1,721,022 research outputs found
Chasing the cuprates with dilatonic dyons
Get PDFAbstract: Magnetic field and momentum dissipation are key ingredients in describing condensed matter systems. We include them in gauge/gravity and systematically explore the bottom-up panorama of holographic IR effective field theories based on bulk EinsteinMaxwell Lagrangians plus scalars. The class of solutions here examined appears insufficient to capture the phenomenology of charge transport in the cuprates. We analyze in particular the temperature scaling of the resistivity and of the Hall angle. Keeping an open attitude, we illustrate weak and strong points of the approach
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
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Applied holography: a practical mini-course
No full textThis primer is a collection of notes based on lectures that were originally given at IIT Madras (India) and at IFT Madrid (Spain). It is a concise and pragmatic course on applied holography focusing on the basic analytic and numerical techniques involved. The presented lectures are not intended to provide all the fundamental theoretical background, which can be found in the available literature, but they concentrate on concrete applications of AdS/CFT to hydrodynamics, quantum chromodynamics and condensed matter. The idea is to accompany the reader step by step through the various benchmark examples with a classmate attitude, providing details for the computations and open-source numerical codes in Mathematica, and sharing simple tricks and warnings collected during the author’s research experience. At the end of this path, the reader will be in possess of all the fundamental skills and tools to learn by him/herself more advanced techniques and to produce independent and novel research in the field
How to sit Maxwell and Higgs on the boundary of Anti-de Sitter
Get PDFIn the context of bottom-up holography, we demonstrate the power of mixed
boundary conditions to promote the boundary gauge field to be dynamical. We
provide two concrete applications of this idea. First, we consider a
holographic dual for a strongly coupled plasma described by dissipative
magnetohydrodynamics. Second, we reveal the expected features of the Higgs
mechanism in a not counterfeit holographic superconductor.Comment: Proceedings for the 6 International Conference on Holography,
String Theory and Spacetime, held in Da Nang (Vietnam), 20-24 of February
2023. Based on arXiv:2211.01760 and arXiv:2302.0236
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Gravity, holography and applications to condensed matter
Get PDFLos sistemas fisicos fuertemente acoplados, junto a sus correspondientes y por lo general exoticas caracteristicas, son imposibles de tratar mediante los enfoques perturbativos convencionales que en estos casos no son capaces de proporcionar una herramienta controlable y robusta. Sin embargo, los efectos no perturbativos y fenomenos fuertemente correlacionados abundan en la fisica, especialmente en la Fisica de la Materia Condensada.
La correspondencia AdS / CFT, que nace de el estimulo de las ideas y esfuerzos empleados en descubrir una posible descripcion de la gravedad cuantica, proporciona una perspectiva inesperada e innovadora para hacer frente a las teorías de campo fuertemente acopladas. En su formulacion mas general este planteamiento ofrece un arma efectiva para hacer frente a ese tipo de problemas utilizando una descripcion dual de teorias gauge mediante teorias de gravedad que resulta ser mas simple que la original.
En los ultimos anos ha habido un gran numero de avances aplicando esta dualidad a temas modernos e innovadores en materia condensada, tales como la naturaleza de los metales raros o el mecanismo que subyace la superconductividad de alta Tc.
La relajacion del momento es un ingrediente omnipresente e inevitable de cualquier sistema realista en Materia Condensada. En los materiales del mundo real la presencia de un reticulo, de impurezas, o de desorden hacen que el momento se disipe, y se da lugar a efectos fisicos relevantes, tales como las propiedades de transporte de corriente continua sean finitas,es decir, la conductividad.
Hay varias preguntas abiertas relacionadas a dichas cantidades, especialmente en el limite de maxima relajacion donde surgen nuevos estados aislantes y transiciones de fase cuantica inesperadas entre los estados ultimos y metalicos (MIT) .
El objetivo principal de esta tesis es la introduccion de disipacion de momento y sus efectos en el contexto Ads/CMT, es decir, las aplicaciones de la dualidad Gauge-Gravedad en materia condensada.
Una manera conveniente y efectiva de romper la simetria traslacional de la teoria cuantica de campos dual es proporcionada por las teorias de gravedad masiva (GM), que constituye una herramienta facil y manejable para atacar varias e interesantes preguntas sobre sistemas fuertemente acoplados con disipacion de impulso. Originalmente concebido para resolver problemas en cosmologia, la GM puede ahora ser empleada bajo una perspectiva completamente nueva y podria convertirse en una herramienta útil para aplicaciones del ''mundo real'' y ''de bajas energias''. Consideramos modelos genericos de gravedad masiva en espacio-tiempos asintóticamente anti de Sitter y los analizamos usando tecnicas holograficas.Strongly coupled physical systems along with their corresponding, and usually exotic, features are elusive and not suitable to be described by conventional and perturbative approaches, which in those cases are not able to provide a controllable and robust tool for computations. Nevertheless non perturbative effects and strongly correlated frameworks are ubiquitous in nature, expecially in
Condensed Matter physics. The AdS/CFT correspondence, born from the excitement of ideas and efforts employed in finding out a possible description of Quantum Gravity, lead to a flurry of fresh air into the subject, introducing an unexpected and brandnew perspective for dealing with strongly coupled field theories. In its more general formulation, known as Gauge-Gravity duality, this setup accounts for an effective and efficient weapon to tackle those kind of problems using a dual gravitational description which turns out to be way easier than the original one. In the last years, a huge number of developments have been achieved in applying the duality towards modern and hot condensed matter misteries, such as the Strange Metals nature or the mechanism underlying the High-Tc Superconductivity.\\
Momentum relaxation is an ever-present and unavoidable ingredient of any realistic Condensed Matter
system. In real-world materials the presence of a lattice, impurities or disorder forces momentum to dissipate and leads to relevant physical effects such as the finiteness of the DC transport properties, i.e. conductivities. Several open questions are connected to those quantities expecially in the limit of strong momentum relaxation where novel insulating states appear and unexpected quantum phase transitions between the latter and metallic states (MIT) arise.\\[0.2cm]
The main purpose of this thesis is the introduction of momentum dissipation and its consequent effects into the framework of AdS/CMT, namely the applications of the Gauge-Gravity duality to Condensed Matter. \\
A convenient and effective way of breaking translational symmetry of the the dual quantum field theory is provided by Massive Gravity (MG) theories, which constitues a tractable and easy tool to adress several interesting questions in strongly coupled systems with momentum dissipation. Born to solve cosmological puzzles, MG can now be reconsidered under a completely new perspective and could become a useful framework for ''Real-world" phenomena and "low energy" applications. We consider generic massive gravity models embedded into asymptotically Anti de Sitter spacetime and we analyze them using holographic techniques
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