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Register a new userConstraint on Brans-Dicke theory from Intermediate/Extreme Mass Ratio Inspirals with self-force method
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Intermediate/Extreme mass ratio inspiral (IMRI/EMRI) system provides a good tool to test the nature of gravity in strong field. We construct the self-force and use the self-force method to generate accurate waveform templates for IMRIS/EMRIs on quasi-elliptical orbits in Brans-Dicke theory. The extra monopole and dipole emissions in Brans-Dicke theory accelerate the orbital decay, so the observations of gravitational waves may place stronger constraint on Brans-Dicke theory. With a two-year observations of gravitational waves emitted from IMRIs/EMRIs with LISA, we can get the most stringent constraint on the Brans-Dicke coupling parameter $omega_0>10^5$.
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Since the evidence for an accelerated universe and the gap of 70% in the total energy, collected by WMAP, search for alternatives for the general relativity is an important issue, for this theory is not suited for these new phenomena. A particular alternative is the Brans-Dicke theory which has being allowing inspiring results, for example, concerning k-essence type fields in 4 dimensions. However, this theory is almost unexplored in the context of the dimensional reduction of the theory in 3 dimensions. In this work, we address some problems in this dimensional reduction, namely, evaluation of the deceleration parameter of the universe described by the 3 dimensional Brans-Dicke with and without matter. In both cases, we see that it is not possible to consider the theory as a model of k-essence descrybing the dark energy, but it can be considered as descrybing the dark matter.
We investigate a Jordan-Brans-Dicke (JBD) scalar field, $Phi$, with power-law potential in the presence of a second scalar field, $phi$, with an exponential potential, in both the Jordan and the Einstein frames. We present the relation of our model with the induced gravity model with power-law potential and the integrability of this kind of models is discussed when the quintessence field $phi$ is massless, and has a small velocity. We prove that in JBD theory, the de Sitter solution is not a natural attractor but an intermediate accelerated solution of the form $a(t)simeq e^{alpha_1 t^{p_1}}$, as $trightarrow infty$ where $alpha_1>0$ and $0<p_1<1$, for a wide range of parameters. Furthermore, in the Einstein frame we get that the attractor is also an intermediate accelerated solution of the form $mathfrak{a}(mathfrak{t})simeq e^{alpha_2 mathfrak{t}^{p_2}}$ as $mathfrak{t}rightarrow infty$ where $alpha_2>0$ and $0<p_2<1$, for the same conditions on the parameters as in the Jordan frame. In the special case of a quadratic potential in the Jordan frame, or for a constant potential in the Einsteins frame, these solutions are of saddle type. Finally, we present a specific elaboration of our extension of the induced gravity model in the Jordan frame, which corresponds to a linear potential of $Phi$. The dynamical system is then reduced to a two dimensional one, and the late-time attractor is linked with the exact solution found for the induced gravity model. In this example the intermediate accelerated solution does not exist, and the attractor solution has an asymptotic de Sitter-like evolution law for the scale factor. Apart from some fine-tuned examples such as the linear, and quadratic potential ${U}(Phi)$ in the Jordan frame, it is true that intermediate accelerated solutions are generic late-time attractors in a modified JBD theory.
It is not currently clear how important it will be to include conservative self-force (SF) corrections in the models for extreme-mass-ratio inspiral (EMRI) waveforms that will be used to detect such signals in LISA (Laser Interferometer Space Antenna) data. These proceedings will address this issue for circular-equatorial inspirals using an approximate EMRI model that includes conservative corrections at leading post-Newtonian order. We will present estimates of the magnitude of the parameter estimation errors that would result from omitting conservative corrections, and compare these to the errors that will arise from noise fluctuations in the detector. We will also use this model to explore the relative importance of the second-order radiative piece of the SF, which is not presently known.
Primordial black holes possibly formed in the early universe could provide a significant fraction of the dark matter and would be unique probes of inflation. A smoking gun for their discovery would be the detection of a subsolar mass compact object. We argue that extreme mass-ratio inspirals will be ideal to search for subsolar-mass black holes not only with LISA but also with third-generation ground-based detectors such as Cosmic Explorer and the Einstein Telescope. These sources can provide unparalleled measurements of the mass of the secondary object at subpercent level for primordial black holes as light as ${cal O}(0.01)M_odot$ up to luminosity distances around hundred megaparsec and few gigaparsec for LISA and Einstein Telescope, respectively, in a complementary frequency range. This would allow claiming, with very high statistical confidence, the detection of a subsolar-mass black hole, which would also provide a novel (and currently undetectable) family of sources for third-generation detectors.
An extreme mass ratio inspiral takes place when a compact stellar object is inspiraling into a supermassive black hole due to gravitational radiation reaction. Gravitational waves (GWs) from this system can be calculated using the Teukolsky equation (TE). In our case, we compute the asymptotic GW fluxes of a spinning body orbiting a Kerr black hole by solving numerically the TE both in time and frequency domain. Our ultimate goal is to produce GW templates for space-based detectors such as LISA.
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