A bstract Cosmological phase transitions in the primordial universe can produce anisotropic stochastic gravitational wave backgrounds (GWB), similar to the cosmic microwave background (CMB). For adiabatic perturbations, the fluctuations in GWB follow those in the CMB, but if primordial fluctuations carry an isocurvature component, this need no longer be true. It is shown that in non-minimal inflationary and reheating settings, primordial isocurvature can survive in GWB and exhibit significant non-Gaussianity (NG) in contrast to the CMB, while obeying current observational bounds. While probing such NG GWB is at best a marginal possibility at LISA, there is much greater scope at future proposed detectors such as DECIGO and BBO. It is even possible that the first observations of inflation-era NG could be made with gravitational wave detectors as opposed to the CMB or Large-Scale Structure surveys.
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Multifield positivity bounds for inflation
Positivity bounds represent nontrivial limitations on effective field theories (EFTs) if those EFTs are to be completed into a Lorentz-invariant, causal, local, and unitary framework. While such positivity bounds have been applied in a wide array of physical contexts to obtain useful constraints, their application to inflationary EFTs is subtle since Lorentz invariance is spontaneously broken during cosmic inflation. One path forward is to employ a
- Award ID(s):
- 2014071
- PAR ID:
- 10557020
- Publisher / Repository:
- JHEP 09 (2023) 041
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2023
- Issue:
- 9
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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A<sc>bstract</sc> Curvatons are light (compared to the Hubble scale during inflation) spectator fields during inflation that potentially contribute to adiabatic curvature perturbations post-inflation. They can alter CMB observables such as the spectral index
n s , the tensor-to-scalar ratior , and the local non-Gaussianity$$ {f}_{\textrm{NL}}^{\left(\textrm{loc}\right)} $$ n s andr observational constraints but can be made viable with a significant contribution from what we call a savior curvaton, a large$$ \left|{f}_{\textrm{NL}}^{\left(\textrm{loc}\right)}\right| $$ > 0. 05, such that the model is distinguishable from single-field inflation, is inevitable. On the other hand, when the underlying inflation model already satisfies then s andr observational constraints, so significant curvaton contribution is forbidden, a large$$ \left|{f}_{\textrm{NL}}^{\left(\textrm{loc}\right)}\right| $$ > 0. 05 is possible in the exceptional case when the isocurvature fluctuation in the curvaton fluid is much greater than the global curvature fluctuation. -
Abstract Dark radiation (DR) appears as a new physics candidate in various scenarios beyond the Standard Model. While it is often assumed that perturbations in DR are adiabatic, they can easily have an isocurvature component if more than one field was present during inflation, and whose decay products did not all thermalize with each other.By implementing the appropriate isocurvature initial conditions (IC), we derive the constraints on both uncorrelated and correlated DR density isocurvature perturbations from the full Planck 2018 data alone, and also in combination with other cosmological data sets.Our study on free-streaming DR (FDR) updates and generalizes the existing bound on neutrino density isocurvature perturbations by including a varying number of relativistic degrees of freedom, and for coupled DR (CDR) isocurvature, we derive the first bound. We also show that for CDRqualitatively new physical effects arise compared to FDR. One such effect is that for isocurvature IC, FDR gives rise to larger CMB anisotropies compared to CDR — contrary to the adiabatic case.More generally, we find that a blue-tilt of DR isocurvature spectrum is preferred. This gives rise to a larger value of the Hubble constant H 0 compared to the standard ΛCDM+Δ N eff cosmology with adiabatic spectra and relaxes the H 0 tension.more » « less
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A<sc>bstract</sc> A model of supergravity inflation we recently proposed can produce slow roll inflation and a realistic spectrum of particles even without F-term supersymmetry breaking. Supersymmetry is broken only by a D-term induced by a recently discovered new type of Fayet-Iliopoulos (FI) term. Almost all supersymmetric partners of the standard model fields can get masses as high as the inflationary Hubble scale. The exception is gauginos, for which the vanishing of F-terms implies an exact cancellation that keeps their masses exactly zero. To cure this problem without spoiling the simplicity of our model we introduce a new term that further enlarges the space of supergravity effective actions. It is an F-term that, similarly to the new FI term, becomes singular in the supersymmetric limit. We show that this term can produce large gaugino masses without altering the spectrum of other states and without lowering the cutoff of the effecive theory.
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We calculate high-precision constraints on Natural Inflation relative to current observational constraints from Planck 2018 + BICEP/Keck(BK15) Polarization + BAO on r and n_{S} , including post-inflationary history of the universe. We find that, for conventional post-inflationary dynamics, Natural Inflation with a cosine potential is disfavored at greater than 95% confidence out by current data. If we assume protracted reheating characterized by w̅>1/3, Natural Inflation can be brought into agreement with current observational constraints. However, bringing unmodified Natural Inflation into the 68% confidence region requires values of T_{re} below the scale of electroweak symmetry breaking. The addition of a SHOES prior on the Hubble Constant H_{0} only worsens the fit.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/JHEP09(2023)041
