232,221 research outputs found
Escaping free-energy minima
We introduce a novel and powerful method for exploring the properties of the
multidimensional free energy surfaces of complex many-body systems by means of
a coarse-grained non-Markovian dynamics in the space defined by a few
collective coordinates.A characteristic feature of this dynamics is the
presence of a history-dependent potential term that, in time, fills the minima
in the free energy surface, allowing the efficient exploration and accurate
determination of the free energy surface as a function of the collective
coordinates. We demonstrate the usefulness of this approach in the case of the
dissociation of a NaCl molecule in water and in the study of the conformational
changes of a dialanine in solution.Comment: 3 figure
Free Energy of ABJM Theory
The free energy of ABJM theory has previously been computed in the strong and
weak coupling limits. In this note, we report on results for the computation of
the first non-vanishing quantum correction to the free energy, from the field
theory side. The correction can be expressed in terms of a thermal mass for the
scalar fields. This mass vanishes to 1-loop order, but there is a non-vanishing
result to 2-loop order. Hence, the leading correction to the free energy is
non-analytic in the 't Hooft coupling constant lambda. The reason is that the
infrared divergences necessitate a resummation of ring diagrams and a related
reorganization of perturbation theory, in which already the leading correction
receives contributions from all orders in lambda. These results suggest that
the free energy interpolates smoothly between weak and strong coupling.Comment: 6 pages. Contribution to the proceedings of the 16th European
Workshop on String Theory 2010, Real Jardin Botanico, Madrid, 14-18 June
2010. v2: published versio
Psychophysical identity and free energy
An approach to implementing variational Bayesian inference in biological
systems is considered, under which the thermodynamic free energy of a system
directly encodes its variational free energy. In the case of the brain, this
assumption places constraints on the neuronal encoding of generative and
recognition densities, in particular requiring a stochastic population code.
The resulting relationship between thermodynamic and variational free energies
is prefigured in mind-brain identity theses in philosophy and in the Gestalt
hypothesis of psychophysical isomorphism.Comment: 22 pages; published as a research article on 8/5/2020 in Journal of
the Royal Society Interfac
Gibbs free energy and Helmholtz free energy for a three-dimensional Ising-like model
The critical behavior of a 3D Ising-like system is studied at the microscopic
level of consideration. The free energy of ordering is calculated analytically
as an explicit function of temperature, an external field and the initial
parameters of the model. Within a unified approach, both Gibbs and Helmholtz
free energies are obtained and the dependencies of them on the external field
and the order parameter, respectively, are presented graphically. The regions
of stability, metastability, and unstability are established on the order
parameter-temperature plane. The way of implementation of the well-known
Maxwell construction is proposed at microscopic level.Comment: 10 pages, 4 figure
Exploring High Dimensional Free Energy Landscapes: Temperature Accelerated Sliced Sampling
Biased sampling of collective variables is widely used to accelerate rare
events in molecular simulations and to explore free energy surfaces. However,
computational efficiency of these methods decreases with increasing number of
collective variables, which severely limits the predictive power of the
enhanced sampling approaches. Here we propose a method called Temperature
Accelerated Sliced Sampling (TASS) that combines temperature accelerated
molecular dynamics with umbrella sampling and metadynamics to sample the
collective variable space in an efficient manner. The presented method can
sample a large number of collective variables and is advantageous for
controlled exploration of broad and unbound free energy basins. TASS is also
shown to achieve quick free energy convergence and is practically usable with
ab initio molecular dynamics techniques
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