87 research outputs found
Non-Native Attitudes to /θ/ and /ð/: A European Case Study
This paper investigates the evaluation of the English sounds /θ/ and /ð/ as produced by European non-native speakers. Using the data from a larger web survey, we compared the error judgements by different native and non-native users of English. This was done to establish whether there is any normative convergence among European non-native speakers, or if this was counteracted by other patterns, such as the presence or absence of these sounds in their L1s. Our analysis shows that while European non-native judges do not differ consistently from native-speakers in their judgements, there are also subtle differences between different groups of non-native speakers, implying that we should be careful not to generalise across groups about non-native attitudes to these sounds
Fermion-Higgs model with Reduced Staggered Fermions
We introduce a lattice fermion-Higgs model with one component `reduced
staggered' fermions. In order to use the fermion field as efficiently as
possible we couple the two {\em staggered} flavors to the O(4) Higgs field
leading to a model with only one SU(2) doublet in the scaling region. The
number of fermions is doubled in a numerical investigation of the model with
the hybrid Monte Carlo algorithm. We present results for the phase diagram,
particle masses and renormalized couplings on lattices ranging in size from
to .Comment: 11 pages of text plus 4 postscript figures. Amsterdam ITFA 92-13,
Juelich HLRZ 92-2
Staggered fermions for chiral gauge theories: Test on a two-dimensional axial-vector model
As a first step towards constructing chiral models on the lattice with
staggered fermions, we study a U(1) model with axial-vector coupling to an
external gauge field in two dimensions. In our approach gauge invariance is
broken, but it is restored in the classical continuum limit. We find that the
continuum divergence relations for the vector and axial-vector currents are
reproduced, up to contact terms, which we determine analytically. The current
divergence relations are also studied numerically for smooth external gauge
fields with topological charge zero. We furthermore investigate the effect of
fluctuating gauge transformations and of gauge configurations with non-trivial
topological charge.Comment: 17 pages, 5 postscript figures (appended), ITFA 93-13, UCSD/PTH 93-1
Two-dimensional model of dynamical fermion mass generation in strongly coupled gauge theories
We generalize the Schwinger model on the lattice by adding a charged
scalar field. In this so-called model the scalar field shields
the fermion charge, and a neutral fermion, acquiring mass dynamically, is
present in the spectrum. We study numerically the mass of this fermion at
various large fixed values of the gauge coupling by varying the effective
four-fermion coupling, and find an indication that its scaling behavior is the
same as that of the fermion mass in the chiral Gross-Neveu model. This suggests
that the model is in the same universality class as the
Gross-Neveu model, and thus renormalizable and asymptotic free at arbitrary
strong gauge coupling.Comment: 18 pages, LaTeX2e, requires packages rotating.sty and curves.sty from
CTA
The Coupled Cluster Method in Hamiltonian Lattice Field Theory
The coupled cluster or exp S form of the eigenvalue problem for lattice
Hamiltonian QCD (without quarks) is investigated. A new construction
prescription is given for the calculation of the relevant coupled cluster
matrix elements with respect to an orthogonal and independent loop space basis.
The method avoids the explicit introduction of gauge group coupling
coefficients by mapping the eigenvalue problem onto a suitable set of character
functions, which allows a simplified procedure. Using appropriate group
theoretical methods, we show that it is possible to set up the eigenvalue
problem for eigenstates having arbitrary lattice momentum and lattice angular
momentum.Comment: LaTeX, no figur
Intestinal Tropism of a Betacoronavirus (Merbecovirus) in Nathusius’s Pipistrelle Bat (Pipistrellus nathusii), Its Natural Host
The emergence of several bat coronavirus-related disease outbreaks in human and domestic animals has fueled surveillance of coronaviruses in bats worldwide. However, little is known about how these viruses interact with their natural hosts. We demonstrate a Betacoronavirus (subgenus Merbecovirus), PN-βCoV, in the intestine of its natural host, Nathusius’s Pipistrelle Bat (Pipistrellus nathusii), by combining molecular and microscopy techniques. Eighty-eight P. nathusii bat carcasses were tested for PN-βCoV RNA by RT-qPCR, of which 25 bats (28%) tested positive. PN-βCoV RNA was more often detected in samples of the intestinal tract than in other sample types. In addition, viral RNA loads were higher in intestinal samples compared to other sample types, both on average and in each individual bat. In one bat, we demonstrated Merbecovirus antigen and PN-βCoV RNA expression in intestinal epithelium and the underlying connective tissue using immunohistochemistry and in situ hybridization, respectively. These results indicate that PN-βCoV has a tropism for the intestinal epithelium of its natural host, Nathusius’s Pipistrelle Bat, and imply that the fecal-oral route is a possible route of transmission.</p
Index Theorem and Overlap Formalism with Naive and Minimally Doubled Fermions
We present a theoretical foundation for the Index theorem in naive and
minimally doubled lattice fermions by studying the spectral flow of a Hermitean
version of Dirac operators. We utilize the point splitting method to implement
flavored mass terms, which play an important role in constructing proper
Hermitean operators. We show the spectral flow correctly detects the index of
the would-be zero modes which is determined by gauge field topology. Using the
flavored mass terms, we present new types of overlap fermions from the naive
fermion kernels, with a number of flavors that depends on the choice of the
mass terms. We succeed to obtain a single-flavor naive overlap fermion which
maintains hypercubic symmetry.Comment: 27 pages, 17 figures; references added, version accepted in JHE
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