1.9k citations · 16.3k across the 107 of their papers we have counts for
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Anisotropic non-Gaussianity from vector field perturbations
Mindaugas Karciauskas, Konstantinos Dimopoulos, David H. Lyth
We suppose that a vector field perturbation causes part of the primordial curvature perturbation. The non-Gaussianity parameter fNL is then, in general, statistically anisotropic.…
Statistical anisotropy of the curvature perturbation from vector field perturbations
Konstantinos Dimopoulos, Mindaugas Karciauskas, David H. Lyth +1
The δN formula for the primordial curvature perturbation ζis extended to include vector as well as scalar fields. Formulas for the tree-level contributions to the spectrum and bisp…
Non-gaussianity of inflationary field perturbations from the field equation
David Seery, Karim A. Malik, David H. Lyth
We calculate the tree-level bispectrum of the inflaton field perturbation directly from the field equations, and construct the corresponding f_NL parameter. Our results agree with…
The curvature perturbation in a box
David H. Lyth
The stochastic properties of cosmological perturbations are best defined through the Fourier expansion in a finite box. I discuss the reasons for that with reference the curvature…
Generating the Curvature Perturbation at the End of Inflation in String Theory
D. H. Lyth, A. Riotto
In brane inflationary scenarios, the cosmological perturbations are supposed to originate from the vacuum fluctuations of the inflaton field corresponding to the position of the br…
Classicality of the primordial perturbations
David H. Lyth, David Seery
We show that during inflation, a quantum fluctuation becomes classical at all orders if it becomes classical at first order. Implications are discussed.
Curvature perturbation from symmetry breaking the end of inflation
Laila Alabidi, David Lyth
We consider a two-field hybrid inflation model, in which the curvature perturbation is predominantly generated at the end of inflation. By finely tuning the coupling of the fields…
A numerical study of non-gaussianity in the curvaton scenario
Karim A. Malik, David H. Lyth
We study the curvaton scenario using gauge-invariant second order perturbation theory and solving the governing equations numerically. Focusing on large scales we calculate the non…
Inflation models after WMAP year three
Laila Alabidi, David H. Lyth
The survey of models in astro-ph/0510441 is updated.For the first time, a large fraction of the models is ruled out at more than .
Non-gaussianity and cosmic uncertainty in curvaton-type models
D. H. Lyth
In curvaton-type models, observable non-gaussianity of the curvature perturbation would come from a contribution of the form , where is gaussian. I analyse this situat…
Higher order contributions to the primordial non-gaussianity
Ignacio Zaballa, Yeinzon Rodriguez, David H. Lyth
In this paper we calculate additional contributions to that part of the non-Gaussianity of the curvature perturbation, which come from the three-point correlator of the field pertu…
Inflation models and observation
Laila Alabidi, David Lyth
We consider small-field models which invoke the usual framework for the effective field theory, and large-field models which go beyond that. Present and future possibilities for di…
Generating the curvature perturbation at the end of inflation
David H. Lyth
The dominant contribution to the primordial curvature perturbation may be generated at the end of inflation. Taking the end of inflation to be sudden, formulas are presented for th…
Forming sub-horizon black holes at the end of inflation
David. H Lyth, Karim A. Malik, Misao Sasaki +1
Previous authors have calculated the mass function of primordial black holes only on scales which are well outside the horizon at the end of inflation. Here we extend the calculati…
The bound on the primordial tensor perturbation
David H. Lyth
I recall the well-known sufficient conditions for the bound on the spectrum of the primordial tensor perturbation. Two recent papers claim a violation of this bound, withou…
A Bound Concerning Primordial Non-Gaussianity
David H. Lyth, Ignacio Zaballa
Seery and Lidsey have calculated the three-point correlator of the light scalar fields, a few Hubble times after horizon exit during inflation. Lyth and Rodriguez have calculated t…
Detecting a small perturbation through its non-Gaussianity
Lotfi Boubekeur, David. H. Lyth
A highly non-gaussian cosmological perturbation with a flat spectrum has unusual stochastic properties. We show that they depend on the size of the box within which the perturbatio…
The inflationary prediction for primordial non-gaussianity
David H. Lyth, Yeinzon Rodriguez
We extend the δN formalism so that it gives all of the stochastic properties of the primordial curvature perturbation ζif the initial field perturbations are gaussian. The calculat…
Non-gaussianity from the second-order cosmological perturbation
David H. Lyth, Yeinzon Rodriguez
Several conserved and/or gauge invariant quantities described as the second-order curvature perturbation have been given in the literature. We revisit various scenarios for the gen…
A general proof of the conservation of the curvature perturbation
David H. Lyth, Karim A. Malik, Misao Sasaki
Without invoking a perturbative expansion, we define the cosmological curvature perturbation, and consider its behaviour assuming that the universe is smooth over a sufficiently la…
The running-mass inflation model and WMAP
Laura Covi, David H. Lyth, Alessandro Melchiorri +1
We consider the observational constraints on the running-mass inflationary model, and in particular on the scale-dependence of the spectral index, from the new Cosmic Microwave Bac…
The CDM isocurvature perturbation in the curvaton scenario
David H Lyth, David Wands
We discuss the residual isocurvature perturbations, fully-correlated with the curvature perturbation, that are automatic in the curvaton scenario if curvaton decay is sufficiently…
Conserved cosmological perturbations
David H Lyth, David Wands
A conserved cosmological perturbation is associated with each quantity whose local evolution is determined entirely by the local expansion of the Universe. It may be defined as the…
The primordial density perturbation in the curvaton scenario
David H. Lyth, Carlo Ungarelli, David Wands
We analyse the primordial density perturbation when it is generated by a `curvaton' field different from the inflaton. In some cases this perturbation may have large isocurvature c…