1,673 research outputs found
Hierarchy and Polysynchrony in an adaptive network
We describe a simple adaptive network of coupled chaotic maps. The network
reaches a stationary state (frozen topology) for all values of the coupling
parameter, although the dynamics of the maps at the nodes of the network can be
non-trivial. The structure of the network shows interesting hierarchical
properties and in certain parameter regions the dynamics is polysynchronous:
nodes can be divided in differently synchronized classes but contrary to
cluster synchronization, nodes in the same class need not be connected to each
other. These complicated synchrony patterns have been conjectured to play roles
in systems biology and circuits. The adaptive system we study describes ways
whereby this behaviour can evolve from undifferentiated nodes.Comment: 13 pages, 17 figure
Can one detect new physics in I=0 and/or I=2 contributions to the decays B --> pi pi?
We study the effects of new-physics contributions to B --> pi pi decays,
which can be parametrized as four new complex quantities. A simple analysis is
provided by utilizing the reparametrization invariance of the decay amplitudes.
We find that six quantities can be reabsorbed into the definitions of Standard
Model-like parameters. As a result, the usual isospin analysis provides only
two constraints on new physics which are independent of estimates for the
Standard Model contributions. In particular, we show that one is not sensitive
to new physics affecting the I=0 amplitudes. On the other hand, I=2 new physics
can be detected, and its parameters can be measured by using independent
determinations of the weak phases. We obtain constraints on these new-physics
parameters through a fit to the current experimental data.Comment: 8 pages, RevTe
Measurements of New Physics in B -> pi pi Decays
If new physics (NP) is present in B -> pi pi decays, it can affect the
isospin I=2 or I=0 channels. In this paper, we discuss various methods for
detecting and measuring this NP. The techniques have increasing amounts of
theoretical hadronic input. If NP is eventually detected in B -> pi pi -- there
is no evidence for it at present -- one will be able to distinguish I=2 and
I=0, and measure its parameters, using these methods.Comment: 24 pages, no figures, revte
Families of piecewise linear maps with constant Lyapunov exponent
We consider families of piecewise linear maps in which the moduli of the two
slopes take different values. In some parameter regions, despite the variations
in the dynamics, the Lyapunov exponent and the topological entropy remain
constant. We provide numerical evidence of this fact and we prove it
analytically for some special cases. The mechanism is very different from that
of the logistic map and we conjecture that the Lyapunov plateaus reflect
arithmetic relations between the slopes.Comment: 26 pages, 13 figure
Emergence of hierarchical networks and polysynchronous behaviour in simple adaptive systems
We describe the dynamics of a simple adaptive network. The network
architecture evolves to a number of disconnected components on which the
dynamics is characterized by the possibility of differently synchronized nodes
within the same network (polysynchronous states). These systems may have
implications for the evolutionary emergence of polysynchrony and hierarchical
networks in physical or biological systems modeled by adaptive networks.Comment: 4 pages, 4 figure
Adverse effects from SIMCE outcomes in Chile
Durante la dictadura militar en Chile se realiza una reforma educativa que considera el paso de una educación pública a una de mercado. En este contexto surge el SIMCE como evaluación externa, a través de la que se pretende dar información de los resultados académicos o calidad educativa de los centros. Sin embargo, este sistema de Rendición de cuentas de alto impacto genera efectos indeseados debido a la forma en que se entregan los resultados y el uso que se hace de ellos, así como por las consecuencias que conlleva para los centros el obtener altos o bajos puntajesDuring the military dictatorship in Chile, an educational reformation is carried out that considers the transition from a public education to a market one. At this time, SIMCE arise as an external evaluation, with the aim of provide information about academic outcomes or about educational quality of the schools. However, this high impact accountability system generates adverse effects because of the way that the results are delivered and the use of them, as well as the consequences for the schools of obtain high or low score
Reparametrization invariance of B decay amplitudes and implications for new physics searches in B decays
When studying B decays within the Standard Model, it is customary to use the
unitarity of the CKM matrix in order to write the decay amplitudes in terms of
only two of the three weak phases which appear in the various diagrams.
Occasionally, it is mentioned that those two weak phases can be used in order
to describe any decay amplitude, even beyond the Standard Model. Here we point
out that, when describing a generic decay amplitude, the two weak phases can be
chosen completely at will, and we study the behavior of the decay amplitudes
under changes in the two weak phases chosen as a basis. Of course, physical
observables cannot depend on such reparametrizations. This has an impact in
discussions of the SM and in attempts to parametrize new physics effects in the
decay amplitudes. We illustrate these issues by looking at B --> psi K_S and
the isospin analysis in B --> pi pi.Comment: 16 pages, RevTe
Bounds on gamma from CP violation measurements in B -> pi+ pi- and B -> psi K_S
We study the determination of gamma from CP-violating observables in B -> pi+
pi- and B -> psi K_S. This determination requires theoretical input to one
combination of hadronic parameters. We show that a mild assumption about this
quantity may allow bounds to be placed on gamma, but we stress the pernicious
effects that an eightfold discrete ambiguity has on such an analysis. The
bounds are discussed as a function of the direct (C) and interference (S)
CP-violating observables obtained from time-dependent B -> pi+ pi- decays, and
their behavior in the presence of new physics effects in B-Bbar mixing is
studied. (V2: Misprints corrected. Slightly improved discussion.)Comment: 11 pages, RevTex 4, 5 eps figures include
Symmetry Constrained Two Higgs Doublet Models
We study Two-Higgs-Doublet Models (2HDM) where Abelian symmetries have been
introduced, leading to a drastic reduction in the number of free parameters in
the 2HDM. Our analysis is inspired in BGL models, where, as the result of a
symmetry of the Lagrangian, there are tree-level scalar mediated
Flavour-Changing-Neutral-Currents, with the flavour structure depending only on
the CKM matrix. A systematic analysis is done on the various possible schemes,
which are classified in different classes, depending on the way the extra
symmetries constrain the matrices of couplings defining the flavour structure
of the scalar mediated neutral currents. All the resulting flavour textures of
the Yukawa couplings are stable under renormalisation since they result from
symmetries imposed at the Lagrangian level. We also present a brief
phenomenological analysis of the most salient features of each class of
symmetry constrained 2HDM.Comment: 30 pages, 5 Table
Lepton-Flavour Violation in Ordinary and Supersymmetric Grand Unified Theories
By an explicit calculation we show that in ordinary SU(5) logarithmic
divergence in the amplitude of cancels among diagrams and
remaining finite part is suppressed by at least . In SUSY SU(5),
when the effect of flavour changing wave function renormalization is taken into
account such logarithmic correction disappears, provided a condition is met
among SUSY breaking masses. In SUGRA-inspired SUSY GUT the remaining
logarithmic effect is argued not to be taken as a prediction of the theory.Comment: 8 pages, LaTeX209 file, using axodraw.st
- …