Ivan Calvo

Zonal flows and long-distance correlations during the formation of the edge shear layer in the TJ-II stellarator (2009)

Calvo, Ivan, Carreras, Benjamin A., Garcia, Luis, Pedrosa, M. A., Hidalgo, Carlos

A theoretical interpretation is given for the observed long-distance correlations in potential fluctuations in TJ-II. The value of the correlation increases above the critical point of the transition...

Topological characterization of flow structures in resistive pressure-gradient-driven turbulence (2008)

Carreras, Benjamin A., Llerena, Irene, Garcia, Luis, Calvo, Ivan

Visualization of turbulent flows is a powerful tool to help understand the turbulence dynamics and induced transport. However, it does not provide a quantitative description of the observed...

Fractional Levy motion through path integrals (2008)

Calvo, Ivan, Sanchez, Raul, Carreras, Benjamin A.

Fractional Levy motion (fLm) is the natural generalization of fractional Brownian motion in the context of self-similar stochastic processes and stable probability distributions. In this paper we...

Path integral formulation of fractional Brownian motion for general Hurst exponent (2008)

Calvo, Ivan, Sanchez, Raul

In J. Phys. A: Math. Gen. 28, 4305 (1995), K. L. Sebastian gave a path integral computation of the propagator of subdiffusive fractional Brownian motion (fBm), i.e. fBm with a Hurst or...

Pseudochaotic poloidal transport in the laminar regime of the resistive ballooning instabilities (2008)

Calvo, Ivan, Garcia, Luis, Carreras, Benjamin A., Sanchez, Raul, Van Milligen, Boudewijn Ph.

In toroidal geometry, and prior to the establishment of a fully developed turbulent state, the so-called topological instability of the pressure-gradient-driven turbulence is observed. In this...

Fractional generalization of Fick's law: a microscopic approach (2007)

Calvo, Ivan, Sanchez, Raul, Carreras, Benjamin A., Van Milligen, Boudewijn Ph.

In the study of transport in inhomogeneous systems it is common to construct transport equations invoking the inhomogeneous Fick law. The validity of this approach requires that at least two...

Continuous Time Random Walks in periodic systems: fluid limit and fractional differential equations on the circle (2007)

Calvo, Ivan, Carreras, B. A., Sanchez, R., Van Milligen, B. Ph.

In this article, the continuous time random walk on the circle is studied. We derive the corresponding generalized master equation and discuss the effects of topology, especially important when Levy...

Poisson sigma models on surfaces with boundary: classical and quantum aspects (2007)

Calvo, Ivan

The topics covered in this thesis may be divided into three parts. Firstly, we perform a study on the most general branes which are consistent with the Poisson sigma model, both at the classical and...

Poisson sigma models on surfaces with boundary: classical and quantum aspects (2007)

Calvo, Ivan

The topics covered in this thesis may be divided into three parts. Firstly, we perform a study on the most general branes which are consistent with the Poisson sigma model, both at the classical and...

Bopp operators and phase-space spin dynamics: Application to rotational quantum brownian motion (2006)

Zueco, D., Calvo, Ivan

As already known for nonrelativistic spinless particles, Bopp operators give an elegant and simple way to compute the dynamics of quasiprobability distributions in the phase space formulation of...

Effects of constraints in general branched molecules: A quantitative ab initio study in HCO-L-Ala-NH2 (2006)

Echenique, Pablo, Alonso, J. L., Calvo, Ivan

A general approach to the design of accurate classical potentials for protein folding is described. It includes the introduction of a meaningful statistical measure of the differences between...

Quantum mechanical calculation of the effects of stiff and rigid constraints in the conformational equilibrium of the Alanine dipeptide (2006)

Echenique, Pablo, Calvo, Ivan, Alonso, J. L.

If constraints are imposed on a macromolecule, two inequivalent classical models may be used: the stiff and the rigid one. This work studies the effects of such constraints on the Conformational...

Explicit factorization of external coordinates in constrained Statistical Mechanics models (2005)

Echenique, Pablo, Calvo, Ivan

If a macromolecule is described by curvilinear coordinates or rigid constraints are imposed, the equilibrium probability density that must be sampled in Monte Carlo simulations includes the...

Dual branes in topological sigma models over Lie groups. BF-theory and non-factorizable Lie bialgebras (2005)

Calvo, Ivan, Falceto, Fernando

We complete the study of the Poisson-Sigma model over Poisson-Lie groups. Firstly, we solve the models with targets $G$ and $G^*$ (the dual group of the Poisson-Lie group $G$) corresponding to a...

Supersymmetric WZ-Poisson sigma model and twisted generalized complex geometry (2005)

Calvo, Ivan

It has been shown recently that extended supersymmetry in twisted first-order sigma models is related to twisted generalized complex geometry in the target. In the general case there are additional...

Star products and branes in Poisson-Sigma models (2005)

Calvo, Ivan, Falceto, Fernando

We prove that non-coisotropic branes in the Poisson-Sigma model are allowed at the quantum level. When the brane is defined by second-class constraints, the perturbative quantization of the model...

Poisson-Dirac branes in Poisson-Sigma models (2005)

Calvo, Ivan, Falceto, Fernando

We analyse the general boundary conditions (branes) consistent with the Poisson-sigma model and study the structure of the phase space of the model defined on the strip with these boundary...

Poisson reduction and branes in Poisson-Sigma models (2004)

Calvo, Ivan, Falceto, Fernando

We analyse the problem of boundary conditions for the Poisson-Sigma model and extend previous results showing that non-coisotropic branes are allowed. We discuss the canonical reduction of a Poisson...

Topological Poisson Sigma models on Poisson-Lie groups (2003)

Calvo, Ivan, Falceto, Fernando, Garcia-Alvarez, David

We solve the topological Poisson Sigma model for a Poisson-Lie group $G$ and its dual $G^*$. We show that the gauge symmetry for each model is given by its dual group that acts by dressing...