Particle-hole symmetry and the nu=5/2 quantum Hall state

We discuss the implications of approximate particle-hole symmetry in a half-filled Landau level in which a paired quantum Hall state forms. We note that the Pfaffian state is not particle-hole symmetric. Therefore, in the limit of vanishing Landau-level mixing, in which particle-hole transformation is an exact symmetry, the Pfaffian spontaneously breaks this symmetry. There is a particle-hole conjugate state, which we call the anti-Pfaffian, which is degenerate with the Pfaffian in this limit. We observe that strong Landau-level mixing should favor the Pfaffian, but it is an open problem which state is favored for the moderate Landau-level mixing which is present in experiments. We discuss the bulk and edge physics of the anti-Pfaffian. We analyze a simplified model in which transitions between analogs of the two states can be studied in detail. Finally, we discuss experimental implications.     

Resonance phenomena and long-term chaotic advection in volume-preserving systems

Creating chaotic advection is the most efficient strategy to achieve mixing on microscale or in very viscous fluids. In this paper, we present a quantitative theory of the long-time resonant mixing in 3D near-integrable flows. We use the flow between two coaxial elliptic counter-rotating cylinders as a demonstrative model, where multiple scatterings on resonance result in mixing by causing the jumps of adiabatic invariants. We improve the existing estimates of the width of the mixing domain. We show that the resulting mixing both on short and long time scales can be described in terms of a single diffusion-type equation with a diffusion coefficient depending on the averaged effect of multiple passages through resonances. We discuss the exact location of the boundaries of the chaotic domain and show how it affects the properties of mixing.     

Knitting neutrino mass textures with or without Tri-Bi maximal mixing

The solar and baseline neutrino oscillation data suggest bimaximal neutrino mixing among the first two generations, and trimaximal mixing between all three neutrino flavors. It has been conjectured that this indicates the existence of an underlying symmetry for the leptonic fermion mass textures. The experimentally measured quantities, however, are associated to the latter indirectly and in a rather complicated way through the mixing matrices of the charged leptons and neutrinos. Motivated by these facts, we derive exact analytical expressions which directly link the charged lepton and neutrino mass and mixing parameters to measured quantities and obtain constraints on the parameter space. We discuss deviations from Tri-Bi mixing matrices and present minimal extensions of the Harrison, Perkins and Scott matrices capable of interpreting all neutrino data.     

Introduction to flavour and CP violation in the Standard Model and beyond

We define the Cabibbo–Kobayashi–Maskawa matrix and briefly discuss its present determination. We recall the formalism for heavy-meson mixing and CP violation in meson decays. Finally we extend our discussion of flavour and CP violation beyond the Standard Model.     

Control methods for problems of mixing and coherence in chaotic maps and flows

We review a variety of control methods which are capable of enhancing the chaoticity and mixing properties of chaotic flows and also methods which work towards promoting the coherence properties of such flows. We discuss a parameter control method which can enhance the chaoticity and the rate of mixing of dissipative as well as conservative flows and outline methods which promote global mixing by the addition of noise and by preventing island formation. As the inverse side of this problem, we summarize methods which can create coherent structures in chaotic dynamical flows. We also discuss the utility of these methods from the point of view of applications as well as for understanding phenomena which occur in natural systems.     

Gauge coupling renormalisation with several U(1) factors

We examine the renormalisation of gauge coupling constants in theories with a G × U(1)^N gauge group (which appears to be the gauge symmetry of many possible superstring vacua). In general, the abelian gauge bosons mix among themselves, so a correct renormalisation requires including this mixing in the evolution of the gauge couplings. We present general results and note that the mixing is scale independent to all orders if the renormalization group trajectory passes through a unification point. We discuss the cases of one loop and two loops explicitly. An example, based on a possible superstring-inspired model, is given.     

Electroweak interactions within a five quark model

We discuss the 5 quark model of Peskin and Tye. We derive the general form of the weak currents. The phenomenology of FCNC puts severe constraints on the mixing angles. When these constraints are fulfilled the model can hardly be distinguished from the standard model. A possible experimental test is radiative decay of theB ⁰ meson. In this model it is about an order of magnitude bigger. We also analyzed if the smallness of the mixing angles could be understood in a natural way. Using discrete symmetries we failed in finding a solution in agreement with all present data.     

Saturation of the all-optical Kerr effect in solids

We discuss the influence of the higher-order Kerr effect (HOKE) in wide bandgap solids at extreme intensities below the onset of optically induced damage. Using different theoretical models, we employ multiphoton absorption rates to compute the nonlinear refractive index by a Kramers-Kronig transform. Within this theoretical framework we provide an estimate for the appearance of significant deviations from the standard optical Kerr effect predicting a linear index change with intensity. We discuss the role of the observed saturation behavior in practically relevant situations, including Kerr lens mode-locking and supercontinuum generation in photonic crystal fibers. Furthermore, we present experimental data from a multiwave mixing experiment in BaF2, which can be explained by the appearance of the HOKE.     

Neutrino textures in light of Super-Kamiokande data and a realistic string model

Motivated by the Super-Kamiokande atmospheric neutrino data, we discuss possible textures for Majorana and Dirac neutrino masses within the see-saw framework. There are two main purposes of this paper: first, to gain intuition into this area from a purely phenomenological analysis, and second, to explore to what extent it may be realized in a specific model. We comment initially on the simplified two-generation case, emphasizing that large mixing is not incompatible with a large hierarchy of mass eigenvalues. We also emphasize that renormalization-group effects may amplify neutrino mixing, and we present semi-analytic expressions for estimating this amplification. Several examples are then given of three-family neutrino mass textures, which may also accommodate the persistent solar neutrino deficit, with different assumptions for the neutrino Dirac mass matrices. We comment on a few features of neutrino mass textures arising in models with a U(1) flavour symmetry. Finally, we discuss the possible pattern of neutrino masses in a “realistic” flipped SU(5) model derived from string theory, illustrating how a desirable pattern of mixing may emerge. Both small- or large-angle MSW solutions are possible, while a hierarchy of neutrino masses appears more natural than near-degeneracy. This model contains some unanticipated features that may be relevant in other models also: The neutrino Dirac matrices may not be related closely to the quark mass matrices, and the heavy Majorana states may include extra gauge-singlet fields. Received: 6 November 1998 / Published online: 18 June 1999     

Magnetically tuned spin dynamics resonance

We present the experimental observation of a magnetically tuned resonance phenomenon in the spin mixing dynamics of ultracold atomic gases. In particular, we study the magnetic field dependence of spin conversion in F=2 (87)Rb spinor condensates in the crossover from interaction dominated to quadratic Zeeman dominated dynamics. We discuss the observations in the framework of spin dynamics as well as matter wave four wave mixing. Furthermore, we show that the validity range of the single mode approximation for spin dynamics is significantly extended at high magnetic field.     

Transient degenerate four wave mixing in saturable absorbers

The transient behaviour of degenerate four wave mixing (DFWM) in a three-level saturable absorber is analysed. We discuss two cases which are relevant to present day experiments. We obtain the transient reflectivity in the cases where the pump beams consist of (a) a single pulse and (b) a train of pulses.     

Heavy neutrinos and lepton number violation in ?p colliders

We discuss the prospects of studying lepton number violating processes in order to identify Majorana neutrinos from low scale seesaw mechanisms at lepton-proton colliders. In particular, we consider the scenarios of colliding electrons with LHC energy protons and, motivated by the efforts towards the construction of a muon collider, the prospects of muon-proton collisions. We find that present constraints on the mixing of the Majorana neutrinos still allow for a detectable signal at these kind of facilities given the smallness of the Standard Model background. We discuss possible cuts in order to further increase the signal over background ratio and the prospects of reconstructing the neutrino mass from the kinematics of the final state particles.     

Effects of polarization-mode dispersion on fiber-based parametric amplification and wavelength conversion

We present a vector theory of four-wave mixing in optical fibers and use it to discuss the effect of polarization-mode dispersion (PMD) on the performance of parametric amplifiers and wavelength converters. We show that PMD distorts the gain spectrum and makes it less uniform than that expected in the absence of residual birefringence. PMD also induces large fluctuations in the amplified or wavelength-converted signal.     

Non-abelian gauge structure in neutrino mixing

We discuss the existence of a non-abelian gauge structure associated with flavor mixing. In the specific case of two flavor mixing of Dirac neutrino fields, we show that this reformulation allows to define flavor neutrino states which preserve the Poincaré structure. Phenomenological consequences of our analysis are explored.     

A parameterization of electro-weak mass matrices for quarks

We discuss quark flavor mixing and CP violation using a 10 parameter quark mass matrix in the electro-weak basis. The matrix handles the high mass of the top quark, 174±16 GeV, and contains two CP violating phases. We show that this scheme favors minimal CP violation by a single phase factor and leads to maximal CP violation in the standard parameterization of the quark flavor mixing matrix.     

Scalar glueball-q\bar{q} mixing above 1 GeV and implications for lattice QCD

Lattice QCD predictions have motivated several recent studies of the mixing between the predicted glueball and a nonet in the GeV region. We show that results from apparently different approaches have some common features, explain why this is so and abstract general conclusions. We place particular emphasis on the flavour dependent constraints imposed by decays of the , and to all pairs of pseudoscalar mesons. From these results we identify a systematic correlation between glueball mass, mixing, and flavour symmetry breaking and conclude that the glueball may be rather lighter than some quenched lattice QCD computations have suggested. We identify experimental tests that can determine the dynamics of a glueball in this mass region and discuss quantitatively the feasibility of decoding glueball- mixing. Received: 19 March 2001 / Published online: 17 August 2001     

Neutrino-neutralino mixing and one-loop corrections in the R-parity violating supersymmetric model

We consider the supersymmetric extension of the Standard Model with neutrino Yukawa interactions and R-parity violation. We calculate one-loop corrections to physical neutrino mass in case of neutrinoneutralino mixing and discuss the influence of this mass shift on parameter constraints.     

T2K indication of relatively large θ13 and a natural perturbation to the democratic neutrino mixing pattern

The T2K Collaboration has recently reported a remarkable indication of the ν→ν oscillation which is consistent with a relatively large value of θ₁₃ in the three-flavor neutrino mixing scheme. We show that it is possible to account for such a result of θ₁₃ by introducing a natural perturbation to the democratic neutrino mixing pattern, without or with CP violation. A testable correlation between θ₁₃ and θ₂₃ is predicted in this ansatz. We also discuss the Wolfenstein-like parametrization of neutrino mixing, and comment on other possibilities of generating sufficiently large θ₁₃ at the electroweak scale.     

The GSI oscillation mystery

In this talk, a short discussion of the GSI anomaly is given. We discuss the physics involved using a comparison with pion decay, and explain why the observed oscillations cannot be caused by standard neutrino mixing.     

Leptonic flavor and CP violation

Recent neutrino oscillation data teach us that the neutrinos have masses and that they mix. We discuss two ways that can be used to probe other non-standard leptonic physics. We show that non-standard neutrino interaction can be probed in neutrino oscillation experiments and discuss sneutrino-antisneutrino mixing.