5,029 research outputs found
Stabilization of Unstable Procedures: The Recursive Projection Method
Fixed-point iterative procedures for solving nonlinear parameter dependent problems can converge for some interval of parameter values and diverge as the parameter changes. The Recursive Projection Method (RPM), which stabilizes such procedures by computing a projection onto the unstable subspace is presented. On this subspace a Newton or special Newton iteration is performed, and the fixed-point iteration is used on the complement. As continuation in the parameter proceeds, the projection is efficiently updated, possibly increasing or decreasing the dimension of the unstable subspace. The method is extremely effective when the dimension of the unstable subspace is small compared to the dimension of the system. Convergence proofs are given and pseudo-arclength continuation on the unstable subspace is introduced to allow continuation past folds. Examples are presented for an important application of the RPM in which a “black-box” time integration scheme is stabilized, enabling it to compute unstable steady states. The RPM can also be used to accelerate iterative procedures when slow convergence is due to a few slowly decaying modes
Modified Higgs couplings and unitarity violation
Prompted by the recent observation of a Higgs-like particle at the CERN Large
Hadron Collider (LHC), we investigate a quantitative correlation between
possible departures of the gauge and Yukawa couplings of this particle from
their Standard Model expectations and the scale of unitarity violation in the
processes and .Comment: 6 pages, 6 eps figures, Arrayeq.sty attached; v2: minor updates,
version published: PRD 87 (2013) 011702(R), Rapid Communicatio
Scalar sector properties of two-Higgs-doublet models with a global U(1) symmetry
We analyze the scalar sector properties of a general class of
two-Higgs-doublet models which has a global U(1) symmetry in the quartic terms.
We find constraints on the parameters of the potential from the considerations
of unitarity of scattering amplitudes, the global stability of the potential
and the -parameter. We concentrate on the spectrum of the non-standard
scalar masses in the decoupling limit which is preferred by the Higgs data at
the LHC. We exhibit charged-Higgs induced contributions to the diphoton decay
width of the 125\,GeV Higgs boson and its correlation with the corresponding
width.Comment: 12 pages, 15 eps figure files; minor modifications made and a few
references adde
New constraints on R-parity violation from proton stability
We derive stringent upper bounds on all the -type
combinations from the consideration of proton stability, where
are baryon-number-violating trilinear couplings and
are lepton-number-violating bilinear mass parameters in a R-parity-violating
supersymmetric theory.Comment: 4 pages, Latex, uses axodraw.sty (in the revised version all
combinations of the form have been constrained, using
one-loop graphs) To appear in Phys. Lett.
Parallel hybrid textures of lepton mass matrices
We analyse the parallel hybrid texture structures in the charged lepton and
the neutrino sector. These parallel hybrid texture structures have physical
implications as they cannot be obtained from arbitrary lepton mass matrices
through weak basis transformations. The total sixty parallel hybrid texture
structures can be grouped into twelve classes, and all the hybrid textures in
the same class have identical physical implications. We examine all the twelve
classes under the assumption of non-factorizable phases in the neutrino mass
matrix. Five out of the total twelve classes are found to be phenomenologically
disallowed. We study the phenomenological implications of the allowed classes
for 1-3 mixing angle, Majorana and Dirac-type violating phases.
Interesting constraints on effective Majorana mass are obtained for all the
allowed classes.Comment: Physical Review D (To appear
- …