Author
Eleftherios Papantonopoulos
Other affiliations: Shanghai Jiao Tong University, National Technical University, Institute of Cosmology and Gravitation, University of Portsmouth ...read more
Bio: Eleftherios Papantonopoulos is an academic researcher from National Technical University of Athens. The author has contributed to research in topics: Scalar field & Black hole. The author has an hindex of 40, co-authored 204 publications receiving 5762 citations. Previous affiliations of Eleftherios Papantonopoulos include Shanghai Jiao Tong University & National Technical University.
Topics: Scalar field, Black hole, Brane, Induced gravity, Einstein tensor
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the authors studied the effects of the mass of the scalar field, the Gauss-Bonnet coupling and the dimensionality of the AdS space on the condensation formation and conductivity of superconductors.
Abstract: We study holographic superconductors in Einstein-Gauss-Bonnet gravity. We consider two particular backgrounds: a $d$-dimensional Gauss-Bonnet-AdS black hole and a Gauss-Bonnet-AdS soliton. We discuss in detail the effects that the mass of the scalar field, the Gauss-Bonnet coupling and the dimensionality of the AdS space have on the condensation formation and conductivity. We also study the ratio ${\ensuremath{\omega}}_{g}/{T}_{c}$ for various masses of the scalar field and Gauss-Bonnet couplings.
240 citations
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TL;DR: In this article, the slow-roll inflationary dynamics in a self-gravitating induced gravity braneworld model with a bulk cosmological constant was studied and important corrections to the four-dimensional Friedmann equation were found.
Abstract: We study the slow-roll inflationary dynamics in a self-gravitating induced gravity braneworld model with a bulk cosmological constant. For we find important corrections to the four-dimensional Friedmann equation which bring the standard chaotic inflationary scenario into closer agreement with recent observations. For we find five-dimensional corrections to the Friedmann equation, which give the known Randall–Sundrum results for the inflationary parameters.
131 citations
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TL;DR: In this paper, a higher order version of Horndeski's four-dimensional action is considered and a conformally invariant version of the BBMB action is constructed for planar horizon geometry embedded in anti de Sitter space.
Abstract: We study certain bi-scalar-tensor theories emanating from conformal symmetry requirements of Horndeski’s four-dimensional action. The former scalar is a Galileon with shift symmetry whereas the latter scalar is adjusted to have a higher order conformal coupling. Employing techniques from local Weyl geometry certain Galileon higher order terms are thus constructed to be conformally invariant. The combined shift and partial conformal symmetry of the action, allow us to construct exact black hole solutions. The black holes initially found are of planar horizon geometry embedded in anti de Sitter space and can accommodate electric charge. The conformally coupled scalar comes with an additional independent charge and it is well-defined on the horizon whereas additional regularity of the Galileon field is achieved allowing for time dependence. Guided by our results in adS space-time we then consider a higher order version of the BBMB action and construct asymptotically flat, regular, hairy black holes. The addition of the Galileon field is seen to cure the BBMB scalar horizon singularity while allowing for the presence of primary scalar hair seen as an independent integration constant along-side the mass of the black hole.
126 citations
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TL;DR: In this paper, the Horndeski and the Galileon Theories are combined with the Vainshtein Mechanism and the Chern-Simons Theories for a modified version of General Scalar Tensor Theories.
Abstract: Part I Modification of GR: General Scalar-Tensor Theories.- Gravity and Scalar Fields.- Cosmological Perturbations in the Most General Scalar-Tensor Theories l- Introduction to the Horndeski and the Galileon Theories.- Horndeski Theory and Cosmological Constant.- Part II Massive Gravity.- Introduction to Massive Gravity.- New Massive Gravity.- Topologically Massive Gravity.- Introduction to the Vainshtein Mechanism.- Black Hole Solutions in Massive Gravity.- Cosmological Applications of Massive Gravity.- Part III Other Modifications.- High Curvature Gravity Theories.- Higher Spin Theories.- Higher Spin Black Holes.- Introduction to Chern-Simons Theories.- Holographic Chern-Simons Theories.- Beyond Supergravity in AdS/CFT.- Holographic Perfect Fluidity, TMG and Gravitational Duality.- Patr IV Overview.- Modified Gravity: an Overview.
126 citations
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TL;DR: The major concepts and results recently achieved in the study of the structure and dynamics of complex networks are reviewed, and the relevant applications of these ideas in many different disciplines are summarized, ranging from nonlinear science to biology, from statistical mechanics to medicine and engineering.
9,441 citations
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TL;DR: The first direct detection of gravitational waves and the first observation of a binary black hole merger were reported in this paper, with a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ.
Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.
4,375 citations
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TL;DR: In this article, the authors present a review of the most important aspects of the different classes of modified gravity theories, including higher-order curvature invariants and metric affine.
Abstract: Modified gravity theories have received increased attention lately due to combined motivation coming from high-energy physics, cosmology, and astrophysics. Among numerous alternatives to Einstein's theory of gravity, theories that include higher-order curvature invariants, and specifically the particular class of $f(R)$ theories, have a long history. In the last five years there has been a new stimulus for their study, leading to a number of interesting results. Here $f(R)$ theories of gravity are reviewed in an attempt to comprehensively present their most important aspects and cover the largest possible portion of the relevant literature. All known formalisms are presented---metric, Palatini, and metric affine---and the following topics are discussed: motivation; actions, field equations, and theoretical aspects; equivalence with other theories; cosmological aspects and constraints; viability criteria; and astrophysical applications.
4,027 citations
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TL;DR: A comprehensive survey of recent work on modified theories of gravity and their cosmological consequences can be found in this article, where the authors provide a reference tool for researchers and students in cosmology and gravitational physics, as well as a selfcontained, comprehensive and up-to-date introduction to the subject as a whole.
3,674 citations
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TL;DR: In this article, the authors report on the implications for cosmic inflation of the 2018 Release of the Planck CMB anisotropy measurements, which are fully consistent with the two previous Planck cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles.
Abstract: We report on the implications for cosmic inflation of the 2018 Release of the Planck CMB anisotropy measurements. The results are fully consistent with the two previous Planck cosmological releases, but have smaller uncertainties thanks to improvements in the characterization of polarization at low and high multipoles. Planck temperature, polarization, and lensing data determine the spectral index of scalar perturbations to be $n_\mathrm{s}=0.9649\pm 0.0042$ at 68% CL and show no evidence for a scale dependence of $n_\mathrm{s}.$ Spatial flatness is confirmed at a precision of 0.4% at 95% CL with the combination with BAO data. The Planck 95% CL upper limit on the tensor-to-scalar ratio, $r_{0.002}<0.10$, is further tightened by combining with the BICEP2/Keck Array BK15 data to obtain $r_{0.002}<0.056$. In the framework of single-field inflationary models with Einstein gravity, these results imply that: (a) slow-roll models with a concave potential, $V" (\phi) < 0,$ are increasingly favoured by the data; and (b) two different methods for reconstructing the inflaton potential find no evidence for dynamics beyond slow roll. Non-parametric reconstructions of the primordial power spectrum consistently confirm a pure power law. A complementary analysis also finds no evidence for theoretically motivated parameterized features in the Planck power spectrum, a result further strengthened for certain oscillatory models by a new combined analysis that includes Planck bispectrum data. The new Planck polarization data provide a stringent test of the adiabaticity of the initial conditions. The polarization data also provide improved constraints on inflationary models that predict a small statistically anisotropic quadrupolar modulation of the primordial fluctuations. However, the polarization data do not confirm physical models for a scale-dependent dipolar modulation.
3,438 citations