arXiv subjects

Luigi Delle Site

Publications and source records attributed to Luigi Delle Site.

58 records · Page 4Linked to original sources

arXiv2006

Adaptive molecular resolution via a continuous change of the phase space dimensionality

For the study of complex synthetic and biological molecular systems by computer simulations one is still restricted to simple model systems or to by far too small time scales. To overcome this problem multiscale techniques are being developed for many applications. However in almost all cases, the regions of different resolution are fixed and not in a true equilibrium with each other. We here give the theoretical framework for an efficient and flexible coupling of the different regimes. The approach leads to an analog of a geometry induced phase transition and a counterpart of the equipartition theorem for fractional degrees of freedom. This provides a rather general formal basis for advanced computer simulation methods applying different levels of resolution.

cond-mat.stat-mech↗

arXiv2006

Variational approach to dequantization

We present a dequantization procedure based on a variational approach whereby quantum fluctuations latent in the quantum momentum are suppressed. This is done by adding generic local deformations to the quantum momentum operator which give rise to a deformed kinetic term quantifying the amount of ``fuzzyness'' caused by such fluctuations. Considered as a functional of such deformations, the deformed kinetic term is shown to possess a unique minimum which is seen to be the classical kinetic energy. Furthermore, we show that extremization of the associated deformed action functional introduces an essential nonlinearity to the resulting field equations which are seen to be the classical Hamilton-Jacobi and continuity equations. Thus, a variational procedure determines the particular deformation that has the effect of suppressing the quantum fluctuations, resulting in dequantization of the system.

quant-ph↗

arXiv2005

Adaptive Resolution Molecular Dynamics Simulation: Changing the Degrees of Freedom on the Fly

We present a new adaptive resolution technique for efficient particle-based multiscale molecular dynamics (MD) simulations. The presented approach is tailor-made for molecular systems where atomistic resolution is required only in spatially localized domains whereas a lower mesoscopic level of detail is sufficient for the rest of the system. Our method allows an on-the-fly interchange between a given molecule's atomic and coarse-grained level of description, enabling us to reach large length and time scales while spatially retaining atomistic details of the system. The new approach is tested on a model system of a liquid of tetrahedral molecules. The simulation box is divided into two regions: one containing only atomistically resolved tetrahedral molecules, the other containing only one particle coarse-grained spherical molecules. The molecules can freely move between the two regions while changing their level of resolution accordingly. The coarse-grained and the atomistically resolved systems have the same statistical properties at the same physical conditions.

cond-mat.soft↗

arXiv2005

Quantum-classical correspondence via a deformed kinetic operator

We propose an approach to the quantum-classical correspondence based on a deformation of the momentum and kinetic operators of quantum mechanics. Making use of the factorization method, we construct classical versions of the momentum and kinetic operators which, in addition to the standard quantum expressions, contain terms that are functionals of the N-particle density. We show that this implementation of the quantum-classical correspondence is related to Witten's deformation of the exterior derivative and Laplacian, introduced in the context of supersymmetric quantum mechanics. The corresponding deformed action is also shown to be related to the Fisher information. Finally, we briefly consider the possible relevance of our approach to the construction of kinetic-energy density functionals.

quant-ph↗