555 research outputs found
Dependence of Variational Perturbation Expansions on Strong-Coupling Behavior. Inapplicability of delta-Expansion to Field Theory
We show that in applications of variational theory to quantum field theory it
is essential to account for the correct Wegner exponent omega governing the
approach to the strong-coupling, or scaling limit. Otherwise the procedure
either does not converge at all or to the wrong limit. This invalidates all
papers applying the so-called delta-expansion to quantum field theory.Comment: Author Information under
http://www.physik.fu-berlin.de/~kleinert/institution.html . Latest update of
paper (including all PS fonts) at
http://www.physik.fu-berlin.de/~kleinert/34
A geological model of the chalk of East Kent
This report describes the geological modelling of the Chalk in the North Downs of East Kent,
within the catchment of River Great Stour and eastwards to the coast, including the Isle of
Thanet. This work was funded by the Environment Agency to support investigations of the local
hydrogeology and thereby to enhance catchment management.
The whole area is underlain by the Upper Cretaceous Chalk Group, with the Palaeogene
succession of the Thanet Sand Formation, the Lambeth Group and the Thames Group overlying
it in the northern and central eastern parts.
The project included a desk study revision of the Chalk of the North Downs, using the new
Chalk lithostratigraphy. The revisions to the geology are shown on the 1:50 000 scale geological
map which accompanies this report. Together with evidence from boreholes and from seismic
surveys, the new outcrop patterns have been incorporated into a geological model, using both
computer software (EarthVision) and manual methods.
The introduction describes the background to the project. The second chapter describes the
sources for the data used in the model: published and unpublished geological maps, borehole
records (both lithological and geophysical), seismic surveys, biostratigraphic records, digital
topographic information, and the published literature.
Each Chalk formation present in the area is then briefly described in the third chapter, noting its
relationship to the older lithostratigraphic divisions, and to biostratigraphic zones. The local
Chalk succession extends from the base of the Chalk Group to the Newhaven Chalk Formation,
here represented by the Margate Chalk Member. Evidence for the thickness of each formation is
reviewed.
The early Palaeogene formations (the Thanet Sand, Upnor, Harwich and London Clay
formations) are also briefly described (Chapter 4) and the local superficial deposits mentioned,
with references to detailed descriptions (Chapter 5). Apart from minor adjustments to the outcrop
of the basal Palaeogene surface, no revision of these formations was done for this study
Making a Move in Exercise Referral: Co-Development of a Physical Activity Referral Scheme
Item does not contain fulltextBackground: Translational research is required to ensure exercise referral schemes (ERSs) are evidence-based and reflect local needs. This article reports process data from the co-development phase of an ERS, providing an insight into (i) factors that must be considered when translating evidence to practice in an ERS setting, and (ii) challenges and facilitators of conducting participatory research involving multiple stakeholders. Methods: An ERS was iteratively co-developed by a multidisciplinary stakeholder group (commissioners, managers, practitioners, patients and academics) via five participatory meetings and an online survey. Audio data (e.g. group discussions) and visual data (e.g. whiteboard notes) were recorded and analysed using NVivo-10 electronic software. Results: Factors to consider when translating evidence to practice in an ERS setting included (i) current ERS culture; (ii) skills, safety and accountability; and (iii) resources and capacity. The co-development process was facilitated by needs-analysis, open questions, multidisciplinary debate and reflective practice. Challenges included contrasting views, irregular attendance and (mis)perceptions of evaluation. Conclusion: The multidisciplinary co-development process highlighted cultural and pragmatic issues related to exercise referral provision, resulting in an evidence-based intervention framework designed to be implemented within existing infrastructures. Further work is required to establish the feasibility and effectiveness of the co-developed intervention in practice
Testing the Gaussian expansion method in exactly solvable matrix models
The Gaussian expansion has been developed since early 80s as a powerful
analytical method, which enables nonperturbative studies of various systems
using `perturbative' calculations. Recently the method has been used to suggest
that 4d space-time is generated dynamically in a matrix model formulation of
superstring theory. Here we clarify the nature of the method by applying it to
exactly solvable one-matrix models with various kinds of potential including
the ones unbounded from below and of the double-well type. We also formulate a
prescription to include a linear term in the Gaussian action in a way
consistent with the loop expansion, and test it in some concrete examples. We
discuss a case where we obtain two distinct plateaus in the parameter space of
the Gaussian action, corresponding to different large-N solutions. This
clarifies the situation encountered in the dynamical determination of the
space-time dimensionality in the previous works.Comment: 30 pages, 15 figures, LaTeX; added references for section
Higher Order Evaluation of the Critical Temperature for Interacting Homogeneous Dilute Bose Gases
We use the nonperturbative linear \delta expansion method to evaluate
analytically the coefficients c_1 and c_2^{\prime \prime} which appear in the
expansion for the transition temperature for a dilute, homogeneous, three
dimensional Bose gas given by T_c= T_0 \{1 + c_1 a n^{1/3} + [ c_2^{\prime}
\ln(a n^{1/3}) +c_2^{\prime \prime} ] a^2 n^{2/3} + {\cal O} (a^3 n)\}, where
T_0 is the result for an ideal gas, a is the s-wave scattering length and n is
the number density. In a previous work the same method has been used to
evaluate c_1 to order-\delta^2 with the result c_1= 3.06. Here, we push the
calculation to the next two orders obtaining c_1=2.45 at order-\delta^3 and
c_1=1.48 at order-\delta^4. Analysing the topology of the graphs involved we
discuss how our results relate to other nonperturbative analytical methods such
as the self-consistent resummation and the 1/N approximations. At the same
orders we obtain c_2^{\prime\prime}=101.4, c_2^{\prime \prime}=98.2 and
c_2^{\prime \prime}=82.9. Our analytical results seem to support the recent
Monte Carlo estimates c_1=1.32 \pm 0.02 and c_2^{\prime \prime}= 75.7 \pm 0.4.Comment: 29 pages, 3 eps figures. Minor changes, one reference added. Version
in press Physical Review A (2002
Large N_c, chiral approach to M_eta' at finite temperature
We study the temperature dependence of the eta and eta' meson masses within
the framework of U(3)_L x U(3)_R chiral perturbation theory, up to
next-to-leading order in a simultaneous expansion in momenta, quark masses and
number of colours. We find that both masses decrease at low temperatures, but
only very slightly. We analyze higher order corrections and argue that large
N_c suggests a discontinuous drop of M_eta' at the critical temperature of
deconfinement T_c, consistent with a first order transition to a phase with
approximate U(1)_A symmetry.Comment: 21 pages, 6 figures. 2 footnotes added, 1 reference changed and 1
typo corrected. To be published in Phys. Rev.
Asymptotically Improved Convergence of Optimized Perturbation Theory in the Bose-Einstein Condensation Problem
We investigate the convergence properties of optimized perturbation theory,
or linear expansion (LDE), within the context of finite temperature
phase transitions. Our results prove the reliability of these methods, recently
employed in the determination of the critical temperature T_c for a system of
weakly interacting homogeneous dilute Bose gas. We carry out the explicit LDE
optimized calculations and also the infrared analysis of the relevant
quantities involved in the determination of in the large-N limit, when
the relevant effective static action describing the system is extended to O(N)
symmetry. Then, using an efficient resummation method, we show how the LDE can
exactly reproduce the known large-N result for already at the first
non-trivial order. Next, we consider the finite N=2 case where, using similar
resummation techniques, we improve the analytical results for the
nonperturbative terms involved in the expression for the critical temperature
allowing comparison with recent Monte Carlo estimates of them. To illustrate
the method we have considered a simple geometric series showing how the
procedure as a whole works consistently in a general case.Comment: 38 pages, 3 eps figures, Revtex4. Final version in press Phys. Rev.
Family stories, public silence: Irish identity construction amongst the second-generation Irish in England
Formal narratives of history, especially that of colonial oppression, have been central to the construction of national identities in Ireland. But the Irish diasporic community in Britain has been cut off from the reproduction of these narratives, most notably by their absence from the curriculum of Catholic schools, as result of the unofficial 'denationalisation' pact agreed by the Church in the 19th century (Hickman, 1995). The reproduction of Irish identities is largely a private matter, carried out within the home through family accounts of local connections, often reinforced by extended visits to parent/s 'home' areas. Recapturing a public dimension has often become a personal quest in adulthood, 'filling in the gaps'. This paper explores constructions of narratives of nation by a key diasporic population, those with one or two Irish-born parents. It places particular emphasis on varying regional/national contexts within which such constructions take place, drawing on focus group discussions and interviews for the ESRC-funded Irish 2 Project in five locations â London, Glasgow, Manchester, Coventry and Banbury
Extended search for the invisible axion with the axion dark matter experiment
This Letter reports on a cavity haloscope search for dark matter axions in the Galactic halo in the mass range 2.81â3.31ÎŒeV. This search utilizes the combination of a low-noise Josephson parametric amplifier and a large-cavity haloscope to achieve unprecedented sensitivity across this mass range. This search excludes the full range of axion-photon coupling values predicted in benchmark models of the invisible axion that solve the strong CP problem of quantum chromodynamics
Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment
This paper describes an analysis of the angular distribution of W->enu and
W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with
the ATLAS detector at the LHC in 2010, corresponding to an integrated
luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and
the missing transverse energy, the W decay angular distribution projected onto
the transverse plane is obtained and analysed in terms of helicity fractions
f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV
and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw
> 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour,
are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017
+/- 0.030, where the first uncertainties are statistical, and the second
include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables,
revised author list, matches European Journal of Physics C versio
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