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Title: Leptogenesis from Gravity Waves in Models of Inflation

Abstract

We present a new mechanism for creating the observed cosmic matter-antimatter asymmetry which satisfies all three Sakharov conditions from one common thread, gravitational waves. We generate lepton number through the gravitational anomaly in the lepton number current. The source term comes from elliptically polarized gravity waves that are produced during inflation if the inflaton field contains a CP-odd component. The amount of matter asymmetry generated in our model can be of realistic size for the parameters within the range of some inflationary scenarios and grand unified theories.

Authors:
; ;  [1]
  1. Stanford Linear Accelerator Center, Post Office Box 20450, Stanford, California 94309 (United States) and Department of Physics, Stanford University, 382 via Pueblo Mall, Stanford California 94305-4060 (United States)
Publication Date:
OSTI Identifier:
20778721
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review Letters; Journal Volume: 96; Journal Issue: 8; Other Information: DOI: 10.1103/PhysRevLett.96.081301; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ANTIMATTER; ASYMMETRY; COSMOLOGY; CP INVARIANCE; GRAND UNIFIED THEORY; GRAVITATIONAL WAVES; GRAVITY WAVES; INFLATIONARY UNIVERSE; LEPTON NUMBER

Citation Formats

Alexander, Stephon H. S., Peskin, Michael E., and Sheikh-Jabbari, M.M.. Leptogenesis from Gravity Waves in Models of Inflation. United States: N. p., 2006. Web. doi:10.1103/PHYSREVLETT.96.0.
Alexander, Stephon H. S., Peskin, Michael E., & Sheikh-Jabbari, M.M.. Leptogenesis from Gravity Waves in Models of Inflation. United States. doi:10.1103/PHYSREVLETT.96.0.
Alexander, Stephon H. S., Peskin, Michael E., and Sheikh-Jabbari, M.M.. Fri . "Leptogenesis from Gravity Waves in Models of Inflation". United States. doi:10.1103/PHYSREVLETT.96.0.
@article{osti_20778721,
title = {Leptogenesis from Gravity Waves in Models of Inflation},
author = {Alexander, Stephon H. S. and Peskin, Michael E. and Sheikh-Jabbari, M.M.},
abstractNote = {We present a new mechanism for creating the observed cosmic matter-antimatter asymmetry which satisfies all three Sakharov conditions from one common thread, gravitational waves. We generate lepton number through the gravitational anomaly in the lepton number current. The source term comes from elliptically polarized gravity waves that are produced during inflation if the inflaton field contains a CP-odd component. The amount of matter asymmetry generated in our model can be of realistic size for the parameters within the range of some inflationary scenarios and grand unified theories.},
doi = {10.1103/PHYSREVLETT.96.0},
journal = {Physical Review Letters},
number = 8,
volume = 96,
place = {United States},
year = {Fri Mar 03 00:00:00 EST 2006},
month = {Fri Mar 03 00:00:00 EST 2006}
}
  • In this talk we present a mechanism for leptogenesis which is based on gravity waves produced during inflation. We show that when inflation is driven by a pseudo-scalar field the metric perturbations generated during inflation can become birefringent, therefore giving a non-vanishing contribution to the gravitational triangle anomaly and sourcing lepton anti-lepton asymmetry. As this asymmetry is sourced by the fields which are active during inflation, it is not washed out or diluted by inflation. The amount of matter asymmetry generated in our model can be of realistic size for the parameters within the range of some inflationary scenarios andmore » grand unified theories.« less
  • The energy levels of the left- and the right-handed neutrinos are split in the background of gravitational waves generated during inflation, which, in presence of lepton-number-violating interactions, gives rise to a net lepton asymmetry at equilibrium. Lepton number violation is achieved by the same dimension five operator which gives rise to neutrino masses after electroweak symmetry breaking. A net baryon asymmetry of the same magnitude can be generated from this lepton asymmetry by electroweak sphaleron processes.
  • Wrapped branes in string compactifications introduce a monodromy that extends the field range of individual closed-string axions to beyond the Planck scale. Furthermore, approximate shift symmetries of the system naturally control corrections to the axion potential. This suggests a general mechanism for chaotic inflation driven by monodromy-extended closed-string axions. We systematically analyze this possibility and show that the mechanism is compatible with moduli stabilization and can be realized in many types of compactifications, including warped Calabi-Yau manifolds and more general Ricci-curved spaces. In this broad class of models, the potential is linear in the canonical inflaton field, predicting a tensormore » to scalar ratio r {approx} 0.07 accessible to upcoming cosmic microwave background (CMB) observations.« less
  • We evaluate both the spectral energy density and the total energy density for relic gravity waves produced during the transition from an early inflationary phase to a matter-dominated Friedmann-Robertson-Walker-type expansion: {ital a}{similar to}{ital t}{sup {ital c}} ({ital c}{lt}1). We find that for power-law inflation the spectral energy density for gravity waves has more power on larger scales than for purely exponential inflation. Evaluating the energy density of created massless particles (both gravitons and massless scalars) we find that in the case of exponential inflation the ratio of the density of created particles to the total density of matter is amore » constant, if {ital c}{ge}1/2. This unusual behavior is a consequence of the fact that the equation of state for created particles mimics the equation of state for matter driving the expansion of the Universe. As a result, self-consistent solutions of the Einstein equations can be found, in which the expansion of the Universe is sustained solely by the ongoing production of massless particles, so that {ital G}{sub {mu}{nu}}=8{pi}{ital G}{l angle}{ital T}{sub {mu}{nu}}{r angle}. In the case of power-law and quasiexponential inflation we find that the ratio of the energy density of gravity waves to the background matter density increases with time, as gravity waves with longer wavelengths and larger amplitudes enter the horizon at successively later epochs. This could lead to the energy density of gravity waves becoming comparable to the energy density of matter at late times, if inflation commenced at Planckian energies.« less
  • We calculate the amplitude of gravitational waves produced by inflation on a de Sitter brane embedded in five-dimensional anti-de Sitter bulk space-time, extending previous calculations in Randall-Sundrum type cosmology to include the effect of induced gravity corrections on the brane. These corrections arise via a term in the brane action that is proportional to the brane Ricci scalar. We find that, as in the Randall-Sundrum case, there is a mass-gap between the discrete zero-mode and a continuum of massive bulk modes, which are too heavy to be excited during inflation. We give the normalization of the zero-mode as a functionmore » of the Hubble rate on the brane and are thus able to calculate the high-energy correction to the spectrum of gravitational wave (tensor) modes excited on large scales during inflation from initial vacuum fluctuations on small scales. We also calculate the amplitude of density (scalar) perturbations expected due to inflaton fluctuations on the brane, and show that the usual four-dimensional consistency relation for the tensor/scalar ratio remains valid for brane inflation with induced gravity corrections.« less