Bulletin of the American Physical Society
2005 APS April Meeting
Saturday–Tuesday, April 16–19, 2005; Tampa, FL
Session T9: Particles and Cosmology |
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Sponsoring Units: DPF DAP Chair: Konstantin Matchev, University of Florida Room: Marriott Tampa Waterside Room 5 |
Monday, April 18, 2005 1:30PM - 1:42PM |
T9.00001: Short Distance and Initial State Effects in Inflation Emil Mottola, Paul Anderson, Carmen Molina-Paris We consider general homogeneous isotropic initial states in inflation, such as might be generated by novel short distance physics, and determine their observational consequences for the CMB power spectrum. We also compute the stress-energy tensor of these general states and give the quantitative criteria necessary for initial state effects not to disturb the inflationary expansion. [Preview Abstract] |
Monday, April 18, 2005 1:42PM - 1:54PM |
T9.00002: A Thermal Graviton Background from Extra Dimensions Ethan Siegel, James Fry Inflationary cosmology predicts a low-amplitude graviton background across a wide range of frequencies. We demonstrate that the presence of extra spatial dimensions will modify the primordial graviton spectrum. If the fundamental scale of these extra dimensions is below the reheat temperature, the high-frequency modes of the graviton background may have a thermal spectrum instead. The energy density in this background is significant enough that nucleosynthesis may be affected in a substantial way. Examining the 21-cm hydrogen line may allow for direct detection of a thermal graviton background. [Preview Abstract] |
Monday, April 18, 2005 1:54PM - 2:06PM |
T9.00003: Evolution of cosmic strings Vitaly Vanchurin We investigate the evolution of cosmic strings network in flat space. We give a dynamical argument that the structures on infinite strings should obey a scaling law. We perform a simulation of the network which uses functional forms for the string position and thus is exact to the limits of computer arithmetic. Our results confirm that the wiggles on the strings obey a scaling law with equal power per logarithmic interval of wavelength up to a cutoff that scales with the simulation time. The average distance between long strings also scales accurately with the time. We also discuss the questions of loop production and fragmentation, and the evolution of strings with intercommutation probabilities $p<1$. [Preview Abstract] |
Monday, April 18, 2005 2:06PM - 2:18PM |
T9.00004: Rotating Brane Worlds and the Global Rotation of the Universe Ali Nayeri, Alan Guth We introduce a class of brane-world models in which a single brane is embedded in an anti-de Sitter spacetime containing a rotating (Kerr) black hole. In this Letter we consider the case of slow rotation, calculating the metric and dynamics of the brane world to first order in the angular momentum of the black hole. To this order we find that the cosmic fluid on the brane rotates rigidly relative to a Robertson-Walker frame of reference, which in turn rotates rigidly relative to the original Kerr-anti-de Sitter coordinate frame. Corrections to the Friedmann equations and the shape of the brane occur only at higher order. We construct models for which the geometry on the brane is either closed or open, but the open models are described only for small distances from the rotation axis, and may very likely develop pathologies at larger distances. Finally we discuss the effect of rotation as a dark energy when we look at the Friedmann equations beyond the first order in the angular momentum of the bulk black hole. [Preview Abstract] |
Monday, April 18, 2005 2:18PM - 2:30PM |
T9.00005: Constrained Perturbative Expansion of the DGP Model Chad Middleton, George Siopsis We address the vDVZ discontinuity of the 5D DGP model which consists of a 3-brane residing in a flat, infinite-volume bulk. It was argued by Gabadadze [hep-th/0403161] that the breakdown of the 5D perturbative expansion is due to the weak-field expansion itself and is avoided when a different expansion - the constrained perturbation theory - is adopted. Expanding on this work, we subject the DGP model to more general regulating conditions and solve the field equations. The solution reduces to the standard DGP and Gabadadze solutions for special choices of the brane ``gauge'' parameter. [Preview Abstract] |
Monday, April 18, 2005 2:30PM - 2:42PM |
T9.00006: An Alternative to Dark Energy: $\Lambda = 0$ Accelerating Cosmologies with Exchange between the Bulk and Brane Grant Mathews, Kenichi Umezu, Kiyotomo Ichiki, Toshitaka Kajino, Masanobu Yahiro We study the cosmological brane world scenario in which the bulk dimension is not {\it empty}. Rather, exchange of mass-energy between the bulk and the brane is allowed. The evolution of matter fields to an observer on the brane is then modified by new terms in the energy momentum tensor describing this exchange. In this paper we specifically investigate the constraints from various cosmological observations on the flow of matter from the bulk to the brane. Interestingly, we show that it is possible to have a $\Lambda = 0$ cosmology in the brane which satisfies all presently available cosmological constraints. At the same time this model also accounts for the suppression of the CMB power spectrum at low multipoles. In this cosmology, the observed cosmic acceleration is attributable to the so-called "dark radiation" associated with the projection of the flow of matter from the bulk to the brane. A peculiar aspect of this cosmology is that the universal dark matter content may be significantly larger than that of a standard $\Lambda CDM$ cosmology. Its influence, however, is offset by the dark-radiation term. Possible other observational tests of this new cosmological paradigm are suggested. [Preview Abstract] |
Monday, April 18, 2005 2:42PM - 2:54PM |
T9.00007: Nonlinear quantum inflaton fluctuations in the early universe Bojan Losic The significance of nonlinear quantum fluctuations in a massless, minimally coupled, inflaton is studied in the limit of very slow roll. In particular we examine their effect, to linear order, on the metric fluctuations they induce by consistently solving the regularized Einstein equations. We find that the quantum state describing these flucuations must be $SO(4,1)$ invariant if perturbation theory is to be consistent to second order. [Preview Abstract] |
Monday, April 18, 2005 2:54PM - 3:06PM |
T9.00008: Cosmology from decaying dark energy, primordial at the Planck scale Jaime Besprosvany The consideration of dark energy's quanta, required also by thermodynamics, introduces its chemical potential into the cosmological equations. Isolating its main contribution, we obtain solutions with dark energy decaying to matter or radiation. When dominant, their energy densities tend asymptotically to a constant ratio, explaining today's dark energy-dark matter coincidence, and in agreement with supernova redshift data, and an age-of-the-universe constraint. This also connects the Planck and today's scales through time. This decay may be manifested in the highest-energy cosmic rays, recently detected. [Preview Abstract] |
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