19,199 research outputs found
Asymptotic approximation of eigenvalues of vector equations
A vectorial extension of the Keller-Rubinow method of computing asymptotic approximations of eigenvalues in bounded domains is presented. The method is applied to the problem of a multimode step-profile cylindrical optical fibre, including the effects of polarisation. A comparison of the asymptotic results with the exact eigenvalues is made when these are available, and the agreement is shown to be good
Decorous lower bounds for minimum linear arrangement
Minimum Linear Arrangement is a classical basic combinatorial optimization problem from the 1960s, which turns out to be extremely challenging in practice. In particular, for most of its benchmark instances, even the order of magnitude of the optimal solution value is unknown, as testified by the surveys on the problem that contain tables in which the best known solution value often has one more digit than the best known lower bound value. In this paper, we propose a linear-programming based approach to compute lower bounds on the optimum. This allows us, for the first time, to show that the best known solutions are indeed not far from optimal for most of the benchmark instances
Higgs couplings and new signals from Flavon-Higgs mixing effects within multi-scalar models
Testing the properties of the Higgs particle discovered at the LHC and
searching for new physics signals, are some of the most important tasks of
Particle Physics today. Current measurements of the Higgs couplings to fermions
and gauge bosons, seem consistent with the Standard Model, and when taken as a
function of the particle mass, should lay on a single line. However, in models
with an extended Higgs sector the diagonal Higgs couplings to up-quarks,
down-quarks and charged leptons, could lay on different lines, while
non-diagonal flavor-violating Higgs couplings could appear too. We describe
these possibilities within the context of multi-Higgs doublet models that
employ the Froggatt-Nielsen (FN) mechanism to generate the Yukawa hierarchies.
Furthermore, one of the doublets can be chosen to be of the inert type, which
provides a viable dark matter candidate. The mixing of the Higgs doublets with
the flavon field, can provide plenty of interesting signals, including: i)
small corrections to the couplings of the SM-like Higgs, ii) exotic signals
from the flavon fields, iii) new signatures from the heavy Higgs bosons. These
aspects are studied within a specific model with 3+1 Higgs doublets and a
singlet FN field. Constraints on the model are derived from the study of K and
D mixing and the Higgs search at the LHC. For last, the implications from the
latter aforementioned constraints to the FCNC top decay are presented
too.Comment: 10 pages, 3 figures and 2 tables; v2: author added, text improved;
v3: Title and Abstract slightly changed, 19 pages, references, tables and
images added, additional clarifications; matches version published by Nucl.
Phys.
Texture zeros and hierarchical masses from flavour (mis)alignment
We introduce an unconventional interpretation of the fermion mass matrix
elements. As the full rotational freedom of the gauge-kinetic terms renders a
set of infinite bases called weak bases, basis-dependent structures as mass
matrices are unphysical. Matrix invariants, on the other hand, provide a set of
basis-independent objects which are of more relevance. We employ one of these
invariants to give a new parametrization of the mass matrices. By virtue of it,
one gains control over its implicit implications on several mass matrix
structures. The key element is the trace invariant which resembles the equation
of a hypersphere with a radius equal to the Frobenius norm of the mass matrix.
With the concepts of alignment or misalignment we can identify texture zeros
with certain alignments whereas Froggatt-Nielsen structures in the matrix
elements are governed by misalignment. This method allows further insights of
traditional approaches to the underlying flavour geometry.Comment: 27 pages; v2 matches version accepted by NPB, discussion on Dirac CP
phase for neutrinos adde
From particle segregation to the granular clock
Recently several authors studied the segregation of particles for a system
composed of mono-dispersed inelastic spheres contained in a box divided by a
wall in the middle. The system exhibited a symmetry breaking leading to an
overpopulation of particles in one side of the box. Here we study the
segregation of a mixture of particles composed of inelastic hard spheres and
fluidized by a vibrating wall. Our numerical simulations show a rich
phenomenology: horizontal segregation and periodic behavior. We also propose an
empirical system of ODEs representing the proportion of each type of particles
and the segregation flux of particles. These equations reproduce the major
features observed by the simulations.Comment: 10 page
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