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Jacob Oost

Bio: Jacob Oost is an academic researcher from Baylor University. The author has contributed to research in topics: Einstein aether theory & General relativity. The author has an hindex of 3, co-authored 6 publications receiving 109 citations.

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TL;DR: In this paper, the authors carried out a systematic analysis of the theoretical and observational constraints on the dimensionless coupling constants of the Einstein-aether theory, taking into account the events GW170817 and GRB 170817A.
Abstract: In this paper, we carry out a systematic analysis of the theoretical and observational constraints on the dimensionless coupling constants $c_i$ ($i=1,2,3,4$) of the Einstein-aether theory, taking into account the events GW170817 and GRB 170817A The combination of these events restricts the deviation of the speed $c_T$ of the spin-2 graviton to the range, $- 3\times 10^{-15} < c_T -1 < 7\times 10^{-16}$, which for the Einstein-aether theory implies $\left|c_{13}\right| \le 10^{-15}$ with $c_{ij} \equiv c_{i} + c_{j}$ The rest of the constraints are divided into two groups: those on the ($c_1, c_{14}$)-plane and those on the ($c_2, c_{14}$)-plane, except the strong-field constraints The latter depend on the sensitivities $\sigma_ae$ of neutron stars, which are not known at present in the new ranges of the parameters found in this paper

106 citations

Journal ArticleDOI
TL;DR: In this article, the authors systematically studied spacetimes of gravitational plane waves in Einstein-aether theory and found that there exist eight cases, in two of which any form of GPs can exist, similar to that in general relativity, while in the other six cases, GPs exist only in particular forms.
Abstract: In this paper, we systematically study spacetimes of gravitational plane waves in Einstein-aether theory. Due to the presence of the timelike aether vector field, now the problem in general becomes overdetermined. In particular, for the linearly polarized plane waves, there are five independent vacuum Einstein-aether field equations for three unknown functions. Therefore, solutions exist only for particular choices of the four free parameters $$c_{i}$$ ’s of the theory. We find that there exist eight cases, in two of which any form of gravitational plane waves can exist, similar to that in general relativity, while in the other six cases, gravitational plane waves exist only in particular forms. Beyond these eight cases, solutions either do not exist or are trivial (simply representing a Minkowski spacetime with a constant or dynamical aether field).

11 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied spherically symmetric spacetimes in Einstein-aether theory in three different coordinate systems, the isotropic, Painleve-Gullstrand, and Schwarzschild coordinates, in which the aether is always comoving, and presented both time-dependent and time-independent exact vacuum solutions.
Abstract: We study spherically symmetric spacetimes in Einstein-aether theory in three different coordinate systems, the isotropic, Painleve-Gullstrand, and Schwarzschild coordinates, in which the aether is always comoving, and present both time-dependent and time-independent exact vacuum solutions. In particular, in the isotropic coordinates we find a class of exact static solutions characterized by a single parameter $c_{14}$ in closed forms, which satisfies all the current observational constraints of the theory, and reduces to the Schwarzschild vacuum black hole solution in the decoupling limit ($c_{14} = 0$). However, as long as $c_{14} ot= 0$, a marginally trapped throat with a finite non-zero radius always exists, and in one side of it the spacetime is asymptotically flat, while in the other side the spacetime becomes singular within a finite proper distance from the throat, although the geometric area is infinitely large at the singularity. Moreover, the singularity is a strong and spacetime curvature singularity, at which both of the Ricci and Kretschmann scalars become infinitely large.

9 citations

Posted Content
03 Apr 2018
TL;DR: In this article, the authors systematically studied spacetimes of plane-fronted gravitational waves with parallel rays (pp-waves) in Einstein-aether theory and found that there exist eight cases, in two of which any form of pp-waves can exist, similar to that in GR, while in the other six of which, pp-wave exist only in particular forms.
Abstract: In this paper, we systematically study spacetimes of plane-fronted gravitational waves with parallel rays (pp-waves) in Einstein-aether theory. In contrast to General Relativity (GR), now the problem in general becomes overdetermined. In particular, for the linearly polarized pp-waves, there are five independent vacuum Einstein-aether field equations for three unknown functions. Therefore, solutions exist only for particular choices of the four free parameters $c_{i}$'s of the theory. We find that there exist eight cases, in two of which any form of pp-waves can exist, similar to that in GR, while in the other six of which, pp-waves exist only in particular forms. Beyond these eight cases, solutions either do not exist or are trivial (simply representing a Minkowski spacetime with a constant or dynamical aether field.).

3 citations

Journal ArticleDOI
16 Jun 2021-Universe
TL;DR: In this paper, the authors studied spherically symmetric spacetimes in Einstein-aether theory in three different coordinate systems, the isotropic, Painleve-Gullstrand, and Schwarzschild coordinates, in which the aether is always comoving, and presented both time-dependent and time-independent exact vacuum solutions.
Abstract: We study spherically symmetric spacetimes in Einstein-aether theory in three different coordinate systems, the isotropic, Painleve-Gullstrand, and Schwarzschild coordinates, in which the aether is always comoving, and present both time-dependent and time-independent exact vacuum solutions. In particular, in the isotropic coordinates we find a class of exact static solutions characterized by a single parameter c14 in closed forms, which satisfies all the current observational constraints of the theory, and reduces to the Schwarzschild vacuum black hole solution in the decoupling limit (c14=0). However, as long as c14≠0, a marginally trapped throat with a finite non-zero radius always exists, and on one side of it the spacetime is asymptotically flat, while on the other side the spacetime becomes singular within a finite proper distance from the throat, although the geometric area is infinitely large at the singularity. Moreover, the singularity is a strong and spacetime curvature singularity, at which both of the Ricci and Kretschmann scalars become infinitely large.

2 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

Journal ArticleDOI
TL;DR: The review aims at providing an overall picture of the subject and an entry point to students and researchers interested in joining the field and a quick reference to recent results and constraints on testing gravity at cosmological scales.
Abstract: We review recent developments and results in testing general relativity (GR) at cosmological scales. The subject has witnessed rapid growth during the last two decades with the aim of addressing the question of cosmic acceleration and the dark energy associated with it. However, with the advent of precision cosmology, it has also become a well-motivated endeavor by itself to test gravitational physics at cosmic scales. We overview cosmological probes of gravity, formalisms and parameterizations for testing deviations from GR at cosmological scales, selected modified gravity (MG) theories, gravitational screening mechanisms, and computer codes developed for these tests. We then provide summaries of recent cosmological constraints on MG parameters and selected MG models. We supplement these cosmological constraints with a summary of implications from the recent binary neutron star merger event. Next, we summarize some results on MG parameter forecasts with and without astrophysical systematics that will dominate the uncertainties. The review aims at providing an overall picture of the subject and an entry point to students and researchers interested in joining the field. It can also serve as a quick reference to recent results and constraints on testing gravity at cosmological scales.

348 citations

Journal ArticleDOI
Leor Barack1, Vitor Cardoso2, Vitor Cardoso3, Samaya Nissanke4  +228 moreInstitutions (101)
TL;DR: A 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 can be found in this article, which is an initiative taken within the framework of the European Action on 'Black holes, Gravitational waves and Fundamental Physics'.
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'. © 2019 IOP Publishing Ltd.

314 citations

Journal ArticleDOI
TL;DR: The effective field theory of dark energy as mentioned in this paper is based on a Lagrangian description of cosmological perturbations which depends on a number of functions of time, some of which are non-minimal couplings representing genuine deviations from General Relativity.

133 citations

Journal ArticleDOI
TL;DR: In this article, the authors studied the shadow cast by two types of charged and slowly rotating black holes in the Einstein-\AE{}ther theory of gravity, and they showed that the presence of the \ae{}th field can also affect the size of the shadow.
Abstract: In this paper, we study the shadow cast by two types of charged and slowly rotating black holes in the Einstein-\AE{}ther theory of gravity. These two types of black holes correspond to two specific combinations of the coupling constants of the \ae{}ther field, i.e., ${c}_{14}=0$ but ${c}_{123}\ensuremath{ e}0$ for the first type and ${c}_{123}=0$ for the second type. For both types of black holes, in addition to the mass and charge of the black holes, we show that the presence of the \ae{}ther field can also affect the size of the shadow. For the first type of black hole, it is shown that the shadow size increases with the parameter ${c}_{13}$, while for the second type of black hole, the shadow size still increases with ${c}_{13}$ but decreases with the parameter ${c}_{14}$. With these properties of the \ae{}ther parameters, we also discuss the observational constraints on these parameters by using the data of the first black hole image by the Event Horizon Telescope. In addition, we also explore the effect of the \ae{}ther field on the deflection angle of light and the time delay by using the Gauss-Bonnet theorem. It is shown that, for a specific combination ${c}_{123}=0$, the deflection angle/time delay is slightly affected by the \ae{}ther parameter ${c}_{13}$ at the leading order.

132 citations