On a theory of neutrino oscillations with entanglement

We show that, despite appearances, a theoretical approach to neutrino oscillation in which the neutrino and its interaction partners are entangled yields the standard result for the neutrino oscillation wavelength. We also shed some light on the question of why plane-wave approaches to the neutrino oscillation problem can yield the correct oscillation wavelength even though they do not explicitly account for the localization of the neutrino source and the detector.Comment: RevTeX 4, 12 pages, 1 figure; v2: Minor clarifications, references adde

Three modes of adaptive speciation in spatially structured populations

Adaptive speciation with gene flow via the evolution of assortative mating has classically been studied in one of two different scenarios. First, speciation can occur if frequency-dependent competition in sympatry induces disruptive selection, leading to indirect selection for mating with similar phenotypes. Second, if a subpopulation is locally adapted to a specific environment, there is indirect selection against hybridizing with maladapted immigrants. While both of these mechanisms have been modeled many times, the literature lacks models that allow direct comparisons between them. Here, we incorporate both frequency-dependent competition and local adaptation into a single model, and investigate whether and how they interact in driving speciation. We report two main results. First, we show that, individually, the two mechanisms operate under separate conditions, hardly influencing each other when one of them alone is sufficient to drive speciation. Second, we also find that the two mechanisms can operate together, leading to a third speciation mode, in which speciation is initiated by selection against maladapted migrants, but completed by within-deme competition in a distinct second phase. While this third mode bears some similarity to classical reinforcement, it happens considerably faster, and both newly formed species go on to coexist in sympatry. KEYWRODS: parapatric speciation, adaptive speciation, assortative mating, frequency dependent selection, reinforement, local adaptatio

An Analytically Tractable Model for Competitive Speciation

Several recent models have shown that frequency-dependent disruptive selection created by intraspecific competition can lead to the evolution of assortative mating 4 and, thus, to competitive sympatric speciation. However, since most results from these 5 models rely on limited numerical analyses, their generality has been subject to considerable debate. Here, we consider one of the standard models, the so-called Roughgarden model, with a simplified genetics where the selected trait is determined by a single diallelic locus. This model is sufficiently complex to maintain key properties of the general multilocus case, but still simple enough to allow for a comprehensive analytical treatment. By means of invasion fitness analysis, we describe the impact of all model parameters on the evolution of assortative mating. Depending on (1) the strength and (2) shape of stabilizing selection, (3) the strength and (4) shape of pairwise competition, (5) the shape of the mating function, and (6) the type of assortative mating, which may or may not lead to sexual selection, we find five different evolutionary regimes. In one of these regimes, the evolution of complete reproductive isolation is possible through arbitrarily small steps in the strength of assortative mating. Our approach provides a mechanistic understanding of several phenomena that have been found in previous models. The results demonstrate how, even in a simple model of competitive speciation, results depend in a complex way on ecological and genetic parameters

Magnetic excitations in two-leg spin 1/2 ladders: experiment and theory

Magnetic excitations in two-leg S=1/2 ladders are studied both experimentally and theoretically. Experimentally, we report on the reflectivity, the transmission and the optical conductivity sigma(omega) of undoped La_x Ca_14-x Cu_24 O_41 for x=4, 5, and 5.2. Using two different theoretical approaches (Jordan-Wigner fermions and perturbation theory), we calculate the dispersion of the elementary triplets, the optical conductivity and the momentum-resolved spectral density of two-triplet excitations for 0.2 <= J_parallel/J_perpendicular <= 1.2. We discuss phonon-assisted two-triplet absorption, the existence of two-triplet bound states, the two-triplet continuum, and the size of the exchange parameters.Comment: 6 pages, 7 eps figures, submitted to SNS 200

Human HT-29 colon carcinoma cells contain mucarinic M3_3 receptors coupled to phosphoinositide metabolism

Five different musearlnie receptor subtypes ean be distinguished by the differenees in their amino aeid sequence, the eoupled signal transduetion system, pharmaeologieal binding properties and aetivation of ionie fluxes. The present study served to eharaeterize the binding profile of musearlnie receptors in human eolon eareinoma eells (HT-29) using seleetive musearlnie antagonists. The affinities of the compounds were eompared with their poteney to inhibit cholinergieally-aetivated phosphoinositide metabolism. Pirenzepine displaced [$^3$H]N-methyl-scopolamine binding and inhibited inositolphosphate (IP) release with potencies typieal of those of non-M$_1$ receptors. The M$_3$ subtype-selective antagonists sila-hexocyelium and hexahydro-sila-difenidol bad high affinity to the musearlnie reeeptors in HT-29 cells (K0 = 3.1 nM and 27 nM, respectively) and inhibited IP release at nanomolar concentrations. The M$_2$ receptor antagonists, AF-DX 116 and methoctramine, had low antimusearinic poteneies. Our results demonstrate that HT-29 human colon earcinoma cells contain an apparently pure population of M$_3$ receptors. These cells could serve as a model system for further investigations coneerning regulatory and signal transduction mechanisms associated with glandular muscarinic M$_3$ receptors

Crossover from hc/e to hc/2e current oscillations in rings of s-wave superconductors

We analyze the crossover from an hc/e-periodicity of the persistent current in flux threaded clean metallic rings towards an hc/2e-flux periodicity of the supercurrent upon entering the superconducting state. On the basis of a model calculation for a one-dimensional ring we identify the underlying mechanism, which balances the hc/e versus the hc/2e periodic components of the current density. When the ring circumference exceeds the coherence length of the superconductor, the flux dependence is strictly hc/2e periodic. Further, we develop a multi-channel model which reduces the Bogoliubov - de Gennes equations to a one-dimensional differential equation for the radial component of the wave function. The discretization of this differential equation introduces transverse channels, whose number scales with the thickness of the ring. The periodicity crossover is analyzed close the critical temperature

Operation Of The NuMi Beam Monitoring System

The NuMI (Neutrinos at the Main Injector) facility produces an intense neutrino beam for experiments. The NuMI Beam Monitoring system consists of four arrays of ion chambers that measure the intensity and distribution of the remnant hadron and tertiary muon beams produced in association with the neutrinos. The ion chambers operate in an environment of high particle fluxes and high radiation.Physic