Transport through a double barrier in Large Radius Carbon Nanotubes in the presence of a transverse magnetic field

We discuss the Luttinger Liquid behaviour of Large Radius Carbon Nanotube e.g. the Multi Wall ones (MWNT), under the action of a transverse magnetic field $B$. Our results imply a reduction with $B$ in the value of the $bulk$ critical exponent, $\alpha_{bulk}$, for the tunneling density of states, which is in agreement with that observed in transport experiments. Then, the problem of the transport through a Quantum Dot formed by two intramolecular tunneling barriers along the MWNT, weakly coupled to Tomonaga-Luttinger liquids is studied, including the action of a strong transverse magnetic field $B$. {We predict the presence of some peaks in the conductance G versus $B$, related to the magnetic flux quantization in the ballistic regime (at a very low temperature, $T$) and also at higher $T$, where the Luttinger behaviour dominates}. The temperature dependence of the maximum $G_{max}$ of the conductance peak according to the Sequential Tunneling follows a power law, $G\propto T^{\gamma_e-1}$ with $\gamma_e$ linearly dependent on the critical exponent, $\alpha_{end}$, strongly reduced by $B$.Comment: 8 pages, 3 figures, PACS numbers: 05.60.Gg, 71.10.Pm, 73.63.-b, 71.20.Tx, 72.80.R

Risk-adjusted measures of value creation in financial institutions

Measuring value creation by comparing the RAROC of an exposure (the return on risk capital) with a single institution-wide hurdle rate is inconsistent with the standard theory of financial valuation. We use asset pricing theory to determine the appropriate hurdle rate for such a RAROC performance measure. We find that this hurdle rate varies with the skewness of asset returns. Thus the RAROC hurdle rate should differ substantially between equity which has a right skew and debt which has a pronounced left skew and also between different qualities of debt exposure. We discuss implications for financial institution risk management and supervision.asset pricing; banking; capital allocation; capital budgeting; capital management; corporate finance; downside risk; economic capital; performance measurement; RAROC; risk management; value creation; hurdle rate; value at risk

Large N Effects and Renormalization of the Long-Range Coulomb Interaction in Carbon Nanotubes

We develop a dimensional regularization approach to deal with the low-energy effects of the long-range Coulomb interaction in 1D electron systems. The method allows us to avoid the infrared singularities arising from the long-range Coulomb interaction at D = 1, providing at the same time insight about the fixed-points of the theory. We show that the effect of increasing the number N of subbands at the Fermi level is opposite to that of approaching the bare Coulomb interaction in the limit D --> 1. Then, we devise a double scaling limit, in which the large N effects are able to tame the singularities due to the long-range interaction. Thus, regular expressions can be obtained for all observables right at D = 1, bearing also a dependence o the doping level of the system. Our results imply a variation with N in the value of the exponent for the tunneling density of states, which is in fair agreement with that observed in different transport experiments involving carbon nanotubes. As the doping level is increased in nanotubes of large radius and multi-walled nanotubes, we predict a significant reduction of order N^{-1/2} in the critical exponent of the tunneling density of states.Comment: 16 pages, 5 figures, PACS codes: 73.40, 11.10.

Weak versus strong wave turbulence in the MMT model

Within the spirit of fluid turbulence, we consider the one-dimensional Majda-McLaughlin-Tabak (MMT) model that describes the interactions of nonlinear dispersive waves. We perform a detailed numerical study of the direct energy cascade in the defocusing regime. In particular, we consider a configuration with large-scale forcing and small scale dissipation, and we introduce three non- dimensional parameters: the ratio between nonlinearity and dispersion, {\epsilon}, and the analogues of the Reynolds number, Re, i.e. the ratio between the nonlinear and dissipative time-scales, both at large and small scales. Our numerical experiments show that (i) in the limit of small {\epsilon} the spectral slope observed in the statistical steady regime corresponds to the one predicted by the Weak Wave Turbulence (WWT) theory. (ii) As the nonlinearity is increased, the WWT theory breaks down and deviations from its predictions are observed. (iii) It is shown that such departures from the WWT theoretical predictions are accompanied by the phenomenon of intermittency, typical of three dimensional fluid turbulence. We calculate the structure-function as well as the probability density function of the wave field at each scale and show that the degree of intermittency depends on {\epsilon}.Comment: 7 pages, 6 figure

Legislative malapportionment and institutional persistence

This paper argues that legislative malapportionment, denoting a discrepancy between the share of legislative seats and the share of population held by electoral districts, serves as a tool for pre-democratic elites to preserve their political power and economic interests after a transition to democracy. The authors claim that legislative malapportionment enhances the pre-democratic elite’s political influence by over-representing areas that are more likely to vote for parties aligned with the elite. This biased political representation survives in equilibrium as long as it helps democratic consolidation. Using data from Latin America, the authors document empirically that malapportionment increases the probability of transitioning to a democracy. Moreover, the data show that over-represented electoral districts are more likely to vote for parties close to pre-democracy ruling groups. The analysis also finds that overrepresented areas have lower levels of political competition and receive more transfers per capita from the central government, both of which favor the persistence of power of pre-democracy elites.Parliamentary Government,Labor Policies,Emerging Markets,Political Economy,Political Systems and Analysis

Legislative Malapportionment and institutional persistence

This paper argues that legislative malapportionment, denoting a discrepancy between the share of legislative seats and the share of population held by electoral districts, serves as a tool for predemocratic elites to preserve their political power and economic interests after a transition to democracy. We claim that legislative malapportionment enhances the pre-democratic elite’s political influence by overrepresenting areas that are more likely to vote for parties aligned with the elite. This biased political representation survives in equilibrium as long as it helps democratic consolidation. We use data from Latin America to document empirically that malapportionment increases the probability of transitioning to a democracy. Moreover, our data show that overrepresented electoral districts are more likely to vote for parties close to pre-democracy ruling groups. We also find that overrepresented areas have lower levels of political competition and they receive more transfers per capita from the central government, both of which favor the persistence of power of pre-democracy elites.Democracy, dictatorship, institutions, Latin America, persistence, political economy