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Generating Ekpyrotic Curvature Perturbations Before the Big Bang
We analyze a general mechanism for producing a nearly scale-invariant spectrum of cosmological curvature perturbations during a contracting phase preceding a big bang, which can be entirely described
Higher-derivative chiral superfield actions coupled to N = 1 supergravity
We construct N=1 supergravity extensions of scalar field theories with higher-derivative kinetic terms. Special attention is paid to the auxiliary fields, whose elimination leads not only to
Lorentzian quantum cosmology
We argue that the Lorentzian path integral is a better starting point for quantum cosmology than its Euclidean counterpart. In particular, we revisit the minisuperspace calculation of the Feynman
No Smooth Beginning for Spacetime.
TLDR
A new mathematical tool is introduced-Picard-Lefschetz theory-for defining the semiclassical path integral for gravity, and it is proved that primordial tensor (gravitational wave) fluctuations are unsuppressed.
D ec 2 01 0 Supersymmetric P ( X , φ ) and the Ghost Condensate
We show how to construct supersymmetric actions for higher-derivative scalar field theories of the form P (X,φ), where X ≡ −(∂φ)2/2m4, within the context of d = 4, N = 1 supersymmetry. This
No rescue for the no boundary proposal: Pointers to the future of quantum cosmology
In recent work, we introduced Picard-Lefschetz theory as a tool for defining the Lorentzian path integral for quantum gravity in a systematic semiclassical expansion. This formulation avoids several
No-Boundary Proposal as a Path Integral with Robin Boundary Conditions.
TLDR
It is shown that, in the context of gravity with a positive cosmological constant, path integrals with a specific family of Robin boundary conditions overcome this problem and are manifestly convergent.
Ekpyrotic Non-Gaussianity -- A Review
Ekpyrotic models and their cyclic extensions solve the standard cosmological flatness, horizon and homogeneity puzzles by postulating a slowly contracting phase of the universe prior to the big bang.
On the Quantum-To-Classical Transition for Ekpyrotic Perturbations
We examine the processes of quantum squeezing and decoherence of density perturbations produced during a slowly contracting ekpyrotic phase in which entropic perturbations are converted to curvature
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