4,290 research outputs found
Massless Particles in Arbitrary Dimensions
Various properties of two kinds of massless representations of the
n-conformal (or (n+1)-De Sitter) group are
investigated for . It is found that, for space-time dimensions ,
the situation is quite similar to the one of the n=4 case for -massless
representations of the n-De Sitter group . These
representations are the restrictions of the singletons of . The
main difference is that they are not contained in the tensor product of two
UIRs with the same sign of energy when n>4, whereas it is the case for another
kind of massless representation. Finally some examples of Gupta-Bleuler
triplets are given for arbitrary spin and .Comment: 33 pages, LaTeX2e. To be published in Reviews in Math. Phy
An extensible web interface for databases and its application to storing biochemical data
This paper presents a generic web-based database interface implemented in
Prolog. We discuss the advantages of the implementation platform and
demonstrate the system's applicability in providing access to integrated
biochemical data. Our system exploits two libraries of SWI-Prolog to create a
schema-transparent interface within a relational setting. As is expected in
declarative programming, the interface was written with minimal programming
effort due to the high level of the language and its suitability to the task.
We highlight two of Prolog's features that are well suited to the task at hand:
term representation of structured documents and relational nature of Prolog
which facilitates transparent integration of relational databases. Although we
developed the system for accessing in-house biochemical and genomic data the
interface is generic and provides a number of extensible features. We describe
some of these features with references to our research databases. Finally we
outline an in-house library that facilitates interaction between Prolog and the
R statistical package. We describe how it has been employed in the present
context to store output from statistical analysis on to the database.Comment: Online proceedings of the Joint Workshop on Implementation of
Constraint Logic Programming Systems and Logic-based Methods in Programming
Environments (CICLOPS-WLPE 2010), Edinburgh, Scotland, U.K., July 15, 201
Masslessness in -dimensions
We determine the representations of the ``conformal'' group , the restriction of which on the ``Poincar\'e'' subgroup are unitary irreducible. We study their restrictions to the ``De
Sitter'' subgroups and (they remain
irreducible or decompose into a sum of two) and the contraction of the latter
to ``Poincar\'e''. Then we discuss the notion of masslessness in dimensions
and compare the situation for general with the well-known case of
4-dimensional space-time, showing the specificity of the latter.Comment: 34 pages, LaTeX2e, 1 figure. To be published in Reviews in Math. Phy
Fiscal Policy, Rent Seeking and Growth under Electoral Uncertainty Theory and Evidence from the OECD
We construct a general equilibrium model of economic growth and optimally chosen fiscal policy, in which individuals compete with each other for a share of government spending and two political parties can alternate in power according to an exogenous reelection probability. The main prediction is that uncertainty about remaining in power results in increased fiscal spending, which in turn distorts incentives by pushing individuals away from productive work to rent-seeking activities; then distorted incentives hurt growth. This receives empirical support in a dataset of 25 OECD countries over the period 1982-1996. In particular, electoral uncertainty leads to larger government consumption shares in GDP, which in turn exert an adverse effect on the ICRG index measuring incentives and this is bad for growth. Actually, estimation by IV methods and confidence intervals that are robust to (potentially) weak instruments, reveal that OLS under-estimates the effects of government spending on rent extraction activities and of such activities on economic growth.Fiscal policy; rent seeking; economic growth; elections.
Fear of Model Misspecification and the Robustness Premium
Robust decision making implies welfare costs or robustness premia when the approximating model is the true data generating process. To examine the importance of these premia at the aggregate level we employ a simple two-sector dynamic general equilibrium model with human capital and introduce an additional form of precautionary behavior. The latter arises from the robust decision maker’s ability to reduce the effects of model misspecification through allocating time and existing human capital to this end. We find that the extent of the robustness premia critically depends on the productivity of time relative to that of human capital. When the relative efficiency of time is low, despite transitory welfare costs, there are gains from following robust policies in the long-run. In contrast, high relative productivity of time implies misallocation costs that remain even in the long-run. Finally, depending on the technology used to reduce model uncertainty, we find that while increasing the fear of model misspecification leads to a net increase in precautionary behavior, investment and output can fall.robustness premium, model misspecification, precautionary behavior
The Role of Government in Anti-Social Redistributive Activities
It is known that anti-social redistributive activities (rent seeking, tax evasion, corruption, violation of property rights, delay of socially beneficial reforms, etc) hurt the macroeconomy. But it is less known what is the role of government size as a determinant of such activities. We use data from 64 counties (both developed and developing) in 5-year periods over 1980-2000. As a measure of anti-social activities, we use the ICRG index; as a measure of government size, we use the government share in GDP; and as a measure of government efficiency, we construct an index by following the methodology of Afonso, Schuknecht and Tanzi (2003). Our regressions show that what really matters to social incentives is the relation between size and efficiency. Specifically, while a larger size of government is bad for incentives when one ignores efficiency, the results change drastically when government efficiency is also taken into account. Only when our measure of size exceeds our measure of efficiency, larger public sectors are bad for incentives. By contrast, when efficiency exceeds size, larger public sectors are not bad; actually, in the case where efficiency is measured by government performance in the policy areas of administration, stabilization and infrastructure, larger public sectors significantly improve incentives.government and behaviour of agents, collective decision-making
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