Perhaps the greatest challenge for fundamental theories based on compactification from extra dimensions is accommodating a period of accelerated cosmological expansion. Previous studies have identified constraints imposed by the existence of dark energy for two overlapping classes of compactified theories: (1) those in which the higher dimensional picture satisfies certain metric properties selected to reproduce known low energy phenomenology; or (2) those derived from string theory assuming they satisfy the Swampland conjectures. For either class, the analyses showed that dark energy is only possible if it takes the form of quintessence. In this paper, we explore the consequences for theories that belong to both classes and show that the joint constraints are highly restrictive, leaving few options.
Warm natural inflation is studied for the case of the original cosine potential. The
radiation bath during inflation induces a dissipation (friction) rate in the equation of motion
for the inflaton field, which can potentially reduce the field excursion needed for an
observationally viable period of inflation. We examine if the dissipation thus provides a
mechanism to avoid the large decay constant f ≳ M
pl of cold cosine natural
inflation. Whereas temperature independent dissipation has previously been shown to alleviate the
need for a trans-Planckian decay constant f, we illustrate here the difficulties of
accommodating a significantly sub-Planckian decay constant (f < 10-1
M
pl) for the
case of a temperature dependent dissipation rate in the form Γ ∝ Tc
, with
c = {1,3}. Such dissipation rates represent physically well-motivated constructions in the
literature. For each model, we map its location in the r-ns
plane and compare with cosmic
microwave background (CMB) data. For c = 1 (c = 3), we find that agreement with CMB data requires
that dissipation be in the weak (moderate) regime and that the minimum allowed value of the decay
constant in the potential is f
min = 0.3 (0.8) M
pl, respectively.
We present a novel application of partial convolutional neural networks (PCNN) that can inpaint masked images of the cosmic microwave background. The network can reconstruct both the maps and the power spectra to a few percent for circular and irregularly shaped masks covering up to 10% of the image area. By performing a Kolmogorov-Smirnov test we show that the reconstructed maps and power spectra are indistinguishable from the input maps and power spectra at the 99.9% level. Moreover, we show that PCNNs can inpaint maps with regular and irregular masks to the same accuracy. This should be particularly beneficial to inpaint irregular masks for the CMB that come from astrophysical sources such as Galactic foregrounds. The proof of concept application shown in this paper shows that PCNNs can be an important tool in data analysis pipelines in cosmology.
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