Exact solutions of Dirac equation on (1+1)-dimensional spacetime coupled to a static scalar field

We use a generalized scheme of supersymmetric quantum mechanics to obtain the energy spectrum and wave function for Dirac equation in (1+1)-dimensional spacetime coupled to a static scalar field.Comment: 7 pages, Late

Molecular species discovery in the diatom <i>Sellaphora</i> and its congruence with mating trials

Many diatom and other microbial eukaryote morphospecies consist of a variable number of (pseudo)cryptic species, with obvious consequences for such fields as biogeography and community ecology. Here, we investigated the species limits of morphologically similar small–celled strains of the model diatom Sellaphora from the United Kingdom and Australia, using cox1 mitochondrial and rbcL chloroplast gene sequences. Based on cox1 sequence data, the sequenced strains belonged to six closely related lineages, presumably species, of which one corresponds to the previously described S. auldreekie D.G. Mann & S.M. McDonald. Although rbcL displayed less sequence variation, the same six lineages were also recovered in an rbcL phylogeny of the genus. Molecular species discovery was compared to mating trials involving three of the lineages, showing that they were reproductively isolated. Incomplete evidence from a fourth lineage suggested that it too was reproductively isolated. A posteriori examination of light microscope morphology revealed no simple metrics or presence/absence characters that could consistently separate all species of the auldreekie complex, even though some do differ in pole width or stria density. While it is premature to make conclusions about their biogeography, it is obvious that a number of cryptic Sellaphora species thus far undetected in the UK are easily found at several localities in warm–temperate Australia

Checklist of the shore and epipelagic fishes of Tonga

A checklist is given below of 1162 species of shore and epipelagic fishes belonging to 111 families that occur in the islands of Tonga, South Pacifie Ocean; 40 of these are epipelagic species. As might be expected, the fish fauna of Tonga is most similar to those of Samoa and Fiji; at least 658 species of the fishes found in Tonga are also known from Fiji and the islands of Samoa. Twelve species of shore fishes are presently known only from Tonga. Specimens of Tongan fishes are housed mainly in the fish collections of the National Museum ofNatural History, Washington D.C.; Bernice P. Bishop Museum, Honolulu; Museum National d'Histoire Naturelle, Paris; and the Australian Museum, Sydney. Native Tongan names offishes, when known, are presented afterspecies names

Equivalence between the real time Feynman histories and the quantum shutter approaches for the "passage time" in tunneling

We show the equivalence of the functions $G_{\rm p}(t)$ and $|\Psi(d,t)|^2$ for the ``passage time'' in tunneling. The former, obtained within the framework of the real time Feynman histories approach to the tunneling time problem, using the Gell-Mann and Hartle's decoherence functional, and the latter involving an exact analytical solution to the time-dependent Schr\"{o}dinger equation for cutoff initial waves

μ−e\mu-e conversion in nuclei within the CMSSM seesaw: universality versus non-universality

In this paper we study $\mu-e$ conversion in nuclei within the context of the Constrained Minimal Supersymmetric Standard Model, enlarged by three right handed neutrinos and their supersymmetric partners, and where the neutrino masses are generated via a seesaw mechanism. Two different scenarios with either universal or non-universal soft supersymmetry breaking Higgs masses at the gauge coupling unification scale are considered. In the first part we present a complete one-loop computation of the conversion rate for this process that includes the photon-, $Z$-boson, and Higgs-boson penguins, as well as box diagrams, and compare their size in the two considered scenarios. Then, in these two scenarios we analyse the relevance of the various parameters on the conversion rates, particularly emphasising the role played by the heavy neutrino masses, $\tan \beta$, and especially $\theta_{13}$. In the case of hierachical heavy neutrinos, an extremely high sensitivity of the rates to $\theta_{13}$ is indeed found. The last part of this work is devoted to the study of the interesting loss of correlation between the $\mu-e$ conversion and $\mu \to e \gamma$ rates that occurs in the non-universal scenario. In the case of large $\tan \beta$ and light $H^0$ Higgs boson an enhanced ratio of the $\mu-e$ to $\mu \to e \gamma$ rates, with respect to the universal case is found, and this could be tested with the future experimental sensitivities.Comment: 48 pages, 15 figures. Minor typos corrected and some references adde

Expanding and Collapsing Scalar Field Thin Shell

This paper deals with the dynamics of scalar field thin shell in the Reissner-Nordstr$\ddot{o}$m geometry. The Israel junction conditions between Reissner-Nordstr$\ddot{o}$m spacetimes are derived, which lead to the equation of motion of scalar field shell and Klien-Gordon equation. These equations are solved numerically by taking scalar field model with the quadratic scalar potential. It is found that solution represents the expanding and collapsing scalar field shell. For the better understanding of this problem, we investigate the case of massless scalar field (by taking the scalar field potential zero). Also, we evaluate the scalar field potential when $p$ is an explicit function of $R$. We conclude that both massless as well as massive scalar field shell can expand to infinity at constant rate or collapse to zero size forming a curvature singularity or bounce under suitable conditions.Comment: 15 pages, 11 figure

Sneutrino cold dark matter, a new analysis: relic abundance and detection rates

We perform a new and updated analysis of sneutrinos as dark matter candidates, in different classes of supersymmetric models. We extend previous analyses by studying sneutrino phenomenology for full variations of the supersymmetric parameters which define the various models. We first revisit the standard Minimal Supersymmetric Standard Model, concluding that sneutrinos are marginally compatible with existing experimental bounds, including direct detection, provided they compose a subdominant component of dark matter. We then study supersymmetric models with the inclusion of right-handed fields and lepton-number violating terms. Simple versions of the lepton-number-violating models do not lead to phenomenology different from the standard case when the neutrino mass bounds are properly included. On the contrary, models with right-handed fields are perfectly viable: they predict sneutrinos which are compatible with the current direct detection sensitivities, both as subdominant and dominant dark matter components. We also study the indirect detection signals for such successful models: predictions for antiproton, antideuteron and gamma-ray fluxes are provided and compared with existing and future experimental sensitivities. The neutrino flux from the center of the Earth is also analyzed.Comment: 72 pages, 50 figures. The version on the archive has low-resolution figures. The paper with high resolution figures may be found through http://www.to.infn.it/~arina/papers or http://www.to.infn.it/~fornengo/Research/paperlist.htm

Long distance regularization in chiral perturbation theory with decuplet

We investigate the use of long distance regularization in SU(3) baryon chiral perturbation theory with decuplet fields. The one-loop decuplet contributions to the octet baryon masses, axial couplings, S-wave nonleptonic hyperon decays and magnetic moments are evaluated in a chirally consistent fashion by employing a cutoff to implement long distance regularization. The convergence of the chiral expansions of these quantities is improved compared to the dimensionally regularized version which indicates that the propagation of Goldstone bosons over distances smaller than a typical hadronic size, which is beyond the regime of chiral perturbation theory but included by dimensional regularization, is removed by use of a cutoff.Comment: 31 page

Dynamical Chiral Symmetry Breaking on the Light Front I. DLCQ Approach

Dynamical chiral symmetry breaking in the DLCQ method is investigated in detail using a chiral Yukawa model closely related to the Nambu-Jona-Lasinio model. By classically solving three constraints characteristic of the light-front formalism, we show that the chiral transformation defined on the light front is equivalent to the usual one when bare mass is absent. A quantum analysis demonstrates that a nonperturbative mean-field solution to the ``zero-mode constraint'' for a scalar boson (sigma) can develop a nonzero condensate while a perturbative solution cannot. This description is due to our identification of the ``zero-mode constraint'' with the gap equation. The mean-field calculation clarifies unusual chiral transformation properties of fermionic field, which resolves a seemingly inconsistency between triviality of the null-plane chiral charge Q_5|0>=0 and nonzero condensate. We also calculate masses of scalar and pseudoscalar bosons for both symmetric and broken phases, and eventually derive the PCAC relation and nonconservation of Q_5 in the broken phase.Comment: Revised version to appear in Phys. Rev. D. 19 pages, 4 figures, REVTEX. Derivation of the PCAC relation is given. Its relation to the nonconservation of chiral charge is clarified. 1 figure and some references adde

Electromagnetic Polarization Effects due to Axion Photon Mixing

We investigate the effect of axions on the polarization of electromagnetic waves as they propagate through astronomical distances. We analyze the change in the dispersion of the electromagnetic wave due to its mixing with axions. We find that this leads to a shift in polarization and turns out to be the dominant effect for a wide range of frequencies. We analyze whether this effect or the decay of photons into axions can explain the large scale anisotropies which have been observed in the polarizations of quasars and radio galaxies. We also comment on the possibility that the axion-photon mixing can explain the dimming of distant supernovae.Comment: 18 pages, 1 figur