1,720,977 research outputs found
Fluctuation relations for systems in a constant magnetic field
Full text linkThe validity of the fluctuation relations (FRs) for systems in a constant magnetic field is investigated. Recently introduced time-reversal symmetries that hold in the presence of static electric and magnetic fields and of deterministic thermostats are used to prove the transient FRs without invoking, as commonly done, inversion of the magnetic field. Steady-state FRs are also derived, under the t-mixing condition. These results extend the predictive power of important statistical mechanics relations. We illustrate this via the nonlinear response for the cumulants of the dissipation, showing how the alternative FRs enable one to determine analytically null cumulants also for systems in a single magnetic field
Erratum: Fluctuation relations for systems in a constant magnetic field (Physical Review E (2020) 102 (030101R) DOI: 10.1103/PhysRevE.102.030101)
Full text linkErratum. After the publication of this paper, we found an inconsequential mistake in the derivation of the dissipation function for the Nosé-Hoover thermostatted system, Eq. (17) of the original paper. A complete and correct derivation for O(0)(X) is now reported in Appendix B of Ref. [1], where, in particular, it is shown that (Formula Presented) (Figure Presented)
The semiclassical limit of the intermediate scattering function
No full textWe point out the existence of an oversimplification in a previously derived semiclassical limit for the intermediate scattering function and present a new derivation of the result. The new formula is similar to the previous one and maintains its symmetry properties (i.e. detailed balance). Unfortunately, our expression also contains a new factor, related to the Maslov index of the trajectories appearing in it, that prevents its numerical implementation
Fluctuation relations for dissipative systems in constant external magnetic field: Theory and molecular dynamics simulations
Full text linkWe illustrate how, contrary to common belief, transient Fluctuation Relations (FRs) for systems in constant external magnetic field hold without the inversion of the field. Building on previous work providing generalized time-reversal symmetries for systems in parallel external magnetic and electric fields, we observe that the standard proof of these important nonequilibrium properties can be fully reinstated in the presence of net dissipation. This generalizes recent results for the FRs in orthogonal fields-an interesting but less commonly investigated geometry-and enables direct comparison with existing literature. We also present for the first time a numerical demonstration of the validity of the transient FRs with nonzero magnetic field via nonequilibrium molecular dynamics simulations of a realistic model of liquid NaCl
Theory and methods for rare events
No full textThis paper reviews the transition path theory (TPT) for activated events and summarizes a
set of methods and algorithms to compute all relevant quantities of this theory: free energy, rate and
mechanism of the event. We provide a set of examples to illustrate the applicability of the methods to
problems in chemistry, biophysics and material science
On the establishment of thermal diffusion in binary Lennard-Jones liquids
Full text linkThe establishment of thermal diffusion in an Ar-Kr Lennard-Jones mixture is investigated via dynamical non equilibrium molecular dynamics [G. Ciccotti, G. Jacucci, Phys. Rev. Lett. 35, 789 (1975)]. We observe, in particular, the evolution of the density and temperature fields of the system following the onset of the thermal gradient. In stationary conditions, we also compute the Soret coefficient of the mixture. This study confirms that dynamical non equilibrium molecular dynamics is an effective tool to gather information on transient phenomena, even though the full evolution of the mass and energy fluxes associated to the temperature and density fields requires, in this case, a more substantial numerical effort than the one employed here
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Continuum mechanics from molecular dynamics via adiabatic time and length scale separation
No full textWe show how to construct, by exploiting adiabatic time and length scale separation between atomistic and continuum mechanics, a multiscale scheme for continuum dynamics free from macroscopic constitutive modeling. To do so, we introduce a new set of degrees of freedom that simultaneously represent the macroscopic and the microscopic dynamics, based on a space tessellation. In this new formulation, the dynamics of the macroscopic fields steers the microscopic particle dynamics by producing the conditions under which they evolve and, concurrently, the particle dynamics drives the evolution of the macroscopic fields by providing them with atomistically based constitutive information. Under conditions of adiabatic separation both in time and length scales, it is possible to decimate the tessellating cells and let the macroscopic equations of motion be driven by the time average of the terms coupling them with the microscopic degrees of freedom
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