4,515 research outputs found

    Local supersymmetry without SUSY partners

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    A gauge theory for a superalgebra that includes an internal gauge (G) and local Lorentz algebras, and that could describe the low energy particle phenomenology is constructed. These two symmetries are connected by fermionic supercharges. The system includes an internal gauge connection 1-form AA, a spin-1/2 Dirac spinor ψ\psi, the Lorentz connection ω\omega, and the vielbein ee. The connection one-form is in the adjoint representation of G, while ψ\psi is in the fundamental. In contrast to standard supergravity, the metric is not a fundamental field and is in the center of the superalgebra: it is not only invariant under the internal gauge group and under Lorentz transformations, but is also invariant under supersymmetry. The features of this theory that mark the difference with standard supersymmetry are: A) The number of fermionic and bosonic states is not necessarily the same; B) There are no superpartners with equal mass, "bosoninos", sleptons and squarks are absent; C) Although this supersymmetry originates in a local gauge theory and gravity is included, there is no gravitino; D) Fermions acquire mass from their coupling to the background or from self-couplings, while bosons remain massless. In odd dimensions, the Chern-Simons form provides an action that is quasi-invariant under the entire superalgebra. In even dimensions, the Yang-Mills form is the only natural option, and the symmetry breaks down to [G x SO(1,D-1)]. In 4D, the construction follows the Townsend - Mac Dowell-Mansouri approach. Due to the absence of osp(4|2)-invariant traces in four dimensions, the resulting Lagrangian is only invariant under [U(1) x SO(3,1)], and includes a Nambu--Jona-Lasinio term. In this case, the Lagrangian depends on a single dimensionful parameter that fixes Newton's constant, the cosmological constant and the NJL coupling.Comment: 24 pages, no figures. Title changed in journal version to "Unconventional supersymmetry and its breaking". Few references added and some paragraphs rewritten from v.1. This version includes two appendices that are not found in the journal versio

    Comments on the Chern-Simons photon term in the QED description of graphene

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    We revisit the Coleman-Hill theorem in the context of reduced planar QED. Using the global U(1) Ward identity for this non-local but still gauge invariant theory, we can confirm that the topological piece of the photon self-energy at zero momentum does not receive further quantum corrections apart from the potential one-loop contribution, even when considering the Lorentz non-invariant case due to the Fermi velocity vF<cv_F<c. This is of relevance to probe possible time parity odd dynamics in a planar sheet of graphene which has an effective description in terms of (2+1)(2+1)-dimensional planar reduced QED.Comment: New section added, published versio

    Effect of the Gribov horizon on the Polyakov loop and vice versa

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    We consider finite temperature SU(2) gauge theory in the continuum formulation, which necessitates the choice of a gauge fixing. Choosing the Landau gauge, the existing gauge copies are taken into account by means of the Gribov-Zwanziger (GZ) quantization scheme, which entails the introduction of a dynamical mass scale (Gribov mass) directly influencing the Green functions of the theory. Here, we determine simultaneously the Polyakov loop (vacuum expectation value) and Gribov mass in terms of temperature, by minimizing the vacuum energy w.r.t. the Polyakov loop parameter and solving the Gribov gap equation. Inspired by the Casimir energy-style of computation, we illustrate the usage of Zeta function regularization in finite temperature calculations. Our main result is that the Gribov mass directly feels the deconfinement transition, visible from a cusp occurring at the same temperature where the Polyakov loop becomes nonzero. In this exploratory work we mainly restrict ourselves to the original Gribov-Zwanziger quantization procedure in order to illustrate the approach and the potential direct link between the vacuum structure of the theory (dynamical mass scales) and (de)confinement. We also present a first look at the critical temperature obtained from the Refined Gribov-Zwanziger approach. Finally, a particular problem for the pressure at low temperatures is reported.Comment: 19 pages, 8 .pdf figures. v2: extended section 3 + extra references; version accepted for publication in EPJ

    The BTZ black hole as a Lorentz-flat geometry

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    It is shown that 2+1 dimensional anti-de Sitter spacetimes are Lorentz-flat. This means, in particular, that any simply-connected patch of the BTZ black hole solution can be endowed with a Lorentz connection that is locally pure gauge. The result can be naturally extended to a wider class of black hole geometries and point particles in three-dimensional spacetime.Comment: 2 page

    Double non-perturbative gluon exchange: an update on the soft Pomeron contribution to pp scattering

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    We employ a set of recent, theoretically motivated, fits to non-perturbative unquenched gluon propagators to check in how far double gluon exchange can be used to describe the soft sector of pp scattering data (total and differential cross section). In particular, we use the refined Gribov--Zwanziger gluon propagator (as arising from dealing with the Gribov gauge fixing ambiguity) and the massive Cornwall-type gluon propagator (as motivated from Dyson-Schwinger equations) in conjunction with a perturbative quark-gluon vertex, next to a model based on the non-perturbative quark-gluon Maris-Tandy vertex, popular from Bethe-Salpeter descriptions of hadronic bound states. We compare the cross sections arising from these models with "older" ISR and more recent TOTEM and ATLAS data. The lower the value of total energy \sqrt{s}, the better the results appear to be.Comment: 14 pages, 8 .pdf figures. To appear in Phys.Rev.

    Enhancing system acceptance through user-centred design: Integrating patient generated wellness data

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    Gestational diabetes mellitus (GDM) is a condition that appears during pregnancy and is expected to be a temporary one. While patients are encouraged to manage it themselves, research findings indicate that GDM may negatively affect the foetus; in addition, there is an increased risk of women with GDM subsequently developing Type 2 diabetes. To alleviate the risks, women with GDM are advised to maintain a record of their diet and blood glucose levels and to attend regular clinical reviews. Rather than using a paper diary, women with GDM can maintain a record of their blood glucose level readings and other relevant data using a wellness mobile application (app). However, such apps are developed for general use and may not meet the specific needs of clinical staff (physicians, dietitians, obstetricians and midwives) involved in managing GDM; for example, an app may record glucose readings but not the details of a meal taken before or after the glucose reading. Second, the apps do not permanently store the data generated by the patient and do not support the transfer of these data to a clinical system or information portal. The mobile health (mHealth) system designed and developed in this research allows one to integrate different types of user generated wellness data into a centralised database. A user-centered design (UCD) approach informed by the technology acceptance model (TAM) was adopted. This paper investigates and evaluates the effectiveness of the approach with regard to facilitating system acceptance and future adoption through an early focus on enhancing system usefulness and ease of use. The functional system requirements of the proposed system were refined through a series of interviews with the perspective of clinical users; ease-of-use and usability issues were resolved through ‘think aloud’ sessions with clinicians and GDM patients

    Lentiviral vectors with amplified beta cell-specific gene expression.

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    An important goal of gene therapy is to be able to deliver genes, so that they express in a pattern that recapitulates the expression of an endogenous cellular gene. Although tissue-specific promoters confer selectivity, in a vector-based system, their activity may be too weak to mediate detectable levels in gene-expression studies. We have used a two-step transcriptional amplification system to amplify gene expression from lentiviral vectors using the human insulin promoter. In this system, the human insulin promoter drives expression of a potent synthetic transcription activator (the yeast GAL4 DNA-binding domain fused to the activation domain of the Herpes simplex virus-1 VP16 activator), which in turn activates a GAL4-responsive promoter, driving the enhanced green fluorescent protein reporter gene. Vectors carrying the human insulin promoter did not express in non-beta-cell lines, but expressed in murine insulinoma cell lines, indicating that the human insulin promoter was capable of conferring cell specificity of expression. The insulin-amplifiable vector was able to amplify gene expression five to nine times over a standard insulin-promoter vector. In primary human islets, gene expression from the insulin-promoted vectors was coincident with insulin staining. These vectors will be useful in gene-expression studies that require a detectable signal and tissue specificity

    Patient Safety Culture in Portuguese Primary

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    Introduction: According to the European Commission more than 37 million Primary Healthcare (PHC) users suffer Adverse Events (AE). When we talk about these unintentional and undesirable events, most of the time we are dealing with acts committed by competent and dedicated professionals, who often work in disorganized systems, and who are not very oriented towards patient safety and health care professional safety. The adoption of a safety culture is a proven useful tool to make AE less likely to occur and to minimize its consequences when these inevitably take place. Methods: The authors describe some pertinent issues that have made the evaluation of AE and Patient Safety Culture (PSC) in Portuguese PHC particularly challenging and describe the preliminary results of a project for the assessment of PSC using the Medical Office Survey on Patient Safety Culture (MOSOPSC). This instrument has been translated, adapted and validated by the authors for the study population. Results: Studies about AE in PHC are scarce, but admittedly necessary. Despite the socio-economic instability experienced in Portugal, the preliminary results obtained by the authors promise a proactive PSC with dedicated health professionals, working as a team and recognizing the problem of adverse events in PHC of the Madeira Island. Discussion: The concepts and methodologies used in other studies cannot simply be applied to specific populations. On the Madeira Island (one autonomous region of Portugal), the issue of patient safety (PS) is difficult to approach but, nevertheless, with information and discussion it was possible to measure the PSC in PHC. Conclusion: After some adjustments, the MOSOPSC questionnaire, in addition to assessing safety culture, has helped to initiate the dialogue and discussion on the issue of PS among the various professionals. This approach has allowed these professionals to anticipate and prevent the occurrence of AE and, whenever such is not possible, notify, discuss, share and learn from those same events.info:eu-repo/semantics/publishedVersio

    The burden of serious fungal infections in Portugal

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    Using published data, we were able to estimate the incidence or prevalence of the above referred fungal infections and ~194 293 (1.8%) people in Portugal suffer from those fungal infections each year
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