Condensate Density Research Articles

The Staggered Fermion for the Gross-Neveu Model at Non-Zero Temperature and Density

The 2 + 1d Gross-Neveu model with finite density and finite temperature is studied by the staggered fermion discretization. The kinetic part of this staggered fermion in momentum space is used to build the relation between the staggered fermion and Wilson-like fermion. In the large Nf limit (the number Nf of staggered fermion flavors), the chiral condensate and fermion density are solved from the gap equation in momentum space, and thus the phase diagram of fermion coupling, temperature and chemical potential is obtained. Moreover, an analytic formula for the inverse of the staggered fermion matrix is given explicitly, which can be calculated easily by parallelization. The generalization to the 1 + 1d and 3 + 1d cases is also considered.

Large-N Expansion for Condensation and Stability of Bose–Bose Mixtures at Finite Temperatures

The two-component mixture of Bose particles with short-range pairwise interaction at finite temperatures in three dimensions is considered. Particularly we examine, by means of the large-$N$ expansion technique, the stability of mixed state below the Bose-Einstein transition point and the temperature dependence of the condensate density for symmetric mixture of Bose gases. The presented analysis reveals the importance of finite-temperature excitations of the non-condensed particles in formation of the phase diagram of two-component Bose systems.

Investigation of the State and Method of Controlling the Parameters of a Two-Phase Vapor System in its Flow in a Channel

A wide area for application of vapor in heat power industry has been shown. Due to this, the problem of maintaining and controlling the dryness of steam during its transportation through steam pipelines remains of current importance. Quite detailed theoretical investigations into the steam parameters during its flow in the pipe have been carried out. A comparative analysis of steam velocity and temperature epures as a function of certain parameters and assumed approximations has been conducted. All calculations have been brought to quantitative results. As a result of the implemented analysis, it has been shown that the uncertainty of exact values of some quantities does not play a crucial role in common patterns of the formation of a dropping liquid. As a result of numerical investigations into the kinetics of steam condensation, the specific volume and density of the droplet condensate across the pipe have been identified. The obtained results and the proposed methodological approach to identifying steam parameters have been used in the development and further improvement of a device to measure dryness of steam whose original design was proposed earlier by one of the authors. The functional diagram and the prototype model of the batchbox of the measuring device are given in this investigation.

Effect of Disorder Amplitude on the Transport of Bose Einstein Condensates at Lowest Energy

In this paper, we have presented an analytical and numerical study of a matter wave packet propagation in a disordered optical potential. We have used the self-consistent Born approximation which is well supported in weak disorder to calculate the real part of the self- energy RΣ(e, p). The difference of 0.1 which appears between the analytical and numerical calculation is very acceptable. The varying of disorder amplitude change the position of the critical energy of the transition which it can be larger or smaller than correlation energy. This analysis gives new insight into numerical result. We propose to analyze the behavior of the energy distribution with this quantum corrected diffusion factor, which is a very important parameter for the mobility edge prediction. Our results open new interesting studies and provide good reference data for future research such as the behavior of the mobility edge in fractal systems and the evolution of the density of condensates in time and space.

Quantum Gases of Dipoles, Quadrupoles and Octupoles in Gross–Pitaevskii Formalism with Form Factor

Here, classical and quantum field theory of dipolar, axisymmetric quadrupolar and octupolar Bose gases is considered within a general approach. Dipole, axisymmetric quadrupole and octupole interaction potentials in the momentum representation are calculated. These results clearly demonstrate attraction and repulsion areas in corresponding gases. Then the Gross–Pitaevskii (GP) equation, which plays a key role in the present paper, is derived from the corresponding functional. The zoology of the form factors appearing in the GP equation is studied in details. The proper classes for the description of spatially non-uniform condensates form factors are chosen. In the Thomas–Fermi approximation a general solution of the GP equation with a quasilocal form factor is obtained. This solution has an interesting form in terms of a double rapidly converging series that universally includes all the interactions considered. Plots of condensate density functions for the exponential-trigonometric form factor are given. For the sake of completeness, in this paper we consider the GP equation with an optical lattice potential in the limit of small condensate densities. This limit does not distinguish between dipolar, quadrupolar and octupolar gases. An important analysis of the condensate stability, in other words the study of condensate excitations, is also performed in this paper. In the Gaussian approximation (from the Gross–Pitaevskii functional), a functional describing the perturbations of the condensate is derived in detail. This problem is an analog of the Bogolubov transformation used in the study of quantum Bose gases in operator formalism. For a probe wave function in the form of a plane wave, a spectrum of (Bogoliubov) excitations was obtained, from which an equation describing the threshold momentum for the emergence of instability was derived. An important result of this paper is the dependence of the threshold on the momentum of a stationary condensate. For completeness of the presentation, the approximating expression in the form of a rapidly converging series is obtained for the corresponding dependence, and plots of the corresponding series for the exponential-trigonometric form factor are given. Finally, in the conclusion a quantum hydrodynamic theory for dipolar, axisymmetric quadrupolar and octupolar gases is briefly presented, giving a clue to the experimental determination of the form factors.

Condensate Density of a Bose Gas Confined between Two Parallel Plates in Canonical Ensemble within Improved Hartree-Fock Approximation

By means of Cornwall-Jackiw-Tomboulis (CJT) effective action approach, the condensate density of a dilute Bose gas is investigated in the canonical ensemble. Our results show that the condensate density is proportional to a half-integer power law of the s-wave scattering length and distance between two plates. Apart from that, these quantities also depend on the particle number and area of each plate.

Inverse moment of the Bs-meson distribution amplitude from QCD sum rule

We derive a QCD sum rule for the inverse moment of the Bs-meson light-cone distribution amplitude in HQET. Within this method, the SU(3)f l symmetry violation is traced to the strange quark mass and to the difference between strange and nonstrange quark condensate densities. We predict the ratio of inverse moments λBs/λB = 1.19 ± 0.14 which can be used in various applications of these distribution amplitudes to the analyses of Bs-meson decays, provided an accurate value of λB is available from other sources, such as the B → ℓνℓγ decay.

Temperature dependence of the density and excitations of dipolar droplets

Droplet states of ultracold gases which are stabilized by fluctuations have recently been observed for dipolar and two component Bose gases. These systems present a novel form of equilibrium where an instability at the mean field level is arrested by higher order correlations making the droplet states sensitive probes of fluctuations. In a recent paper, we argued that thermal fluctuations can play an important role for droplets even at low temperatures where the non-condensed density is much smaller than the condensate density. We used the Hartree-Fock-Bogoliubov theory together with local density approximation for fluctuations to obtain a generalized Gross Pitaevskii (GP) equation and solved it with a Gaussian variational ansatz to show that the transition between the low density and droplet states can be significantly modified by the temperature. In this paper, we first solve the same GP equation numerically with a time splitting spectral method to check the validity of the Gaussian variational ansatz. Our numerical results are in good agreement with the Gaussian ansatz for a large parameter regime and show that the density of the gas is most strongly modified by temperature near the abrupt transition between a pancake shaped cloud and the droplet. For cigar shaped condensates, as in the recent Er experiments, the dependence of the density on temperature remains quite small throughout the smooth transition. We then consider the effect of temperature on the collective oscillation frequencies of the droplet using both a time dependent Gaussian variational ansatz and real time numerical evolution. We find that the oscillation frequencies depend significantly on the temperature close to the transition for the experimentally relevant temperature regime ($\simeq 100$nK).

Probing the circumstellar medium 2.8 Gyr after the big bang: detection of Bowen fluorescence in the Sunburst arc

ABSTRACT We discovered Bowen emission arising from a strongly lensed (i.e. with magnification factor μ > 20) source hosted in the Sunburst arc at z = 2.37. We claim this source is plausibly a transient stellar object and study the unique ultraviolet lines emerging from it. In particular, narrow (σv ≃ 40 km s−1) ionization lines of Fe fluoresce after being exposed to Ly α (1216 Å) radiation that pumps selectively their atomic levels. Data from VLT/MUSE, X-Shooter, and ESPRESSO observations (the latter placed at the focus of the four UTs) at increasing spectral resolution of R = 2500, 11 400, and 70 000, respectively, confirm such fluorescent lines are present since at least 3.3 yr (≃1 yr rest frame). Additional Fe forbidden lines have been detected, while C and Si doublets probe an electron density ne ≳ 106 cm−3. Similarities with the spectral features observed in the circumstellar Weigelt blobs of Eta Carinae probing the circumstellar dense gas condensations in radiation-rich conditions are observed. We discuss the physical origin of the transient event, which remains unclear. We expect such transient events (including also supernova or impostors) will be easily recognized with ELTs thanks to high angular resolution provided by adaptive optics and large collecting area, especially in modest (μ < 3) magnification regime.

Spatial separation of degenerate components of magnon Bose\u2013Einstein condensate by using a local acceleration potential

Bose–Einstein condensation (BEC) of magnons is one of the few macroscopic quantum phenomena observable at room temperature. Due to the competition of the exchange and the magnetic dipole interactions, the minimum-energy magnon state is doubly degenerate and corresponds to two antiparallel non-zero wavevectors. Correspondingly, the room-temperature magnon BEC differs essentially from other condensates, since it takes place simultaneously at ± kmin. The degeneracy of BEC and interaction between its two components have significant impact on condensate properties. Phase locking of the two condensates causes formation of a standing wave of the condensate density and quantized vortices. Additionally, interaction between the two components is believed to be important for stabilization of the condensate with respect to a real-space collapse. Thus, the possibility to create a non-degenerate, single-component condensate is decisive for understanding of underlying physics of magnon BEC. Here, we experimentally demonstrate an approach, which allows one to accomplish this challenging task. We show that this can be achieved by using a separation of the two components of the degenerate condensate in the real space by applying a local pulsed magnetic field, which causes their motion in the opposite directions. Thus, after a certain delay, the two clouds corresponding to different components become well separated in the real space. We find that motion of the clouds can be described well based on the peculiarities of magnon dispersion characteristics. Additionally, we show that, during the motion, the condensate cloud harvests non-condensed magnons, which results in a partial compensation of condensate depletion.

Research of a two-phase steam system during its flow in the pipe and a device for measuring dryness steam

Water steam is widely applied in various fields of industry and heat power engineering. The article shows a wide application of water steam in heat-and-power engineering. In this regard, the issue of preserving and controlling the dryness of steam during its transportation via steam lines remains relevant. Quite detailed theoretical studies of steam parameters during its flow in the pipe have been performed. A comparative analysis of steam velocity and temperature plots depending on certain flow parameters and accepted approximations is performed. The analysis presented that gas-dynamic and thermodynamic processes can be considered approximately. This does not play a fundamental role in the general patterns of dropping liquid. As a result of numerical studies of the steam condensation kinetics, the specific volume and density of drop condensate along the pipe section are determined. The obtained results and the proposed methodological approach for determining the parameters of steam were used in the development and further improvement of the device for measuring the dryness of steam, the original construction of which was proposed earlier by one of the authors. The article presents the functional diagram and layout of the measuring unit of the gauge.

Bose-Bose mixtures in a weak-disorder potential: Fluctuations and superfluidity

We study the properties of a homogeneous dilute Bose-Bose gas in a weak-disorder potential at zero temperature. By using the perturbation theory, we calculate the disorder corrections to the condensate density, the equation of state, the compressibility, and the superfluid density as a function of density, strength of disorder, and miscibility parameter. It is found that the disorder potential may lead to modifying the miscibility-immiscibility condition and a full miscible phase turns out to be impossible in the presence of the disorder. We show that the intriguing interplay of the disorder and intra- and interspecies interactions may strongly influence the localization of each component, the quantum fluctuations, and the compressibility, as well as the superfluidity of the system.

Sc14Co3.10In2.59 – the representative of the Lu14Co3In3 type with the smallest rare earth element

Abstract The scandium-rich phase Sc14Co3.10In2.59 has been synthesized by a direct reaction of the elements in a sealed tantalum ampoule in a high-frequency furnace. Single crystals were obtained by slow cooling of the product. The Sc14Co3.10In2.59 structure was refined from single-crystal X-ray diffractometer data: Lu14Co3In3 type, P42/nmc, a = 889.13(13), c = 2138.7(4) pm, wR2 = 0.0483, 1636 F 2 values, and 64 variables. Sc14Co3.10In2.59 completes the series of the rare earth metal-rich phases RE 14Co3In3. The structure refinement revealed defects on the Co1 site (84.7(5)% occupancy on 8g) and a mixed occupancy of 59.1(7)% In1/40.9(7)% Co3 on the 4c site. The structure is built up by a dense condensation of Co@Sc6 trigonal prisms and In2@InSc11 and In1/Co2@Co2Sc10 icosahedra. An interpenetration of the In2@InSc11 icosahedra leads to dumb-bell formation with an In2–In2 distance of 289 pm. The Sc14Co3.10In2.59 structure is stabilized by substantial Sc–Sc bonding (316–360 pm Sc–Sc).

The anatomy of the peridural membrane of the human spine.

A peridural membranous layer exists between the bony wall of the spinal canal and the dura mater, but reports on the anatomy of this structure have been inconsistent. The objective of this study is to give a precise description of the peridural membrane (PDM) and to define it unambiguously as a distinct and unique anatomical entity. Thirty-four cadaveric sections of human thoraco-lumbar spines were dissected. On gross examination, the PDM appears as a smooth hollow tube that covers the bony wall of the spinal canal. An evagination of this tube into the neural foramen contains the exiting spinal nerve. The entire epidural venous plexus, including its extension into the neural foramina, is contained in the body of the PDM. Histological examination of the PDM shows a variable distribution of veins arteries, lymphatics, and nerves embedded in a continuous sheath of fibrous, areolar, and adipose tissue. The posterior longitudinal ligament may be considered a dense condensation of fibrous tissue within the membrane. Thus, the PDM is a unique, continuous, and complete anatomical structure. In the spinal canal, the PDM is adjacent to the periosteum. In the neural foramen, suprapedicular PDM and pedicular periosteum separate anatomically to form a suprapedicular compartment, bounded anteriorly by the intervertebral disc and posteriorly by the facet joint. Trauma or degeneration of the disc or facet joint may lead to inflammation and pain sensitization of PDM. This protective mechanism may be of considerable importance for the functioning of the spine under conditions of strain.

Self-consistent 3D radiative magnetohydrodynamic simulations of coronal rain formation and evolution

Context. Coronal rain consists of cool and dense plasma condensations formed in coronal loops as a result of thermal instability. Aims. Previous numerical simulations of thermal instability and coronal rain formation have relied on the practice of artificially adding a coronal heating term to the energy equation. To reproduce large-scale characteristics of the corona, the use of more realistic coronal heating prescription is necessary. Methods. We analysed coronal rain formation and evolution in a three-dimensional radiative magnetohydrodynamic simulation spanning from convection zone to corona which is self-consistently heated by magnetic field braiding as a result of convective motions. Results. We investigate the spatial and temporal evolution of energy dissipation along coronal loops which become thermally unstable. Ohmic dissipation in the model leads to the heating events capable of inducing sufficient chromospheric evaporation into the loop to trigger thermal instability and condensation formation. The cooling of the thermally unstable plasma occurs on timescales that are comparable to the duration of the individual impulsive heating events. The impulsive heating has sufficient duration to trigger thermal instability in the loop but does not last long enough to lead to coronal rain limit cycles. We show that condensations can either survive and fall into the chromosphere or be destroyed by strong bursts of Joule heating associated with a magnetic reconnection events. In addition, we find that condensations can also form along open magnetic field lines. Conclusions. We modelled, for the first time, coronal rain formation in a self-consistent 3D radiative magnetohydrodynamic simulation, in which the heating occurs mainly through the braiding and subsequent Ohmic dissipation of the magnetic field. The heating is stratified enough and lasts for long enough along specific field lines to produce the necessary chromospheric evaporation that triggers thermal instability in the corona.

EPLETION DENSITY OF IDEAL GAS BOSE-EINSTEIN CONDENSATE BY TWO PARALLEL PLATES

By means of the second quantization formalism, the condensate density of an infinite Bose gas and finite Bose gas is studied in the broken phase. Our results show that the compactification in one-direction makes the remarkable changes in the condensate density.

Effective field theory of bosons with finite-range interaction in a disordered environment

We investigate the low-temperature properties of a ultracold gas made of bosonic alkali-metal atoms with finite-range interaction under the effect of a disordered environment. The statistical characterization of the disorder is investigated within an effective-field-theory formalism for a generic spatial dimension $d$. Moving to $d=3$, where all the arising divergences are properly regularized, we focus on the depletion of both the condensate and superfluid densities. At zero temperature we obtain meaningful analytical formulas for the condensate fraction and the superfluid fraction which take into account the interplay among scattering length, effective range, and disorder strength.

ЭКСПЕРИМЕНТАЛЬНОЕ ИЗУЧЕНИЕ НЕКОТОРЫХ АСПЕКТОВ ИСПАРЕНИЯ КОНДЕНСАТА «СУХИМ» УГЛЕВОДОРОДНЫМ ГАЗОМ В БОМБЕ PVT

The paper investigates the indicators of the down hole zone stimulation process on gas-condensate well by applying "dry" natural gas in different thermo-baric conditions. The designed experimental investigation has been carried out in pVT bomb for eliminating different unnecessary factors may impact on obtained results. Investigation considered the dependences of the physicochemical and thermodynamic properties of fluids, as well as the rate of evaporated condensate on temperature, condensate density, and the number of contacts. The data obtained provide valuable directions for optimizing well productivity

Density Maximization of One-Step Electrodeposited Copper Nanocones and Dropwise Condensation Heat-Transfer Performance Evaluation.

Currently, it is still a great challenge to obtain copper-based high-efficient dropwise condensation heat transfer (CHT) interfaces via template-free electrodepositing technologies. Here, we report that the density of template-free electrodeposited copper nanocones can maximally reach 1.5 × 106/mm2 by the synergistic control of substrate surface roughness, poly(ethylene glycol) (PEG) molecular weight, and PEG concentration. After thiol modification, the densely packed copper nanocone samples can present low-adhesive superhydrophobicity and condensate microdrop self-jumping function at ambient environment. Condensation heat and mass transfer characterizations show that the CHT coefficient of copper surfaces can maximally enhance 98% for 20 °C vapor and 51% for 40 °C vapor by in situ growth of superhydrophobic densely packed copper nanocones. Although the dropwise condensation mode can change from the jumping mode to the mixed jumping and sweeping mode and the shedding-off mode along with the increase of surface subcooling and vapor temperature, the CHT performance of the nanosample is still superior to that of the contrast flat hydrophobic surface during the whole testing range of surface subcooling. As vapor temperature increases to 80 °C, the CHT performance of the nanosample is inferior to that of the contrast sample. The CHT enhancement under low-temperature vapor should be ascribed to the enhancement of small-drop mass transfer ability caused by low-adhesive superhydrophobicity nature of nanosample surfaces. Their performance degradation mainly results from increased drop-drop drag force along with the increase of surface subcooling and vapor temperature. In sharp contrast, the CHT deterioration under high-temperature vapor should be ascribed to larger drop-surface adhesion and drop-drop drag force. The former is caused by vapor penetration, whereas the latter is caused by the dramatically increased nucleation density and growth rate of condensates. These findings would help design and develop copper-based high-efficiency condensation heat transfer interfaces.

Expansion of the strongly interacting superfluid Fermi gas: Symmetries and self-similar regimes

We consider an expansion of the strongly interacting superfluid Fermi gas in a vacuum, assuming absence of the trapping potential, in the so-called unitary regime (see, for instance, \cite{pitaevskii2008superfluid}) when the chemical potential $\mu \propto \hbar^2n^{2/3}/m$ where $n$ is the density of the Bose-Einstein condensate of Cooper pairs of fermionic atoms. In low temperatures, $T\to 0$, such expansion can be described in the framework of the Gross-Pitaevskii equation (GPE). Because of the chemical potential dependence on the density, $\sim n^{2/3}$, the GPE has additional symmetries, resulting in the existence of the virial theorem \cite% {vlasov1971averaged}, connecting the mean size of the gas cloud and its Hamiltonian. It leads asymptotically at $t\to\infty$ to the gas cloud expansion, linearly growing in time. We study such asymptotics, and reveal the perfect match between the quasi-classical self-similar solution and the asymptotic expansion of the non-interacting gas. This match is governed by the virial theorem, derived through utilizing the Talanov transformation \cite{talanov1970focusing}, which was first obtained for the stationary self-focusing of light in media with a cubic nonlinearity due to the Kerr effect. In the quasi-classical limit, the equations of motion coincide with 3D hydrodynamics for the perfect monoatomic gas with $\gamma=5/3$. Their self-similar solution describes, on the background of the gas expansion, the angular deformities of the gas shape in the framework of the Ermakov--Ray--Reid type system.