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@ARTICLE{Cicoli:600392,
      author       = {Cicoli, Michele and Guidetti, Veronica and Muia, Francesco
                      and Pedro, Francisco G. and Vacca, Gian Paolo},
      title        = {{O}n the choice of entropy variables in multifield
                      inflation},
      journal      = {Classical and quantum gravity},
      volume       = {40},
      number       = {2},
      issn         = {0264-9381},
      address      = {Bristol},
      publisher    = {IOP Publ.},
      reportid     = {PUBDB-2023-07949, arXiv:2107.03391. DESY-21-106},
      pages        = {025008},
      year         = {2023},
      note         = {20 pages + appendices, 3 figures},
      abstract     = {We discuss the usefulness and theoretical consistency of
                      different entropy variables used in the literature to
                      describe isocurvature perturbations in multifield
                      inflationary models with a generic curved field space. We
                      clarify which is the proper entropy variable to be used to
                      match the evolution of isocurvature modes during inflation
                      to the one after the reheating epoch in order to compare
                      with observational constraints. In particular, we find that
                      commonly used variables, as the relative entropy
                      perturbation or the one associated to the decomposition in
                      tangent and normal perturbations with respect to the
                      inflationary trajectory, even if more useful to perform
                      numerical studies, can lead to results which are wrong by
                      several orders of magnitude, or even to apparent
                      destabilisation effects which are unphysical for cases with
                      light kinetically coupled spectator fields.},
      keywords     = {entropy: perturbation (INSPIRE) / inflation: model
                      (INSPIRE) / isocurvature: perturbation (INSPIRE) /
                      trajectory (INSPIRE) / reheating (INSPIRE) / spectator
                      (INSPIRE) / curvature (INSPIRE) / stability (INSPIRE) /
                      coupling (INSPIRE) / kinetic (INSPIRE) / multifield
                      inflation (autogen) / isocurvature modes (autogen) / entropy
                      perturbations (autogen)},
      cin          = {T},
      ddc          = {530},
      cid          = {I:(DE-H253)T-20120731},
      pnm          = {611 - Fundamental Particles and Forces (POF4-611) /
                      STRINGFLATION - Inflation in String Theory - Connecting
                      Quantum Gravity with Observations (647995)},
      pid          = {G:(DE-HGF)POF4-611 / G:(EU-Grant)647995},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)16},
      eprint       = {2107.03391},
      howpublished = {arXiv:2107.03391},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2107.03391;\%\%$},
      UT           = {WOS:000905279400001},
      doi          = {10.1088/1361-6382/acabf7},
      url          = {https://bib-pubdb1.desy.de/record/600392},
}