Keldysh field theory for nonequilibrium condensation in a parametrically pumped polariton system

We develop a quantum field theory for parametrically pumped polaritons using Keldysh Green's function techniques. By considering the mean-field and Gaussian fluctuations, we find that the low energy physics of the highly non-equilibrium phase transition to the optical parametric oscillator regime is in many ways similar to equilibrium condensation. In particular, we show that this phase transition can be associated with an effective chemical potential, at which the system's bosonic distribution function diverges, and an effective temperature. As in equilibrium systems, the transition is achieved by tuning this effective chemical potential to the energy of the lowest normal mode. Since the occupations of the modes are available, we determine experimentally observable properties, such as the luminescence and absorption spectra.Comment: 16 pages, 14 figure

Rare quantum metastable states in the strongly dispersive Jaynes-Cummings oscillator

We present evidence of metastable rare quantum-fluctuation switching for the driven dissipative Jaynes-Cummings oscillator coupled to a zero-temperature bath in the strongly dispersive regime. We show that single-atom complex amplitude bistability is accompanied by the appearance of a low-amplitude long-lived transient state, hereinafter called `dark state', having a distribution with quasi-Poissonian statistics both for the coupled qubit and cavity mode. We find that the dark state is linked to a spontaneous flipping of the qubit state, detuning the cavity to a low-photon response. The appearance of the dark state is correlated with the participation of the two metastable states in the dispersive bistability, as evidenced by the solution of the Master Equation and single quantum trajectories.Comment: Extensively revised text, 18 revised figures (16 in main and 2 in appendix), 38(+1) references, appendi

Non-equilibrium quantum condensation in an incoherently pumped dissipative system

We study spontaneous quantum coherence in an out of equilibrium system, coupled to multiple baths describing pumping and decay. For a range of parameters describing coupling to, and occupation of the baths, a stable steady-state condensed solution exists. The presence of pumping and decay significantly modifies the spectra of phase fluctuations, leading to correlation functions that differ both from an isolated condensate and from a laser.Comment: 5 pages, 2 eps figure

First-order dissipative phase transition in an exciton-polariton condensate

We investigate the phase diagram of a two-dimensional driven-dissipative system of polaritons coupled to an excitonic reservoir. We find that two critical points exists. The first corresponds to the quasicondensation and the second to a first-order phase transition from the nonuniform state with spatially modulated density to a uniform state. The latter is related to the modulational instability of a homogeneous state due to the repulsive interactions with the noncondensed reservoir. The first-order character of the transition is evidenced by a discontinuity in the density and the correlation length as well as the phase coexistence and metastability. Moreover, we show that a signature of a Berezinskii-Kosterlitz-Thouless-like transition can be observed in the nonuniform phase

Thermodynamics and Excitations of Condensed Polaritons in Disordered Microcavities

We study the thermodynamic condensation of microcavity polaritons using a realistic model of disorder in semiconductor quantum wells. This approach correctly describes the polariton inhomogeneous broadening in the low density limit, and treats scattering by disorder to all orders in the condensed regime. While the weak disorder changes the thermodynamic properties of the transition little, the effects of disorder in the condensed state are prominent in the excitations and can be seen in resonant Rayleigh scattering.Comment: 5 pages, 3 eps figures (published version

POLISH TOWNS AND THE CHANGES IN THEIR AREAS AND POPULATION DENSITIES

DOI: 10.2478 Available on-line at: http://www.bulletinofgeography.umk.pl http://versita.com/bgssThis article presents the spatial and population density changes in Polish towns in the years 1960–2003. The assumed time frame allowed identifying area changes for a complete set of towns in different socio-economic conditions: the period of intense industrialisation, the economic crisis of the 1980s, the period of economic transition and finally in the years of a market economy. The investigation revealed that the trend shown by changes and the size of a town as measured by the number of its population are distinctly interrelated. It also demonstrated a much stronger dynamics of changes in the first subperiod, i.e. years 1960–1985, followed by a phase of relative stabilization (compared with the previous period) after the year 1980 (mainly of the spatial changes). Moreover, change intensity and change trends observed for the urban areas and population densities vary considerably in terms of space

Simultaneous bistability of qubit and resonator in circuit quantum electrodynamics

We explore the joint activated dynamics exhibited by two quantum degrees of freedom: a cavity mode oscillator which is strongly coupled to a superconducting qubit in the strongly coherently driven dispersive regime. Dynamical simulations and complementary measurements show a range of parameters where both the cavity and the qubit exhibit sudden simultaneous switching between two metastable states. This manifests in ensemble averaged amplitudes of both the cavity and qubit exhibiting a partial coherent cancellation. Transmission measurements of driven microwave cavities coupled to transmon qubits show detailed features which agree with the theory in the regime of simultaneous switching

Infrastructure's and housing's development in the rural areas in Poland - some problems

The article refers to an analysis and an evaluation of changes in the technical infrastructure and housing in the rural areas in Poland in the years 1995-2008. The article covered all rural and rural-urban (excluding urban parts) gminas in Poland that altogether amount to 2,172 units (as of 2008). It was stated that in the rural areas in Poland a population density increases and it is caused mainly by dynamic suburbanisation processes and by a population movement from cities and towns towards suburban gminas, in the less degree by a natural increase. In the article there were presented spatial variations of rural gminas in the following elements: a length of the water-line and sewerage networks per 100 km2; a share of water-line and of sewerage systems’ users; a number of dwellings per 1,000 population; a number of rooms per 1 person; the usable floor space of a dwelling in m2 per 1 person; a share of dwellings fitted with water-line system and a share of dwellings equipped with flush toilet and bathroom. It was also shown that there are relationships between population density and infrastructure’s and housing’s elements by proving positive as well as negative correlations

Craniofacial structure in patients with obstructive sleep apnoea

Background: Obstructive sleep apnoea (OSA) is characterised by at least five 10-s episodes of apnoea or markedly shallow breathing per 1 h of sleep, which can lead to severe, sometimes life-threatening complications. It is essential to determine the specific features of the affected patients’ craniofacial structure, thus enabling their allocation to risk groups. The aim of the study was to assess the craniofacial structure in OSA patients, comparing the findings with Hasund’s and Segner’s cephalometric normal values. In addition, the sagittal dimensions of the upper airways, measured at two levels, were compared to McNamara’s normal values. Materials and methods: The study covered 41 patients diagnosed polysomno­graphically with OSA. Lateral cephalograms with cephalometric analysis and the measurements of the upper and lower sagittal dimensions of the upper airways were taken for each patient. Results: The only feature of the patents’ facial skeleton that significantly diverged from the normal range was the SNB angle (p = 0.004). Other angles, i.e. SNA, ANB, NL/NSL, NL/ML and NSL/ML, were not significantly different from normal. The average upper cross-sectional area of the upper airways was 10.4 mm; in 97.6% patients, this measurement was below McNamara’s normal values. In the majority of patients (75.6%), the average lower sagittal dimension of the upper airways (10.4 mm) was also below the normal. Conclusions: Mandibular retrognathia, manifested by the reduced SNB angle, and the narrowed upper and lower sagittal dimensions of the upper airways can be considered one of OSA prognostic factors