# A ΛCDM Bounce Scenario

### APA

Wilson-Ewing, E. (2015). A ΛCDM Bounce Scenario. Perimeter Institute. https://pirsa.org/15010074

### MLA

Wilson-Ewing, Edward. A ΛCDM Bounce Scenario. Perimeter Institute, Jan. 21, 2015, https://pirsa.org/15010074

### BibTex

@misc{ pirsa_PIRSA:15010074, doi = {10.48660/15010074}, url = {https://pirsa.org/15010074}, author = {Wilson-Ewing, Edward}, keywords = {Quantum Gravity}, language = {en}, title = {A ΛCDM Bounce Scenario}, publisher = {Perimeter Institute}, year = {2015}, month = {jan}, note = {PIRSA:15010074 see, \url{https://pirsa.org}} }

Edward Wilson-Ewing University of New Brunswick

## Abstract

We study a contracting universe composed of cold dark matter and radiation, and with a positive cosmological constant. Assuming that loop quantum cosmology captures the correct high-curvature dynamics of the space-time, we calculate the spectrum of scalar and tensor perturbations after the bounce, assuming initial quantum vacuum fluctuations. We find that the modes that exit the (sound) Hubble radius during matter-domination when the effective equation of state is slightly negative due to the cosmological constant will be nearly scale-invariant with a slight red tilt, in agreement with observations. The tensor perturbations are also nearly scale-invariant, and the predicted tensor-to-scalar ratio is small. Finally, as this scenario predicts a positive running of the scalar index, it can be differentiated from inflationary models.