Nonequilibrium Phase Diagram of a Driven-Dissipative Many-Body System

We study the nonequilibrium dynamics of a many-body bosonic system on a lattice, subject to driving and dissipation. The time-evolution is described by a master equation, which we treat within a generalized Gutzwiller mean field approximation for density matrices. The dissipative processes are engineered such that the system, in the absence of interaction between the bosons, is driven into a homogeneous steady state with off-diagonal long range order. We investigate how the coherent interaction affects qualitatively the properties of the steady state of the system and derive a nonequilibrium phase diagram featuring a phase transition into a steady state without long range order. The phase diagram exhibits also an extended domain where an instability of the homogeneous steady state gives rise to a persistent density pattern with spontaneously broken translational symmetry. In the limit of small particle density, we provide a precise analytical description of the time-evolution during the instability. Moreover, we investigate the transient following a quantum quench of the dissipative processes and we elucidate the prominent role played by collective topological variables in this regime.Comment: 23 pages, 15 figure

Fine Structure of Spermiogenesis in the Tick Amblyomma Hebraeum (Acari: Ixodidae): Late Stages of Differentiation and Structure of the Mature Spermatozoon

Spermatids of Amblyomma hebraeum were examined by light and electron microscopy. These large, elongate, tubular cells are pointed at one end and truncate at the other. Each is composed of an outer sheath and an inner cord. The outer sheath lining and the inner cord surface are composed of cellular processes joined at the truncate end of the sperm cell. The nucleus is in the outer sheath. The semispherical apex of the inner cord is covered by numerous bulbous expansions. The final stage of spermiogenesis is the simultaneous evagination of the inner cord at the pointed end and invagination of the outer sheath at the truncate end of the cell. The mature spermatozoon, ca. 200 μm long and consisting of the inner cord added to the former outer sheath, is clavate anteriorly and caudate posteriorly, where the nucleus is located. The mature spermatozoon contains β-glycogen particles and large peripheral granules. A prominent acrosomal complex associated with the nucleus is observed in the aging spermatozoon. The cellular processes and/or the fibrillar granular cytoplasm may have a role in sperm movemen