5,888 research outputs found
An Analytic Method for -Expansion involving Resonance and Reduction
In this paper we describe an analytic method able to give the multiplication
table(s) of the set(s) involved in an -expansion process (with either
resonance or -resonant-reduction) for reaching a target Lie (super)algebra
from a starting one, after having properly chosen the partitions over subspaces
of the considered (super)algebras. This analytic method gives us a simple set
of expressions to find the partitions over the set(s) involved in the process.
Then, we use the information coming from both the initial (super)algebra and
the target one for reaching the multiplication table(s) of the mentioned
set(s). Finally, we check associativity with an auxiliary computational
algorithm, in order to understand whether the obtained set(s) can describe
semigroup(s) or just abelian set(s) connecting two (super)algebras. We also
give some interesting examples of application, which check and corroborate our
analytic procedure and also generalize some result already presented in the
literature.Comment: v3, 47 pages, misprints corrected in Fortschritte der Physik,
Published online 7 November 201
Minimal Supergravity and the supersymmetry of Arnold-Beltrami Flux branes
In this paper we study some properties of the newly found Arnold-Beltrami
flux-brane solutions to the minimal supergravity. To this end we first
single out the appropriate Free Differential Algebra containing both a gauge
-form and a gauge -form : then we
present the complete rheonomic parametrization of all the generalized
curvatures. This allows us to identify two-brane configurations with
Arnold-Beltrami fluxes in the transverse space with exact solutions of
supergravity and to analyze the Killing spinor equation in their background. We
find that there is no preserved supersymmetry if there are no additional
translational Killing vectors. Guided by this principle we explicitly construct
Arnold-Beltrami flux two-branes that preserve , and of the
original supersymmetry. Two-branes without fluxes are instead BPS states and
preserve supersymmetry. For each two-brane solution we carefully study
its discrete symmetry that is always given by some appropriate crystallographic
group . Such symmetry groups are transmitted to the
gauge theories on the brane world--volume that occur in the gauge/gravity
correspondence. Furthermore we illustrate the intriguing relation between gauge
fluxes in two-brane solutions and hyperinstantons in topological
sigma-models.Comment: 56 pages, LaTeX source, 8 jpg figures, typos correcte
Generalized cosmological term in D=4 supergravity from a new AdS-Lorentz superalgebra
A new supersymmetrization of the so-called AdS-Lorentz algebra is presented.
It involves two fermionic generators and is obtained by performing an abelian
semigroup expansion of the superalgebra osp(4|1). The peculiar properties of
the aforesaid expansion method are then exploited to construct a D=4
supergravity action involving a generalized supersymmetric cosmological term in
a geometric way, only from the curvatures of the novel superalgebra. The action
obtained with this procedure is a MacDowell-Mansouri like action. Gauge
invariance and supersymmetry of the action are also analyzed.Comment: 25 pages. This is a preprint of the article published in Eur. Phys.
J. C 78 (2018) no.11, 945. The final authenticated version is available
online at: https://doi.org/10.1140/epjc/s10052-018-6421-
Editorial: The role of platinum-based antitumor prodrugs in medicinal inorganic chemistry
Editorial on the research topic "The role of platinum-based antitumor prodrugs in medicinal inorganic chemistry
Non-relativistic three-dimensional supergravity theories and semigroup expansion method
In this work we present an alternative method to construct diverse non-relativistic Chern-Simons supergravity theories in three spacetime dimensions. To this end, we apply the Lie algebra expansion method based on semigroups to a supersymmetric extension of the Nappi-Witten algebra. Two different families of non-relativistic superalgebras are obtained, corresponding to generalizations of the extended Bargmann superalgebra and extended Newton-Hooke superalgebra, respectively. The expansion method considered here allows to obtain known and new non-relativistic supergravity models in a systematic way. In particular, it immediately provides an invariant tensor for the expanded superalgebra, which is essential to construct the corresponding Chern-Simons supergravity action. We show that the extended Bargmann supergravity and its Maxwellian generalization appear as particular subcases of a generalized extended Bargmann supergravity theory. In addition, we demonstrate that the generalized extended Bargmann and generalized extended Newton-Hooke supergravity families are related through a contraction process
Evaluating diagnosis and treatment of oral and esophageal candidiasis in Ugandan AIDS patients.
A randomized cross-over clinical and endoscopic evaluation of 85 Ugandan patients showed that esophageal candidiasis in AIDS patients with oral candidiasis could be managed without endoscopy and biopsies. Oral lesions, especially when accompanied by esophageal symptoms, were sufficient for diagnosis. Miconazole was more effective than nystatin in treating esophageal candidiasis and could be a valid alternative to more expensive azolic drugs in developing countries
Climate Science, Development Practice, and Policy Interactions in Dryland Agroecological Systems
The literature on drought, livelihoods, and poverty suggests that dryland residents are especially vulnerable to climate change. However, assessing this vulnerability and sharing lessons between dryland communities on how to reduce vulnerability has proven difficult because of multiple definitions of vulnerability, complexities in quantification, and the temporal and spatial variability inherent in dryland agroecological systems. In this closing editorial, we review how we have addressed these challenges through a series of structured, multiscale, and interdisciplinary vulnerability assessment case studies from drylands in West Africa, southern Africa, Mediterranean Europe, Asia, and Latin America. These case studies adopt a common vulnerability framework but employ different approaches to measuring and assessing vulnerability. By comparing methods and results across these cases, we draw out the following key lessons: (1) Our studies show the utility of using consistent conceptual frameworks for vulnerability assessments even when quite different methodological approaches are taken; (2) Utilizing narratives and scenarios to capture the dynamics of dryland agroecological systems shows that vulnerability to climate change may depend more on access to financial, political, and institutional assets than to exposure to environmental change; (3) Our analysis shows that although the results of quantitative models seem authoritative, they may be treated too literally as predictions of the future by policy makers looking for evidence to support different strategies. In conclusion, we acknowledge there is a healthy tension between bottom-up/ qualitative/place-based approaches and top-down/quantitative/generalizable approaches, and we encourage researchers from different disciplines with different disciplinary languages, to talk, collaborate, and engage effectively with each other and with stakeholders at all levels
Pastoralist Conservation: Local Ecological Knowledge and Collective Action for Grassland Conservation in Sierra de Segura (Spain)
Even if Pastoralism is not practised anymore by a majority of families in the Sierra de Segura (south-eastern Andalusia, Spain), it is still considered a paradigmatic way of life and management of its highlands and a key cultural heritage deeply rooted in local identity. In this article we explore two pastoral communities of this region, Santiago and Pontones, with their body of situated knowledge of the territory and natural resources, which helps pastoralists to organize their livelihoods, while requiring collective organization to manage access to grasslands. Through an ethnographic research based on participant observation and in-depth interviews, we explore the knowledge system, practices and institutions relevant for the use and maintenance of mountain pastures. The results show how local governance strategies and management of pastures are organized, among other drivers, to be able to adapt over time to change. On the other hand, collective actions have a notable social component to enable access to pastures. However, the community faces challenges for its sustainability such as environmental change, low generational turnover and the diminishing presence of women, very particularly in pastoralist practice and decision-making
An update of the chemiosmotic theory as suggested by possible proton currents inside the coupling membrane
Understanding how biological systems convert and store energy is a primary purpose of basic research. However, despite Mitchell's chemiosmotic theory, we are far from the complete description of basic processes such as oxidative phosphorylation (OXPHOS) and photosynthesis. After more than half a century, the chemiosmotic theory may need updating, thanks to the latest structural data on respiratory chain complexes. In particular, up-to date technologies, such as those using fluorescence indicators following proton displacements, have shown that proton translocation is lateral rather than transversal with respect to the coupling membrane. Furthermore, the definition of the physical species involved in the transfer (proton, hydroxonium ion or proton currents) is still an unresolved issue, even though the latest acquisitions support the idea that protonic currents, difficult to measure, are involved. Moreover, F o F 1 -ATP synthase ubiquitous motor enzyme has the peculiarity (unlike most enzymes) of affecting the thermodynamic equilibrium of ATP synthesis. It seems that the concept of diffusion of the proton charge expressed more than two centuries ago by Theodor von Grotthuss is to be taken into consideration to resolve these issues. All these uncertainties remind us that also in biology it is necessary to consider the Heisenberg indeterminacy principle, which sets limits to analytical questions
Infinite S-expansion with ideal subtraction and some applications
According to the literature, the S-expansion procedure involving a finite semigroup is valid no matter what the structure of the original Lie (super)algebra is; however, when something about the structure of the starting (super)algebra is known and when certain particular conditions are met, the S-expansion method (with its features of resonance and reduction) is able not only to lead to several kinds of expanded (super)algebras but also to reproduce the effects of the standard as well as the generalized Inönü-Wigner contraction. In the present paper, we propose a new prescription for S-expansion, involving an infinite abelian semigroup S^(∞) and the subtraction of an infinite ideal subalgebra. We show that the subtraction of the infinite ideal subalgebra corresponds to a reduction. Our approach is a generalization of the finite S-expansion procedure presented in the literature, and it offers an alternative view of the generalized Inönü-Wigner contraction. We then show how to write the invariant tensors of the target (super)algebras in terms of those of the starting ones in the infinite S-expansion context presented in this work. We also give some interesting examples of application on algebras and superalgebras
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