152 citations · 526 across the 15 of their papers we have counts for
15 papers
as an Effective Theory in de Sitter
Sebastian Cespedes, Zhehan Qin, Dong-Gang Wang
Effective field theories (EFTs) provide a powerful framework to parametrise unknown aspects of possible ultraviolet (UV) physics. For scalar fields in de Sitter space, however, new…
Cosmology, Decoherence and the Second Law
Sebastian Cespedes, Senarath de Alwis, Fernando Quevedo
We consider quantum decoherence and entropy increase in early universe cosmology. We first study decoherence in a discrete bipartite quantum system for which a single qubit gets en…
The Massive Flat Space Limit of Cosmological Correlators
Sebastian Cespedes, Sadra Jazayeri
Identifying useful flat-space limits for cosmological correlators, where they can be expressed in terms of observables in Minkowski space is nontrivial due to their scale-invariant…
Quantum Transitions, Detailed Balance, Black Holes and Nothingness
Sebastian Cespedes, Senarath de Alwis, Francesco Muia +1
We consider vacuum transitions by bubble nucleation among 4D vacua with different values and signs of the cosmological constant , including both up and down tunnelings. Followin…
The hand-made tail: Non-perturbative tails from multifield inflation
Ana Achucarro, Sebastian Cespedes, Anne-Christine Davis +1
It is becoming increasingly clear that large but rare fluctuations of the primordial curvature field, controlled by the tail of its probability distribution, could have dramatic ef…
Density Perturbations and Primordial Non-Gaussianities in a Closed Universe
Sebastian Cespedes, Senarath de Alwis, Francesco Muia +1
The spatial curvature of the universe is not yet known. Even though at present the Universe is very close to being essentially flat and most signatures of curvature appear to have…
Lorentzian Vacuum Transitions: Open or Closed Universes?
Sebastian Cespedes, Senarath P. de Alwis, Francesco Muia +1
We consider the generalisation of quantum tunneling transitions in the WKB approximation to the time-independent functional Schrödinger and Wheeler-DeWitt equations. Following a Lo…
On the time evolution of cosmological correlators
Sebastian Cespedes, Anne-Christine Davis, Scott Melville
Developing our understanding of how correlations evolve during inflation is crucial if we are to extract information about the early Universe from our late-time observables. To tha…
Constraints on holographic multi-field inflation and models based on the Hamilton-Jacobi formalism
Ana Achucarro, Sebastian Cespedes, Anne-Christine Davis +1
In holographic inflation, the cosmological dynamics is postulated to be dual to the renormalization group flow of a Euclidean conformal field theory with marginally relev…
Signatures of graviton masses on the CMB
Philippe Brax, Sebastian Cespedes, Anne-Christine Davis
The impact of the existence of gravitons with non-vanishing masses on the B modes of the Cosmic Microwave Background (CMB) is investigated. We also focus on putative modifications…
Disformal transformations on the CMB
Clare Burrage, Sebastian Cespedes, Anne-Christine Davis
In this work we study the role of disformal transformation on cosmological backgrounds and its relation to the speed of sound for tensor modes. A speed different from one for tenso…
Non-canonical inflation coupled to matter
Sebastian Cespedes, Anne-Christine Davis
We compute corrections to the inflationary potential due to conformally coupled non-relativistic matter. We find that under certain conditions of the matter coupling, inflation may…
Cosmic inflation in a landscape of heavy-fields
Sebastian Cespedes, Gonzalo A. Palma
Heavy isocurvature fields may have a strong influence on the low energy dynamics of curvature perturbations during inflation, as long as the inflationary trajectory becomes non-geo…
Heavy fields, reduced speeds of sound and decoupling during inflation
Ana Achucarro, Vicente Atal, Sebastian Cespedes +3
We discuss and clarify the validity of effective single field theories of inflation obtained by integrating out heavy degrees of freedom in the regime where adiabatic perturbations…
On the importance of heavy fields during inflation
Sebastian Cespedes, Vicente Atal, Gonzalo A. Palma
We study the dynamics of two-field models of inflation characterized by a hierarchy of masses between curvature and isocurvature modes. When the hierarchy is large, a low energy ef…