Narrow Results

Swampland Conjectures have attracted quite some interest in the Cosmological Community. They have been shown to have wide ranging implications, like constraints on inflationary models, primordial black holes, etc. to name a few. A particularly revealing insight on dark energy also shows that one can have the dark energy equation-of-state for a quintessence scenario to be significantly different than $-1$ after one takes into account the refined dS conjecture. Another interesting issue with the swampland conjectures is that they have been shown to be incompatible with single field inflationary models in GR-based cosmology. In our previous work, we have, however, shown that single field inflationary models are quite compatible with swampland conjectures in their usual string theoretic form in a large class of modified cosmological scenarios. Building on that work, we now show that in modified cosmological scenarios where the early universe expansion was driven by single field inflation, one can have the dark energy equation of state to be significantly different from $-1$ even if we just take into account the original dS conjecture, let alone the refined form of that. We thereby show that one does not need to apply a step function approach towards inflation in order to have an observable distinction between constant and non-constant dark energy models in the context of the swampland conjectures.

We review a class of weakly non-local higher derivative theories of gravity as a step forward with Einstein’s general relativity. These theories are unitary (ghost-free) and UV-finite at quantum level in even and odd dimensions. In D = 4 the beta functions have been explicitly evaluated showing quantum scale-invariance (all the beta functions vanish). It is trivial to show finiteness in odd dimensions. Moreover these results can be easily extended to any even dimension and it is possible, that the higher-dimensional theory can be made finite too. Therefore, we have the possibility for finite and UV-complete quantum gravity in any dimension.