arXiv subjects

Danjie Wenren

Publications and source records attributed to Danjie Wenren.

3 recordsLinked to original sources

arXiv2017

Hyperbolic Black Holes and Open String Production

In this paper we investigate open string pair production effects near hyperbolic black holes in AdS$_5$. We study the classical dynamics of D3 probe branes in this background and their quantum tunneling rate across the horizon from the inside using a method similar to that of Kraus, Parikh and Wilczek. The hyperbolic black holes can decay through these tunneling events and their lifetime is estimated. The radiated branes move towards the boundary and do not bounce back. Their world-lines do not intersect directly and they do not hit the singularity either, providing a clean scenario for studying the non-adiabatic pair production effects of open strings stretched between them near horizon. We find that there is a well defined parameter regime where there can be significant pair production. This requires the radiated branes to be highly boosted. However, the radiation of such branes still has small back-reaction on the black hole background, though the open string pair production on them can potentially alter the background. We comment on the possible relation of our model and the AMPS paradox. Some issues and future directions are discussed in the end.

hep-th↗

arXiv2017

Heavy Fermion Production and Primordial N-Spectra

We compute the non-adiabatic production of heavy fermion during inflation due to its coupling with inflaton. The coupling, partly inspired by axion monodromy, comes from the modulation of the fermion mass by the inflaton field. Even though the fermion mass is always much higher than the Hubble scale and the density of the produced fermions is low, they can still have detectable signatures in the cosmic microwave background. Their contributions to the primordial $N$-spectra are then analyzed in detail and compared with those from the fermion's bosonic super-partner. At the classical level, where the produced particles are treated as classical sources, the effect on the $N$-spectra is proportional to the density of the produced particles and the fermion and boson cases have the same contribution. Quantum interference, however, leads to distinction between the two cases. Implications of this similarity and distinction are discussed before making general remarks about the limitations of our calculation and possible ways of overcoming them.

hep-th↗

arXiv2014

Tilt and Tensor-to-Scalar Ratio in Multifield Monodromy Inflation

We study the possible range of the tilt $n_s$ and the tensor-to-scalar ratio $r$ in multifield versions of a class of inflationary models from string theory. We show that $r$ is the same between the single field models and multifield models while $n_s$ is bounded above by the results of single field models. Below its maximum value, $n_s$ depends on the specific distributions of parameters in the model. The general trend is that the wider the distributions are, the smaller $n_s$ is. We show that $n_s$ does not have a rigorous lower bound. It is argued, however, that models predicting arbitrarily small $n_s$ only constitute a small portion of the possible ones and for the vast majority of models, $n_s$ is bounded below by predictions given by models with uniformly distributed parameters.

hep-th↗