arXiv subjects

V. Capek

Publications and source records attributed to V. Capek.

4 recordsLinked to original sources

arXiv2002

Langevin approach to the Porto system

M. Porto (Phys. Rev. E 63 (2001) 030102) suggested a system consisting of Coulomb interacting particles, forming a linear track and a rotor, and working as a molecular motor. Newton equations with damping for the rotor coordinate on the track x, with a prescribed time-dependence of the rotor angle theta, indicated unidirectional motion of the rotor. Here, for the same system, the treatment was generalized to nonzero temperatures by including stochastic forces and treating both x and theta via two coupled Langevin equations. Numerical results are reported for stochastic homogeneous distributions of impact events and Gaussian distributions of stochastic forces acting on both the variables. For specific values of parameters involved, the unidirectional motion of the rotor along the track is confirmed, but with a mechanism that is not necessarily the same as that one by Porto. In an additional weak homogeneous potential field U(x)=const.x acting against the motion, the unidirectional motion persists. Then the rotor accumulates potential energy at the cost of thermal stochastic forces from the bath.

cond-mat.stat-mech↗

arXiv2002

Stationary flows in quantum dissipative closed circuits as a challenge to thermodynamics

An experimentally inspired model is constructed and rigorously solved from the Hamiltonian level where a dc circular spontaneous flow exists in absence of a magnetic field, irrespective of presence of dissipation causing otherwise proper relaxation. The flow causes a spontaneous unidirectional transfer of heat from one bath to another one, even against temperature step. This is what is explicitly forbidden by the Clausius form of the Second law of thermodynamics. The unidirectionality of the flow is caused by that of spontaneous processes known to bear this property since their introduction by Einstein. The model slightly improves the previous one (Čápek & Sheehan 2002), describes a realistic plasma system for which experimental results violating the second law were announced, and the result obtained fully supports the experimental conclusions (Sheehan 1995). Analytical proof of the violation is supported by numerical results. All mathematical details are exposed, two fully independent types of mathematical arguments behind starting equations are invoked, and no approximations that could be made responsible for the striking conclusions are used. It shows how the physics beyond the Second law is still little understood.

physics.plasm-ph↗

arXiv2001

Zeroth and Second Laws of Thermodynamics Simultaneously Questioned in the Quantum Microworld

Several models of quantum open systems are known at present to violate, according to principles of the standard quantum theory of open systems, the second law of thermodynamics. Here, a new and rather trivial model of another type is suggested describing mechanism that violates, according to the same principles, the zeroth and the second laws of thermodynamics simultaneously. Up to a technically minor modification, the model resembles some models already known, solved by standard means, and properly understood. Universal validity of two basic principles of thermodynamics in strictly quantum situations is thus simultaneously called in question.

cond-mat.stat-mech↗

arXiv2000

A Thought Construction of Working Perpetuum Mobile of the Second Kind

A previously published model of the isothermal Maxwell demon as one of models of open quantum systems endowed with faculty of selforganization is reconstructed here. It describes an open quantum system interacting with a single thermodynamic bath but otherwise not aided from outside. Its activity is given by the standard linear Liouville equation for the system and bath. Owing to its selforganization property, the model then yields cyclic conversion of heat from the bath into mechanical work without compensation. Hence, it provides an explicit thought construction of perpetuum mobile of the second kind, contradicting thus the Thomson formulation of the second law of thermodynamics. No approximation is involved as a special scaling procedure is used which makes the kinetic equations employed exact.

cond-mat.stat-mech↗