We present a series of theoretical constraints on the potentially viable inflation models that might yield a blue spectrum for primordial tensor perturbations. By performing a detailed dynamical analysis we show that, while there exists such possibility, the corresponding phase space is strongly bounded. Our result implies that, in order to achieve a blue tilt for inflationary tensor perturbations, one may either construct a non-canonical inflation model delicately, or study the generation of primordial tensor modes beyond the standard scenario of single slow-roll field.
Bibliographical noteFunding Information:
We thank Robert Brandenberger, Genly Leon, Jerome Quintin and Yi Wang for useful discussions. YFC thanks the Asia Pacific Center for Theoretical Physics for warmest hospitality during his visit. YFC is supported in part by the Chinese National Youth Thousand Talents Program , by the USTC start-up funding (Grant No. KY2030000049 ), by the Natural Sciences and Engineering Research Council ( NSERC ) of Canada and the Department of Physics at McGill . JG and SP acknowledge the Max-Planck-Gesellschaft , the Korea Ministry of Education, Science and Technology , Gyeongsangbuk-Do and Pohang City for the support of the Independent Junior Research Group at the Asia Pacific Center for Theoretical Physics. They are also supported in part by a Starting Grant through the Basic Science Research Program of the National Research Foundation of Korea ( 2013R1A1A1006701 ). The research of ENS is implemented within the framework of the Operational Program “Education and Lifelong Learning” (Actions Beneficiary: General Secretariat for Research and Technology), and is co-financed by the European Social Fund (ESF) and the Greek State . SYW was supported by Ministry of Science and Technology, Taiwan and the National Center of Theoretical Science in Taiwan .
© 2015 The Authors.