On the cycle class map for zero-cycles over local fields

We study the Chow group of zero-cycles of smooth projective varieties over local and strictly local fields. We prove in particular the injectivity of the cycle class map to integral l-adic cohomology for a large class of surfaces with positive geometric genus, over local fields of residue characteristic different from l. The same statement holds for semistable K3 surfaces defined over C((t)), but does not hold in general for surfaces over strictly local fields.Comment: 37 pages (with an appendix by Spencer Bloch); bibliography updated, final versio

Definitions and Measures of ICT Impact on Growth: What is Really at Stake?

Many innovations have been introduced in national accounts in order to better gauge the information and communication technologies (ICT) diffusion impact: new ICT definitions; recognition of business and government software expenditures as fixed investment; hedonic price index. Nevertheless, there still does not exist any clear consensus about the magnitude of the ICT impact on growth. Our aim is to propose some explanations of this relative failure and also show that the debate should not be exclusively centered on quantitative methods. To this end, we take a close look at the two main questions concerning the debate surrounding the measure of the ICT impact: 1) Are there any substantial total factor productivity (TFP) gains generated by ICT diffusion or is it only a classic story of capital deepening increase ? 2) If there are indeed TFP gains, are they limited to ICT producers, as Robert J.Gordon claims, or is there any diffusion to ICT users ? The answer to the first question is really important only if it determines the length and the extent of an eventual growth cycle impulsed by ICT. The possibility that productivity gains mainly due to capital deepening generate strong and durable growth has been theoritically demonstrated by Greenwood and Jovanovic (1998), thanks to a vintage capital model. We precise the conditions under which this result can be obtained and discuss their empirical relevance. According to this approach, the true debate concerns the durability of the present technological shock, instead of its capacity to generate an autonomous technical progress. The answer to the second question is crucial because it could guide industrial policy choices. If TFP gains are limited to ICT producers, should a country always be an ICT producer, or will it anyway grow at a strong pace thanks to the fall of ICT prices ? The relevance of this economic debate is unfortunately poised by the shortcomings of available statistical tools. On one hand, the distinction between ICT users and producers is purely discretionary. On the other hand, TFP measure is completely distorted by the method used to evaluate the value of capital (cost-based prices against adjusted-quality prices). That is why we argue that the international diffusion of growth gains due to ICT essentially depends on the capacity of ICT producers' countries to stay in a rent keeping situation. The text is divided into two parts. The first one first makes a quick assessment of the adaptation of american national accounts to the " new economy ", and then underlines the limits of these changes. The second one shows that the economic debate on the importance of TFP gains acceleration and where they occur, although more complex because of these limits, can quite ignore them thanks to the implications of some endogeneous growth and international trade models.ICT; multifactor productivity; national accounts; hedonic prices

A restriction isomorphism for cycles of relative dimension zero

We study the restriction map to the closed fiber of a regular projective scheme over an excellent henselian discrete valuation ring, for a cohomological version of the Chow group of relative zero-cycles. Our main result extends the work of Saito--Sato to general perfect residue fields.Comment: 34 pages; final versio

Index of varieties over Henselian fields and Euler characteristic of coherent sheaves

Let X be a smooth proper variety over the quotient field of a Henselian discrete valuation ring with algebraically closed residue field of characteristic p. We show that for any coherent sheaf E on X, the index of X divides the Euler-Poincar\'e characteristic \chi(X,E) if p=0 or p>dim(X)+1. If 0<p\leq dim(X)+1, the prime-to-p part of the index of X divides \chi(X,E). Combining this with the Hattori-Stong theorem yields an analogous result concerning the divisibility of the cobordism class of X by the index of X. As a corollary, rationally connected varieties over the maximal unramified extension of a p-adic field possess a zero-cycle of p-power degree (a zero-cycle of degree 1 if p>dim(X)+1). When p=0, such statements also have implications for the possible multiplicities of singular fibers in degenerations of complex projective varieties.Comment: 20 pages; final versio

An innovative blazar classification based on radio jet kinematics

Blazars are usually classified following their synchrotron peak frequency ($\nu F(\nu)$ scale) as high, intermediate, low frequency peaked BL Lacs (HBLs, IBLs, LBLs), and flat spectrum radio quasars (FSRQs), or, according to their radio morphology at large scale, FR~I or FR~II. However, the diversity of blazars is such that these classes seem insufficient to chart the specific properties of each source. We propose to classify a wide sample of blazars following the kinematic features of their radio jets seen in very long baseline interferometry (VLBI). For this purpose we use public data from the MOJAVE collaboration in which we select a sample of blazars with known redshift and sufficient monitoring to constrain apparent velocities. We selected 161 blazars from a sample of 200 sources. We identify three distinct classes of VLBI jets depending on radio knot kinematics: class I with quasi-stationary knots, class II with knots in relativistic motion from the radio core, and class I/II, intermediate, showing quasi-stationary knots at the jet base and relativistic motions downstream. A notable result is the good overlap of this kinematic classification with the usual spectral classification; class I corresponds to HBLs, class II to FSRQs, and class I/II to IBLs/LBLs. We deepen this study by characterizing the physical parameters of jets from VLBI radio data. Hence we focus on the singular case of the class I/II by the study of the blazar BL Lac itself. Finally we show how the interpretation that radio knots are recollimation shocks is fully appropriate to describe the characteristics of these three classes.Comment: 12 pages, 13 figures, accepted by A&

International financial adjustment

The paper proposes a unified framework to study the dynamics of net foreign assets and exchange rate movements. We show that deteriorations in a country's net exports or net foreign asset position have to be matched either by future net export growth (trade adjustment channel) or by future increases in the returns of the net foreign asset portfolio (hitherto unexplored financial adjustment channel). Using a newly constructed data set on US gross foreign positions, we find that stabilizing valuation effects contribute as much as 31% of the external adjustment. Our theory also has asset pricing implications. Deviations from trend of the ratio of net exports to net foreign assets predict net foreign asset portfolio returns one quarter to two years ahead and net exports at longer horizons. The exchange rate affects the trade balance and the valuation of net foreign assets. It is forecastable in and out of sample at one quarter and beyond. A one standard deviation decrease of the ratio of net exports to net foreign assets predicts an annualized 4% depreciation of the exchange rate over the next quarter.

From World Banker to World Venture Capitalist: US External Adjustment and the Exorbitant Privilege

Does the center country of the International Monetary System enjoy an "exorbitant privilege" that significantly weakens its external constraint as has been asserted in some European quarters? Using a newly constructed dataset, we perform a detailed analysis of the historical evolution of US external assets and liabilities at market value since 1952. We find strong evidence of a sizeable excess return of gross assets over gross liabilities. Interestingly, this excess return increased after the collapse of the BrettonWoods fixed exchange rate system. It is mainly due to a "return discount": within each class of assets, the total return (yields and capital gains) that the US has to pay to foreigners is smaller than the total return the US gets on its foreign assets. We also find evidence of a "composition effect": the US tends to borrow short and lend long. As financial globalization accelerated its pace, the US transformed itself from a World Banker into a World Venture Capitalist, investing greater amounts in high yield assets such as equity and FDI. We use these findings to cast some light on the sustainability of the current global imbalances.

International Financial Adjustment

The paper proposes a unified framework to study the dynamics of net foreign assets and exchange rate movements. We show that deteriorations in a country's net exports or net foreign asset position have to be matched either by future net export growth (trade adjustment channel) or by future increases in the returns of the net foreign asset portfolio (hitherto unexplored financial adjustment channel). Using a newly constructed data set on US gross foreign positions, we find that stabilizing valuation effects contribute as much as 31% of the external adjustment. Our theory also has asset pricing implications. Deviations from trend of the ratio of net exports to net foreign assets predict net foreign asset portfolio returns one quarter to two years ahead and net exports at longer horizons. The exchange rate affects the trade balance and the valuation of net foreign assets. It is forecastable in and out of sample at one quarter and beyond. A one standard deviation decrease of the ratio of net exports to net foreign assets predicts an annualized 4% depreciation of the exchange rate over the next quarter.Meese-Rogoff, external adjustment, net foreign assets, valuation effects, exchange rates