Abstract
One class of single-field inflationary models compatible with the recently-conjectured Swampland criteria would be those in which a Hubble slow-roll arameter ϵH is not the same as ϵV ∼ (V′/V)2. However, a roadblock for these models (with a convex potential) lie in the unacceptably high tensor-to-scalar ratio, r, generically predicted by them. In this work, illustrating through an explicit example, we point out that having a non-Bunch-Davies component to the initial state of cosmological perturbations makes the value of r compatible with observations. In this way, we lay down a new path even for standard models of slow-roll inflation to be consistent with the Swampland criteria by invoking deviations from the Bunch-Davies initial state.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
C. Vafa, The string landscape and the swampland, hep-th/0509212 [INSPIRE].
N. Arkani-Hamed, L. Motl, A. Nicolis and C. Vafa, The string landscape, black holes and gravity as the weakest force, JHEP 06 (2007) 060 [hep-th/0601001] [INSPIRE].
G. Obied, H. Ooguri, L. Spodyneiko and C. Vafa, De Sitter space and the swampland, arXiv:1806.08362 [INSPIRE].
D. Andriot, On the de Sitter swampland criterion, Phys. Lett. B 785 (2018) 570 [arXiv:1806.10999] [INSPIRE].
P. Agrawal, G. Obied, P.J. Steinhardt and C. Vafa, On the cosmological implications of the string swampland, Phys. Lett. B 784 (2018) 271 [arXiv:1806.09718] [INSPIRE].
W.H. Kinney, S. Vagnozzi and L. Visinelli, The zoo plot meets the swampland: mutual (in)consistency of single-field inflation, string conjectures and cosmological data, arXiv:1808.06424 [INSPIRE].
A. Achúcarro and G.A. Palma, The string swampland constraints require multi-field inflation, JCAP 02 (2019) 041 [arXiv:1807.04390] [INSPIRE].
S.K. Garg and C. Krishnan, Bounds on slow roll and the de Sitter swampland, arXiv:1807.05193 [INSPIRE].
H. Ooguri and C. Vafa, On the geometry of the string landscape and the swampland, Nucl. Phys. B 766 (2007) 21 [hep-th/0605264] [INSPIRE].
D. Klaewer and E. Palti, Super-Planckian spatial field variations and quantum gravity, JHEP 01 (2017) 088 [arXiv:1610.00010] [INSPIRE].
R. Blumenhagen, I. Valenzuela and F. Wolf, The swampland conjecture and F-term axion monodromy inflation, JHEP 07 (2017) 145 [arXiv:1703.05776] [INSPIRE].
H. Ooguri and C. Vafa, Non-supersymmetric AdS and the swampland, Adv. Theor. Math. Phys. 21 (2017) 1787 [arXiv:1610.01533] [INSPIRE].
U.H. Danielsson and T. Van Riet, What if string theory has no de Sitter vacua?, Int. J. Mod. Phys. D 27 (2018) 1830007 [arXiv:1804.01120] [INSPIRE].
S. Sethi, Supersymmetry breaking by fluxes, JHEP 10 (2018) 022 [arXiv:1709.03554] [INSPIRE].
T.D. Brennan, F. Carta and C. Vafa, The string landscape, the swampland and the missing corner, PoS(TASI2017)015 (2017) [arXiv:1711.00864] [INSPIRE].
M. Dias, J. Frazer, A. Retolaza and A. Westphal, Primordial gravitational waves and the swampland, Fortsch. Phys. 67 (2019) 1800063 [arXiv:1807.06579] [INSPIRE].
V. Sahni, M. Sami and T. Souradeep, Relic gravity waves from brane world inflation, Phys. Rev. D 65 (2002) 023518 [gr-qc/0105121] [INSPIRE].
T. Shiromizu, K.-I. Maeda and M. Sasaki, The Einstein equation on the 3-brane world, Phys. Rev. D 62 (2000) 024012 [gr-qc/9910076] [INSPIRE].
R. Maartens, D. Wands, B.A. Bassett and I. Heard, Chaotic inflation on the brane, Phys. Rev. D 62 (2000) 041301 [hep-ph/9912464] [INSPIRE].
M. Wali Hossain, R. Myrzakulov, M. Sami and E.N. Saridakis, Unification of inflation and dark energy à la quintessential inflation, Int. J. Mod. Phys. D 24 (2015) 1530014 [arXiv:1410.6100] [INSPIRE].
G.N. Felder, L. Kofman and A.D. Linde, Instant preheating, Phys. Rev. D 59 (1999) 123523 [hep-ph/9812289] [INSPIRE].
G.N. Felder, L. Kofman and A.D. Linde, Inflation and preheating in NO models, Phys. Rev. D 60 (1999) 103505 [hep-ph/9903350] [INSPIRE].
L. Heisenberg, M. Bartelmann, R. Brandenberger and A. Refregier, Dark energy in the swampland, Phys. Rev. D 98 (2018) 123502 [arXiv:1808.02877] [INSPIRE].
E. Ó. Colgáin, M.H. P.M. Van Putten and H. Yavartanoo, Observational consequences of H 0 tension in de Sitter swampland, arXiv:1807.07451 [INSPIRE].
K. Dutta, Ruchika, A. Roy, A.A. Sen and M.M. Sheikh-Jabbari, Negative cosmological constant is consistent with cosmological data, arXiv:1808.06623 [INSPIRE].
Y. Akrami, R. Kallosh, A. Linde and V. Vardanyan, The landscape, the swampland and the era of precision cosmology, Fortsch. Phys. 67 (2019) 1800075 [arXiv:1808.09440] [INSPIRE].
M.C. Bento, R.G. Felipe and N.M.C. Santos, Brane assisted quintessential inflation with transient acceleration, Phys. Rev. D 77 (2008) 123512 [arXiv:0801.3450] [INSPIRE].
Planck collaboration, Planck 2015 results. XX. Constraints on inflation, Astron. Astrophys. 594 (2016) A20 [arXiv:1502.02114] [INSPIRE].
U.H. Danielsson, A note on inflation and trans-Planckian physics, Phys. Rev. D 66 (2002) 023511 [hep-th/0203198] [INSPIRE].
N. Agarwal, R. Holman, A.J. Tolley and J. Lin, Effective field theory and non-Gaussianity from general inflationary states, JHEP 05 (2013) 085 [arXiv:1212.1172] [INSPIRE].
S. Kundu, Inflation with general initial conditions for scalar perturbations, JCAP 02 (2012) 005 [arXiv:1110.4688] [INSPIRE].
S. Kundu, Non-Gaussianity consistency relations, initial states and back-reaction, JCAP 04 (2014) 016 [arXiv:1311.1575] [INSPIRE].
U.H. Danielsson, Inflation, holography and the choice of vacuum in de Sitter space, JHEP 07 (2002) 040 [hep-th/0205227] [INSPIRE].
A. Dey and S. Paban, Non-Gaussianities in the cosmological perturbation spectrum due to primordial anisotropy, JCAP 04 (2012) 039 [arXiv:1106.5840] [INSPIRE].
A. Dey, E. Kovetz and S. Paban, Non-Gaussianities in the cosmological perturbation spectrum due to primordial anisotropy II, JCAP 10 (2012) 055 [arXiv:1205.2758] [INSPIRE].
L. Lello, D. Boyanovsky and R. Holman, Pre-slow roll initial conditions: large scale power suppression and infrared aspects during inflation, Phys. Rev. D 89 (2014) 063533 [arXiv:1307.4066] [INSPIRE].
J. Martin and R.H. Brandenberger, The trans-Planckian problem of inflationary cosmology, Phys. Rev. D 63 (2001) 123501 [hep-th/0005209] [INSPIRE].
A. Kempf, Mode generating mechanism in inflation with cutoff, Phys. Rev. D 63 (2001) 083514 [astro-ph/0009209] [INSPIRE].
K. Sugimura and E. Komatsu, Bispectrum from open inflation, JCAP 11 (2013) 065 [arXiv:1309.1579] [INSPIRE].
G. Shiu and J. Xu, Effective field theory and decoupling in multi-field inflation: an illustrative case study, Phys. Rev. D 84 (2011) 103509 [arXiv:1108.0981] [INSPIRE].
I. Agullo, Loop quantum cosmology, non-Gaussianity and CMB power asymmetry, Phys. Rev. D 92 (2015) 064038 [arXiv:1507.04703] [INSPIRE].
L. Hui and W.H. Kinney, Short distance physics and the consistency relation for scalar and tensor fluctuations in the inflationary universe, Phys. Rev. D 65 (2002) 103507 [astro-ph/0109107] [INSPIRE].
J. Ganc, Calculating the local-type f NL for slow-roll inflation with a non-vacuum initial state, Phys. Rev. D 84 (2011) 063514 [arXiv:1104.0244] [INSPIRE].
S. Brahma, E. Nelson and S. Shandera, Fossilized gravitational wave relic and primordial clocks, Phys. Rev. D 89 (2014) 023507 [arXiv:1310.0471] [INSPIRE].
A. Ashoorioon, K. Dimopoulos, M.M. Sheikh-Jabbari and G. Shiu, Reconciliation of high energy scale models of inflation with Planck, JCAP 02 (2014) 025 [arXiv:1306.4914] [INSPIRE].
R. Flauger, D. Green and R.A. Porto, On squeezed limits in single-field inflation. Part I, JCAP 08 (2013) 032 [arXiv:1303.1430] [INSPIRE].
R. Holman and A.J. Tolley, Enhanced non-Gaussianity from excited initial states, JCAP 05 (2008) 001 [arXiv:0710.1302] [INSPIRE].
A. Ashoorioon, Rescuing single field inflation from the swampland, Phys. Lett. B 790 (2019) 568 [arXiv:1810.04001] [INSPIRE].
A. Kehagias and A. Riotto, A note on inflation and the swampland, Fortsch. Phys. 66 (2018) 1800052 [arXiv:1807.05445] [INSPIRE].
BICEP2 and Planck collaborations, Joint analysis of BICEP2/Keck Array and Planck data, Phys. Rev. Lett. 114 (2015) 101301 [arXiv:1502.00612] [INSPIRE].
J.M. Maldacena, Non-Gaussian features of primordial fluctuations in single field inflationary models, JHEP 05 (2003) 013 [astro-ph/0210603] [INSPIRE].
C. Cheung, P. Creminelli, A.L. Fitzpatrick, J. Kaplan and L. Senatore, The effective field theory of inflation, JHEP 03 (2008) 014 [arXiv:0709.0293] [INSPIRE].
M.W. Hossain, R. Myrzakulov, M. Sami and E.N. Saridakis, Evading Lyth bound in models of quintessential inflation, Phys. Lett. B 737 (2014) 191 [arXiv:1405.7491] [INSPIRE].
F. Denef, A. Hebecker and T. Wrase, De Sitter swampland conjecture and the Higgs potential, Phys. Rev. D 98 (2018) 086004 [arXiv:1807.06581] [INSPIRE].
U. Danielsson, The quantum swampland, arXiv:1809.04512 [INSPIRE].
Open Access
This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.
Author information
Authors and Affiliations
Corresponding author
Additional information
ArXiv ePrint: 1809.01277
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.
The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.
To view a copy of this licence, visit https://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Brahma, S., Hossain, M.W. Avoiding the string swampland in single-field inflation: excited initial states. J. High Energ. Phys. 2019, 6 (2019). https://doi.org/10.1007/JHEP03(2019)006
Received:
Revised:
Accepted:
Published:
DOI: https://doi.org/10.1007/JHEP03(2019)006