Search results for "dynamical system"
showing 10 items of 523 documents
Attracteur de polarisation dans les fibres optiques
2004
Nous etudions la dynamique non lineaire des etats de polarisation de deux ondes coherentes ou incoherentes se propageant dans une fibre optique. Nous presentons en particulier un effet original d'attraction de la polarisation.
Anomalies in b→s Transitions and Dark Matter
2018
Since 2013, the LHCb collaboration has reported on the measurement of several observables associated to $b \to s$ transitions, finding various deviations from their predicted values in the Standard Model. These include a set of deviations in branching ratios and angular observables, as well as in the observables $R_K$ and $R_{K^\ast}$, specially built to test the possible violation of Lepton Flavor Universality. Even though these tantalizing hints are not conclusive yet, the $b \to s$ anomalies have gained considerable attention in the flavor community. Here we review New Physics models that address these anomalies and explore their possible connection to the dark matter of the Universe. Af…
Ising model universality for two-dimensional lattices
1993
We use the single-cluster Monte Carlo update algorithm to simulate the Ising model on two-dimensional Poissonian random lattices of Delaunay type with up to 80\,000 sites. By applying reweighting techniques and finite-size scaling analyses to time-series data near criticality, we obtain unambiguous support that the critical exponents for the random lattice agree with the exactly known exponents for regular lattices, i.e., that (lattice) universality holds for the two-dimensional Ising model.
Are the B decay anomalies related to neutrino oscillations?
2015
5 pages.- 2 figures.- v2: 1 ref. added.- v3: matches
Neutrino masses from new generations
2011
We reconsider the possibility that Majorana masses for the three known neutrinos are generated radiatively by the presence of a fourth generation and one right-handed neutrino with Yukawa couplings and a Majorana mass term. We find that the observed light neutrino mass hierarchy is not compatible with low energy universality bounds in this minimal scenario, but all present data can be accommodated with five generations and two right-handed neutrinos. Within this framework, we explore the parameter space regions which are currently allowed and could lead to observable effects in neutrinoless double beta decay, $\mu - e$ conversion in nuclei and $\mu \rightarrow e \gamma$ experiments. We also…
Constraints from lepton universality at the z-peak on unified theories
1995
We suggest the use of a universality-breaking observable based on lepton asymmetries as derived from the left-right asymmetry and the $\tau$ polarization at the $Z$ peak, which can efficiently constrain the parameter space of unified theories. The new observable is complementary to the leptonic partial width differences and it depends critically on the chirality of a possible non-universal $Z$-boson coupling to like-flavour leptons. The LEP/SLC potential of probing universality violation is discussed in representative low-energy extensions of the Standard Model (SM) that could be derived by supersymmetric grand unified theories, such as the SM with left-handed and/or right-handed neutral is…
Probing Supersymmetric Grand Unification through Flavor Physics
2007
Flavor Changing Neutral Current (FCNC) and CP violating processes are a powerful tool to probe the Standard Model (SM) and, hence, to constrain or obtain indirect hints of New Physics (NP) beyond it. Within Supersymmetric Grand Unified theories it is generally possible to link processes occurring in the leptonic and hadronic sectors; thus, their correlated analysis provides a very interesting low energy test for a Grand Unified theory at high energies. Similarly to the FCNC decays, we also show that the Lepton Flavor Universality tests in low-energy systems ( K l 2 and π l 2 ) offer a unique opportunity in shedding light on physics beyond the Standard Model; the smallness of NP effects is m…
Bifurcations of phase portraits of a Singular Nonlinear Equation of the Second Class
2014
Abstract The soliton dynamics is studied using the Frenkel Kontorova (FK) model with non-convex interparticle interactions immersed in a parameterized on-site substrate potential. The case of a deformable substrate potential allows theoretical adaptation of the model to various physical situations. Non-convex interactions in lattice systems lead to a number of interesting phenomena that cannot be produced with linear coupling alone. In the continuum limit for such a model, the particles are governed by a Singular Nonlinear Equation of the Second Class. The dynamical behavior of traveling wave solutions is studied by using the theory of bifurcations of dynamical systems. Under different para…
Agreement of Neutrino Deep Inelastic Scattering Data with Global Fits of Parton Distributions
2013
The compatibility of neutrino-nucleus deep inelastic scattering data within the universal, factorizable nuclear parton distribution functions has been studied independently by several groups in the past few years. The conclusions are contradictory, ranging from a violation of the universality up to a good agreement, most of the controversy originating from the use of the neutrino-nucleus data from the NuTeV Collaboration. Here, we pay attention to non-negligible differences in the absolute normalization between different neutrino data sets. We find that such variations are large enough to prevent a tensionless fit to all data simultaneously and could therefore misleadingly point towards non…
Lepton nonuniversality in exclusive b→sℓℓ decays
2017
The LHCb measurements of certain ratios of decay modes testing lepton flavor nonuniversality might open an exciting world of new physics beyond the standard model. The latest LHCb measurements of ${R}_{{K}^{*}}$ offer some new insight beyond the previous measurement of ${R}_{K}$. We work out the present significance for nonuniversality, and argue that claims of $5\ensuremath{\sigma}$ deviations from the standard model based on all present $b\ensuremath{\rightarrow}s{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ data including the ratios are misleading and are at present still based on guesstimates of hadronic power corrections in the $b\ensuremath{\rightarrow}s{\ensuremath{\el…