Braneworld Cosmological Perturbation Theory at Low Energy

Homogeneous cosmology in the braneworld can be studied without solving bulk equations of motion explicitly. The reason is simply because the symmetry of the spacetime restricts possible corrections in the 4-dimensional effective equations of motion. It would be great if we could analyze cosmological perturbations without solving the bulk. For this purpose, we combine the geometrical approach and the low energy gradient expansion method to derive the 4-dimensional effective action. Given our effective action, the standard procedure to obtain the cosmological perturbation theory can be utilized and the temperature anisotropy of the cosmic background radiation can be computed without solving the bulk equations of motion explicitly.Comment: 10 pages, Based on a talk presented at ACRGR4, the 4th Australasian Conference on General Relativity and Gravitation, Monash University, Melbourne, January 2004. To appear in the proceedings, in General Relativity and Gravitatio

Braneworld Kaluza-Klein Corrections in a Nutshell

Evaluating Kaluza-Klein (KK) corrections is indispensable to test the braneworld scenario. In this paper, we propose a novel symmetry approach to a 4-dimensional effective action with KK corrections for the Randall-Sundrum two-brane system. The result can be used to assess the validity of the low energy approximation. Also, our result provides the basis for predicting CMB spectrum with KK corrections and the study of the transition from black strings to black holes.Comment: 4 page

A note on initial state entanglement in inflationary cosmology

We give a new interpretation of the effect of initial state entanglement on the spectrum of vacuum fluctuations. We consider an initially entangled state between two free massive scalar fields in de Sitter space. We construct the initial state by making use of a Bogoliubov transformation between the Bunch-Davies vacuum and a four mode squeezed state, and then derive the exact power spectrum for one of the scalar fields. We demonstrate that an oscillatory spectrum hardly appears for the initially entangled state unless an ad hoc absolute value of the Bogoliubov coefficients is chosen.Comment: 10 page

Cosmological implications of quantum entanglement in the multiverse

We explore the cosmological implications of quantum entanglement between two causally disconnected universes in the multiverse. We first consider two causally separated de Sitter spaces with a state which is initially entangled. We derive the reduced density matrix of our universe and compute the spectrum of vacuum fluctuations. We then consider the same system with an initially non-entangled state. We find that scale dependent modulations may enter the spectrum for the case of initially non-entangled state due to quantum interference. This gives rise to the possibility that the existence of causally disconnected universes may be experimentally tested by analyzing correlators in detail.Comment: 12 pages, 1 figur

Non-college-bound English learners as the underserved third: How students graduate from high school without being college- or career-ready

Not all high school students go to college. Yet, because there is currently such a dominant emphasis on “college for all,” preparing non-college-bound students for career-readiness has received short shrift. This issue is particularly important for English learners (ELs) because close to half of high school ELs do not advance to postsecondary education. Through a longitudinal ethnography of two underperforming, non-college-bound ELs, I examine how and why a relatively well-resourced school allowed these students to graduate without college- and career-readiness. I argue that although there were substantial structural inequalities that led to the under-education of the two ELs, educators at the school were largely unaware of such barriers and attributed the ELs’ underachievement to the students’ own deficits. I counter this institutional deficit orientation with alternative stories of student assets that illuminate the substantial strengths and talents that the focal ELs possessed, which, if recognized and integrated into their education, could have led to career-readiness.Accepted manuscrip