ﻻ يوجد ملخص باللغة العربية
We revisit the question of how to calculate correlations of the curvature perturbation, $zeta$, using the $delta N$ formalism when one cannot employ a truncated Taylor expansion of $N$. This problem arises when one uses lattice simulations to probe the effects of isocurvature modes on models of reheating. Working in real space, we use an expansion in the cross-correlation between fields at different positions, and present simple expressions for observables such as the power spectrum and the reduced bispectrum, $f_{rm NL}$. These take the same form as those of the usual $delta N$ expressions, but with the derivatives of $N$ replaced by non-perturbative $delta N$ coefficients. We test the validity of this expansion and argue that our expressions are particularly well suited for use with simulations.
We develop a theory of nonlinear cosmological perturbations on superhorizon scales for a multi-component scalar field with a general kinetic term and a general form of the potential in the context of inflationary cosmology. We employ the ADM formalis
According to the equivalence principal, the long wavelength perturbations must not have any dynamical effect on the short scale physics up to ${cal O} (k_L^2/k_s^2)$. Their effect can be always absorbed to a coordinate transformation locally. So any
We derive the exact supergravity profile for the twisted scalar field emitted by a system of fractional D3 branes at a Z2 orbifold singularity supporting N=2 quiver gauge theories with unitary groups and bifundamental matter. At the perturbative leve
Large-scale clustering of highly biased tracers of large-scale structure has emerged as one of the best observational probes of primordial non-Gaussianity of the local type (i.e. f_{NL}^{local}). This type of non-Gaussianity can be generated in multi
Recently, Saad, Shenker and Stanford showed how to define the genus expansion of Jackiw-Teitelboim quantum gravity in terms of a double-scaled Hermitian matrix model. However, the models non-perturbative sector has fatal instabilities at low energy t