Observational consequences of a landscape

Freivogel, Ben; Kleban, Matthew; Martínez, María Rodríguez; Susskind, Leonard

doi:10.1088/1126-6708/2006/03/039

Cited by 299 publications

(479 citation statements)

References 45 publications

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“…Thus, the probability of N e e-folds of inflation is proportional to 1/N 3 e . This result can be derived analytically in an inflection point model [240] (see [661] for earlier work in a slightly different model), and is consistent with the simpler analytic arguments of §5.1.2, which focused on the appearance of the term φ 3/2 in an effective single-field description. Of course, the total number of e-folds is not itself an observable, but whether or not N e 60 strongly influences the likelihood of observing relics of a pre-inflationary stage, such as traces of bubble collisions [678][679][680][681][682].…”

Section: Multi-field Effectssupporting

confidence: 82%

“…The DBI kinetic term (see §5.3) has been argued to ameliorate the overshoot problem [659], though this conclusion was challenged by [660]. Negative spatial curvature resulting from tunneling entirely removes overshooting in certain classes of potential, and reduces its severity in general [661,662]. Finally, it was argued in [663] that the overshooting of an inflection point is ameliorated by particle production near points in field space where new species become light [664][665][666][667].…”

Section: Fine-tuningmentioning

confidence: 99%

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Inflation and String Theory

2015

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Section: Multi-field Effectssupporting

confidence: 82%

Section: Fine-tuningmentioning

confidence: 99%

Inflation and String Theory

2015

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“…Nevertheless, by introducing fine tunings it is possible to construct inflation models with observationally interesting open geometries (e.g., Gott 1982;Linde 1995;Bucher et al 1995;Linde 1999) or closed geometries (Linde 2003). Even more speculatively, there has been interest in models with open geometries from considerations of tunnelling events between metastable vacua within a "string landscape" (Freivogel et al 2006). Observational limits on spatial curvature therefore offer important additional constraints on inflationary models and fundamental physics.…”

Section: Curvaturementioning

confidence: 99%

Planck2013 results. XVI. Cosmological parameters

Ade¹,

Aghanim²,

Armitage-Caplan³

et al. 2014

A&A

5,001

163

2,253

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This paper presents the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensing-potential power spectra. We find that the Planck spectra at high multipoles ( > ∼ 40) are extremely well described by the standard spatiallyflat six-parameter ΛCDM cosmology with a power-law spectrum of adiabatic scalar perturbations. Within the context of this cosmology, the Planck data determine the cosmological parameters to high precision: the angular size of the sound horizon at recombination, the physical densities of baryons and cold dark matter, and the scalar spectral index are estimated to be θ * = (1.04147 ± 0.00062) × 10 −2 , Ω b h 2 = 0.02205 ± 0.00028, Ω c h 2 = 0.1199 ± 0.0027, and n s = 0.9603 ± 0.0073, respectively (note that in this abstract we quote 68% errors on measured parameters and 95% upper limits on other parameters). For this cosmology, we find a low value of the Hubble constant, H 0 = (67.3 ± 1.2) km s −1 Mpc −1 , and a high value of the matter density parameter, Ω m = 0.315 ± 0.017. These values are in tension with recent direct measurements of H 0 and the magnituderedshift relation for Type Ia supernovae, but are in excellent agreement with geometrical constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent level precision using Planck CMB data alone. We use high-resolution CMB data together with Planck to provide greater control on extragalactic foreground components in an investigation of extensions to the six-parameter ΛCDM model. We present selected results from a large grid of cosmological models, using a range of additional astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured over the standard six-parameter ΛCDM cosmology. The deviation of the scalar spectral index from unity is insensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find an upper limit of r 0.002 < 0.11 on the tensor-to-scalar ratio. There is no evidence for additional neutrino-like relativistic particles beyond the three families of neutrinos in the standard model. Using BAO and CMB data, we find N eff = 3.30 ± 0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the sum of neutrino masses. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of N eff = 3.046. We find no evidence for dynamical dark energy; using BAO and CMB data, the dark energy equation of state parameter is constrained to be w = −1.13 +0.13 −0.10 . We also use the Planck data to set limits on a possible variation of the fine-structure constant, dark matter annihilation and primordial magnetic fields. Despite the success of the six-parameter ΛCDM model in describing the Planck data at high multipoles, we note that this cosmology does not provide a good fit to the temperature power spectrum at low multipoles. T...

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“…The condition (4.9) in turn ensures that the quadratic term in the round brackets of (4.8) dominates over the quartic term in the axion, although the latter could become significant at the outer edge of the super-Planckian regime. (This latter effect may be interesting in light of the hints of a tension between Planck and BICEP2 [82][83][84][85], although that tension is highly uncertain given [86,87] as well as foreground unknowns. )…”

Section: Jhep09(2014)123mentioning

confidence: 99%

The powers of monodromy

McAllister

Silverstein

Westphal

et al. 2014

J. High Energ. Phys.

236

339

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Flux couplings to string theory axions yield super-Planckian field ranges along which the axion potential energy grows. At the same time, other aspects of the physics remain essentially unchanged along these large displacements, respecting a discrete shift symmetry with a sub-Planckian period. After a general overview of this monodromy effect and its application to large-field inflation, we present new classes of specific models of monodromy inflation, with monomial potentials µ 4−p φ p . A key simplification in these models is that the inflaton potential energy plays a leading role in moduli stabilization during inflation. The resulting inflaton-dependent shifts in the moduli fields lead to an effective flattening of the inflaton potential, i.e. a reduction of the exponent from a fiducial value p 0 to p < p 0 . We focus on examples arising in compactifications of type IIB string theory on products of tori or Riemann surfaces, where the inflaton descends from the NS-NS two-form potential B 2 , with monodromy induced by a coupling to the R-R field strength F 1 . In this setting we exhibit models with p = 2/3, 4/3, 2, and 3, corresponding to predictions for the tensor-to-scalar ratio of r ≈ 0.04, 0.09, 0.13, and 0.2, respectively. Using mirror symmetry, we also motivate a second class of examples with the role of the axions played by the real parts of complex structure moduli, with fluxes inducing monodromy.

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Observational consequences of a landscape

Cited by 299 publications

References 45 publications

Inflation and String Theory

Inflation and String Theory

Planck2013 results. XVI. Cosmological parameters

The powers of monodromy

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