7,410 research outputs found
Question of Peccei-Quinn symmetry and quark masses in the economical 3-3-1 model
We show that there is an infinite number of U(1) symmetries like Peccei-Quinn
symmetry in the 3-3-1 model with minimal scalar sector---two scalar triplets.
Moreover, all of them are completely broken due to the model's scalars by
themselves (notice that these scalars as known have been often used to break
the gauge symmetry and generating the masses for the model's particles). There
is no any residual Peccei-Quinn symmetry. Because of the minimal scalar content
there are some quarks that are massless at tree-level, but they can get
consistent mass contributions at one-loop due to this fact. Interestingly,
axions as associated with the mentioned U(1)s breaking (including Majoron due
to lepton-charge breaking) are all gauged away because they are also the
Goldstone bosons responsible for the gauge symmetry breaking as usual.Comment: 25 pages, 4 figures, revised version, to appear in Physical Review
Effect of Disorder in the Frustrated Ising FCC Antiferromagnet: Phase Diagram and Stretched Exponential Relaxation
We study the phase transition in a face-centered-cubic antiferromagnet with
Ising spins as a function of the concentration of ferromagnetic bonds
randomly introduced into the system. Such a model describes the spin-glass
phase at strong bond disorder. Using the standard Monte Carlo simulation and
the powerful Wang-Landau flat-histogram method, we carry out in this work
intensive simulations over the whole range of . We show that the first-order
transition disappears with a tiny amount of ferromagnetic bonds, namely , in agreement with theories and simulations on other 3D models. The
antiferromagnetic long-range order is also destroyed with a very small
(). With increasing , the system changes into a spin glass and
then to a ferromagnetic phase when . The phase diagram in the space
() shows an asymmetry, unlike the case of the Ising spin glass
on the simple cubic lattice. We calculate the relaxation time around the
spin-glass transition temperature and we show that the spin autocorrelation
follows a stretched exponential relaxation law where the factor is equal to
at the transition as suggested by the percolation-based theory.
This value is in agreement with experiments performed on various spin glasses
and with Monte Carlo simulations on different SG models
Large signal of within the constraints of decays in the 3-3-1 model with neutral leptons
In the framework of the 3-3-1 model with neutral leptons, we have
investigated the lepton-flavor-violating sources based on the Higgs mass
spectrum which has two neutral Higgses identitied with corresponding ones in
the Two-Higgs-Doublet model (THDM). On the scale of the LHC,
we point out the parameter space regions where the experimental limits of decays are satisfied. These regions depend heavily on
the mixing of exotic leptons but are predicted to have large signals. We also show that
can reach a value of .Comment: 30 pages, 9 figure
State-constraint static Hamilton-Jacobi equations in nested domains
We study state-constraint static Hamilton-Jacobi equations in a sequence of
domains in such that for all . We obtain rates of convergence
of , the solution to the state-constraint problem in , to ,
the solution to the corresponding problem in . In many cases, the rates obtained are proven to be
optimal. Various new examples and discussions are provided at the end of the
paper.Comment: 23 pages, 1 figur
Tournament-Based Incentives and Mergers and Acquisitions
This research examines the relation between tournament-based incentives, which are proxied by the difference between a firm’s CEO pay and the median pay of the senior managers, and mergers and acquisitions (M&As). We find that tournament-based incentives are positively related to firm acquisitiveness and acquiring firms’ stock and operating performance. Further analysis indicates that positive acquisition performance increases the likelihood of the CEO being promoted from inside the acquiring firm. Our evidence is consistent with the view that tournament-based incentives motivate acquiring firms’ managers to make greater efforts and take more risk that result in superior acquisition performance
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