Inflation physics from the cosmic microwave background and large scale structure

Abstract

Executive SummaryPrecision cosmological measurements push the boundaries of our understanding of the fundamental physics that governs our universe. In the coming years, cosmologists will be in a position to make major breakthroughs in our understanding of the physics of the very early universe and be able to probe particle physics and gravity at the highest energy scales yet accessed. A major leap forward in the sensitivity of cosmological experiments is within our technological reach, leveraging past and current experience to tackle some of the most interesting fundamental physics questions.Cosmic inflation, the theory that the universe underwent a violent, exponential expansion during the first moments of time, is the leading theoretical paradigm for the earliest history of the universe and for the origin of the structure in the universe. Current measurements of the cosmic microwave background (CMB) and observations of the large-scale distributions of dark matter and galaxies in the universe are in stunning agreement with the concept of inflation. The next generations of experiments in observational cosmology are poised to decide central questions about the mechanism behind inflation. In this short document, we highlight the importance of experimentally determining the nature of inflation in the early universe and the unique opportunity these experiments provide to explore the physics of space, time, and matter at the highest energies possible: those found at the birth of the universe.

Inflection-point B−L Higgs inflation

“…For the upper-bound on M < 5.67M P , the prediction for the tensor-to-scalar ratio is bounded by r < 1.108 × 10 −4 , which is very small. However, as discussed before the prediction for the running of the spectral index α ≃ − 2.742 × 10 −3 , which is independent of M, is within the reach of future precision measurements [16]. Note that this result is even independent of the particle content of the theory.…”

“…Precision measurement of the running of the spectral index in future experiments can reduce the error to ±0.002 [16]. Hence, the prediction can be tested in the future.…”

Looking through the same lens: Shear calibration for LSST, Euclid, and WFIRST with stage 4 CMB lensing

“…CMB lensing has been measured by the WMAP satellite [39,40], the Atacama Cosmology Telescope (ACT) [41][42][43][44], the South Pole Telescope (SPT) [45][46][47], POLARBEAR [48], the Planck satellite [49,50], and the BICEP 2/Keck Array [51]. In the future, Advanced ACT [52], SPT-3G [53], and a stage 4 ground-based CMB experiment (CMB S4) [54,55], as well as the Simons Observatory [56], will provide high fidelity maps of the CMB lensing convergence over a large fraction of the sky.…”

Inflection-point inflation in a hyper-charge oriented U(1)X model

“…For the upper bound on M < 5.67M P , the resultant tensor-to-scalar ratio is given by r < 3.047 × 10 −5 , which is too small to test in the future experiments. However, as discussed in the previous section, the inflection-point inflation predicts the running of the spectral index to be α ≃ −2.742 × 10 −3 , independently of M. This predicted value is within the reach of future precision measurements [21]. We now consider the particle mass spectrum of the model at low energies.…”

“…It is expected that the future experiments can reduce the error to ±0.002 [21], and therefore the prediction of the inflection-point inflation scenario can be tested in the future.…”