Leptogenesis from Gravity Waves in Models of Inflation

Alexander, Stephon; Peskin, Michael E.; Sheikh-Jabbari, M. M.

doi:10.1103/physrevlett.96.081301

Cited by 318 publications

(415 citation statements)

References 12 publications

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“…The amplitude of gravitational waves gives the Hubble curvature during inflation and would tell us the value of the inflation potential [15]. In addition gravitational waves produced during inflation can have several applications like leptogenesis by the gravitational spin-coupling to neutrinos [16] or by a gravitational Chern-Simon coupling of the lepton number current [17]. Observation of the B-mode polarization in the CMB would confirm the existence of primordial super-horizon gravitational waves.…”

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confidence: 88%

Enhanced Polarization of the Cosmic Microwave Background Radiation from Thermal Gravitational Waves

2006

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If inflation was preceded by a radiation era then at the time of inflation there will exist a decoupled thermal distribution of gravitons. Gravitational waves generated during inflation will be amplified by the process of stimulated emission into the existing thermal distribution of gravitons. Consequently the usual zero temperature scale invariant tensor spectrum is modified by a temperature dependent factor. This thermal correction factor amplify the B-mode polarization of the CMB by an order of magnitude at large angles, which may now be in the range of observability of WMAP.PACS numbers: PACS No.: 04.30. Db, 04.62.+v, 98.80.Cq Inflation [1], in addition to solving the horizon and flatness problems of the standard hot big-bang model, generates a nearly scale invariant density perturbations, which has been tested in the observations of the CMBR angular spectrum. One prediction of inflationary models which has not yet been tested is the existence of a nearly scale invariant spectrum of gravitational waves [2,3]. The definitive test of the existence of these cosmological gravitational waves would be the observation of B mode polarization in the CMB. The recent WMAP three year results [4] give only an upper bound on the B mode polarization, (l+1)l 2π C BB l=(2−6) < 0.05(µK) 2 .In this paper we show that if inflation was preceded by a radiation era then there would be a thermal background of gravitons at the time of inflation. This thermal distribution of gravitons would have decoupled close to Plank era. The generation of tensor perturbation during inflation would be by stimulated emission into this existing thermal background of gravitational waves. This process changes the power spectrum of tensor modes by an extra temperature dependent factor coth(k/2T ). At large angular scales (l ≤ 30) the power spectrum P T = A T k nT of gravitational waves generated during inflation would have a spectral index n T = −1 − 2ǫ, instead of the standard slow roll inflation prediction n T = −2ǫ which implies that C BB l=3 ≃ 10 × C BB l=30 . If a thermal enhancement of low l BB modes exists then it will be observable with WMAP or in the upcoming Planck [5] experiment. In the conclusion, we discuss the implications of inflationary models from the observations or non-observation of this low l thermal enhancement.

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confidence: 88%

Enhanced Polarization of the Cosmic Microwave Background Radiation from Thermal Gravitational Waves

2006

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“…CS modified gravity theories have been studied as models for parity violation [5] and leptogenesis [6], [7] in the early universe. CS models have also been used as effective theories where the CS term is radiatively generated via fermions coupling to gravity in a parity violating way [8].…”

Section: A Brief Review Of Cs Modified Gravitymentioning

confidence: 99%

Papapetrou energy-momentum tensor for Chern-Simons modified gravity

Guarrera

Hariton

2007

Phys. Rev. D

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We construct a conserved, symmetric energy-momentum (pseudo-)tensor for Chern-Simons modified gravity, thus demonstrating that the theory is Lorentz invariant. The tensor is discussed in relation to other gravitational energy-momentum tensors and analyzed for the Schwarzschild, Reissner-Nordstrom, and Friedmann-Robertson-Walker solutions. To our knowledge this is the first confirmation that the Reissner-Nordstrom and Friedmann-Robertson-Walker metrics are solutions of the modified theory.MIT-CTP 3810

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“…where γ is defined in (14). The relations (13) have been derived in [8] and for brevity we do not repeat the derivation here.…”

Section: Introductionmentioning

confidence: 99%

“…Further studies of the model were carried out for example in [11], where the cosmic no-hair theorem is tested within Gauge-flation with a Bianchi I background, in [12], where the background solutions of Gauge-flation were explored, and in [13], where it is shown that the theory can be embedded in the gravi-leptogenesis scenario of [14]. Recently, it was also shown [15,16] that Gauge-flation shares some background trajectories with Chromo-natural inflation [17], another recent model which assigns to non-Abelian gauge fields a crucial role in the dynamics of inflation and in the generation of primordial fluctuations (see [6] for a comprehensive review).…”

Section: Introductionmentioning

confidence: 99%

Gauge-flation confronted with Planck

Namba¹,

Dimastrogiovanni²,

Peloso³

2013

J. Cosmol. Astropart. Phys.

110

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Gauge-flation is a recently proposed model in which inflation is driven solely by a non-Abelian gauge field thanks to a specific higher order derivative operator. The nature of the operator is such that it does not introduce ghosts. We compute the cosmological scalar and tensor perturbations for this model, improving over an existing computation. We then confront these results with the Planck data. The model is characterized by the quantity γ ≡H 2 (where g is the gauge coupling constant, Q the vector vev, and H the Hubble rate). For γ < 2, the scalar perturbations show a strong tachyonic instability. In the stable region, the scalar power spectrum n s is too low at small γ, while the tensor-to-scalar ratio r is too high at large γ. No value of γ leads to acceptable values for n s and r, and so the model is ruled out by the CMB data. The same behavior with γ was obtained in Chromo-natural inflation, a model in which inflation is driven by a pseudo-scalar coupled to a non-Abelian gauge field. When the pseudo-scalar can be integrated out, one recovers the model of Gauge-flation plus corrections. It was shown that this identification is very accurate at the background level, but differences emerged in the literature concerning the perturbations of the two models. On the contrary, our results show that the analogy between the two models continues to be accurate also at the perturbative level.

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Leptogenesis from Gravity Waves in Models of Inflation

Cited by 318 publications

References 12 publications

Enhanced Polarization of the Cosmic Microwave Background Radiation from Thermal Gravitational Waves

Enhanced Polarization of the Cosmic Microwave Background Radiation from Thermal Gravitational Waves

Papapetrou energy-momentum tensor for Chern-Simons modified gravity

Gauge-flation confronted with Planck

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