On Gauge Invariant Cosmological Perturbations in UV-modified Horava Gravity: A Brief Introduction

We revisit gauge invariant cosmological perturbations in UV-modified, z = 3 Horava gravity with one scalar matter field, which has been proposed as a renormalizable gravity theory without the ghost problem in four dimensions. We confirm that there is no extra graviton modes and general relativity is recovered in IR, which achieves the consistency of the model. From the UV-modification terms which break the detailed balance condition in UV, we obtain scale-invariant power spectrums for non-inflationary backgrounds, like the power-law expansions, without knowing the details of early expansion history of Universe. This could provide a new framework for the Big Bang cosmology.Comment: 5 pages, Prepared for Proceeding of International Joint Conference of ICGAC-XIII and IK15 (July 3-7, 2017, Seoul, Republic of Korea

A Simple Inducement Scheme to Overcome Adoption Externalities

Potential customers of network commodities face coordination problems due to adoption externalities that give rise to multiple, Pareto-ranked equilibria. We investigate the extent to which the coordination problem can be resolved by inducement schemes when agents’ preferences are private information. Specifically, we show that all symmetric “cut-off strategy” profiles (agents adopt if and only if their type is below a threshold) constitute the set of profiles that can be implemented as a unique equilibrium under an inducement scheme. We derive the ex ante cost of implementing each such profile. Furthermore, we fully characterize the set of inducement schemes that I) implement each such profile and ii) have the following simple form: each scheme specifies a fixed fee that every adopter pays, and a fixed gross subsidy/prize to be randomly allocated to (or evenly split among) the adopters. We discuss the implications of these findings on the design of optimal schemes for different network organizers, namely, private entrepreneurs and public entities.adoption externality, coordination, inducement scheme

Dynamic Formation of Network with Adoption Externalities

We analyze an entry game with multiple periods, in each period of which privately informed agents who have not joined yet decide whether to subscribe to a network, and subscribers derive benefits in future periods depending on the network size. We study the case that the agents are sufficiently patient and show that there exists a unique symmetric \e\ if the number of existing subscribers is common knowledge in each period, thereby resolving the coordination problem which is prevalent in markets with network externalities. Asymmetric \ea\ may exist, but we show that they, if exist, converge to the unique symmetric \e\ as the number of agents increases without boundcoordination failure, unique symmetric equilibrium