2,087 research outputs found
Seiberg Witten Map and the Axial Anomaly in Noncommutative Field Theory
Using the point-splitting regularisation, we calculate the axial anomaly in
an arbitrary even dimensional Non-Commutative (NC) field theory. Our result is
(star) gauge invariant in its {\it unintegrated} form, to the leading order in
the NC parameter.
Exploiting the Seiberg Witten map, this result gets transformed to the
familiar Adler-Bell-Jackiw anomaly in ordinary space-time. Furthermore, using
this map, we derive an expression for the unintegrated axial anomaly for
constant fields in NC space-time, that is valid to all finite orders of the NC
parameter.Comment: Slightly modified version with minor changes in the reference, Jour.
ref: Phys. Lett. B533 (2002) 16
Virasoro Symmetry of Constrained KP Hierarchies
Additional non-isospectral symmetries are formulated for the constrained
Kadomtsev-Petviashvili (\cKP) integrable hierarchies. The problem of
compatibility of additional symmetries with the underlying constraints is
solved explicitly for the Virasoro part of the additional symmetry through
appropriate modification of the standard additional-symmetry flows for the
general (unconstrained) KP hierarchy. We also discuss the special case of \cKP
--truncated KP hierarchies, obtained as Darboux-B\"{a}cklund orbits of initial
purely differential Lax operators. The latter give rise to Toda-lattice-like
structures relevant for discrete (multi-)matrix models. Our construction
establishes the condition for commutativity of the additional-symmetry flows
with the discrete Darboux-B\"{a}cklund transformations of \cKP hierarchies
leading to a new derivation of the string-equation constraint in matrix models.Comment: LaTeX, 11 pg
The Value of Information Technology-Enabled Diabetes Management
Reviews different technologies used in diabetes disease management, as well as the costs, benefits, and quality implications of technology-enabled diabetes management programs in the United States
Covered self-expandable metal stents for pancreatic duct stricture: a systematic review and meta-analysis
Background and study aims Placement of a covered (C)-self-expandable metal stent (SEMS) has been recently investigated as an alternative endoscopic treatment for main pancreatic duct stricture (MPDS) in chronic pancreatitis. Our aim was to carry out a systematic review and meta-analysis of studies quantifying efficacy and safety of C-SEMSs in the management of MPDS.Methods A multiple database search was performed, including MEDLINE, Embase and Cochrane Library, from January 2000 to September 2020, to identify studies reporting the efficacy and safety of C-SEMSs in patients with MPDS. Stricture and pain resolution were investigated. Other outcomes included technical success, stent migration, stricture recurrence and need for repeated stent placement. Pancreatitis, severe abdominal pain requiring stent removal and de-novo stricture were recorded as complications.Results Nineteen studies were identified, which included a total of 300 patients. C-SEMSs showed a pooled stricture resolution rate of 91 % [95 % confidence interval (CI), 85 %-96 %] and a pooled pain resolution rate of 92 % (95 % CI, 85 %-98 %). The pooled proportion for stricture recurrence was equal to 6 % (95 % CI, 1 %-14 %), while stent migration occurred in 33 of 300 patients, the pooled proportion being 7 % (95 % CI 1 %-15 %). The pooled mean stent duration was 133 days (95 % CI, 100-166 days). The most common complication was pancreatitis (3 %, 95 % CI 0 %-8 %), while de-novo stricture pooled proportion was 2 % (95 % CI, 0 %-5 %).Conclusions C-SEMSs are effective and safe in the treatment of MPDS. However, there is a significant need for further high-quality, well-designed studies to produce evidence-based data on short and long-term efficacy, safety, costs of C-SEMSs, and also optimal stent duration
Construction of KP Hierarchies in Terms of Finite Number of Fields and their Abelianization
The -boson representations of KP hierarchy are constructed in terms of
mutually independent two-boson KP representations for arbitrary number .
Our construction establishes the multi-boson representations of KP hierarchy as
consistent Poisson reductions of standard KP hierarchy within the -matrix
scheme. As a byproduct we obtain a complete description of any
finitely-many-field formulation of KP hierarchy in terms of Darboux coordinates
with respect to the first Hamiltonian structure. This results in a series of
representations of \Win1\, algebra made out of arbitrary even number of boson
fields.Comment: 12 p., LaTeX, minor typos corrected, BGU-93/2/June-P
General methods for constructing bispectral operators
We present methods for obtaining new solutions to the bispectral problem. We
achieve this by giving its abstract algebraic version suitable for
generalizations. All methods are illustrated by new classes of bispectral
operators.Comment: 11 pages, LaTeX2e, uses amsfonts.sty and latexsym.sty, no figure
Higher Dimensional Classical W-Algebras
Classical -algebras in higher dimensions are constructed. This is achieved
by generalizing the classical Gel'fand-Dickey brackets to the commutative limit
of the ring of classical pseudodifferential operators in arbitrary dimension.
These -algebras are the Poisson structures associated with a higher
dimensional version of the Khokhlov-Zabolotskaya hierarchy (dispersionless
KP-hierarchy). The two dimensional case is worked out explicitly and it is
shown that the role of Diff is taken by the algebra of generators of
local diffeomorphisms in two dimensions.Comment: 22 pages, Plain TeX, KUL-TF-92/19, US-FT/6-9
Assessing the level of spatial homogeneity of the agronomic Indian monsoon onset
Over monsoon regions, such as the Indian subcontinent, the local onset of persistent rainfall is a crucial event in the annual climate for agricultural planning. Recent work suggested that local onset dates are spatially coherent to a practical level over West Africa; a similar assessment is undertaken here for the Indian subcontinent. Areas of coherent onset, defined as local onset regions or LORs, exist over the studied region. These LORs are significant up to the 95% confidence interval and are primarily clustered around the Arabian Sea (adjacent to and extending over the Western Ghats), the Monsoon Trough (north central India), and the Bay of Bengal. These LORs capture regions where synoptic scale controls of onset may be present and identifiable. In other regions, the absence of LORs is indicative of regions where local and stochastic factors may dominate onset. A potential link between sea surface temperature anomalies and LOR variability is presented. Finally, Kerala, which is often used as a representative onset location, is not contained within an LOR suggesting that variability here may not be representative of wider onset variability
Minimal Length Uncertainty Relation and the Hydrogen Spectrum
Modifications of Heisenberg's uncertainty relations have been proposed in the
literature which imply a minimum position uncertainty. We study the low energy
effects of the new physics responsible for this by examining the consequent
change in the quantum mechanical commutation relations involving position and
momenta. In particular, the modifications to the spectrum of the hydrogen atom
can be naturally interpreted as a varying (with energy) fine structure
constant. From the data on the energy levels we attempt to constrain the scale
of the new physics and find that it must be close to or larger than the weak
scale. Experiments in the near future are expected to change this bound by at
least an additional order of magnitude.Comment: 8 pages, no figure. Corrected typos, added a reference with comment
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