4,515 research outputs found
Local supersymmetry without SUSY partners
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 , a
spin-1/2 Dirac spinor , the Lorentz connection , and the vielbein
. The connection one-form is in the adjoint representation of G, while
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
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 . 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 -dimensional planar reduced QED.Comment: New section added, published versio
Effect of the Gribov horizon on the Polyakov loop and vice versa
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
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
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
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.
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
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
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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