Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session R12: Cosmology: Inflation 
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Sponsoring Units: DAP Chair: Jeffrey Filippini, University of Illinois  Urbana Room: 250DE 
Monday, April 18, 2016 10:45AM  10:57AM 
R12.00001: Attractor effects in Preheating after multifield inflation with nonminimal couplings Evangelos Sfakianakis, Matthew DeCross, David Kaiser, Anirudh Prabhu, Chanda PrescodWeinstein Multifield models of inflation with nonminimal couplings are in excellent agreement with the observational results from Planck. It is thus imperative that the preheating behavior of these models is analyzed, if one wishes to connect any viable inflationary proposal to the hot Big Bang. I will describe the strong singlefield attractor behavior that exists during inflation in these models and how it generically persists after the end of inflation, thereby avoiding the ``dephasing'' that can occur in multifield models. Hence there is efficient transfer of energy from the oscillating inflaton field(s) to coupled fluctuations. A doublycovariant formalism can be used for studying such resonances and identifing several features of preheating specific to the nonminimal couplings, including effects that arise from the nontrivial fieldspace manifold. In particular, whereas longwavelength fluctuations in both the adiabatic and isocurvature directions may be resonantly amplified for small or modest values of the dimensionless nonminimal couplings, one can show suppression of the growth of longwavelength isocurvature modes in the limit of strong coupling. [Preview Abstract] 
Monday, April 18, 2016 10:57AM  11:09AM 
R12.00002: Resonance Structure of Preheating after multifield inflation with nonminimal couplings (Part 2) Chanda PrescodWeinstein, Matthew DeCross, David Kaiser, Anirudh Prabhu, Evangelos Sfakianakis Postinflation reheating is a critical phase in the history of the cosmos, necessary to connect earlyuniverse inflation to the successes of the standard hot big bang scenario. Reheating falls between two regimes that are well constrained by observations and match the latest observations remarkably well. After reheating, the energy density should include contributions from multiple species of matter, including the Standard Model particles or types of matter that decay into Standard Model particles prior to bigbang nucleosynthesis. Reheating therefore must be a multifield phenomenon. In this talk we continue our investigation of multifield inflation with nonminimal couplings, focusing on the ``preheatingâ€ť phase after inflation during which the scalarfield condensate(s) that drove inflation decay resonantly into highermomentum quanta. Here we present the structure of resonances in this family of models semianalytically and numerically across wide regions of parameter space. We construct Floquet charts for a wide range of nonminimal couplings. We also compare the resonance structure with the wellknown minimally coupled quartic model, showing how the introduction of nonniminal couplings affects the resonance bands. [Preview Abstract] 
Monday, April 18, 2016 11:09AM  11:21AM 
R12.00003: Inflationary perturbations in a closed FLRW universe Nelson Yokomizo, Beatrice Bonga, Brajesh Gupt We investigate the evolution of gauge invariant quantum perturbations in the closed FLRW model in the presence of an inflationary potential. We first find out initial conditions for the background geometry which lead to a desired slowroll phase that is compatible with observation. Providing the initial conditions for the quantum field at the onset of slowroll we study the influence of the spatial curvature on the scalar and tensor power spectra at the end of inflation. By comparing our results with the recent Planck data we discuss the role of spatial curvature on the estimation of various cosmological parameters. We highlight the main differences from the standard inflationary scenario in a flat FLRW model and potential implications for future observations. Finally, we comment on the quantum gravitational extension of this scenario to the Planck scale. [Preview Abstract] 
Monday, April 18, 2016 11:21AM  11:33AM 
R12.00004: Beginning inflation in an inhomogeneous universe William East, Matthew Kleban, Andrei Linde, Leonardo Senatore The idea that a period of exponential expansion occurred early in the Universe's history was originally proposed in order to explain the large scale homogeneity and isotropy of the Universe. However, there remain open questions about the conditions under which inflation can eventually arise when homogeneity is not assumed to begin with it. I will describe an investigation, utilizing simulations in full general relativity, of the very inhomogeneous regime where initially the gradient energy of the scalar inflaton field dominates over the potential energy, including the strongfield regime where the wavelength of the inhomogeneities are comparable to the Hubble radius, and black holes form. The results show that inflation can eventually arise from a general class of such initial conditions, at least as long as the the scalar field variations do not include values off the inflationary plateau. I will also comment on future directions for using the tools of numerical relativity to explore nonlinear and strongfield dynamics in cosmology. [Preview Abstract] 

R12.00005: ABSTRACT WITHDRAWN 
Monday, April 18, 2016 11:45AM  11:57AM 
R12.00006: Complex Scalar Field Dark Matter and its Imprint on the Gravitational Wave Background from Inflation Bohua Li, Paul Shapiro, Tanja RindlerDaller We consider an alternative CDM to WIMP dark matter, ultralight bosons (m$>\sim10^{22}$eV) of a complex scalar field (SFDM), whose number per unit comoving volume is conserved after particle production during standard reheating (w=0). In a $\Lambda$SFDM universe, SFDM starts relativistic, evolving from stiff (w=1) to radiationlike (w=1/3), before becoming nonrelativistic and CDMlike at late times (w=0). Thus, before the familiar radiationdominated phase, there is an earlier phase of stiffmatterdomination. The transitions between these phases, determined by SFDM particle mass and selfinteraction coupling strength, are constrained by cosmological observables, particularly $N_{\rm{eff}}$, the effective number of neutrino species during BBN, the redshift of matterradiation equality, and tensor fluctuations from inflation, which imprint CMB Bmodes. Tensor modes that reenter the horizon during or before the stiff phase contribute an energy density as gravitational waves which is amplified by the stiff phase, increasing the expansion rate of the radiationdominated era. These effects yield constraints on SFDM parameters and make detection of these GWs today possible at high frequencies by laser interferometry, for currently allowed tensortoscalar ratio r and reheat temperature. [Preview Abstract] 
Monday, April 18, 2016 11:57AM  12:09PM 
R12.00007: The tensor bispectrum in a matter bounce V. Sreenath, Debika Chowdhury, L. Sriramkumar Matter bounces are bouncing scenarios wherein the universe contracts as in a matter dominated phase at early times. Such scenarios are known to lead to a scale invariant spectrum of tensor perturbations, just as de Sitter inflation does. In this work, we examine if the tensor bispectrum can discriminate between the inflationary and the bouncing scenarios. Using the Maldacena formalism, we analytically evaluate the tensor bispectrum in a matter bounce for an arbitrary triangular configuration of the wavevectors. We show that, over scales of cosmological interest, the nonGaussianity parameter $h_{_{\rm NL}}$ that characterizes the amplitude of the tensor bispectrum is quite small when compared to the corresponding values in de Sitter inflation. During inflation, the amplitude of the tensor perturbations freeze on superHubble scales, a behavior that results in the socalled consistency condition relating the tensor bispectrum and the power spectrum in the squeezed limit. In contrast, in the bouncing scenarios, the amplitude of the tensor perturbations grow strongly as one approaches the bounce, which suggests that the consistency condition will not be valid in such situations. We explicitly show that the consistency relation is indeed violated in the matter bounce. [Preview Abstract] 
Monday, April 18, 2016 12:09PM  12:21PM 
R12.00008: Possible Evidence for PlanckScale Resonant Particle Production during Inflation from the CMB Power Spectrum Mayukh Gangopadhyay, Grant Mathews, Kiyotomo Ichiki, Toshitaka Kajino The power spectrum of the cosmic microwave background from both the {\it Planck} and {\it WMAP} data exhibits a slight dip for multipoles in the range of $l= 1030$. We show that such a dip could be the result of the resonant creation of massive particles that couple to the inflaton field. For our bestfit models, the epoch of resonant particle creation reenters the horizon at a wave number of $k_* \sim 0.00011 \pm 0.0004 $ ($h$ Mpc$^{1}$). The amplitude and location of this feature corresponds to the creation of a number of degenerate fermion species of mass $\sim (811) /\lambda^{3/2} $ $m_{pl}$ during inflation where $\lambda \sim (1.0 \pm 0.5) N^{2/5}$ is the coupling constant between the inflaton field and the created fermion species, while $N$ is the number of degenerate species. Although the evidence is of marginal statistical significance, this could constitute new observational hints of unexplored physics beyond the Planck scale. [Preview Abstract] 
Monday, April 18, 2016 12:21PM  12:33PM 
R12.00009: Studies of Inflationary Phase Transitions by Partition Sums over the Inflaton Field in a Spacetime Constructed from Intersecting Manifolds Kendall Mallory This presentation gives results from studies of inflationary spacetime models exhibiting phase transitions. Grand partition sums are computed over normal modes of the inflaton scalar field. These are embedded within a four dimensional spacetime constructed from the intersection between two, five dimensional manifolds. This space is homogeneous, and isotropic. The expansion is controlled by a parameter representing the relative position of the manifolds, and by their shape. For given values of this parameter the geometry recreates de Sitter or Antide Sitter space. Thermodynamic results are presented given simple assumptions regarding the behavior of this space as it undergoes inflationary expansion. The validity of modelling the dynamics of state transitions with thermodynamic equilibrium states, is assumed here [Preview Abstract] 
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