1,117 research outputs found
Renormalization Group Analysis of \rho-Meson Properties at Finite Density
We calculate the density dependence of the -meson mass and coupling
constant() for -nucleon-nucleon vertex at one loop using the
lagrangian where the -meson is included as a dynamical gauge boson of a
hidden local symmetry. From the condition that thermodynamic potential should
not depend on the arbitrary energy scale, renormalization scale, one can
construct a renormalization group equation for the thermodynamic potential and
argue that the various renormalization group coefficients are functions of the
density or temperature. We calculate the -function for
-nucleon-nucleon coupling constant () and -function
for -meson mass (). We found that the -meson mass
and the coupling constant for drop as density increases in the
low energy limit.Comment: 24 pages, 10 figures, revised versio
Lorentz gauge theory as a model of emergent gravity
We consider a class of Lorentz gauge gravity theories within Riemann-Cartan
geometry which admits a topological phase in the gravitational sector. The
dynamic content of such theories is determined only by the contortion part of
the Lorentz gauge connection. We demonstrate that there is a unique Lagrangian
that admits propagating spin one mode in correspondence with gauge theories of
other fundamental interactions. Remarkably, despite the R^2 type of the
Lagrangian and non-compact structure of the Lorentz gauge group, the model
possesses rather a positive-definite Hamiltonian. This has been proved in the
lowest order of perturbation theory. This implies further consistent
quantization and leads to renormalizable quantum theory. It is assumed that the
proposed model describes possible mechanism of emergent Einstein gravity at
very early stages of the Universe due to quantum dynamics of contortion.Comment: 11 pages, final version, minor correction
Can majority support save an endangered language? A case study of language attitudes in Guernsey
Many studies of minority language revitalisation focus on the attitudes and perceptions of minorities, but not on those of majority group members. This paper discusses the implications of these issues, and presents research into majority andf minority attitudes towards the endangered indigenous vernacular of Guernsey, Channel Islands. The research used a multi-method approach (questionnaire and interview) to obtain attitudinal data from a representative sample of the population that included politicians and civil servants (209 participants). The findings suggested a shift in language ideology away from the post-second world war ‘culture of modernisation’ and monolingual ideal, towards recognition of the value of a bi/trilingual linguistic heritage. Public opinion in Guernsey now seems to support the maintenance of the indigenous language variety, which has led to a degree of official support. The paper then discusses to what extent this ‘attitude shift’ is reflected in linguistic behaviour and in concrete language planning measures
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The XWS open access catalogue of extreme European windstorms from 1979 to 2012
The XWS (eXtreme WindStorms) catalogue consists of storm tracks and model-generated maximum 3 s wind-gust footprints for 50 of the most extreme winter windstorms to hit Europe in the period 1979–2012. The catalogue is intended to be a valuable resource for both academia and industries such as (re)insurance, for example allowing users to characterise extreme European storms, and validate climate and catastrophe models. Several storm severity indices were investigated to find which could best represent a list of known high-loss (severe) storms. The best-performing index was Sft, which is a combination of storm area calculated from the storm footprint and maximum 925 hPa wind speed from the storm track. All the listed severe storms are included in the catalogue, and the remaining ones were selected using Sft. A comparison of the model footprint to station observations revealed that storms were generally well represented, although for some storms the highest gusts were underestimated. Possible reasons for this underestimation include the model failing to simulate strong enough pressure gradients and not representing convective gusts.
A new recalibration method was developed to estimate the true distribution of gusts at each grid point and correct for this underestimation. The recalibration model allows for storm-to-storm variation which is essential given that different storms have different degrees of model bias. The catalogue is available at www.europeanwindstorms.org
Meson Exchange Effect on Color Superconductivity
We investigate the effects of pion and gluon exchanges on the formation of
two-flavor color superconductivity at moderate density, . The
chiral quark model proposed by Manohar and Georgi containing pions as well as
gluons is employed to show that the pion exchange reduces substantially the
value of the superconducting gap gotten with the gluon exchange only. It turns
out that the pion exchanges produce a repulsion between quark-quark pair in a
spin and isospin singlet state.
We suggest that the phase consisiting of pions, gluons and quarks is one of
the candidates of in-medium QCD phase at moderate density.Comment: 8 pages, 1 figure, minor correction
Symmetry energy of dense matter in holographic QCD
We study the nuclear symmetry energy of dense matter using holographic QCD.
To this end, we consider two flavor branes with equal quark masses in a
D4/D6/D6 model. We find that at all densities the symmetry energy monotonically
increases. At small densities, it exhibits a power law behavior with the
density, .Comment: 9 pages, 3 figure
Appreciative inquiry as a method of transforming identity and power in Pakistani women
This paper describes a three-year action research project that used Appreciative Inquiry to work with marginalised Pakistani women living in Sheffield. The research encountered many of the difficulties and dilemmas that have been previously identified in the theory and practice of Appreciative Inquiry. However, it also empowered the participants to develop critical thinking, particularly around issues of power and identity. Through generating authentic and untold stories, Appreciative Inquiry enabled participants to discuss, subvert and challenge the identities that had been constructed for them by sources of power within their community and culture. The paper describes the innovative application of Appreciative Inquiry, offers a theoretical response to criticisms of Appreciative Inquiry and suggests how it may be effective in enabling marginalised people to critically address issues of powe
Precision Determination of the Neutron Spin Structure Function g1n
We report on a precision measurement of the neutron spin structure function
using deep inelastic scattering of polarized electrons by polarized
^3He. For the kinematic range 0.014<x<0.7 and 1 (GeV/c)^2< Q^2< 17 (GeV/c)^2,
we obtain at an average . We find relatively large negative
values for at low . The results call into question the usual Regge
theory method for extrapolating to x=0 to find the full neutron integral
, needed for testing quark-parton model and QCD sum rules.Comment: 5 pages, 3 figures To be published in Phys. Rev. Let
Quark Number Susceptibility with Finite Chemical Potential in Holographic QCD
We study the quark number susceptibility in holographic QCD with a finite
chemical potential or under an external magnetic field at finite temperature.
We first consider the quark number susceptibility with the chemical potential.
We observe that approaching the critical temperature from high temperature
regime, the quark number susceptibility divided by temperature square develops
a peak as we increase the chemical potential, which confirms recent lattice QCD
results. We discuss this behavior in connection with the existence of the
critical end point in the QCD phase diagram. We also consider the quark number
susceptibility under the external magnetic field. We predict that the quark
number susceptibility exhibits a blow-up behavior at low temperature as we
raise the value of the magnetic field. We finally spell out some limitations of
our study.Comment: 25 pages, 3 figures, published versio
Measurement of the diffractive structure function in deep inelastic scattering at HERA
This paper presents an analysis of the inclusive properties of diffractive
deep inelastic scattering events produced in interactions at HERA. The
events are characterised by a rapidity gap between the outgoing proton system
and the remaining hadronic system. Inclusive distributions are presented and
compared with Monte Carlo models for diffractive processes. The data are
consistent with models where the pomeron structure function has a hard and a
soft contribution. The diffractive structure function is measured as a function
of \xpom, the momentum fraction lost by the proton, of , the momentum
fraction of the struck quark with respect to \xpom, and of . The \xpom
dependence is consistent with the form \xpoma where
in all bins of and
. In the measured range, the diffractive structure function
approximately scales with at fixed . In an Ingelman-Schlein type
model, where commonly used pomeron flux factor normalisations are assumed, it
is found that the quarks within the pomeron do not saturate the momentum sum
rule.Comment: 36 pages, latex, 11 figures appended as uuencoded fil
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