132 research outputs found
Quantum Aspects of the Noncommutative Sine-Gordon Model
In this paper, we first use semi-classical methods to study quantum field
theoretical aspects of the integrable noncommutative sine-Gordon model proposed
in [hep-th/0406065]. In particular, we examine the fluctuations at quadratic
order around the static kink solution using the background field method. We
derive equations of motion for the fluctuations and argue that at O(theta^2)
the spectrum of fluctuations remains essentially the same as that of the
corresponding commutative theory. We compute the one-loop two-point functions
of the sine-Gordon field and the additional scalar field present in the model
and exhibit logarithmic divergences, only some of which lead to UV/IR mixing.
We briefly discuss the one-loop renormalization in Euclidean signature and
comment on the obstacles in determining the noncommutativity corrections to the
quantum mass of the kink.Comment: 1+14 pages, 8 eps figures, Added references, Version to appear in
JHE
Nonlocal regularisation of noncommutative field theories
We study noncommutative field theories, which are inherently nonlocal, using
a Poincar\'e-invariant regularisation scheme which yields an effective,
nonlocal theory for energies below a cut-off scale. After discussing the
general features and the peculiar advantages of this regularisation scheme for
theories defined in noncommutative spaces, we focus our attention onto the
particular case when the noncommutativity parameter is inversely proportional
to the square of the cut-off, via a dimensionless parameter . We work out
the perturbative corrections at one-loop order for a scalar theory with quartic
interactions, where the signature of noncommutativity appears in
-dependent terms. The implications of this approach, which avoids the
problems related to UV-IR mixing, are discussed from the perspective of the
Wilson renormalisation program. Finally, we remark about the generality of the
method, arguing that it may lead to phenomenologically relevant predictions,
when applied to realistic field theories.Comment: 1+11 pages, 6 figures; v2: references added, typos corrected,
conclusions unchange
Edge Currents in Non-commutative Chern-Simons Theory from a New Matrix Model
This paper discusses the formulation of the non-commutative Chern-Simons (CS)
theory where the spatial slice, an infinite strip, is a manifold with
boundaries. As standard star products are not correct for such manifolds, the
standard non-commutative CS theory is not also appropriate here. Instead we
formulate a new finite-dimensional matrix CS model as an approximation to the
CS theory on the strip. A work which has points of contact with ours is due to
Lizzi, Vitale and Zampini where the authors obtain a description for the fuzzy
disc. The gauge fields in our approach are operators supported on a subspace of
finite dimension N+\eta of the Hilbert space of eigenstates of a simple
harmonic oscillator with N, \eta \in Z^+ and N \neq 0. This oscillator is
associated with the underlying Moyal plane. The resultant matrix CS theory has
a fuzzy edge. It becomes the required sharp edge when N and \eta goes to
infinity in a suitable sense. The non-commutative CS theory on the strip is
defined by this limiting procedure. After performing the canonical constraint
analysis of the matrix theory, we find that there are edge observables in the
theory generating a Lie algebra with properties similar to that of a
non-abelian Kac-Moody algebra. Our study shows that there are (\eta+1)^2
abelian charges (observables) given by the matrix elements (\cal A_i)_{N-1 N-1}
and (\cal A_i)_{nm} (where n or m \geq N) of the gauge fields, that obey
certain standard canonical commutation relations. In addition, the theory
contains three unique non-abelian charges, localized near the N^th level. We
show that all non-abelian edge observables except these three can be
constructed from the abelian charges above. Using the results of this analysis
we discuss the large N and \eta limit.Comment: LaTeX, 16 pages and 2 figures. Comments added in sections 4 and 5. A
minor error corrected in section 4. Figures replaced for clarity. Typos
correcte
Influence of a vegetable fat blend on the texture, microstructure and sensory properties of kashar cheese
Human papillomavirus (HPV) prevalence and types among Turkish women at a gynecology outpatient unit
The Star Product on the Fuzzy Supersphere
The fuzzy supersphere is a finite-dimensional matrix
approximation to the supersphere incorporating supersymmetry
exactly. Here the star-product of functions on is obtained by
utilizing the OSp(2,1) coherent states. We check its graded commutative limit
to and extend it to fuzzy versions of sections of bundles using the
methods of [1]. A brief discussion of the geometric structure of our
star-product completes our work.Comment: 21 pages, LaTeX, new material added, minor errors correcte
Cumulative incidence and risk factors for cutaneous squamous-cell carcinoma metastases in organ transplant recipients: the SCOPE-ITSCC metastases study, a prospective multi-center study.
Solid organ transplant recipients (SOTRs) are believed to have an increased risk of metastatic cutaneous squamous-cell carcinoma (cSCC), but reliable data are lacking regarding the precise incidence and associated risk factors. In a prospective cohort study, including 19 specialist dermatology outpatient clinics in 15 countries, patient and tumor characteristics were collected using standardized questionnaires when SOTRs presented with a new cSCC. After a minimum of 2 years of follow-up, relevant data for all SOTRs were collected. Cumulative incidence of metastases was calculated by the Aalen-Johansen estimator. Fine and Gray models were used to assess multiple risk factors for metastases. Of 514 SOTRs who presented with 623 primary cSCCs, 37 developed metastases with a 2-year patient-based cumulative incidence of 6.2%. Risk factors for metastases included location in the head and neck area, local recurrence, size >2cm, clinical ulceration, poor differentiation grade, perineural invasion and deep invasion. A high-stage tumor that is also ulcerated showed the highest risk of metastasis, with a 2-year cumulative incidence of 46.2% (31.9% - 68.4%). SOTRs have a high risk of cSCC metastases and well-established clinical and histological risk factors have been confirmed. High-stage, ulcerated cSCCs have the highest risk of metastasis. [Abstract copyright: Copyright © 2024. Published by Elsevier Inc.
The effectiveness of a multidisciplinary intervention strategy for the treatment of symptomatic joint hypermobility in childhood:A randomised, single Centre parallel group trial (The Bendy Study)
Introduction: Joint hypermobility is common in childhood and can be associated with musculoskeletal pain and dysfunction. Current management is delivered by a multidisciplinary team, but evidence of effectiveness is limited. This clinical trial aimed to determine whether a structured multidisciplinary, multisite intervention resulted in improved clinical outcomes compared with standard care. Method: A prospective randomised, single centre parallel group trial comparing an 8-week individualised multidisciplinary intervention programme (bespoke physiotherapy and occupational therapy in the clinical, home and school environment) with current standard management (advice, information and therapy referral if deemed necessary). The primary endpoint of the study was between group difference in child reported pain from baseline to 12 months as assessed using the Wong Baker faces pain scale. Secondary endpoints were parent reported pain (100 mm visual analogue scale), parent reported function (child health assessment questionnaire), child reported quality of life (child health utility 9-dimensional assessment), coordination (movement assessment battery for children version 2) and grip strength (handheld dynamometer). Results: 119 children aged 5 to 16 years, with symptomatic hypermobility were randomised to receive an individualised multidisciplinary intervention (I) (n = 59) or standard management (S) (n = 60). Of these, 105 completed follow up at 12 months. No additional significant benefit could be shown from the intervention compared to standard management. However, there was a statistically significant improvement in child and parent reported pain, coordination and grip strength in both groups. The response was independent of the degree of hypermobility. Conclusion: This is the first randomised controlled trial to compare a structured multidisciplinary, multisite intervention with standard care in symptomatic childhood hypermobility. For the majority, the provision of education and positive interventions aimed at promoting healthy exercise and self-management was associated with significant benefit without the need for more complex interventions. Trial registration: The trial was registered prospectively with the national database at the Clinical Research Network (UKCRN Portfolio 9366). The trial was registered retrospectively with ISRCTN (ISRCTN86573140)
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