13,196 research outputs found
Revisiting the strengths and limitations of regulatory contracts in infrastructure industries
This paper evaluates regulation by contract in public-private partnerships (PPPs) in infrastructure services. Although the benefits of competition for the market and of regulatory contracts are widely acknowledged, the literature indentifies several failures in their design. These ‘flaws’ are present in both developed and developing countries and arise in all types of contracts. This study analyses both short and long term contracts, focusing on purely contractual PPPs and institutionalized PPPs (mixed companies). The evidence suggests that for all kinds of contracts, the major problems tend to arise in the preparation of public tender documents: the ‘best’ bidder is not often the winner. The likely results include redistribution in favor of the private partner, weak incentives for high performance, and renegotiation of contracts. Moreover, risks are not allocated correctly nor is effective monitoring ensured. This review of contract procedures and design allows us to draw several implications for policy-makers and to present suggestions and recommendations for improving regulatory contracts.regulation by contract; bidding documents; contract design; risk; monitoring
Quantitative studies of water and sanitation utilities: a literature survey
This paper performs a literature update of quantitative studies of water and sanitation services (WSS). There are 190 studies which use cost or production functions to evaluate the performance of WSS utilities. The studies examine (1) the scale, scope or density economies of utilities in a particular country or region, (2) the influence of ownership on efficiency, (3) the existence and power of incentives associated with different governance systems (including external regulation), and (4) performance assessment (benchmarking). In addition, this paper presents some patterns regarding quantitative methods adopted over time and major trends in results.benchmarking; water and sanitation utilities; literature survey
Shadows and strong gravitational lensing: a brief review
For ultra compact objects (UCOs), Light Rings (LRs) and Fundamental Photon
Orbits (FPOs) play a pivotal role in the theoretical analysis of strong
gravitational lensing effects, and of BH shadows in particular. In this short
review, specific models are considered to illustrate how FPOs can be useful in
order to understand some non-trivial gravitational lensing effects. This paper
aims at briefly overviewing the theoretical foundations of these effects,
touching also some of the related phenomenology, both in General Relativity
(GR) and alternative theories of gravity, hopefully providing some intuition
and new insights for the underlying physics, which might be critical when
testing the Kerr black hole hypothesis.Comment: 32 pages, 9 figures; Review paper in the General Relativity and
Gravitation (GRG) Topical Collection "Testing the Kerr spacetime with
gravitational-wave and electromagnetic observations" (Guest Editor: Emanuele
Berti); v2: Typo corrected and two references adde
Deflationary cosmology: constraints from angular size and ages of globular clusters
Observational constraints to a large class of decaying vacuum cosmologies are
derived using the angular size data of compact radio sources and the latest age
estimates of globular clusters. For this class of deflationary
models, the present value of the vacuum energy density is quantified by a
positive parameter smaller than unity. In the case of milliarcsecond
compact radio-sources, we find that the allowed intervals for and the
matter density parameter are heavily dependent on the value of the
mean projected linear size . For pc, the best
fit occurs for , , and , , respectively. This analysis shows that if
one minimizes for the free parameters , and
, the best fit for these angular size data corresponds to a decaying
with and
pc. Constraints from age estimates of globular clusters and old high redshift
galaxies are not so restrictive, thereby suggesting that there is no age crisis
for this kind of cosmologies.Comment: 6 pages, 3 figures, revised version to appear in Phys. Rev.
Is CDM an effective CCDM cosmology?
We show that a cosmology driven by gravitationally induced particle
production of all non-relativistic species existing in the present Universe
mimics exactly the observed flat accelerating CDM cosmology with just
one dynamical free parameter. This kind of scenario includes the creation cold
dark matter (CCDM) model [Lima, Jesus & Oliveira, JCAP 011(2010)027] as a
particular case and also provides a natural reduction of the dark sector since
the vacuum component is not needed to accelerate the Universe. The new cosmic
scenario is equivalent to CDM both at the background and perturbative
levels and the associated creation process is also in agreement with the
universality of the gravitational interaction and equivalence principle.
Implicitly, it also suggests that the present day astronomical observations
cannot be considered the ultimate proof of cosmic vacuum effects in the evolved
Universe because CDM may be only an effective cosmology.Comment: 6 pages, 2 figures, changes in the abstract, introduction, new
references and typo correction
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