Labour Market Dynamics in RBC Models

This paper explores the ability of a large set of RBC type models to explain aggregate US data by examining how well the rst-order conditions (FOCs) from each model t the data. Typically, the residuals from the FOC for hours worked are large in magnitude (more volatile than total hours), very highly persistent, and stay away from zero for long periods of time. This pattern suggests that standard RBC models are unable to capture the dynamics in the joint behaviour of consumption, output and hours that exists in the US data. We show that models which generate dynamic terms in the FOC for hours worked are able to capture this feature of the data by exploring a RBC model augmented by learning by doing which has been shown to have such a dynamic FOC. The results are remarkable. The residuals from the hours FOC are much less volatile than total hours and display no persistence. Less conclusive results emerge from models with habit formation in preferences which also yield dynamic FOCs for the labour input. We conclude that an additional dynamic component in the FOCs is essential to better capture the dynamics in the data and future research using the RBC structure should explore models that deliver it.

An Expectations-Driven Interpretation of the “Great Recession”

The boom-years preceding the "Great Recession" were a time of rapid innovation in the financial industry. We explore the idea that both the boom and eventual bust emerged from overoptimistic expectations of efficiency-gains in the financial sector. We treat the bankruptcy costs facing intermediaries in a costly state verification problem as a stochastic process, and model the boom-bust in terms of an unfulfilled news-shock where the expected fall in costs are eventually not realized. In response to a change in expectations only, the model generates a boom-bust cycle in aggregate activity, asset prices and leverage, and a countercyclical credit spread

Fear of Sovereign Default, Banks, and Expectations-driven Business Cycles

What is the effect of the fear of future sovereign default on the economy of the defaulting country? The typical sovereign default model does not address this question. In this paper we wish to explore the possibility that changing expectations about future default themselves can lead to financial stress (as measured by credit spreads) and recessionary outcomes. We exploit the "news- shock" framework to consider an environment in which sovereign debt-holders receive imperfect signals about the portion of debt that a sovereign may default on in the future. We then investigate how domestic banks can play a role in transmitting the expectation of default into a realized recession through the interaction of the domestic banks' holdings of government debt and their risk- weighted capital requirements. Our results suggest that, consistent with the data, even in the absence of actual realized government default, an increase in pessimism regarding the prospect of future default results in a rise in yields on government debt and an increase in interest rates on private domestic loans, as well as a recession in the economy

Viscous cosmologies in scalar-tensor theories for Kasner type metrics

In a viscous Bianchi type I metric of the Kasner form, it is well known that it is not possible to describe an anisotropic physical model of the universe, which satisfies the second law of thermodynamics and the dominant energy condition (DEC) in Einstein's theory of gravity. We examine this problem in scalar-tensor theories of gravity. In this theory we show that it is possible to describe the growth of entropy, keeping the thermodynamics and the dominant energy condition.Comment: 6 pages, Latex, accepted in Phys. Rev.

WRKY6 restricts Piriformospora indica-stimulated and phosphate-induced root development in Arabidopsis

BACKGROUND: Arabidopsis root growth is stimulated by Piriformospora indica, phosphate limitation and inactivation of the WRKY6 transcription factor. Combinations of these factors induce unexpected alterations in root and shoot growth, root architecture and root gene expression profiles. RESULTS: The results demonstrate that P. indica promotes phosphate uptake and root development under Pi limitation in wrky6 mutant. This is associated with the stimulation of PHOSPHATE1 expression and ethylene production. Expression profiles from the roots of wrky6 seedlings identified genes involved in hormone metabolism, transport, meristem, cell and plastid proliferation, and growth regulation. 25 miRNAs were also up-regulated in these roots. We generated and discuss here a list of common genes which are regulated in growing roots and which are common to all three growth stimuli investigated in this study. CONCLUSION: Since root development of wrky6 plants exposed to P. indica under phosphate limitation is strongly promoted, we propose that common genes which respond to all three growth stimuli are central for the control of root growth and architecture. They can be tested for optimizing root growth in model and agricultural plants. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12870-015-0673-4) contains supplementary material, which is available to authorized users

Constraining Dark Energy and Cosmological Transition Redshift with Type Ia Supernovae

The property of dark energy and the physical reason for acceleration of the present universe are two of the most difficult problems in modern cosmology. The dark energy contributes about two-thirds of the critical density of the present universe from the observations of type-Ia supernova (SNe Ia) and anisotropy of cosmic microwave background (CMB).The SN Ia observations also suggest that the universe expanded from a deceleration to an acceleration phase at some redshift, implying the existence of a nearly uniform component of dark energy with negative pressure. We use the ``gold'' sample containing 157 SNe Ia and two recent well-measured additions, SNe Ia 1994ae and 1998aq to explore the properties of dark energy and the transition redshift. For a flat universe with the cosmological constant, we measure $\Omega_{M}=0.28_{-0.05}^{+0.04}$, which is consistent with Riess et al. The transition redshift is $z_{T}=0.60_{-0.08}^{+0.06}$. We also discuss several dark energy models that define the $w(z)$ of the parameterized equation of state of dark energy including one parameter and two parameters ($w(z)$ being the ratio of the pressure to energy density). Our calculations show that the accurately calculated transition redshift varies from $z_{T}=0.29_{-0.06}^{+0.07}$ to $z_{T}=0.60_{-0.08}^{+0.06}$ across these models. We also calculate the minimum redshift $z_{c}$ at which the current observations need the universe to accelerate.Comment: 16 pages, 5 figures, 1 tabl

The Genesis of Cosmological Tracker Fields

The role of the quintessence field as a probable candidate for the repulsive dark energy, the conditions for tracking and the requisites for tracker fields are examined. The concept of `integrated tracking' is introduced and a new criterion for the existence of tracker potentials is derived assuming monotonic increase in the scalar energy density parameter \Omega_\phi with the evolution of the universe as suggested by the astrophysical constraints. It provides a technique to investigate generic potentials of the tracker fields. The general properties of the tracker fields are discussed and their behaviour with respect to tracking parameter \epsilon is analyzed. It is shown that the tracker fields around the limiting value \epsilon \simeq \frac 23 give the best fit with the observational constraints.Comment: 8 pages, Latex file, 1 figure, comments adde