dirac
fermions with spin and valley degrees of freedom. Mechanical strain can be used
to create a pseudo magnetic field pointing to opposite directions in the two
valleys. We study interacting electrons in graphene exposed to both an external
real magnetic field and a strain-induced pseudo magnetic field. For a certain
ratio between these two fields, it is proposed that a fermionic
symmetry-protected topological state can be realized. The state is
characterized in detail using model wave functions, Chern-Simons field theory,
and numerical calculations. Our paper suggests that graphene with artificial
gauge fields may host a rich set of topological states.Comment: 8 pages, 4 figure
Mergers and acquisitions matching for performance improvement: a DEA-based approach
This article proposes a new data envelopment analysis (DEA)-based
approach to deal with mergers and acquisitions (M&As) matching.
To derive reliable matching degrees between bidder and target
firms, we consider both technical efficiency and scale efficiency.
Specifically, an inverse DEA model is developed for measuring the
technical efficiency, while a conventional DEA model is employed to
identify the return of scale of the merged decision-making units
(DMUs). Then, an optimization model is formulated to generate
matching results to improve DMUs’ performance. An empirical study
of M&As matching Turkish energy firms is examined to illustrate the
proposed approach. This study shows that both technical efficiency
and scale efficiency have impacts on M&As matching practices
Threshold effects as the origin of , and observed in
We investigate the decay via various rescattering
diagrams. Without introducing genuine exotic resonances, it is shown that the
, and reported by the LHCb collaboration
can be simulated by the , and threshold cusps, respectively. These cusps are enhanced by some nearby
triangle singularities. The with cannot be well simulated
by the threshold effects in our model, which implies that it may be a genuine
resonance.Comment: 7 pages, 6 figures, 2 table
- …