from axion gauge couplings Ippei Obata Kyoto University PhD in preparation 29Nov CosPA2016 Primordial GWs from the inflation Energy scale of early Universe Redtilted Paritysymmetric ID: 830095
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Slide1
Blue Tensor Spectra (with slightly parity-violated) from axion-gauge couplings
Ippei Obata (Kyoto University, PhD)
(in preparation)
29_Nov_
CosPA2016
Slide2Primordial GWs from the inflation
Energy scale of early UniverseRed-tilted.
Parity-symmetric.
Tiny amplitude.
BICEP2/Keck Array (2016)
Tensor power
spectrum (
vacuum fluctuations):
info
Slide3Is it detectable directly?Ando (2013, DECIGO workshop)
Sensitivity curves of DECIGO:
if the source of GWs is
vacuum fluctuations
( r
= O(1) )
Slide4Additional sources of GWs
(One
helicity
mode enhancement!)
→Additional sources for scalar and
tensor
perturbations!
EOM for gauge field:
Sorbo
(2011), Barnaby et al. (2011),
…
(inflationary
axion
-gauge coupling)
Slide5Testable chiral blue
tensor spectrum
CMB
:
Starobinsky
type
: Chaotic type
: Hilltop
type
Preferable parameter region
Valerie
et al
. 2016
Tensor spectrum:
( r = O(0.01) )
Slide6Testable chiral blue
tensor spectrum
CMB
:
Starobinsky
type
: Chaotic type
: Hilltop
type
Preferable parameter region
Valerie
et al
. 2016
Tensor spectrum:
( r = O(0.01) )
Svrcek
& Witten (2005)
Natural scale predicted by the
h
eterotic
superstring!
Slide7Our question and studyWe explore the concrete model building based on the heterotic
string theory and reconsider the form of axion-gauge couplings.We found that rich varieties of blue tensor spectra could be provided
sourced by gauge fields coupled to two types of axions.
In t
his work
…
Question
…
Testable blue tensor spectrum
↔︎ EFT of the heterotic
string theory ? :
Slide8Axions from the heterotic superstring
Axions
arise from the B field:
“Model-independent” type
Choi &Kim (1985),
…
: its
field strength
“Model-dependent” type
compactification
Two types of
axion
Slide9Axions from the heterotic superstring
4-dim. reduced axion-gauge coupling
Anomaly cancellation
term:
Choi &Kim (1985),
…
Bianchi identity:
Model-independent
axion
:
Model-dependent
axion
:
Origin of
axion
-gauge couplings:
(omitting Lorentz indices)
Slide10Source of GWs from superstring
→ parity-symmetric blue tensor spectra!
Model example (1):
Slide11Source of GWs from superstring
→
slightly parity-violated blue tensor spectra!
Model example
(2):
diagonalising
Slide12Main Results BBO
ex:
Bule-tilted and slightly parity violated spectra.
Testable by future gravitational wave interferometers (DECIGO, BBO).
Avoiding the overproduction of scalar modes.
Slide13Summary & Outlook
Working in progress!We explore the concrete model building based on the heterotic string theory and reconsider the form of
axion-gauge couplings.
We found that rich varieties of blue tensor spectra sourced by gauge fields coupled to the model-(in)dependent
axion
could be provided.
?
Possible
potential forms of
axion, the non-Abelian gauge interaction,
…