Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session B5: Inflation and Dark Energy |
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Sponsoring Units: DAP Chair: Tanja Rindler-Daller, University of Vienna Room: Virginia B |
Saturday, January 28, 2017 10:45AM - 10:57AM |
B5.00001: The Viability of Phantom Dark Energy as a Quantum Field in 1st-Order FLRW Space Kevin Ludwick In the standard cosmological framework of the 0th-order FLRW metric and the use of perfect fluids in the stress-energy tensor, dark energy with an equation-of-state parameter $w < -1$ (known as phantom dark energy) implies negative kinetic energy and vacuum instability when modeled as a scalar field. However, the accepted values for present-day $w$ from Planck and WMAP9 include a significant range of values less than $-1$. We consider a more accurate description of the universe through the 1st-order perturbing of the isotropic and homogeneous FLRW metric and the components of the stress-energy tensor and investigate whether a field with an apparent $w<-1$ may still have positive kinetic energy. Treating dark energy as a classical scalar field in this metric, we find that it is not as obvious as one might think that phantom dark energy has negative kinetic energy categorically. Analogously, we find that field models of quintessence dark energy ($w>-1$) do not necessarily have positive kinetic energy categorically. We then investigate the same question treating dark energy as a quantum field in 1st-order FLRW space-time and examining the expectation value of the stress-energy tensor for $w<-1$ using adiabatic expansion. [Preview Abstract] |
Saturday, January 28, 2017 10:57AM - 11:09AM |
B5.00002: Quantum Gravity, very early universe and the cosmic microwave background Brajesh Gupt, Abhay Ashtekar The standard model of cosmology in conjunction with inflation is a robust paradigm of the evolution of our Universe from today all the way up to the energy scale $10^{16}~{\rm GeV}$. However, the framework fails to provide a faithful understanding of the physics at Planck scale since it excludes quantum gravity correction. Furthermore, recent observations reveal the presence of large scale CMB anomalies which could be signatures of new physics preceding inflation. We present a quantum gravitational extension of the current inflationary paradigm and its possible connection with the CMB anomalies. We highlight the predictions for the future observations and potential avenues where the interplay between the UV physics of very early Universe and the IR behavior of large scale perturbations can have interesting implications for late time Universe. [Preview Abstract] |
Saturday, January 28, 2017 11:09AM - 11:21AM |
B5.00003: Inflationary squeezed bispectrum and super-horizon modes Anne-Sylvie Deutsch, Sarah Shandera Generically, inflation predicts a larger number of e-folds than the $N=60$ required to solve the horizon problem. Therefore, our observations only probe a sub-volume of the whole patch generated during inflation, and the locally observed statistics might be different than the statistics in the large volume, inducing a bias, or variance, on the locally observed cosmological parameters. We study the coupling between sub- and super-horizon modes and its impact on late time correlation functions of the curvature perturbation. In particular, in this talk, we focus on the case of the bispectrum in the squeezed limit, a popular probe to study the properties of multi-field inflation. [Preview Abstract] |
Saturday, January 28, 2017 11:21AM - 11:33AM |
B5.00004: Cosmic Gauge-Field Dark Energy Christopher Devulder, Robert Caldwell We present a cosmological model in which dark energy consists of a cosmic gauge field. At early times it behaves like radiation; at late times it drives cosmic acceleration. By varying the number of fields, their coupling strength and handedness, a wide range of behavior is shown to emerge. Joint constraints on the model from SNe, BAO and CMB data are presented. We discuss the possibility that the gauge field may seed a spectrum of primordial gravitational waves with a distinct imprint on the power spectrum, as well as act like a dissipative medium for high frequency gravitational waves. We show that this model could have an impact on the B-mode polarization pattern in the CMB, as well as future probes that use standard sirens to constrain the energy budget of the Universe. [Preview Abstract] |
Saturday, January 28, 2017 11:33AM - 11:45AM |
B5.00005: Observational effects from dimensional compactification Eleni-Alexandra Kontou, Jose-Juan Blanco-Pillado, Mark Hertzberg, Ali Masoumi Many of the extensions of the Standard Model involve theories that live on a higher dimensional spacetime. On the other hand, all our observational evidence points to a 4-dimensional description of the universe at low energies so one way to accommodate these higher dimensional theories is to allow for a compactifation mechanism. In this work we explore the possibility that we can obtain any observational signature that points towards the existence of this type of process in our past. Certain so-called anomalies in the CMB data might be giving us a hint that the amount of inflation was just the minimal required to solve the cosmological problems but not longer. In such case, we might hope to see the effects of a previous state of the universe in the power spectrum of perturbations. We assume the spacetime is divided in two parts, the 3+1 dimensional manifold and an internal space of n flat compact dimensions. Before the compactification, the extra dimensions can either be expanding or contracting and we compare the observable consequences obtained within these different higher dimensional cosmological scenarios. [Preview Abstract] |
Saturday, January 28, 2017 11:45AM - 11:57AM |
B5.00006: ABSTRACT WITHDRAWN |
Saturday, January 28, 2017 11:57AM - 12:09PM |
B5.00007: Gravitational waves in axion inflation: implications for CMB and small-scales interferometer measurements Caner Unal, Marco Peloso, Lorenzo Sorbo, Juan Garcia-Bellido A strong experimental effort is ongoing to detect the primordial gravitational waves (GW) generated during inflation from their impact on the Cosmic Microwave Background (CMB). This effort is motivated by the direct relation between the amplitude of GW signal and the energy scale of inflation, in the standard case of GW production from vacuum. I will discuss the robustness of this relation and the conditions under which particle production mechanisms during inflation can generate a stronger GW signal than the vacuum one. I will present a concrete model employing a coupling between a rolling axion and a gauge field, that can produce a detectable GW signal for an arbitrarily small inflation scale, respecting bounds from back-reaction, perturbativity, and the gaussianity of the measured density perturbations. I will show how the GW produced by this mechanism can be distinguished from the vacuum ones by their spectral dependence and statistical properties. I will finally discuss the possibility of detecting an inflationary GW signal at terrestrial (AdvLIGO) and space (LISA) interferometers. Such experiments are sensitive to the modes much smaller than the ones corresponding to CMB and Large Scale Structure, presenting a unique observational window on the final stages of inflation. [Preview Abstract] |
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