Irreversible processes such as solvation, energy transfer, and chemical binding have received renewed interest in recent years. Because these processes involve large systems with many degrees of freedom, the typical approach to studying these processes is the open quantum systems formalism, in which the degrees of freedom are partitioned into a system of interest and a bath held at thermal equi...

We extend a standard stochastic theory to study open quantum systems coupled to a generic quantum environment. We exemplify the general framework by studying a two-level quantum system coupled bilinearly to the three fundamental classes of non-interacting particles: bosons, fermions, and spins. In this unified stochastic approach, the generalized stochastic Liouville equation (SLE) formally cap...

When a system is thermally coupled to only small part of larger bath, statistical fluctuations the temperature (more precisely, internal energy) this ``sub-bath'' around mean defined by bath can become significant. We show that these generally give rise $1/f$-like noise power spectral density from even single two-level system. extend results distribution fluctuators, finding corresponding modif...

BACKGROUND Bath-PUVA-photochemotherapy has become a useful alternative to oral PUVA therapy due to a number of advantages over systemic PUVA, for example, no ophthalmologic risk and nausea, and a lower cumulative UVA doses. However, its major disadvantage is the logistical requirement for bath tubs in practice and some patients feel uncomfortable to share the same bath with others. Topical psor...

The stationary state of a quantum particle strongly coupled to a quantum thermal bath is known to be non-Gibbsian, due to entanglement with the bath. For harmonic potentials, where the system can be described by effective temperatures, thermodynamic relations are shown to take a generalized Gibbsian form that may violate the Clausius inequality. For the weakly anharmonic case, a Fokker-Planck-t...