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353
Inflation after wmap3: Confronting the slowroll and exact power spectra with cmb data
, 2006
"... ... year data for inflation are investigated using both the slowroll approximation and an exact numerical integration of the inflationary power spectra including a phenomenological modelling of the reheating era. At slowroll leading order, the constraints ǫ1 < 0.022 and −0.07 < ǫ2 < 0.07 ..."
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... year data for inflation are investigated using both the slowroll approximation and an exact numerical integration of the inflationary power spectra including a phenomenological modelling of the reheating era. At slowroll leading order, the constraints ǫ1 < 0.022 and −0.07 < ǫ2 < 0.07 are obtained at 95 % CL (Confidence Level) implying a tensortoscalar ratio r10 < 0.21 and a Hubble parameter during inflation H/mPl < 1.3 × 10−5. At nexttoleading order, a tendency for ǫ3> 0 is observed. With regards to the exact numerical integration, large field models, V (φ) ∝ φp, with p> 3.1 are now excluded at 95 % CL. Small field models, V (φ) ∝ 1 − (φ/µ) p, are still compatible with the data for all values of p. However, if µ/mPl < 10 is assumed, then the case p = 2 is slightly disfavoured. In addition, mild constraints on the reheating temperature for an extreme equation of state wreh � −1/3 are found, namely Treh> 2 TeV at 95 % CL. Hybrid models are disfavoured by the data, the best fit model having ∆χ2 ≃ +5 with two extra parameters in comparison with large field models. Running mass models remain compatible, but no prior independent constraints can be obtained. Finally, superimposed oscillations of transPlanckian origin are studied. The vanilla slowroll model is still the most probable one. However, the overall statistical weight in favour of superimposed oscillations has increased in comparison with the WMAP first year data, the amplitude of the oscillations satisfying 2xσ0 < 0.76 at 95 % CL. The best fit model leads to an improvement of ∆χ2 ≃ −12 for 3 extra parameters. Moreover, compared to other oscillatory patterns, the logarithmic shape is favoured.
Multidimensional mSUGRA likelihood maps
 Phys. Rev. D 73 (2006) 015013 [arXiv:hepph/0507283]. 27
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Modified Newtonian dynamics (MOND): Observational phenomenology and relativistic extensions
 Living Reviews in Relativity
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Dark Energy from backreaction
 JCAP
, 2004
"... We consider the effect of inhomogeneities on the expansion of the Einsteinde Sitter universe. We find that the backreaction of linear scalar metric perturbations results in apparent dark energy with a mixture of equations of state between 0 and –4/3. We discuss the possibility that backreaction cou ..."
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We consider the effect of inhomogeneities on the expansion of the Einsteinde Sitter universe. We find that the backreaction of linear scalar metric perturbations results in apparent dark energy with a mixture of equations of state between 0 and –4/3. We discuss the possibility that backreaction could account for presentday acceleration. 1
Crossing of the w = 1 barrier by D3brane dark energy model,” Phys
 Rev. D
"... We explore a possibility for the Universe to cross the w = −1 cosmological constant barrier for the dark energy state parameter. We consider the Universe as a slowly decaying D3brane. The D3brane dynamics is approximately described by a nonlocal string tachyon interaction and a back reaction of gr ..."
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Cited by 18 (8 self)
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We explore a possibility for the Universe to cross the w = −1 cosmological constant barrier for the dark energy state parameter. We consider the Universe as a slowly decaying D3brane. The D3brane dynamics is approximately described by a nonlocal string tachyon interaction and a back reaction of gravity is incorporated in the closed string tachyon dynamics. In a local effective approximation this model contains one phantom component and one usual field with a simple polynomial interaction. To understand cosmological properties of this system we study toy models with the same scalar fields but with modified interactions. These modifications admit polynomial superpotentials. We find restrictions on these interactions under which it is possible to reach w = −1 from below at large time. Explicit solutions with the dark energy state parameter crossing/noncrossing the barrier w = −1 are presented.
Spherical Slepian functions and the polar gap in geodesy
, 2006
"... Satellites mapping out the spatial variations of the gravitational or magnetic fields of the Earth or other planets ideally fly on polar orbits, uniformly covering the entire globe. Thus potential fields on the sphere are usually expressed in spherical harmonics, basis functions with global support. ..."
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Cited by 18 (3 self)
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Satellites mapping out the spatial variations of the gravitational or magnetic fields of the Earth or other planets ideally fly on polar orbits, uniformly covering the entire globe. Thus potential fields on the sphere are usually expressed in spherical harmonics, basis functions with global support. For various, especially engineering, reasons, however, inclined orbits are favorable. These leave a “polar gap”: an antipodal pair of axisymmetric polar caps, typically less than 10 ◦ in diameter, without any data coverage. Estimation of spherical harmonic field coefficients from an incompletely sampled sphere is prone to error, since the spherical harmonics are not orthogonal over the partial domain of the cut sphere. The historically somewhat neglected geodetic polar gap problem has been revived by, among others, Sneeuw & van Gelderen (1997), and recently,
The spectral action and cosmic topology
 arXiv:1005.2256. 18 DANIEL KOLODRUBETZ AND MATILDE MARCOLLI
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The “Unromantic Pictures” of Quantum Theory
 J. Phys. A
, 2007
"... I am concerned with two views of quantum mechanics that John S. Bell called “unromantic”: spontaneous wave function collapse and Bohmian mechanics. I discuss some of their merits and report about recent progress concerning extensions to quantum field theory and relativity. In the last section, I spe ..."
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Cited by 16 (8 self)
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I am concerned with two views of quantum mechanics that John S. Bell called “unromantic”: spontaneous wave function collapse and Bohmian mechanics. I discuss some of their merits and report about recent progress concerning extensions to quantum field theory and relativity. In the last section, I speculate about an extension of Bohmian mechanics to quantum gravity. PACS numbers: 03.65.Ta; 03.70.+k. Key words: quantum theory without observers; Ghirardi–Rimini–Weber model of spontaneous wave function collapse;
Brane inflation and the WMAP data: a Bayesian analysis
, 2007
"... The Wilkinson Microwave Anisotropy Probe (WMAP) constraints on string inspired “brane inflation ” are investigated. Here, the inflaton field is interpreted as the distance between two branes placed in a fluxenriched background geometry and has a DiracBornInfeld (DBI) kinetic term. Our method re ..."
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Cited by 16 (5 self)
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The Wilkinson Microwave Anisotropy Probe (WMAP) constraints on string inspired “brane inflation ” are investigated. Here, the inflaton field is interpreted as the distance between two branes placed in a fluxenriched background geometry and has a DiracBornInfeld (DBI) kinetic term. Our method relies on an exact numerical integration of the inflationary power spectra coupled to a MarkovChain MonteCarlo exploration of the parameter space. This analysis is valid for any perturbative value of the string coupling constant and of the string length, and includes a phenomenological modelling of the reheating era to describe the postinflationary evolution. It is found that the data favour a scenario where inflation stops by violation of the slowroll conditions well before brane annihilation, rather than by tachyonic instability. Concerning the background geometry, it is established that log v> −10 at 95 % confidence level (CL), where v is the dimensionless ratio of the fivedimensional submanifold at the base of the sixdimensional warped conifold geometry to the volume of the unit fivesphere. The reheating energy scale remains poorly constrained, Treh> 20 GeV at 95 % CL, for an extreme equation of state (wreh � −1/3) only. Assuming the string length is known, the favoured values of the string coupling and of the RamondRamond total background charge appear to be correlated. Finally, the stochastic regime (without and with volume effects) is studied using a perturbative treatment of the Langevin equation. The validity of such an approximate scheme is discussed and shown to be too limited for a full characterisation of the quantum effects.