21,192 research outputs found
sj-docx-1-hij-10.1177_19401612211025238 - Supplemental material for A Downward Spiral? A Panel Study of Misinformation and Media Trust in Chile
No full textSupplemental material, sj-docx-1-hij-10.1177_19401612211025238 for A Downward Spiral? A Panel Study of Misinformation and Media Trust in Chile by Sebastián Valenzuela, Daniel Halpern and Felipe Araneda in The International Journal of Press/Politics</p
Instability of asymptotically anti de Sitter black holes under Robin conditions at the timelike boundary
Full text linkArtículo finalmente publicado en: Araneda, B. G. y Dotti, G. D. (2017). Instability of asymptotically anti de Sitter black holes under Robin conditions at the timelike boundary. Physical Review D, 96(10), 104020. https://doi.org/10.1103/PhysRevD.96.104020Fil: Araneda, Bernardo Gabriel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Araneda, Bernardo Gabriel. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina.Fil: Araneda, Bernardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Dotti, Gustavo Daniel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Dotti, Gustavo Daniel. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina.Fil: Dotti, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.The static region outside the event horizon of an asymptotically anti de Sitter black hole has a conformal timelike boundary I on which boundary conditions have to be imposed for the evolution of linear fields from initial data to be a well posed problem. Only homogeneous Dirichlet, Neumann or Robin conditions preserve the action of the background isometry group on the solution space. We study the case in which the modal decomposition of the linear field leads to potentials not diverging at the conformal timelike boundary. We prove that there is always an instability if Robin boundary conditions with large enough γ (the quotient between the values of the derivative of the field and the field at the boundary) are allowed. We explain the origin of this instability, show that for modes with nonnegative potentials there is a single unstable state and prove a number of properties of this state. Although our results apply in general to 1+1 wave equations on a half infinite domain with a potential that is not singular at the boundary, our motivation is to analyze the gravitational stability of the four dimensional Schwarzschild anti de Sitter black holes (SAdS 4 ) in the context of the black hole non modal linear stability program initiated in Phys. Rev. Lett. 112, 191101 (2014), and the related supersymmetric type of duality exchanging odd and even modes. We prove that this symmetry is broken except when a combination of Dirichlet conditions in the even sector and a particular Robin condition in the odd sector is enforced, or viceversa, and that only the first of these two choices leads to a stable dynamics.https://link.aps.org/doi/10.1103/PhysRevD.96.104020info:eu-repo/semantics/submittedVersionFil: Araneda, Bernardo Gabriel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Araneda, Bernardo Gabriel. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina.Fil: Araneda, Bernardo Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Dotti, Gustavo Daniel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina.Fil: Dotti, Gustavo Daniel. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina.Fil: Dotti, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Física de Partículas y Campo
Report on Meteorological Research March 1, 1935 (m-1)
No full textThe object of the report was to elucidate in detail the various features of the research program in meteorology being carried on at the Daniel Guggenheim Airship Institute in Akron, Ohio. Mr. L. J. Fangman, of the U.S. Weather Bureau, was collaborating with the author in carrying out work such as a study of autographic records of the various meteorological elements during frontal passages with a view to the possible prediction of the intensity of the accompanying disturbance as it may affect the operation of aircraft and a study of atmospheric gustiness with a view to finding the dependence between frequency end amplitude of velocity fluctuations and the vertical temperature and velocity gradients
(Fourth) Report on Meteorological Activities at the DGAI (8-1-36)(Weather Bureau Copy)
No full textThis report is on the investigations of frontal phenomena at the Daniel Guggenheim Airship Institute in Akron, Ohio from January 1, 1935 through August 1, 1936. The investigation was carried out with the cooperation of the U.S. Bureau of Aeronautics, the U.S. Weather Bureau, the California Institute of Technology, and the Guggenheim Airship Institute. Mr. R.C. Robinson of the Weather Bureau cooperated with the author in carrying out the investigation. The object of the investigation was to determine the intensity of the atmospheric disturbances (i.e. rapidity of wind shift and gustiness) accompanying the passage of cold fronts, along with a study of the characteristics of the air masses involved and other features which might affect the intensity of the disturbance. The report treated thirty cold fronts which passed the station during 1935 to 1936
Archives and Images as Repositories of Time, Language, and Forms from the Past: A Conversation with Daniel Eisenberg
Full text linkTipo de Weyl de perturbaciones de agujeros negros
Full text linkTesis (Lic. en Física)--Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física, 2014.Fil: Araneda, Bernardo Gabriel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.En este trabajo se estudian las perturbaciones lineales de soluciones algebráicamente
especiales de las ecuaciones de Einstein, en particular, espaciotiempos tipo Petrov D. Se
analiza la estructura de autovalores y las direcciones principales nulas de la geometrı́a
perturbada. Se demuestra que el espaciotiempo no retiene en general la especialidad algebraica bajo la perturbación, teniendo cuatro direcciones nulas que resultan no-analı́ticas en
el parámetro perturbativo, y que representan una bifurcación de los dos pares coincidentes
del background. Los resultados son válidos para todo espaciotiempo tipo D perturbado,
en particular para la familia de agujeros negros de Kerr-Newman. Se aplican estos resultados a perturbaciones genéricas del agujero negro de Schwarzschild, demostrándose que
las nuevas direcciones principales no pueden corresponder a modos armónicos puros de la
perturbación, y obteniendo un efecto claro del modo par sobre la geometrı́a.In this paper we study linear perturbations of algebraically special solutions of the Einstein equations, in particular, spacetimes of Petrov D type. The eigenvalue structure and principal null directions of the perturbed geometry are analyzed. It is shown that the spacetime does not retain in general the algebraic specialness under perturbation, having four null directions which turn out to be non-analytic in the perturbative parameter, and which represent a bifurcation of the two coincident pairs of the background. The results are valid for all perturbed D-type spacetimes, in particular for the Kerr-Newman family of black holes. We apply these results to generic perturbations of the Schwarzschild black hole, showing that the new principal directions cannot correspond to pure harmonic modes of the perturbation, and obtaining a clear effect of the even mode on the geometry.Fil: Araneda, Bernardo Gabriel. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina
Daniel Akech
Full text linkabstract: Daniel was a little boy when the war came to his village. He witnessed people being shot and running for shelter. There was no food or water so he drank urine and ate tree leaves.
“Lost Boys Found” is an ongoing, interdisciplinary project that is collecting, recording and archiving the oral histories of the Lost Boys/Girls of Sudan. The collection is a work-in-progress, seeking to record the oral history of as many Lost Boys/Girls as are willing, and will be used in a future book.Age: 24Region: Upper NileThis picture and bio was donated to the "Lost Boys Found" oral history project from The Arizona Lost Boys Cente
Daniel Emmett postcard
No full textPostcard of Daniel Emmett and his home in Mount Vernon, Ohio. Emmett is considered to be the author of the antebellum song "Dixie," written in 1859, which became the unofficial song of the Confederate soldiers during the American Civil War. He was born in Mount Vernon in 1815 and taught himself the fiddle, and later became associated with minstrel shows and helped to define that genre. Minstrel shows traveled around the United States, presenting skits and musical performances. Emmett also composed many other songs, including "Old Dan Tucker," "Turkey in the Straw," and "The Blue Tail Fly." He died in 1904
Daniel Jau Maper
Full text linkabstract: Daniel Jau Maper was herding cattle when Arabs attacked his village.
“Lost Boys Found” is an ongoing, interdisciplinary project that is collecting, recording and archiving the oral histories of the Lost Boys/Girls of Sudan. The collection is a work-in-progress, seeking to record the oral history of as many Lost Boys/Girls as are willing, and will be used in a future book.Age: 27Region: Upper NileThis picture and bio was donated to the "Lost Boys Found" oral history project from The Arizona Lost Boys Cente
Daniel A. Ngor
Full text linkWhen Daniel was five years old Arab soldiers attacked his village.
“Lost Boys Found” is an ongoing, interdisciplinary project that is collecting, recording and archiving the oral histories of the Lost Boys/Girls of Sudan. The collection is a work-in-progress, seeking to record the oral history of as many Lost Boys/Girls as are willing, and will be used in a future book.Age : 23Region: Upper NileThis picture and bio was donated to the "Lost Boys Found" oral history project from The Arizona Lost Boys Cente
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