Laura Mersini-Houghton

Birth of the Universe from the Landscape of String Theory

We show that a unique, most probable and stable solution for the wavefunction of the universe, with a very small cosmological constant

Why the Universe started from a low entropy state

\Lambda_1\simeq\big(\frac{\pi}{l_{p}N}\big)^2

Can we predict Λ for the non-SUSY sector of the landscape?

, can be predicted from the supersymmetric minisuperspace with N vacua of the landscape of string theory without referring to the anthropic principle. Due to the nearest neighbor tunneling in moduli space lattice, the N-fold degeneracy of the vacua is lifted and a discrete spectrum of bound state levels over the whole minisuperspace emerges. Supersymmetry is spontaneously broken by these bound states, with discrete non-zero energy levels

'Tilting' the Universe with the Landscape Multiverse: The 'Dark' Flow

\Lambda_s\simeq\big(\frac{s\pi}{l_{p}N}\big)^2

Cosmological Avatars of the Landscape II: CMB and LSS Signatures

, s=1,2,...

First glimpse of string theory in the sky

We show that the inclusion of backreaction of massive long wavelengths imposes dynamical constraints on the allowed phase space of initial conditions for inflation, which results in a superselection rule for the initial conditions. Only high energy inflation is stable against collapse due to the gravitational instability of massive perturbations. We present arguments to the effect that the initial conditions problem cannot be meaningfully addressed by thermostatistics as far as the gravitational degrees of freedom are concerned. Rather, the choice of the initial conditions for the universe in the phase space and the emergence of an arrow of time have to be treated as a dynamic selection.

Cosmic bubble and domain wall instabilities I: parametric amplification of linear fluctuations

We propose a new selection criterion for predicting the most probable wavefunction of the universe that propagates on the string landscape background, by studying its dynamics from a quantum cosmology view. Previously, we applied this proposal to the SUSY sector of the landscape. In this work, the dynamic selection criterion is applied to the investigation of the non-SUSY sector. In the absence of detailed information about its structure, it is assumed that this sector has a stochastic distribution of vacua energies. The calculation of a distribution probability for the cosmological constants Λeff, obtained from the density of states ρ, indicates that the most probable wavefunction is peaked around universes with zero Λeff. In contrast to the extended wavefunction solutions found for the SUSY sector with N-vacua and peaked around , wavefunctions residing on the non-SUSY sector exhibit Anderson localization. Although minisuperspace is a limited approach it presently provides a dynamical quantum selection rule for the most probable vacua solution from the landscape.

Cosmological avatars of the landscape. I. Bracketing the supersymmetry breaking scale

We argue that the recent observations of large scale bulk flows by Kashlinsky et al. has a natural explanation in terms of superhorizon inhomogeneities induced by nonlocal entanglement of our Hubble volume with modes and domains beyond the horizon. This entanglement gives rise to corrections to the Newtonian potential on a characteristic scale L1 103H?1, and it induces a dipole and quadrupole contribution in the CMB. We also show that these induced multipoles are aligned with each other, with the alignment axis normal to their plane being oriented along the preferred frame determined by the dipole. We also give other potential tests of our hypothesis.

Limitations of anthropic predictions for the cosmological constant Λ: cosmic heat death of anthropic observers

This is the second paper in the series that confronts predictions of a model of the landscape with cosmological observations. We show here how the modifications of the Friedmann equation due to the decohering effects of long wavelength modes on the wave function of the Universe defined on the landscape leave unique signatures on the CMB spectra and large scale structure (LSS). We show that the effect of the string corrections is to suppress {sigma}{sub 8} and the CMB temperature-temperature (TT) spectrum at large angles, thereby bringing WMAP and SDSS data for {sigma}{sub 8} into agreement. We find interesting features imprinted on the matter power spectrum P(k): power is suppressed at large scales indicating the possibility of primordial voids competing with the integrated Sachs-Wolfe effect. Furthermore, power is enhanced at structure and substructure scales, k{approx_equal}10{sup -2-0}h Mpc{sup -1}. Our smoking gun for discriminating this proposal from others with similar CMB and LSS predictions comes from correlations between cosmic shear and temperature anisotropies, which here indicate a noninflationary channel of contribution to LSS, with unique ringing features of nonlocal entanglement displayed at structure and substructure scales.

Investigation of the selection of original universe proposal

We propose a new method for identifying new physics imprints on present observational data in cosmology whereby signatures of string theory are clearly distinguished from imprints of possible features on the inflaton potential. Our method relies on the cross-correlations spectra of cosmic shear from large scale structure (LSS) with the cosmic microwave background (CMB) temperature anisotropies and