30,411 research outputs found
Commercialising Australia's interstate rail freight transport: Some ownership and investment issues
The paper addresses the issues of rights of way ownership and application of consistent investment appraisal techniques across modes of transport. There are linkages between ownership, rights of way, competitive strategies and market contestability which will have a significant bearing on the choice of investment criteria used by commercialised railways. Investment methodologies in competing modes of land transport must be consistent. Investment in individual elements of railway infrastructure must be integrated with the overall cost recovery strategy of the operator. Major railway projects must be submitted to both financial and economic evaluation, so that the interests of individual railway authorities and the community are considered
Global-String and Vortex Superfluids in a Supersymmetric Scenario
The main goal of this work is to investigate the possibility of finding the
supersymmetric version of the U(1)-global string model which behaves as a
vortex-superfluid. To describe the superfluid phase, we introduce a
Lorentz-symmetry breaking background that, in an approach based on
supersymmetry, leads to a discussion on the relation between the violation of
Lorentz symmetry and explicit soft supersymmetry breakings. We also study the
relation between the string configuration and the vortex-superfluid phase. In
the framework we settle down in terms of superspace and superfields, we
actually establish a duality between the vortex degrees of freedom and the
component fields of the Kalb-Ramond superfield. We make also considerations
about the fermionic excitations that may appear in connection with the vortex
formation.Comment: 9 pages. This version presented the relation between Lorentz symmetry
violation by the background and the appearance of terms that explicitly break
SUS
Note on Shadowing and Diffraction in Deep-Inelastic Lepton Scattering
We discuss the close relation between shadowing in deep-inelastic
lepton-nucleus scattering and diffractive photo- and leptoproduction of hadrons
from free nucleons. We show that the magnitude of nuclear shadowing at small
Bjorken-x, as measured by the E665 and NMC collaborations, is directly related
to HERA data on the amount of diffraction in the scattering from free nucleons.Comment: 6 pages, Latex, to be published in Eur. Phys. J.
Flavour symmetries in a renormalizable SO(10) model
In the context of a renormalizable supersymmetric SO(10) Grand Unified
Theory, we consider the fermion mass matrices generated by the Yukawa couplings
to a representation
of scalars. We perform a complete investigation of the possibilities of
imposing flavour symmetries in this scenario; the purpose is to reduce the
number of Yukawa coupling constants in order to identify potentially predictive
models. We have found that there are only 14 inequivalent cases of Yukawa
coupling matrices, out of which 13 cases are generated by symmetries,
with suitable , and one case is generated by a symmetry. A
numerical analysis of the 14 cases reveals that only two of them---dubbed A and
B in the present paper---allow good fits to the experimentally known fermion
masses and mixings.Comment: 36 pages, no figures, revised fits using newer data, added fit for
case A, added references, new appendices concerning the SO(10) scalar
potential and inequalities for the vacuum expectation values, conclusions
unchanged; some minor changes, matches published versio
Scotogenic model for co-bimaximal mixing
We present a scotogenic model, i.e. a one-loop neutrino mass model with dark
right-handed neutrino gauge singlets and one inert dark scalar gauge doublet
, which has symmetries that lead to co-bimaximal mixing, i.e. to an
atmospheric mixing angle and to a -violating phase
, while the mixing angle remains arbitrary.
The symmetries consist of softly broken lepton numbers (), a non-standard symmetry, and three symmetries. We
indicate two possibilities for extending the model to the quark sector. Since
the model has, besides , three scalar gauge doublets, we perform a
thorough discussion of its scalar sector. We demonstrate that it can
accommodate a Standard Model-like scalar with mass , with
all the other charged and neutral scalars having much higher masses.Comment: v2 - 23 pages, 5 figures, minor changes requested by refere
Molecule survival in magnetized protostellar disk winds. II. Predicted H2O line profiles versus Herschel/HIFI observations
We investigate whether the broad wings of H2O emission identified with
Herschel towards low-mass Class 0 and Class 1 protostars may be consistent with
an origin in a dusty MHD disk wind, and the constraints it would set on the
underlying disk properties. We present synthetic H2O line profiles predictions
for a typical MHD disk wind solution with various values of disk accretion
rate, stellar mass, extension of the launching area, and view angle. We compare
them in terms of line shapes and intensities with the HIFI profiles observed by
the WISH Key Program. We find that a dusty MHD disk wind launched from 0.2--0.6
AU AU to 3--25 AU can reproduce to a remarkable degree the observed shapes and
intensities of the broad H2O component, both in the fundamental 557 GHz line
and in more excited lines. Such a model also readily reproduces the observed
correlation of 557 GHz line luminosity with envelope density, if the infall
rate at 1000 AU is 1--3 times the disk accretion rate in the wind ejection
region. It is also compatible with the typical disk size and bolometric
luminosity in the observed targets. However, the narrower line profiles in
Class 1 sources suggest that MHD disk winds in these sources, if present, would
have to be slower and/or less water rich than in Class 0 sources. In
conclusion, MHD disk winds appear as a valid (though not unique) option to
consider for the origin of the broad H2O component in low-mass protostars. ALMA
appears ideally suited to further test this model by searching for resolved
signatures of the warm and slow wide-angle molecular wind that would be
predicted.Comment: accepted for publication in A&
- …