The parameterized post-Friedmann framework for theories of modified gravity: Concepts, formalism, and examples
نویسندگان
چکیده
منابع مشابه
A Parameterized Post-Friedmann Framework for Modified Gravity
We develop a parameterized post-Friedmann (PPF) framework which describes three regimes of modified gravity models that accelerate the expansion without dark energy. On large scales, the evolution of scalar metric and density perturbations must be compatible with the expansion history defined by distance measures. On intermediate scales in the linear regime, they form a scalar-tensor theory wit...
متن کاملParameterized Post-Friedmann Signatures of Acceleration in the CMB
We extend the covariant, parametrized post-Friedmann (PPF) treatment of cosmic acceleration from modified gravity to an arbitrary admixture of matter, radiation, relativistic components and spatial curvature. This generalization facilitates the adaptation of Einstein-Boltzmann codes for solving CMB and matter perturbations in the linear regime. We use such a code to study the effect of metric e...
متن کاملCrossing the Phantom Divide with Parameterized Post-Friedmann Dark Energy
Dark energy models with a single scalar field cannot cross the equation of state divide set by a cosmological constant. More general models that allow crossing require additional degrees of freedom to ensure gravitational stability. We show that a parameterized post-Friedmann description of cosmic acceleration provides a simple but accurate description of multiple scalar field crossing models. ...
متن کاملnetwork of phonological rules in lori dialect of andimeshk: a study within the framework of post-generative approach.
پژوهش حاضر ارائه ی توصیفی است از نظام آوایی گویش لری شهر اندیمشک، واقع در شمال غربی استان خوزستان. چهارچوب نظری این پژوهش، انگاره ی پسازایشی جزءمستقل می باشد. این پایان نامه شامل موارد زیر است: -توصیف آواهای این گویش به صورت آواشناسی سنتی و در قالب مختصه های زایشی ممیز، همراه با آوانوشته ی تفصیلی؛ -توصیف نظام آوایی گویش لری و قواعد واجی آن در چهارچوب انگاره ی پسازایشی جزءمستقل و معرفی برهم کن...
The Palatini formalism for higher-curvature gravity theories
We compare the metric and the Palatini formalism to obtain the Einstein equations in the presence of higher-order curvature corrections that consist of contractions of the Riemann tensor, but not of its derivatives. We find that in general the two formalisms are not equivalent and that the set of solutions of the Palatini equations is a non-trivial subset of the solutions of the metric equation...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
ژورنال
عنوان ژورنال: Physical Review D
سال: 2013
ISSN: 1550-7998,1550-2368
DOI: 10.1103/physrevd.87.024015