1,720,986 research outputs found
Exact solutions of Einstein and Einstein-Maxwell gravity minimally coupled to a scalar field
No full textWe present a general method for solving exactly the static field equations of Einstein and Einstein-Maxwell gravity minimally coupled to a scalar field. Through this method one can derive broad classes of static solutions with radial symmetry of the theory, which may play an important role in applications of the AdS/CFT correspondence to condensed matter and strongly coupled QFT's. Moreover, the method allows to prove a new no-hair theorem about the existence of hairy black brane and black hole solutions
Black brane solutions and their solitonic extremal limit in Einstein-scalar gravity
No full textWe investigate static, planar solutions of Einstein-scalar gravity admitting an anti-de Sitter (AdS) vacuum. When the squared mass of the scalar field is positive and the scalar potential can be derived from a superpotential, minimum energy theorems indicate the existence of a scalar soliton. On the other hand, for these models, no-hair theorems forbid the existence of hairy black brane solutions with AdS asymptotics. By considering a specific example (an exact integrable model which has the form of a Toda molecule) and by deriving explicit exact solution, we show that these models allow for hairy black brane solutions with non-AdS domain wall asymptotics, whose extremal limit is a scalar soliton. The soliton smoothly interpolates between a non-AdS domain wall solution at r = infinity and an AdS solution near r = 0
Brane solutions sourced by a scalar with vanishing potential and classification of scalar branes
No full textAbstract: We derive exact brane solutions of minimally coupled Einstein-Maxwell-scalar gravity in d + 2 dimensions with a vanishing scalar potential and we show that these solutions are conformal to the Lifshitz spacetime whose dual QFT is characterized by hyperscaling violation. These solutions, together with the AdS brane and the domain wall sourced by an exponential potential, give the complete list of scalar branes sourced by a generic potential having simple (scale-covariant) scaling symmetries not involving Galilean boosts. This allows us to give a classification of both simple and interpolating brane solution of minimally coupled Einstein-Maxwell-scalar gravity having no Schrödinger isometries, which may be very useful for holographic applications
Infrared behavior of scalar condensates in effective holographic theories
No full textWe investigate the infrared behavior of the spectrum of scalar-dressed, asymptotically Anti de Sitter (AdS) black brane (BB) solutions of effective holographic models. These solutions describe scalar condensates in the dual field theories. We show that for zero charge density the ground state of these BBs must be degenerate with the AdS vacuum, must satisfy conformal boundary conditions for the scalar field and it is isolated from the continuous part of the spectrum. When a finite charge density is switched on, the ground state is not anymore isolated and the degeneracy is removed. Depending on the coupling functions. the new ground state may possibly be energetically preferred with respect to the extremal Reissner-Nordstrom AdS BB. We derive several properties of BBs near ext remality and at finite temperature. As a check and illustration of our results we derive and discuss several analytic and numerical, HU solutions of Hinstein-scalar-Maxwell AdS gravity with different coupling functions and different potentials. We also discuss how our results can be used for understanding holographic quantum critical points, in particular their stability and the associated quantum phase transitions loading to superconductivity or hyperscaling violation
Hyperscaling violation for scalar black branes in arbitrary dimensions
No full textWe extend to black branes (BB) in arbitrary dimensions the results of ref. [1] about hyperscaling violation and phase transition for scalar black 2-branes. We derive the analytic form of the (d + 1)-dimensional scalar soliton interpolating between a conformal invariant AdS(d+2) vacuum in the infrared and a scale covariant metric in the ultraviolet. We show that the thermodynamical system undergoes a phase transition between Schwarzschild-AdS(d+2) and a scalar-dressed HE. We calculate the critical exponent z and the hyperscaling violation parameter theta in the two phases. We show that our scalar NB solutions generically emerge as compactifications of p-brane solutions of supergravity theories. We also derive the short distance form of the correlators for the scalar operators corresponding to an UV exponential potential supporting our black brane solution. We show that also for negative theta these correlators have a short distance power-law behavior
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Bridging the Gap Between Strategic Environmental Assessment and Planning: A Geodesign Perspective Revised
Get PDFCurrent planning practices in Europe are affected by regulations aiming at environmental protection and risk reduction; however, planners face difficulties in implementing the norms. This chapter discusses the influence of the introduction of strategic environmental assessment and of spatial data infrastructures in the EU. To address these issues, the geodesign approach is proposed, firstly analyzing its relationships with the current planning regulations at the regional level in Italy and then its opportunities for application in practice with regard to the Sardinian case study (Italy); secondly, examples of Planning Support System are proposed and tested with real-world case studies to implement the core phases of the geodesign approach. In addition, the benefits for SEA of developing state-of-the-art workflows in geodesign collaborative workshops are discussed. The chapter concludes suggesting that geodesign may fruitfully address some of the major issues in the current planning and SEA practice, taking full advantage of the newly available resources of SDI
The fluorine in surface waters: origin, weight on human health, and defluoridation techniques
Get PDFIn order to understand the distribution of fluorine in surface environments, also linked to fluoride deposits, this paper discusses the role of rift systems in fluorine enrichment of surface waters, with two examples: the Sardinia Island and the East African Rift. The main goal of this study is aimed to highlighting the areas that could potentially host fluorine in the surface waters in order to make it easier the lecture also for people to search and read not experts in the field, such as the biomedical field. Furthermore, potentialities and limitations of the currently available defluoridation techniques were examined, in order to identify the best intervention technology.
From a careful review of the literature, to the addition of the extensive field observations in Sardinia and Ethiopia carried by the authors in the previous decades, we highlight the origin, processes and evolution of F-migration in Rift systems.
The given examples of Sardinia and Ethiopia show that the origin and consequent behaviour of fluorine is strictly controlled by the rift systems. In this framework, the availability of fluorine for surface waters depends on two possible types of sources: a direct supply and an indirect supply. Directly from spring waters and ground waters fed by hydrothermal systems related to rifting, and indirectly from the leaching of products of rift-related activities, such as fluorite-bearing deposits, sedimentary or meta-sedimentary rift-related sequences, and volcanic or metavolcanic complexes emplaced along rift structures. The whole geological history of a given area must be taken into account in interpreting its present fluorine geochemistry.
In conclusion, we underline the aspects of a possible control of these areas where fluoride exposure might lead to a long-term harm to local communities and we point out the nowadays best remediation-technologies, discussing their pro and cons in their applicability to different scales and social-contexts
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
- …
