منابع مشابه
Linear perturbations of quaternionic metrics
We extend the twistor methods developed in our earlier work on linear deformations of hyperkähler manifolds [1] to the case of quaternionic-Kähler manifolds. Via Swann’s construction, deformations of a 4d-dimensional quaternionic-Kähler manifold M are in one-to-one correspondence with deformations of its 4d+ 4-dimensional hyperkähler cone S. The latter can be encoded in variations of the comple...
متن کاملLinear perturbations of hyperkähler metrics
We study general linear perturbations of a class of 4d real-dimensional hyperkähler manifolds obtainable by the (generalized) Legendre transform method. Using twistor methods, we show that deformations can be encoded in a set of holomorphic functions of 2d + 1 variables, as opposed to the functions of d + 1 variables controlling the unperturbed metric. Such deformations generically break all tr...
متن کاملBACKREACTION OF LINEAR PERTURBATIONS AND DARK ENERGYa
The coincidence problem. Perhaps the most surprising observation in modern cosmology is that the expansion of the universe has apparently started to accelerate in the recent past, at a redshift of probably less than one. This phenomenon has usually been interpreted in the context of a homogeneous and isotropic model of the universe. The acceleration can then be accommodated only by modifying gr...
متن کاملLinear Perturbations in Brane Gas Cosmology
Abstract We consider the effect of string inhomogeneities on the time dependent background of Brane Gas Cosmology. We derive the equations governing the linear perturbations of the dilatongravity background in the presence of string matter sources. We focus on long wavelength fluctuations and find that there are no instabilities. Thus, the predictions of Brane Gas Cosmology are robust against t...
متن کاملCosmological Perturbations: Entering the Non-Linear Regime
We consider one-loop corrections (non-linear corrections beyond leading order) to the bispectrum and skewness of cosmological density fluctuations induced by gravitational evolution, focusing on the case of Gaussian initial conditions and scale-free initial power spectra, P (k) ∝ k. As has been established by comparison with numerical simulations, tree-level (leading order) perturbation theory ...
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: Proceedings of the American Mathematical Society
سال: 2018
ISSN: 0002-9939,1088-6826
DOI: 10.1090/proc/14094