59,871 research outputs found
Quantum black holes in Type-IIA String Theory
We study black hole solutions of Type-IIA Calabi-Yau compactifications in the
presence of perturbative quantum corrections. We define a class of black holes
that only exist in the presence of quantum corrections and that, consequently,
can be considered as purely quantum black holes. The regularity conditions of
the solutions impose the topological constraint h^{1,1}>h^{2,1} on the
Calabi-Yau manifold, defining a class of admissible compactifications, which we
prove to be non-empty for h^{1,1}=3 by explicitly constructing the
corresponding Calabi-Yau manifolds, new in the literature.Comment: 17 pages. References added. Explanation of the truncation improve
Precision Charmonium Spectroscopy From Lattice QCD
We present results for Charmonium spectroscopy using Non-Relativistic QCD
(NRQCD). For the NRQCD action the leading order spin-dependent and next to
leading order spin-independent interactions have been included with
tadpole-improved coefficients. We use multi-exponential fits to multiple
correlation functions to extract ground and excited states. Splittings
between the lowest , and states are given and we have accurate
values for the state hyperfine splitting and the fine structure.
Agreement with experiment is good - the remaining systematic errors are
discussed.Comment: 23 pages uuencoded latex file. Contains figures in late
Gravitational Entropy and Quantum Cosmology
We investigate the evolution of different measures of ``Gravitational
Entropy'' in Bianchi type I and Lema\^itre-Tolman universe models.
A new quantity behaving in accordance with the second law of thermodynamics
is introduced. We then go on and investigate whether a quantum calculation of
initial conditions for the universe based upon the Wheeler-DeWitt equation
supports Penrose's Weyl Curvature Conjecture, according to which the Ricci part
of the curvature dominates over the Weyl part at the initial singularity of the
universe. The theory is applied to the Bianchi type I universe models with dust
and a cosmological constant and to the Lema\^itre-Tolman universe models. We
investigate two different versions of the conjecture. First we investigate a
local version which fails to support the conjecture. Thereafter we construct a
non-local entity which shows more promising behaviour concerning the
conjecture.Comment: 20 pages, 7 ps figure
Knowledge tree: Putting discourse into computerâbased learning
Most CBL materials currently in use model only the declarative aspects of the learning process. If such courseware is used without careful planning, this can be dangerous because one of the most fundamental aspects of education is the dialogue that occurs between teachers and the students. Traditionally, this has taken place in informal discussions as well as in formal smallâgroup learning sessions such as the conventional tutorial. However, as the studentâstaff ratio increases, so does the opportunity for this type of personal dialogue decrease. Modern networking technology offers a huge potential to add discourse to CBL, but there are many pedagogical problems involved with the intrinsically ephemeral and anarchic nature both of the Internet and of most conferencing or bulletinâboard systems. In this paper we describe a software system called Knowledge Tree (KT) which we have developed to address some of these issues. KT combines a hierarchical conceptâoriented database functionality with that of a Usenetâstyle bulletin board Using this, a knowledge garden may be developed for any subject area. These each contain a hypermedia database of frequently asked questions, together with answers provided by subject experts. There is provision for interâstudent discussions of problems and issues. When students ask new questions these are automatically emailed to a relevant subject expert (determined by a subjectâspecific concept thesaurus). The answer is then placed in the database which eventually grows to become a valuable teaching resource. KT is disciplineâindependent as the concept thesaurus can be changed to encapsulate any domain of knowledge. We have used it in support of conventional lecture courses, as an important component of a multimedia course, and for general IT support. These examples illustrate the role that this system can play both in basic information provision, and in facilitating the discussion of deep issues
B Physics with NRQCD: A Quenched Study
We present results on the spectrum of B mesons and heavy baryons, using a
non-relativistic formulation for the heavy and a clover action for the light
quark. We also discuss B meson decay constants and their dependency upon the
heavy meson mass.Comment: 4 pages, uuencoded compressed postscript file, contribution to
LATTICE 9
The Energy-Momentum Tensor in Fulling-Rindler Vacuum
The energy density in Fulling-Rindler vacuum, which is known to be negative
"everywhere" is shown to be positive and singular on the horizons in such a
fashion as to guarantee the positivity of the total energy. The mechanism of
compensation is displayed in detail.Comment: 9 pages, ULB-TH-15/9
Consistent analysis of neutral- and charged-current neutrino scattering off carbon
Background: Good understanding of the cross sections for (anti)neutrino
scattering off nuclear targets in the few-GeV energy region is a prerequisite
for correct interpretation of results of ongoing and planned oscillation
experiments.
Purpose: Clarify possible source of disagreement between recent measurements
of the cross sections on carbon.
Method: Nuclear effects in (anti)neutrino scattering off carbon nucleus are
described using the spectral function approach. The effect of two- and
multi-nucleon final states is accounted for by applying an effective value of
the axial mass, fixed to 1.23 GeV. Neutral-current elastic (NCE) and
charged-current quasielastic (CCQE) processes are treated on equal footing.
Results: The differential and total cross sections for the energy ranging
from a few hundreds of MeV to 100 GeV are obtained and compared to the
available data from the BNL E734, MiniBooNE, and NOMAD experiments.
Conclusions: Nuclear effects in NCE and CCQE scattering seem to be very
similar. Within the spectral function approach, the axial mass from the shape
analysis of the MiniBooNE data is in good agreement with the results reported
by the BNL E734 and NOMAD Collaborations. However, the combined analysis of NCE
and CCQE data does not seem to support the contribution of multi-nucleon final
states being large enough to explain the normalization of the
MiniBooNE-reported cross sections.Comment: 14 pages, 9 figures, detailed discussion of the role of FSI is adde
Guidelines for the management of the foot health problems associated with rheumatoid arthritis
Background. Rheumatoid arthritis (RA) as a chronic systemic disease, commonly affects the feet, impacting
negatively on patients' quality of life. Specialist podiatrists have a prime role to play in the assessment and
management of foot and ankle problems within this patient group. However, it has been identified that in many
areas there is no specialist podiatry service, with many patients being managed by nonâspecialist podiatrists.
Therefore, the North West Clinical Effectiveness Group for the Foot in Rheumatic Diseases (NWCEG) identified
the need to develop âpractitioner facingâ guidelines for the management of specific foot health problems associated
with RA.
Methods. Members of a guideline development group from the NWCEG each reviewed the evidence for specific
aspects of the assessment and management of foot problems. Where evidence was lacking, âexpert opinionâ was
obtained from the members of the NWCEG and added as a consensus on current and best practice. An iterative
approach was employed, with the results being reviewed and revised by all members of the group and external
reviewers before the final guideline document was produced.
Results. The management of specific foot problems (callus, nail pathology, ulceration) and the use of specific
interventions (foot orthoses, footwear, patient education, steroid injection therapy) are detailed and standards in
relation to each are provided. A diagrammatic screening pathway is presented, with the aim of guiding nonspecialist
podiatrists through the complexity of assessing and managing those patients with problems requiring
input from a specialist podiatrist and other members of the rheumatology multidisciplinary team.
Conclusion. This pragmatic approach ensured that the guidelines were relevant and applicable to current practice
as âbest practiceâ, based on the available evidence from the literature and consensus expert opinion. These
guidelines provide both specialist and nonâspecialist podiatrists with the essential and âgold standardâ aspects of
managing people with RAârelated foot problems
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