6,319 research outputs found
Quasinormal modes of Einstein-Gauss-Bonnet-dilaton black holes
No full textWe study quasinormal modes of static Einstein-Gauss-Bonnet-dilaton black holes. Both axial and polar perturbations are considered and studied from l = 0 to l = 3. We emphasize the difference in the spectrum between the Schwarzschild solutions and dilatonic black holes. At large Gauss-Bonnet coupling constant, a small secondary branch of black holes is present, when the dilaton coupling is sufficiently strong. The modes of the primary branch can differ from the Schwarzschild modes up to 10%. The secondary branch is unstable and possesses long-lived modes. We address the possible effects of these modes on future observations of gravitational waves emitted during the ringdown phase of astrophysical black holes.Deutsche ForschungsgemeinschaftEuropean CommissionDepto. de Física TeóricaFac. de Ciencias FísicasTRUEpu
Quasinormal modes of an electrically charged AdS black hole in 4D Einstein-Gauss-Bonnet gravity
No full textLas ondas de las perturbaciones de los agujeros negros dependen de los parámetros geométricos del espacio-tiempo que los describe. En este trabajo se investigan las perturbaciones en campos escalares y electromagnéticos sobre la geometría de un agujero negro AdS cargado eléctricamente en la gravedad de Einstein-Gauss-Bonnet 4D, mostrando la deducción de las ecuaciones de campo modificadas, los comportamientos de las principales propiedades de este agujero negro y su relación con sus casos limite particulares y con otras teorías de gravedad. Se derivan a las ecuaciones maestras y a los potenciales que describen a las perturbaciones y se discuten los métodos para encontrar las frecuencias de los modos cuasinormales, explorando principalmente al formalismo del método de la aproximación WKB, discutiendo sus fundamentos y algunas de sus restricciones y mejoras. Se calculan numéricamente, mediante el uso de los métodos semi-analíticos del potencial de Pöschl-Teller y de la aproximación WKB, a las frecuencias de los modos cuasinormales del campo escalar (con y sin masa) y del campo electromagnético alrededor de un agujero negro AdS con carga eléctrica y en la gravedad de Einstein-Gauss-Bonnet 4D y de sus casos limite particulares, encontrando destacados resultados, como el hecho de que este agujero negro es mejor oscilador que los agujeros negros de Schwarzschild, de Reissner–Nordström, de Einstein-Gauss-Bonnet 4D y de Einstein-Gauss-Bonnet 4D con carga eléctrica y por ende posee una sombra más pequeña. También se describen los efectos de los parámetros geométricos sobre las frecuencias calculadas, encontrando destacadas consistencias en los resultados obtenidos comparados entre si y con los ya publicados por otros autores. (Texto tomado de la fuente)The waves of black hole perturbations depend on the geometric parameters of space-time that describe them. In this work we investigate the perturbations in scalar and electromagnetic fields on the geometry of an electrically charged AdS black hole in Einstein-Gauss-Bonnet 4D gravity, showing the deduction of the modified field equations, the behavior of the main properties of this black hole and its relationship with its particular limit cases and with other gravity theories. The master equations and potentials describing the perturbations are derived and methods for finding the frequencies of Quasinormal Modes are discussed, mainly exploring the formalism of the WKB approximation method, discussing its fundamentals and some of its restrictions and enhancements. They are calculated numerically, using the semi-analytic methods of the Pöschl-Teller potential and the WKB approximation, the frequencies of the Quasinormal Modes of the scalar field (with and without mass) and the electromagnetic field around an electrically charged AdS black hole in the Einstein-Gauss-Bonnet 4D gravity and its particular limit cases, finding outstanding results, such as the fact that this black hole is a better oscillator than the Schwarzschild, Reissner–Nordström, Einstein-Gauss-Bonnet 4D and Einstein-Gauss-Bonnet 4D black holes with electric charge and therefore it has a smaller shadow. The effects of the geometric parameters on the calculated frequencies are also described, finding outstanding consistency in the results obtained compared with each other and with those already published by other authors.MaestríaRelatividad General y Agujeros Negro
Quasinormal modes of an electrically charged AdS black hole in 4D Einstein-Gauss-Bonnet gravity
No full textLas ondas de las perturbaciones de los agujeros negros dependen de los parámetros geométricos del espacio-tiempo que los describe. En este trabajo se investigan las perturbaciones en campos escalares y electromagnéticos sobre la geometría de un agujero negro AdS cargado eléctricamente en la gravedad de Einstein-Gauss-Bonnet 4D, mostrando la deducción de las ecuaciones de campo modificadas, los comportamientos de las principales propiedades de este agujero negro y su relación con sus casos limite particulares y con otras teorías de gravedad. Se derivan a las ecuaciones maestras y a los potenciales que describen a las perturbaciones y se discuten los métodos para encontrar las frecuencias de los modos cuasinormales, explorando principalmente al formalismo del método de la aproximación WKB, discutiendo sus fundamentos y algunas de sus restricciones y mejoras. Se calculan numéricamente, mediante el uso de los métodos semi-analíticos del potencial de Pöschl-Teller y de la aproximación WKB, a las frecuencias de los modos cuasinormales del campo escalar (con y sin masa) y del campo electromagnético alrededor de un agujero negro AdS con carga eléctrica y en la gravedad de Einstein-Gauss-Bonnet 4D y de sus casos limite particulares, encontrando destacados resultados, como el hecho de que este agujero negro es mejor oscilador que los agujeros negros de Schwarzschild, de Reissner–Nordström, de Einstein-Gauss-Bonnet 4D y de Einstein-Gauss-Bonnet 4D con carga eléctrica y por ende posee una sombra más pequeña. También se describen los efectos de los parámetros geométricos sobre las frecuencias calculadas, encontrando destacadas consistencias en los resultados obtenidos comparados entre si y con los ya publicados por otros autores. (Texto tomado de la fuente)The waves of black hole perturbations depend on the geometric parameters of space-time that describe them. In this work we investigate the perturbations in scalar and electromagnetic fields on the geometry of an electrically charged AdS black hole in Einstein-Gauss-Bonnet 4D gravity, showing the deduction of the modified field equations, the behavior of the main properties of this black hole and its relationship with its particular limit cases and with other gravity theories. The master equations and potentials describing the perturbations are derived and methods for finding the frequencies of Quasinormal Modes are discussed, mainly exploring the formalism of the WKB approximation method, discussing its fundamentals and some of its restrictions and enhancements. They are calculated numerically, using the semi-analytic methods of the Pöschl-Teller potential and the WKB approximation, the frequencies of the Quasinormal Modes of the scalar field (with and without mass) and the electromagnetic field around an electrically charged AdS black hole in the Einstein-Gauss-Bonnet 4D gravity and its particular limit cases, finding outstanding results, such as the fact that this black hole is a better oscillator than the Schwarzschild, Reissner–Nordström, Einstein-Gauss-Bonnet 4D and Einstein-Gauss-Bonnet 4D black holes with electric charge and therefore it has a smaller shadow. The effects of the geometric parameters on the calculated frequencies are also described, finding outstanding consistency in the results obtained compared with each other and with those already published by other authors.MaestríaRelatividad General y Agujeros Negro
FINANCING COMMUNITY FACILITIES: A CASE STUDY OF THE PARKS AND RECREATIONAL GENERAL OBLIGATION BOND MEASURE OF SAN JOSE, CALIFORNIA
No full textThis study of the City of San Jose’s Parks and Recreation General Obligation (GO) Bond Measure seeks to identify the politics-, management-, and planning-related lessons learned by the City as it developed its community facilities using the GO bonds proceeds. The study finds that these lessons include: be conservative in what you promise the residents; be prepared for changes in economic environment by identifying supplementary funding sources should the primary source not yield adequate funds; make sure that the jurisdiction is organizationally capable of handling the increased workload; and prepare detailed project plans prior to the bond issuance.Community Infrastructure and Services; Municipal Bonds; Public Finance
Perturbed black holes in Einstein-dilaton-Gauss-Bonnet gravity: Stability, ringdown, and gravitational-wave emission
No full textGravitational waves emitted by distorted black holes—such as those arising from the coalescence of two neutron stars or black holes—carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant, and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here, we focus on a particularly appealing extension of general relativity, which corrects Einstein’s theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations, (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that future ringdown detections with a large signal-to-noise ratio would improve current constraints on the coupling parameter of the theory
Jose Maria Alvarez Biographical Sketch and Commentary - Accession 171 - M76 (92-94)
No full textThe Jose Maria Alvarez Papers consist of a paper titled “Conversaciones con Jose Maria Alvarez” by Juan Miguel Margalef in collaboration with Jesus Munarriz and Csaba Csuday. Alvarez is a Spanish author and historian who has written articles, books, movie scripts and poetry. The paper contains biographical information concerning Alvarez as well as comments on his writing. The paper is written in Spanish.https://digitalcommons.winthrop.edu/manuscriptcollection_findingaids/1304/thumbnail.jp
Dr. Jose Franco Rodriguez & - The Gift of Bicameral Mentality in Lake Atitlan\u27s Mayan Ora
No full textDr. Jose Franco Rodriguez and speaks at the Chesnutt Library of Fayetteville State University about their recent research Of Gods And Men- The Gift of Bicameral Mentality in Lake Atitlan\u27s Mayan Ora.
Presented live on March 5, 2025 as part of Chesnutt Library\u27s Faculty Author Series.https://digitalcommons.uncfsu.edu/faculty_author/1012/thumbnail.jp
Jose Miguel Ramos Arispe
No full textPhotograph shows an engraving of Jose Miguel Ramos Arispe, considered the Father of Mexican Federalism and author of the 1824 Mexican Constitution
Black holes in Einstein-Gauß-Bonnet-dilaton theory
No full textGeneralizations of the Schwarzschild and Kerr black holes are discussed in an astrophysically viable generalized theory of gravity, which includes higher curvature corrections in the form of the Gauss-Bonnet term, coupled to a dilaton. The angular momentum of these black holes can slightly exceed the Kerr bound. The location and the orbital frequency of particles in their innermost stable circular orbits can deviate significantly from the respective Kerr values. Study of the quasinormal modes of the static black holes gives strong evidence that they are mode stable against polar and axial perturbations. Future gravitational wave observations should improve the current bound on the Gauss-Bonnet coupling constant, based on observations of the low-mass x-ray binary A 0620-00
Radial perturbations of the scalarized Einstein-Gauss-Bonnet black holes
No full textRecently a new class of scalarized black holes in Einstein-Gauss-Bonnet (EGB) theories was discovered. What is special for these black hole solutions is that the scalarization is not due to the presence of matter, but it is induced by the curvature of spacetime itself. Moreover, more than one branch of scalarized solutions can bifurcate from the Schwarzschild branch, and these scalarized branches are characterized by the number of nodes of the scalar field. The next step is to consider the linear stability of these solutions, which is particularly important due to the fact that the Schwarzschild black holes lose stability at the first point of bifurcation. Therefore we here study in detail the radial perturbations of the scalarized EGB black holes. The results show that all branches with a nontrivial scalar field with one or more nodes are unstable. The stability of the solutions on the fundamental branch, whose scalar field has no radial nodes, depends on the particular choice of the coupling function between the scalar field and the Gauss-Bonnet invariant. We consider two particular cases based on the previous studies of the background solutions. If this coupling has the form used in [D. D. Doneva and S. S. Yazadjiev, Phys. Rev. Lett. 120, 131103 (2018)] the fundamental branch of solutions is stable, except for very small masses. In the case of a coupling function quadratic in the scalar field [H. O. Silva, J. Sakstein, L. Gualtieri, T. P. Sotiriou, and E. Berti, Phys. Rev. Lett. 120, 131104 (2018)], though, the whole fundamental branch is unstable.Deutsche ForschungsgemeinschaftEuropean CommissionSofia UniversityMinisterium für Wissenschaft, Forschung und Kunst (Baden-Württemberg)Baden-Wurttemberg StiftungDepto. de Física TeóricaFac. de Ciencias FísicasTRUEpu
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