737 research outputs found
Corrections to the Nuclear Axial Vector Coupling in a Nuclear Medium
We examine further corrections to the time component of the axial vector
coupling constant in a nuclear medium. The dominant correction is that of
exchange currents. The corrections we examine make the remaining discrepancy
worse.Comment: 6 pages, 2 figure
Longitudinal gluons and Nambu-Goldstone bosons in a two-flavor color superconductor
In a two-flavor color superconductor, the SU(3)_c gauge symmetry is
spontaneously broken by diquark condensation. The Nambu-Goldstone excitations
of the diquark condensate mix with the gluons associated with the broken
generators of the original gauge group. It is shown how one can decouple these
modes with a particular choice of 't Hooft gauge. We then explicitly compute
the spectral density for transverse and longitudinal gluons of adjoint color 8.
The Nambu-Goldstone excitations give rise to a singularity in the real part of
the longitudinal gluon self-energy. This leads to a vanishing gluon spectral
density for energies and momenta located on the dispersion branch of the
Nambu-Goldstone excitations.Comment: 16 pages, 4 figures, minor revisions to text, one ref. adde
Bound state spectra of three-body muonic molecular ions
The results of highly accurate calculations are presented for all twenty-two
known bound and states in the six
three-body muonic molecular ions and
. A number of bound state properties of these muonic molecular ions have
been determined numerically to high accuracy. The dependence of the total
energies of these muonic molecules upon particle masses is considered. We also
discuss the current status of muon-catalysis of nuclear fusion reactions.Comment: This is the final version. All `techical' troubles with the
Latex-file have been resolved. A few misprints/mistakes in the text were
correcte
The climate change risk management matrix for the grazing industry of northern Australia
The complexity, variability and vastness of the northern Australian rangelands make it difficult to assess the risks associated with climate change. In this paper we present a methodology to help industry and primary producers assess risks associated with climate change and to assess the effectiveness of adaptation options in managing those risks. Our assessment involved three steps. Initially, the impacts and adaptation responses were documented in matrices by âexpertsâ (rangeland and climate scientists). Then, a modified risk management framework was used to develop risk management matrices that identified important impacts, areas of greatest vulnerability (combination of potential impact and adaptive capacity) and priority areas for action at the industry level. The process was easy to implement and useful for arranging and analysing large amounts of information (both complex and interacting). Lastly, regional extension officers (after minimal âclimate literacyâ training) could build on existing knowledge provided here and implement the risk management process in workshops with rangeland land managers. Their participation is likely to identify relevant and robust adaptive responses that are most likely to be included in regional and property management decisions. The process developed here for the grazing industry could be modified and used in other industries and sectors.
By 2030, some areas of northern Australia will experience more droughts and lower summer rainfall. This poses a serious threat to the rangelands. Although the impacts and adaptive responses will vary between ecological and geographic systems, climate change is expected to have noticeable detrimental effects: reduced pasture growth and surface water availability; increased competition from woody vegetation; decreased production per head (beef and wool) and gross margin; and adverse impacts on biodiversity. Further research and development is needed to identify the most vulnerable regions, and to inform policy in time to facilitate transitional change and enable land managers to implement those changes
Gluon self-energy in a two-flavor color superconductor
The energy and momentum dependence of the gluon self-energy is investigated
in a color superconductor with two flavors of massless quarks. The presence of
a color-superconducting quark-quark condensate modifies the gluon self-energy
for energies which are of the order of the gap parameter. For gluon energies
much larger than the gap, the self-energy assumes the form given by the
standard hard-dense loop approximation. It is shown that this modification of
the gluon self-energy does not affect the magnitude of the gap to leading and
subleading order in the weak-coupling limit.Comment: 21 pages, 6 figures, RevTeX, aps and epsfig style files require
Fluctuation modes in color-superconductors
We investigate fluctuation effects of a gap parameter in
color-superconductors. The fluctuation modes in the super phase are described
by two scalar fields of diquarks. One of them is a Nambu-Goldstone boson and
the other is a diquark boson whose mass is about twice of the gap energy (an
extended quasi-supersymmetry). In the normal phase the fluctuation becomes a
precursory (soft) mode whose amplitude increases near the critical temperature.Comment: 6 page
Slow-roll Inflation with the Gauss-Bonnet and Chern-Simons Corrections
We study slow-roll inflation with the Gauss-Bonnet and Chern-Simons
corrections. We obtain general formulas for the observables: spectral indices,
tensor-to-scalar ratio and circular polarization of gravitational waves. The
Gauss-Bonnet term violates the consistency relation r = -8n_T. Particularly,
blue spectrum n_T > 0 and scale invariant spectrum |8n_T|/r << 1 of tensor
modes are possible. These cases require the Gauss-Bonnet coupling function of
\xi _{,\phi } \sim 10^8/M_{Pl}. We use examples to show new-inflation-type
potential with 10M_{Pl} symmetry breaking scale and potential with flat region
in \phi \gtrsim 10M_{Pl} lead to observationally consistent blue and scale
invariant spectra, respectively. Hence, these interesting cases can actually be
realized. The Chern-Simons term produce circularly polarized tensor modes. We
show an observation of these signals supports existence of the Chern-Simons
coupling function of \omega _{,\phi } \sim 10^8/M_{Pl}. Thus, with future
observations, we can fix or constrain the value of these coupling functions, at
the CMB scale.Comment: 21 pages, 5 figure
The impact of neighbourhood walkability on the effectiveness of a structured education programme to increase objectively measured walking
Background: Incorporating physical activity into daily activities is key for the effectiveness of lifestyle education interventions aimed at improving health outcomes; however, consideration of the environmental context in which individuals live is not always made. Walkability is a characteristic of the physical environment, and may be a potential facilitator to changing physical activity levels. Methods: Using data collected during the Walking Away from Diabetes randomised controlled trial, we examined the association between the walkability of the home neighbourhood and physical activity of participants. We also determined whether home neighbourhood walkability of participants was associated with the intervention effect of the education programme. Results: Data from 706 participants were available for analysis. Neighbourhood walkability was not significantly associated with any of the physical activity measures at baseline, or at 12, 24 or 36 months following the intervention (p>0.05 for all). There was no association between walkability and change in purposeful steps/ day from baseline to 36months in the usual care or intervention arm; 25.77 (-99.04, 150.58) and 42.97 (-327.63, 413.45) respectively. Conclusion: Neighbourhood walkability appeared to have no association with objectively-measured physical activity in this population. Furthermore, the walkability of participantâs neighbourhood did not influence the effectiveness of a lifestyle programme
Partial Deconfinement in Color Superconductivity
We analyze the fate of the unbroken SU(2) color gauge interactions for 2
light flavors color superconductivity at non zero temperature. Using a simple
model we compute the deconfining/confining critical temperature and show that
is smaller than the critical temperature for the onset of the superconductive
state itself. The breaking of Lorentz invariance, induced already at zero
temperature by the quark chemical potential, is shown to heavily affect the
value of the critical temperature and all of the relevant features related to
the deconfining transition. Modifying the Polyakov loop model to describe the
SU(2) immersed in the diquark medium we argue that the deconfinement transition
is second order. Having constructed part of the equation of state for the 2
color superconducting phase at low temperatures our results are relevant for
the physics of compact objects featuring a two flavor color superconductive
state.Comment: 9 pp, 4 eps-figs, version to appear in PR
Supernovae, Hypernovae and Color Superconductivity
We argue that Color Superconductivity (CSC, Cooper pairing in quark matter
leading to the breaking of SU(3) color symmetry) may play a role in triggering
the explosive endpoint of stellar evolution in massive stars (M > 8 M_{\odot}).
We show that the binding energy release in the transition of a sub-core region
to the CSC phase can be of the same order of magnitude as the gravitational
binding energy release from core collapse. The core temperature during collapse
is likely below the critical temperature for CSC, and the transition is first
order, proceeding on Fermi timescales when the pressure reaches a critical
value of several times nuclear density. We also discuss the implications for
hypernova events with total ejecta energy of 10-100 times that of type II
supernova.Comment: 8 pages, LaTe
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