225 research outputs found
Falsifying Tree Level String Motivated Bouncing Cosmologies
The string effective action at tree level contains, in its bosonic sector,
the Einstein-Hilbert term, the dilaton, and the axion, besides scalar and gauge
fields coming from the Ramond-Ramond sector. The reduction to four dimensions
brings to scene moduli fields. We generalize this effective action by
introducing two arbitrary parameters, and , connected with the
dilaton and axion couplings. In this way, more general frameworks can be
analyzed. Regular solutions with a bounce can be obtained for a range of
(negative) values of the parameter which, however, exclude the pure
string configuration (). We study the evolution of scalar
perturbations in such cosmological scenarios. The predicted primordial power
spectrum decreases with the wavenumber with spectral index , in
contradiction with the results of the . Hence, all such effective string
motivated cosmological bouncing models seem to be ruled out, at least at the
tree level approximation.Comment: Latex file, 19 pages, 3 figures in eps forma
On anomalies in classical dynamical systems
The definition of "classical anomaly" is introduced. It describes the
situation in which a purely classical dynamical system which presents both a
lagrangian and a hamiltonian formulation admits symmetries of the action for
which the Noether conserved charges, endorsed with the Poisson bracket
structure, close an algebra which is just the centrally extended version of the
original symmetry algebra. The consistency conditions for this to occur are
derived. Explicit examples are given based on simple two-dimensional models.
Applications of the above scheme and lines of further investigations are
suggested.Comment: arXiv version is already officia
Does Quantum Cosmology Predict a Constant Dilatonic Field?
Quantum cosmology may permit to determine the initial conditions of the
Universe. In particular, it may select a specific model between many possible
classical models. In this work, we study a quantum cosmological model based on
the string effective action coupled to matter. The Schutz's formalism is
employed in the description of the fluid. A radiation fluid is considered. In
this way, a time coordinate may be identified and the Wheeler-DeWitt equation
reduces in the minisuperspace to a Schr\"odinger-like equation. It is shown
that, under some quite natural assumptions, the expectation values indicate a
null axionic field and a constant dilatonic field. At the same time the scale
factor exhibits a bounce revealing a singularity-free cosmological model. In
some cases, the mininum value of the scale factor can be related to the value
of gravitational coupling.Comment: Latex file, 14 page
âTogether ⊠for only a momentâ British newspaper constructions of altruistic non-commercial surrogate motherhood
Objectives: To explore how national altruistic surrogacy is framed in a representative selection of the British press.
Methods: A study of 90 British national newspaper articles was carried out using the Lexis-Nexis data base to search for articles on altruistic surrogacy. Content analysis of gain, loss, neutral frames and high or low alarm and vulnerability frames in the titles and the body of the text was carried out. The type of construction used in the article content was also analysed. Data were coded and consensus reached using a coding strategy specifically developed for the purposes of this study.
Results: Titles and content were predominantly loss, high alarm and high vulnerability framed. The content was also gain framed, and written with a focus on the social and legal aspects differentially between the newspaper types.
Discussion: The tabloid press emphasizes social issues, and the middle market and serious press focus on legal issues of altruistic surrogacy. Selectively framed and reinforced information provided by the different newspapers, reflect the different readership, with Tabloid readers likely to be, surrogates (mostly from lower socioeconomic strata) and serious/ middle-market readers likely to be commissioning parents (mostly professionals)
On the symmetries of BF models and their relation with gravity
The perturbative finiteness of various topological models (e.g. BF models)
has its origin in an extra symmetry of the gauge-fixed action, the so-called
vector supersymmetry. Since an invariance of this type also exists for gravity
and since gravity is closely related to certain BF models, vector supersymmetry
should also be useful for tackling various aspects of quantum gravity. With
this motivation and goal in mind, we first extend vector supersymmetry of BF
models to generic manifolds by incorporating it into the BRST symmetry within
the Batalin-Vilkovisky framework. Thereafter, we address the relationship
between gravity and BF models, in particular for three-dimensional space-time.Comment: 29 page
Construction of nonsingular cosmological solutions in string theories
We study nonsingular cosmological scenarios in a general -dimensional
string effective action of the dilaton-modulus-axion system in the presence of
the matter source. In the standard dilatonic Brans-Dicke parameter
() with radiation, we analytically obtain singularity-free bouncing
solutions where the universe starts out in a state with a finite curvature and
evolves toward the weakly coupled regime. We apply this analytic method to the
string-gas cosmology including the massive state in addition to the leading
massless state (radiation), with and without the axion. We numerically find
bouncing solutions which asymptotically approach an almost radiation-dominant
universe with a decreasing curvature irrespective of the presence of the axion,
implying that inclusion of the matter source is crucial for the existence of
such solutions for . In the theories with , it is
possible to obtain complete regular bouncing solutions with a finite dilaton
and curvature in both past and future asymptotics for the general dimension,
. We also discuss the case where dilatonic higher-order corrections are
involved to the tree-level effective action and demonstrate that the presence
of axion/modulus fields and the matter source does not significantly affect the
dynamics of the dilaton-driven inflation and the subsequent graceful exit.Comment: 27 pages, 6 eps figure
Prevalence and predictors of tuberculin skin positivity in Hellenic Army recruits
BACKGROUND: Tuberculosis (TB) remains one of the leading causes of death among infectious diseases worldwide. Despite its low incidence rates in countries of Western Europe and North America, the resurgence of TB in Eastern Europe and the increased immigration from high-incidence countries imply that extreme vigilance is required in order to detect early, treat, and isolate all new cases. In this study, we analyzed the prevalence and predictors of tuberculin skin testing positivity in Hellenic Army recruits. METHODS: The study population consisted of 953 Greek military recruits enlisted inthe Army during the period from November 2005 toFebruary 2006. Tuberculin skin testing was performed on all study subjects upon enrollment, according to the routine procedures. A tuberculin skin test reaction size >15 mm was considered positive for all study participants. Epidemiological data regarding age, repatriation status, geographic area of residence, smoking habits, and parental occupation were collected by means of personal interviews. In addition, body weight, height, and body mass index were measured. RESULTS: The mean age of the studied subjects (± SD) was 23.5 (± 6.4) years. The overall prevalence of tuberculin positivity was 3.9% (37/953), and bivariable analysis showed that it was associated with lower weight (p = 0.047) and repatriation status (p < 0.001). Tuberculin skin testing was positive in 2.6% of natives (24/900) and 24.5% of repatriates (13/53). A backward, stepwise multivariable logistic regression model showed that only repatriation status was independently associated with tuberculin positivity (p < 0.001; odds ratio [OR]: 14.1; 95% confidence interval [CI]: 6.5â30.3). CONCLUSION: While the incidence of tuberculosis in the native Greek population is low, and comparable to other Western European countries, the extremely high tuberculin positivity in repatriated persons underscores the importance of actively screening for TB in order to promptly identify, isolate, and treat cases of active and latent infection
Anointed or appointed? Fatherâdaughter succession within the family business
With the focus on events and outcomes shaping most of the existing family business research
on intra-family succession, the subtleties of the incumbent-successor relationship and the
dynamic nature of succession as a process of becoming is somewhat neglected. In particular,
we have limited understanding of how successor identities are constructed as legitimate
between incumbent and successor during father-daughter succession. This article addresses this
gap in understanding by exploring how the daughter successor engages in identity work with
the father incumbent during the process of succession and the role of father-daughter gendered
relations in shaping her successor identity. Using a two-stage research design strategy, we draw
upon empirical evidence derived from 14 individual and joint semi-structured interviews to
present a narrative analysis of five father-daughter dyads. In so doing, we unveil how the
daughterâs successor identity was co-constructed as legitimate and how father-daughter
gendered relations influenced this process. Although daughters rely on certain father-daughter
relations (preparation, endorsement and osmotic credibility) for legitimacy, they also need to
develop independently from their father in order to heighten their own visibility and establish
credibility
Symmetries of topological field theories in the BV-framework
Topological field theories of Schwarz-type generally admit symmetries whose
algebra does not close off-shell, e.g. the basic symmetries of BF models or
vector supersymmetry of the gauge-fixed action for Chern-Simons theory (this
symmetry being at the origin of the perturbative finiteness of the theory). We
present a detailed discussion of all these symmetries within the algebraic
approach to the Batalin-Vilkovisky formalism. Moreover, we discuss the general
algebraic construction of topological models of both Schwarz- and Witten-type.Comment: 30 page
The EUFOREA pocket guide for chronic rhinosinusitis
Chronic rhinosinusitis (CRS) is known to affect around 5 % of the total population, with major impact on the quality of life of those severely affected (1). Despite a substantial burden on individuals, society and health economies, CRS often remains underdiagnosed, under-estimated and under-treated (2). International guidelines like the European Position Paper on Rhinosinusitis and Nasal Polyps (EPOS) (3) and the International Consensus statement on Allergy and Rhinology: Rhinosinusitis 2021 (ICAR) (4) offer physicians insight into the recommended treatment options for CRS, with an overview of effective strategies and guidance of diagnosis and care throughout the disease journey of CRS
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