A Continuous Time GARCH Process of Higher Order

A continuous time GARCH model of order (p,q) is introduced, which is driven by a single Lévy process. It extends many of the features of discrete time GARCH(p,q) processes to a continuous time setting. When p=q=1, the process thus defined reduces to the COGARCH(1,1) process of Klüppelberg, Lindner and Maller (2004). We give sufficient conditions for the existence of stationary solutions and show that the volatility process has the same autocorrelation structure as a continuous time ARMA process. The autocorrelation of the squared increments of the process is also investigated, and conditions ensuring a positive volatility are discussed

Optimization of a neutrino factory oscillation experiment

We discuss the optimization of a neutrino factory experiment for neutrino oscillation physics in terms of muon energy, baselines, and oscillation channels (gold, silver, platinum). In addition, we study the impact and requirements for detector technology improvements, and we compare the results to beta beams. We find that the optimized neutrino factory has two baselines, one at about 3000 to 5000km, the other at about 7500km (``magic'' baseline). The threshold and energy resolution of the golden channel detector have the most promising optimization potential. This, in turn, could be used to lower the muon energy from about 50GeV to about 20GeV. Furthermore, the inclusion of electron neutrino appearance with charge identification (platinum channel) could help for large values of \sin^2 2 \theta_{13}. Though tau neutrino appearance with charge identification (silver channel) helps, in principle, to resolve degeneracies for intermediate \sin^2 2 \theta_{13}, we find that alternative strategies may be more feasible in this parameter range. As far as matter density uncertainties are concerned, we demonstrate that their impact can be reduced by the combination of different baselines and channels. Finally, in comparison to beta beams and other alternative technologies, we clearly can establish a superior performance for a neutrino factory in the case \sin^2 2 \theta_{13} < 0.01.Comment: 51 pages, 25 figures, 6 tables, references corrected, final version to appear in Phys. Rev.

Leptogenesis in models with keV sterile neutrino dark matter

We analyze leptogenesis in gauge extensions of the Standard Model with keV sterile neutrino dark matter. We find that both the observed dark matter abundance and the correct baryon asymmetry of the Universe can simultaneously emerge in these models. Both the dark matter abundance and the leptogenesis are controlled by the out of equilibrium decays of the same heavy right handed neutrino.Comment: 6 pages, 1 figur

Molecular, morphological, and phytochemical evidence for a broad species concept of Plagiochila bifaria (Hepaticae)

Debate over the synonymy of the European Plagiochila killarniensis and the Neotropical P bifaria of R sect. Arrectae has focused on differences in secondary metabolite composition. The broad morphological species concept of R bifaria proposed in recent papers has now been tested by comparing nrDNA ITS1 and ITS2 sequences of R bifaria populations encompassing several different morpho- and chemotypes from the British Isles, Tenerife, Costa Rica, Brazil, Ecuador, and Bolivia, with sequences of other species of R sects. Arrectae, Rutilantes, and Fuscoluteae. Phylogenetic analyses demonstrate that specimens of P. bifaria form a well supported clade within Plagiochila sect. Arrectae. Sequences of R bifaria from the British Isles, Tenerife, and Ecuador, representing the "methyl everninate" chemotype, form a well supported subclade within the P bifaria clade. Sequences of specimens from Costa Rica, Brazil, and Bolivia are placed in the basal part of the R bifaria clade. The data support a broad species concept of P bifaria. The different chemotypes do not warrant distinct taxonomic ranks. Plagiochila centrifuga and P. compressula are treated as new synonyms of R bifaria

Heavy Quark Physics From Lattice QCD

We review the application of lattice QCD to the phenomenology of b- and c-quarks. After a short discussion of the lattice techniques used to evaluate hadronic matrix elements and the corresponding systematic uncertainties, we summarise results for leptonic decay constants, B--Bbar mixing, semileptonic and rare radiative decays. A discussion of the determination of heavy quark effective theory parameters is followed by an explanation of the difficulty in applying lattice methods to exclusive nonleptonic decays.Comment: 52 pages LaTeX with 10 eps files. Requires: hfsprocl.sty (included) plus axodraw.sty, rotating.sty and array.sty. To appear in Heavy Flavours (2nd edition) edited by A J Buras and M Lindner (World Scientific, Singapore). Revised version corrects typo in axis labelling of Fig 1

Universal transport signatures of Majorana fermions in superconductor-Luttinger liquid junctions

One of the most promising proposals for engineering topological superconductivity and Majorana fermions employs a spin-orbit coupled nanowire subjected to a magnetic field and proximate to an s-wave superconductor. When only part of the wire's length contacts to the superconductor, the remaining conducting portion serves as a natural lead that can be used to probe these Majorana modes via tunneling. The enhanced role of interactions in one dimension dictates that this configuration should be viewed as a superconductor-Luttinger liquid junction. We investigate such junctions between both helical and spinful Luttinger liquids, and topological as well as non-topological superconductors. We determine the phase diagram for each case and show that universal low-energy transport in these systems is governed by fixed points describing either perfect normal reflection or perfect Andreev reflection. In addition to capturing (in some instances) the familiar Majorana-mediated `zero-bias anomaly' in a new framework, we show that interactions yield dramatic consequences in certain regimes. Indeed, we establish that strong repulsion removes this conductance anomaly altogether while strong attraction produces dynamically generated effective Majorana modes even in a junction with a trivial superconductor. Interactions further lead to striking signatures in the local density of states and the line-shape of the conductance peak at finite voltage, and also are essential for establishing smoking-gun transport signatures of Majorana fermions in spinful Luttinger liquid junctions.Comment: 25 pages, 6 figures, v

Physics and optimization of beta-beams: From low to very high gamma

The physics potential of beta beams is investigated from low to very high gamma values and it is compared to superbeams and neutrino factories. The gamma factor and the baseline are treated as continuous variables in the optimization of the beta beam, while a fixed mass water Cherenkov detector or a totally active scintillator detector is assumed. We include in our discussion also the gamma dependence of the number of ion decays per year. For low gamma, we find that a beta beam could be a very interesting alternative to a superbeam upgrade, especially if it is operated at the second oscillation maximum to reduce correlations and degeneracies. For high gamma, we find that a beta beam could have a potential similar to a neutrino factory. In all cases, the sensitivity of the beta beams to CP violation is very impressive if similar neutrino and anti-neutrino event rates can be achieved.Comment: 34 pages, 16 figures, Fig. 2 modified, discussion improved, refs. added, version to appear in PR

keV sterile neutrino dark matter in gauge extensions of the standard model

It is known that a keV scale sterile neutrino is a good warm dark matter candidate. We study how this possibility could be realized in the context of gauge extensions of the standard model. The na\"ive expectation leads to large thermal overproduction of sterile neutrinos in this setup. However, we find that it is possible to use out-of-equilibrium decay of the other right-handed neutrinos of the model to dilute the present density of the keV sterile neutrinos and achieve the observed dark matter density. We present the universal requirements that should be satisfied by the gauge extensions of the standard model, containing right-handed neutrinos, to be viable models of warm dark matter, and provide a simple example in the context of the left-right symmetric model.Comment: RevTex, 13 pages, 5 figures; journal version (corrected typos

PMT Test Facility at MPIK Heidelberg and Double Chooz Super Vertical Slice

Proceedings supplement for conference poster at Neutrino 2010, Athens, Greece

Symmetric Brownian motor

In this paper we present a model of a symmetric Brownian motor (SBM) which changes the sign of its velocity when the temperature gradient is inverted. The velocity, external work and efficiency are studied as a function of the temperatures of the baths and other relevant parameters. The motor shows a current reversal when another parameter (a phase shift) is varied. Analytical predictions and results from numerical simulations are performed and agree very well. Generic properties of this type of motors are discussed.Comment: 8 pages and 10 figure