24,527 research outputs found
Dundee Discussion Papers in Economics 179:Activism, separation of powers and development
We consider a model of constitutional (mechanism) design with separation of powers where different institutions are assigned different tasks. In this context, we define activism as an institution extending its mechanism of decision-making into the domain of other institution’s tasks. When members of the institutions are likely to be benevolent as well as non-benevolent, such activism in a limited form reduces the cost of achieving collusion-proofness and raises welfare. Hence the value of such activism can be potentially very high in the context of developing economies. But as the fraction of non-benevolent member increases, such activism turns excessive and reduces welfare. It is argued that developing economies are likely to get caught in the excessive activism trap because of the high levels of corruption and bribery
Spin-Charge Decoupling and Orthofermi Quantum Statistics
Currently Gutzwiller projection technique and nested Bethe ansatz are two
main methods used to handle electronic systems in the infinity limit. We
demonstrate that these two approaches describe two distinct physical systems.
In the nested Bethe ansatz solutions, there is a decoupling between the spin
and charge degrees of freedom. Such a decoupling is absent in the Gutzwiller
projection technique. Whereas in the Gutzwiller approach, the usual
antisymmetry of space and spin coordinates is maintained, we show that the
Bethe ansatz wave function is compatible with a new form of quantum statistics,
viz., orthofermi statistics. In this statistics, the wave function is
antisymmetric in spatial coordinates alone. This feature ultimately leads to
spin-charge decoupling.Comment: 12 pages, LaTex Journal_ref: A slightly abridged version of this
paper has appeared as a brief report in Phys. Rev. B, Vol. 63, 132405 (2001
Effect of geometrical size of the particles in a hot and dense hadron gas
Incorporation of the finite size of baryons into the equation of state (EOS)
of a hot and dense hadron gas (HG) in a thermodynamically consistent manner has
been a much studied problem. We first review its current status. Various models
have been proposed in order to account for the repulsive force generated by the
hard-core geometrical size of the baryons resulting in an excluded volume
effect in the EOS. We examine the criterion of the thermodynamical consistency
of these models and summarize their shortcomings. In order to remove the
shortcomings, we propose a new model which incorporates the excluded volume
effect in a thermodynamically consistent manner. We find that the new model
works even for the cases of extremely large temperatures and densities where
most of other approaches fail. Furthermore, the new expressions for
thermodynamical variables resemble in form with those obtained from
thermodynamically inconsistent models and thus a useful correction factor has
been suggested here which converts inconsistent expressions into
thermodynamically consistent ones. Finally we compare the predictions of new
model with those obtained from various old models.Comment: 19 pages, 9 figures, accepted for publication in Phys. Rev.
Vector meson masses in hot nuclear matter : the effect of quantum corrections
The medium modification of vector meson masses is studied taking into account
the quantum correction effects for the hot and dense hadronic matter. In the
framework of Quantum Hadrodynamics, the quantum corrections from the baryon and
scalar meson sectors were earlier computed using a nonperturbative variational
approach through a realignment of the ground state with baryon-antibaryon and
sigma meson condensates. The effect of such corrections was seen to lead to a
softer equation of state giving rise to a lower value for the compressibility
and, an increase in the in-medium baryonic masses than would be reached when
such quantum effects are not taken into account. These quantum corrections
arising from the scalar meson sector result in an increase in the masses of the
vector mesons in the hot and dense matter, as compared to the situation when
only the vacuum polarisation effects from the baryonic sector are taken into
account.Comment: 13 pages revtex file, 6 figure
Photoinduced magnetism in the ferromagnetic semiconductors
We study the enhancement of the magnetic transition temperature due to
incident light in ferromagnetic semiconductors such as EuS. The photoexcited
carriers mediate an extra ferromagnetic interaction due to the coupling with
the localized magnetic moments. The Hamiltonian consists of a Heisenberg model
for the localized moments and an interaction term between the photoexcited
carriers and the localized moments. The model predicts a small enhancement of
the transition temperature in semi-quantitative agreement with the experiments.Comment: 5 pages, 5 figure
Fabrication of Nano-Gapped Single-Electron Transistors for Transport Studies of Individual Single-Molecule Magnets
Three terminal single-electron transistor devices utilizing Al/Al2O3 gate
electrodes were developed for the study of electron transport through
individual single-molecule magnets. The devices were patterned via multiple
layers of optical and electron beam lithography. Electromigration induced
breaking of the nanowires reliably produces 1-3 nm gaps between which the SMM
can be situated. Conductance through a single Mn12(3-thiophenecarboxylate)
displays the coulomb blockade effect with several excitations within +/- 40
meV.Comment: 10 pages, 5 figure
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