### Abstract

A nice paper by Morrison [arXiv:1302.1860] demonstrates the recent convergence of opinion that has taken place concerning the graviton propagator on de Sitter background. We here discuss the few points which remain under dispute. First, the inevitable decay of tachyonic scalars really does result in their 2-point functions breaking de Sitter invariance. This is obscured by analytic continuation techniques which produce formal solutions to the propagator equation that are not propagators. Second, Morrison's de Sitter invariant solution for the spin two sector of the graviton propagator involves derivatives of the scalar propagator at M2=0, where it is not meromorphic unless de Sitter breaking is permitted. Third, de Sitter breaking does not require zero modes. Fourth, the ambiguity Morrison claims in the equation for the spin two structure function is fixed by requiring it to derive from a mode sum. Fifth, Morrison's spin two sector is not "physically equivalent" to ours because their coincidence limits differ. Finally, it is only the noninvariant propagator that gets the time independence and scale invariance of the tensor power spectrum correctly.

Original language | English |
---|---|

Article number | 104004 |

Journal | Physical Review D - Particles, Fields, Gravitation and Cosmology |

Volume | 89 |

Issue number | 10 |

DOIs | |

Publication status | Published - 2014 May 2 |

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### All Science Journal Classification (ASJC) codes

- Nuclear and High Energy Physics
- Physics and Astronomy (miscellaneous)

### Cite this

*Physical Review D - Particles, Fields, Gravitation and Cosmology*,

*89*(10), [104004]. https://doi.org/10.1103/PhysRevD.89.104004

}

*Physical Review D - Particles, Fields, Gravitation and Cosmology*, vol. 89, no. 10, 104004. https://doi.org/10.1103/PhysRevD.89.104004

**Perils of analytic continuation.** / Miao, Shun-Pei; Mora, P. J.; Tsamis, N. C.; Woodard, R. P.

Research output: Contribution to journal › Article

TY - JOUR

T1 - Perils of analytic continuation

AU - Miao, Shun-Pei

AU - Mora, P. J.

AU - Tsamis, N. C.

AU - Woodard, R. P.

PY - 2014/5/2

Y1 - 2014/5/2

N2 - A nice paper by Morrison [arXiv:1302.1860] demonstrates the recent convergence of opinion that has taken place concerning the graviton propagator on de Sitter background. We here discuss the few points which remain under dispute. First, the inevitable decay of tachyonic scalars really does result in their 2-point functions breaking de Sitter invariance. This is obscured by analytic continuation techniques which produce formal solutions to the propagator equation that are not propagators. Second, Morrison's de Sitter invariant solution for the spin two sector of the graviton propagator involves derivatives of the scalar propagator at M2=0, where it is not meromorphic unless de Sitter breaking is permitted. Third, de Sitter breaking does not require zero modes. Fourth, the ambiguity Morrison claims in the equation for the spin two structure function is fixed by requiring it to derive from a mode sum. Fifth, Morrison's spin two sector is not "physically equivalent" to ours because their coincidence limits differ. Finally, it is only the noninvariant propagator that gets the time independence and scale invariance of the tensor power spectrum correctly.

AB - A nice paper by Morrison [arXiv:1302.1860] demonstrates the recent convergence of opinion that has taken place concerning the graviton propagator on de Sitter background. We here discuss the few points which remain under dispute. First, the inevitable decay of tachyonic scalars really does result in their 2-point functions breaking de Sitter invariance. This is obscured by analytic continuation techniques which produce formal solutions to the propagator equation that are not propagators. Second, Morrison's de Sitter invariant solution for the spin two sector of the graviton propagator involves derivatives of the scalar propagator at M2=0, where it is not meromorphic unless de Sitter breaking is permitted. Third, de Sitter breaking does not require zero modes. Fourth, the ambiguity Morrison claims in the equation for the spin two structure function is fixed by requiring it to derive from a mode sum. Fifth, Morrison's spin two sector is not "physically equivalent" to ours because their coincidence limits differ. Finally, it is only the noninvariant propagator that gets the time independence and scale invariance of the tensor power spectrum correctly.

UR - http://www.scopus.com/inward/record.url?scp=84900838104&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84900838104&partnerID=8YFLogxK

U2 - 10.1103/PhysRevD.89.104004

DO - 10.1103/PhysRevD.89.104004

M3 - Article

VL - 89

JO - Physical review D: Particles and fields

JF - Physical review D: Particles and fields

SN - 1550-7998

IS - 10

M1 - 104004

ER -