265 research outputs found
Symmetry transform in the Faddeev-Jackiw quantization of dual models
We study the presence of symmetry transformations in the Faddeev-Jackiw
approach for constrained systems. Our analysis is based in the case of a
particle submitted to a particular potential which depends on an arbitrary
function. The method is implemented in a natural way and symmetry generators
are identified. These symmetries permit us to obtain the absent elements of the
sympletic matrix which complement the set of Dirac brackets of such a theory.
The study developed here is applied in two different dual models. First, we
discuss the case of a two-dimensional oscillator interacting with an
electromagnetic potential described by a Chern-Simons term and second the
Schwarz-Sen gauge theory, in order to obtain the complete set of non-null Dirac
brackets and the correspondent Maxwell electromagnetic theory limit.Comment: 22 pages, RevTex file, no figur
Pasti-Sorokin-Tonin Actions in the Presence of Sources
Pasti, Sorokin and Tonin have recently constructed manifestly
Lorentz-invariant actions for self-dual field strengths and for Maxwell fields
with manifest electromagnetic duality. Using the method of Deser, Gomberoff,
Henneaux and Teitelboim, we generalize these actions in the presence of
sources.Comment: 6 pages, LaTe
New remarks on the linear constraint self-dual boson and Wess-Zumino terms
In this work we prove in a precise way that the soldering formalism can be
applied to the Srivastava chiral boson (SCB), in contradiction with some
results appearing in the literature. We have promoted a canonical
transformation that shows directly that the SCB is composed of two
Floreanini-Jackiw's particles with the same chirality which spectrum is a
vacuum-like one. As another conflictive result we have proved that a
Wess-Zumino term used in the literature consists of the scalar field, once
again denying the assertion that the WZ term adds a new degree of freedom to
the SCB theory in order to modify the physics of the system.Comment: 6 pages, Revtex. Final version to appear in Physical Review
Duality in a fermion-like formulation for the electromagnetic field
We employ the Dirac-like equation for the gauge field proposed by Majorana to
obtain an action that is symmetric under duality transformation. We also use
the equivalence between duality and chiral symmetry in this fermion-like
formulation to show how the Maxwell action can be seen as a mass term.Comment: 4 pages. Revtex. Final version to be published in Phys. Rev.
Hamiltonian Quantization of Effective Lagrangians with Massive Vector Fields
Effective Lagrangians containing arbitrary interactions of massive vector
fields are quantized within the Hamiltonian path integral formalism. It is
proven that correct Hamiltonian quantization of these models yields the same
result as naive Lagrangian quantization (Matthews's theorem). This theorem
holds for models without gauge freedom as well as for (linearly or nonlinearly
realized) spontaneously broken gauge theories. The Stueckelberg formalism, a
procedure to rewrite effective Lagrangians in a gauge invariant way, is
reformulated within the Hamiltonian formalism as a transition from a second
class constrained theory to an equivalent first class constrained theory. The
relations between linearly and nonlinearly realized spontaneously broken gauge
theories are discussed. The quartically divergent Higgs self interaction is
derived from the Hamiltonian path integral.Comment: 16 pages LaTeX, BI-TP 93/1
Frequency and phenotypic spectrum of KMT2B dystonia in childhood: A singleâcenter cohort study
Background: Childhood-onset dystonia is often genetically determined. Recently, KMT2B variants have been recognized as an important cause of childhood-onset dystonia.
Objective: To define the frequency of KMT2B mutations in a cohort of dystonic patients aged less than 18 years at onset, the associated clinical and radiological phenotype, and the natural history of disease.
Methods: Whole-exome sequencing or customized gene panels were used to screen a cohort of sixty-five patients who had previously tested negative for all other known dystonia-associated genes.
Results: We identified fourteen patients (21.5%) carrying KMT2B variants, of which one was classified as a Variant of Unknown Significance (VUS). We also identified two additional patients carrying pathogenic mutations in GNAO1 and ATM. Overall, we established a definitive genetic diagnosis in 23% of cases. We observed a spectrum of clinical manifestations in KMT2B variant carriers, ranging from generalized dystonia to short stature or intellectual disability alone, even within the same family. In 78.5% of cases, dystonia involved the lower limbs at onset, with later caudo-cranial generalization. Eight patients underwent pallidal Deep Brain Stimulation with a median decrease of BFMDRS-M score of 38.5% in the long term. We also report four asymptomatic carriers, suggesting that some KMT2B mutations may be associated with incomplete disease penetrance.
Conclusions: KMT2B mutations are frequent in childhood-onset dystonia and cause a complex neurodevelopmental syndrome often featuring growth retardation and intellectual disability as additional phenotypic features. A dramatic and long-lasting response to Deep Brain Stimulation is characteristic of DYT-KMT2B dystonia
Hamiltonian embedding of the massive noncommutative U(1) theory
We show that the massive noncommutative U(1) can be embedded in a gauge
theory by using the BFFT Hamiltonian formalism. By virtue of the peculiar
non-Abelian algebraic structure of the noncommutative massive U(1) theory,
several specific identities involving Moyal commutators had to be used in order
to make the embedding possible. This leads to an infinite number of steps in
the iterative process of obtaining first-class constraints. We also shown that
the involutive Hamiltonian can be constructed.Comment: 8 pages, Revtex (multicol
Radiative corrections to the Chern-Simons term at finite temperature in the noncommutative Chern-Simons-Higgs model
By analyzing the odd parity part of the gauge field two and three point
vertex functions, the one-loop radiative correction to the Chern-Simons
coefficient is computed in noncommutative Chern-Simons-Higgs model at zero and
at high temperature. At high temperature, we show that the static limit of this
correction is proportional to but the first noncommutative correction
increases as . Our results are analytic functions of the
noncommutative parameter.Comment: Revised version with a new section on the gauge field three point
vertex function adde
"It's making contacts" : notions of social capital and implications for widening access to medical education
Acknowledgements Our thanks to the Medical Schools Council (MSC) of the UK for funding Study A; REACH Scotland for funding Study B; and Queen Mary University of London, and to the medical school applicants and students who gave their time to be interviewed. Our thanks also to Dr Sean Zhou and Dr Sally Curtis, and Manjul Medhi, for their help with data collection for studies A and B respectively. Our thanks also to Dr Lara Varpio, Uniformed Services University of the USA, for her advice and guidance on collating data sets and her comments on the draft manuscript.Peer reviewedPublisher PD
Effective Potential and Spontaneous Symmetry Breaking in the Noncommutative phi^6 Model
We study the conditions for spontaneous symmetry breaking of the
(2+1)-dimensional noncommutative phi^6 model in the small-theta limit. In this
regime, considering the model as a cutoff theory, it is reasonable to assume
translational invariance as a property of the vacuum state and study the
conditions for spontaneous symmetry breaking by an effective potential
analysis. An investigation of up to the two loop level reveals that
noncommutative effects can modify drastically the shape of the effective
potential. Under reasonable conditions, the nonplanar sector of the theory can
become dominant and induce symmetry breaking for values of the mass and
coupling constants not reached by the commutative counterpart.Comment: 11 pages, 2 figures, corrected to match with the PRD versio
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