CMB quadrupole depression produced by early fast-roll inflation: Monte Carlo Markov chains analysis of WMAP and SDSS data

Journal Article · Tue Jul 15 00:00:00 EDT 2008 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.78.023013· OSTI ID:21250317

Destri, C ^[1]; Vega, H J. de ^[2]; Sanchez, N G ^[3]

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1. Dipartimento di Fisica G. Occhialini, Universita Milano-Bicocca Piazza della Scienza 3, 20126 Milano (Italy) and INFN, sezione di Milano, via Celoria 16, Milano (Italy)
2. LPTHE, Laboratoire Associe au CNRS UMR 7589, Universite Pierre et Marie Curie (Paris VI) et Denis Diderot (Paris VII), Tour 24, 5 eme. etage, 4, Place Jussieu, 75252 Paris, Cedex 05 (France)
3. Observatoire de Paris, LERMA, Laboratoire Associe au CNRS UMR 8112, 61, Avenue de l'Observatoire, 75014 Paris (France)

Generically, the classical evolution of the inflaton has a brief fast-roll stage that precedes the slow-roll regime. The fast-roll stage leads to a purely attractive potential in the wave equations of curvature and tensor perturbations (while the potential is purely repulsive in the slow-roll stage). This attractive potential leads to a depression of the CMB quadrupole moment for the curvature and B-mode angular power spectra. A single new parameter emerges in this way in the early universe model: the comoving wave number k{sub 1} characteristic scale of this attractive potential. This mode k{sub 1} happens to exit the horizon precisely at the transition from the fast-roll to the slow-roll stage. The fast-roll stage dynamically modifies the initial power spectrum by a transfer function D(k). We compute D(k) by solving the inflaton evolution equations. D(k) effectively suppresses the primordial power for k<k{sub 1} and possesses the scaling property D(k)={psi}(k/k{sub 1}) where {psi}(x) is a universal function. We perform a Monte Carlo Markov chain analysis of the WMAP and SDSS data including the fast-roll stage and find the value k{sub 1}=0.266 Gpc{sup -1}. The quadrupole mode k{sub Q}=0.242 Gpc{sup -1} exits the horizon earlier than k{sub 1}, about one-tenth of an e-fold before the end of fast roll. We compare the fast-roll fit with a fit without fast roll but including a sharp lower cutoff on the primordial power. Fast roll provides a slightly better fit than a sharp cutoff for the temperature-temperature, temperature-E modes, and E modes-E modes. Moreover, our fits provide nonzero lower bounds for r, while the values of the other cosmological parameters are essentially those of the pure {lambda}CDM model. We display the real space two point C{sup TT}({theta}) correlator. The fact that k{sub Q} exits the horizon before the slow-roll stage implies an upper bound in the total number of e-folds N{sub tot} during inflation. Combining this with estimates during the radiation dominated era we obtain N{sub tot}{approx}66, with the bounds 62<N{sub tot}<82. We repeated the same analysis with the WMAP-5, ACBAR-2007, and SDSS data confirming the overall picture.

• OSTI ID: 21250317
• Journal Information: Physical Review. D, Particles Fields, Vol. 78, Issue 2; Other Information: DOI: 10.1103/PhysRevD.78.023013; (c) 2008 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE
COMPARATIVE EVALUATIONS
DISTURBANCES
EVOLUTION
INFLATION
MARKOV PROCESS
MONTE CARLO METHOD
PERTURBATION THEORY
QUADRUPOLE MOMENTS
QUADRUPOLES
RELICT RADIATION
SCALING
SPACE
SPECTRA
TRANSFER FUNCTIONS
UNIVERSE
WAVE EQUATIONS