The Overshoot Problem and Giant Structures

Models of small-field inflation often suffer from the overshoot problem. A particularly efficient resolution to the problem was proposed recently in the context of string theory. We show that this resolution predicts the existence of giant spherically symmetric overdense regions with radius of at least 110 Mpc. We argue that if such structures will be found they could offer an experimental window into string theory.Comment: 19 pages, 1 figure, comments and refs. adde

D6+D0 and Five Dimensional Spinning Black Hole

We study the system of D6+D0 branes at sub-stringy scale. We show that the proper description of the system, for large background field associated with the D0-branes, is via spinning chargeless black holes in five dimensions. The repulsive force between the D6-branes and the D0-branes is understood through the centrifugal barrier. We discuss the implication on the stability of the D6+D0 solution.Comment: 8 page

Parity in the CMB: Space Oddity

We search for a direction in the sky that exhibits parity symmetry under reflections through a plane. We use the natural estimator, which compares the power in even and odd $\ell+m$ multipoles, and apply minimal blind masking of outliers to the ILC map in order to avoid large errors in the reconstruction of multipoles. The multipoles of the cut sky are calculated both naively and by using the covariance inversion method and we estimate the significance of our results using $\Lambda$CDM simulations. Focusing on low multipoles, $2\leq \ell \leq \ell_{\max}$ with $\ell_{\max}=5,6$ or even 7, we find two perpendicular directions of even and odd parity in the map. While the even parity direction does not appear significant, the odd direction is quite significant -- at least a $3.6\sigma$ effect.Comment: 6 pages, 7 figures. Accepted for publication in The Astrophysical Journa

A stringy glimpse into the black hole horizon

We elaborate on the recent claim [arXiv:1702.03583] that non-perturbative effects in $\alpha'$, which are at the core of the FZZ duality, render the region just behind the horizon of the $SL(2,\mathbb{R})_k/U(1)$ black hole singular already at the classical level ($g_s=0$). We argue that the 2D classical $SL(2,\mathbb{R})_k/U(1)$ black hole could shed some light on quantum black holes in higher dimensions including large black holes in $AdS_5\times S^5$