TY - JOUR
T1 - Inflationary physics and trans-Planckian conjecture in the stringy running vacuum model
T2 - from the phantom vacuum to the true vacuum
AU - Mavromatos, Nick E.
AU - Solà Peracaula, Joan
N1 - Funding Information:
The work of NEM is supported in part by the UK Science and Technology Facilities research Council (STFC) under the Research Grant ST/T000759/1. The work of JS has been partially supported by Projects PID2019-105614GB-C21 and FPA2016-76005-C2-1-P (MINECO, Spain), 2017-SGR-929 (Generalitat de Catalunya) and CEX2019-000918-M (ICCUB). The authors also acknowledge participation in the COST Association Action CA18108 ?Quantum Gravity Phenomenology in the Multimessenger Approach (QG-MM) ?.
Funding Information:
The work of NEM is supported in part by the UK Science and Technology Facilities research Council (STFC) under the Research Grant ST/T000759/1. The work of JS has been partially supported by Projects PID2019-105614GB-C21 and FPA2016-76005-C2-1-P (MINECO, Spain), 2017-SGR-929 (Generalitat de Catalunya) and CEX2019-000918-M (ICCUB). The authors also acknowledge participation in the COST Association Action CA18108 “Quantum Gravity Phenomenology in the Multimessenger Approach (QG-MM)”.
Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Società Italiana di Fisica and Springer-Verlag GmbH Germany, part of Springer Nature.
PY - 2021/11
Y1 - 2021/11
N2 - In previous works, we have embedded the running vacuum model (RVM) of cosmology in the framework of string theory. Specifically, we considered a string-inspired cosmology with primordial gravitational waves (GW) and gravitational anomalies, which were argued to lead, via appropriate condensation during the very-early-universe era, to dynamical inflation, of RVM type, without the need for extra inflaton fields. A crucial role for the associated slow-roll nature of the inflationary era was played by the fundamental axion field that exists in the gravitational multiplet of strings, viz. the Kalb–Ramond (KR) axion. In this paper, we study further this model and demonstrate several novel facts, completing our previous studies. We clarify the different roles played by the background KR axions, which constitute a form of stiff matter that dominates a pre-RVM-inflationary epoch of the Universe. We show that the KR axion when combined with the gravitational Chern–Simons contribution obeys together a peculiar equation of state p= - ρ, with negative energy density ρ< 0 , which we call ‘phantom vacuum’. Eventually, this state transmutes into the standard vacuum state thanks to the contribution from the gravitational Chern–Simons condensate, which makes the total ρtotal= - ptotal> 0. At this point the RVM vacuum picture emerges naturally, with an overall equation of state of true vacuum type. We find that our scenario is consistent with the trans-Planckian censorship hypothesis, given that the rate of change of the KR axion takes only sub-Planckian values. We also discuss some explicit scenarios on the creation of GWs within the context of supergravity models that could be embedded in our string theory framework. Finally, we argue how the RVM in our context can help to alleviate the current tensions of the Λ CDM.
AB - In previous works, we have embedded the running vacuum model (RVM) of cosmology in the framework of string theory. Specifically, we considered a string-inspired cosmology with primordial gravitational waves (GW) and gravitational anomalies, which were argued to lead, via appropriate condensation during the very-early-universe era, to dynamical inflation, of RVM type, without the need for extra inflaton fields. A crucial role for the associated slow-roll nature of the inflationary era was played by the fundamental axion field that exists in the gravitational multiplet of strings, viz. the Kalb–Ramond (KR) axion. In this paper, we study further this model and demonstrate several novel facts, completing our previous studies. We clarify the different roles played by the background KR axions, which constitute a form of stiff matter that dominates a pre-RVM-inflationary epoch of the Universe. We show that the KR axion when combined with the gravitational Chern–Simons contribution obeys together a peculiar equation of state p= - ρ, with negative energy density ρ< 0 , which we call ‘phantom vacuum’. Eventually, this state transmutes into the standard vacuum state thanks to the contribution from the gravitational Chern–Simons condensate, which makes the total ρtotal= - ptotal> 0. At this point the RVM vacuum picture emerges naturally, with an overall equation of state of true vacuum type. We find that our scenario is consistent with the trans-Planckian censorship hypothesis, given that the rate of change of the KR axion takes only sub-Planckian values. We also discuss some explicit scenarios on the creation of GWs within the context of supergravity models that could be embedded in our string theory framework. Finally, we argue how the RVM in our context can help to alleviate the current tensions of the Λ CDM.
UR - http://www.scopus.com/inward/record.url?scp=85119406209&partnerID=8YFLogxK
U2 - 10.1140/epjp/s13360-021-02149-6
DO - 10.1140/epjp/s13360-021-02149-6
M3 - Article
AN - SCOPUS:85119406209
SN - 2190-5444
VL - 136
JO - European Physical Journal Plus
JF - European Physical Journal Plus
IS - 11
M1 - 1152
ER -