Estimating the size of the European stimulus packages for 2009: An Update. Bruegel Policy Contribution 2009/02, February 20, 2009

[Introduction]. In December 2008, the European Council agreed on an EU‐wide economic stimulus of “around € 200 billion”. However, this agreement is not very specific in two important respects. First, it is unclear which country is to contribute how much to the roughly €170 billion part of the fiscal stimulus that is to be effected by member states, with the remaining €30 billion to be contributed at the EU level. Second, there is no clear timeline detailing which part of the stimulus is to be delivered by when. However, both the geography and the timing of the European stimulus are important dimensions when trying to assess the likely economic impact of the pact and the progress towards it implementation. In order to contribute to the debate on the geography and timing of the stimulus, we presented a first estimate of the size of fiscal stimuli that had recently been proposed by member states (and had, in some cases, already been adopted) just in time for the European Council. The present update of that earlier paper simply presents the latest breakdown of the fiscal stimuli in member states using thesame methodology as before. In addition, an heroic attempt is made to compare the total European package for 2009 to the stimulus packages set to be implemented in theUS and China. To keep the complexity of the EU side of the exercise manageable, we only take into account the 13 largest economies in the EU that make up more than 90 percent of the EU’s GDP, plus the planned boost at the Community level. Despite this simplification, the task of estimating the size of the different programmes remains challenging, not least because of the great variety of different instruments used and the rapid evolution of national debates

Detecting New Physics in Rare Top Decays at the LHC

In the companion paper it was shown that there are six observables in $gg\to t \bar t \to (b \bar b c) (\bar b \ell \bar \nu)$ that can be used to reveal the presence of new physics (NP) in $t \to b \bar b c$. In the present paper we examine the prospects for detecting and identifying such NP at the LHC, in both the short term and long term. To this end, we develop an algorithm for extracting the NP parameters from measurements of the observables. In the short term, depending on what measurements have been made, there are several different ways of detecting the presence of NP. It may even be possible to approximately determine the values of certain NP parameters. In the long term, it is expected that all six observables will be measured. The values of the NP parameters can then be determined reasonably precisely from a fit to these measurements, which will provide good information about the type of NP present in $t \to b \bar b c$.Comment: Published versio

The 2d-directed spanning forest converges to the Brownian web

The two-dimensional directed spanning forest (DSF) introduced by Baccelli and Bordenave is a planar directed forest whose vertex set is given by a homogeneous Poisson point process $\mathcal{N}$ on $\mathbb{R}^2$. If the DSF has direction $-e_y$, the ancestor $h(u)$ of a vertex $u \in \mathcal{N}$ is the nearest Poisson point (in the $L_2$ distance) having strictly larger $y$-coordinate. This construction induces complex geometrical dependencies. In this paper we show that the collection of DSF paths, properly scaled, converges in distribution to the Brownian web (BW). This verifies a conjecture made by Baccelli and Bordenave in 2007

Unemployment Insurance in Unionized Labor Markets: Neither Ghent nor Centralized

This paper analyzes unemployment insurance (UI) schemes in the presence of mobile workers and trade unions at industry or regional level that are capable of internalizing the effect of wage demands on UI contribution rates. We compare two types of existing UI systems. When UI is organized at trade union level (decentralized Ghent UI), trade unions strategically lower the benefit levels of their UI schemes to deter welfare recipients from other unions from entering their UI scheme, leading to a race to the bottom in UI provision. With centralized provision of UI, by contrast, trade unions do not fully account for the cost of higher wages as mobility allows them to partially shift the burden of unemployment to other UIs. A system of coordinated UI, combining a centrally set benefit level with decentralized funding as in Ghent UI systems, can circumvent both the strategic benefit setting and the fiscal externality problems, thus reconciling the equity and efficiency aims in the design of unemployment insurance

Search for New Physics in Rare Top Decays: ttˉt \bar t Spin Correlations and Other Observables

In this paper we study new-physics contributions to the top-quark decay $t \to b \bar b c$. We search for ways of detecting such new physics via measurements at the LHC. As top quarks are mainly produced at the LHC in $t \bar t$ production via gluon fusion, we analyze the process $gg \to t \bar t \to (b \bar b c) (\bar b \ell \bar \nu)$. We find six observables that can be used to reveal the presence of new physics in $t \to b \bar b c$. Three are invariant mass-squared distributions involving two of the final-state particles in the top decay, and three are angular correlations between the final-state quarks coming from the $t$ decay and the $\ell^-$ coming from the $\bar t$ decay. The angular correlations are related to the $t \bar t$ spin correlation.Comment: Published versio

Measuring CP-Violating Observables in Rare Top Decays at the LHC

In this paper we consider CP-violating new-physics contributions to the decay $t \to b \bar b c$. We examine the prospects for detecting such new physics at the LHC, which requires studying the process $gg \to t (\to b \bar b c) \bar t (\to \bar b \ell \bar \nu)$. We find two observables that can be used to reveal the presence of CP-violating new physics in $t \to b \bar b c$. They are (i) the partial-rate asymmetry and (ii) the triple-product correlations involving the momenta of various particles associated with the interaction. A Monte Carlo analysis is performed to determine how well these observables can be used to detect the presence of new physics, and to measure its parameters. We find that there is little difficulty in extracting the value of the relevant new-physics parameter from the partial-rate asymmetry. For the triple-product correlations, we test multiple strategies that can be used for the extraction of the corresponding combination of new-physics parameters.Comment: Published versio

EU stimulus packages. Estimating the size of the European stimulus packages for 2009: an update

David Saha and Jakob von Weizsäcker present the latest breakdown of the fiscal stimuli in the 13 largest EU economies and compare the total European package for 2009 to the US stimulus package. The authors estimate the size of the European stimulus packages to increase to 0.99% of GDP following increases in the stimulus packages in the Netherlands, the UK and Germany . The US stimulus package is estimated at about 1.7 percent of GDP, substantially above the EU average but only marginally above the largest national stimulus package in the EU

On certain classes of algebras in which centralizers are ideals

This paper is primarily concerned with studying finite-dimensional anti-commutative nonassociative algebras in which every centralizer is an ideal. These are shown to be anti-associative and are classified over a general field $F$; in particular, they are nilpotent of class at most $3$ and metabelian. These results are then applied to show that a Leibniz algebra over a field of charactersitic zero in which all centralizers are ideals is solvable

Human Immunodeficiency Virus Type 1 (HIV-1) Infection of Herpesvirus Saimiri-Immortalized Human CD4-Positive T Lymphoblastoid Cells: Evidence of Enhanced HIV-1 Replication and Cytopathic Effects Caused by Endogenous Interferon-γ

AbstractHerpesvirus saimiri (HVS) is a nonhuman primate gamma herpesvirus which can immortalize human T lymphocytes similar to Epstein–Barr virus immortalization of B cells. The HVS-immortalized T cell lines can be cloned and they remain functional, including susceptibility of CD4 expressing T cells to infection with human immunodeficiency virus type 1 (HIV-1). In this report, we have used five such HVS-transformed CD4-positive T cell clones to reevaluate the role of endogenous interferon gamma (IFNγ) in HIV-1 replication in T cells. All five clones had similar phenotypes; and four clones constitutively produced IFNγ and one clone did not. All five clones could be efficiently infected with HIV-1. HIV-1 infection of the IFNγ-positive cells also upregulated IFNγ mRNA production and IFNγ secretion but not production of IL-2 or IL-4. In contrast, infection of IFNγ-negative cells did not induce IFNγ, IL-2, or IL-4. Exposure to anti-IFNγ antibodies after HIV-1 infection significantly reduced virus production and inhibited virus-induced death of IFNγ-positive cells but had no effect on IFNγ-negative cells. We conclude that in CD4-positive T lymphocytes immortalized by HVS endogenous IFNγ does not inhibit HIV-1 but enhances HIV-1 replication and cytolysis. The potential augmenting effects of IFNγ on HIV-1 replication in CD4-positive T cells recommend caution in a therapeutic use of this cytokine in AIDS