Brownian motion: a case of temperature fluctuations

A diffusion process of a Brownian particle in a medium of temperature $T$ is re-considered. We assume that temperature of the medium fluctuates around its mean value. The velocity probability distribution is obtained. It is shown that the stationary state is not a thermodynamic equilibrium state described by the Maxwell distribution. Instead a nonequilibrium state is produced by temperature fluctuations.Comment: accepted for publication in Acta Physica Polonica

Geometric phase as a determinant of a qubit--environment coupling

We investigate the qubit geometric phase and its properties in dependence on the mechanism for decoherence of a qubit weakly coupled to its environment. We consider two sources of decoherence: dephasing coupling (without exchange of energy with environment) and dissipative coupling (with exchange of energy). Reduced dynamics of the qubit is studied in terms of the rigorous Davies Markovian quantum master equation, both at zero and non--zero temperature. For pure dephasing coupling, the geometric phase varies monotonically with respect to the polar angle (in the Bloch sphere representation) parameterizing an initial state of the qubit. Moreover, it is antisymmetric about some points on the geometric phase-polar angle plane. This is in distinct contrast to the case of dissipative coupling for which the variation of the geometric phase with respect to the polar angle typically is non-monotonic, displaying local extrema and is not antisymmetric. Sensitivity of the geometric phase to details of the decoherence source can make it a tool for testing the nature of the qubit--environment interaction.Comment: accepted for publication in Quantum Information Processin

The perception of polish organic food consumers

This paper presents the problems concerning the organic food demand in Poland. It indicates the reasons for such small interest in this kind of food, the main motives of purchase, and the barriers of market development. It also shows the ways of developing the organic food market development

Absolute negative mobility induced by white Poissonian noise

We research the transport properties of inertial Brownian particles which move in a symmetric periodic potential and are subjected to both a symmetric, unbiased time-periodic external force and biased Poissonian white shot noise (of non-zero average F) being composed of a random sequence of delta-shaped pulses with random amplitudes. Upon varying the parameters of white shot-noise one conveniently can manipulate the transport direction and the overall nonlinear response behavior. Within tailored parameter regimes, we find that the response is opposite to the applied average bias F of such white shot noise. This very transport characteristics thus mimics a nonlinear Absolute Negative Mobility (ANM) regime. Moreover, such white shot noise driven ANM is robust with respect to statistics of the shot noise spikes. Our findings can be checked and corroborated experimentally by use of a setup that consists of a single resistively and capacitively shunted Josephson junction device.Comment: 14 pages, 12 figures; accepted in J. Stat. Mech.: Theor. Exp. (2013