447 research outputs found
Colored noise in the fractional Hall effect: duality relations and exact results
We study noise in the problem of tunneling between fractional quantum Hall
edge states within a four probe geometry. We explore the implications of the
strong-weak coupling duality symmetry existent in this problem for relating the
various density-density auto-correlations and cross-correlations between the
four terminals. We identify correlations that transform as either ``odd'' or
``anti-symmetric'', or ``even'' or ``symmetric'' quantities under duality. We
show that the low frequency noise is colored, and that the deviations from
white noise are exactly related to the differential conductance. We show
explicitly that the relationship between the slope of the low frequency noise
spectrum and the differential conductance follows from an identity that holds
to {\it all} orders in perturbation theory, supporting the results implied by
the duality symmetry. This generalizes the results of quantum supression of the
finite frequency noise spectrum to Luttinger liquids and fractional statistics
quasiparticles.Comment: 14 pages, 3 figure
Electoral rules, political competition and fiscal spending : regression discontinuity evidence from Brazilian municipalities
We exploit a discontinuity in Brazilian municipal election rules to investigate whether political competition has a causal impact on policy choices. In municipalities with less than 200,000 voters mayors are elected with a plurality of the vote. In municipalities with more than 200,000 voters a run-off election takes place among the top two candidates if neither achieves a majority of the votes. At a first stage, we show that the possibility of runoff increases political competition. At a second stage, we use the discontinuity as a source of exogenous variation to infer causality from political competition to fiscal policy. Our second stage results suggest that political competition induces more investment and less current spending, particularly personnel expenses. Furthermore, the impact of political competition is larger when incumbents can run for reelection, suggesting incentives matter insofar as incumbents can themselves remain in office.Electoral Systems; Strategic Voting; Political Competition; Regression Discontinuity; Fiscal Spending. JEL Codes: H72; D72; C14; P1
Study of the effects of Pauli blocking and Pauli non-locality on the optical potential
Elastic scattering angular distributions for systems with reduced mass
between 3 and 34 and energies varying between 25 and 120 MeV/nucleon were
analyzed. The stable He, its exotic partner He, and the weakly bound
Li nuclei were included as projectiles in the systematics. Optical
model data analyzes were performed with an adjustable factor of normalization
included in the imaginary part of the potential. These analyzes indicated a
reduction of absorption for systems with small reduced masses that was detected
due to the refractive nature of the scattering by light systems.Comment: 16 pages, 7 figure
Correlations in one dimensional quantum impurity problems with an external field
We study response functions of integrable quantum impurity problems with an
external field at using non perturbative techniques derived from the
Bethe ansatz. We develop the first steps of the theory of excitations over the
new, field dependent ground state, leading to renormalized (or ``dressed'')
form-factors. We obtain exactly the low frequency behaviour of the dynamical
susceptibility in the double well problem of dissipative
quantum mechanics (or equivalently the anisotropic Kondo problem),and the low
frequency behaviour of the AC noise for tunneling between edges
in fractional quantum Hall devices. We also obtain exactly the structure of
singularities in and . Our results differ
significantly from previous perturbative approaches.Comment: harvmac, epsf, 37pgs, 2figs. modified some reference
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