搜索结果: 1-15 共查到“天文学 perturbations”相关记录26条 . 查询时间(0.171 秒)
Dynamics of Cosmological Perturbations in Multi-Speed Inflation
Dynamics Cosmological Perturbations Multi-Speed Inflation
2011/10/18
We study a multi-field inflationary theory with separable Lagrangian, which has different speed of sound for each field. We find that the fields always coupled at perturbative level through gravitatio...
Local Scale-Dependent Non-Gaussian Curvature Perturbations at Cubic Order
E ective Field Theory Cosmology In ation Non-Gaussianity
2011/10/17
We calculate non-Gaussianities in the bispectrum and trispectrum arising from the cubic term in the local expansion of the scalar curvature perturbation. We compute to three-loop order and for general...
On Shear-Free perturbations of FLRW Universes
On Shear-Free perturbations of FLRW Universes
2011/10/14
A surprising exact result for the Einstein Field Equations is that if pressure-free matter is moving in a shear-free way, then it must be either expansion-free or rotation-free. It has been suggested ...
Compensated Isocurvature Perturbations and the Cosmic Microwave Background
Compensated Isocurvature Perturbations Microwave Background
2011/10/19
Measurements of cosmic microwave background (CMB) anisotropies constrain isocurvature fluctuations between photons and non-relativistic particles to be sub-dominant to adiabatic fluctuations. Perturba...
Recent cosmological observations, including measurements of the CMB anisotropy and the primordial helium abundance, indicate the existence of an extra radiation component in the Universe beyond the st...
Manifestly gauge invariant theory of the nonlinear cosmological perturbations in the leading order of the gradient expansion
nonlinear cosmological perturbation, gauge invariance, non-Gaussianity PACS number(s):98.80.Cq
2011/9/29
In the full nonlinear cosmological perturbation theory in the leading order of the gradient expansion, all the types of the gauge invariant perturbation variables are defined. The metric junction cond...
General conditions for scale-invariant perturbations in an expanding universe
General conditions scale-invariant perturbations expanding universe
2011/9/29
We investigate the general properties of expanding cosmological models which generate scale-invariant curvature perturbations in the presence of a variable speed of sound. We show that in an expanding...
Intense ultraviolet perturbations on aquatic primary producers
Intense ultraviolet aquatic primary producers
2011/1/13
During the last decade, the hypothesis that one or more biodiversity drops in the Phanerozoic eon, evident in the geological record, might have been caused by the most powerful kind of stellar explos...
Inflationary Perturbations in Palatini Generalised Gravity
Inflationary Perturbations Palatini Generalised Gravity
2011/1/13
We examine the generation of primordial perturbations during an inflationary epoch in generalised theories of gravity when the equations of motion are derived using the Palatini variational principle...
Curvature Perturbations and non-Gaussianities from Waterfall Phase Transition during Inflation
Curvature Perturbations non-Gaussianities
2011/1/13
We consider a variant of hybrid inflation where the waterfall phase transition happens during inflation. By adjusting the parameters associated with the mass of the waterfall field, we arrange that t...
Perturbations and observational aspects of mutated hilltop inflation
observational aspects mutated hilltop inflation
2011/1/13
We perform a careful investigation of cosmological perturbations and observational aspects, taking mutated hilltop inflation as a representative model. Employing mostly analytical treatment, we derive...
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
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...
Non-adiabatic perturbations in multi-component perfect fluids
Non-adiabatic perturbations multi-component perfect fluids
2010/11/16
Еvolution of non-adiabatic perturbations in models with multiple coupled perfect fluids with
non-adiabatic sound speed is considered. Instead of splitting the entropy perturbation on relative and int...
Inflation in Entropic Cosmology: Primordial Perturbations and non-Gaussianities
Inflation Primordial Perturbations non-Gaussianities
2010/11/16
We investigate thermal inflation in double-screen entropic cosmology. We find that its realization is general, resulting from the system evolution from non-equilibrium to equilibrium. Furthermore,goin...
Transit timing variations in eccentric hierarchical triple exoplanetary systems. I. Perturbations on the time-scale of the orbital period of the perturber
Earth and Planetary Astrophysics (astro-ph.EP) Solar and Stellar Astrophysics (astro-ph.SR)
2010/12/24
We study the long-term time-scale (i.e. period comaprable to the orbital period of the outer perturber object) transit timing variations in transiting exoplanetary systems which contain a further, mor...