Search

Your search keyword '"Kostas Kokkotas"' showing total 19 results
Start Over Author "Kostas Kokkotas"
19 results on '"Kostas Kokkotas"'

1. Astrophysics with the Laser Interferometer Space Antenna

Author

Pau Amaro-Seoane, Jeff Andrews, Manuel Arca Sedda, Abbas Askar, Quentin Baghi, Razvan Balasov, Imre Bartos, Simone S. Bavera, Jillian Bellovary, Christopher P. L. Berry, Emanuele Berti, Stefano Bianchi, Laura Blecha, Stéphane Blondin, Tamara Bogdanović, Samuel Boissier, Matteo Bonetti, Silvia Bonoli, Elisa Bortolas, Katelyn Breivik, Pedro R. Capelo, Laurentiu Caramete, Federico Cattorini, Maria Charisi, Sylvain Chaty, Xian Chen, Martyna Chruślińska, Alvin J. K. Chua, Ross Church, Monica Colpi, Daniel D’Orazio, Camilla Danielski, Melvyn B. Davies, Pratika Dayal, Alessandra De Rosa, Andrea Derdzinski, Kyriakos Destounis, Massimo Dotti, Ioana Duţan, Irina Dvorkin, Gaia Fabj, Thierry Foglizzo, Saavik Ford, Jean-Baptiste Fouvry, Alessia Franchini, Tassos Fragos, Chris Fryer, Massimo Gaspari, Davide Gerosa, Luca Graziani, Paul Groot, Melanie Habouzit, Daryl Haggard, Zoltan Haiman, Wen-Biao Han, Alina Istrate, Peter H. Johansson, Fazeel Mahmood Khan, Tomas Kimpson, Kostas Kokkotas, Albert Kong, Valeriya Korol, Kyle Kremer, Thomas Kupfer, Astrid Lamberts, Shane Larson, Mike Lau, Dongliang Liu, Nicole Lloyd-Ronning, Giuseppe Lodato, Alessandro Lupi, Chung-Pei Ma, Tomas Maccarone, Ilya Mandel, Alberto Mangiagli, Michela Mapelli, Stéphane Mathis, Lucio Mayer, Sean McGee, Berry McKernan, M. Coleman Miller, David F. Mota, Matthew Mumpower, Syeda S. Nasim, Gijs Nelemans, Scott Noble, Fabio Pacucci, Francesca Panessa, Vasileios Paschalidis, Hugo Pfister, Delphine Porquet, John Quenby, Angelo Ricarte, Friedrich K. Röpke, John Regan, Stephan Rosswog, Ashley Ruiter, Milton Ruiz, Jessie Runnoe, Raffaella Schneider, Jeremy Schnittman, Amy Secunda, Alberto Sesana, Naoki Seto, Lijing Shao, Stuart Shapiro, Carlos Sopuerta, Nicholas C. Stone, Arthur Suvorov, Nicola Tamanini, Tomas Tamfal, Thomas Tauris, Karel Temmink, John Tomsick, Silvia Toonen, Alejandro Torres-Orjuela, Martina Toscani, Antonios Tsokaros, Caner Unal, Verónica Vázquez-Aceves, Rosa Valiante, Maurice van Putten, Jan van Roestel, Christian Vignali, Marta Volonteri, Kinwah Wu, Ziri Younsi, Shenghua Yu, Silvia Zane, Lorenz Zwick, Fabio Antonini, Vishal Baibhav, Enrico Barausse, Alexander Bonilla Rivera, Marica Branchesi, Graziella Branduardi-Raymont, Kevin Burdge, Srija Chakraborty, Jorge Cuadra, Kristen Dage, Benjamin Davis, Selma E. de Mink, Roberto Decarli, Daniela Doneva, Stephanie Escoffier, Poshak Gandhi, Francesco Haardt, Carlos O. Lousto, Samaya Nissanke, Jason Nordhaus, Richard O’Shaughnessy, Simon Portegies Zwart, Adam Pound, Fabian Schussler, Olga Sergijenko, Alessandro Spallicci, Daniele Vernieri, and Alejandro Vigna-Gómez

Subjects
Black holes, Gravitational waves, Stellar remnants, Multi-messenger, Extreme mass ratio in-spirals, Atomic physics. Constitution and properties of matter, QC170-197
Abstract

Abstract The Laser Interferometer Space Antenna (LISA) will be a transformative experiment for gravitational wave astronomy, and, as such, it will offer unique opportunities to address many key astrophysical questions in a completely novel way. The synergy with ground-based and space-born instruments in the electromagnetic domain, by enabling multi-messenger observations, will add further to the discovery potential of LISA. The next decade is crucial to prepare the astrophysical community for LISA’s first observations. This review outlines the extensive landscape of astrophysical theory, numerical simulations, and astronomical observations that are instrumental for modeling and interpreting the upcoming LISA datastream. To this aim, the current knowledge in three main source classes for LISA is reviewed; ultra-compact stellar-mass binaries, massive black hole binaries, and extreme or interme-diate mass ratio inspirals. The relevant astrophysical processes and the established modeling techniques are summarized. Likewise, open issues and gaps in our understanding of these sources are highlighted, along with an indication of how LISA could help making progress in the different areas. New research avenues that LISA itself, or its joint exploitation with upcoming studies in the electromagnetic domain, will enable, are also illustrated. Improvements in modeling and analysis approaches, such as the combination of numerical simulations and modern data science techniques, are discussed. This review is intended to be a starting point for using LISA as a new discovery tool for understanding our Universe.

Published
2023
Full Text
View/download PDF

2. Dynamical behavior of the C -metric: Charged scalar fields, quasinormal modes, and superradiance

Author

Kyriakos Destounis, Giacomo Mascher, and Kostas Kokkotas

Subjects
High Energy Physics - Theory, High Energy Astrophysical Phenomena (astro-ph.HE), General Relativity and Quantum Cosmology, High Energy Physics - Theory (hep-th), FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Astrophysics - High Energy Astrophysical Phenomena
Abstract

The $C$-metric is a boost-symmetric spacetime solution to the vacuum Einstein field equations which describes black holes that are uniformly accelerated under the tension of a cosmic string. Only recently the thermodynamics of accelerating black holes and their modal stability against neutral scalar perturbations were concisely established. The generalization of accelerating black holes to incorporate an electric charge, namely the charged $C$-metric, possess three distinct families of quasinormal mode frequencies; the complex photon surface quasinormal modes associated with unstable null particles at the equatorial plane of the photon surface, the purely imaginary acceleration modes whose existence solely depends on the acceleration of spacetime and the purely imaginary near-extremal modes which dominate the dynamics of the ringdown at late times when the event and Cauchy horizon approach each other. We extend the quasinormal mode analysis to charged scalar fluctuations and find that the photon surface modes are continuously deformed with respect to their neutral counterpart as the scalar charge is increased. We further find that the acceleration and near-extremal families acquire an oscillation frequency when the scalar charge is introduced. Finally, we study the superradiant amplification of charged scalar monochromatic waves impinging charged accelerating black holes. We find that even though the frequency range of superradiant amplification is lessened due to the acceleration, the amplification factors are considerably elevated with respect to those transpiring in Reissner-Nordstr\"om black holes and are maximized when the scalar charge is significantly large., Comment: 12 pages, 8 figures, accepted for publication in PRD, updated references

Published
2022

3. Charged black holes in de Sitter space: superradiant amplification of charged scalar waves and resonant hyperradiation

Author

Kyriakos Destounis, Giacomo Mascher, and Kostas Kokkotas

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), High Energy Physics - Theory, General Relativity and Quantum Cosmology, High Energy Physics - Theory (hep-th), FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Astrophysics - High Energy Astrophysical Phenomena
Abstract

Black holes typically inhabit highly dynamical galactic environments and are frequently permeated by accretion media. The inevitable scattering of scalar, electromagnetic and gravitational waves off rotating and charged black holes provides a remarkable demonstration of the energy extraction and subsequent amplification of scattered waves under the expense of the compact object's rotational and electromagnetic energy; a phenomenon known as superradiance. Certain circumstances tremendously favor the energy extraction process in such extent that linear superradiant instabilities are triggered. We examine the superradiant amplification of monochromatic charged scalar fields impinging Reissner-Nordstr\"om-de Sitter black holes which are known to exhibit superradiantly unstable quasinormal modes. We find that even though the frequency range of superradiance is reduced when a positive cosmological constant is incorporated, the amplification factors are significantly elevated with respect to those occurring in Reissner-Nordstr\"om spacetime. Intriguingly, we confirm that the long-lived quasinormal resonances that reside in the superradiant regime induce resonant peaks when the wave's frequency matches the real part of the quasinormal mode, regardless of the spacetime's modal stability., Comment: 10 pages, 8 figures, accepted for publication in Physical Review D, fixed references

Published
2022

4. Slowly-rotating curved acoustic black holes: Quasinormal modes, Hawking-Unruh radiation and quasibound states

Author

Horacio Santana Vieira, Kyriakos Destounis, and Kostas Kokkotas

Subjects
General Relativity and Quantum Cosmology, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc)
Abstract

Astrophysical black holes are generally surrounded by accretion disks, galactic matter and the omnipresent cosmic microwave background radiation, thus allowing for the concurrent propagation of both gravitational and sound waves. Recently, acoustic black holes were embedded in Schwarzschild spacetime allowing for the coexistence of event and acoustic horizons. Here, we obtain a class of perturbative solutions to the field equations of the relativistic Gross-Pitaevskii and Yang-Mills theories, which describe sound waves propagating on a curved slowly-rotating acoustic black hole, akin to Lense-Thirring spacetime. We investigate the quasinormal mode frequencies, Hawking-Unruh radiation, and quasibound states. Our novel metric mimics the gravitational field of astrophysical compact objects in the limiting case of slow rotation, and therefore could, in principle, shed more light into the underlying classical and quantum physics of black holes through analog acoustic probes., Comment: 18 pages, 5 figures. Matches published version in PRD

Published
2021
Full Text
View/download PDF

5. Nonlinear evolution and non-uniqueness of scalarized neutron stars

Author

Jasbir Singh, Hao-Jui Kuan, Stoytcho Yazadjiev, Daniela Doneva, and Kostas Kokkotas

Subjects
High Energy Astrophysical Phenomena (astro-ph.HE), General Relativity and Quantum Cosmology, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), Astrophysics - High Energy Astrophysical Phenomena
Abstract

It was recently shown, that in a class of tensor-multi-scalar theories of gravity with a nontrivial target space metric, there exist scalarized neutron star solutions. An important property of these compact objects is that the scalar charge is zero and therefore, the binary pulsar experiments can not impose constraints based on the absence of scalar dipole radiation. Moreover, the structure of the solutions is very complicated. For a fixed central energy density up to three neutron star solutions can exist -- one general relativistic and two scalarized, that is quite different from the scalarization in other alternative theories of gravity. In the present paper we address the stability of these solutions using two independent approaches -- solving the linearized radial perturbation equations and performing nonlinear simulations in spherical symmetry. The results show that the change of stability occurs at the maximum mass models and all solutions before that point are stable. This leads to the interesting consequence that there exists a stable part of the scalarized branch close to the bifurcation point where the mass of the star increases with the decrease of the central energy density., Comment: 10 pages, 5 figures, 1 table

Published
2021
Full Text
View/download PDF

6. On black hole area quantization and echoes

Author

Andrew Coates, Kostas Kokkotas, Sebastian Völkel, Coates, Andrew, Volkel, Sebastian H., Kokkotas, Kostas D., College of Sciences, and Department of Physics

Subjects
General Relativity and Quantum Cosmology, Physics and Astronomy (miscellaneous), 010308 nuclear & particles physics, Astrophysics::High Energy Astrophysical Phenomena, 0103 physical sciences, Astronomy and astrophysics, Quantum science and technology, Physics, multidisciplinary, Physics, particles and fields, Black holes, Gravitational wave echoes, Gravitational waves, Area quantization, Quasinormal modes, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), 010306 general physics, 01 natural sciences
Abstract

In this work we argue that black hole area quantization of Bekenstein and Mukhanov should not give rise to measurable effects in terms of so-called gravitational wave echoes during black hole mergers. We outline that the quantum spectrum of a black hole should be washed out during and after black hole mergers, and hence one should not expect echoes in this scenario. The extreme broadening of the spectrum is due to the large particle emission rate during ringdown. Our results question key assumptions being made in recent literature on this topic., 12 pages, accepted for publication in classical and quantum gravity

Published
2022

7. Testing general relativity with present and future astrophysical observations

Author

Emanuele Berti, Enrico Barausse, Vitor Cardoso, Leonardo Gualtieri, Paolo Pani, Ulrich Sperhake, Leo C Stein, Norbert Wex, Kent Yagi, Tessa Baker, C P Burgess, Flávio S Coelho, Daniela Doneva, Antonio De Felice, Pedro G Ferreira, Paulo C C Freire, James Healy, Carlos Herdeiro, Michael Horbatsch, Burkhard Kleihaus, Antoine Klein, Kostas Kokkotas, Jutta Kunz, Pablo Laguna, Ryan N Lang, Tjonnie G F Li, Tyson Littenberg, Andrew Matas, Saeed Mirshekari, Hirotada Okawa, Eugen Radu, Richard O’Shaughnessy, Bangalore S Sathyaprakash, Chris Van Den Broeck, Hans A Winther, Helvi Witek, Mir Emad Aghili, Justin Alsing, Brett Bolen, Luca Bombelli, Sarah Caudill, Liang Chen, Juan Carlos Degollado, Ryuichi Fujita, Caixia Gao, Davide Gerosa, Saeed Kamali, Hector O Silva, João G Rosa, Laleh Sadeghian, Marco Sampaio, Hajime Sotani, and Miguel Zilhao

Published
2015
Full Text
View/download PDF

9. Gravitational Waves and Hydromagnetic Instabilities in Rotating Magnetized Neutron Stars

Author

Lasky, Paul D., Zink, Burkhard, and Kostas Kokkotas

Subjects
Astrophysics - Solar and Stellar Astrophysics, Astrophysics::High Energy Astrophysical Phenomena, Astrophysics::Solar and Stellar Astrophysics, FOS: Physical sciences, General Relativity and Quantum Cosmology (gr-qc), General Relativity and Quantum Cosmology, Solar and Stellar Astrophysics (astro-ph.SR)
Abstract

We perform nonlinear general relativistic ideal magnetohydrodynamic simulations of poloidal magnetic fields in rotating polytropic neutron stars. We have three primary goals: i) to understand the nature of magnetohydrodynamic instabilities inherent to poloidal magnetic fields in non-rotating and rotating neutron stars, ii) to explore the possible space of stable equilibrium configurations and iii) to understand gravitational wave emissions caused by the catastrophic reconfiguration of magnetic fields associated with giant magnetar flares. Our key physical contributions can be summarized as follows: i) gravitational waves from f-modes caused by magnetar flares are unlikely to be detected in the current or near-future generation of gravitational waves observatories, ii) gravitational waves from Alfven waves propagating inside the neutron star are more likely candidates, although this interpretation relies on the unknown damping time of these modes, iii) any magnetic field equilibria derived from our simulations are characterized as non-axisymmetric, with approximately 65% of their magnetic energy in the poloidal field, iv) rotation acts to separate the timescales of different instabilities in our system, with the varicose mode playing a more major role due to a delayed kink instability and v) despite the slowing growth rate of the kink mode, it is always present in our simulations, even for models where the rotational period is of the same order as the Alfven timescale., Comment: Submitted to Physical Review D. High resolution figures available on request

Published
2012
Full Text
View/download PDF

10. The transient gravitational-wave sky

Author

Nils, A, John, B, Krzystof, B, Sebastiano, B, Emanuele, B, Laura, C, Pablo Cerdá, D, James, C, Marc, F, Lee Samuel, F, Chris, F, Giacomazzo, B, Jose Antonio, G, Martin, H, Ik Siong, H, Stefan, H, Nathan Johnson, M, Peter, K, Sergei, K, Shiho, K, Kostas, K, Pablo, L, Luis, L, Janna, L, Steve, L, Andrew, M, Ilya, M, Szabolcs, M, Zsuzsa, M, David, N, Paul, O, Rosalba, P, Jocelyn, R, Christian, R, Carl, R, Max, R, Erik, S, Antony, S, Peter, S, Deirdre, S, Alicia, S, Ulrich, S, Patrick, S, Nial, T, Michal, W, Stan, W, Nils Andersson, John Baker, Krzystof Belczynski, Sebastiano Bernuzzi, Emanuele Berti, Laura Cadonati, Pablo Cerdá Durán, James Clark, Marc Favata, Lee Samuel Finn, Chris Fryer, Giacomazzo, Bruno, Jose Antonio González, Martin Hendry, Ik Siong Heng, Stefan Hild, Nathan Johnson McDaniel, Peter Kalmus, Sergei Klimenko, Shiho Kobayashi, Kostas Kokkotas, Pablo Laguna, Luis Lehner, Janna Levin, Steve Liebling, Andrew MacFadyen, Ilya Mandel, Szabolcs Marka, Zsuzsa Marka, David Neilsen, Paul O'Brien, Rosalba Perna, Jocelyn Read, Christian Reisswig, Carl Rodriguez, Max Ruffert, Erik Schnetter, Antony Searle, Peter Shawhan, Deirdre Shoemaker, Alicia Soderberg, Ulrich Sperhake, Patrick Sutton, Nial Tanvir, Michal Was, Stan Whitcomb, Nils, A, John, B, Krzystof, B, Sebastiano, B, Emanuele, B, Laura, C, Pablo Cerdá, D, James, C, Marc, F, Lee Samuel, F, Chris, F, Giacomazzo, B, Jose Antonio, G, Martin, H, Ik Siong, H, Stefan, H, Nathan Johnson, M, Peter, K, Sergei, K, Shiho, K, Kostas, K, Pablo, L, Luis, L, Janna, L, Steve, L, Andrew, M, Ilya, M, Szabolcs, M, Zsuzsa, M, David, N, Paul, O, Rosalba, P, Jocelyn, R, Christian, R, Carl, R, Max, R, Erik, S, Antony, S, Peter, S, Deirdre, S, Alicia, S, Ulrich, S, Patrick, S, Nial, T, Michal, W, Stan, W, Nils Andersson, John Baker, Krzystof Belczynski, Sebastiano Bernuzzi, Emanuele Berti, Laura Cadonati, Pablo Cerdá Durán, James Clark, Marc Favata, Lee Samuel Finn, Chris Fryer, Giacomazzo, Bruno, Jose Antonio González, Martin Hendry, Ik Siong Heng, Stefan Hild, Nathan Johnson McDaniel, Peter Kalmus, Sergei Klimenko, Shiho Kobayashi, Kostas Kokkotas, Pablo Laguna, Luis Lehner, Janna Levin, Steve Liebling, Andrew MacFadyen, Ilya Mandel, Szabolcs Marka, Zsuzsa Marka, David Neilsen, Paul O'Brien, Rosalba Perna, Jocelyn Read, Christian Reisswig, Carl Rodriguez, Max Ruffert, Erik Schnetter, Antony Searle, Peter Shawhan, Deirdre Shoemaker, Alicia Soderberg, Ulrich Sperhake, Patrick Sutton, Nial Tanvir, Michal Was, and Stan Whitcomb

Abstract

Interferometric detectors will very soon give us an unprecedented view of the gravitational-wave sky, and in particular of the explosive and transient Universe. Now is the time to challenge our theoretical understanding of short-duration gravitational-wave signatures from cataclysmic events, their connection to more traditional electromagnetic and particle astrophysics, and the data analysis techniques that will make the observations a reality. This paper summarizes the state of the art, future science opportunities, and current challenges in understanding gravitational-wave transients.

Published
2013

11. Non-linear Evolution of Rotating Relativistic Stars

Author

Stergioulas, N., Font, J. A., and Kostas Kokkotas

Subjects
Astrophysics (astro-ph), FOS: Physical sciences, Astrophysics::Earth and Planetary Astrophysics, General Relativity and Quantum Cosmology (gr-qc), Astrophysics, General Relativity and Quantum Cosmology
Abstract

We present first results of the non-linear evolution of rotating relativistic stars obtained with an axisymmetric relativistic hydrodynamics code in a fixed spacetime. As initial data we use stationary axisymmetric and perturbed configurations. We find that, in order to prevent (numerical) angular momentum loss at the surface layers of the star a high-resolution grid (or a numerical scheme that retains high order at local extrema) is needed. For non-rotating stars, we compute frequencies of radial and non-radial small-amplitude oscillations, which are in excellent agreement with linear normal mode frequencies computed in the Cowling approximation. As a first application of our code, quasi-radial modes of rapidly rotating relativistic stars are computed. By generalizing our numerical code to 3-D, we plan to study the evolution and non-linear dynamics of toroidal oscillations (r-modes) of rapidly rotating neutron stars, which are a promising source of gravitational waves., Comment: 12 pages, 4 figures, Contribution to the 19th Texas Symposium

Published
1999
Full Text
View/download PDF

12. Corrigendum: Scientific objectives of Einstein telescope

Author

Bangalore Sathyaprakash, Pau Amaro Seoane, Bernard Schutz, Carlos F. Sopuerta, Marc Favata, Tomasz Bulik, Walter Del Pozzo, and Kostas Kokkotas

Subjects
Physics, Physics and Astronomy (miscellaneous), Einstein Telescope, Astronomy
Published
2013

14. W-Modes: A New Family of Normal Modes of Pulsating Relativistic Stars

Author

Kostas Kokkotas and Schutz, B. F.

Subjects
General Relativity and Quantum Cosmology, Astrophysics::High Energy Astrophysical Phenomena
Abstract

A new family of outgoing-wave normal modes of pulsating relativistic stars which have no Newtonian analogues is demonstrated. These modes, named w-modes, are primarily oscillations of the space-time metric in which the fluid hardly vibrates at all. They are characterized by complex frequencies with unusually large imaginary parts, comparable to their real parts. A sequence of l = 2 modes is calculated for a number of spherical polytropic stellar models. The lowest order mode of each sequence has a frequency similar to that of a spherical black hole. For higher modes, the spectrum diverges from the black-hole spectrum, but shows remarkable similarity to that of the strongly damped modes of the toy problem. These modes are considered to be important and observable in the burst of gravitational radiation that follows the formation of a neutron star.

15. Pathway to the Square Kilometre Array - The German White Paper

Author

Aharonian, F., Arshakian, T. G., Allen, B., Banerjee, R., Beck, R., Becker, W., Bomans, D. J., Breitschwerdt, D., Brüggen, M., Brunthaler, A., Catinella, B., Champion, D., Ciardi, B., Crocker, R., Avillez, M. A., Dettmar, R. J., Engels, D., Enßlin, T., Enke, H., Fieseler, T., Gizon, L., Hackmann, E., Hartmann, B., Henkel, C., Hoeft, M., Iapichino, L., Innes, D., James, C., Jasche, J., Jones, D., Kagramanova, V., Kauffmann, G., Keane, E., Kerp, J., Klöckner, H. -R, Kostas Kokkotas, Kramer, M., Krause, M., Krupp, N., Kunz, J., Lämmerzahl, C., Lee, K. J., List, M., Liu, K., Lobanov, A., Mann, G., Merloni, A., Middelberg, E., Niemeyer, J., Noutsos, A., Perlick, V., Reich, W., Richter, P., Roy, A., Saintonge, A., Schäfer, G., Schaffner-Bielich, J., Schinnerer, E., Schleicher, D., Schneider, P., Schwarz, D. J., Sedrakian, A., Sesana, A., Smolčić, V., Solanki, S., Tuffs, R., Vetter, M., Weber, E., Weller, J., Wex, N., Wucknitz, O., and Zwaan, M.

Subjects
Physics - Instrumentation and Detectors, FOS: Physical sciences, Instrumentation and Detectors (physics.ins-det), Astrophysics - Instrumentation and Methods for Astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM)
Abstract

The Square Kilometre Array (SKA) is the most ambitious radio telescope ever planned. With a collecting area of about a square kilometre, the SKA will be far superior in sensitivity and observing speed to all current radio facilities. The scientific capability promised by the SKA and its technological challenges provide an ideal base for interdisciplinary research, technology transfer, and collaboration between universities, research centres and industry. The SKA in the radio regime and the European Extreme Large Telescope (E-ELT) in the optical band are on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI) and have been recognised as the essential facilities for European research in astronomy. This "White Paper" outlines the German science and R&D interests in the SKA project and will provide the basis for future funding applications to secure German involvement in the Square Kilometre Array., Editors: H. R. Kl\"ockner, M. Kramer, H. Falcke, D.J. Schwarz, A. Eckart, G. Kauffmann, A. Zensus; 150 pages (low resolution- and colour-scale images), published in July 2012, language English (including a foreword and an executive summary in German), the original file is available via the MPIfR homepage

16. Torsional Oscillations of Relativistic Stars with Dipole Magnetic Fields II. Global Alfv\'en Modes

Author

Sotani, H., Kostas Kokkotas, Stergioulas, N., and Vavoulidis, M.

Subjects
Astrophysics::High Energy Astrophysical Phenomena, Astrophysics, General Relativity and Quantum Cosmology
Abstract

We investigate torsional Alfv\'{e}n modes of relativistic stars with a global dipole magnetic field. It has been noted recently (Glampedakis et al. 2006) that such oscillation modes could serve as as an alternative explanation (in contrast to torsional crustal modes) for the SGR phenomenon, if the magnetic field is not confined to the crust. We compute global Alfv\'{e}n modes for a representative sample of equations of state and magnetar masses, in the ideal MHD approximation and ignoring $\ell \pm 2$ terms in the eigenfunction. We find that the presence of a realistic crust has a negligible effect on Alfv\'{e}n modes for $B > 4\times 10^{15}$ G. Furthermore, we find strong avoided crossings between torsional Alfv\'{e}n modes and torsional crust modes. For magnetar-like magnetic field strengths, the spacing between consecutive Alfv\'{e}n modes is of the same order as the gap of avoided crossings. As a result, it is not possible to identify modes of predominantly crustal character and all oscillations are predominantly Alfv\'{e}n-like. Interestingly, we find excellent agreement between our computed frequencies and observed frequencies in two SGRs, for a maximum magnetic field strenght in the range of (0.8--1.2)$\times 10^{16}$ G., Comment: 13 pages, 8 figures

19. Black holes, gravitational waves and fundamental physics: a roadmap

Author

Leor Barack, Vitor Cardoso, Samaya Nissanke, Thomas P Sotiriou, Abbas Askar, Chris Belczynski, Gianfranco Bertone, Edi Bon, Diego Blas, Richard Brito, Tomasz Bulik, Clare Burrage, Christian T Byrnes, Chiara Caprini, Masha Chernyakova, Piotr Chruściel, Monica Colpi, Valeria Ferrari, Daniele Gaggero, Jonathan Gair, Juan García-Bellido, S F Hassan, Lavinia Heisenberg, Martin Hendry, Ik Siong Heng, Carlos Herdeiro, Tanja Hinderer, Assaf Horesh, Bradley J Kavanagh, Bence Kocsis, Michael Kramer, Alexandre Le Tiec, Chiara Mingarelli, Germano Nardini, Gijs Nelemans, Carlos Palenzuela, Paolo Pani, Albino Perego, Edward K Porter, Elena M Rossi, Patricia Schmidt, Alberto Sesana, Ulrich Sperhake, Antonio Stamerra, Leo C Stein, Nicola Tamanini, Thomas M Tauris, L Arturo Urena-López, Frederic Vincent, Marta Volonteri, Barry Wardell, Norbert Wex, Kent Yagi, Tiziano Abdelsalhin, Miguel Ángel Aloy, Pau Amaro-Seoane, Lorenzo Annulli, Manuel Arca-Sedda, Ibrahima Bah, Enrico Barausse, Elvis Barakovic, Robert Benkel, Charles L Bennett, Laura Bernard, Sebastiano Bernuzzi, Christopher P L Berry, Emanuele Berti, Miguel Bezares, Jose Juan Blanco-Pillado, Jose Luis Blázquez-Salcedo, Matteo Bonetti, Mateja Bošković, Zeljka Bosnjak, Katja Bricman, Bernd Brügmann, Pedro R Capelo, Sante Carloni, Pablo Cerdá-Durán, Christos Charmousis, Sylvain Chaty, Aurora Clerici, Andrew Coates, Marta Colleoni, Lucas G Collodel, Geoffrey Compère, William Cook, Isabel Cordero-Carrión, Miguel Correia, Álvaro de la Cruz-Dombriz, Viktor G Czinner, Kyriakos Destounis, Kostas Dialektopoulos, Daniela Doneva, Massimo Dotti, Amelia Drew, Christopher Eckner, James Edholm, Roberto Emparan, Recai Erdem, Miguel Ferreira, Pedro G Ferreira, Andrew Finch, Jose A Font, Nicola Franchini, Kwinten Fransen, Dmitry Gal’tsov, Apratim Ganguly, Davide Gerosa, Kostas Glampedakis, Andreja Gomboc, Ariel Goobar, Leonardo Gualtieri, Eduardo Guendelman, Francesco Haardt, Troels Harmark, Filip Hejda, Thomas Hertog, Seth Hopper, Sascha Husa, Nada Ihanec, Taishi Ikeda, Amruta Jaodand, Philippe Jetzer, Xisco Jimenez-Forteza, Marc Kamionkowski, David E Kaplan, Stelios Kazantzidis, Masashi Kimura, Shiho Kobayashi, Kostas Kokkotas, Julian Krolik, Jutta Kunz, Claus Lämmerzahl, Paul Lasky, José P S Lemos, Jackson Levi Said, Stefano Liberati, Jorge Lopes, Raimon Luna, Yin-Zhe Ma, Elisa Maggio, Alberto Mangiagli, Marina Martinez Montero, Andrea Maselli, Lucio Mayer, Anupam Mazumdar, Christopher Messenger, Brice Ménard, Masato Minamitsuji, Christopher J Moore, David Mota, Sourabh Nampalliwar, Andrea Nerozzi, David Nichols, Emil Nissimov, Martin Obergaulinger, Niels A Obers, Roberto Oliveri, George Pappas, Vedad Pasic, Hiranya Peiris, Tanja Petrushevska, Denis Pollney, Geraint Pratten, Nemanja Rakic, Istvan Racz, Miren Radia, Fethi M Ramazanoğlu, Antoni Ramos-Buades, Guilherme Raposo, Marek Rogatko, Roxana Rosca-Mead, Dorota Rosinska, Stephan Rosswog, Ester Ruiz-Morales, Mairi Sakellariadou, Nicolás Sanchis-Gual, Om Sharan Salafia, Anuradha Samajdar, Alicia Sintes, Majda Smole, Carlos Sopuerta, Rafael Souza-Lima, Marko Stalevski, Nikolaos Stergioulas, Chris Stevens, Tomas Tamfal, Alejandro Torres-Forné, Sergey Tsygankov, Kıvanç İ Ünlütürk, Rosa Valiante, Maarten van de Meent, José Velhinho, Yosef Verbin, Bert Vercnocke, Daniele Vernieri, Rodrigo Vicente, Vincenzo Vitagliano, Amanda Weltman, Bernard Whiting, Andrew Williamson, Helvi Witek, Aneta Wojnar, Kadri Yakut, Haopeng Yan, Stoycho Yazadjiev, Gabrijela Zaharijas, Miguel Zilhão, AstroParticule et Cosmologie (APC (UMR_7164)), Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), Institut des Hautes Etudes Scientifiques (IHES), IHES, Laboratoire Univers et Théories (LUTH (UMR_8102)), Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire d'études spatiales et d'instrumentation en astrophysique (LESIA (UMR_8109)), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Physique Théorique d'Orsay [Orsay] (LPT), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR_7158 / UMR_E_9005 / UM_112)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut des Hautes Études Scientifiques (IHES), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Astrophysique Interprétation Modélisation (AIM (UMR7158 / UMR_E_9005 / UM_112)), Barack, L., Cardoso, V., Nissanke, S., Sotiriou, T. P., Askar, A., Belczynski, C., Bertone, G., Bon, E., Blas, D., Brito, R., Bulik, T., Burrage, C., Byrnes, C. T., Caprini, C., Chernyakova, M., Chrusciel, P., Colpi, M., Ferrari, V., Gaggero, D., Gair, J., Garcia-Bellido, J., Hassan, S. F., Heisenberg, L., Hendry, M., Heng, I. S., Herdeiro, C., Hinderer, T., Horesh, A., Kavanagh, B. J., Kocsis, B., Kramer, M., Le Tiec, A., Mingarelli, C., Nardini, G., Nelemans, G., Palenzuela, C., Pani, P., Perego, A., Porter, E. K., Rossi, E. M., Schmidt, P., Sesana, A., Sperhake, U., Stamerra, A., Stein, L. C., Tamanini, N., Tauris, T. M., Urena-Lopez, L. A., Vincent, F., Volonteri, M., Wardell, B., Wex, N., Yagi, K., Abdelsalhin, T., Aloy, M. A., Amaro-Seoane, P., Annulli, L., Arca-Sedda, M., Bah, I., Barausse, E., Barakovic, E., Benkel, R., Bennett, C. L., Bernard, L., Bernuzzi, S., Berry, C. P. L., Berti, E., Bezares, M., Blanco-Pillado, J. J., Blazquez-Salcedo, J. L., Bonetti, M., Boskovic, M., Bosnjak, Z., Bricman, K., Brugmann, B., Capelo, P. R., Carloni, S., Cerda-Duran, P., Charmousis, C., Chaty, S., Clerici, A., Coates, A., Colleoni, M., Collodel, L. G., Compere, G., Cook, W., Cordero-Carrion, I., Correia, M., De La Cruz-Dombriz, A., Czinner, V. G., Destounis, K., Dialektopoulos, K., Doneva, D., Dotti, M., Drew, A., Eckner, C., Edholm, J., Emparan, R., Erdem, R., Ferreira, M., Ferreira, P. G., Finch, A., Font, J. A., Franchini, N., Fransen, K., Gal'Tsov, D., Ganguly, A., Gerosa, D., Glampedakis, K., Gomboc, A., Goobar, A., Gualtieri, L., Guendelman, E., Haardt, F., Harmark, T., Hejda, F., Hertog, T., Hopper, S., Husa, S., Ihanec, N., Ikeda, T., Jaodand, A., Jetzer, P., Jimenez-Forteza, X., Kamionkowski, M., Kaplan, D. E., Kazantzidis, S., Kimura, M., Kobayashi, S., Kokkotas, K., Krolik, J., Kunz, J., Lammerzahl, C., Lasky, P., Lemos, J. P. S., Levi Said, J., Liberati, S., Lopes, J., Luna, R., Ma, Y. -Z., Maggio, E., Mangiagli, A., Montero, M. M., Maselli, A., Mayer, L., Mazumdar, A., Messenger, C., Menard, B., Minamitsuji, M., Moore, C. J., Mota, D., Nampalliwar, S., Nerozzi, A., Nichols, D., Nissimov, E., Obergaulinger, M., Obers, N. A., Oliveri, R., Pappas, G., Pasic, V., Peiris, H., Petrushevska, T., Pollney, D., Pratten, G., Rakic, N., Racz, I., Radia, M., Ramazanoglu, F. M., Ramos-Buades, A., Raposo, G., Rogatko, M., Rosca-Mead, R., Rosinska, D., Rosswog, S., Ruiz-Morales, E., Sakellariadou, M., Sanchis-Gual, N., Sharan Salafia, O., Samajdar, A., Sintes, A., Smole, M., Sopuerta, C., Souza-Lima, R., Stalevski, M., Stergioulas, N., Stevens, C., Tamfal, T., Torres-Forne, A., Tsygankov, S., I Unluturk, Ki., Valiante, R., Van De Meent, M., Velhinho, J., Verbin, Y., Vercnocke, B., Vernieri, D., Vicente, R., Vitagliano, V., Weltman, A., Whiting, B., Williamson, A., Witek, H., Wojnar, A., Yakut, K., Yan, H., Yazadjiev, S., Zaharijas, G., Zilhao, M., Gravitation and Astroparticle Physics Amsterdam, GRAPPA (ITFA, IoP, FNWI), IoP (FNWI), High Energy Astrophys. & Astropart. Phys (API, FNWI), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Université Paris-Sud - Paris 11 (UP11), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7), Sperhake, Ulrich [0000-0002-3134-7088], Drew, Amelia [0000-0001-8252-602X], Radia, Miren [0000-0001-8861-2025], Apollo - University of Cambridge Repository, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Ege Üniversitesi, Barack, L, Cardoso, V, Nissanke, S, Sotiriou, T, Askar, A, Belczynski, C, Bertone, G, Bon, E, Blas, D, Brito, R, Bulik, T, Burrage, C, Byrnes, C, Caprini, C, Chernyakova, M, Chruściel, P, Colpi, M, Ferrari, V, Gaggero, D, Gair, J, García-Bellido, J, Hassan, S, Heisenberg, L, Hendry, M, Heng, I, Herdeiro, C, Hinderer, T, Horesh, A, Kavanagh, B, Kocsis, B, Kramer, M, Le Tiec, A, Mingarelli, C, Nardini, G, Nelemans, G, Palenzuela, C, Pani, P, Perego, A, Porter, E, Rossi, E, Schmidt, P, Sesana, A, Sperhake, U, Stamerra, A, Stein, L, Tamanini, N, Tauris, T, Urena-López, L, Vincent, F, Volonteri, M, Wardell, B, Wex, N, Yagi, K, Abdelsalhin, T, Aloy, M, Amaro-Seoane, P, Annulli, L, Arca-Sedda, M, Bah, I, Barausse, E, Barakovic, E, Benkel, R, Bennett, C, Bernard, L, Bernuzzi, S, Berry, C, Berti, E, Bezares, M, Blanco-Pillado, J, Blázquez-Salcedo, J, Bonetti, M, Bošković, M, Bosnjak, Z, Bricman, K, Brügmann, B, Capelo, P, Carloni, S, Cerdá-Durán, P, Charmousis, C, Chaty, S, Clerici, A, Coates, A, Colleoni, M, Collodel, L, Compère, G, Cook, W, Cordero-Carrión, I, Correia, M, de la Cruz-Dombriz, Á, Czinner, V, Destounis, K, Dialektopoulos, K, Doneva, D, Dotti, M, Drew, A, Eckner, C, Edholm, J, Emparan, R, Erdem, R, Ferreira, M, Ferreira, P, Finch, A, Font, J, Franchini, N, Fransen, K, Gal’Tsov, D, Ganguly, A, Gerosa, D, Glampedakis, K, Gomboc, A, Goobar, A, Gualtieri, L, Guendelman, E, Haardt, F, Harmark, T, Hejda, F, Hertog, T, Hopper, S, Husa, S, Ihanec, N, Ikeda, T, Jaodand, A, Jetzer, P, Jimenez-Forteza, X, Kamionkowski, M, Kaplan, D, Kazantzidis, S, Kimura, M, Kobayashi, S, Kokkotas, K, Krolik, J, Kunz, J, Lämmerzahl, C, Lasky, P, Lemos, J, Levi Said, J, Liberati, S, Lopes, J, Luna, R, Ma, Y, Maggio, E, Mangiagli, A, Montero, M, Maselli, A, Mayer, L, Mazumdar, A, Messenger, C, Ménard, B, Minamitsuji, M, Moore, C, Mota, D, Nampalliwar, S, Nerozzi, A, Nichols, D, Nissimov, E, Obergaulinger, M, Obers, N, Oliveri, R, Pappas, G, Pasic, V, Peiris, H, Petrushevska, T, Pollney, D, Pratten, G, Rakic, N, Racz, I, Radia, M, Ramazanoğlu, F, Ramos-Buades, A, Raposo, G, Rogatko, M, Rosca-Mead, R, Rosinska, D, Rosswog, S, Ruiz-Morales, E, Sakellariadou, M, Sanchis-Gual, N, Sharan Salafia, O, Samajdar, A, Sintes, A, Smole, M, Sopuerta, C, Souza-Lima, R, Stalevski, M, Stergioulas, N, Stevens, C, Tamfal, T, Torres-Forné, A, Tsygankov, S, İ Ünlütürk, K, Valiante, R, van de Meent, M, Velhinho, J, Verbin, Y, Vercnocke, B, Vernieri, D, Vicente, R, Vitagliano, V, Weltman, A, Whiting, B, Williamson, A, Witek, H, Wojnar, A, Yakut, K, Yan, H, Yazadjiev, S, Zaharijas, G, and Zilhão, M

Subjects
High Energy Physics - Theory, cosmological model, Physics and Astronomy (miscellaneous), Event horizon, Astronomy, 01 natural sciences, General Relativity and Quantum Cosmology, Cosmology, Physics, Particles & Fields, Gravitation, High Energy Physics::Theory, black hole: formation, Vacuum energy, black hole, general relativity, NEUTRON-STAR, GENERAL-RELATIVITY, dark energy, STAR CLUSTER SIMULATIONS, gravitational wave, QC, QB, media_common, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, astro-ph.HE, Quantum Science & Technology, [PHYS.HTHE]Physics [physics]/High Energy Physics - Theory [hep-th], hep-th, source modelling, BRANS-DICKE THEORY, fundamental physic, gravitational waves, QUASI-NORMAL MODES, Physical Sciences, birth and evolution of black holes, black holes, fundamental physics, gravitational-wave astronomy, [PHYS.GRQC]Physics [physics]/General Relativity and Quantum Cosmology [gr-qc], HIGH-REDSHIFT FORMATION, Astrophysics - High Energy Astrophysical Phenomena, SCALAR-TENSOR THEORIES, General relativity, media_common.quotation_subject, gr-qc, Physics, Multidisciplinary, birth and evolution of black hole, FOS: Physical sciences, ST/R00045X/1, General Relativity and Quantum Cosmology (gr-qc), Astronomy & Astrophysics, gravitational radiation: direct detection, horizon, vacuum state: energy, Theoretical physics, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, inflation, 010306 general physics, STFC, Science & Technology, 010308 nuclear & particles physics, Gravitational wave, Physique, gravitational radiation, RCUK, ST/P000703/1, R-PROCESS NUCLEOSYNTHESIS, Astronomie, singularity, Universe, High Energy Physics - Theory (hep-th), gravitation, black hole: model, TIMING ARRAY LIMITS, Dark energy, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], X-RAY BINARIES
Abstract

The grand challenges of contemporary fundamental physics-dark matter, dark energy, vacuum energy, inflation and early universe cosmology, singularities and the hierarchy problem-all involve gravity as a key component. And of all gravitational phenomena, black holes stand out in their elegant simplicity, while harbouring some of the most remarkable predictions of General Relativity: event horizons, singularities and ergoregions. The hitherto invisible landscape of the gravitational Universe is being unveiled before our eyes: the historical direct detection of gravitational waves by the LIGO-Virgo collaboration marks the dawn of a new era of scientific exploration. Gravitational-wave astronomy will allow us to test models of black hole formation, growth and evolution, as well as models of gravitational-wave generation and propagation. It will provide evidence for event horizons and ergoregions, test the theory of General Relativity itself, and may reveal the existence of new fundamental fields. The synthesis of these results has the potential to radically reshape our understanding of the cosmos and of the laws of Nature. The purpose of this work is to present a concise, yet comprehensive overview of the state of the art in the relevant fields of research, summarize important open problems, and lay out a roadmap for future progress. This write-up is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'., SCOPUS: re.j, info:eu-repo/semantics/published

Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results