20,815 research outputs found
Black hole attractors and the entropy function in four- and five-dimensional N=2 supergravity
No full textExtremal black holes in theories of gravity coupled to abelian gauge fields and neutral scalars, such as those arising in the low-energy description of compactifications of string theory on Calabi-Yau manifolds, exhibit the attractor phenomenon: on the event horizon the scalars settle to values determined by the charges carried by the black hole and independent of the values at infinity. It is so, because on the horizon the energy contained in vector fields acts as an effective potential (the black hole potential), driving the scalars towards its minima.
For spherically symmetric black holes in theories where gauge potentials appear in the Lagrangian solely through field strengths, the attractor phenomenon can be alternatively described by a variational principle based on the so-called entropy function, defined as the Legendre transform with respect to electric fields of the Lagrangian density integrated over the horizon. Stationarity conditions for the entropy function then take the form of attractor equations relating the horizon values of the scalars to the black hole charges, while the stationary value itself yields the entropy of the black hole.
In this study we examine the relationship between the entropy function and the black hole potential in four-dimensional N=2 supergravity and demonstrate that in the absence of higher-order corrections to the Lagrangian these two notions are equivalent. We also exemplify their practical application by finding a supersymmetric and a non-supersymmetric solution to the attractor equations for a conifold prepotential.
Exploiting a connection between four- and five-dimensional black holes we then extend the definition of the entropy function to a class of rotating black holes in five-dimensional N=2 supergravity with cubic prepotentials, to which the original formulation did not apply because of broken spherical symmetry and explicit dependence of the Lagrangian on the gauge potentials in the Chern-Simons term. We also display two types of solutions to the respective attractor equations.
The link between four- and five-dimensional black holes allows us further to derive five-dimensional first-order differential flow equations governing the profile of the fields from infinity to the horizon and construct non-supersymmetric solutions in four dimensions by dimensional reduction.
Finally, four-dimensional extremal black holes in N=2 supergravity can be also viewed as certain two-dimensional string compactifications with fluxes. Motivated by this fact the recently proposed entropic principle postulates as a probability measure on the space of these string compactifications the exponentiated entropy of the corresponding black holes. Invoking the conifold example we find that the entropic principle would favor compactifications that result in infrared-free gauge theories
Jan Kapr's contribution to contemporary music : an essay about a composer and teacher
No full textThis creative project is a treatise on a leading personality of Czechoslovakian musical life, the composer, Jan Kapr. The author discusses the following:1. The complicated development of Kapr's career and work, 2. Kapr's method of organization of musical material in a composition, as described in his book Constants,3. His former and current style which is demonstrated in two of his compositions, Concert Variations, for flute and string orchestra and Testimonies for four solo instruments,4. Two of his recent works, Exercises for Gydli and the Symphony No. 7, Country of Childhood.Thesis (M.A.
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
ELEVEN FACES OF JAN GOGOL, JR.
No full textAuthor Jan Rendl in his thesis attempts to look at the world of ideas and educator Jan
Gogola ml. through the eleven chapters in which each chapter somehow characterizes itself by Jan Gogola ml. and each of them somehow determines its creative ideas of it through the metaphor of a football match when Jan Gogola, with its characters, movies himself a teammate, as well as defensively. It gives goals with their situations as well as occasionally digging his opponents ankles.
Jan Gogola ml. thus embodies one stage of the Department of Documentary Film at FAMU, which often stands at the intersection between teaching activities and Karel Vachek among students who applied by them during their seminars psychological methods that work must be peculiarly associated with the author of the film
Dr. Jan French – Faculty Author Interview
No full textDr. Jan French, Assistant Professor of Anthropology, discusses her new book, Legalizing Identities: Becoming Black or Indian in Brazil’s Northeast, which shows how law can successfully serve as the impetus for the transformation of cultural practices and collective identity
Jan Bernátek - organ works
No full textThis graduation thesis provides a more detailed view on compositoins of Jan Bernátek.The aim is to present this less well-known temporary czech author,who makes use of the organ in the majority of his work
The Theological Work of Jan Valerián Jirsík
No full textAnglická anotace The theological work of Jan Valerian Jirsík Jan Hamberger This thesis deals with the theological work of the Czech 19th century author Jan Valerián Jirsík (1798-1883). Its first part consists of an introduction into the Czech historical context of the 19th century and the life of the author. Its second part presents a survey of the literary-theological work of Jirsík in three life phases: the first phase is demarked by his activity as chaplain and vicar, the second phase by his editorial activity for Casopis pro katolické duchovenstvo (trans. Magazine for catholic clergy) and the last phase by his pontifical years in the diocese of Southern Bohemia. His literary work is divided by theme into various periods, shortly described and characterized. The last and major section of this thesis deals with the most comprehensive and renown work of Jan Valerián Jirsík - Populární dogmatika (trans. Popular doctrine). This pivotal work of theologian Jirsík is discussed at large and analyzed by tractate, both apologetic and dogmatic. The conclusion expresses the prevailing character of the entire work of Jirsík and its significance. Key words: Theology Apologetic theology Dogmatic theology Theological literature Catholic Churc
Actor Profile of Jan Vondracek
No full textDivided into seven chapters, the work treats seven roles of the Czech actor Jan Vondracek (born in 1966) in Divadlo v Dlouhe Theatre from 1997-2008. The author starts from the analysis of Vondracek's performances and describes the specifics of his
showmanship and generalizes the personality traits of his characters. She also ponders the meaning of Czech dramatic art based on
typical characters in the context of contemporary Czech theatre
The picture of Jan Palach in czech culture
No full textThis thesis deals with cultural image of Jan Palach. It focuses especially on symbols and myths contributing to construction of this image. The main emphasis is given on the concept of sacrifice - the study analyzes comparisons of Jan Palach to archetypes of Jesus Christ and young martyrs. In the second part author analyzes national dimension of Palach's cultural image. She deals with comparison of Palach to Jan Hus and analyzes Palach's funeral as a part of tradition of Czech public funerals - quiet national demonstrations. The methodology of the study is discourse analysis, which is applied not only on texts (fiction and nonfiction), but also on photographic and film footage
Jan Maruna - the author of my region
No full textNa začátku práce jsem autora blíže představila a následně analyzovala jeho tři romány: Ambra a moře v nás, Hrobník od Svatého Bartoloměje, Vlak do nebe.
Při rozboru textů jsem se zaměřila na téma, prostředí a čas, charakteristiku postav, kompozici, jazyk a jeho prostředky.
Práce je rozdělena do čtyř hlavních kapitol: Portrét Jana Maruny, Vybrané romány, Analýza struktury vybraných děl a Ostatní prozaická díla v kontextu Jana Maruny.Katedra českého jazyka a literaturyObhájenoAt the beginning of the thesis I introduced the author in more detail and subsequently analysed his three novels: Ambra a moře v nás, Hrobník od Svatého Bartoloměje, Vlak do nebe. When I was examining the texts I was focused on the topic, setting and time, characteristic of characters, composition, language and its devices. The Bachelor thesis is divided into 4 main chapters: Portrait of Jan Maruna, Chosen novels, Analysis of structure of chosen works and Other prosaic works in context of Jan Maruna
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