Does Real Exchange Rate Volatility Affect Sectoral Trade Flows?

This paper investigates empirically the effect of real exchange rate volatility on sectoral bilateral trade flows between the US and her top thirteen trading countries. Our investigation also considers those effects on trade flows which may arise through changes in income volatility and the interaction between income and exchange rate volatilities. We provide evidence that exchange rate volatility mainly affects sectoral trade flows of developing but not that of developed countries. We also find that the effect of the interaction term on trade flows is opposite that of exchange rate volatility yet there is little impact arising from income volatility

Energy conditions bounds on f(T) gravity

In standard approach to cosmological modeling in the framework of general relativity, the energy conditions play an important role in the understanding of several properties of the Universe, including singularity theorems, the current accelerating expansion phase, and the possible existence of the so-called phantom fields. Recently, the $f(T)$ gravity has been invoked as an alternative approach for explaining the observed acceleration expansion of the Universe. If gravity is described by a $f(T)$ theory instead of general relativity, there are a number of issues that ought to be reexamined in the framework of $f(T)$ theories. In this work, to proceed further with the current investigation of the limits and potentialities of the $f(T)$ gravity theories, we derive and discuss the bounds imposed by the energy conditions on a general $f(T)$ functional form. The null and strong energy conditions in the framework of $f(T)$ gravity are derived from first principles, namely the purely geometric Raychaudhuri's equation along with the requirement that gravity is attractive. The weak and dominant energy conditions are then obtained in a direct approach via an effective energy-momentum tensor for $f(T)$ gravity. Although similar, the energy condition inequalities are different from those of general relativity (GR), but in the limit $f(T)=T$ the standard forms for the energy conditions in GR are recovered. As a concrete application of the derived energy conditions to locally homogeneous and isotropic $f(T)$ cosmology, we use the recent estimated value of the Hubble parameter to set bounds from the weak energy condition on the parameters of two specific families of $f(T)$ gravity theories.Comment: 8 pages.V2: Typos corrected, refs. added. V3:Version to appear in Phys. Rev. D (2012). New subsection, minor changes, references added, typos correcte

Abstract and document reproduction Final report, 1 Oct. 1969 - 30 Sep. 1970

Document and abstract reproduction and dissemination facility operations revie

A geometric proof of the Karpelevich-Mostow's theorem

In this paper we give a geometric proof of the Karpelevich's theorem that asserts that a semisimple Lie subgroup of isometries, of a symmetric space of non compact type, has a totally geodesic orbit. In fact, this is equivalent to a well-known result of Mostow about existence of compatible Cartan decompositions

Mok's characteristic varieties and the normal holonomy group

In this paper we complete the study of the normal holonomy groups of complex submanifolds (non nec. complete) of Cn or CPn. We show that irreducible but non transitive normal holonomies are exactly the Hermitian s-representations of [CD09, Table 1] (see Corollary 1.1). For each one of them we construct a non necessarily complete complex submanifold whose normal holonomy is the prescribed s-representation. We also show that if the submanifold has irreducible non transitive normal holonomy then it is an open subset of the smooth part of one of the characteristic varieties studied by N. Mok in his work about rigidity of locally symmetric spaces. Finally, we prove that if the action of the normal holonomy group of a projective submanifold is reducible then the submanifold is an open subset of the smooth part of a so called join, i.e. the union of the lines joining two projective submanifolds