21,770 research outputs found
Quark masses in QCD: a progress report
Recent progress on QCD sum rule determinations of the light and heavy quark
masses is reported. In the light quark sector a major breakthrough has been
made recently in connection with the historical systematic uncertainties due to
a lack of experimental information on the pseudoscalar resonance spectral
functions. It is now possible to suppress this contribution to the 1% level by
using suitable integration kernels in Finite Energy QCD sum rules. This allows
to determine the up-, down-, and strange-quark masses with an unprecedented
precision of some 8-10%. Further reduction of this uncertainty will be possible
with improved accuracy in the strong coupling, now the main source of error. In
the heavy quark sector, the availability of experimental data in the vector
channel, and the use of suitable multipurpose integration kernels allows to
increase the accuracy of the charm- and bottom-quarks masses to the 1% level.Comment: Invited review paper to be published in Modern Physics Letters
Corrections to the Gell-Mann-Oakes-Renner relation and chiral couplings and
Next to leading order corrections to the
Gell-Mann-Oakes-Renner relation (GMOR) are obtained using weighted QCD Finite
Energy Sum Rules (FESR) involving the pseudoscalar current correlator. Two
types of integration kernels in the FESR are used to suppress the contribution
of the kaon radial excitations to the hadronic spectral function, one with
local and the other with global constraints. The result for the pseudoscalar
current correlator at zero momentum is , leading to the chiral corrections to GMOR: . The resulting uncertainties are mostly due to variations in the upper
limit of integration in the FESR, within the stability regions, and to a much
lesser extent due to the uncertainties in the strong coupling and the strange
quark mass. Higher order quark mass corrections, vacuum condensates, and the
hadronic resonance sector play a negligible role in this determination. These
results confirm an independent determination from chiral perturbation theory
giving also very large corrections, i.e. roughly an order of magnitude larger
than the corresponding corrections in chiral . Combining
these results with our previous determination of the corrections to GMOR in
chiral , , we are able to determine two low
energy constants of chiral perturbation theory, i.e. , and , both at the
scale of the -meson mass.Comment: Revised version with minor correction
Collective Action Frames and Policy Windows: The Case of the Project to Export Liquefied Natural Gas from Bolivia to California
How and why can a political mobilisation prevent what appears to be an economically rational and beneficial government investment? The present paper explores the ways in which both public policy and contentious politics theories can be potentially bridged to answer this question. It suggests ways in which concepts used by public policy theorists such as 'policy windows' (Kingdon, 1984) or 'advocacy coalitions' (Sabatier, 1999) may be useful to understand the emergence of political opportunities or the construction of collective action frames. The case study to be used is the project to export liquefied gas from Bolivia to California, which was promoted by the administration of Gonzalo Sánchez de Lozada in 2002 and was cancelled after civil society groups not only mobilise to resist it, but to demand the resignation of the president.
Agenda-setting and The Political Ecology of Large Infrastructure Projects in Latin America
This paper analyses the complex interplay between the environmental acceptability of large infrastructure projects and other normative values that may influence policy decisions, such as 'social justice' and 'economic growth'. It explores how historical changes in policy ideas may determine if a project survives on the policy agenda, if it is moved up to the decision-agenda; and whether and how it is finally implemented. Two case studies are presented with more detail: the project for a new international airport in Mexico City (1964-2000) and the Misicuni Multipurpose Project, aimed at solving the problems of water scarcity in Cochabamba, Bolivia (1952-2000).
Social Movements, Public Policy, and Democratic Consolidation in Latin America
This work studies how different social mobilisation processes have influenced policy processes in Latin America (2000-2003) and vice versa. Studying these interrelations includes three issues of empirical and theoretical importance. First, it explores under what conditions an investment project or policy initiative that is strongly supported by a democratically elected government on the basis of economic and technical arguments may trigger the emergence of a social movement; and under what conditions a social movement may successfully preclude the implementation of such project or policy initiative. Second, this work explores if these social movements have actually compensated for the absence of channels of participation and representation that work to influence the institutional policy process. Third and final, it studies if the influence and impact of these social movements have contributed to improve the design and implementation of public policies in the medium term and to promote the democratic consolidation in the region. Although the work is based on evidence from many countries in the region, there are mainly two case studies presented with more detail: the 'Water War' in Cochabamba, Bolivia (2001-2002) and the conflict triggered by the project to build a new airport in Mexico City (2001-2002). The 'Gas War' of Bolivia (2003) is also explored with less detail.
Discourses and Conditions of Possibility in Latin American Social Movements: The Cases of the Bolivian 'Water War' and the Movement of Opposition against the New Airport in Mexico City
This work presents a comparative analysis of two Latin American social movements. The first case is the movement of opposition against the privatisation of water and sanitation services (WSS) in Cochabamba, Bolivia and the second case is the movement of opposition against the project for a new international airport in Mexico City. Both case studies are used to illustrate how the study of collective discourses or collective action frames (CAFs) and the study of collective identities from a new social movement (NSM) perspective can be linked to improve our understanding of contemporary social movements. For these purposes, the work proposes the concept of conditions of possibility, defined as the contextual and organisational conditions that allow the resonance between constructed discourses and collective identities during the visible and the non-visible stages of a social movement.
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