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Inflationary non-Gaussianities in the most general second-order scalar-tensor theories
Inflationary non-Gaussianities in the most general second-order scalar-tensor theories
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2011/10/14
For very general scalar-field theories in which the equations of motion are at second-order, we evaluate the three-point correlation function of primordial scalar perturbations generated during inflat...
On the prior dependence of constraints on the tensor-to-scalar ratio
infl ation, primordial gravitational waves (theory), cosmological parameters from CMBR
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2011/10/9
We investigate the prior dependence of constraints on cosmic tensor perturbations. Commonly imposed is the strong prior of the single-field inflationary consistency equation, relating the tensor spect...
Model-Independent Comparisons of Pulsar Timings to Scalar-Tensor Gravity
General Relativity Gravity Gravitation Scalar-Tensor Tensor-Scalar Neutron Stars Pulsars Binary Pulsars Double Pulsar
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2011/10/14
Observations of pulsar timing provide strong constraints on scalar-tensor theories of gravity, but these constraints are traditionally quoted as limits on the microscopic parameters (like the Brans-Di...
Asymptotically safe gravity as a scalar-tensor theory and its cosmological implications
Asymptotically gravity scalar-tensor theory cosmological implications
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2011/10/14
We study asymptotically safe gravity with Einstein-Hilbert truncation taking into account the renormalization group running of both gravitational and cosmological constants. We show the classical beha...
A long-wavelength instability involving the stress tensor
instabilities—cosmic rays—acceleration of particles—ISM: supernova remnants
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2011/10/20
Cosmic ray acceleration through first-order Fermi acceleration in a collisionless plasma relies on efficient scattering off magnetic field fluctuations. Scattering is most efficient for magnetic field...
On the redundancy of operators and the bispectrum in the most general second-order scalar-tensor theory
redundancy operators bispectrum general second-order scalar-tensor theory
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2011/10/19
In this short note we explain how to use the linear equation of motions to simplify the third-order action for the cosmological fluctuations. No field redefinition is needed in this exact procedure wh...
Time-varying G in shift-symmetric scalar-tensor theories with a Vainshtein mechanism
shift-symmetric scalar-tensor theories Vainshtein mechanism
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2011/10/18
We show that the current bounds on the time variation of the Newton constant G can put severe constraints on many interesting scalar-tensor theories which possess a shift symmetry and a nonminimal mat...
Observing the Big Bounce with Tensor Modes in the Cosmic Microwave Background: Phenomenology and Fundamental LQC Parameters
Quantum gravity quantum cosmology
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2010/11/12
Cosmological models where the standard Big Bang is replaced by a bounce have been studied for
decades. The situation has however dramatically changed in the last years for two reasons. First,because ...
Stability and QuasinormalModes of Black holes in Tensor-Vector-Scalar theory: Scalar Field Perturbations
Stability QuasinormalModes Black holes Tensor-Vector-Scalar theory Scalar Field Perturbations Tensor-Vector-Scalar theory
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2010/11/16
The imminent detection of gravitational waves will trigger precision tests of gravity through
observations of quasinormal ringing of black holes. While General Relativity predicts just two po-larizat...
An exact cosmological solution of a Scalar-Tensor Gravity theory compatible with the $\Lambda$CDM model
exact cosmological solution Scalar-Tensor Gravity theory compatible $\Lambda$CDM model
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2010/11/15
consider the massive Scalar-Tensor theory in the Jordan frame F() = K22,Z() = 1, and U() = (1/2)m22, F() corresponds to a constant Brans-Dicke parameter !BD = 1/4K2. The constaint of the solar s...
The matter Lagrangian and the energy-momentum tensor in modified gravity with non-minimal coupling between matter and geometry
energy-momentum tensor modified gravity non-minimal coupling
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2010/3/18
We show that in modified $f(R)$ type gravity models with non-minimal coupling between matter and geometry, both the matter Lagrangian, and the energy-momentum tensor, are completely and uniquely deter...
Scalar-Scalar, Scalar-Tensor, and Tensor-Tensor Correlators from Anisotropic Inflation
Scalar-Tensor Scalar-Scalar Tensor-Tensor Anisotropic Inflation
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2010/3/22
We compute the phenomenological signatures of a model (Watanabe et al' 09) of anisotropic inflation driven by a scalar and a vector field. The action for the vector is U(1) invariant, and the model is...
On Current-Carrying Cosmic Strings and the Generalized Rainich Algebra in Scalar-Tensor Gravities
Current-Carrying Cosmic Strings the Generalized Rainich Algebra Scalar-Tensor Gravities
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2010/10/15
We obtain exact solutions for a static and charged cosmic string in a Einstein-Maxwell-Dilaton theory of a scalar-tensor type in (3+1)-Dimensions. This theory is specified by the dilaton field f, the ...
Phase Space Solutions in Scalar-Tensor Cosmological Models
Phase Space Solutions Scalar-Tensor Cosmological Models
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2010/10/15
An analysis of the solutions for the field equations of generalized scalar-tensor theories of gravitation is performed through the study of the geometry of the phase space and the stability of the sol...
Remarks on Some Vacuum Solutions of Scalar-Tensor Cosmological Models
Vacuum Solutions Scalar-Tensor Cosmological Models
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2010/10/21
We present a class of exact vacuum solutions corresponding to de Sitter and warm inflation models in the framework of scalar-tensor cosmologies. We show that in both cases the field equations reduce t...