Quantum hydrodynamics in dilute-gas Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Engels, Peter
2012-10-01
The peculiar dynamics of superfluids are a fascinating research topic. Since the first generation of a dilute gas Bose-Einstein condensate (BEC) in 1995, quantum degenerate atomic gases have taken the investigation of quantum hydrodynamics to a new level. The atomic physics toolbox has grown tremendously and now provides unique and powerful ways to explore nonlinear quantum systems. As an example, pioneering results have recently revealed that the counterflow between two superfluids can be used as a well controlled tool to access the rich dynamics of vector systems. New structures, such as beating dark-dark solitons which only exist in multicomponent systems and have never been observed before, can now be realized in the lab for the first time. Furthermore, the field of nonlinear quantum hydrodynamics is entering new regimes by exploiting Raman dressing as a tool to directly modify the dispersion relation. This leads to the generation of spin-orbit coupled BECs, artificial gauge fields, etc. that are currently receiving tremendous interest due to their parallels to complex condensed-matter systems. Studies of quantum hydrodynamics help to develop a profound understanding of nonlinear quantum dynamics, which is not only of fundamental interest but also of eminent importance for future technological applications, e.g. in telecommunication applications using optical solitons in fibers. This talk will showcase some ``classic'' hallmark results and highlight recent advances from the forefront of the field.
Photon recoil momentum in a Bose-Einstein condensate of a dilute gas
NASA Astrophysics Data System (ADS)
Avetisyan, Yu A.; Malyshev, V. A.; Trifonov, E. D.
2017-04-01
We develop a ‘minimal’ microscopic model to describe a two-pulse-Ramsey-interferometer-based scheme of measurement of the photon recoil momentum in a Bose-Einstein condensate of a dilute gas (Campbell et al 2005 Phys. Rev. Lett. 94 170403). We exploit the truncated coupled Maxwell-Schrödinger equations to elaborate the problem. Our approach provides a theoretical tool to reproduce essential features of the experimental results. Additionally, we calculate the quantum-mechanical mean value of the recoil momentum and its statistical distribution that provides a detailed information about the recoil event.
Bose-Einstein Condensation in a Dilute Gas; the First 70 Years and Some Recent Experiments
NASA Astrophysics Data System (ADS)
Cornell, E. A.; Wieman, C. E.
Bose-Einstein condensation, or BEC, has a long and rich history dating from the early 1920s. In this article we will trace briefly over this history and some of the developments in physics that made possible our successful pursuit of BEC in a gas. We will then discuss what was involved in this quest. In this discussion we will go beyond the usual technical description to try and address certain questions that we now hear frequently, but are not covered in our past research papers. These are questions along the lines of ``How did you get the idea and decide to pursue it? Did you know it was going to work? How long did it take you and why?'' We will review some of our favorites from among the experiments we have carried out with BEC. There will then be a brief encore on why we are optimistic that BEC can be created with nearly any species of magnetically trappable atom. Throughout this article we will try to explain what makes BEC in a dilute gas so interesting, unique, and experimentally challenging.
Bose-Einstein Condensation in a Dilute Gas:. the First 70 Years and Some Recent Experiments
NASA Astrophysics Data System (ADS)
Cornell, E. A.; Wieman, C. E.
2003-04-01
Bose-Einstein condensation, or BEC, has a long and rich history dating from the early 1920s. In this article we will trace briefly over this history and some of the developments in physics that made possible our successful pursuit of BEC in a gas. We will then discuss what was involved in this quest. In this discussion we will go beyond the usual technical description to try and address certain questions that we now hear frequently, but are not covered in our past research papers. These are questions along the lines of "How did you get the idea and decide to pursue it? Did you know it was going to work? How long did it take you and why?" We will review some of our favorites from among the experiments we have carried out with BEC. There will then be a brief encore on why we are optimistic that BEC can be created with nearly any species of magnetically trappable atom. Throughout this article we will try to explain what makes BEC in a dilute gas so interesting, unique, and experimentally challenging.
NASA Astrophysics Data System (ADS)
Krieg, Jan; Strassel, Dominik; Streib, Simon; Eggert, Sebastian; Kopietz, Peter
2017-01-01
We use the functional renormalization group (FRG) to derive analytical expressions for thermodynamic observables (density, pressure, entropy, and compressibility) as well as for single-particle properties (wave-function renormalization and effective mass) of interacting bosons in two dimensions as a function of temperature T and chemical potential μ . We focus on the quantum disordered and the quantum critical regime close to the dilute Bose gas quantum critical point. Our approach is based on a truncated vertex expansion of the hierarchy of FRG flow equations and the decoupling of the two-body contact interaction in the particle-particle channel using a suitable Hubbard-Stratonovich transformation. Our analytic FRG results extend previous analytical renormalization-group calculations for thermodynamic observables at μ =0 to finite values of μ . To confirm the validity of our FRG approach, we have also performed quantum Monte Carlo simulations to obtain the magnetization, susceptibility, and correlation length of the two-dimensional spin-1 /2 quantum X Y model with coupling J in a regime where its quantum critical behavior is controlled by the dilute Bose gas quantum critical point. We find that our analytical results describe the Monte Carlo data for μ ≤0 rather accurately up to relatively high temperatures T ≲0.1 J .
Ultra-cold dilute gas Bose-Fermi mixture with ^87Rb and ^40K
NASA Astrophysics Data System (ADS)
Goldwin, J.; Olsen, M. L.; Inouye, S.; Jin, D. S.
2003-05-01
Sympathetic cooling experiments with Bose-Fermi mixtures offer a way to cool Fermi gases to quantum degeneracy with relatively little loss in atom number, as well as offering interesting new systems for study with the control and precision typical of atomic physics experiments. Here we report on the sympathetic cooling of fermionic ^40K with bosonic ^87Rb. We first trap and cool ^87Rb atoms in a two-species MOT together with ^40K. After loading into a purely magnetic quadrupole configuration trap, the gas is transferred mechanically nearly a meter to a Ioffe-Pritchard type magnetic trap in an ultra-high vacuum cell. radio-frequency induced evaporation of the ^87Rb atoms results in pure Bose-Einstein condensates of ˜ 2× 10^5 atoms. In the process ^40K atoms are cooled by virtue of thermal contact with the ^87Rb reservoir resulting in cooling of ^40K, with ˜ 1 × 10^4 atoms at temperatures below 100 nK. We present results from the experiment demonstrating the efficiency of the cooling, and describe ongoing investigations into the limits of the cooling and the strong inter-species interactions in the mixture. Finally, future directions for the experiment are discussed.
NASA Astrophysics Data System (ADS)
Boudjemâa, Abdelâali; Guebli, Nadia
2017-10-01
Using the time-dependent Hartree–Fock–Bogoliubov approach, where the condensate is coupled with the thermal cloud and the anomalous density, we study the equilibrium and the dynamical properties of three-dimensional quantum-degenerate Bose gas at finite temperature. Effects of the anomalous correlations on the condensed fraction and the critical temperature are discussed. In uniform Bose gas, useful expressions for the Bogoliubov excitations spectrum, the first and second sound, the condensate depletion and the superfluid fraction are derived. Our results are tested by comparing the findings computed by quantum Monte Carlo simulations. We present also a systematic investigation of the collective modes of a Bose condensate confined in an external trap. Our predictions are in qualitative agreement with previous experimental and theoretical results. We show in particular that our theory is capable of explaining the so-called anomalous behavior of the m=0 mode.
A new apparatus for studies of quantized vortex dynamics in dilute-gas Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Newman, Zachary L.
The presence of quantized vortices and a high level of control over trap geometries and other system parameters make dilute-gas Bose-Einstein condensates (BECs) a natural environment for studies of vortex dynamics and quantum turbulence in superfluids, primary interests of the BEC group at the University of Arizona. Such research may lead to deeper understanding of the nature of quantum fluid dynamics and far-from-equilbrium phenomena. Despite the importance of quantized vortex dynamics in the fields of superfluidity, superconductivity and quantum turbulence, direct imaging of vortices in trapped BECs remains a significant technical challenge. This is primarily due to the small size of the vortex core in a trapped gas, which is typically a few hundred nanometers in diameter. In this dissertation I present the design and construction of a new 87Rb BEC apparatus with the goal of studying vortex dynamics in trapped BECs. The heart of the apparatus is a compact vacuum chamber with a custom, all-glass science cell designed to accommodate the use of commercial high-numerical-aperture microscope objectives for in situ imaging of vortices. The designs for the new system are, in part, based on prior work in our group on in situ imaging of vortices. Here I review aspects of our prior work and discuss some of the successes and limitations that are relevant to the new apparatus. The bulk of the thesis is used to described the major subsystems of the new apparatus which include the vacuum chamber, the laser systems, the magnetic transfer system and the final magnetic trap for the atoms. Finally, I demonstrate the creation of a BEC of ˜ 2 x 106 87Rb atoms in our new system and show that the BEC can be transferred into a weak, spherical, magnetic trap with a well defined magnetic field axis that may be useful for future vortex imaging studies.
Cornell, Eric A; Wieman, Carl E
2002-06-17
Bose-Einstein condensates of dilute gases offer a rich field to study fundamental quantum-mechanical processes, manipulation of the speed at which light propogates, observation of atomic pair-formation and superfluidity, or even simulating white dwarf stars. Still more radical applications are on the horizon. However, their initial creation was a masterpiece of experimental physics. After an initial process of laser cooling (which itself won its developers the 1997 Nobel Prize), atoms in a magnetic-optical trap must be safely transferred into a purely magnetic trap, where the condensation process begins at 170 nK and 20 nK a pure condensate of 2000 atoms could be created. More astonishingly, Wieman and Cornell showed these low temperatures could be achieved in "bench scale" equipment rather than the massive pieces normally demanded by cryoscience. For their 1995 discovery of this new state of matter, they were awarded the 2001 Nobel Prize in Physics.
Belyaev, S. T.
2016-06-15
We consider excitations that exist, in addition to phonons, in the ideal Bose gas at zero temperature. These excitations are vortex rings whose energy spectrum is similar to the roton one in liquid helium.
Decay of hydrodynamic modes in dilute Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Gust, Erich; Reichl, Linda
2015-03-01
We present the results of Bogoliubov mean field theory applied to the hydrodynamic modes in a dilute Bose-Einstein condensate. The condensate has six hydrodynamic modes, two of which are decaying shear modes related to the viscosity, and two pairs pairs of sound modes which undergo an avoided crossing as the equilibrium temperature is varied. The two pairs of sound modes decay at very different rates, except in the neighborhood of the avoided crossing, where the identity of the longest-lived mode switches. The predicted speed and lifetime of the longest-lived sound mode are consistent with recent experimental observations on sound in an 87Rb Bose-Einstein condensate. The strong depedence of the decay rates on temperature implies a possible new method for determining the temperature of Bose-Einstein condensates. The authors wish to thank the Robert A. Welch Foundation Grant No. F-1051 for support of this work.
Bose-Einstein Condensation in the Relativistic Ideal Bose Gas
Grether, M.; Llano, M. de; Baker, George A. Jr.
2007-11-16
The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state.
Bose-Einstein condensation in the relativistic ideal Bose gas.
Grether, M; de Llano, M; Baker, George A
2007-11-16
The Bose-Einstein condensation (BEC) critical temperature in a relativistic ideal Bose gas of identical bosons, with and without the antibosons expected to be pair-produced abundantly at sufficiently hot temperatures, is exactly calculated for all boson number densities, all boson point rest masses, and all temperatures. The Helmholtz free energy at the critical BEC temperature is lower with antibosons, thus implying that omitting antibosons always leads to the computation of a metastable state.
Vortex Pump for Dilute Bose-Einstein Condensates
Moettoenen, Mikko; Pietilae, Ville; Virtanen, Sami M. M.
2007-12-21
The formation of vortices by topological phase engineering has been realized experimentally to create the first two- and four-quantum vortices in dilute atomic Bose-Einstein condensates. We consider a similar system, but in addition to the Ioffe-Pritchard magnetic trap we employ an additional hexapole field. By controlling cyclically the strengths of these magnetic fields, we show that a fixed amount of vorticity can be added to the condensate in each cycle. In an adiabatic operation of this vortex pump, the appearance of vortices into the condensate is interpreted as the accumulation of a local Berry phase. Our design can be used as an experimentally realizable vortex source for possible vortex-based applications of dilute Bose-Einstein condensates.
Vortex pump for dilute bose-einstein condensates.
Möttönen, Mikko; Pietilä, Ville; Virtanen, Sami M M
2007-12-21
The formation of vortices by topological phase engineering has been realized experimentally to create the first two- and four-quantum vortices in dilute atomic Bose-Einstein condensates. We consider a similar system, but in addition to the Ioffe-Pritchard magnetic trap we employ an additional hexapole field. By controlling cyclically the strengths of these magnetic fields, we show that a fixed amount of vorticity can be added to the condensate in each cycle. In an adiabatic operation of this vortex pump, the appearance of vortices into the condensate is interpreted as the accumulation of a local Berry phase. Our design can be used as an experimentally realizable vortex source for possible vortex-based applications of dilute Bose-Einstein condensates.
Condensate statistics in interacting and ideal dilute bose gases
Kocharovsky; Kocharovsky; Scully
2000-03-13
We obtain analytical formulas for the statistics, in particular, for the characteristic function and all cumulants, of the Bose-Einstein condensate in dilute weakly interacting and ideal equilibrium gases in the canonical ensemble via the particle-number-conserving operator formalism of Girardeau and Arnowitt. We prove that the ground-state occupation statistics is not Gaussian even in the thermodynamic limit. We calculate the effect of Bogoliubov coupling on suppression of ground-state occupation fluctuations and show that they are governed by a pair-correlation, squeezing mechanism.
Bose-Einstein condensation in dilute atomic gases
NASA Astrophysics Data System (ADS)
Arlt, J.; Bongs, K.; Sengstock, K.; Ertmer, W.
2002-02-01
Bose-Einstein condensation is one of the most curious and fascinating phenomena in physics. It lies at the heart of such intriguing processes as superfluidity and superconductivity. However, in most cases, only a small part of the sample is Bose-condensed and strong interactions are present. A weakly interacting, pure Bose-Einstein condensate (BEC) has therefore been called the "holy grail of atomic physics". In 1995 this grail was found by producing almost pure BECs in dilute atomic gases. We review the experimental development that led to the realization of BEC in these systems and explain how BECs are now routinely produced in about 25 laboratories worldwide. The tremendous experimental progress of the past few years is outlined and a number of recent experiments show the current status of the field. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s00114-001-0277-8.
Vortices in a highly rotating Bose condensed gas
NASA Astrophysics Data System (ADS)
Coddington, I. R.
Superfluids, with their dissipationless flow and exotic topologies, have puzzled researchers in diverse fields of physics for almost a century. One of the hallmark features of superfluids is their response to rotation, which requires the fluid to be pierced by an array quantized singularities or vortices. Over the past few years, vortices and the lattices they organize into have become one of the major fields of experimental research with dilute gas Bose-Einstein condensates. This thesis explores the physics of vortices and vortex lattices in the dilute gas Bose-Einstein condensate while drawing connections to other superfluid systems. In addition to characterizing several equilibrium vortex effects, this work also studies several excitations. By removing atoms from the rotating condensate with a tightly focused, resonant laser, the density can be locally suppressed, creating aggregate vortices containing many units of circulation. These so called "giant vortices" offer insight into the dynamical stability of density defects in this system. Using similar techniques we can excite and directly image Tkachenko waves in the vortex. These low frequency modes are a consequence of the small but nonvanishing elastic shear modulus of the vortex-filled superfluid. Finally, by working at extremely high rotations we can create a Bose-Einstein condensates in the lowest Landau level. In this regime, which requires rotation rates greater than 99% of the centrifugal limit for a harmonically trapped gas, we are able to observe several expected and unexpected shifts in the physical properties of the condensate. In conclusion the dilute gas Bose-Einstein condensates offers a rich system in which to study vortex physics, and explore dynamical effects common to all rotating superfluids.
Numerical simulation of polariton Bose gas thermalization
NASA Astrophysics Data System (ADS)
Kartsev, P. F.; Kuznetsov, I. O.
2016-08-01
In this work, we present the numerical simulation of the process a Bose gas thermalization and the formation of the condensate. Our approach is based on kinetic equations and “Fermi's golden rule” in the incoherent approximation. Direct summation of terms is performed using GPGPU OpenCL parallel code using AMD Radeon HD 7970.
Canonical Bose gas simulations with stochastic gauges.
Drummond, P D; Deuar, P; Kheruntsyan, K V
2004-01-30
A technique to simulate the grand canonical ensembles of interacting Bose gases is presented. Results are generated for many temperatures by averaging over energy-weighted stochastic paths, each corresponding to a solution of coupled Gross-Pitaevskii equations with phase noise. The stochastic gauge method used relies on an off-diagonal coherent-state expansion, thus taking into account all quantum correlations. As an example, the second-order spatial correlation function and momentum distribution for an interacting 1D Bose gas are calculated.
Excitation picture of an interacting Bose gas
Kira, M.
2014-12-15
Atomic Bose–Einstein condensates (BECs) can be viewed as macroscopic objects where atoms form correlated atom clusters to all orders. Therefore, the presence of a BEC makes the direct use of the cluster-expansion approach–lucrative e.g. in semiconductor quantum optics–inefficient when solving the many-body kinetics of a strongly interacting Bose. An excitation picture is introduced with a nonunitary transformation that describes the system in terms of atom clusters within the normal component alone. The nontrivial properties of this transformation are systematically studied, which yields a cluster-expansion friendly formalism for a strongly interacting Bose gas. Its connections and corrections to the standard Hartree–Fock–Bogoliubov approach are discussed and the role of the order parameter and the Bogoliubov excitations are identified. The resulting interaction effects are shown to visibly modify number fluctuations of the BEC. Even when the BEC has a nearly perfect second-order coherence, the BEC number fluctuations can still resolve interaction-generated non-Poissonian fluctuations. - Highlights: • Excitation picture expresses interacting Bose gas with few atom clusters. • Semiconductor and BEC many-body investigations are connected with cluster expansion. • Quantum statistics of BEC is identified in terms of atom clusters. • BEC number fluctuations show extreme sensitivity to many-body correlations. • Cluster-expansion friendly framework is established for an interacting Bose gas.
Surface Region of Superfluid Helium as an Inhomogeneous Bose-Condensed Gas
NASA Astrophysics Data System (ADS)
Griffin, A.; Stringari, S.
1996-01-01
We present arguments that the low density surface region of self-bounded superfluid 4He systems is an inhomogeneous dilute Bose gas, with almost all of the atoms occupying the same single-particle state at T = 0. Numerical evidence for this complete Bose-Einstein condensation was first given by the many-body variational calculations of 4He droplets by Lewart, Pandharipande, and Pieper in 1988 [Phys. Rev. B 37, 4950 (1988)]. We show that the low density surface region can be treated rigorously using a generalized Gross-Pitaevskii equation for the Bose order parameter.
Stability of a unitary Bose gas.
Fletcher, Richard J; Gaunt, Alexander L; Navon, Nir; Smith, Robert P; Hadzibabic, Zoran
2013-09-20
We study the stability of a thermal (39)K Bose gas across a broad Feshbach resonance, focusing on the unitary regime, where the scattering length a exceeds the thermal wavelength λ. We measure the general scaling laws relating the particle-loss and heating rates to the temperature, scattering length, and atom number. Both at unitarity and for positive a<λ we find agreement with three-body theory. However, for a<0 and away from unitarity, we observe significant four-body decay. At unitarity, the three-body loss coefficient, L(3) proportional λ(4), is 3 times lower than the universal theoretical upper bound. This reduction is a consequence of species-specific Efimov physics and makes (39)K particularly promising for studies of many-body physics in a unitary Bose gas.
Dilute Bose gases with large scattering length using Bijl-Jastrow wavefunctions
NASA Astrophysics Data System (ADS)
Sykes, Andrew; Corson, John; Sze, Michelle; Bohn, John
2014-05-01
The Bijl-Jastrow wavefunction, which explicitly includes two-body correlations, has been reasonably successful in explaining macroscopic properties of liquid Helium at low temperatures. We apply the same techniques to understand dilute Bose gases with an effective zero-range interaction (employing the Bethe-Peierls boundary condition rather than including an explicit two-body potential). We discuss the renormalisation issues which arise as a result of this diverging zero-range boundary condition. We calculate observables such as the ground state energy, the condensate fraction, and Tan's contact in the system, with particularly interest in the regime where the gas parameter na3 is appreciable (n being the number density and a the scattering length). Finally, we will discuss possible extensions and avenues for further research.
Localization of weakly interacting Bose gas in quasiperiodic potential
NASA Astrophysics Data System (ADS)
Ray, Sayak; Pandey, Mohit; Ghosh, Anandamohan; Sinha, Subhasis
2016-01-01
We study the localization properties of weakly interacting Bose gas in a quasiperiodic potential. The Hamiltonian of the non-interacting system reduces to the well known ‘Aubry-André model’, which shows the localization transition at a critical strength of the potential. In the presence of repulsive interaction we observe multi-site localization and obtain a phase diagram of the dilute Bose gas by computing the superfluid fraction and the inverse participation ratio. We construct a low-dimensional classical Hamiltonian map and show that the onset of localization is manifested by the chaotic phase space dynamics. The level spacing statistics also identify the transition to localized states resembling a Poisson distribution that are ubiquitous for both non-interacting and interacting systems. We also study the quantum fluctuations within the Bogoliubov approximation and compute the quasiparticle energy spectrum. Enhanced quantum fluctuation and multi-site localization phenomenon of non-condensate density are observed above the critical coupling of the potential. We briefly discuss the effect of the trapping potential on the localization of matter wave.
Fast and accurate calculation of dilute quantum gas using Uehling-Uhlenbeck model equation
NASA Astrophysics Data System (ADS)
Yano, Ryosuke
2017-02-01
The Uehling-Uhlenbeck (U-U) model equation is studied for the fast and accurate calculation of a dilute quantum gas. In particular, the direct simulation Monte Carlo (DSMC) method is used to solve the U-U model equation. DSMC analysis based on the U-U model equation is expected to enable the thermalization to be accurately obtained using a small number of sample particles and the dilute quantum gas dynamics to be calculated in a practical time. Finally, the applicability of DSMC analysis based on the U-U model equation to the fast and accurate calculation of a dilute quantum gas is confirmed by calculating the viscosity coefficient of a Bose gas on the basis of the Green-Kubo expression and the shock layer of a dilute Bose gas around a cylinder.
Observation of quantum equilibration in dilute Bose gases
NASA Astrophysics Data System (ADS)
Niu, Linxiao; Tang, Pengju; Yang, Baoguo; Chen, Xuzong; Wu, Biao; Zhou, Xiaoji
2016-12-01
We investigate experimentally the dynamical relaxation of a nonintegrable quantum many-body system to its equilibrium state. A Bose-Einstein condensate is loaded into the first excited band of an optical lattice and let to evolve up to a few hundreds of milliseconds. Signs of quantum equilibration are observed. There is a period of time, roughly 40 ms long, during which both the aspect ratio of the cloud and its momentum distribution remain constant. In particular, the momentum distribution has a flat top and is not a Gaussian thermal distribution. After this period, the cloud becomes classical as its momentum distribution becomes Gaussian.
1/N-expansion for the critical temperature of the Bose gas
NASA Astrophysics Data System (ADS)
Hryhorchak, O.; Pastukhov, V.
2017-06-01
We revised the large-N expansion for a three-dimensional Bose system with short-range repulsion in normal phase. Particularly, for the model potential that is characterised only by the s-wave scattering length a the full numerical calculations of the critical temperature in the 1/N -approximation as a function of the gas parameter an1/3 are performed. Additionally to the well-known result in the dilute limit we estimated analytically the leading-order strong-coupling behavior of the Bose-Einstein condensation transition temperature. It is shown that the critical temperature shift of the non-ideal Bose gas grows at small an1/3 , reaches some maximal value and then falls down becoming negative.
Number-conserving master equation theory for a dilute Bose-Einstein condensate
Schelle, Alexej; Wellens, Thomas; Buchleitner, Andreas; Delande, Dominique
2011-01-15
We describe the transition of N weakly interacting atoms into a Bose-Einstein condensate within a number-conserving quantum master equation theory. Based on the separation of time scales for condensate formation and noncondensate thermalization, we derive a master equation for the condensate subsystem in the presence of the noncondensate environment under the inclusion of all two-body interaction processes. We numerically monitor the condensate particle number distribution during condensate formation, and derive a condition under which the unique equilibrium steady state of a dilute, weakly interacting Bose-Einstein condensate is given by a Gibbs-Boltzmann thermal state of N noninteracting atoms.
Calorimetry of a Bose-Einstein-condensed photon gas.
Damm, Tobias; Schmitt, Julian; Liang, Qi; Dung, David; Vewinger, Frank; Weitz, Martin; Klaers, Jan
2016-04-19
Phase transitions, as the condensation of a gas to a liquid, are often revealed by a discontinuous behaviour of thermodynamic quantities. For liquid helium, for example, a divergence of the specific heat signals the transition from the normal fluid to the superfluid state. Apart from liquid helium, determining the specific heat of a Bose gas has proven to be a challenging task, for example, for ultracold atomic Bose gases. Here we examine the thermodynamic behaviour of a trapped two-dimensional photon gas, a system that allows us to spectroscopically determine the specific heat and the entropy of a nearly ideal Bose gas from the classical high temperature to the Bose-condensed quantum regime. The critical behaviour at the phase transition is clearly revealed by a cusp singularity of the specific heat. Regarded as a test of quantum statistical mechanics, our results demonstrate a quantitative agreement with its predictions at the microscopic level.
Calorimetry of a Bose-Einstein-condensed photon gas
NASA Astrophysics Data System (ADS)
Damm, Tobias; Schmitt, Julian; Liang, Qi; Dung, David; Vewinger, Frank; Weitz, Martin; Klaers, Jan
2016-04-01
Phase transitions, as the condensation of a gas to a liquid, are often revealed by a discontinuous behaviour of thermodynamic quantities. For liquid helium, for example, a divergence of the specific heat signals the transition from the normal fluid to the superfluid state. Apart from liquid helium, determining the specific heat of a Bose gas has proven to be a challenging task, for example, for ultracold atomic Bose gases. Here we examine the thermodynamic behaviour of a trapped two-dimensional photon gas, a system that allows us to spectroscopically determine the specific heat and the entropy of a nearly ideal Bose gas from the classical high temperature to the Bose-condensed quantum regime. The critical behaviour at the phase transition is clearly revealed by a cusp singularity of the specific heat. Regarded as a test of quantum statistical mechanics, our results demonstrate a quantitative agreement with its predictions at the microscopic level.
Theory of a Nearly Two-Dimensional Dipolar Bose Gas
2016-05-11
A TRIDENT SCHOLAR PROJECT REPORT NO. 453 Theory of a Nearly Two-Dimensional Dipolar Bose Gas by Midshipman 1/C Michael A. Woulfe...approved for public release and sale; its distribution is unlimited. U.S.N.A. --- Trident Scholar project report; no. 453 (2016) THEORY OF A...YYYY) 05-11-2016 2. REPORT TYPE 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE Theory of a Nearly Two-Dimensional Dipolar Bose Gas 5a
Behavior of trapped ultracold dilute Bose gases at large scattering length near a Feshbach resonance
NASA Astrophysics Data System (ADS)
Lekala, M. L.; Chakrabarti, B.; Rampho, G. J.; Das, T. K.; Sofianos, S. A.; Adam, R. M.
2014-02-01
We calculate the ground-state energy and the collective excitation frequency of trapped bosons at large scattering length interacting via the realistic two-body van der Waals potential. Our many-body method keeps two-body correlations produced by all interacting pairs. When the scattering length is small compared to the trap size and the number of bosons in the trap is of the order of a few thousands, the mean-field results are in good agreement with the many-body results. However for large particle numbers, even when the condensate is sufficiently dilute, the interatomic correlation comes into the picture. When the scattering length is quite large near the Feshbach resonance, the Bose gas becomes highly correlated. The many-body results are close to the Gross-Pitaevskii results for a small number of bosons, however, large deviations are noted in the large particle limit. We also calculate the lowest collective excitation and the interaction energy for large scattering lengths. The monopole excitation frequency exhibits a pronounced dependence on the scattering length. We also observe a universal behavior for the interaction energy at the limit of large scattering length.
Degenerate Bose gas without anomalous averages
NASA Astrophysics Data System (ADS)
Bobrov, V. B.; Trigger, S. A.; Schram, P. P.
2016-11-01
Theory of a weakly non-ideal Bose gas in the canonical ensemble is developed without assumption of the C-number representation of the creation and annihilation operators with zero momentum. Instead of this assumption, we use the assumption on the C-number nature of the density operator N0 = a† 0a0 with zero momentum. It is shown that the pole of the “density-density” Green function (DDGF), as well as the pole of the single-particle Green function (SPGF), exactly coincide with the Bogoliubov phonon-roton spectrum of excitations for both assumptions. This spectrum, as is known confirmed by many neutron and x-ray experimental measurements of the dynamic structure factor in He II, is straightly related to the DDGF. At the same time, we show that in the other case under consideration, when neither N0 nor a† 0 and a0 are C-numbers, a gap can exist in SPGF. This gap in SPGF excitations is straightly related to the density of particles in the “condensate”. Therefore, the spectra of excitations for the DDGF and SPGF in the last case under consideration are different, in contrast to the Bogoliubov-type theory where these spectra are identical.
Nonequilibrium States of a Quenched Bose Gas
NASA Astrophysics Data System (ADS)
Ling, Hong; Kain, Ben
2014-05-01
Yin and Radzihovsky [Phys. Rev. A 88, 063611 (2014)] recently developed a self-consistent extension of a Bogoliubov theory, in which the condensate number density, nc, is treated as a mean field that changes with time in order to analyze a JILA experiment by Makotyn et al. [Nature Physics doi:10.1038/nphys2850 (2014)] on a 85Rb Bose gas following a deep quench to a large scattering length. We apply this theory to construct a set of closed equations that highlight the role of dnc/dt, which is to induce an effective interaction between quasiparticles. We show analytically that such a system supports a steady state characterized by a constant condensate density and a steady but periodically changing momentum distribution, whose time average is described exactly by the generalized Gibbs ensemble. We discuss how the dnc/dt-induced effective interaction, which cannot be ignored on the grounds of the adiabatic approximation for modes near the gapless Goldstone mode, can affect experimentally measurable quantities such as Tan's contact. This work is supported in part by the US Army Research Office under Grant No. W911NF-10-1-0096 and in part by the US National Science Foundation under Grant No. PHY11-25915.
Hydrodynamic modes of a one-dimensional trapped Bose gas
Fuchs, J.N.; Leyronas, X.; Combescot, R.
2003-10-01
We consider two regimes where a trapped Bose gas behaves as a one-dimensional (1D) system. In the first one the Bose gas is microscopically described by 3D mean-field theory, but the trap is so elongated that it behaves as a 1D gas with respect to low-frequency collective modes. In the second regime we assume that the 1D gas is truly 1D and that it is properly described by the Lieb-Liniger model. In both regimes we find the frequency of the lowest compressional mode by solving the hydrodynamic equations. This is done by making use of a method which allows us to find analytical or quasianalytical solutions of these equations for a large class of models approaching very closely the actual equation of state of the Bose gas. We find an excellent agreement with the recent results of Menotti and Stringari obtained from a sum-rule approach.
NASA Astrophysics Data System (ADS)
Chomaz, L.; Baier, S.; Petter, D.; Mark, M. J.; Wächtler, F.; Santos, L.; Ferlaino, F.
2016-10-01
In a joint experimental and theoretical effort, we report on the formation of a macrodroplet state in an ultracold bosonic gas of erbium atoms with strong dipolar interactions. By precise tuning of the s -wave scattering length below the so-called dipolar length, we observe a smooth crossover of the ground state from a dilute Bose-Einstein condensate to a dense macrodroplet state of more than 2 ×104 atoms . Based on the study of collective excitations and loss features, we prove that quantum fluctuations stabilize the ultracold gas far beyond the instability threshold imposed by mean-field interactions. Finally, we perform expansion measurements, showing that although self-bound solutions are prevented by losses, the interplay between quantum stabilization and losses results in a minimal time-of-flight expansion velocity at a finite scattering length.
First and second sounds in a degenerate Bose gas
NASA Astrophysics Data System (ADS)
Dmytruk, I.; Svidzynskiy, A.; Shygorin, P.
2017-06-01
In this work the propagation of sound waves in a degenerate quantum gas is considered. We modify the Wang Chang and Uhlenbeck method for description of the sounds in a Maxwell gas for the case of a degenerate quantum gas. Using this approach, we constructed a dispersion relation for sound waves in a condensed Bose gas at finite temperatures, and calculate the velocities of first and second sounds in the first approximation. The possibility of the theoretical investigation for sound damping is discussed.
Splitting Times of Doubly Quantized Vortices in Dilute Bose-Einstein Condensates
Huhtamaeki, J. A. M.; Pietilae, V.; Virtanen, S. M. M.; Moettoenen, M.; Isoshima, T.
2006-09-15
Recently, the splitting of a topologically created doubly quantized vortex into two singly quantized vortices was experimentally investigated in dilute atomic cigar-shaped Bose-Einstein condensates [Y. Shin et al., Phys. Rev. Lett. 93, 160406 (2004)]. In particular, the dependency of the splitting time on the peak particle density was studied. We present results of theoretical simulations which closely mimic the experimental setup. We show that the combination of gravitational sag and time dependency of the trapping potential alone suffices to split the doubly quantized vortex in time scales which are in good agreement with the experiments.
Size and dynamics of vortex dipoles in dilute Bose-Einstein condensates
Kuopanportti, Pekko; Huhtamaeki, Jukka A. M.
2011-01-15
Recently, Freilich et al. [Science 329, 1182 (2010)] experimentally discovered stationary states of vortex dipoles, pairs of vortices of opposite circulation, in dilute Bose-Einstein condensates. To explain their observations, we perform simulations based on the Gross-Pitaevskii equation and obtain excellent quantitative agreement on the size of the stationary dipole. We also investigate how their imaging method, in which atoms are repeatedly extracted from a single condensate, affects the vortex dynamics. We find that it mainly induces isotropic size oscillations of the condensate without otherwise disturbing the vortex trajectories. Thus, the imaging technique appears to be a promising tool for studying real-time superfluid dynamics.
Anisotropic superfluidity in a dipolar Bose gas
Ticknor, Christopher; Wilson, Ryan M; Bohn, John L
2010-11-04
A quintessential feature of superfluidity is the ability to support dissipationless flow, for example, when an object moves through a superfluid and experiences no drag. This, however, only occurs when the object is moving below a certain critical velocity; when it exceeds this critical velocity it dissipates energy into excitations of the superfluid, resulting in a net drag force on the object and the breakdown of superfluid flow. In many superfluids, such as dilute Bose-Einstein condensates (BECs) of atoms with contact interactions, this critical velocity is simply the speed of sound in the system, where the speed of sound is set by the density and the s-wave scattering length of the atoms. However, for other superfluids, such as liquid {sup 4}He, this is not the case. In {sup 4}He, the critical velocity is set by a roton mode, corresponding to a peak in the static structure factor of the system at some finite, non-zero momentum, with a characteristic velocity that is considerably less than the speed of sound in the liquid. This feature has been verified experimentally via measurements of ion-drift velocity in the fluid, thereby providing insight into the detailed structure of the system. Interestingly, a roton-like feature was predicted to exist in the dispersion relation of a quasi-two-dimensional (q2D) dipolar BEC (DBEC) [16], or a BEC with dipole-dipole interactions. However, unlike the dispersion of {sup 4}He, the disperSion of a DBEC is highly tunable as a function of the condensate density or dipole-dipole interaction (ddi) strength. Additionally, the DBEC is set apart from liquid {sup 4}He in that its interactions depend on how the dipoles are oriented in space. Thus, the DBEC provides an ideal system to study the effects that anisotropies have on the bulk properties of a superfluid, such as the critical velocity. Here we consider a DBEC in a quasi-two-dimensional (q2D) geometry and allow for the dipoles to be polarized at a nonzero angle into the plane
Esteve, J; Trebbia, J-B; Schumm, T; Aspect, A; Westbrook, C I; Bouchoule, I
2006-04-07
We report in situ measurements of density fluctuations in a quasi-one-dimensional 87Rb Bose gas at thermal equilibrium in an elongated harmonic trap. We observe an excess of fluctuations compared to the shot-noise level expected for uncorrelated atoms. At low atomic density, the measured excess is in good agreement with the expected "bunching" for an ideal Bose gas. At high density, the measured fluctuations are strongly reduced compared to the ideal gas case. We attribute this reduction to repulsive interatomic interactions. The data are compared with a calculation for an interacting Bose gas in the quasicondensate regime.
Anisotropic Expansion of a Thermal Dipolar Bose Gas.
Tang, Y; Sykes, A G; Burdick, N Q; DiSciacca, J M; Petrov, D S; Lev, B L
2016-10-07
We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the postexpansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases. Furthermore, we present a simple method to determine scattering lengths in dipolar gases, including near a Feshbach resonance, through observation of thermal gas expansion.
Anisotropic Expansion of a Thermal Dipolar Bose Gas
NASA Astrophysics Data System (ADS)
Tang, Y.; Sykes, A. G.; Burdick, N. Q.; DiSciacca, J. M.; Petrov, D. S.; Lev, B. L.
2016-10-01
We report on the anisotropic expansion of ultracold bosonic dysprosium gases at temperatures above quantum degeneracy and develop a quantitative theory to describe this behavior. The theory expresses the postexpansion aspect ratio in terms of temperature and microscopic collisional properties by incorporating Hartree-Fock mean-field interactions, hydrodynamic effects, and Bose-enhancement factors. Our results extend the utility of expansion imaging by providing accurate thermometry for dipolar thermal Bose gases. Furthermore, we present a simple method to determine scattering lengths in dipolar gases, including near a Feshbach resonance, through observation of thermal gas expansion.
Percolation analysis of a disordered spinor Bose gas
NASA Astrophysics Data System (ADS)
Nabi, Sk Noor; Basu, Saurabh
2016-06-01
We study the effects of an on-site disorder potential in a gas of spinor (spin-1) ultracold atoms loaded in an optical lattice corresponding to both ferromagnetic and antiferromagnetic spin-dependent interactions. Starting with a disordered spinor Bose-Hubbard model (SBHM) on a two-dimensional square lattice, we observe the appearance of a Bose glass phase using the fraction of the lattice sites having finite superfluid order parameter and non integer local densities as an indicator. A precise distinction between three different types of phases namely, superfluid, Mott insulator and Bose glass is done via a percolation analysis thereby demonstrating that a reliable enumeration of phases is possible at particular values of the parameters of the SBHM. Finally, we present the phase diagram based on the above information for both antiferromagnetic and ferromagnetic interactions.
Nonuniversal Equation of State of the Two-Dimensional Bose Gas.
Salasnich, L
2017-03-31
For a dilute two-dimensional Bose gas the universal equation of state has a logarithmic dependence on the s-wave scattering length. Here we derive nonuniversal corrections to this equation of state, taking account of finite-range effects of the interatomic potential. Our beyond-mean-field analytical results are obtained performing dimensional regularization of divergent zero-point quantum fluctuations within the finite-temperature formalism of functional integration. In particular, we find that in the grand canonical ensemble the pressure has a nonpolynomial dependence on the finite- range parameter and it is a highly nontrivial function of chemical potential and temperature.
Anisotropic superfluidity in a dipolar Bose gas.
Ticknor, Christopher; Wilson, Ryan M; Bohn, John L
2011-02-11
We study the superfluid character of a dipolar Bose-Einstein condensate (DBEC) in a quasi-two dimensional geometry. We consider the dipole polarization to have some nonzero projection into the plane of the condensate so that the effective interaction is anisotropic in this plane, yielding an anisotropic dispersion relation. By performing direct numerical simulations of a probe moving through the DBEC, we observe the sudden onset of drag or creation of vortex-antivortex pairs at critical velocities that depend strongly on the direction of the probe's motion. This anisotropy emerges because of the anisotropic manifestation of a rotonlike mode in the system.
Anisotropic Superfluidity in a Dipolar Bose Gas
Ticknor, Christopher; Wilson, Ryan M.; Bohn, John L.
2011-02-11
We study the superfluid character of a dipolar Bose-Einstein condensate (DBEC) in a quasi-two dimensional geometry. We consider the dipole polarization to have some nonzero projection into the plane of the condensate so that the effective interaction is anisotropic in this plane, yielding an anisotropic dispersion relation. By performing direct numerical simulations of a probe moving through the DBEC, we observe the sudden onset of drag or creation of vortex-antivortex pairs at critical velocities that depend strongly on the direction of the probe's motion. This anisotropy emerges because of the anisotropic manifestation of a rotonlike mode in the system.
Casimir force induced by an imperfect Bose gas.
Napiórkowski, Marek; Piasecki, Jarosław
2011-12-01
We present a study of the Casimir effect in an imperfect (mean-field) Bose gas contained between two infinite parallel plane walls. The derivation of the Casimir force follows from the calculation of the excess grand-canonical free energy density under periodic, Dirichlet, and Neumann boundary conditions with the use of the steepest descent method. In the one-phase region, the force decays exponentially fast when distance D between the walls tends to infinity. When the Bose-Einstein condensation point is approached, the decay length in the exponential law diverges with critical exponent ν(IMP) = 1, which differs from the perfect gas case where ν(P) = 1/2. In the two-phase region, the Casimir force is long range and decays following the power law D(-3), with the same amplitude as in the perfect gas.
Fast thermalization and Helmholtz oscillations of an ultracold Bose gas.
Papoular, D J; Pitaevskii, L P; Stringari, S
2014-10-24
We analyze theoretically the transport properties of a weakly interacting ultracold Bose gas enclosed in two reservoirs connected by a constriction. We assume that the transport of the superfluid part is hydrodynamic, and we describe the ballistic transport of the normal part using the Landauer-Büttiker formalism. Modeling the coupled evolution of the phase, atom number, and temperature mismatches between the reservoirs, we predict that Helmholtz (plasma) oscillations can be observed at nonzero temperatures below Tc. We show that, because of its strong compressibility, the Bose gas is characterized by a fast thermalization compared to the damping time for plasma oscillations, accompanied by a fast transfer of the normal component. This fast thermalization also affects the gas above Tc, where we present a comparison to the ideal fermionic case. Moreover, we outline the possible realization of a superleak through the inclusion of a disordered potential.
Momentum Distribution in the Unitary Bose Gas from First Principles.
Comparin, Tommaso; Krauth, Werner
2016-11-25
We consider a realistic bosonic N-particle model with unitary interactions relevant for Efimov physics. Using quantum Monte Carlo methods, we find that the critical temperature for Bose-Einstein condensation is decreased with respect to the ideal Bose gas. We also determine the full momentum distribution of the gas, including its universal asymptotic behavior, and compare this crucial observable to recent experimental data. Similar to the experiments with different atomic species, differentiated solely by a three-body length scale, our model only depends on a single parameter. We establish a weak influence of this parameter on physical observables. In current experiments, the thermodynamic instability of our model from the atomic gas towards an Efimov liquid could be masked by the dynamical instability due to three-body losses.
Dynamics of impurities in ultracold Bose gas
NASA Astrophysics Data System (ADS)
Shchadilova, Yulia; Grusdt, Fabian; Rubtsov, Alexey; Demler, Eugene
2015-05-01
A system of an impurity immersed in a Bose-Einstein condensate (BEC) exhibits the polaronic effect, which is known to be an ubiquitous phenomenon in a wide range of physical systems including semiconductors, doped Mott insulators, and high-Tc superconductors. Recent analysis of the BEC-polaron problem showed that existing analytical approaches do not provide reliable results in the experimentally relevant range of parameters when tested against Monte Carlo (MC) simulations. In this contribution we demonstrate that the description of polarons at finite momentum can be done by employing an analytical class of wavefunctions based on the correlated Gaussian ansatz (CGWs). We show that CGWs show excellent agreement with known MC results for the polaron binding energy for a wide range of interactions. We discuss the properties of the polarons and atomic mixtures in systems of ultracold atoms in which polaronic effects can be observed with current experimental technology. Our CGWs predicts a specific pattern of correlations between host atoms that can be measured in time-of-flight experiments. Department of Physics, Harvard University.
Ground state of a resonantly interacting Bose gas
Diederix, J. M.; Heijst, T. C. F. van; Stoof, H. T. C.
2011-09-15
We show that a two-channel mean-field theory for a Bose gas near a Feshbach resonance allows for an analytic computation of the chemical potential, and therefore the universal constant {beta}, at unitarity. To improve on this mean-field theory, which physically neglects condensate depletion, we study a variational Jastrow ansatz for the ground-state wave function and use the hypernetted-chain approximation to minimize the energy for all positive values of the scattering length. We also show that other important physical quantities such as Tan's contact and the condensate fraction can be directly obtained from this approach.
Equilibrium state of a trapped two-dimensional Bose gas
Rath, Steffen P.; Yefsah, Tarik; Guenter, Kenneth J.; Cheneau, Marc; Desbuquois, Remi; Dalibard, Jean; Holzmann, Markus; Krauth, Werner
2010-07-15
We study experimentally and numerically the equilibrium density profiles of a trapped two-dimensional {sup 87}Rb Bose gas and investigate the equation of state of the homogeneous system using the local density approximation. We find a clear discrepancy between in situ measurements and quantum Monte Carlo simulations, which we attribute to a nonlinear variation of the optical density of the atomic cloud with its spatial density. However, good agreement between experiment and theory is recovered for the density profiles measured after time of flight, taking advantage of their self-similarity in a two-dimensional expansion.
Two-step condensation of the charged Bose gas.
Delgado, R L; Bargueño, P; Sols, F
2012-09-01
The condensation of the spinless ideal charged Bose gas in the presence of a magnetic field is revisited. The conventional approach is extended to include the macroscopic occupation of excited kinetic states lying in the lowest Landau level, which plays an essential role in the case of large magnetic fields. In that limit, signatures of two diffuse phase transitions (crossovers) appear in the specific heat. In particular, at temperatures lower than the cyclotron frequency, the system behaves as an effectively one-dimensional free boson system, with the specific heat equal to 1/2Nk(B) and a gradual condensation at lower temperatures.
On the Ground-State Energy and Local Pressure of an Inhomogeneous Bose Gas
NASA Astrophysics Data System (ADS)
Bobrov, V. B.; Trigger, S. A.
2017-01-01
The exact expression for the average kinetic energy of an inhomogeneous Bose gas in the ground state is obtained as a functional of the inhomogeneous density of the Bose-Einstein condensate. The result is based on existence of the off-diagonal long-range order in the single-particle density matrix for systems with a Bose-Einstein condensate. This makes it possible to avoid the use of anomalous averages. On this basis, the explicit expressions for the ground-state energy and the local pressure of an inhomogeneous Bose gas are derived within the self-consistent Hartree-Fock approximation.
NASA Astrophysics Data System (ADS)
Mehedi Faruk, Mir; Sazzad Hossain, Md.; Muktadir Rahman, Md.
2016-02-01
The changes in characteristics of Bose condensation of ideal Bose gas due to an external generic power law potential U=\\sumi=1dci\\vert xi/ai\\vertni are studied carefully. Detailed calculation of Kim et al. (J. Phys. Condens. Matter 11 (1999) 10269) yielded the hierarchy of condensation transitions with changing fractional dimensionality. In this manuscript, some theorems regarding specific heat at constant volume CV are presented. Careful examination of these theorems reveal the existence of hidden hierarchy of the condensation transition in trapped systems as well.
Quench dynamics of a strongly interacting resonant Bose gas
NASA Astrophysics Data System (ADS)
Yin, Xiao; Radzihovsky, Leo
2015-03-01
We explore the dynamics of a resonant Bose gas following its quench to a strongly interacting regime near a Feshbach resonance. For such deep quenches, we utilize a self-consistent dynamic mean-field approximation and find that after an initial regime of many-body Rabi-like oscillations between the condensate and finite-momentum quasiparticle pairs, at long times, the gas reaches a prethermalized nonequilibrium steady state. We explore the resulting state through its broad stationary momentum distribution function, that exhibits a power-law high momentum tail. We study the associated enhanced depletion, quench-rate dependent excitation energy, Tan's contact, structure function and radio frequency spectroscopy. We find these predictions to be in a qualitative agreement with recent experiments We acknowledge the supported by the NSF through DMR-1001240 on this research.
Superfluidity and phase transitions in a resonant Bose gas
Radzihovsky, Leo; Weichman, Peter B.; Park, Jae I.
2008-10-15
The atomic Bose gas is studied across a Feshbach resonance, mapping out its phase diagram, and computing its thermodynamics and excitation spectra. It is shown that such a degenerate gas admits two distinct atomic and molecular superfluid phases, with the latter distinguished by the absence of atomic off-diagonal long-range order, gapped atomic excitations, and deconfined atomic {pi}-vortices. The properties of the molecular superfluid are explored, and it is shown that across a Feshbach resonance it undergoes a quantum Ising transition to the atomic superfluid, where both atoms and molecules are condensed. In addition to its distinct thermodynamic signatures and deconfined half-vortices, in a trap a molecular superfluid should be identifiable by the absence of an atomic condensate peak and the presence of a molecular one.
Bose gas with generalized dispersion relation plus an energy gap
NASA Astrophysics Data System (ADS)
Solis, M. A.; Martinez, J. G.; Garcia, J.
We report the critical temperature, the condensed fraction, the internal energy and the specific heat for a d-dimensional Bose gas with a generalized dispersion relation plus an energy gap, i.e., ɛ =ɛ0 for k = 0 and ɛ =ɛ0 + Δ +csks , for k > 0 , where ℏk is the particle momentum, ɛ0 the lowest particle energy, cs a constant with dimension of energy multiplied by a length to the power s > 0 . When Δ > 0 , a Bose-Einstein critical temperature Tc ≠ 0 exists for any d / s >= 0 at which the internal energy shows a peak and the specific heat shows a jump. The critical temperature and the specific heat jump increase as functions of the gap but they decrease as functions of d / s . Thermodynamic properties are ɛ0 independent since this is just a reference energy. For Δ = 0 we recover the results reported in Ref. [1]. V. C. Aguilera-Navarro, M. de Llano y M. A. Solís, Eur. J. Phys. 20, 177 (1999). We acknowledge partial support from Grants PAPIIT IN111613 and CONACyT 221030.
Phantom vortices: hidden angular momentum in ultracold dilute Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Weiner, Storm E.; Tsatsos, Marios C.; Cederbaum, Lorenz S.; Lode, Axel U. J.
2017-01-01
Vortices are essential to angular momentum in quantum systems such as ultracold atomic gases. The existence of quantized vorticity in bosonic systems stimulated the development of the Gross-Pitaevskii mean-field approximation. However, the true dynamics of angular momentum in finite, interacting many-body systems like trapped Bose-Einstein condensates is enriched by the emergence of quantum correlations whose description demands more elaborate methods. Herein we theoretically investigate the full many-body dynamics of the acquisition of angular momentum by a gas of ultracold bosons in two dimensions using a standard rotation procedure. We demonstrate the existence of a novel mode of quantized vorticity, which we term the phantom vortex. Contrary to the conventional mean-field vortex, can be detected as a topological defect of spatial coherence, but not of the density. We describe previously unknown many-body mechanisms of vortex nucleation and show that angular momentum is hidden in phantom vortices modes which so far seem to have evaded experimental detection. This phenomenon is likely important in the formation of the Abrikosov lattice and the onset of turbulence in superfluids.
Phantom vortices: hidden angular momentum in ultracold dilute Bose-Einstein condensates.
Weiner, Storm E; Tsatsos, Marios C; Cederbaum, Lorenz S; Lode, Axel U J
2017-01-16
Vortices are essential to angular momentum in quantum systems such as ultracold atomic gases. The existence of quantized vorticity in bosonic systems stimulated the development of the Gross-Pitaevskii mean-field approximation. However, the true dynamics of angular momentum in finite, interacting many-body systems like trapped Bose-Einstein condensates is enriched by the emergence of quantum correlations whose description demands more elaborate methods. Herein we theoretically investigate the full many-body dynamics of the acquisition of angular momentum by a gas of ultracold bosons in two dimensions using a standard rotation procedure. We demonstrate the existence of a novel mode of quantized vorticity, which we term the phantom vortex. Contrary to the conventional mean-field vortex, can be detected as a topological defect of spatial coherence, but not of the density. We describe previously unknown many-body mechanisms of vortex nucleation and show that angular momentum is hidden in phantom vortices modes which so far seem to have evaded experimental detection. This phenomenon is likely important in the formation of the Abrikosov lattice and the onset of turbulence in superfluids.
Phantom vortices: hidden angular momentum in ultracold dilute Bose-Einstein condensates
Weiner, Storm E.; Tsatsos, Marios C.; Cederbaum, Lorenz S.; Lode, Axel U. J.
2017-01-01
Vortices are essential to angular momentum in quantum systems such as ultracold atomic gases. The existence of quantized vorticity in bosonic systems stimulated the development of the Gross-Pitaevskii mean-field approximation. However, the true dynamics of angular momentum in finite, interacting many-body systems like trapped Bose-Einstein condensates is enriched by the emergence of quantum correlations whose description demands more elaborate methods. Herein we theoretically investigate the full many-body dynamics of the acquisition of angular momentum by a gas of ultracold bosons in two dimensions using a standard rotation procedure. We demonstrate the existence of a novel mode of quantized vorticity, which we term the phantom vortex. Contrary to the conventional mean-field vortex, can be detected as a topological defect of spatial coherence, but not of the density. We describe previously unknown many-body mechanisms of vortex nucleation and show that angular momentum is hidden in phantom vortices modes which so far seem to have evaded experimental detection. This phenomenon is likely important in the formation of the Abrikosov lattice and the onset of turbulence in superfluids. PMID:28091520
Superfluid density of a spin-orbit-coupled Bose gas
NASA Astrophysics Data System (ADS)
Zhang, Yi-Cai; Yu, Zeng-Qiang; Ng, Tai Kai; Zhang, Shizhong; Pitaevskii, Lev; Stringari, Sandro
2016-09-01
We discuss the superfluid properties of a uniform, weakly interacting Bose-Einstein condensed gas with spin-orbit coupling, realized recently in experiments. We find a finite normal fluid density ρn at zero temperature which turns out to be a function of the Raman coupling. In particular, the entire fluid becomes normal at the transition point from the zero momentum to the plane wave phase, even though the condensate fraction remains finite. We emphasize the crucial role played by the breaking of Galilean invariance and by the gapped branch of the elementary excitations whose contribution to various sum rules is discussed explicitly. Our predictions for the superfluid density are successfully compared with the available experimental results based on the measurement of the sound velocities.
Dynamics of a finite temperature Bose gas in atomtronic devices
NASA Astrophysics Data System (ADS)
Colussi, Victor; Holland, Murray; Anderson, Dana Z.
2014-05-01
We investigate the problem of modeling atomtronic devices that utilize the nonequilibrium dynamics of a finite temperature Bose-condensed gas placed underneath an atom chip to mimic the properties of classical circuit elements. Our model consists of the full dynamics of the condensate and thermal cloud. The thermal cloud is treated semiclassically, in the spirit of the ZNG method (Zaremba, Nikuni and Griffin.) However, we develop a novel procedure to account for collisions between the condensate and thermal cloud which evaluates collision rates directly. We present the results of this model compared to two experiments: the atomtronic battery and transistor [arXiv:1208.3109v2]. Also presented are predictions for more complex circuit elements. This work is funded by the NSF Physics Frontier Center at JILA and by the Air Force Office of Scientific Research.
Kinetics of a bose gas in harmonic traps: nonergodic behavior
NASA Astrophysics Data System (ADS)
Geist, Wolfgang; You, Li; Kennedy, Brian
1997-11-01
The quantum Boltzmann equation describes kinetics of a degenerate quantum gas. For applications to a trapped Bose gas, it takes the following form *be1 fracdn_idt&=& sum_j,k,lδ (ɛi +ɛj -ɛk -ɛl )*g(i,j,k,l) &&(; n_k*n_l*(1+n_i)*(1+n_j)-n_i*n_j*(1+n_l)*(1+n_k)) * with ni the average number of particles in the state i of the three dimension al harmonic trap labelled by quantum numbers (i_x,i_y,i_z). The delta function ensures energy conservation and the matrix element g(i,j,k,l) is a two-body scattering matrix element which includes an overlap integral of the fou r harmonic oscillator eigenstates associated with the states i,j,k and l. Previous studies of this equation (M.Holland, J.Williams, K.Coakley, J.Cooper, Phys.Rev.A,55,3670, (1996)), (C W Gardiner and P Zoller, Phys.Rev.A(1997)) assume an ergodic approximation (degenerate energy states have equal particle numbers) in order to simplify numerical simula tions. In this study we include a limited number of low lying states without making the ergodic assumption. Interesting nonergodic effects will be reported, and comparisons between the ergodic and nonergodic kinetics will be made.
Dilution and stoichiometry effects on gas reburning: An experimental study
Bilbao, R.; Alzueta, M.U.; Millera, A.; Prada, L.
1997-06-01
Gas reburning is a NO{sub x} reduction technique that can be applied to different combustion systems. The influence of stoichiometry and dilution effects on the efficiency of the gas reburning process has been studied from an experimental point of view at a temperature of 1,100 C. Methane, ethane, and natural gas have been used as reburning fuels. The results obtained show that both stoichiometry and dilution level are very important parameters for the performance of the process.
Interacting Bose gas confined in a Kronig-Penney potential
NASA Astrophysics Data System (ADS)
Rodríguez, O. A.; Solís, M. A.
We analyze the effect of the 1D periodic Kronig-Penney potential, composed of barriers of width b and separated a distance a, over an interacting Bose gas. At T = 0 , the Gross-Pitaevskii equation is solved analytically in terms of the Jacobi elliptic functions for repulsive or attractive interaction between bosons. By applying the boundary conditions for periodic solutions as well as the normalization of the wave function, we arrive to a set of nonlinear equations from which we obtain the density profile and the chemical potential of the condensate as a function of the particle momentum. The profiles for attractive and repulsive interactions are compared with that of the non-interacting case. For attractive interaction we are able to observe a pronounced spatial localization in the middle of every two barriers. We reproduce the well known results when the Kronig-Penney potential becomes a Dirac Comb. We acknowledge partial support from Grants PAPIIT IN111613 and CONACyT 221030.
Vortex patterns in moderately rotating Bose-condensed gas
NASA Astrophysics Data System (ADS)
Imran, Mohd; Ahsan, M. A. H.
2017-02-01
Using exact diagonalization, we investigate the many-body ground state for regular vortex patterns in a rotating Bose-condensed gas of N spinless particles, confined in a quasi-two-dimensional harmonic trap and interacting repulsively via finite-range Gaussian potential. The N-body Hamiltonian matrix is diagonalized in given subspaces of quantized total angular momentum L z , to obtain the lowest-energy eigenstate. Further, the internal structure of these eigenstates is analyzed by calculating the corresponding conditional probability distribution. Specifically, the quantum mechanically stable as well as unstable states in a co-rotating frame are examined in the moderately rotating regime corresponding to angular momenta 4N≤slant {L}z< 5N for N = 16 bosons. In response to externally impressed rotation, the patterns of singly quantized vortices are formed, shaping into canonical polygons with a central vortex at the trap center. The internal structure of unstable states reveals the mechanism of entry, nucleation and pattern formation of vortices with structural phase transition, as the condensate goes from one stable vortical state to the other. The stable polygonal vortex patterns having discrete p-fold rotational symmetry with p = 5 and p = 6 are observed. The hexagonal vortex pattern with p = 6 symmetry is a precursor to the triangular vortex lattice of singly quantized vortices in the thermodynamic limit. For unstable states, quantum melting of vortex patterns due to uncertainty in positions of individual vortices, is also briefly discussed.
NASA Astrophysics Data System (ADS)
Berman, Oleg L.; Kezerashvili, Roman Ya.
2016-06-01
The high-temperature superfluidity of two-dimensional dipolar excitons in two parallel transition metal dichalcogenide (TMDC) layers is predicted. We study Bose-Einstein condensation in the two-component system of dipolar A and B excitons. The effective mass, energy spectrum of the collective excitations, the sound velocity, and critical temperature are obtained for different TMDC materials. It is shown that in the Bogoliubov approximation, the sound velocity in the two-component dilute exciton Bose gas is always larger than in any one-component exciton system. The difference between the sound velocities for two-component and one-component dilute gases is caused by the fact that the sound velocity for a two-component system depends on the reduced mass of A and B excitons, which is always smaller than the individual mass of A or B exciton. Due to this fact, the critical temperature Tc for superfluidity for the two-component exciton system in a TMDC bilayer is about one order of magnitude higher than Tc in any one-component exciton system. We propose to observe the superfluidity of two-dimensional dipolar excitons in two parallel TMDC layers, which causes two opposite superconducting currents in each TMDC layer.
Bose-Einstein condensation in an ultra-hot gas of pumped magnons.
Serga, Alexander A; Tiberkevich, Vasil S; Sandweg, Christian W; Vasyuchka, Vitaliy I; Bozhko, Dmytro A; Chumak, Andrii V; Neumann, Timo; Obry, Björn; Melkov, Gennadii A; Slavin, Andrei N; Hillebrands, Burkard
2014-03-11
Bose-Einstein condensation of quasi-particles such as excitons, polaritons, magnons and photons is a fascinating quantum mechanical phenomenon. Unlike the Bose-Einstein condensation of real particles (like atoms), these processes do not require low temperatures, since the high densities of low-energy quasi-particles needed for the condensate to form can be produced via external pumping. Here we demonstrate that such a pumping can create remarkably high effective temperatures in a narrow spectral region of the lowest energy states in a magnon gas, resulting in strikingly unexpected transitional dynamics of Bose-Einstein magnon condensate: the density of the condensate increases immediately after the external magnon flow is switched off and initially decreases if it is switched on again. This behaviour finds explanation in a nonlinear 'evaporative supercooling' mechanism that couples the low-energy magnons overheated by pumping with all the other thermal magnons, removing the excess heat, and allowing Bose-Einstein condensate formation.
Collective modes of a one-dimensional trapped atomic Bose gas at finite temperatures
NASA Astrophysics Data System (ADS)
Hu, Hui; Xianlong, Gao; Liu, Xia-Ji
2014-07-01
We theoretically investigate collective modes of a one-dimensional (1D) interacting Bose gas in a harmonic tras at finite temperatures, by using a variational approach and the local density approximation. We find that the temperature dependence of collective mode frequencies is notably different in the weakly and strongly interacting regimes. Therefore, the experimental measurement of collective modes could provide a sensitive probe for different quantum phases of a 1D trapped Bose gas, realized by tuning the interatomic interaction strength and temperature. Our prediction on the temperature dependence of the breathing mode frequency is in good qualitative agreement with an earlier experimental measurement for a weakly interacting 1D Bose gas of rubidium-87 atoms in harmonic traps [Moritz et al., Phys. Rev. Lett. 91, 250402 (2003), 10.1103/PhysRevLett.91.250402].
Ultrarelativistic Bose-Einstein gas on Lorentz symmetry violation
NASA Astrophysics Data System (ADS)
de Sales, J. A.; Costa-Soares, T.; Vasquez Otoya, V. J.
2012-11-01
In this paper, we study the effects of Lorentz Symmetry Breaking on the thermodynamic properties of ideal gases. Inspired by the dispersion relation coming from the Carroll-Field-Jackiw model for Electrodynamics with Lorentz and CPT violation term, we compute the thermodynamics quantities for a Boltzmann, Fermi-Dirac and Bose-Einstein distributions. Two regimes are analyzed: the large and the small Lorentz violation. In the first case, we show that the topological mass induced by the Chern-Simons term behaves as a chemical potential. For Bose-Einstein gases, a condensation in both regimes can be found.
Exact Vortex Nucleation and Cooperative Vortex Tunneling in Dilute Bose-Einstein Condensates
Parke, M. I.; Wilkin, N. K.; Gunn, J. M. F.; Bourne, A.
2008-09-12
With the imminent advent of mesoscopic rotating Bose-Einstein condensates in the lowest Landau level regime, we explore lowest Landau level vortex nucleation. An exact many-body analysis is presented in a weakly elliptical trap for up to 400 particles. Striking non-mean-field features are exposed at filling factors >>1. For example, near the critical rotation frequency pairs of energy levels approach each other with exponential accuracy. A physical interpretation is provided by requantizing a mean-field theory, where 1/N plays the role of Planck's constant, revealing two vortices cooperatively tunneling between classically degenerate energy minima. The tunnel splitting variation is described in terms of frequency, particle number, and ellipticity.
Single-particle spectral density of a Bose gas in the two-fluid hydrodynamic regime
Arahata, Emiko; Nikuni, Tetsuro; Griffin, Allan
2011-11-15
In Bose superfluids, the single-particle Green's function can be directly related to the superfluid velocity-velocity correlation function in the hydrodynamic regime. An explicit expression for the single-particle spectral density was originally written down by Hohenberg and Martin in 1965, starting from the two-fluid equations for a superfluid. We give a simple derivation of their results. Using these results, we calculate the relative weights of first and second sound modes in the single-particle spectral density as a function of temperature in a uniform Bose gas. We show that the second sound mode makes a dominant contribution to the single-particle spectrum in a relatively high-temperature region. We also discuss the possibility of experimental observation of the second sound mode in a Bose gas by photoemission spectroscopy.
Gas dilution system results and application to acid rain utilities
Jolley-Souders, K.; Geib, R.; Dunn, C.
1997-12-31
In 1997, the United States EPA will remove restrictions preventing acid rain utilities from using gas dilution systems for calibration or linearity studies for continuous emissions monitoring, Test Method 205 in 40CFR51 requires that a gas dilution system must produce calibration gases whose measured values are within {+-}2% of predicted values. This paper presents the evaluation of the Environics/CalMat 2020 Dilution System for use in calibration studies. Internal studies show that concentrations generated by this unit are within {+-}0.5% of predicted values. Studies are being conducted by several acid rain utilities to evaluate the Environics/CalMat system using single minor component calibration standards. In addition, an internally generated study is being performed to demonstrate the system`s accuracy using a multi-component gas mixture. Data from these tests will be presented in the final version of the paper.
Evaluation of two gas-dilution methods for instrument calibration
NASA Technical Reports Server (NTRS)
Evans, A., Jr.
1977-01-01
Two gas dilution methods were evaluated for use in the calibration of analytical instruments used in air pollution studies. A dual isotope fluorescence carbon monoxide analyzer was used as the transfer standard. The methods are not new but some modifications are described. The rotary injection gas dilution method was found to be more accurate than the closed loop method. Results by the two methods differed by 5 percent. This could not be accounted for by the random errors in the measurements. The methods avoid the problems associated with pressurized cylinders. Both methods have merit and have found a place in instrument calibration work.
Liu, Xia-Ji Hu, Hui
2014-12-15
We theoretically investigate first and second sound of a two-dimensional (2D) atomic Bose gas in harmonic traps by solving Landau’s two-fluid hydrodynamic equations. For an isotropic trap, we find that first and second sound modes become degenerate at certain temperatures and exhibit typical avoided crossings in mode frequencies. At these temperatures, second sound has significant density fluctuation due to its hybridization with first sound and has a divergent mode frequency towards the Berezinskii–Kosterlitz–Thouless (BKT) transition. For a highly anisotropic trap, we derive the simplified one-dimensional hydrodynamic equations and discuss the sound-wave propagation along the weakly confined direction. Due to the universal jump of the superfluid density inherent to the BKT transition, we show that the first sound velocity exhibits a kink across the transition. These predictions might be readily examined in current experimental setups for 2D dilute Bose gases with a sufficiently large number of atoms, where the finite-size effect due to harmonic traps is relatively weak.
Momentum-Space Correlations of a One-Dimensional Bose Gas.
Fang, Bess; Johnson, Aisling; Roscilde, Tommaso; Bouchoule, Isabelle
2016-02-05
Analyzing the noise in the momentum profiles of single realizations of one-dimensional Bose gases, we present the experimental measurement of the full momentum-space density correlations ⟨δn_{p}δn_{p^{'}}⟩, which are related to the two-body momentum correlation function. Our data span the weakly interacting region of the phase diagram, going from the ideal Bose gas regime to the quasicondensate regime. We show experimentally that the bunching phenomenon, which manifests itself as super-Poissonian local fluctuations in momentum space, is present in all regimes. The quasicondensate regime is, however, characterized by the presence of negative correlations between different momenta, in contrast to the Bogolyubov theory for Bose condensates, predicting positive correlations between opposite momenta. Our data are in good agreement with ab initio calculations.
Equation of state and contact of a strongly interacting Bose gas in the normal state
Liu, Xia -Ji; Mulkerin, Brendan; He, Lianyi; Hu, Hui
2015-04-27
Here, we theoretically investigate the equation of state and Tan's contact of a nondegenerate three-dimensional Bose gas near a broad Feshbach resonance, within the framework of large-N expansion. Our results agree with the path-integral Monte Carlo simulations in the weak-coupling limit and recover the second-order virial expansion predictions at strong interactions and high temperatures. At resonance, we find that the chemical potential and energy are significantly enhanced by the strong repulsion, while the entropy does not change significantly. With increasing temperature, the two-body contact initially increases and then decreases like T^{–1} at large temperature, and therefore exhibits a peak structure at about 4T_{c0}, where T_{c0} is the Bose-Einstein condensation temperature of an ideal, noninteracting Bose gas. These results may be experimentally examined with a nondegenerate unitary Bose gas, where the three-body recombination rate is substantially reduced. In particular, the nonmonotonic temperature dependence of the two-body contact could be inferred from the momentum distribution measurement.
Distribution of Zeros and the Equation of State. IV ---Ideal Bose-Einstein Gas---
NASA Astrophysics Data System (ADS)
Ikeda, K.
1982-09-01
The ideal Bose-Einstein gas is investigated on the basis of the fundamental concept of the distribution of zeros of the grand partition function on the complex z(= activity) plane. For this gas there are no zeros; but poles play essentially the same role as zeros from an analytical point of view, and are distributed on the part of the positive real axis from λ-3(>0) to +∞, where λ=h(2π mkT)-1/2. The distribution function of poles is calculated, and the function-theoretical structure of the equation of state is discussed. The Bose-Einstein condensation (especially the continuity of the slope of the p-v isotherm at the condensation point and the continuity of the specific heat at the transition temperature) is examined from the point of view of the distribution of poles. From the same point of view the two-dimensional and one-dimensional ideal Bose-Einstein gases are treated. Finally, the n-dimensional (n≥ 4) ideal Bose-Einstein gas is discussed, and it is shown that for n≥ 5 the specific heat is discontinuous at the transition temperature.
Equation of state and contact of a strongly interacting Bose gas in the normal state
Liu, Xia -Ji; Mulkerin, Brendan; He, Lianyi; ...
2015-04-27
Here, we theoretically investigate the equation of state and Tan's contact of a nondegenerate three-dimensional Bose gas near a broad Feshbach resonance, within the framework of large-N expansion. Our results agree with the path-integral Monte Carlo simulations in the weak-coupling limit and recover the second-order virial expansion predictions at strong interactions and high temperatures. At resonance, we find that the chemical potential and energy are significantly enhanced by the strong repulsion, while the entropy does not change significantly. With increasing temperature, the two-body contact initially increases and then decreases like T–1 at large temperature, and therefore exhibits a peak structuremore » at about 4Tc0, where Tc0 is the Bose-Einstein condensation temperature of an ideal, noninteracting Bose gas. These results may be experimentally examined with a nondegenerate unitary Bose gas, where the three-body recombination rate is substantially reduced. In particular, the nonmonotonic temperature dependence of the two-body contact could be inferred from the momentum distribution measurement.« less
Quantized vortices in the ideal bose gas: a physical realization of random polynomials.
Castin, Yvan; Hadzibabic, Zoran; Stock, Sabine; Dalibard, Jean; Stringari, Sandro
2006-02-03
We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.
[Study on drawing aseptic gas in diluting drugs].
Fan, Z C; Yu, F Y; Zou, F S
1996-07-01
In this study, the gas was drawn from sealed aseptic bottles, the blue flame of an alcohol lamp, and the air of the same treatment room. And the gas was put into aseptic solutions of 10% glucose separately and dripped. Then the samples were taken for bacteriaculture at appointed time-points. Meanwhile, the gases were drawn and put into aseptic solutions of 10% glucose separately. Then deactived penicillines were diluted with the solutions separately. Finally, the penicillines were mixed with 10% glucose and dripped. The samples were taken for bacteria-culture in the same way. The results showed that there was no colony existed in the gas from the sealed aseptic bottles and the flame of the alcohol lamp. However, colonies existed in the samples from the air of the treatment room. It is suggested that sealed aseptic gas should be drawn and kept for use in diluting drugs.
Stability spectroscopy of rotons in a dipolar Bose gas
NASA Astrophysics Data System (ADS)
Corson, John P.; Wilson, Ryan M.; Bohn, John L.
2013-05-01
We study the stability of a quasi-one-dimensional dipolar Bose-Einstein condensate that is perturbed by a weak lattice potential along its axis. Our numerical simulations demonstrate that systems exhibiting a roton-maxon structure destabilize readily when the lattice wavelength equals either half the roton wavelength or a low roton subharmonic. We apply perturbation theory to the Gross-Pitaevskii and Bogoliubov-de Gennes equations to illustrate the mechanisms behind the instability threshold. The features of our stability diagram may be used as a direct measurement of the roton wavelength for quasi-one-dimensional geometries.
Stability Spectroscopy of Rotons in a Dipolar Bose Gas
NASA Astrophysics Data System (ADS)
Corson, John; Wilson, Ryan; Bohn, John
2013-05-01
We study the stability of a quasi-one-dimensional dipolar Bose-Einstein condensate that is perturbed by a weak lattice potential along its axis. Our numerical simulations demonstrate that systems exhibiting a roton-maxon structure destabilize readily when the lattice wavelength equals either half the roton wavelength or a low roton subharmonic. We apply perturbation theory to the Gross-Pitaevskii and Bogoliubov de Gennes equations to illustrate the mechanisms behind the instability threshold. The features of our stability diagram are a novel signature of roton physics, and their experimental observation would constitute a direct measurement of the roton wavelength for quasi-one-dimensional geometries.
Onset of thermalization in a 1D Bose gas
NASA Astrophysics Data System (ADS)
Riou, Jean-Felix; Reinhard, Aaron W.; Adams, Laura; Weiss, David S.
2011-05-01
There has been considerable theoretical debate about how nearly integrable many-body quantum systems approach thermal equilibrium. Experiments on one dimensional Bose gases in optical lattices may shed light on this issue. We have studied the time evolution of momentum distributions of Rb clouds initially prepared in ``quantum Newton's cradle'' states [T. Kinoshita, T. Wenger and David S. Weiss, ``A quantum Newton's Cradle,'' Nature 440, 900 (2006)]. The measured evolution rates are found to depend on density and lattice depth. In order to isolate the part of the approach to equilibrium due to atom-atom interactions, it has been necessary to quantify, experimentally and theoretically, the contributions of various heating and loss processes to these rates.
Fermi-to-Bose crossover in a trapped quasi-2D gas of fermionic atoms
NASA Astrophysics Data System (ADS)
Turlapov, A. V.; Kagan, M. Yu
2017-09-01
The physics of many-body systems where particles are restricted to move in two spatial dimensions is challenging and even controversial: on one hand, neither long-range order nor Bose condensation may appear in infinite uniform 2D systems at finite temperature, on the other hand this does not prohibit superfluidity or superconductivity. Moreover, 2D superconductors, such as cuprates, are among the systems with the highest critical temperatures. Ultracold atoms are a platform for studying 2D physics. Unique from other physical systems, quantum statistics may be completely changed in an ultracold gas: an atomic Fermi gas may be smoothly crossed over into a gas of Bose molecules (or dimers) by tuning interatomic interactions. We review recent experiments where such crossover has been demonstrated, as well as critical phenomena in the Fermi-to-Bose crossover. We also present simple theoretical models describing the gas at different points of the crossover and compare the data to these and more advanced models.
Non-equilibrium dynamics of an impurity in the one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Robinson, Neil; Konik, Robert
2015-03-01
In recent years, the out-of-equilibrium dynamics of interacting many-body quantum systems have attracted much attention. Integrable quantum models have played an important role in understanding the role of local conservation laws in the relaxation of observables, explaining unusual experimental observations in the one-component Bose gas. We study the non-equilibrium dynamics of ``impurity'' wave packets containing a single boson propagating in the one-component Bose gas. Utilizing the integrability of the multi-component Lieb-Liniger model and recent results from the algebraic Bethe ansatz, we compute the time-evolution of the density profile of the ``impurity'' in the cases where the bosons is of the same or different species as the background gas. Our method, based upon numerically solving the Bethe ansatz equations and evaluating the Lehmann spectral representation for local observables, allows us to reach long times with high numerical precision. By comparing results from the two-component Lieb-Liniger model to the one-component Bose gas we can comment on the role of distinguishability in the dynamics of impurities in integrable models.
Modeling syngas-fired gas turbine engines with two dilutants
NASA Astrophysics Data System (ADS)
Hawk, Mitchell E.
2011-12-01
Prior gas turbine engine modeling work at the University of Wyoming studied cycle performance and turbine design with air and CO2-diluted GTE cycles fired with methane and syngas fuels. Two of the cycles examined were unconventional and innovative. The work presented herein reexamines prior results and expands the modeling by including the impacts of turbine cooling and CO2 sequestration on GTE cycle performance. The simple, conventional regeneration and two alternative regeneration cycle configurations were examined. In contrast to air dilution, CO2 -diluted cycle efficiencies increased by approximately 1.0 percentage point for the three regeneration configurations examined, while the efficiency of the CO2-diluted simple cycle decreased by approximately 5.0 percentage points. For CO2-diluted cycles with a closed-exhaust recycling path, an optimum CO2-recycle pressure was determined for each configuration that was significantly lower than atmospheric pressure. Un-cooled alternative regeneration configurations with CO2 recycling achieved efficiencies near 50%, which was approximately 3.0 percentage points higher than the conventional regeneration cycle and simple cycle configurations that utilized CO2 recycling. Accounting for cooling of the first two turbine stages resulted in a 2--3 percentage point reduction in un-cooled efficiency, with air dilution corresponding to the upper extreme. Additionally, when the work required to sequester CO2 was accounted for, cooled cycle efficiency decreased by 4--6 percentage points, and was more negatively impacted when syngas fuels were used. Finally, turbine design models showed that turbine blades are shorter with CO2 dilution, resulting in fewer design restrictions.
Measuring the Edwards-Anderson order parameter of the Bose glass: A quantum gas microscope approach
NASA Astrophysics Data System (ADS)
Thomson, S. J.; Walker, L. S.; Harte, T. L.; Bruce, G. D.
2016-11-01
With the advent of spatially resolved fluorescence imaging in quantum gas microscopes, it is now possible to directly image glassy phases and probe the local effects of disorder in a highly controllable setup. Here we present numerical calculations using a spatially resolved local mean-field theory, show that it captures the essential physics of the disordered system, and use it to simulate the density distributions seen in single-shot fluorescence microscopy. From these simulated images we extract local properties of the phases which are measurable by a quantum gas microscope and show that unambiguous detection of the Bose glass is possible. In particular, we show that experimental determination of the Edwards-Anderson order parameter is possible in a strongly correlated quantum system using existing experiments. We also suggest modifications to the experiments which will allow further properties of the Bose glass to be measured.
Ohashi, Y.; Kitaura, M.; Matsumoto, H.
2006-03-15
We investigate a strongly correlated Bose gas in an optical lattice. Extending the standard-basis operator method developed by Haley and Erdoes to a boson Hubbard model, we calculate excitation spectra in the superfluid phase, as well as in the Mott insulating phase, at T=0. In the Mott phase, the excitation spectrum has a finite energy gap, reflecting the localized character of atoms. In the superfluid phase, the excitation spectrum is shown to have an itinerant-localized dual structure, where the gapless Bogoliubov mode (which describes the itinerant character of superfluid atoms) and a band with a finite energy gap coexist. We also show that the rf-tunneling current measurement would give useful information about the duality of a strongly correlated superfluid Bose gas near the superfluid-insulator transition.
Dynamical density-density correlations in the one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Caux, Jean-Sébastien; Calabrese, Pasquale
2006-09-01
The zero-temperature dynamical structure factor of the one-dimensional Bose gas with delta-function interaction (Lieb-Liniger model) is computed as a function of momentum and frequency using a hybrid theoretical/numerical method based on the exact Bethe-ansatz solution. This allows one to interpolate continuously between the weakly coupled Thomas-Fermi and strongly coupled Tonks-Girardeau regimes. The results should be experimentally accessible with Bragg spectroscopy.
Ultraviolet absorption spectra of metalorganic molecules diluted in hydrogen gas
NASA Astrophysics Data System (ADS)
Itoh, Hideo; Watanabe, Masanobu; Mukai, Seiji; Yajima, Hiroyoshi
1988-12-01
Ultraviolet absorption spectra of trimethyl gallium, triethyl gallium, and trimethyl aluminum diluted in hydrogen gas were measured as a function of the wavelength (185-350 nm) and the concentration of the molecules (4.8×10 -6 -1.6×10 -4 mol/liter). Their absorbances changed linearly with the concentration of the molecules, which allowed us to calculate the molar absorption coefficients of the molecules on the basis of the Beer-Lambert law.
Angular momentum relaxation in atom-diatom dilute gas mixtures
NASA Astrophysics Data System (ADS)
Evans, Glenn T.
1987-04-01
The angular momentum relaxation cross sections for a diatomic molecule in a dilute atomic gas are estimated subject to the assumption that the intermolecular torque is dominated by the hard, impulsive contribution (evaluated using Boltzmann kinetic theory for nonspherical molecules). For carbon monoxide in a variety of gases, the kinetic theory derived contribution to the angular momentum cross section is in qualitative agreement with the experimental results of Jameson, Jameson, and Buchi.
Quantum and thermal fluctuations in a Raman spin-orbit-coupled Bose gas
NASA Astrophysics Data System (ADS)
Chen, Xiao-Long; Liu, Xia-Ji; Hu, Hui
2017-07-01
We theoretically study a three-dimensional weakly interacting Bose gas with Raman-induced spin-orbit coupling at finite temperature. By employing a generalized Hartree-Fock-Bogoliubov theory with Popov approximation, we determine a complete finite-temperature phase diagram of three exotic condensation phases (i.e., the stripe, plane-wave, and zero-momentum phases), against both quantum and thermal fluctuations. We find that the plane-wave phase is significantly broadened by thermal fluctuations. The phonon mode and sound velocity at the transition from the plane-wave phase to the zero-momentum phase are thoughtfully analyzed. At zero temperature, we find that quantum fluctuations open an unexpected gap in sound velocity at the phase transition, in stark contrast to the previous theoretical prediction of a vanishing sound velocity. At finite temperature, thermal fluctuations continue to significantly enlarge the gap, and simultaneously shift the critical minimum. For a Bose gas of 87Rb atoms at the typical experimental temperature, T =0.3 T0 , where T0 is the critical temperature of an ideal Bose gas without spin-orbit coupling, our results of gap opening and critical minimum shifting in the sound velocity are qualitatively consistent with the recent experimental observation [Ji et al., Phys. Rev. Lett. 114, 105301 (2015), 10.1103/PhysRevLett.114.105301].
Gas turbine annular combustor with radial dilution air injection
Shekelton, J.R.; Johnson, D.C.
1991-10-22
This patent describes a radial flow gas turbine. It comprises: a rotor including turbine blades and a nozzle adjacent the turbine blades, the nozzle being adapted to direct hot gases at the turbine blades to cause rotation of the rotor; an annular combustor about the rotor and having a combustor outlet leading to the nozzle, the annular combustor having spaced inner and outer walls connected by a generally radially extending wall, the annular combustor including a combustion annulus defined by the inner, outer and radially extending walls upstream of the outlet; a dilution air annulus disposed downstream of the combustion annulus and immediately radially outwardly of the nozzle axially adjacent to and immediately downstream of the combustor outlet of the annular combustion; and a housing substantially surrounding the annular combustor in spaced relation to the inner, outer and radially extending walls thereof, the housing and walls together defining at least a portion of a dilution air flow path having a compressed air inlet in communication with a compressor for supplying dilution air at one end thereof, a turbine nozzle shroud and the inner wall defining the remainder of the dilution air flow path, the compressed air outlet injecting dilution air directly across the combustor outlet toward the compressed air inlet, the illusion air being injected into the hot gases at generally a right angle thereto assist hot gases approach the combustor outlet, the compressed air outlet being in communication with the dilution air annulus directly through the combustor outlet of the annular combustor downstream of the combustion annulus.
Experiments on a one-dimensional Bose gas: Thomas Fermi to Tonks-Girardeau
NASA Astrophysics Data System (ADS)
Wenger, Trevor
A set of experiments was performed on a one-dimensional Bose gas system. A 3D Bose-Einstein condensate of 87Rb atoms was formed in an all-optical trap. The BEC was then loaded into a 2D optical lattice that consists of an array of parallel 1D tubes. Measurements of the energy, cloud size, and local pair correlation function probe the properties of the gas from the weak coupling to strong coupling (Tonks-Girardeau) limit. The characteristic property of fermionization of the wave functions was observed in the TG limit. Another experiment was done to probe the nature on non-equilibrium 1D Bose gases. This integrable system, when placed in a non-equilibrium momentum distribution, was found not to thermalize on the time scale of our experiment (hundreds of trap oscillations or thousands of collisions). This is in stark contrast to the 3D case, which thermalizes on the order of 3 trap oscillations.
Isobars of an ideal Bose gas within the grand canonical ensemble
Jeon, Imtak; Park, Jeong-Hyuck; Kim, Sang-Woo
2011-08-15
We investigate the isobar of an ideal Bose gas confined in a cubic box within the grand canonical ensemble for a large yet finite number of particles, N. After solving the equation of the spinodal curve, we derive precise formulas for the supercooling and the superheating temperatures that reveal an N{sup -1/3} or N{sup -1/4} power correction to the known Bose-Einstein condensation temperature in the thermodynamic limit. Numerical computations confirm the accuracy of our analytical approximation, and further show that the isobar zigzags on the temperature-volume plane if N{>=}14 393. In particular, for the Avogadro's number of particles, the volume expands discretely about 10{sup 5} times. Our results quantitatively agree with a previous study on the canonical ensemble within 0.1% error.
Isobars of an ideal Bose gas within the grand canonical ensemble
NASA Astrophysics Data System (ADS)
Jeon, Imtak; Kim, Sang-Woo; Park, Jeong-Hyuck
2011-08-01
We investigate the isobar of an ideal Bose gas confined in a cubic box within the grand canonical ensemble for a large yet finite number of particles, N. After solving the equation of the spinodal curve, we derive precise formulas for the supercooling and the superheating temperatures that reveal an N-1/3 or N-1/4 power correction to the known Bose-Einstein condensation temperature in the thermodynamic limit. Numerical computations confirm the accuracy of our analytical approximation, and further show that the isobar zigzags on the temperature-volume plane if N≥14393. In particular, for the Avogadro’s number of particles, the volume expands discretely about 105 times. Our results quantitatively agree with a previous study on the canonical ensemble within 0.1% error.
Optimum criteria of an irreversible quantum Brayton refrigeration cycle with an ideal Bose gas
NASA Astrophysics Data System (ADS)
Wang, Hao; Liu, Sanqiu; He, Jizhou
2008-11-01
An irreversible cycle model of the quantum Brayton refrigeration cycle is established, in which finite-time processes and irreversibility in the two adiabatic processes are taken into account. On the basis of the thermodynamic properties of an ideal Bose gas, by using the optimal control-theory, the mathematical expressions for several important performance parameters, such as the coefficient of performance, power input and cooling load, are derived and some important performance parameters, e.g., the temperatures of the working substance at several important state-points, are optimized. By means of numerical predictions, the optimal performance characteristic curves of a Bose-Brayton refrigeration cycle are obtained and analyzed. Furthermore, some optimal operating regions including those for the cooling load, coefficient of performance and the temperatures of the cyclic working substance at the two important state-points are determined and evaluated. Finally, several special cases are discussed in detail.
Correlation dynamics during a slow interaction quench in a one-dimensional Bose gas.
Bernier, Jean-Sébastien; Citro, Roberta; Kollath, Corinna; Orignac, Edmond
2014-02-14
We investigate the response of a one-dimensional Bose gas to a slow increase of its interaction strength. We focus on the rich dynamics of equal-time single-particle correlations treating the Lieb-Liniger model within a bosonization approach and the Bose-Hubbard model using the time-dependent density-matrix renormalization group method. For short distances, correlations follow a power law with distance with an exponent given by the adiabatic approximation. In contrast, for long distances, correlations decay algebraically with an exponent understood within the sudden quench approximation. This long distance regime is separated from an intermediate distance one by a generalized Lieb-Robinson criterion. At long times, in this intermediate regime, bosonization predicts that single-particle correlations decay following a stretched exponential, an unconventional behavior. We develop here an intuitive understanding for the propagation of correlations, in terms of a generalized light cone, applicable to a large variety of systems and quench forms.
Spontaneously Broken Gauge Symmetry in a Bose Gas with Constant Particle Number
NASA Astrophysics Data System (ADS)
Schelle, A.
The interplay between spontaneously broken gauge symmetries and Bose-Einstein condensation has long been controversially discussed in science, since the equations of motion are invariant under phase transformations. Within the present model, it is illustrated that spontaneous symmetry breaking appears as a non-local process in position space, but within disjoint subspaces of the underlying Hilbert space. Numerical simulations show that it is the symmetry of the relative phase distribution between condensate and non-condensate quantum fields which is spontaneously broken when passing the critical temperature for Bose-Einstein condensation. Since the total number of gas particles remains constant over time, the global U(1)-gauge symmetry of the system is preserved.
Critical temperature of a Rashba spin-orbit-coupled Bose gas in a harmonic trap
NASA Astrophysics Data System (ADS)
Hu, Hui; Liu, Xia-Ji
2012-01-01
We investigate theoretically Bose-Einstein condensation of an ideal, trapped Bose gas in the presence of Rashba spin-orbit coupling. Analytic results for the critical temperature and condensate fraction are derived based on a semiclassical approximation to the single-particle-energy spectrum and density of states and are compared with exact results obtained by explicitly summing discrete energy levels for a small number of particles. We find a significant decrease of the critical temperature and of the condensate fraction due to finite spin-orbit coupling. For a large coupling strength and a finite number of particles N, the critical temperature scales as N2/5 and N2/3 in three and two dimensions, respectively, contrasted to the predictions of N1/3 and N1/2 in the absence of spin-orbit coupling. Finite-size corrections in three dimensions are also discussed.
Coherence-enhanced imaging of a degenerate Bose-Einstein gas.
Sadler, L E; Higbie, J M; Leslie, S R; Vengalattore, M; Stamper-Kurn, D M
2007-03-16
We present coherence-enhanced imaging, an in situ technique that uses Raman superradiance to probe the spatial coherence of an ultracold gas. Applying this technique, we identify the coherent portion of an inhomogeneous degenerate (87)Rb gas and obtain a spatially resolved measurement of the first-order spatial correlation function. We find that the decay of spin gratings is enhanced in high density regions of a Bose-Einstein condensate, and ascribe the enhancement to collective atom-atom scattering. Further, we directly observe spatial inhomogeneities that arise generally in the course of extended-sample superradiance.
Probing the Quantum State of a 1D Bose Gas Using Off-Resonant Light Scattering
Sykes, A. G.; Ballagh, R. J.
2011-12-30
We present a theoretical treatment of coherent light scattering from an interacting 1D Bose gas at finite temperatures. We show how this can provide a nondestructive measurement of the atomic system states. The equilibrium states are determined by the temperature and interaction strength, and are characterized by the spatial density-density correlation function. We show how this correlation function is encoded in the angular distribution of the fluctuations of the scattered light intensity, thus providing a sensitive, quantitative probe of the density-density correlation function and therefore the quantum state of the gas.
Ground state and excitations of a Bose gas: From a harmonic trap to a double well
Japha, Y.; Band, Y. B.
2011-09-15
We determine the low-energy properties of a trapped Bose gas split in two by a potential barrier over the whole range of barrier heights and asymmetry between the wells. For either weak or strong coupling between the wells, our two-mode theory yields a two-site Bose-Hubbard Hamiltonian with the tunneling, interaction, and bias parameters calculated simply using an explicit form of two mode functions. When the potential barrier is relatively low, most of the particles occupy the condensate mode and our theory reduces to a two-mode version of the Bogoliubov theory, which gives a satisfactory estimate of the spatial shape and energy of the lowest collective excitation. When the barrier is high, our theory generalizes the standard two-site Bose-Hubbard model into the case of asymmetric modes, and correctly predicts a full separation of the modes in the limit of strong separation of the wells. We provide explicit analytic forms for the number squeezing and coherence as a function of particle number and temperature. We compare our theory to other two-mode theories for bosons in a double well and discuss their validity in different parameter regimes.
Entanglement pre-thermalization in a one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Kaminishi, Eriko; Mori, Takashi; Ikeda, Tatsuhiko N.; Ueda, Masahito
2015-12-01
An isolated quantum system often shows relaxation to a quasi-stationary state before reaching thermal equilibrium. Such a pre-thermalized state was observed in recent experiments in a one-dimensional Bose gas after it had been coherently split into two. Although the existence of local conserved quantities is usually considered to be the key ingredient of pre-thermalization, the question of whether non-local correlations between the subsystems can influence pre-thermalization of the entire system has remained unanswered. Here we study the dynamics of coherently split one-dimensional Bose gases and find that the initial entanglement combined with energy degeneracy due to parity and translation invariance strongly affects the long-term behaviour of the system. The mechanism of this entanglement pre-thermalization is quite general and not restricted to one-dimensional Bose gases. In view of recent experiments with a small and well-defined number of ultracold atoms, our predictions based on exact few-body calculations could be tested in experiments.
Heat Flux for a Relativistic Dilute Bidimensional Gas
NASA Astrophysics Data System (ADS)
García-Perciante, A. L.; Méndez, A. R.; Escobar-Aguilar, E.
2017-02-01
Relativistic kinetic theory predicts substantial modifications to the dissipation mechanisms of a dilute gas. For the heat flux, these include (in the absence of external forces) a correction to the thermal conductivity and the appearance of a new, purely relativistic, term proportional to the density gradient. In this work we obtain such constitutive equation for the particular case of a bidimensional gas. The calculation is based on the Chapman-Enskog solution to the relativistic Boltzmann equation and yields analytical expressions for the corresponding transport coefficients, which are evaluated for the particular case of hard disks. These results will be useful for numerical simulations and may be applied to bidimensional non-dense materials.
Heat Flux for a Relativistic Dilute Bidimensional Gas
NASA Astrophysics Data System (ADS)
García-Perciante, A. L.; Méndez, A. R.; Escobar-Aguilar, E.
2017-04-01
Relativistic kinetic theory predicts substantial modifications to the dissipation mechanisms of a dilute gas. For the heat flux, these include (in the absence of external forces) a correction to the thermal conductivity and the appearance of a new, purely relativistic, term proportional to the density gradient. In this work we obtain such constitutive equation for the particular case of a bidimensional gas. The calculation is based on the Chapman-Enskog solution to the relativistic Boltzmann equation and yields analytical expressions for the corresponding transport coefficients, which are evaluated for the particular case of hard disks. These results will be useful for numerical simulations and may be applied to bidimensional non-dense materials.
Stepwise Bose-Einstein Condensation in a Spinor Gas
NASA Astrophysics Data System (ADS)
Frapolli, C.; Zibold, T.; Invernizzi, A.; Jiménez-García, K.; Dalibard, J.; Gerbier, F.
2017-08-01
We observe multistep condensation of sodium atoms with spin F =1 , where the different Zeeman components mF=0 ,±1 condense sequentially as the temperature decreases. The precise sequence changes drastically depending on the magnetization mz and on the quadratic Zeeman energy q (QZE) in an applied magnetic field. For large QZE, the overall structure of the phase diagram is the same as for an ideal spin-1 gas, although the precise locations of the phase boundaries are significantly shifted by interactions. For small QZE, antiferromagnetic interactions qualitatively change the phase diagram with respect to the ideal case, leading, for instance, to condensation in mF=±1 , a phenomenon that cannot occur for an ideal gas with q >0 .
Stepwise Bose-Einstein Condensation in a Spinor Gas.
Frapolli, C; Zibold, T; Invernizzi, A; Jiménez-García, K; Dalibard, J; Gerbier, F
2017-08-04
We observe multistep condensation of sodium atoms with spin F=1, where the different Zeeman components m_{F}=0,±1 condense sequentially as the temperature decreases. The precise sequence changes drastically depending on the magnetization m_{z} and on the quadratic Zeeman energy q (QZE) in an applied magnetic field. For large QZE, the overall structure of the phase diagram is the same as for an ideal spin-1 gas, although the precise locations of the phase boundaries are significantly shifted by interactions. For small QZE, antiferromagnetic interactions qualitatively change the phase diagram with respect to the ideal case, leading, for instance, to condensation in m_{F}=±1, a phenomenon that cannot occur for an ideal gas with q>0.
Cooperative scattering measurement of coherence in a spatially modulated Bose gas
Lu Bo; Vogt, Thibault; Liu Xinxing; Xu Xu; Zhou Xiaoji; Chen Xuzong
2011-05-15
Correlations of a Bose gas released from an optical lattice are measured using superradiant scattering. Conditions are chosen so that, after initial incident light pumping at the Bragg angle for diffraction, superradiant scattering into the Bragg diffracted mode is preponderant due to matter-wave amplification and mode competition. A temporal analysis of the superradiant scattering gain reveals periodical oscillations and damping due to the initial lack of coherence between lattice sites. Such damping is used for characterizing first-order spatial correlations in our system with a precision of one lattice period.
Two- and three-body contacts in the unitary Bose gas
NASA Astrophysics Data System (ADS)
Fletcher, Richard J.; Lopes, Raphael; Man, Jay; Navon, Nir; Smith, Robert P.; Zwierlein, Martin W.; Hadzibabic, Zoran
2017-01-01
In many-body systems governed by pairwise contact interactions, a wide range of observables is linked by a single parameter, the two-body contact, which quantifies two-particle correlations. This profound insight has transformed our understanding of strongly interacting Fermi gases. Using Ramsey interferometry, we studied coherent evolution of the resonantly interacting Bose gas, and we show here that it cannot be explained by only pairwise correlations. Our experiments reveal the crucial role of three-body correlations arising from Efimov physics and provide a direct measurement of the associated three-body contact.
Coherence properties of a two-dimensional trapped Bose gas around the superfluid transition
Plisson, T.; Allard, B.; Salomon, G.; Aspect, A.; Bourdel, T.; Holzmann, M.; Bouyer, P.
2011-12-15
We measure the momentum distribution of a two-dimensional trapped Bose gas and observe the increase of the range of coherence around the Berezinskii-Kosterlitz-Thouless (BKT) transition. We quantitatively compare our observed profiles to both a Hartree-Fock mean-field theory and quantum Monte Carlo simulations. In the normal phase, the momentum distribution is observed to sharpen well before the phase transition. This behavior is partially captured in a mean-field approach, in contrast to the physics of the BKT transition.
Momentum-Resolved Observation of Thermal and Quantum Depletion in a Bose Gas
NASA Astrophysics Data System (ADS)
Chang, R.; Bouton, Q.; Cayla, H.; Qu, C.; Aspect, A.; Westbrook, C. I.; Clément, D.
2016-12-01
We report on the single-atom-resolved measurement of the distribution of momenta ℏk in a weakly interacting Bose gas after a 330 ms time of flight. We investigate it for various temperatures and clearly separate two contributions to the depletion of the condensate by their k dependence. The first one is the thermal depletion. The second contribution falls off as k-4, and its magnitude increases with the in-trap condensate density as predicted by the Bogoliubov theory at zero temperature. These observations suggest associating it with the quantum depletion. How this contribution can survive the expansion of the released interacting condensate is an intriguing open question.
Non-equilibrium scale invariance and shortcuts to adiabaticity in a one-dimensional Bose gas
Rohringer, W.; Fischer, D.; Steiner, F.; Mazets, I. E.; Schmiedmayer, J.; Trupke, M.
2015-01-01
We present experimental evidence for scale invariant behaviour of the excitation spectrum in phase-fluctuating quasi-1d Bose gases after a rapid change of the external trapping potential. Probing density correlations in free expansion, we find that the temperature of an initial thermal state scales with the spatial extension of the cloud as predicted by a model based on adiabatic rescaling of initial eigenmodes with conserved quasiparticle occupation numbers. Based on this result, we demonstrate that shortcuts to adiabaticity for the rapid expansion or compression of the gas do not induce additional heating. PMID:25867640
NASA Astrophysics Data System (ADS)
Arahata, E.; Nikuni, T.
2013-05-01
We study sound propagation in a Bose-condensed gas confined in a highly elongated harmonic trap at finite temperatures. Our analysis is based on Zaremba-Nikuni-Griffin (ZNG) formalism, which consists of Gross-Pitaevskii equation for the condensate and the kinetic equation for a thermal cloud. We extend ZNG formalism to deal with a highly-anisotropic trap potential, and use it to simulate sound propagation in the two fluid hydrodynamic regime. We use the trap parameters for the experiment that has reported second sound propagation. Our simulation results show that propagation of two sound pulses corresponding to first and second sound can be observed in an intermediate temperature.
Finite Size Effect on the Specific Heat of a Bose Gas in Multi-filament Cables
NASA Astrophysics Data System (ADS)
Guijarro, G.; Solís, M. A.
2016-05-01
The specific heat for an ideal Bose gas confined in semi-infinite multi-filament cables is analyzed. We start with a Bose gas inside a semi-infinite tube of impenetrable walls and finite rectangular cross section. The internal filament structure is created by applying to the gas two, mutually perpendicular, finite Kronig-Penney delta potentials along the tube cross section, while particles are free to move perpendicular to the cross section. The energy spectrum accessible to the particles is obtained and introduced into the grand potential to calculate the specific heat of the system as a function of temperature for different values of the periodic structure parameters such as the cross-section area, the wall impenetrability, and the number of filaments. The specific heat as a function of temperature shows at least two maxima and one minimum. The main difference with respect to the infinite case is that the peak associated with the BE condensation becomes a smoothed maximum, namely there is not a jump in the specific heat derivative, whose temperature no longer represents a critical point.
Thermodynamic behavior of a one-dimensional Bose gas at low temperature
NASA Astrophysics Data System (ADS)
De Rosi, Giulia; Astrakharchik, Grigori E.; Stringari, Sandro
2017-07-01
We show that the chemical potential of a one-dimensional (1D) interacting Bose gas exhibits a nonmonotonic temperature dependence which is peculiar of superfluids. The effect is a direct consequence of the phononic nature of the excitation spectrum at large wavelengths exhibited by 1D Bose gases. For low temperatures T , we demonstrate that the coefficient in T2 expansion of the chemical potential is entirely defined by the zero-temperature density dependence of the sound velocity. We calculate that coefficient along the crossover between the Bogoliubov weakly interacting gas and the Tonks-Girardeau gas of impenetrable bosons. Analytic expansions are provided in the asymptotic regimes. The theoretical predictions along the crossover are confirmed by comparison with the exactly solvable Yang-Yang model in which the finite-temperature equation of state is obtained numerically by solving Bethe-ansatz equations. A 1D ring geometry is equivalent to imposing periodic boundary conditions and arising finite-size effects are studied in detail. At T =0 we calculated various thermodynamic functions, including the inelastic structure factor, as a function of the number of atoms, pointing out the occurrence of important deviations from the thermodynamic limit.
Level density of a bose gas and extreme value statistics.
Comtet, A; Leboeuf, P; Majumdar, Satya N
2007-02-16
We establish a connection between the level density of a gas of noninteracting bosons and the theory of extreme value statistics. Depending on the exponent that characterizes the growth of the underlying single-particle spectrum, we show that at a given excitation energy the limiting distribution function for the number of excited particles follows the three universal distribution laws of extreme value statistics, namely, the Gumbel, Weibull, and Fréchet distributions. Implications of this result, as well as general properties of the level density at different energies, are discussed.
Strong correlation effects in a two-dimensional Bose gas with quartic dispersion
NASA Astrophysics Data System (ADS)
Radić, Juraj; Natu, Stefan S.; Galitski, Victor
2015-06-01
Motivated by the fundamental question of the fate of interacting bosons in flat bands, we consider a two-dimensional Bose gas at zero temperature with an underlying quartic single-particle dispersion in one spatial direction. This type of band structure can be realized using the NIST scheme of spin-orbit coupling [Y.-J. Lin, K. Jiménez-Garcia, and I. B. Spielman, Nature (London) 471, 83 (2011), 10.1038/nature09887], in the regime where the lower-band dispersion has the form ɛk˜kx4/4 +ky2+... , or using the shaken lattice scheme of Parker et al. [C. V. Parker, L.-C. Ha, and C. Chin, Nat. Phys. 9, 769 (2013), 10.1038/nphys2789]. We numerically compare the ground-state energies of the mean-field Bose-Einstein condensate (BEC) and various trial wave functions, where bosons avoid each other at short distances. We discover that, at low densities, several types of strongly correlated states have an energy per particle (ɛ ), which scales with density (n ) as ɛ ˜n4 /3 , in contrast to ɛ ˜n for the weakly interacting Bose gas. These competing states include a Wigner crystal, quasicondensates described in terms of properly symmetrized fermionic states, and variational wave functions of Jastrow type. We find that one of the latter has the lowest energy among the states we consider. This Jastrow-type state has a strongly reduced, but finite, condensate fraction, and true off-diagonal long-range order, which suggests that the ground state of interacting bosons with quartic dispersion is a strongly correlated condensate reminiscent of superfluid helium-4. Our results show that even for weakly interacting bosons in higher dimensions, one can explore the crossover from a weakly coupled BEC to a strongly correlated condensate by simply tuning the single-particle dispersion or density.
Quantum Joule-Thomson effect in a saturated homogeneous Bose gas.
Schmidutz, Tobias F; Gotlibovych, Igor; Gaunt, Alexander L; Smith, Robert P; Navon, Nir; Hadzibabic, Zoran
2014-01-31
We study the thermodynamics of Bose-Einstein condensation in a weakly interacting quasihomogeneous atomic gas, prepared in an optical-box trap. We characterize the critical point for condensation and observe saturation of the thermal component in a partially condensed cloud, in agreement with Einstein's textbook picture of a purely statistical phase transition. Finally, we observe the quantum Joule-Thomson effect, namely isoenthalpic cooling of an (essentially) ideal gas. In our experiments this cooling occurs spontaneously, due to energy-independent collisions with the background gas in the vacuum chamber. We extract a Joule-Thomson coefficient μJT>10(9) K/bar, about 10 orders of magnitude larger than observed in classical gases.
Quantum Joule-Thomson Effect in a Saturated Homogeneous Bose Gas
NASA Astrophysics Data System (ADS)
Schmidutz, Tobias F.; Gotlibovych, Igor; Gaunt, Alexander L.; Smith, Robert P.; Navon, Nir; Hadzibabic, Zoran
2014-01-01
We study the thermodynamics of Bose-Einstein condensation in a weakly interacting quasihomogeneous atomic gas, prepared in an optical-box trap. We characterize the critical point for condensation and observe saturation of the thermal component in a partially condensed cloud, in agreement with Einstein's textbook picture of a purely statistical phase transition. Finally, we observe the quantum Joule-Thomson effect, namely isoenthalpic cooling of an (essentially) ideal gas. In our experiments this cooling occurs spontaneously, due to energy-independent collisions with the background gas in the vacuum chamber. We extract a Joule-Thomson coefficient μJT>109 K /bar, about 10 orders of magnitude larger than observed in classical gases.
Automated measurement of respiratory gas exchange by an inert gas dilution technique
NASA Technical Reports Server (NTRS)
Sawin, C. F.; Rummel, J. A.; Michel, E. L.
1974-01-01
A respiratory gas analyzer (RGA) has been developed wherein a mass spectrometer is the sole transducer required for measurement of respiratory gas exchange. The mass spectrometer maintains all signals in absolute phase relationships, precluding the need to synchronize flow and gas composition as required in other systems. The RGA system was evaluated by comparison with the Douglas bag technique. The RGA system established the feasibility of the inert gas dilution method for measuring breath-by-breath respiratory gas exchange. This breath-by-breath analytical capability permits detailed study of transient respiratory responses to exercise.
Automated measurement of respiratory gas exchange by an inert gas dilution technique
NASA Technical Reports Server (NTRS)
Sawin, C. F.; Rummel, J. A.; Michel, E. L.
1974-01-01
A respiratory gas analyzer (RGA) has been developed wherein a mass spectrometer is the sole transducer required for measurement of respiratory gas exchange. The mass spectrometer maintains all signals in absolute phase relationships, precluding the need to synchronize flow and gas composition as required in other systems. The RGA system was evaluated by comparison with the Douglas bag technique. The RGA system established the feasibility of the inert gas dilution method for measuring breath-by-breath respiratory gas exchange. This breath-by-breath analytical capability permits detailed study of transient respiratory responses to exercise.
Roberts, D.C.; Pomeau, Y.
2005-09-30
We calculate a force due to zero-temperature quantum fluctuations on a stationary object in a moving superfluid flow. We model the object by a localized potential varying only in the flow direction and model the flow by a three-dimensional weakly interacting Bose-Einstein condensate at zero temperature. We show that this force exists for any arbitrarily small flow velocity and discuss the implications for the stability of superfluid flow.
Generation and exploration of the Spin-Orbit coupled Bose gas
NASA Astrophysics Data System (ADS)
Pan, Jian-Wei
2013-03-01
To generate an artificial gauge field with ultracold quantum gas becomes a very hot topic in last few years and will continue to be attractive for ultracold atomic and condensed matter physics in the coming future. Many interesting and important topics such as Fractional Quantum Hall effect, Spin-orbit coupling and Topological insulator are connected to this topic very closely. Here we present our recent experimental progress of the synthesized gauge potential and the spin-orbit coupled Bose-Einstein condensate (BEC) in optical dipole trap. Raman coupling technique and a bias magnetic field is applied to tune the structure of the gauge potential and spin-orbit coupling. Several fundamental properties of spin-orbit coupled BEC is experimentally studied including the properties of collective dipole oscillation, the stability of excited dressed state, the critical temperature of spin-orbit coupled Bose gas and the formation of magnetic order during evaporative cooling. These studies enrich the knowledge of this field and further explorations are also in planning.
Nondissipative drag of superflow in a two-component Bose gas
Fil, D.V.; Shevchenko, S.I.
2005-07-15
A microscopic theory of a nondissipative drag in a two-component superfluid Bose gas is developed. The expression for the drag current in the system with the components of different atomic masses, densities, and scattering lengths is derived. It is shown that the drag current is proportional to the square root of the gas parameter. The temperature dependence of the drag current is studied and it is shown that at temperature of order or smaller than the interaction energy the temperature reduction of the drag current is rather small. A possible way of measuring the drag factor is proposed. A toroidal system with the drag component confined in two half-ring wells separated by two Josephson barriers is considered. Under certain condition such a system can be treated as a Bose-Einstein counterpart of the Josephson charge qubit in an external magnetic field. It is shown that the measurement of the difference of number of atoms in two wells under a controlled evolution of the state of the qubit allows one to determine the drag factor.
Stoner ferromagnetism in a thermal pseudospin-1/2 Bose gas.
Radić, Juraj; Natu, Stefan S; Galitski, Victor
2014-10-31
We compute the finite-temperature phase diagram of a pseudospin-1/2 Bose gas with contact interactions, using two complementary methods: the random-phase approximation and self-consistent Hartree-Fock theory. We show that the spin-dependent interactions, which break the (pseudo-) spin-rotational symmetry of the Hamiltonian, generally lead to the appearance of a magnetically ordered phase at temperatures above the superfluid transition. In three dimensions, we predict a normal easy-axis (easy-plane) ferromagnet for sufficiently strong repulsive (attractive) interspecies interactions, respectively. The normal easy-axis ferromagnet is the bosonic analog of Stoner ferromagnetism known in electronic systems. For the case of interspecies attraction, we also discuss the possibility of a bosonic analog of the Cooper-paired phase. This state is shown to significantly lose in energy to the transverse ferromagnet in three dimensions, but is more energetically competitive in lower dimensions. Extending our calculations to a spin-orbit-coupled Bose gas with equal Rashba and Dresselhaus-type couplings (as recently realized in experiment), we investigate the possibility of stripe ordering in the normal phase. Within our approximations, however, we do not find an instability towards stripe formation, suggesting that the stripe order melts below the condensation temperature, which is consistent with the experimental observations of Ji et al. [Ji et al., Nat. Phys. 10, 314 (2014)].
Quantum sine-Gordon dynamics on analogue curved spacetime in a weakly imperfect scalar Bose gas
NASA Astrophysics Data System (ADS)
Volkoff, T. J.; Fischer, Uwe R.
2016-07-01
Using the coherent state functional integral expression of the partition function, we show that the sine-Gordon model on an analogue curved spacetime arises as the effective quantum field theory for phase fluctuations of a weakly imperfect Bose gas on an incompressible background superfluid flow when these fluctuations are restricted to a subspace of the single-particle Hilbert space. We consider bipartitions of the single-particle Hilbert space relevant to experiments on ultracold bosonic atomic or molecular gases, including, e.g., restriction to high- or low-energy sectors of the dynamics and spatial bipartition corresponding to tunnel-coupled planar Bose gases. By assuming full unitary quantum control in the low-energy subspace of a trapped gas, we show that (1) appropriately tuning the particle number statistics of the lowest-energy mode partially decouples the low- and high-energy sectors, allowing any low-energy single-particle wave function to define a background for sine-Gordon dynamics on curved spacetime and (2) macroscopic occupation of a quantum superposition of two states of the lowest two modes produces an analogue curved spacetime depending on two background flows, with respective weights continuously dependent on the corresponding weights of the superposed quantum states.
Plane shock wave structure in a dilute granular gas
NASA Astrophysics Data System (ADS)
Reddy, M. H. Lakshminarayana; Alam, Meheboob
2016-11-01
We analyse the early time evolution of the Riemann problem of planar shock wave structures for a dilute granular gas by solving Navier-Stokes equations numerically. The one-dimensional reduced Navier-Stokes equations for plane shock wave problem are solved numerically using a relaxation-type numerical scheme. The results on the shock structures in granular gases are presented for different Mach numbers and restitution coefficients. Based on our analysis on early time shock dynamics we conclude that the density and temperature profiles are "asymmetric"; the density maximum and the temperature maximum occur within the shock layer; the absolute magnitudes of longitudinal stress and heat flux which are initially zero at both end states attain maxima in a very short time and thereafter decrease with time.
Lorentz-violating effects in the Bose-Einstein condensation of an ideal bosonic gas
NASA Astrophysics Data System (ADS)
Casana, Rodolfo; da Silva, Kleber A. T.
2015-03-01
We have studied the effects of Lorentz-violation in the Bose-Einstein condensation (BEC) of an ideal boson gas, by assessing both the nonrelativistic and ultrarelativistic limits. Our model describes a massive complex scalar field coupled to a CPT-even and Lorentz-violating background. We first analyze the nonrelativistic case, at this level by using experimental data, we obtain upper-bounds for some LIV parameters. In the sequel, we have constructed the partition function for the relativistic ideal boson gas which to be able of a consistent description requires the imposition of severe restrictions on some LIV coefficients. In both cases, we have demonstrated that the LIV contributions are contained in an overall factor, which multiplies almost all thermodynamical properties. An exception is the fraction of the condensed particles.
Hydrodynamic versus collisionless dynamics of a one-dimensional harmonically trapped Bose gas
NASA Astrophysics Data System (ADS)
De Rosi, Giulia; Stringari, Sandro
2016-12-01
By using a sum-rule approach we investigate the transition between the hydrodynamic and the collisionless regime of the collective modes in a one-dimensional (1D) harmonically trapped Bose gas. Both the weakly interacting gas and the Tonks-Girardeau limits are considered. We predict that the excitation of the dipole compression mode is characterized in the high-temperature collisionless regime by a beating signal of two different frequencies (ωz and 3 ωz ), while in the high-temperature collisional regime, the excitation consists of a single frequency (√{7 }ωz ). This behavior differs from the case of the lowest breathing mode whose excitation consists of a single frequency (2 ωz ) in both regimes. Our predictions for the dipole compression mode open promising perspectives for the experimental investigation of collisional effects in 1D configurations.
Critical behavior of the ideal-gas Bose-Einstein condensation in the Apollonian network.
de Oliveira, I N; dos Santos, T B; de Moura, F A B F; Lyra, M L; Serva, M
2013-08-01
We show that the ideal Boson gas displays a finite-temperature Bose-Einstein condensation transition in the complex Apollonian network exhibiting scale-free, small-world, and hierarchical properties. The single-particle tight-binding Hamiltonian with properly rescaled hopping amplitudes has a fractal-like energy spectrum. The energy spectrum is analytically demonstrated to be generated by a nonlinear mapping transformation. A finite-size scaling analysis over several orders of magnitudes of network sizes is shown to provide precise estimates for the exponents characterizing the condensed fraction, correlation size, and specific heat. The critical exponents, as well as the power-law behavior of the density of states at the bottom of the band, are similar to those of the ideal Boson gas in lattices with spectral dimension d(s)=2ln(3)/ln(9/5)~/=3.74.
Quantum Phase Diffusion of a Bose-Einstein Condensate
Lewenstein, M.; You, L. |
1996-10-01
We discuss the quantum properties of the Bose-Einstein condensate of a dilute gas of atoms in a trap. We show that the phase of the condensate undergoes quantum diffusion which can be detected in far off-resonant light scattering experiments. {copyright} {ital 1996 The American Physical Society.}
NASA Astrophysics Data System (ADS)
Lo Gullo, Nicola; Dell'Anna, Luca
2015-12-01
We study the spreading of density-density correlations and the Loschmidt echo, after different sudden quenches in an interacting one-dimensional Bose gas on a lattice, also in the presence of a superimposed aperiodic potential. We use a time dependent Bogoliubov approach to calculate the evolution of the correlation functions and employ the linked cluster expansion to derive the Loschmidt echo.
Spatially Periodic Structures of an Atomic Bose-Einstein Condensate
Rozanov, N.N.
2005-06-15
The conditions providing the formation of periodic vortex lattices of an interference nature in an atomic Bose-Einstein condensate (i.e., in the absence of rotation of the condensate) are determined. Spatially periodic exact solutions of the nonlocal nonlinear Schroedinger equation (the generalized Gross-Pitaevskii equation) that describes the Bose-Einstein condensate of a dilute gas of alkali metal atoms with due regard for the nonlocality of interatomic interactions are obtained in the form of a set of two or three plane waves. It is shown that periodic vortex lattices can be produced in interference experiments with a Bose-Einstein condensate of a dilute gas of alkali metal atoms.
Emergent structure in a dipolar Bose gas in a one-dimensional lattice
Wilson, Ryan M.; Bohn, John L.
2011-02-15
We consider an ultracold dipolar Bose gas in a one-dimensional lattice. For a sufficiently large lattice recoil energy, such a system becomes a series of nonoverlapping Bose-Einstein condensates that interact via the long-range dipole-dipole interaction (ddi). We model this system via a coupled set of nonlocal Gross-Pitaevskii equations (GPEs) for lattices of both infinite and finite extent. We find significantly modified stability properties in the lattice due to the softening of a discrete roton-like mode, as well as ''islands'' in parameter space where biconcave densities are predicted to exist and that only exist in the presence of the other condensates on the lattice. We solve for the elementary excitations of the system to check the dynamical stability of these solutions and to uncover the nature of their collapse. By solving a coupled set of GPEs exactly on a full numeric grid, we show that this emergent biconcave structure can be realized in a finite lattice with atomic {sup 52}Cr.
Thermodynamics of the Noninteracting Bose Gas in a Two-Dimensional Box
NASA Astrophysics Data System (ADS)
Li, Heqiu; Guo, Qiujiang; Jiang, Ji; Johnston, David C.
Bose-Einstein condensation (BEC) of a noninteracting Bose gas of N particles in a two-dimensional (2D) box with Dirichlet boundary conditions is studied. Confirming previous work, we find that BEC occurs at finite N at low temperatures T without the occurrence of a phase transition. We further show that the crossover temperature between weak and strong increases in BEC upon cooling is TE ~ 1 / log (N) at fixed area per boson, so in the thermodynamic limit there is no significant BEC in 2D at finite T. Calculations of thermodynamic properties versus T and area A are presented, including Helmholtz free energy, entropy S, pressure p, ratio of p to the energy density U / A , heat capacity at constant area CV and at constant pressure Cp, isothermal compressibility κT and thermal expansion coefficient αp, obtained using both the grand canonical ensemble (GCE) and canonical ensemble (CE) formalisms. The GCE formalism gives acceptable predictions for S, p, p / (U / A) , κT and αp at large N, T and A, but fails when N is small or BEC is significant, whereas the CE formalism gives accurate results even at low T and/or A where BEC occurs.
30 CFR 36.49 - Tests of exhaust-gas dilution system.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Tests of exhaust-gas dilution system. 36.49..., EVALUATION, AND APPROVAL OF MINING PRODUCTS APPROVAL REQUIREMENTS FOR PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT Test Requirements § 36.49 Tests of exhaust-gas dilution system. The performance...
30 CFR 36.49 - Tests of exhaust-gas dilution system.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Tests of exhaust-gas dilution system. 36.49..., EVALUATION, AND APPROVAL OF MINING PRODUCTS APPROVAL REQUIREMENTS FOR PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT Test Requirements § 36.49 Tests of exhaust-gas dilution system. The performance...
30 CFR 36.49 - Tests of exhaust-gas dilution system.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Tests of exhaust-gas dilution system. 36.49..., EVALUATION, AND APPROVAL OF MINING PRODUCTS APPROVAL REQUIREMENTS FOR PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT Test Requirements § 36.49 Tests of exhaust-gas dilution system. The performance...
30 CFR 36.49 - Tests of exhaust-gas dilution system.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Tests of exhaust-gas dilution system. 36.49..., EVALUATION, AND APPROVAL OF MINING PRODUCTS APPROVAL REQUIREMENTS FOR PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT Test Requirements § 36.49 Tests of exhaust-gas dilution system. The performance...
30 CFR 36.49 - Tests of exhaust-gas dilution system.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Tests of exhaust-gas dilution system. 36.49..., EVALUATION, AND APPROVAL OF MINING PRODUCTS APPROVAL REQUIREMENTS FOR PERMISSIBLE MOBILE DIESEL-POWERED TRANSPORTATION EQUIPMENT Test Requirements § 36.49 Tests of exhaust-gas dilution system. The performance...
Kosterlitz-Thouless Transition of the Quasi-Two-Dimensional Trapped Bose Gas
Holzmann, Markus; Krauth, Werner
2008-05-16
We use quantum Monte Carlo methods to compute the density profile, the nonclassical moment of inertia, and the condensate fraction of an interacting quasi-two-dimensional trapped Bose gas with up to N{approx}5x10{sup 5} atoms and parameters closely related to recent experiments. We locate the Kosterlitz-Thouless temperature T{sub KT} and discuss intrinsic signatures of the onset of superfluidity in the density profile. Below T{sub KT}, the condensate fraction is macroscopic even for our largest systems and decays only slowly with system size. We show that the thermal population of excited states in the transverse direction changes the two-dimensional density profile noticeably in both the normal and the superfluid phase.
Spin squeezing of a dipolar Bose gas in a double-well potential
NASA Astrophysics Data System (ADS)
Tan, Qing-Shou; Lu, Hai-Yan; Yi, Su
2016-01-01
The spin-squeezing dynamics of a quasi-one-dimensional dipolar Bose gas trapped in a double-well potential is studied by employing the method of the multiconfigurational time-dependent Hartree for bosons. We find that optimal squeezing generated by the dipolar interaction can be improved over the one-axis twisting limit, and this squeezing is much stronger than that obtained by the contact interaction. Moreover, natural orbital-related squeezing can be controlled by the direction of the dipole moment, which provides control for storing the optimal spin squeezing. The origin of the squeezing as well as the relationship between spin squeezing and the two-order correlation function are also discussed.
Thermodynamic Properties of a Trapped Bose Gas:. a Diffusion Monte Carlo Study
NASA Astrophysics Data System (ADS)
Datta, S.
We investigate the thermodynamic properties of a trapped Bose gas of Rb atoms interacting through a repulsive potential at low but finite temperature (kBT < μ < Tc) by Quantum Monte Carlo method based upon the generalization of Feynman-Kac method1-3 applicable to many-body systems at T=0 to finite temperatures. In this paper, we report temperature variation of condensation fraction, chemical potential, density profile, total energy of the system, release energy, frequency shifts and moment of inertia within the realistic potential model (Morse type) for the first time by diffusion Monte Carlo technique. The most remarkable success was in achieving the same trend in the temperature variation of frequency shifts as was observed in JILA4 for both m=2 and m=0 modes. For other things, we agree with the work of Giorgini et al.,5 Pitaevskii et al.6 and Krauth.7
Quenched Dynamics of the Momentum Distribution of the Unitary Bose Gas
NASA Astrophysics Data System (ADS)
Ancilotto, Francesco; Rossi, Maurizio; Salasnich, Luca; Toigo, Flavio
2015-12-01
We study the quenched dynamics of the momentum distribution of a unitary Bose gas under isotropic harmonic confinement within a time-dependent density functional approach based on our recently calculated Monte Carlo bulk equation of state. In our calculations the inter-atomic s-wave scattering length of the trapped bosons is suddenly increased to a very large value and the real-time evolution of the system is studied. Prompted by the very recent experimental data of 85Rb atoms at unitarity (Makotyn et al. in Nat Phys 10:116, 2014) we focus on the momentum distribution as a function of time. Our results suggest that at low momenta, a quasi-stationary momentum distribution is reached after a long transient, contrary to what found experimentally for large momenta which equilibrate on a time scale shorter than the one for three body losses.
Spatial Nonlocal Pair Correlations in a Repulsive 1D Bose Gas
Sykes, A. G.; Davis, M. J.; Kheruntsyan, K. V.; Gangardt, D. M.; Viering, K.; Raizen, M. G.
2008-04-25
We analytically calculate the spatial nonlocal pair correlation function for an interacting uniform 1D Bose gas at finite temperature and propose an experimental method to measure nonlocal correlations. Our results span six different physical realms, including the weakly and strongly interacting regimes. We show explicitly that the characteristic correlation lengths are given by one of four length scales: the thermal de Broglie wavelength, the mean interparticle separation, the healing length, or the phase coherence length. In all regimes, we identify the profound role of interactions and find that under certain conditions the pair correlation may develop a global maximum at a finite interparticle separation due to the competition between repulsive interactions and thermal effects.
Two-dimensional dynamics of expansion of a degenerate Bose gas
NASA Astrophysics Data System (ADS)
Mazets, Igor E.
2012-11-01
Expansion of a degenerate Bose gas released from a pancakelike trap is numerically simulated under the assumption of separation of the motion in the plane of the loose initial trapping and the motion in the direction of the initial tight trapping. The initial conditions for the phase fluctuations are generated using the extension to the two-dimensional case of the description of the phase noise by the Ornstein-Uhlenbeck stochastic process. The numerical simulations, taking into account both the finite size of the two-dimensional system and the atomic interactions, which cannot be neglected on the early stage of expansion, did not reproduce the scaling law for the peaks in the density fluctuation spectra experimentally observed by Choi, Seo, Kwon, and Shin [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.109.125301 109, 125301 (2012)]. The latter experimental results may thus require an explanation beyond our current assumptions.
Reentrant behavior of the breathing-mode-oscillation frequency in a one-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Gudyma, A. Iu.; Astrakharchik, G. E.; Zvonarev, Mikhail B.
2015-08-01
Exciting temporal oscillations of the density distribution is a high-precision method for probing ultracold trapped atomic gases. Interaction effects in their many-body dynamics are particularly puzzling and counter-intuitive in one spatial dimension (1D) due to enhanced quantum correlations. We consider 1D quantum Bose gas in a parabolic trap at zero temperature and explain, analytically and numerically, how oscillation frequency depends on the number of particles, their repulsion, and the trap strength. We identify the frequency with the energy difference between the ground state and a particular excited state. This way we avoided resolving the dynamical evolution of the system, simplifying the problem immensely. We find an excellent quantitative agreement of our results with the data from the Innsbruck experiment [Science 325, 1224 (2009), 10.1126/science.1175850].
Lavie, Nilli; Torralbo, Ana
2010-01-01
Load theory of attention proposes that distractor processing is reduced in tasks with high perceptual load that exhaust attentional capacity within task-relevant processing. In contrast, tasks of low perceptual load leave spare capacity that spills over, resulting in the perception of task-irrelevant, potentially distracting stimuli. Tsal and Benoni (2010) find that distractor response competition effects can be reduced under conditions with a high search set size but low perceptual load (due to a singleton color target). They claim that the usual effect of search set size on distractor processing is not due to attentional load but instead attribute this to lower level visual interference. Here, we propose an account for their findings within load theory. We argue that in tasks of low perceptual load but high set size, an irrelevant distractor competes with the search nontargets for remaining capacity. Thus, distractor processing is reduced under conditions in which the search nontargets receive the spillover of capacity instead of the irrelevant distractor. We report a new experiment testing this prediction. Our new results demonstrate that, when peripheral distractor processing is reduced, it is the search nontargets nearest to the target that are perceived instead. Our findings provide new evidence for the spare capacity spillover hypothesis made by load theory and rule out accounts in terms of lower level visual interference (or mere “dilution”) for cases of reduced distractor processing under low load in displays of high set size. We also discuss additional evidence that discounts the viability of Tsal and Benoni's dilution account as an alternative to perceptual load. PMID:21133554
Off-diagonal long-range order, cycle probabilities, and condensate fraction in the ideal Bose gas.
Chevallier, Maguelonne; Krauth, Werner
2007-11-01
We discuss the relationship between the cycle probabilities in the path-integral representation of the ideal Bose gas, off-diagonal long-range order, and Bose-Einstein condensation. Starting from the Landsberg recursion relation for the canonic partition function, we use elementary considerations to show that in a box of size L3 the sum of the cycle probabilities of length k>L2 equals the off-diagonal long-range order parameter in the thermodynamic limit. For arbitrary systems of ideal bosons, the integer derivative of the cycle probabilities is related to the probability of condensing k bosons. We use this relation to derive the precise form of the pik in the thermodynamic limit. We also determine the function pik for arbitrary systems. Furthermore, we use the cycle probabilities to compute the probability distribution of the maximum-length cycles both at T=0, where the ideal Bose gas reduces to the study of random permutations, and at finite temperature. We close with comments on the cycle probabilities in interacting Bose gases.
NASA Astrophysics Data System (ADS)
Kolomeitsev, E. E.; Voskresensky, D. N.
2016-12-01
The spectrum of bosonic scalar-mode excitations in a normal Fermi liquid with local scalar interaction is investigated for various values and momentum dependence of the scalar Landau parameter f0 in the particle-hole channel. For f0 > 0 the conditions are found when the phase velocity on the spectrum of zero sound acquires a minimum at non-zero momentum. For -1 < f0 < 0 there are only damped excitations, and for f0 < -1 the spectrum becomes unstable against the growth of scalar-mode excitations. An effective Lagrangian for the scalar excitation modes is derived after performing a bosonization procedure. We demonstrate that the instability may be tamed by the formation of a static Bose condensate of the scalar modes. The condensation may occur in a homogeneous or inhomogeneous state relying on the momentum dependence of the scalar Landau parameter. We show that in the isospin-symmetric nuclear matter there may appear a metastable state at subsaturation nuclear density owing to the condensate. Then we consider a possibility of the condensation of the zero-sound-like excitations in a state with a non-zero momentum in Fermi liquids moving with overcritical velocities, provided an appropriate momentum dependence of the Landau parameter f0(k) > 0. We also argue that in peripheral heavy-ion collisions the Pomeranchuk instability may occur already for f0 > -1.
FK-DLR properties of a quantum multi-type Bose-gas with a repulsive interaction
NASA Astrophysics Data System (ADS)
Suhov, Y.; Stuhl, I.
2014-08-01
The paper extends earlier results from Suhov and Kelbert ["FK-DLR states of a quantum Bose-gas with a hardcore interaction," arXiv:1304.0782] and Suhov et al. ["Shift-invariance for FK-DLR states of a 2D quantum Bose-gas," arXiv:1304.4177] about infinite-volume quantum bosonic states (FK-DLR states) to the case of multi-type particles with non-negative interactions. (An example is a quantum Widom-Rowlinson model.) Following the strategy from Suhov and Kelbert and Suhov et al., we establish that, for the values of fugacity z ∈ (0, 1) and inverse temperature β > 0, finite-volume Gibbs states form a compact family in the thermodynamic limit. Next, in dimension two we show that any limit-point state (an FK-DLR state in the terminology adopted in Suhov and Kelbert and Suhov et al.) is translation-invariant.
Disordered spin dependent interactions in a spinor (S=1) Bose gas: A percolation analysis
NASA Astrophysics Data System (ADS)
Nabi, Sk. Noor; Basu, Saurabh
2016-05-01
We study the effect of disorder in the spin dependent interaction of a spinor Bose Hubbard model. We apply mean field theory and observe the presence of Bose glass phase by computing the superfluid order parameter and compressibility. The extent of different types of phase is computed via a percolation analysis for phase diagram corresponding to antiferromagnetic interactions.
Disordered spin dependent interactions in a spinor (S=1) Bose gas: A percolation analysis
Nabi, Sk. Noor; Basu, Saurabh
2016-05-23
We study the effect of disorder in the spin dependent interaction of a spinor Bose Hubbard model. We apply mean field theory and observe the presence of Bose glass phase by computing the superfluid order parameter and compressibility. The extent of different types of phase is computed via a percolation analysis for phase diagram corresponding to antiferromagnetic interactions.
Mora, Christophe; Castin, Yvan
2009-05-08
We consider the grand potential {omega} of a two-dimensional weakly interacting homogeneous Bose gas at zero temperature. Building on a number-conserving Bogoliubov method for a lattice model in the grand canonical ensemble, we calculate the next order term as compared to the Bogoliubov prediction, in a systematic expansion of {omega} in powers of the parameter measuring the weakness of the interaction. Our prediction is in very good agreement with recent Monte Carlo calculations.
Black hole thermodynamics as seen through a microscopic model of a relativistic Bose gas
NASA Astrophysics Data System (ADS)
Skákala, Jozef; Shankaranarayanan, S.
2016-02-01
Equations of gravity when projected on spacetime horizons resemble Navier-Stokes equation of a fluid with a specific equation of state [T. Damour, Surface effects of black hole physics, in Proc. M. Grossman Meeting (North Holland, 1982), p. 587, T. Padmanabhan, Phys. Rev. D 83 (2011) 044048, arXiv:gr-qc/1012.0119, S. Kolekar and T. Padmanabhan, Phys. Rev. D 85 (2011) 024004, arXiv:gr-qc/1012.5421]. We show that this equation of state describes massless ideal relativistic gas. We use these results, and build an explicit and simple molecular model of the fluid living on the Schwarzschild and Reissner-Nordström black hole horizons. For the spin zero Bose gas, our model makes two predictions: (i) The horizon area/entropy is quantized as given by Bekenstein’s quantization rule, (ii) The model explains the correct type of proportionality between horizon area and entropy. However, for the physically relevant range of parameters, the proportionality constant is never equal to 1/4.
Transport of ultracold Bose gases beyond the Gross-Pitaevskii description
Ernst, Thomas; Paul, Tobias; Schlagheck, Peter
2010-01-15
We explore atom-laser-like transport processes of ultracold Bose-condensed atomic vapors in mesoscopic waveguide structures beyond the Gross-Pitaevskii mean-field theory. Based on a microscopic description of the transport process in the presence of a coherent source that models the outcoupling from a reservoir of perfectly Bose-Einstein condensed atoms, we derive a system of coupled quantum evolution equations that describe the dynamics of a dilute condensed Bose gas in the framework of the Hartree-Fock-Bogoliubov approximation. We apply this method to study the transport of dilute Bose gases through an atomic quantum dot and through waveguides with disorder. Our numerical simulations reveal that the onset of an explicitly time-dependent flow corresponds to the appearance of strong depletion of the condensate on the microscopic level and leads to a loss of global phase coherence.
Overlap of exact and Gross-Pitaevskii wave functions in Bose-Einstein condensates of dilute gases
NASA Astrophysics Data System (ADS)
Klaiman, Shachar; Cederbaum, Lorenz S.
2016-12-01
It has been proven theoretically for bosons with two-body repulsive interaction potentials in the dilute limit that the Gross-Pitaevskii equation provides the exact energy and density per particle as does the basic many-particle Schrödinger equation [E. H. Lieb and R. Seiringer, Phys. Rev. Lett. 88, 170409 (2002), 10.1103/PhysRevLett.88.170409]. Here, we investigate the overlap of the Gross-Pitaevskii and exact ground-state wave functions. It is found that this overlap is always smaller than unity and may even vanish despite the fact that both wave functions provide the same energy and density per particle. Consequences are discussed.
Microcanonical finite-size scaling of an ideal Bose gas in a box
NASA Astrophysics Data System (ADS)
Wang, Honghui; He, Jizhou; Wang, Jianhui
2017-01-01
We derive an exact recursive scheme to determine exactly the microcanonical partition function of a finite Bose system. Such a recursive approach is identical to that previously obtained within the context of counting statistics. Within the exact microcanonical ensemble, we study microcanonical finite-size scaling behaviors of condensate fraction and specific heat around the critical energy ɛ c for the finite ideal Bose system. We show that the microcanonical scaling functions governing the various critical behaviors are universal in the ideal Bose-Einstein condensates.
NASA Astrophysics Data System (ADS)
Bera, Sangita; Lekala, Mantile Leslie; Chakrabarti, Barnali; Bhattacharyya, Satadal; Rampho, Gaotsiwe Joel
2017-09-01
'We study the condensate fluctuation and several statistics of weakly interacting attractive Bose gas of 7 Li atoms in harmonic trap. Using exact recursion relation we calculate canonical ensemble partition function and study the thermal evolution of the condensate. As 7 Li condensate is associated with collapse, the number of condensate atom is truly finite and it facilitates to study the condensate in mesoscopic region. Being highly correlated, we utilize the two-body correlated basis function to get the many-body effective potential which is further used to calculate the energy levels. Taking van der Waals interaction as interatomic interaction we calculate several quantities like condensate fraction
Quantum states of dark solitons in the 1D Bose gas
NASA Astrophysics Data System (ADS)
Sato, Jun; Kanamoto, Rina; Kaminishi, Eriko; Deguchi, Tetsuo
2016-07-01
We present a series of quantum states that are characterized by dark solitons of the nonlinear Schrödinger equation (i.e. the Gross-Pitaevskii equation) for the one-dimensional Bose gas interacting through the repulsive delta-function potentials. The classical solutions satisfy the periodic boundary conditions and we simply call them classical dark solitons. Through exact solutions we show corresponding aspects between the states and the solitons in the weak coupling case: the quantum and classical density profiles completely overlap with each other not only at an initial time but also at later times over a long period of time, and they move together with the same speed in time; the matrix element of the bosonic field operator between the quantum states has exactly the same profiles of the square amplitude and the phase as the classical complex scalar field of a classical dark soliton not only at the initial time but also at later times, and the corresponding profiles move together for a long period of time. We suggest that the corresponding properties hold rigorously in the weak coupling limit. Furthermore, we argue that the lifetime of the dark soliton-like density profile in the quantum state becomes infinitely long as the coupling constant approaches zero, by comparing it with the quantum speed limit time. Thus, we call the quantum states quantum dark soliton states.
Nonlinear quantization of a degenerate charged Bose gas in an external Coulomb trap
Reinisch, Gilbert
2004-09-01
We consider a degenerate charged Bose-Coulomb gas populating several discrete stationary boson bound states that are located in a spherical-symmetrical central Coulombian potential. Each such state is defined, through appropriate boundary conditions and normalization, by a so-called 'nonlinear eigenstate' that is actually a solution of the coupled (linear) stationary Schroedinger-like Gross-Pitaevskii differential equation and the (nonlinear) Poisson equation. The corresponding eigenvalues allow us to define the energies of these degenerate boson states, much like the Koopmans orbital energy in atomic physics. This theory applies surprisingly well (compared with the corresponding Hartree-Fock results) to spherical-symmetrical s orbital states in atomic physics (i.e., bosonlike restricted orbital states where the additional spin degree of freedom is already integrated out). Finally the superposition of two such stationary nonlinear eigenstates is investigated and given a semiclassical physical significance similar to a Thomas-Fermi approach. The resulting concepts apply particularly well (namely within an average 1% error bar with respect to spectroscopic data) to the 1s{sup 2}-2s{sup 2} orbital states of the 3{<=}Z{<=}9 atomic subsystems.
Real-space mean-field theory of a spin-1 Bose gas in synthetic dimensions
NASA Astrophysics Data System (ADS)
Hurst, Hilary M.; Wilson, Justin H.; Pixley, J. H.; Spielman, I. B.; Natu, Stefan S.
2016-12-01
The internal degrees of freedom provided by ultracold atoms provide a route for realizing higher dimensional physics in systems with limited spatial dimensions. Nonspatial degrees of freedom in these systems are dubbed "synthetic dimensions." This connection is useful from an experimental standpoint but complicated by the fact that interactions alter the condensate ground state. Here we use the Gross-Pitaevskii equation to study the ground-state properties of a spin-1 Bose gas under the combined influence of an optical lattice, spatially varying spin-orbit coupling, and interactions at the mean-field level. The associated phases depend on the sign of the spin-dependent interaction parameter and the strength of the spin-orbit field. We find "charge"- and spin-density-wave phases which are directly related to helical spin order in real space and affect the behavior of edge currents in the synthetic dimension. We determine the resulting phase diagram as a function of the spin-orbit coupling and spin-dependent interaction strength, considering both attractive (ferromagnetic) and repulsive (polar) spin-dependent interactions, and we provide a direct comparison of our results with the noninteracting case. Our findings are applicable to current and future experiments, specifically with 87Rb, 7Li, 41K, and 23Na.
Superfluidity and relaxation dynamics of a laser-stirred two-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Singh, Vijay Pal; Weitenberg, Christof; Dalibard, Jean; Mathey, Ludwig
2017-04-01
We investigate the superfluid behavior of a two-dimensional (2D) Bose gas of 87Rb atoms using classical field dynamics. In the experiment by R. Desbuquois et al. [Nat. Phys. 8, 645 (2012), 10.1038/nphys2378], a 2D quasicondensate in a trap is stirred with a blue-detuned laser beam along a circular path around the trap center. Here, we study this experiment from a theoretical perspective. The heating induced by stirring increases rapidly above a velocity vc, which we define as the critical velocity. We identify the superfluid, the crossover, and the thermal regime by a finite, a sharply decreasing, and a vanishing critical velocity, respectively. We demonstrate that the onset of heating occurs due to the creation of vortex-antivortex pairs. A direct comparison of our numerical results to the experimental ones shows a good agreement, if a systematic shift of the critical phase-space density is included. We relate this shift to the absence of thermal equilibrium between the condensate and the thermal wings, which were used in the experiment to extract the temperature. We expand on this observation by studying the full relaxation dynamics between the condensate and the thermal cloud.
Relaxation dynamics of the one-dimensional Bose gas via the coordinate Bethe ansatz
NASA Astrophysics Data System (ADS)
Davis, Matthew; Zill, Jan; Wright, Tod; Kheruntsyan, Karen; Gasenzer, Thomas
2015-05-01
Recently there has been significant progress in understanding the nature of relaxation in closed quantum systems following a disturbance. Many of the theoretical results have been obtained through the study of models that can be mapped to non-interacting systems, or via approximate numerical methods. We instead utilise the symbolic evaluation of matrix elements between the coordinate Bethe-ansatz eigenstates of the Lieb-Liniger model to simulate quenches of the one-dimensional Bose gas for up to N = 5 particles. We consider a range of scenarios, including quenches of the interaction strength to both repulsive and attractive values, and the application of momentum kicks in analogy to the quantum Newton's cradle experiment of Ref.. Our approach allows us to compare the time-evolving nonequilibrium correlation functions to their diagonal-ensemble (infinite-time-average) values. We find evidence of relaxation to the diagonal ensemble following a quench to repulsive interactions, and most of our results for relaxed-state correlations agree with recent generalized thermodynamic Bethe-ansatz calculations. However, our results for local third-order correlations differ markedly from the predictions of these generalized ensembles.
Strongly anomalous non-thermal fixed point in a quenched two-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Karl, Markus; Gasenzer, Thomas
2017-09-01
Universal scaling behavior in the relaxation dynamics of an isolated two-dimensional Bose gas is studied by means of semi-classical stochastic simulations of the Gross–Pitaevskii model. The system is quenched far out of equilibrium by imprinting vortex defects into an otherwise phase-coherent condensate. A strongly anomalous non-thermal fixed point is identified, associated with a slowed decay of the defects in the case that the dissipative coupling to the thermal background noise is suppressed. At this fixed point, a large anomalous exponent η ≃ -3 and, related to this, a large dynamical exponent z≃ 5 are identified. The corresponding power-law decay is found to be consistent with three-vortex-collision induced loss. The article discusses these aspects of non-thermal fixed points in the context of phase-ordering kinetics and coarsening dynamics, thus relating phenomenological and analytical approaches to classifying far-from-equilibrium scaling dynamics with each other. In particular, a close connection between the anomalous scaling exponent η, introduced in a quantum-field theoretic approach, and conservation-law induced scaling in classical phase-ordering kinetics is revealed. Moreover, the relation to superfluid turbulence as well as to driven stationary systems is discussed.
NASA Astrophysics Data System (ADS)
Heller, Sigmund; Strunz, Walter T.
2010-12-01
Stochastic field equations represent a powerful tool to describe the thermal state of a trapped Bose gas. Often, such approaches are confronted with the old problem of an ultraviolet catastrophe, which demands a cutoff at high energies. In Heller and Strunz (2009 J. Phys. B: At. Mol. Opt. Phys. 42 081001) we introduce a quantum stochastic field equation, avoiding the cutoff problem through a fully quantum approach based on the Glauber-Sudarshan P-function. For a close link to actual experimental setups, the theory is formulated for a fixed particle number and thus based on the canonical ensemble. In this work the derivation and the non-trivial numerical implementation of the equation is explained in detail. We present applications for finite Bose gases trapped in a variety of potentials and show results for ground state occupation numbers and their equilibrium fluctuations. Moreover, we investigate spatial coherence properties by studying correlation functions of various orders.
Quantum particle-number fluctuations in a two-component Bose gas in a double-well potential
Zin, Pawel; Oles, Bartlomiej; Sacha, Krzysztof
2011-09-15
A two-component Bose gas in a double-well potential with repulsive interactions may undergo a phase separation transition if the interspecies interactions outweigh the intraspecies ones. We analyze the transition in the strong interaction limit within the two-mode approximation. Numbers of particles in each potential well are equal and constant. However, at the transition point, the ground state of the system reveals huge fluctuations of numbers of particles belonging to the different gas components; that is, the probability for observation of any mixture of particles in each potential well becomes uniform.
NASA Astrophysics Data System (ADS)
Amano, Minami; Abe, Hisashi
2017-02-01
Gas dilution systems are commonly used to generate calibration gas mixtures for secondary gas standards. However, if a gas dilution system is used to generate gas mixtures for primary trace-moisture standards in multiple gas species, difficulty arises; flow control with relative stability of better than 0.009% is required although the relative uncertainty of the best gas flow meter to date is around 0.3%. In this study, we developed a novel gas dilution system using critical flow Venturi nozzles to address this problem. The developed dilution system can measure and control the flow rates of gases in the range of approximately 0.05 l min-1 to 7 l min-1 (when converted to those measured at 101 325 Pa and 273.15 K) with relative stability of better than 0.007%. Using the dilution system, we developed a magnetic suspension balance/diffusion-tube humidity generator capable of generating trace moisture in N2 in the range of approximately 10 nmol mol-1 to 5 µmol mol-1 in amount fraction. The accuracy of the generated trace-moisture standard was verified by measurement with cavity ring-down spectroscopy.
Individual Tracer Atoms in an Ultracold Dilute Gas.
Hohmann, Michael; Kindermann, Farina; Lausch, Tobias; Mayer, Daniel; Schmidt, Felix; Lutz, Eric; Widera, Artur
2017-06-30
We report on the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the relaxation of the initial nonthermal state and detect the effect of single collisions which has so far eluded observation. We show that, after few collisions, the measured spatial distribution of the tracer atoms is correctly described by a Langevin equation with a velocity-dependent friction coefficient, over a large range of Knudsen numbers. Our results extend the simple and effective Langevin treatment to the realm of light particles in dilute gases. The experimental technique developed opens up the microscopic exploration of a novel regime of diffusion at the level of individual collisions.
Individual Tracer Atoms in an Ultracold Dilute Gas
NASA Astrophysics Data System (ADS)
Hohmann, Michael; Kindermann, Farina; Lausch, Tobias; Mayer, Daniel; Schmidt, Felix; Lutz, Eric; Widera, Artur
2017-06-01
We report on the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the relaxation of the initial nonthermal state and detect the effect of single collisions which has so far eluded observation. We show that, after few collisions, the measured spatial distribution of the tracer atoms is correctly described by a Langevin equation with a velocity-dependent friction coefficient, over a large range of Knudsen numbers. Our results extend the simple and effective Langevin treatment to the realm of light particles in dilute gases. The experimental technique developed opens up the microscopic exploration of a novel regime of diffusion at the level of individual collisions.
NASA Astrophysics Data System (ADS)
Tiwari, Rakesh Prabhat; Shukla, Alok
2006-06-01
Inhomogeneous boson systems, such as the dilute gases of integral spin atoms in low-temperature magnetic traps, are believed to be well described by the Gross-Pitaevskii equation (GPE). GPE is a nonlinear Schrödinger equation which describes the order parameter of such systems at the mean field level. In the present work, we describe a Fortran 90 computer program developed by us, which solves the GPE using a basis set expansion technique. In this technique, the condensate wave function (order parameter) is expanded in terms of the solutions of the simple-harmonic oscillator (SHO) characterizing the atomic trap. Additionally, the same approach is also used to solve the problems in which the trap is weakly anharmonic, and the anharmonic potential can be expressed as a polynomial in the position operators x, y, and z. The resulting eigenvalue problem is solved iteratively using either the self-consistent-field (SCF) approach, or the imaginary time steepest-descent (SD) approach. Iterations can be initiated using either the simple-harmonic-oscillator ground state solution, or the Thomas-Fermi (TF) solution. It is found that for condensates containing up to a few hundred atoms, both approaches lead to rapid convergence. However, in the strong interaction limit of condensates containing thousands of atoms, it is the SD approach coupled with the TF starting orbitals, which leads to quick convergence. Our results for harmonic traps are also compared with those published by other authors using different numerical approaches, and excellent agreement is obtained. GPE is also solved for a few anharmonic potentials, and the influence of anharmonicity on the condensate is discussed. Additionally, the notion of Shannon entropy for the condensate wave function is defined and studied as a function of the number of particles in the trap. It is demonstrated numerically that the entropy increases with the particle number in a monotonic way. Program summaryTitle of program:bose
Rare Gas Metastable Atom Density in Diluted O2 RF Plasmas
NASA Astrophysics Data System (ADS)
Kitajima, Takeshi; Takahashi, Kei; Nakano, Toshiki; Makabe, Toshiaki
Rare gas diluted O2 plasmas are gaining interests for application to high quality SiO2 film formation. The density of rare gas metastable atoms and O atom in rare gas diluted O2 radio frequency (RF) capacitively coupled plasma (CCP) was measured by optical absorption spectroscopy (OAS). Decreases of rare gas metastable densities due to addition of O2 indicate efficient O atom production by rare gas metastables via collisional quenching. Krypton metastable had highest density among four rare gas species for fixed RF power. The decrease of Ar metastable density due to O2 addition showed quantitative agreement with reported quenching rate coefficient. Detailed discussion on different gas pressures illustrates reduced O2 fraction is the key for selective production of O atoms through rare gas metastables.
Beau, Mathieu; Savoie, Baptiste
2014-05-15
In this paper, we rigorously investigate the reduced density matrix (RDM) associated to the ideal Bose gas in harmonic traps. We present a method based on a sum-decomposition of the RDM allowing to treat not only the isotropic trap, but also general anisotropic traps. When focusing on the isotropic trap, the method is analogous to the loop-gas approach developed by Mullin [“The loop-gas approach to Bose-Einstein condensation for trapped particles,” Am. J. Phys. 68(2), 120 (2000)]. Turning to the case of anisotropic traps, we examine the RDM for some anisotropic trap models corresponding to some quasi-1D and quasi-2D regimes. For such models, we bring out an additional contribution in the local density of particles which arises from the mesoscopic loops. The close connection with the occurrence of generalized-Bose-Einstein condensation is discussed. Our loop-gas-like approach provides relevant information which can help guide numerical investigations on highly anisotropic systems based on the Path Integral Monte Carlo method.
Imai, Hirohiko; Yoshimura, Hironobu; Kimura, Atsuomi; Fujiwara, Hideaki
2017-08-04
We present a new method for the continuous flow production of concentrated hyperpolarized xenon-129 (HP (129)Xe) gas from a dilute xenon (Xe) gas mixture with high nuclear spin polarization. A low vapor pressure (i.e., high boiling-point) gas was introduced as an alternative to molecular nitrogen (N2), which is the conventional quenching gas for generating HP (129)Xe via Rb-Xe spin-exchange optical-pumping (SEOP). In contrast to the generally used method of extraction by freezing Xe after the SEOP process, the quenching gas separated as a liquid at moderately low temperature so that Xe was maintained in its gaseous state, allowing the continuous delivery of highly polarized concentrated Xe gas. We selected isobutene as the candidate quenching gas and our method was demonstrated experimentally while comparing its performance with N2. Isobutene could be liquefied and removed from the Xe gas mixture using a cold trap, and the concentrated HP (129)Xe gas exhibited a significantly enhanced nuclear magnetic resonance (NMR) signal. Although the system requires further optimization depending on the intended purpose, our approach presented here could provide a simple means for performing NMR or magnetic resonance imaging (MRI) measurements continuously using HP (129)Xe with improved sensitivity.
NASA Astrophysics Data System (ADS)
Kocharovsky, V. V.; Scully, Marlan O.; Zhu, Shi-Yao; Suhail Zubairy, M.
2000-02-01
A nonequilibrium approach to the dynamics and statistics of the condensate of an ideal N-atom Bose gas cooling via interaction with a thermal reservoir using the canonical ensemble is developed. We derive simple analytical expressions for the canonical partition function and equilibrium distribution of the number of atoms in the ground state of a trap under different approximations, and compare them with exact numerical results. The N-particle constraint associated with the canonical ensemble is usually a burden. In the words of Kittel, ``in the investigation of the Bose-Einstein...laws it is very inconvenient to impose the restriction that the number of particles in the subsystem shall be held constant.'' But in the present approach, based on the analogy between a second-order phase transition and laser threshold behavior, the N-particle constraint makes the problem easier. We emphasize that the present work provides another example of a case in which equilibrium (detailed balance) solutions to nonequilibrium equations of motion provide a useful supplementary approach to conventional statistical mechanics. We also discuss some dynamical and mesoscopic aspects of Bose-Einstein condensation. The conclusion is that the present analytical (but approximate) results, based on a nonequilibrium approach, are in excellent agreement with exact (but numerical) results. The present analysis has much in common with the quantum theory of the laser.
NASA Astrophysics Data System (ADS)
Girardeau, M. D.
1998-07-01
A recent paper of Gardiner [Phys. Rev. A 56, 1414 (1997)] introduces a particle-number-conserving Bogoliubov method for the excitation spectrum of a Bose-condensed gas, for use in theories of recently experimentally produced trapped atomic Bose condensates. Gardiner's approach is compared and contrasted with the 1959 Girardeau-Arnowitt theory [Phys. Rev. 113, 755 (1959)], to which it is closely related and which is also fully number conserving. The number-conserving Bogoliubov quasiparticle operators of the Girardeau-Arnowitt theory satisfy Bose commutation relations exactly so long as states with the condensate totally depleted are neglected, whereas those of Gardiner satisfy Bose commutation relations only in an approximation that deteriorates progressively as the condensate is depleted.
Basic Mean-Field Theory for Bose-Einstein Condensates
NASA Astrophysics Data System (ADS)
Kevrekidis, P. G.; Frantzeskakis, D. J.; Carretero-González, R.
The phenomenon of Bose-Einstein condensation, initially predicted by Bose [1] and Einstein [2, 3] in 1924, refers to systems of particles obeying the Bose statistics. In particular, when a gas of bosonic particles is cooled below a critical transition temperature T c , the particles merge into the Bose-Einstein condensate (BEC), in which a macroscopic number of particles (typically 103 to 106) share the same quantum state. Bose-Einstein condensation is in fact a quantum phase transition, which is connected to the manifestation of fundamental physical phenomena, such as superfluidity in liquid helium and superconductivity in metals (see, e.g., [4] for a relevant discussion and references). Dilute weakly-interacting BECs were first realized experimentally in 1995 in atomic gases, and specifically in vapors of rubidium [5] and sodium [6]. In the same year, first signatures of Bose-Einstein condensation in vapors of lithium were also reported [7] and were later more systematically confirmed [8]. The significance and importance of the emergence of BECs has been recognized through the 2001 Nobel prize in Physics [9, 10]. During the last years there has been an explosion of interest in the physics of BECs. Today, over fifty experimental groups around the world can routinely produce BECs, while an enormous amount of theoretical work has ensued.
Bose-Einstein condensation on a manifold with non-negative Ricci curvature
Akant, Levent Ertuğrul, Emine Tapramaz, Ferzan Turgut, O. Teoman
2015-01-15
The Bose-Einstein condensation for an ideal Bose gas and for a dilute weakly interacting Bose gas in a manifold with non-negative Ricci curvature is investigated using the heat kernel and eigenvalue estimates of the Laplace operator. The main focus is on the nonrelativistic gas. However, special relativistic ideal gas is also discussed. The thermodynamic limit of the heat kernel and eigenvalue estimates is taken and the results are used to derive bounds for the depletion coefficient. In the case of a weakly interacting gas, Bogoliubov approximation is employed. The ground state is analyzed using heat kernel methods and finite size effects on the ground state energy are proposed. The justification of the c-number substitution on a manifold is given.
Metastable quantum phase transitions in a periodic one-dimensional Bose gas. II. Many-body theory
Kanamoto, R.; Carr, L. D.; Ueda, M.
2010-02-15
We show that quantum solitons in the Lieb-Liniger Hamiltonian are precisely the yrast states. We identify such solutions with Lieb's type II excitations from weak to strong interactions, clarifying a long-standing question of the physical meaning of this excitation branch. We demonstrate that the metastable quantum phase transition previously found in mean-field analysis of the weakly interacting Lieb-Liniger Hamiltonian [Phys. Rev. A 79, 063616 (2009)] extends into the medium- to strongly interacting regime of a periodic one-dimensional Bose gas. Our methods are exact diagonalization, finite-size Bethe ansatz, and the boson-fermion mapping in the Tonks-Girardeau limit.
Rezende, Sergio M.
2009-09-01
A magnon gas in a film of yttrium iron garnet driven by microwave radiation exhibits Bose-Einstein condensation (BEC) when the driving power exceeds a critical value. We show that the nature and the critical exponents of the BEC transition change dramatically if the BEC magnons are significantly coupled to the zone-center magnons. The theoretical results explain the diverse behavior of the order parameter inferred from the experimental data for the light scattering and the microwave emission from the BEC observed with coherent and incoherent microwave pumping.
Mott-insulator transition in a two-dimensional atomic Bose gas.
Spielman, I B; Phillips, W D; Porto, J V
2007-02-23
Cold atoms in periodic potentials are versatile quantum systems for implementing simple models prevalent in condensed matter theory. Here we realize the 2D Bose-Hubbard model by loading a Bose-Einstein condensate into an optical lattice, and study the resulting Mott insulator. The measured momentum distributions agree quantitatively with theory (no adjustable parameters). In these systems, the Mott insulator forms in a spatially discrete shell structure which we probe by focusing on correlations in atom shot noise. These correlations show a marked dependence on the lattice depth, consistent with the changing size of the insulating shell expected from simple arguments.
NASA Astrophysics Data System (ADS)
Pires, M. O. C.; de Passos, E. J. V.
2017-02-01
We develop the Hartree-Fock-Bogoliubov theory at finite temperature for Bose gas trapped in the two-dimensional optical lattice with the on-site energy low enough that the gas presents superfluid properties. We obtain the condensate density as function of the temperature neglecting the anomalous density in the thermodynamics equation. The condensate fraction provides two critical temperature. Below the temperature T_{C1}, there is one condensate fraction. Above two condensate fractions merger up to the critical temperature T_{C2}. At temperatures larger than T_{C2}, the condensate fraction is null and, therefore, the gas is normal fluid. We resume by a finite-temperature phase diagram where three domains can be identified: the normal fluid, the superfluid with one stable condensate fraction and the superfluid with two condensate fractions being unstable one of them.
The effect of dilution on the gas retention behavior of Tank 241-SY- 103 waste
Bredt, P.R.; Tingey, S.M.
1996-01-01
Twenty-five of the 177 underground waste storage tanks on the Hanford Site have been placed on the Flammable Gas watch list. These 25 tanks, containing high-level waste generated during plutonium and uranium processing, have been identified as potentially capable of accumulating flammable gases above the lower flammability limit (Babad et al. 1991). In the case of Tanks 241-SY-101 and 241-SY-103, it has been proposed that diluting the tank waste may mitigate this hazard (Hudson et al. 1995; Stewart et al. 1994). The effect of dilution on the ability of waste from Tank 241-SY-103 to accumulate gas was studied at Pacific Northwest National Laboratory. A similar study has been completed for waste from Tank 241-SY-101 (Bredt et al. 1995). Because of the additional waste-storage volume available in Tank 241-SY-103 and because the waste is assumed to be similar to that currently in Tank 241-SY-101, Tank 241-SY-103 became the target for a demonstration of passive mitigation through in-tank dilution. In 1994, plans for the in-tank dilution demonstration were deferred pending a decision on whether to pursue dilution as a mitigation strategy. However, because Tank 241-SY-103 is an early retrieval target, determination of how waste properties vary with dilution will still be required.
Heat transfer coefficients of dilute flowing gas-solids suspensions
NASA Technical Reports Server (NTRS)
Kane, R. S.; Pfeffer, R.
1973-01-01
Heat transfer coefficients of air-glass, argon-glass, and argon-aluminum suspensions were measured in horizontal and vertical tubes. The glass, 21.6 and 36.0 micron diameter particles, was suspended at gas Reynolds numbers between 11,000 and 21,000 and loading ratios between 0 and 2.5. The presence of particles generally reduced the heat transfer coefficient. The circulation of aluminum powder in the 0.870 inch diameter closed loop system produced tenacious deposits on protuberances into the stream. In the vertical test section, the Nusselt number reduction was attributed to viscous sublayer thickening; in the horizontal test section to particle deposition.
Application of the Lagrangian variational method to a one-dimensional Bose gas in a dimple trap
NASA Astrophysics Data System (ADS)
Sakhel, Roger R.; Sakhel, Asaad R.
2017-05-01
We present an application of the Lagrangian variational method (LVM) to study the small-oscillation dynamics and ground-state properties of an interacting Bose gas in a one-dimensional dimple trap, for the first time. For this purpose, a Gaussian wavefunction ansatz—rich in variational parameters—is used for the analytical solutions of the equations of motion resulting from the LVM. The results of LVM are found to agree well with those due to the numerical Crank-Nicolson method. The strength of this method is shown to reveal details hidden in the wavefunction and its dynamics that are otherwise hard to obtain numerically or even experimentally. In this regard, the important role that the wavefunction-width plays in determining the properties of a trapped Bose gas is manifested. Via this method, the dependence of the breathing-mode frequency on the interactions, width of wavefunction, and dimple trap parameters, is demonstrated. A significant result is that in the ‘width-space’ of the wavefunction, the LVM yields a differential equation that describes the motion of a fictitious particle in an effective potential whose shape is by analogy similar to that of an interatomic interaction potential.
P-wave superfluid in a quasi-two-dimensional dipolar Bose-Fermi quantum gas mixture
NASA Astrophysics Data System (ADS)
Kain, Ben; Ling, Hong
2013-03-01
The p-wave (px + ipy) superfluid has attracted significant attention in recent years mainly because its vortex core supports a Majorana fermion which, due to its non-Abelian statistics, can be explored for implementing topological quantum computation (TQC). Mixing in bosons may lead to p-wave pairing in a Fermi gas. In a dipolar condensate, the dipole-dipole interaction represents a control knob inaccessible to nondipolar Bosons. Thus, mixing dipolar bosons with fermions opens up new possibilities. We consider a mixture of a spin-polarized Fermi gas and a dipolar Bose-Einstein condensate in a quasi-two-dimensional trap setting. We take the Hartree-Fock-Bogoliubov mean-field approach and develop a theory for studying the stability of the mixture and estimating the critical temperature of the p-wave superfluid. We use this theory to identify the experimentally accessible parameter space in which the mixture is stable against phase separation and the p-wave superfluid pairing can be resonantly enhanced. An enhanced p-wave superfluid order parameter can make the fault tolerant TQC less susceptible to thermal fluctuations. This work aims to stimulate experimental activity in creating dipolar Bose-Fermi mixtures. This work is supported by the US National Science Foundation and the US Army Research Office
FK-DLR properties of a quantum multi-type Bose-gas with a repulsive interaction
Suhov, Y.; Stuhl, I.
2014-08-01
The paper extends earlier results from Suhov and Kelbert [“FK-DLR states of a quantum Bose-gas with a hardcore interaction,” http://arxiv.org/abs/arXiv:1304.0782 ] and Suhov et al. [“Shift-invariance for FK-DLR states of a 2D quantum Bose-gas,” http://arxiv.org/abs/arXiv:1304.4177 ] about infinite-volume quantum bosonic states (FK-DLR states) to the case of multi-type particles with non-negative interactions. (An example is a quantum Widom–Rowlinson model.) Following the strategy from Suhov and Kelbert and Suhov et al., we establish that, for the values of fugacity zϵ(0, 1) and inverse temperature β > 0, finite-volume Gibbs states form a compact family in the thermodynamic limit. Next, in dimension two we show that any limit-point state (an FK-DLR state in the terminology adopted in Suhov and Kelbert and Suhov et al.) is translation-invariant.
A van der Waals Equation of State for a Dilute Boson Gas
ERIC Educational Resources Information Center
Deeney, F. A.; O'Leary, J. P.
2012-01-01
An equation of state of a system is a relationship that connects the thermodynamic variables of the system such as pressure and temperature. Such equations are well known for classical gases but less so for quantum systems. In this paper we develop a van der Waals equation of state for a dilute boson gas that may be used to explain the occurrence…
A van der Waals Equation of State for a Dilute Boson Gas
ERIC Educational Resources Information Center
Deeney, F. A.; O'Leary, J. P.
2012-01-01
An equation of state of a system is a relationship that connects the thermodynamic variables of the system such as pressure and temperature. Such equations are well known for classical gases but less so for quantum systems. In this paper we develop a van der Waals equation of state for a dilute boson gas that may be used to explain the occurrence…
NASA Astrophysics Data System (ADS)
Lin, Bihong; Chen, Jincan
2008-05-01
An irreversible model of the Carnot cryogenic refrigeration cycle working with an ideal Bose or Fermi gas is established, which is composed of two irreversible adiabatic and two isothermal processes. The effects of the quantum degeneracy of the working substance, the irreversibility of the finite-rate heat transfer between the working fluid and the heat reservoirs, and the internal irreversibility in two adiabatic processes on the optimum performance characteristics of the quantum refrigeration cycle are analyzed. The performance characteristics of the cycle in strong and weak gas degeneracy cases are discussed. Expressions for several important performance parameters such as the coefficient of performance, cooling rate and power input are derived. By using numerical solutions, the cooling rate of the cycle is optimized for a given power input. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal regions of the coefficient of performance and power input are determined. Some optimum criteria are given.
Jacqmin, Thibaut; Armijo, Julien; Bouchoule, Isabelle; Berrada, Tarik; Kheruntsyan, Karen V.
2011-06-10
We report on local, in situ measurements of atom number fluctuations in slices of a one-dimensional Bose gas on an atom chip setup. By using current modulation techniques to prevent cloud fragmentation, we are able to probe the crossover from weak to strong interactions. For weak interactions, fluctuations go continuously from super- to sub-Poissonian as the density is increased, which is a signature of the transition between the subregimes where the two-body correlation function is dominated, respectively, by thermal and quantum contributions. At stronger interactions, the super-Poissonian region disappears, and the fluctuations go directly from Poissonian to sub-Poissonian, as expected for a ''fermionized'' gas.
Jacqmin, Thibaut; Armijo, Julien; Berrada, Tarik; Kheruntsyan, Karen V; Bouchoule, Isabelle
2011-06-10
We report on local, in situ measurements of atom number fluctuations in slices of a one-dimensional Bose gas on an atom chip setup. By using current modulation techniques to prevent cloud fragmentation, we are able to probe the crossover from weak to strong interactions. For weak interactions, fluctuations go continuously from super- to sub-Poissonian as the density is increased, which is a signature of the transition between the subregimes where the two-body correlation function is dominated, respectively, by thermal and quantum contributions. At stronger interactions, the super-Poissonian region disappears, and the fluctuations go directly from Poissonian to sub-Poissonian, as expected for a "fermionized" gas.
Reaction of trace mercury in natural gas with dilute polysulfide solutions in a packed column
Not Available
1991-12-01
This paper reports that the natural gas produced around the world can contain traces of mercury which have to be removed. It is difficult to purify gas to desired mercury levels using conventional techniques. By scrubbing with dilute polysulfide solution, the residual mercury in the gas can be removed from about 0.1 to below 0.01 ppb, a reduction of 90%. In this system, the gas is passed through a packed tower wetted with a solution containing 3 ppm of polysulfide salt. Stainless steel packings are effective for this application. In addition to promoting gas-liquid contact, the stainless steel packings adsorb and concentrate polysulfides which react with Hg in the gas to form insoluble HgS, and thus remove Hg from the gas.
Phases of a two-dimensional bose gas in an optical lattice.
Jiménez-García, K; Compton, R L; Lin, Y-J; Phillips, W D; Porto, J V; Spielman, I B
2010-09-10
Ultracold atoms in optical lattices realize simple condensed matter models. We create an ensemble of ≈60 harmonically trapped 2D Bose-Hubbard systems from a 87Rb Bose-Einstein condensate in an optical lattice and use a magnetic resonance imaging approach to select a few 2D systems for study, thereby eliminating ensemble averaging. Our identification of the transition from superfluid to Mott insulator, as a function of both atom density and lattice depth, is in excellent agreement with a universal state diagram [M. Rigol, Phys. Rev. A 79 053605 (2009)] suitable for our trapped system. In agreement with theory, our data suggest a failure of the local density approximation in the transition region.
Loading and compression of a single two-dimensional Bose gas in an optical accordion
NASA Astrophysics Data System (ADS)
Ville, J. L.; Bienaimé, T.; Saint-Jalm, R.; Corman, L.; Aidelsburger, M.; Chomaz, L.; Kleinlein, K.; Perconte, D.; Nascimbène, S.; Dalibard, J.; Beugnon, J.
2017-01-01
The experimental realization of two-dimensional (2D) Bose gases with a tunable interaction strength is an important challenge for the study of ultracold quantum matter. Here we report on the realization of an optical accordion creating a lattice potential with a spacing that can be dynamically tuned between 11 and 2 μ m . We show that we can load ultracold 87Rb atoms into a single node of this optical lattice in the large spacing configuration and then decrease nearly adiabatically the spacing to reach a strong harmonic confinement with frequencies larger than ωz/2 π =10 kHz. Atoms are trapped in an additional flat-bottom in-plane potential that is shaped with a high resolution. By combining these tools we create custom-shaped uniform 2D Bose gases with tunable confinement along the transverse direction and hence with a tunable interaction strength.
Quenching to unitarity: Quantum dynamics in a 3D Bose gas
NASA Astrophysics Data System (ADS)
Sykes, Andrew; Corson, John; D'Incao, Jose; Koller, Andrew; Bohn, John; Rey, Ana Maria; Hazzard, Kaden; Greene, Chris
2014-03-01
We study the dynamics of a zero temperature Bose condensate following a sudden quench of the scattering length from noninteracting to unitarity (infinite scattering length). In this talk we discuss how a qualitative understanding of the dynamics can be built up by understanding few-body physics under the same dynamical scenario. We calculate the coherent evolution of the momentum distribution, particularly focusing on the time dependence of the contact. By comparing the results to a many-body mean-field calculation, we gauge the qualitative and quantitative accuracy of this approach. We then discuss the results of a three-body calculation, in which loss dynamics occurs due to three-body recombination. One the key results of this work indicates that loss dynamics takes place over a much longer timescale than the coherent dynamics. This exciting result supports the idea that meta-stable degenerate unitary Bose gases may be experimentally observable in such a non-equilibrium scenario.
Condensate fraction in a 2D Bose gas measured across the Mott-insulator transition.
Spielman, I B; Phillips, W D; Porto, J V
2008-03-28
We realize a single-band 2D Bose-Hubbard system with Rb atoms in an optical lattice and measure the condensate fraction as a function of lattice depth, crossing from the superfluid to the Mott-insulating phase. We quantitatively identify the location of the superfluid to normal transition by observing when the condensed fraction vanishes. Our measurement agrees with recent quantum Monte Carlo calculations for a finite-sized 2D system to within experimental uncertainty.
Ramsey Interferometry Using the Zeeman Sublevels in a Spin-2 Bose Gas
NASA Astrophysics Data System (ADS)
Sadgrove, Mark; Eto, Yujiro; Sekine, Sawako; Suzuki, Hirosuke; Hirano, Takuya
2013-09-01
We perform atom interferometry using the Zeeman sublevels of a spin-2 Bose--Einstein condensate of 87Rb. The observed fringes are strongly peaked, and fringe repetition rates higher than the fundamental Ramsey frequency are found in agreement with a simple theory based on spin rotations. With a suitable choice of initial states, the interferometer could function as a useful tool for magnetometry and studies of spinor dynamics in general.
NASA Astrophysics Data System (ADS)
Akhoundi, A.; Foroutan, G.
2017-05-01
The effects of gas dilution on the chemistry of macromolecules and nucleation of nanoparticles in a low pressure radio-frequency acetylene discharge are investigated by employing a self-consistent, one dimensional multi-fluid model. Ar, He, and H2 are used for the dilution with different percentages, keeping the total gas inlet constant. The results of numerical simulations showed that the nucleation rate decreases monotonically with H2 fraction, when the plasma is diluted in hydrogen. But, for Ar and He diluted plasmas, the nucleation increases with increasing of the dilution up to 40%, and then declines. Diluting acetylene in Ar increases the electron number density and consequently the rate of electron impact hydrocarbon dissociation, the latter in turn leads to a more effective polymerization and nanoparticle nucleation. Radicals are identified as the most important species during the nucleation process and their number density is always higher in Ar diluted plasma than the other two.
Choi, S; Dunjko, V; Zhang, Z D; Olshanii, M
2015-09-11
Using a time-dependent modified nonlinear Schrödinger equation (MNLSE)-where the conventional chemical potential proportional to the density is replaced by the one inferred from Lieb-Liniger's exact solution-we study frequencies of the collective monopole excitations of a one-dimensional Bose gas. We find that our method accurately reproduces the results of a recent experimental study [E. Haller et al., Science 325, 1224 (2009)] in the full spectrum of interaction regimes from the ideal gas, through the mean-field regime, through the mean-field Thomas-Fermi regime, all the way to the Tonks-Giradeau gas. While the former two are accessible by the standard time-dependent NLSE and inaccessible by the time-dependent local density approximation, the situation reverses in the latter case. However, the MNLSE is shown to treat all these regimes within a single numerical method.
Numerical investigation of enhanced dilution zone mixing in a reverse flow gas turbine combustor
NASA Astrophysics Data System (ADS)
Crocker, D. S.; Smith, C. E.
1995-04-01
An advanced method for dilution zone mixing in a reverse flow gas turbine combustor was numerically investigated. For long mixing lengths associated with reverse flow combustors (X/H greater than 2.0), pattern factor was found to be mainly driven by nozzle-to-nozzle fuel flow and/or circumferential airflow variations; conventional radially injected dilution jets could not effectively mix out circumferential nonuniformities. To enhance circumferential mixing, dilution jets were angled to produce a high circumferential (swirl) velocity component. The jets on the outer liner were angled in one direction while the jets on the inner liner were angled in the opposite direction, thus enhancing turbulent shear at the expense of jet penetration. Three-dimensional CFD calculations were performed on a three-nozzle (90 deg) sector, with different fuel flow from each nozzle (90, 100, and 110% of design fuel flow). The computations showed that the optimum configuration of angled jets reduced the pattern factor by 60% compared to an existing conventional dilution hole configuration. The radial average temperature profile was adequately controlled by the inner-to-outer liner dilution flow split.
Su, Yuanyuan; Irwin, Jimmy A.
2013-03-20
The measured emission-weighted metal abundance of the hot gas in early-type galaxies has been known to be lower than theoretical expectations for 20 years. In addition, both X-ray luminosity and metal abundance vary significantly among galaxies of similar optical luminosities. This suggests some missing factors in the galaxy evolution process, especially the metal enrichment process. With Chandra and XMM-Newton, we studied 32 early-type galaxies (kT {approx}< 1 keV) covering a span of two orders of L{sub X,gas}/L{sub K} to investigate these missing factors. Contrary to previous studies that X-ray faint galaxies show extremely low Fe abundance ({approx}0.1 Z{sub Sun }), nearly all galaxies in our sample show an Fe abundance at least 0.3 Z{sub Sun }, although the measured Fe abundance difference between X-ray faint and X-ray bright galaxies remains remarkable. We investigated whether this dichotomy of hot gas Fe abundances can be related to the dilution of hot gas by mixing with cold gas. With a subset of 24 galaxies in this sample, we find that there is virtually no correlation between hot gas Fe abundances and their atomic gas content, which disproves the scenario that the low metal abundance of X-ray faint galaxies might be a result of the dilution of the remaining hot gas by pristine atomic gas. In contrast, we demonstrate a negative correlation between the measured hot gas Fe abundance and the ratio of molecular gas mass to hot gas mass, although it is unclear what is responsible for this apparent anti-correlation. We discuss several possibilities including that externally originated molecular gas might be able to dilute the hot gas metal content. Alternatively, the measured hot gas Fe abundance may be underestimated due to more complex temperature and abundance structures and even a two-temperature model might be insufficient to reflect the true value of the emission weighted mean Fe abundance.
Excitation dynamics in a lattice Bose gas within the time-dependent Gutzwiller mean-field approach
Krutitsky, Konstantin V.; Navez, Patrick
2011-09-15
The dynamics of the collective excitations of a lattice Bose gas at zero temperature is systematically investigated using the time-dependent Gutzwiller mean-field approach. The excitation modes are determined within the framework of the linear-response theory as solutions of the generalized Bogoliubov-de Gennes equations valid in the superfluid and Mott-insulator phases at arbitrary values of parameters. The expression for the sound velocity derived in this approach coincides with the hydrodynamic relation. We calculate the transition amplitudes for the excitations in the Bragg scattering process and show that the higher excitation modes make significant contributions. We simulate the dynamics of the density perturbations and show that their propagation velocity in the limit of week perturbation is satisfactorily described by the predictions of the linear-response analysis.
Collapse and revival of the monopole mode of a degenerate Bose gas in an isotropic harmonic trap
NASA Astrophysics Data System (ADS)
Straatsma, C. J. E.; Colussi, V. E.; Davis, M. J.; Lobser, D. S.; Holland, M. J.; Anderson, D. Z.; Lewandowski, H. J.; Cornell, E. A.
2016-10-01
We study the monopole (breathing) mode of a finite temperature Bose-Einstein condensate in an isotropic harmonic trap recently developed by Lobser et al. [Nat. Phys. 11, 1009 (2015), 10.1038/nphys3491]. We observe a nonexponential collapse of the amplitude of the condensate oscillation followed by a partial revival. This behavior is identified as being due to beating between two eigenmodes of the system, corresponding to in-phase and out-of-phase oscillations of the condensed and noncondensed fractions of the gas. We perform finite temperature simulations of the system dynamics using the Zaremba-Nikuni-Griffin methodology [J. Low Temp. Phys. 116, 277 (1999), 10.1023/A:1021846002995], and find good agreement with the data, thus confirming the two mode description.
Rezende, Sergio M.
2009-05-01
Strong experimental evidences of the formation of quasiequilibrium Bose-Einstein condensation (BEC) of magnons at room temperature in a film of yttrium iron garnet (YIG) excited by microwave radiation have been recently reported. Here we present a theory for the dynamics of the magnon gas driven by a microwave field far out of equilibrium that provides rigorous support for the formation of a BEC of magnons in a YIG film magnetized in the plane. We show that if the microwave driving power exceeds a threshold value the nonlinear magnetic interactions create cooperative mechanisms for the onset of a phase transition leading to the spontaneous generation of quantum coherence and magnetic dynamic order in a macroscopic scale. The theoretical results agree with the experimental data for the intensity and the decay rate of the Brillouin light scattering from the BEC as a function of power and for the microwave emission from the uniform mode generated by the confluence of BEC magnon pairs.
Transport of a Bose gas in 1D disordered lattices at the fluid-insulator transition.
Tanzi, Luca; Lucioni, Eleonora; Chaudhuri, Saptarishi; Gori, Lorenzo; Kumar, Avinash; D'Errico, Chiara; Inguscio, Massimo; Modugno, Giovanni
2013-09-13
We investigate the momentum-dependent transport of 1D quasicondensates in quasiperiodic optical lattices. We observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. In the limit of nondisordered lattices the observations suggest a contribution of quantum phase slips to the dissipation. We identify a set of critical disorder and interaction strengths for which such critical momentum vanishes, separating a fluid regime from an insulating one. We relate our observation to the predicted zero-temperature superfluid-Bose glass transition.
Exponents of the spectral functions and dynamical structure factor of the 1D Lieb-Liniger Bose gas
NASA Astrophysics Data System (ADS)
Carmelo, J. M. P.; Sacramento, P. D.
2016-06-01
We study the (k , ω) -plane finite-energy line shape of the zero-temperature one-boson removal spectral function (ω < 0) , one-boson addition spectral function (ω > 0) , and charge dynamical structure factor (ω > 0) of the 1D Lieb-Liniger Bose gas with repulsive boson interaction c > 0. Our analysis of the problem focuses on the line shape at finite excitation energies in the vicinity of these functions spectrum upper (ω < 0) or lower (ω > 0) threshold. Specifically, we derive the exact momentum, interaction, and density dependences of the exponents controlling such a line shape in each of the N = 1 , 2 , 3 , … momentum subdomains k ∈ [(N - 1) 2 πn , N 2 πn ] . Here n = N / L is the boson density, N the boson number, and L the system length. In the thermodynamic limit considered in our study nearly all spectral weight of the dynamical correlation functions is for large values of n / c contained in the N = 1 momentum subdomain k ∈ [ 0 , 2 πn ] . As n / c decreases a small fraction of that weight is transferred to the remaining set of N = 2 , 3 , 4 , … momentum subdomains, particularly to the N = 2 subdomain. In the case of the momentum subdomain k ∈ [ 0 , 2 πn ] , our exact results agree with those of previous studies. For that subdomain the above exponents are plotted as a function of the momentum for several n / c values. Our derivation of the line shapes of the three dynamical correlation functions relies on the use of a simplified form of the pseudofermion dynamical theory of the fermionic 1D Hubbard model suitably modified in this paper for the 1D Bose gas.
El-Sherbini, Th.M.
2005-03-17
This article gives a brief review of Bose-Einstein condensation. It is an exotic quantum phenomenon that was observed in dilute atomic gases for the first time in 1995. It exhibits a new state of matter in which a group of atoms behaves as a single particle. Experiments on this form of matter are relevant to many different areas of physics- from atomic clocks and quantum computing to super fluidity, superconductivity and quantum phase transition.
Einstein, Bose and Bose-Einstein Statistics
NASA Astrophysics Data System (ADS)
Wali, Kameshwar C.
2005-05-01
In June 1924, a relatively unknown Satyendra Nath Bose from Dacca, India, wrote a letter to Einstein beginning with ``Respected Sir, I have ventured to send you the accompanying article for your perusal. I am anxious to know what you think of it. You will see that I have ventured to deduce the coefficient 8πυ^2/c^3 in Planck's law independent of the classical electrodynamics, only assuming that the ultimate elementary regions in Phase-space have the content h^3. I do not know sufficient German to translate the paper. If you think the paper worth publication, I shall be grateful if you arrange for its publication in Zeitschrift für Physik.'' Einstein did translate the article himself and got it published. He wrote to Ehrenfest: ``The Indian Bose has given a beautiful derivation of Planck's law, including the constant [i.e.8πυ^2/c^3].'' Einstein extended the ideas of Bose that implied, among other things, a new statistics for the light-quanta to the molecules of an ideal gas and wrote to Ehrenfest, `from a certain temperature on, the molecules ``condense'' without attractive forces, that is, they accumulate at zero velocity. The theory is pretty, but is there also some truth to it?' Abraham Pais has called Bose's paper ``the fourth and the last revolutionary papers of the old quantum theory.'' My paper will present the works of Bose and Einstein in their historical perspective and the eventual birth of the new quantum Bose-Einstein statistics.
Equation of state of a polarized Fermi gas in the Bose-Einstein-condensate limit
Alzetto, F.; Leyronas, X.
2010-04-15
We present a theoretical study of the BEC-BCS crossover in the Bose-Einstein-condensate (BEC) regime in the case of an unequal number of fermions of two species. We take full account of the composite nature of the dimers made of fermions. In the limit of low densities, we calculate the ground-state energy of the system, or equivalently the chemical potentials of each species, as well as the one-particle gap and the energy of an 'impurity' immersed in a Fermi sea. For the chemical potentials we go up to order (density){sup 4/3}. The results found involve the exact atom-dimer a{sub AD} and dimer-dimer a{sub DD} scattering lengths and therefore include the three- and four-body problems in the many-body problem. We briefly comment on the importance of the different mean-field corrections for recent experiments.
Half-quantum vortex molecules in a binary dipolar Bose gas.
Shirley, Wilbur E; Anderson, Brandon M; Clark, Charles W; Wilson, Ryan M
2014-10-17
We study the ground state phases of a rotating two-component, or binary, Bose-Einstein condensate, wherein one component possesses a large permanent magnetic dipole moment. A variety of nontrivial phases emerge in this system, including a half-quantum vortex (HQV) chain phase and a HQV molecule phase, where HQVs bind at short distances. We attribute these phases to the development of a minimum in the HQV interaction potential, which emerges without coherent coupling or attractive interactions between the components. Thus, we show that the presence of dipolar interactions in this system provides a unique mechanism for the formation of HQV molecules and results in a rich ground state phase diagram.
Quenching to unitarity: Quantum dynamics in a three-dimensional Bose gas
NASA Astrophysics Data System (ADS)
Sykes, A. G.; Corson, J. P.; D'Incao, J. P.; Koller, A. P.; Greene, C. H.; Rey, A. M.; Hazzard, K. R. A.; Bohn, J. L.
2014-02-01
We study the dynamics of a zero-temperature Bose condensate following a sudden quench of the scattering length from noninteracting to unitarity (infinite scattering length). We apply three complementary approaches to understand the momentum distribution and loss rate. First, using a time-dependent variational ansatz for the many-body state, we calculate the dynamics of the momentum distribution. Second, we demonstrate that, at short times and large momenta compared to those set by the density, the physics can be understood within a simple, analytic two-body model. We make a quantitative prediction for the evolution of Tan's contact and find features in the momentum distribution that are absent in equilibrium. Third, we study three-body loss at finite density under the same dynamic scenario. We find lifetimes that are long compared to the saturation times of large-momentum modes, and we relate this result to the three-body inelasticity parameter.
Observation of a Rosensweig Instability and Stable Quantum Droplets in a Dipolar Bose Gas
NASA Astrophysics Data System (ADS)
Pfau, Tilman; Ferrier Barbut, Igor; Kadau, Holger; Schmitt, Matthias; Wenzel, Matthias
2016-05-01
Ferrofluids show unusual hydrodynamic effects due to the magnetic nature of their constituents. For increasing magnetization a classical ferrofluid undergoes a Rosensweig instability and creates self-organized ordered surface structures or droplet crystals. We observe a related instability in a Bose-Einstein condensate with strong dipolar interactions resulting in surprisingly stable droplet crystals. We find that quantum fluctuations which are the origin of genuine quantum many-body effects cannot be neglected and provide a stabilizing mechanism. We study experimentally individual stable quantum droplets containing about 800 atoms which are expected to collapse at the mean-field level due to the essentially attractive interaction. By systematic measurements on individual droplets we demonstrate quantitatively that quantum fluctuations stabilize them against the mean-field collapse. We observe in addition interference of several droplets indicating that this stable many-body state is phase coherent.
Guerra, Carlos
2017-01-01
In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires) as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i) the gas diffusion coefficient inside such arrays, (ii) the time between collisions of molecules with the nanocylinder walls (mean time of flight), (iii) the surface impingement rate, and (iv) the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport. It can be specifically shown that the gas diffusion coefficient inside such arrays is inversely proportional to the areal density of cylinders and their mean diameter. An example calculation of a diffusion coefficient is delivered for a system of titanium isopropoxide molecules diffusing between vertically aligned carbon nanotubes. Our findings are important for the correct modelling and optimisation of gas-based deposition techniques, such as atomic layer deposition or chemical vapour deposition, frequently used for surface functionalisation of high-aspect-ratio nanocylinder arrays in solar cells and energy storage applications. Furthermore, gas sensing devices with high-aspect-ratio nanocylinder arrays and the growth of vertically aligned carbon nanotubes need the fundamental understanding and precise modelling of gas transport to optimise such processes. PMID:28144565
Szmyt, Wojciech; Guerra, Carlos; Utke, Ivo
2017-01-01
In this work we modelled the diffusive transport of a dilute gas along arrays of randomly distributed, vertically aligned nanocylinders (nanotubes or nanowires) as opposed to gas diffusion in long pores, which is described by the well-known Knudsen theory. Analytical expressions for (i) the gas diffusion coefficient inside such arrays, (ii) the time between collisions of molecules with the nanocylinder walls (mean time of flight), (iii) the surface impingement rate, and (iv) the Knudsen number of such a system were rigidly derived based on a random-walk model of a molecule that undergoes memoryless, diffusive reflections from nanocylinder walls assuming the molecular regime of gas transport. It can be specifically shown that the gas diffusion coefficient inside such arrays is inversely proportional to the areal density of cylinders and their mean diameter. An example calculation of a diffusion coefficient is delivered for a system of titanium isopropoxide molecules diffusing between vertically aligned carbon nanotubes. Our findings are important for the correct modelling and optimisation of gas-based deposition techniques, such as atomic layer deposition or chemical vapour deposition, frequently used for surface functionalisation of high-aspect-ratio nanocylinder arrays in solar cells and energy storage applications. Furthermore, gas sensing devices with high-aspect-ratio nanocylinder arrays and the growth of vertically aligned carbon nanotubes need the fundamental understanding and precise modelling of gas transport to optimise such processes.
NASA Astrophysics Data System (ADS)
Gavrilik, A. M.; Mishchenko, Yu. A.
2014-11-01
We establish the relation of the second virial coefficient of a recently proposed (μ ˜,q ) -deformed Bose gas model [A. M. Gavrilik and Yu. A. Mishchenko, Ukr. J. Phys. 58, 1171 (2013)] to the interaction and compositeness parameters when either of these factors is taken into account separately. When the interaction is dealt with, the deformation parameter becomes linked directly to the scattering length and the effective radius of interaction (in general, to scattering phases). The additionally arising temperature dependence is a feature absent in the deformed Bose gas model within the adopted interpretation of the deformation parameters μ ˜ and q . Here the problem of the temperature dependence is analyzed in detail and its possible solution is proposed.
Gavrilik, A M; Mishchenko, Yu A
2014-11-01
We establish the relation of the second virial coefficient of a recently proposed (μ[over ̃],q)-deformed Bose gas model [A. M. Gavrilik and Yu. A. Mishchenko, Ukr. J. Phys. 58, 1171 (2013)] to the interaction and compositeness parameters when either of these factors is taken into account separately. When the interaction is dealt with, the deformation parameter becomes linked directly to the scattering length and the effective radius of interaction (in general, to scattering phases). The additionally arising temperature dependence is a feature absent in the deformed Bose gas model within the adopted interpretation of the deformation parameters μ[over ̃] and q. Here the problem of the temperature dependence is analyzed in detail and its possible solution is proposed.
Richtmyer-Meshkov instability in dilute gas-particle mixtures with re-shock
NASA Astrophysics Data System (ADS)
Schulz, J. C.; Gottiparthi, K. C.; Menon, S.
2013-11-01
The Richtmyer-Meshkov instability (RMI) is investigated in a dilute gas-particle mixture using three-dimensional numerical simulations. This work extends an earlier two-dimensional study [S. Ukai, K. Balakrishnan, and S. Menon, "On Richtmyer-Meshkov instability in dilute gas-particle mixtures," Phys. Fluids 22, 104103 (2010)] to a larger parameter space consisting of variations in the mass loading and the particle size as well as considering both single-mode and multi-mode interface initializations. In addition, the effect of the presence of particles on re-shock RMI is also investigated. Single-phase numerical predictions of the mixing layer growth-rate are shown to compare well to both experimental and theoretical results. In a dilute gas-particle mixture, the initial growth-rate of RMI shows similar trends compared to previous work; however, the current numerical predictions show that there is an observable increase, not previously predicted, in the growth of the mixing layer at higher mass loadings. For the range of cases considered, an increase as much as 56% is observed. This increase is attributed to additional vorticity production in the mixing layer resulting from inter-phase momentum coupling. Moreover, the presence of particles introduces a continuous drag on the gas-phase resulting in a delay in the time at which re-shock occurs. This delay, which is observed to be as much as 6%, is largest for higher initial mass loadings and smaller particle radii and has a corresponding effect on both the growth-rate of the mixing-layer after re-shock and the final width of the mixing layer. A new semi-analytical correlation is developed and verified against the numerical data to predict the re-shocked RMI growth-rate in dilute gas-particle flows. The correlation shows that the re-shock RMI growth-rate is linearly proportional to the velocity jump at re-shock, the molecular mixing fraction, and the multi-phase Atwood number. Depending on the initial mass loading and
NASA Astrophysics Data System (ADS)
Peletminskii, A. S.; Peletminskii, S. V.; Slyusarenko, Yu V.
2017-07-01
We study a many-body system of interacting fermionic atoms of two species that are in thermodynamic equilibrium with their condensed heteronuclear bound states (molecules). In order to describe such an equilibrium state, we use a microscopic approach that involves the Bogoliubov model for a weakly interacting Bose gas and approximate formulation of the second quantization method in the presence of bound states of particles elaborated earlier by the authors. This microscopic approach is valid at low temperatures, when the average kinetic energy of all the components in the system is small in comparison with the bound state energy. The coupled equations, which relate the chemical potentials of fermionic components and molecular condensate density, are obtained within the proposed theory. At zero temperature, these equations are analyzed both analytically and numerically, attracting the relevant experimental data. We find the conditions at which a condensate of heteronuclear molecules coexists in equilibrium with degenerate components of a Fermi gas. The ground state energy and single-particle excitation spectrum are found. The boundaries of the applicability of the developed microscopic approach are analyzed.
Coupled-cluster theory of a gas of strongly-interacting electrons in the dilute limit
Mihaila, Bodgan; Cardenas, Andres L
2008-01-01
We study the ground-state properties of a dilute gas of strongly-interacting fermions in the framework of the coupled-cluster expansion (CCE). We demonstrate that properties such as universality, opening of a gap in the excitation spectrum and applicability of s-wave approximations appear naturally in the CCE approach. In the zero-density limit, we show that the ground-state energy density depends on only one parameter which in turn may depend at most on the spatial dimensionality of the system.
Sun, Chenhang; Berg, John C
2003-04-15
Inverse gas chromatography (IGC) at infinite dilution has been widely used to access the nonspecific surface free energy of solid materials. Since most practical surfaces are heterogeneous, the effective surface energy given by IGC at infinite dilution is somehow averaged over the whole sample surface, but the rule of averaging has thus far not been established. To address this problem, infinite dilution IGC analysis was carried out on mixtures of known heterogeneity. These materials are obtained by mixing two types of solid particles with significantly different surface energies as characterized individually with IGC, and results are obtained for binary combinations in varying proportions. It is found that when all surface components have the same accessibility by probe molecules, the effective surface energy of such a heterogeneous surface is related to the surface energy distribution by a square root linear relationship, square root sigma(eff)(LW)= summation operator (i)phi(i) square root sigma(i)(LW), where sigma(i)(LW) refers to the nonspecific (Lifshitz-van der Waals) surface energy of patches i, and phi(i) to their area fraction.
Transport of an interacting Bose gas in 1D disordered lattices
D'Errico, C.; Chaudhuri, S.; Gori, L.; Kumar, A.; Lucioni, E.; Tanzi, L.; Inguscio, M.; Modugno, G.
2014-08-20
We use ultracold atoms in a quasiperiodic lattice to study two outstanding problems in the physics of disordered systems: a) the anomalous diffusion of a wavepacket in the presence of disorder, interactions and noise; b) the transport of a disordered superfluid. a) Our results show that the subdiffusion, observed when interaction alone is present, can be modelled with a nonlinear diffusion equation and the peculiar shape of the expanding density profiles can be connected to the microscopic nonlinear diffusion coefficients. Also when noise alone is present we can describe the observed normal diffusion dynamics by existing microscopic models. In the unexplored regime in which noise and interaction are combined, instead, we observe an anomalous diffusion, that we model with a generalized diffusion equation, where noise- and interaction-induced contributions add each other. b) We find that an instability appearing at relatively large momenta can be employed to locate the fluid-insulator crossover driven by disorder. By investigating the momentum-dependent transport, we observe a sharp crossover from a weakly dissipative regime to a strongly unstable one at a disorder-dependent critical momentum. The set of critical disorder and interaction strengths for which such critical momentum vanishes, can be identified with the separation between a fluid regime and an insulating one and can be related to the predicted zero-temperature superfluid-Bose glass transition.
Characteristics of dilute gas-solids suspensions in drag reducing flow
NASA Technical Reports Server (NTRS)
Kane, R. S.; Pfeffer, R.
1973-01-01
Measurements were performed on dilute flowing gas-solids suspensions and included data, with particles present, on gas friction factors, velocity profiles, turbulence intensity profiles, turbulent spectra, and particle velocity profiles. Glass beads of 10 to 60 micron diameter were suspended in air at Reynolds numbers of 10,000 to 25,000 and solids loading ratios from 0 to 4. Drag reduction was achieved for all particle sizes in vertical flow and for the smaller particle sizes in horizontal flow. The profile measurements in the vertical tube indicated that the presence of particles thickened the viscous sublayer. A quantitative theory based on particle-eddy interaction and viscous sublayer thickening has been proposed.
NASA Astrophysics Data System (ADS)
Budiman, Harry; Mulyana, Muhammad Rizky; Zuas, Oman
2017-01-01
Uncertainty estimation for the gravimetric dilution of four calibration gas mixtures [carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) in helium (He) Balance] have been carried out according to the International Organization for Standardization (ISO) of "Guide to the Expression of Uncertainty in Measurement". The uncertainty of the composition of gas mixtures was evaluated to measure the quality, reliability, and comparability of the prepared calibration gas mixtures. The analytical process for the uncertainty estimation is comprised of four main stages such as specification of measurand, identification, quantification of the relevant uncertainty sources, and combination of the individual uncertainty sources. In this study, important uncertainty sources including weighing, gas cylinder, component gas, certified calibration gas mixture (CCGM) added, and purity of the He balance were examined to estimate the final uncertainty of composition of diluted calibration gas mixtures. The results shows that the uncertainties of gravimetric dilution of the four calibration gas mixtures (CO2, CO, and CH4 in He Balance) were found in the range of 5.974% - 7.256% that were expressed as %relative of expanded uncertainty at 95% of confidence level (k=2). The major contribution of sources uncertainty to the final uncertainty arose from the uncertainty related to the certified calibration gas mixture (CCGM) which was the uncertainty value stated in the CCGM certificate. The verification of calibration gas mixtures composition shows that the gravimetric values of calibration gas mixtures were consistent with the results of measurement using gas chromatography flame ionization detector equipped by methanizer.
NASA Astrophysics Data System (ADS)
Parisi, L.; Giorgini, S.
2017-02-01
We present a theoretical study based upon quantum Monte Carlo methods of the Bose polaron in one-dimensional systems with contact interactions. In this instance of the problem of a single impurity immersed in a quantum bath, the medium is a Lieb-Liniger gas of bosons ranging from the weakly interacting to the Tonks-Girardeau regime, whereas the impurity is coupled to the bath via a different contact potential, producing both repulsive and attractive interactions. Both the case of a mobile impurity, having the same mass as the particles in the medium, and the case of a static impurity with infinite mass are considered. We make use of numerical techniques that allow us to calculate the ground-state energy of the impurity, its effective mass, and the contact parameter between the impurity and the bath. These quantities are investigated as a function of the strength of interactions between the impurity and the bath and within the bath. In particular, we find that the effective mass rapidly increases to very large values when the impurity gets strongly coupled to an otherwise weakly repulsive bath. This heavy impurity hardly moves within the medium, thereby realizing the "self-localization" regime of the Landau-Pekar polaron. Furthermore, we compare our results with predictions of perturbation theory valid for weak interactions and with exact solutions available when the bosons in the medium behave as impenetrable particles.
NASA Astrophysics Data System (ADS)
Hanai, R.; Littlewood, P. B.; Ohashi, Y.
2016-05-01
We theoretically investigate a Bose-condensed exciton gas out of equilibrium. Within the framework of the combined BCS-Leggett strong-coupling theory with the non-equilibrium Keldysh formalism, we show how the Bose-Einstein condensation (BEC) of excitons is suppressed to eventually disappear, when the system is in the non-equilibrium steady state. The supply of electrons and holes from the bath is shown to induce quasi-particle excitations, leading to the partial occupation of the upper branch of Bogoliubov single-particle excitation spectrum. We also discuss how this quasi-particle induction is related to the suppression of exciton BEC, as well as the stability of the steady state.
NASA Astrophysics Data System (ADS)
Wali, Kameshwar C.
2005-04-01
In June 1924, a relatively unknown Satyendra Nath Bose from Dacca, India, wrote a letter to Einstein beginning with ``Respected Sir, I have ventured to send you the accompanying article for your perusal. I am anxious to know what you think of it. You will see that I have ventured to deduce the coefficient 8πυ^2/c^3 in Planck's law independent of the classical electrodynamics, only assuming that the ultimate elementary regions in Phase-space have the content h^3. I do not know sufficient German to translate the paper. If you think the paper worth publication, I shall be grateful if you arrange for its publication in Zeitschrift für Physik.'' Einstein did translate the article himself and got it published. He wrote to Ehrenfest: ``The Indian Bose has given a beautiful derivation of Planck's law, including the constant [i.e.8πυ^2/c^3].'' Einstein extended the ideas of Bose that implied, among other things, a new statistics for the light-quanta to the molecules of an ideal gas and wrote to Ehrenfest, `from a certain temperature on, the molecules ``condense'' without attractive forces, that is, they accumulate at zero velocity. The theory is pretty, but is there also some truth to it?' Abraham Pais has called Bose's paper ``the fourth and the last revolutionary papers of the old quantum theory.'' My paper will present the works of Bose and Einstein in their historical perspective and the eventual birth of the new quantum Bose-Einstein statistics.
Fedichev, Petr O; Fischer, Uwe R
2003-12-12
We propose an experimental scheme to observe the Gibbons-Hawking effect in the acoustic analog of a (1+1)-dimensional de Sitter universe, produced in an expanding, cigar-shaped Bose-Einstein condensate. It is shown that a two-level system created at the center of the trap, an atomic quantum dot interacting with phonons, observes a thermal Bose distribution at the de Sitter temperature.
Fan, Wenlai; Qian, Michael C
2005-10-05
The aroma compounds of young and aged Chinese "Yanghe Daqu" liquor samples were extracted by solid phase microextraction (SPME) and analyzed by gas chromatography (GC)-olfactometry dilution analysis. The original liquor samples were diluted with deionized water to give a final alcohol content of 14% (v/v). The samples were stepwise diluted (1:1) with 14% (by volume) ethanol-water solution and then extracted by headspace SPME. The samples were preequilibrated at 50 degrees C for 15 min and extracted with stirring at the same temperature for 30 min prior to injection into GC. The aroma compounds were identified by both GC-MS and GC-olfactometry using DB-Wax and DB-5 columns. The results suggested that esters were the major contributors to Yanghe Daqu liquor aroma. Ethyl hexanoate, ethyl butanoate, and ethyl pentanoate had very high flavor dilution values in both young and aged liquors (FD > 8192). Methyl hexanoate, ethyl heptanoate, ethyl benzoate, and butyl hexanoate could also be very important because of their high flavor dilution values (FD > or = 256). Moreover, two acetals, 1,1-diethoxyethane and 1,1-diethoxy-3-methylbutane, also were shown high flavor dilution values in Yanghe Daqu liquors (FD > or = 256). Other aroma compounds having moderate flavor dilution values included acetaldehyde, 3-methylbutanol, and 2-pentanol (FD > or = 32). Comparing young and aged liquors, the aroma profiles were similar, but the aroma compounds in the aged sample had higher flavor dilution values than in the young ones.
Edwards, Selvin H; Kimberly, Mary M; Pyatt, Susan D; Stribling, Shelton L; Dobbin, Kara D; Myers, Gary L
2011-04-01
Our purpose was to establish a mass spectrometry reference measurement procedure (RMP) for cholesterol to use in the CDC's standardization programs. We explored a gas chromatography-isotope dilution mass spectrometry (GC-IDMS) procedure using a multilevel standard calibration curve to quantify samples with varying cholesterol concentrations. We calibrated the mass spectrometry instrument by isotope dilution with a pure primary standard reference material and an isotopically enriched cholesterol analog as the internal standard (IS). We diluted the serum samples with Tris-HCl buffer (pH 7.4, 0.05 mol/L, 0.25% Triton X-100) before analysis. We used 17 serum pools, 10 native samples, and 2 standard reference materials (SRMs). We compared the GC-IDMS measurements with the CDC's modified Abell-Levy-Brodie-Kendall (AK) RMP measurements and assessed method accuracy by analyzing 2 SRMs. We evaluated the procedure for lack of interference by analyzing serum spiked with a mixture of 7 sterols. The mean percent bias between the AK and the GC-IDMS RMP was 1.6% for all samples examined. The mean percent bias from NIST's RMP was 0.5% for the SRMs. The total %CVs for SRM 1951b levels I and II were 0.61 and 0.73%, respectively. We found that none of the sterols investigated interfered with the cholesterol measurement. The low imprecision, linear response, lack of interferences, and acceptable bias vs the NIST primary RMP qualifies this procedure as an RMP for determining serum cholesterol. The CDC will adopt and implement this GC-IDMS procedure for cholesterol standardization.
NASA Astrophysics Data System (ADS)
Duan-Liang, Xiao; Meng-Yun, Lai; Xiao-Yin, Pan
2016-01-01
We investigate the thermodynamic properties of an ideal charged Bose gas confined in an anisotropic harmonic potential and a constant magnetic field. Using an accurate density of states, we calculate analytically the thermodynamic potential and consequently various intriguing thermodynamic properties, including the Bose-Einstein transition temperature, the specific heat, magnetization, and the corrections to these quantities due to the finite number of particles are also given explicitly. In contrast to the infinite number of particles scenarios, we show that those thermodynamic properties, particularly the Bose-Einstein transition temperature depends upon the strength of the magnetic field due to the finiteness of the particle numbers, and the collective effects of a finite number of particles become larger when the particle number decreases. Moreover, the magnetization varies with the temperature due to the finiteness of the particle number while it keeps invariant in the thermodynamic limit N → ∞. Project supported by the National Natural Science Foundation of China (Grant No. 11375090), and the K. C. Wong Magna Foundation of Ningbo University, China.
Chang Chiachen; Zhang Shiwei; Ceperley, David M.
2010-12-15
Ground-state properties of the repulsive Hubbard model on a cubic lattice are investigated by means of the auxiliary-field quantum Monte Carlo method. We focus on low-density systems with varying on-site interaction U/t, as a model relevant to recent experiments on itinerant ferromagnetism in a dilute Fermi gas with contact interaction. Twist-average boundary conditions are used to eliminate open-shell effects and large lattice sizes are studied to reduce finite-size effects. The sign problem is controlled by a generalized constrained path approximation. We find no ferromagnetic phase transition in this model. The ground-state correlations are consistent with those of a paramagnetic Fermi liquid.
Dilute-gas properties of some systems containing CO/sub 2/
Ameling, W.; Lucas, K.
1987-05-01
The SSR-MPA potential model is used to correlate and extrapolate the dilute-gas properties of some systems containing CO/sub 2/. With parameters determined from a consistent set of second virial and Joule-Thomson data, the third virial coefficient of CO/sub 2/ as well as the second virial coefficients of various mixtures containing CO/sub 2/ can be predicted very well. The Mason-Monchik approximation fails for a complicated molecule such as CO/sub 2/, although at least a viscosity prediction of technical accuracy is obtained. If parameters fitted to the CO/sub 2/ viscosity are used, excellent predictions can be made for the viscosity of gaseous mixtures containing CO/sub 2/.
Schmarr, Hans-Georg; Slabizki, Petra; Legrum, Charlotte
2013-08-01
Trace level analyses in complex matrices benefit from heart-cut multidimensional gas chromatographic (MDGC) separations and quantification via a stable isotope dilution assay. Minimization of the potential transfer of co-eluting matrix compounds from the first dimension ((1)D) separation into the second dimension separation requests narrow cut-windows. Knowledge about the nature of the isotope effect in the separation of labeled and unlabeled compounds allows choosing conditions resulting in at best a co-elution situation in the (1)D separation. Since the isotope effect strongly depends on the interactions of the analytes with the stationary phase, an appropriate separation column polarity is mandatory for an isotopic co-elution. With 3-alkyl-2-methoxypyrazines and an ionic liquid stationary phase as an example, optimization of the MDGC method is demonstrated and critical aspects of narrow cut-window definition are discussed.
NASA Astrophysics Data System (ADS)
Wahl, Christian; Brausemann, Rudolf; Schmitt, Julian; Vewinger, Frank; Christopoulos, Stavros; Weitz, Martin
2016-12-01
Bose-Einstein condensation is a phenomenon well known for material particles as cold atomic gases, and this concept has in recent years been extended to photons confined in microscopic optical cavities. Essential for the operation of such a photon condensate is a thermalization mechanism that conserves the average particle number, as in the visible spectral regime can be realized by subsequent absorption re-emission processes in dye molecules. Here we report on the status of an experimental effort aiming at the extension of the concept of Bose-Einstein condensation of photons towards the vacuum ultraviolet spectral regime, with gases at high-pressure conditions serving as a thermalization medium for the photon gas. We have recorded absorption spectra of xenon gas at up to 30 bar gas pressure of the 5p^6-5p^56s transition with a wavelength close to 147 nm. Moreover, spectra of ethylene noble gas mixtures between 158 and 180 nm wavelength are reported.
Kovalev, Vadim Mikhailovich; Tse, Wang-Kong
2017-09-01
We develop a microscopic theory for the relaxation dynamics of an optically pumped two-level system (TLS) coupled to a bath of weakly interacting Bose gas. Using Keldysh formalism and diagrammatic perturbation theory, expressions for the relaxation times of the TLS Rabi oscillations are derived when the boson bath is in the normal state and the Bose-Einstein condensate (BEC) state. We apply our general theory to consider an irradiated quantum dot coupled with a boson bath consisting of a two-dimensional dipolar exciton gas. When the bath is in the BEC regime, relaxation of the Rabi oscillations is due to both condensate and non-condensate fractions of the bath bosons for weak TLS-light coupling and dominantly due to the non-condensate fraction for strong TLS-light coupling. Our theory also shows that a phase transition of the bath from the normal to the BEC state strongly influences the relaxation rate of the TLS Rabi oscillations. The TLS relaxation rate is approximately independent of the pump field frequency and monotonically dependent on the field strength when the bath is in the low-temperature regime of the normal phase. Phase transition of the dipolar exciton gas leads to a non-monotonic dependence of the TLS relaxation rate on both the pump field frequency and field strength, providing a characteristic signature for the detection of BEC phase transition of the coupled dipolar exciton gas. © 2017 IOP Publishing Ltd.
Satyendranath Bose: Co-Founder of Quantum Statistics
ERIC Educational Resources Information Center
Blanpied, William A.
1972-01-01
Satyendranath Bose was first to prove Planck's Law by using ideal quantum gas. Einstein credited Bose for this first step in the development of quantum statistical mechanics. Bose did not realize the importance of his work, perhaps because of peculiar academic settings in India under British rule. (PS)
Desbuquois, Rémi; Yefsah, Tarik; Chomaz, Lauriane; Weitenberg, Christof; Corman, Laura; Nascimbène, Sylvain; Dalibard, Jean
2014-07-11
We present a general "fit-free" method for measuring the equation of state (EoS) of a scale-invariant gas. This method, which is inspired from the procedure introduced by Ku et al. [Science 335, 563 (2012)] for the unitary three-dimensional Fermi gas, provides a general formalism which can be readily applied to any quantum gas in a known trapping potential, in the frame of the local density approximation. We implement this method on a weakly interacting two-dimensional Bose gas across the Berezinskii-Kosterlitz-Thouless transition and determine its EoS with unprecedented accuracy in the critical region. Our measurements provide an important experimental benchmark for classical-field approaches which are believed to accurately describe quantum systems in the weakly interacting but nonperturbative regime.
NASA Astrophysics Data System (ADS)
Plata, J.
2006-07-01
The effect of magnetic-field modulation on a Fermi gas of atoms in the BCS-BEC crossover is studied analytically. Recent experimental findings on the system response to a sinusoidal variation of the field are explained. Specifically, the dissociation processes induced by the modulation in the Bose-Einstein condensate regime are described. The role played by the frequency, amplitude, and application time of the perturbation in the emergence of the observed behavior is clarified. The results uncover also the relevance of the detuning from the Feshbach resonance to the appearance of particular spectral features. The applicability of the field modulation as a spectroscopic tool for probing the crossover is discussed.
Lattice Boltzmann accelerated direct simulation Monte Carlo for dilute gas flow simulations
NASA Astrophysics Data System (ADS)
Di Staso, G.; Clercx, H. J. H.; Succi, S.; Toschi, F.
2016-11-01
Hybrid particle-continuum computational frameworks permit the simulation of gas flows by locally adjusting the resolution to the degree of non-equilibrium displayed by the flow in different regions of space and time. In this work, we present a new scheme that couples the direct simulation Monte Carlo (DSMC) with the lattice Boltzmann (LB) method in the limit of isothermal flows. The former handles strong non-equilibrium effects, as they typically occur in the vicinity of solid boundaries, whereas the latter is in charge of the bulk flow, where non-equilibrium can be dealt with perturbatively, i.e. according to Navier-Stokes hydrodynamics. The proposed concurrent multiscale method is applied to the dilute gas Couette flow, showing major computational gains when compared with the full DSMC scenarios. In addition, it is shown that the coupling with LB in the bulk flow can speed up the DSMC treatment of the Knudsen layer with respect to the full DSMC case. In other words, LB acts as a DSMC accelerator. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.
Wong, Siu-kay; Yu, Kwok-chiu; Lam, Chi-ho
2010-03-01
This paper presents the development of a highly precise and accurate analytical method for the determination of three matrix-bound pyrethroids, namely, cypermethrin, permethrin, and bifenthrin, using an isotope dilution gas chromatography/mass spectrometry technique. Identification of the analytes was confirmed under selective ion monitoring mode by the presence of two dominant ion fragments within specific time windows and matching of relative ion intensities of the ions concerned in samples and calibration standards. Quantitation was based on the measurement of concentration ratios of the natural and isotope analogues in the sample and calibration blends. Intraday and interday repeatabilities of replicate analyses of the pyethroids in an apple juice sample were below 0.5%. The expanded relative uncertainty ranged from 3 to 6%, which was significantly lower than the range obtained using internal or external calibration methods. As a labeled analogue is not available for bifenthrin, bifenthrin was determined using labeled cis-permethrin as the internal standard. The results were counterchecked by a gas chromatography-electron capture detection technique using PCB 209 as the internal standard. The method developed was applied to a recent pilot study organized by CCQM and the results were consistent with those of other participants.
Density functional theory of gas-liquid phase separation in dilute binary mixtures.
Okamoto, Ryuichi; Onuki, Akira
2016-06-22
We examine statics and dynamics of phase-separated states of dilute binary mixtures using density functional theory. In our systems, the difference of the solvation chemical potential between liquid and gas [Formula: see text] (the Gibbs energy of transfer) is considerably larger than the thermal energy [Formula: see text] for each solute particle and the attractive interaction among the solute particles is weaker than that among the solvent particles. In these conditions, the saturated vapor pressure increases by [Formula: see text], where [Formula: see text] is the solute density added in liquid. For [Formula: see text], phase separation is induced at low solute densities in liquid and the new phase remains in gaseous states, even when the liquid pressure is outside the coexistence curve of the solvent. This explains the widely observed formation of stable nanobubbles in ambient water with a dissolved gas. We calculate the density and stress profiles across planar and spherical interfaces, where the surface tension decreases with increasing interfacial solute adsorption. We realize stable solute-rich bubbles with radius about 30 nm, which minimize the free energy functional. We then study dynamics around such a bubble after a decompression of the surrounding liquid, where the bubble undergoes a damped oscillation. In addition, we present some exact and approximate expressions for the surface tension and the interfacial stress tensor.
Lattice Boltzmann accelerated direct simulation Monte Carlo for dilute gas flow simulations.
Di Staso, G; Clercx, H J H; Succi, S; Toschi, F
2016-11-13
Hybrid particle-continuum computational frameworks permit the simulation of gas flows by locally adjusting the resolution to the degree of non-equilibrium displayed by the flow in different regions of space and time. In this work, we present a new scheme that couples the direct simulation Monte Carlo (DSMC) with the lattice Boltzmann (LB) method in the limit of isothermal flows. The former handles strong non-equilibrium effects, as they typically occur in the vicinity of solid boundaries, whereas the latter is in charge of the bulk flow, where non-equilibrium can be dealt with perturbatively, i.e. according to Navier-Stokes hydrodynamics. The proposed concurrent multiscale method is applied to the dilute gas Couette flow, showing major computational gains when compared with the full DSMC scenarios. In addition, it is shown that the coupling with LB in the bulk flow can speed up the DSMC treatment of the Knudsen layer with respect to the full DSMC case. In other words, LB acts as a DSMC accelerator.This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'. © 2016 The Author(s).
Finite-momentum superfluidity and phase transitions in a p-wave resonant Bose gas
Choi, Sungsoo; Radzihovsky, Leo
2011-10-15
We study a degenerate two-species gas of bosonic atoms interacting through a p-wave Feshbach resonance as, for example, realized in a {sup 85}Rb-{sup 87}Rb mixture. We show that, in addition to a conventional atomic and a p-wave molecular spinor-1 superfluidity at large positive and negative detunings, respectively, the system generically exhibits a finite-momentum atomic-molecular superfluidity at intermediate detuning around the unitary point. We analyze the detailed nature of the corresponding phases and the associated quantum and thermal phase transitions.
Density form factors of the 1D Bose gas for finite entropy states
NASA Astrophysics Data System (ADS)
De Nardis, J.; Panfil, M.
2015-02-01
We consider the Lieb-Liniger model for a gas of bosonic δ-interacting particles. Using Algebraic Bethe Ansatz results we compute the thermodynamic limit of the form factors of the density operator between finite entropy eigenstates such as finite temperature states or generic non-equilibrium highly excited states. These form factors are crucial building blocks to obtain the thermodynamic exact dynamic correlation functions of such physically relevant states. As a proof of principle we compute an approximated dynamic structure factor by including only the simplest types of particle-hole excitations and show the agreement with known results.
Ultracold Bose gases: From the Gross-Pitaevskii to the fractional quantum Hall regime
NASA Astrophysics Data System (ADS)
Bhongale, Satyan Gopal
Ultra-cold Bose gases present an ideal environment for the study of many-body physics. These systems can be prepared under various experimental conditions with precise control. Techniques like Feshbach resonances allow us to dynamically tune the inter atomic interaction, from strongly attractive to a strongly repulsive one. In the first part of the thesis, we study the weakly interacting Bose gas in connection with the dynamics of an atom laser. Here we propose a possible optical pumping model for loading the reservoir of a continuous wave atom laser. The finite temperature effects like phase diffusion require a thorough understanding of the kinetic regime of the dilute Bose gas. In this respect, we develop a non-Markovian quantum kinetic theory and thereby show the emergence of different time scales for correlation and subsequent relaxation to an equilibrium states. Using numerical simulations, we also predict the damping rates and frequencies of collective modes. In the second part, we study the strongly correlated regime where the interaction energy is greater than any other (single particle) energy scale of the problem. Here, in the presence of a Feshbach interaction we predict the generation of novel strongly correlated paired states. Such states while similar to the one observed in a 5/2 fractional quantum hall effect, are unique in symmetry to the Bose gas system.
Localized collapse and revival of coherence in an ultracold Bose gas
McGuirk, J. M.; Zajiczek, L. F.
2011-01-15
We study the collapse and revival of coherence induced by dipolar spin waves in a trapped gas of {sup 87}Rb atoms. In particular, we observe spatially localized collapse and revival of Ramsey fringe contrast and show how the pattern of coherence depends on the strength of the spin-wave excitation. We find that the spatial character of the coherence dynamics is incompatible with a simple model based only on position-space overlap of wave functions. We show that this phenomenon requires a full phase-space description of the atomic spin using a quantum Boltzmann transport equation, which highlights spin-wave-induced coherent spin currents and the ensuing dynamics they drive.
Inelastic gas: An experimental study of vibro-fluidized dilute granular media
NASA Astrophysics Data System (ADS)
Feitosa, Klebert Bezerra
We conduct an experimental study of a two dimensional vibro-fluidized dilute granular medium. The system is composed of spherical beads confined to move in a vertical plane and excited by intense vertical vibrations. We perform full-field tracking of positions and orientations of the spheres by high speed photography. In steady-state, the motion of the grains resembles that of a molecular gas, thus the name granular gas. We study the distribution of linear velocities in the granular gas. The investigation shows that the distributions are non-gaussian, best fitted by the function P(v) ˜ exp(-beta| v|/sigma)1.5), and insensitive to number density, driving parameters and particle inelasticity. The distribution is a one parameter distribution, parameterized by the mean square velocity; which defines a granular temperature. T = ½
Influence of a magnetic field on the viscosity of a dilute gas consisting of linear molecules.
Hellmann, Robert; Vesovic, Velisa
2015-12-07
The viscomagnetic effect for two linear molecules, N2 and CO2, has been calculated in the dilute-gas limit directly from the most accurate ab initio intermolecular potential energy surfaces presently available. The calculations were performed by means of the classical trajectory method in the temperature range from 70 K to 3000 K for N2 and 100 K to 2000 K for CO2, and agreement with the available experimental data is exceptionally good. Above room temperature, where no experimental data are available, the calculations provide the first quantitative information on the magnitude and the behavior of the viscomagnetic effect for these gases. In the presence of a magnetic field, the viscosities of nitrogen and carbon dioxide decrease by at most 0.3% and 0.7%, respectively. The results demonstrate that the viscomagnetic effect is dominated by the contribution of the jj¯ polarization at all temperatures, which shows that the alignment of the rotational axes of the molecules in the presence of a magnetic field is primarily responsible for the viscomagnetic effect.
Density functional theory of gas-liquid phase separation in dilute binary mixtures
NASA Astrophysics Data System (ADS)
Okamoto, Ryuichi; Onuki, Akira
2016-06-01
We examine statics and dynamics of phase-separated states of dilute binary mixtures using density functional theory. In our systems, the difference of the solvation chemical potential between liquid and gas Δ {μ\\text{s}} (the Gibbs energy of transfer) is considerably larger than the thermal energy {{k}\\text{B}}T for each solute particle and the attractive interaction among the solute particles is weaker than that among the solvent particles. In these conditions, the saturated vapor pressure increases by {{k}\\text{B}}Tn2\\ell\\exp ≤ft(Δ {μ\\text{s}}/{{k}\\text{B}}T\\right) , where n2\\ell is the solute density added in liquid. For \\exp ≤ft(Δ {μ\\text{s}}/{{k}\\text{B}}T\\right)\\gg 1 , phase separation is induced at low solute densities in liquid and the new phase remains in gaseous states, even when the liquid pressure is outside the coexistence curve of the solvent. This explains the widely observed formation of stable nanobubbles in ambient water with a dissolved gas. We calculate the density and stress profiles across planar and spherical interfaces, where the surface tension decreases with increasing interfacial solute adsorption. We realize stable solute-rich bubbles with radius about 30 nm, which minimize the free energy functional. We then study dynamics around such a bubble after a decompression of the surrounding liquid, where the bubble undergoes a damped oscillation. In addition, we present some exact and approximate expressions for the surface tension and the interfacial stress tensor.
Glass transition of adsorbed stereoregular PPMA by inverse gas chromatography at infinite dilution
NASA Astrophysics Data System (ADS)
Hamieh, T.; Rezzaki, M.; Grohens, Y.; Schultz, J.
1998-10-01
In this paper, we used inverse gas chromatography (IGC) at infinite dilution that proved to be a powerful technique to determine glass transition and other transitions of PMMA adsorbed on α-alumina. We highlighted the glass transition temperature of the system PMMA/α-Al2O3 with defined polymer tacticity at various covered surface fractions. Thus, the Tg of the adsorbed isotactic PMMA increases strongly as compared to the bulk value. The study of the physical chemical properties of PMMA/α-alumina revealed an important difference in the acidic and basic behaviour, in Lewis terms, of aluminium oxide covered by various concentrations of PMMA. It appears that there is a stabilisation of the physical chemical properties of PMMA/α-Al2O3 for a surface coverage above 50%. This study also highlighted an important effect of the tacticity of the polymer on the acid-base character of the system PMMA/Al2O3. Dans cet article, nous montrons que la chromatographie gazeuse inverse (CGI) à dilution infinie se révèle être une technique très intéressante pour la détermination de la transition vitreuse de polymères stéréoréguliers adsorbés sur des substrats solides tels que l'alumine. Nous avons mis en évidence des transitions attribuées aux phénomènes de relaxation béta, transition vitreuse et autres transitions des systèmes PMMA/Al2O3 de tacticité définie à différents taux de recouvrement. Ainsi, la Tg du PMMA isotactique adsorbé augmente de façon significative par rapport a celle du polymère massique. L'étude des propriétés physico-chimiques du système PMMA/Al2O3, révèle une différence importante dans le comportement acido-basique, au sens de Lewis, de l'alumine pour de taux de recouvrement en PMMA variables. Il apparaît qu'il y a stabilisation des propriétés physico-chimiques de PMMA/Al2O3 pour un taux de recouvrement en PMMA supérieur à 50 %. Cette étude a montré également une influence importante de la tacticité du polymère sur le
Nada, Hiroki
2006-08-24
A molecular dynamics simulation of a three-phase system including a gas clathrate, liquid water, and a gas was carried out at 298 K and high pressure in order to investigate the growth mechanism of the clathrate from a dilute aqueous gas solution. The simulation indicated that the clathrate grew on interfaces between the clathrate and the liquid water, after transfer of the gas molecules from the gas phase to the interfaces. The results suggest a two-step process for growth: first, gas molecules are arranged at cage sites, and second, H(2)O molecules are ordered near the gas molecules. The results also suggest that only the H(2)O molecules, which are surrounded or sandwiched by the gas molecules, form the stable polygons that constitute the cages of the clathrate. In addition, the growth of the clathrate from a concentrated aqueous gas solution was also simulated, and the results suggested a growth mechanism in which many H(2)O and gas molecules correctively form the structure of the clathrate. The clathrate grown from the concentrated solution contained some empty cages, whereas the formation of empty cages was not observed during the growth from the dilute solution. The results obtained by both simulations are compared with the results of an experimental study, and the growth mechanism of the clathrate in a real system is discussed.
Kim, Mi Eon; Kim, Yong Doo; Kang, Ji Hwan; Heo, Gwi Suk; Lee, Dong Soo; Lee, Sangil
2016-04-01
Dimethyl sulphide (DMS) is an important compound in global atmospheric chemistry and climate change. Traceable international standards are essential for measuring accurately the long-term global trend in ambient DMS. However, developing accurate gas standards for sub-nanomole per mole (nmol/mol) mole fractions of DMS in a cylinder is challenging, because DMS is reactive and unstable. In this study, a dynamic dilution method that is traceable and precise was developed to generate sub-nmol/mol DMS gas mixtures with a dynamic dilution system based on sonic nozzles and a long-term (>5 years) stable 10 μmol/mol parent DMS primary standard gas mixtures (PSMs). The dynamic dilution system was calibrated with traceable methane PSMs, and its estimated dilution factors were used to calculate the mole fractions of the dynamically generated DMS gas mixtures. A dynamically generated DMS gas mixture and a 6 nmol/mol DMS PSM were analysed against each other by gas chromatography with flame-ionisation detection (GC/FID) to evaluate the dilution system. The mole fractions of the dynamically generated DMS gas mixture determined against a DMS PSM and calculated with the dilution factor agreed within 1% at 6 nmol/mol. In addition, the dynamically generated DMS gas mixtures at various mole fractions between 0.4 and 11.7 nmol/mol were analysed by GC/FID and evaluated for their linearity. The analytically determined mole fractions showed good linearity with the mole fractions calculated with the dilution factors. Results showed that the dynamic dilution method generates DMS gas mixtures ranging between 0.4 nmol/mol and 12 nmol/mol with relative expanded uncertainties of less than 2%. Therefore, the newly developed dynamic dilution method is a promising reference method for generating sub-nmol/mol DMS gas standards for accurate ambient measurements.
2016-06-01
ER D C/ EL T R- 16 -1 0 SERDP/ESTCP, USEPA, & FUDS-ITA Laboratory -Scale Demonstration Using Dilute Ammonia Gas-Induced Alkaline...library at http://acwc.sdp.sirsi.net/client/default. SERDP/ESTCP, USEPA, FUDS-ITA ERDC/EL TR-16-10 June 2016 Laboratory -Scale Demonstration...and Chris Griggs Environmental Laboratory U.S. Army Engineer Research and Development Center 3909 Halls Ferry Road Vicksburg, MS 39180-6199
Weiguo Pan; Zuohe Chi; Yongjing Liao
1997-07-01
This article reported pressure drop characteristics and methods for calculating friction factors {lambda} 0 and {lambda}{sub {mu}} for gas and gas-solids flows, respectively, in straight horizontal pipes are summarized advantages seed. The and disadvantages of calculating friction factor {lambda}{sub {mu}} through dimensional analysis in comparison with model simulation are analyzed. It is pointed out that model simulation is more suitable to engineering use than dimensional analysis. According to experimental results of dilute gas-coal powder flow in straight horizontal pipes of the coal pulverization system in a power plant; an empirical formula and a theoretical formula for calculating friction factor {lambda}{sub {mu}} in straight horizontal pipes transporting dilute coal powder are obtained.
Partial discharge and breakdown mechanisms in ultra-dilute SF6 and PFC gases mixed with N2 gas
NASA Astrophysics Data System (ADS)
Okubo, H.; Yamada, T.; Hatta, K.; Hayakawa, N.; Yuasa, S.; Okabe, S.
2002-11-01
Because of the high global warming potential of SF6 gas, research on alternative gases for electrical insulation with a lower environmental impact is essential. Gas mixtures composed of electronegative gases and N2 gas have the advantage of the reduction of the amount of SF6 gas and of utilizing the synergistic effect in electrical insulation performance. We investigated the partial discharge (PD) and breakdown (BD) characteristics of SF6/N2 and PFC (C3F8/N2 and C2F6/N2) gas mixtures under non-uniform electric field conditions, by changing the dilute content of electronegative gases. As a result, the synergistic effect in SF6/N2 gas mixtures was verified to be higher than that in PFC/N2 gas mixtures. The physical mechanism from PD inception to BD was discussed with consideration of the difference in electronegativity of SF6 and PFC gases. Furthermore, we found that PD inception and PD-to-BD mechanisms changed at a content of 10 ppm for SF6 due to the electron attachment activity of SF6 gas. The change in the PD and BD mechanisms in C3F8/N2 and C2F6/N2 gas mixtures appeared at 0.1% content for C3F8 and at 1% content for C2F6.
Disorder, three body interaction and Bose glass phase in a spinor atomic gas in an optical lattice
NASA Astrophysics Data System (ADS)
Nabi, Sk Noor; Basu, Saurabh
2016-10-01
We study the effects of disorder on the spin dependent interaction term of a spinor Bose Hubbard model with a three body interaction potential. The signature of the Bose glass (BG) phase is observed by computing the fraction of the lattice sites having finite superfluid (SF) order parameter and non integer occupation densities. We obtain the phase diagram both for the antiferromagnetic (AF) and ferromagnetic (F) cases via a percolation analysis. In the AF case, the BG phase intervenes between the odd-even Mott insulating (MI) lobes (for example, the lobes corresponding to occupation densities, n=1 and (n=2) but not between the even-odd MI lobes. In the ferromagnetic case, the presence of the BG phase is observed between all the MI lobes irrespective of them being even or odd. The BG phase almost destroys the first MI lobe while the MI phase looks more stable than the SF phase both in the AF and F cases due to the presence of the three body interactions.
Beyond mean-field properties of binary dipolar Bose mixtures at low temperatures
NASA Astrophysics Data System (ADS)
Pastukhov, Volodymyr
2017-02-01
We rigorously analyze the low-temperature properties of homogeneous three-dimensional two-component Bose mixture with dipole-dipole interaction. For such a system the effective hydrodynamic action that governs the behavior of low-energy excitations is derived. The infrared structure of the exact single-particle Green's functions is obtained in terms of macroscopic parameters, namely the inverse compressibility and the superfluid density matrices. Within the one-loop approximation we calculate some of the most relevant observable quantities and give the beyond mean-field stability condition for the binary dipolar Bose gas in the dilute limit. A brief variational derivation of the coupled equations that describe macroscopic hydrodynamics of the system in the external nonuniform potential at zero temperature is presented.
Limits to the analog Hawking temperature in a Bose-Einstein condensate
Wuester, S.; Savage, C. M.
2007-07-15
Quasi-one-dimensional outflow from a dilute gas Bose-Einstein condensate reservoir is a promising system for the creation of analog Hawking radiation. We use numerical modeling to show that stable sonic horizons exist in such a system under realistic conditions, taking into account the transverse dimensions and three-body loss. We find that loss limits the analog Hawking temperatures achievable in the hydrodynamic regime, with sodium condensates allowing the highest temperatures. A condensate of 30 000 atoms, with transverse confinement frequency {omega}{sub perpendicular}=6800x2{pi} Hz, yields horizon temperatures of about 20 nK over a period of 50 ms. This is at least four times higher than for other atoms commonly used for Bose-Einstein condensates.
NASA Astrophysics Data System (ADS)
Gardiner, S. A.; Morgan, S. A.
2007-04-01
We describe a number-conserving approach to the dynamics of Bose-Einstein condensed dilute atomic gases. This builds upon the works of Gardiner [Phys. Rev. A 56, 1414 (1997)] and Castin and Dum [Phys. Rev. A 57, 3008 (1998)]. We consider what is effectively an expansion in powers of the ratio of noncondensate to condensate particle numbers, rather than inverse powers of the total number of particles. This requires the number of condensate particles to be a majority, but not necessarily almost equal to the total number of particles in the system. We argue that a second-order treatment of the relevant dynamical equations of motion is the minimum order necessary to provide consistent coupled condensate and noncondensate number dynamics for a finite total number of particles, and show that such a second-order treatment is provided by a suitably generalized Gross-Pitaevskii equation, coupled to the Castin-Dum number-conserving formulation of the Bogoliubov-de Gennes equations. The necessary equations of motion can be generated from an approximate third-order Hamiltonian, which effectively reduces to second order in the steady state. Such a treatment as described here is suitable for dynamics occurring at finite temperature, where there is a significant noncondensate fraction from the outset, or dynamics leading to dynamical instabilities, where depletion of the condensate can also lead to a significant noncondensate fraction, even if the noncondensate fraction is initially negligible.
Iraqi, Rafika; Vermeulen, Catherine; Benzekri, Amale; Bouseta, Amina; Collin, Sonia
2005-02-23
"Spanish style" Moroccan green table olives were screened for potent odorants by gas chromatography-olfactometry/aroma extraction dilution analysis of a representative Likens-Nickerson extract. (Z)-3-Hexenal [flavor dilution factor (FD) = 256], (E,E)-2,4-decadienal (FD = 128), and (E,Z)-2,4-decadienal (FD = 64) were revealed to confer green and coriander/paraffin oil odors to both fruit and oil extracts, whereas guaiacol (FD = 128) imparted a bad olive, phenolic note. Methional (3-methylthiopropionaldehyde, FD = 128) and several terpenes (FD
Mutelet, Fabrice; Jaubert, Jean-Noël; Rogalski, Marek; Harmand, Julie; Sindt, Michèle; Mieloszynski, Jean-Luc
2008-03-27
Activity coefficients at infinite dilution, gammainfinity, of organic compounds in two new room-temperature ionic liquids (n-methacryloyloxyhexyl-N-methylimidazolium bromide (C10H17O2MIM)(Br) at 313.15 and 323.15 K and n-acryloyloxypropyl-N-methylimidazolium bromide(C6H11O2MIM)(Br)) were determined using inverse gas chromatography. Phase loading studies of the net retention volume per gram of packing as a function of the percent phase loading were used to estimate the influence of concurrent retention mechanisms on the accuracy of activity coefficients at infinite dilution of solutes in both ionic liquids. It was found that most of the solutes were retained largely by partition with a small contribution from adsorption and that n-alkanes were retained predominantly by interfacial adsorption on ionic liquids studied in this work. The solvation characteristics of the two ionic liquids were evaluated using the Abraham solvation parameter model.
Tsachaki, Maroussa; Gady, Anne-Laure; Kalopesas, Michalis; Linforth, Robert S T; Athès, Violaine; Marin, Michele; Taylor, Andrew J
2008-07-09
On the basis of a mechanistic model, the overall and liquid mass transfer coefficients of aroma compounds were estimated during aroma release when an inert gas diluted the static headspace over simple ethanol/water solutions (ethanol concentration = 120 mL x L(-1)). Studied for a range of 17 compounds, they were both increased in the ethanol/water solution compared to the water solution, showing a better mass transfer due to the presence of ethanol, additively to partition coefficient variation. Thermal imaging results showed differences in convection of the two systems (water and ethanol/water) arguing for ethanol convection enhancement inside the liquid. The effect of ethanol in the solution on mass transfer coefficients at different temperatures was minor. On the contrary, at different headspace dilution rates, the effect of ethanol in the solution helped to maintain the volatile headspace concentration close to equilibrium concentration, when the headspace was replenished 1-3 times per minute.
Wang, Yuanyuan; Finn, Chad; Qian, Michael C
2005-05-04
The aroma extract of Chickasaw blackberry (Rubus L.) was separated with silica gel normal phase chromatography into six fractions. Gas chromatography-olfactometry (GCO) was performed on each fraction to identify aroma active compounds. Aroma extraction dilution analysis (AEDA) was employed to characterize the aroma profile of Chickasaw blackberries from two growing regions of the United States: Oregon and Arkansas. Comparative AEDA analysis showed that the berries grown in the two regions had similar aroma compositions; however, those odorants had various aroma impacts in each region. The compounds with high flavor dilution factors in Oregon's Chickasaw were ethyl butanoate, linalool, methional, trans,cis-2,6-nonadienal, cis-1,5-octadien-3-one, and 2,5-dimethyl-4-hydroxy-3(2H)-furanone, whereas in the Chickasaw grown in Arkansas, they were ethyl butanoate, linalool, methional, ethyl 2-methylbutanoate, beta-damascenone, and geraniol.
10 cm x 10 cm Single Gas Electron Multiplier (GEM) X-ray Fluorescence Detector for Dilute Elements
NASA Astrophysics Data System (ADS)
Shaban, E. H.; Siddons, D. P.; Seifu, D.
2014-03-01
We have built and tested a 10 cm × 10 cm single Gas Electron Multiplier (GEM) X-ray detector to probe dilute amounts of Fe in a prepared sample. The detector uses Argon/Carbon Dioxide (75/25) gas mixture flowing at a slow rate through a leak proof Plexi-glass enclosure held together by O-rings and screws. The Fluorescence X-ray emitted by the element under test is directed through a Mylar window into the drift region of the detector where abundant gas is flowing. The ionized electrons are separated, drifted into the high electric field of the GEM, and multiplied by impact ionization. The amplified negatively charged electrons are collected and further amplified by a Keithley amplifier to probe the absorption edge of the element under test using X-ray absorption spectroscopy technique. The results show that the GEM detector provided good results with less noise as compared with a Silicon drift detector (SDD).
NASA Astrophysics Data System (ADS)
Jain, P.; Bradley, A. S.; Gardiner, C. W.
2007-08-01
We study an experimentally realizable system containing stable black hole white hole acoustic horizons in toroidally trapped Bose-Einstein condensates—the quantum de Laval nozzle. We numerically obtain stationary flow configurations and assess their stability using Bogoliubov theory, finding both in hydrodynamic and nonhydrodynamic regimes there exist dynamically unstable regions associated with the creation of positive and negative energy quasiparticle pairs in analogy with the gravitational Hawking effect. The dynamical instability takes the form of a two mode squeezing interaction between resonant pairs of Bogoliubov modes. We study the evolution of dynamically unstable flows using the truncated Wigner method, which confirms the two mode squeezed state picture of the analogue Hawking effect for low winding number.
NASA Astrophysics Data System (ADS)
Arahata, Emiko; Nikuni, Tetsuro
2013-03-01
We study sound propagation in Bose-condensed gases in a highly elongated harmonic trap at finite temperatures. This problem is studied within the framework of the Zaremba-Nikuni-Griffin (ZNG) formalism, which consists of a generalized Gross-Pitaevskii equation for the condensate and a kinetic equation for the thermal cloud. We extend the ZNG formalism to deal with a highly anisotropic trap potential and use it to simulate sound propagation using the trap parameters corresponding to an experiment on sound pulse propagation at finite temperature. We focus on the high-density two-fluid hydrodynamic regime, and explore the possibility of observing first- and second-sound pulse propagation. The results of numerical simulation are compared with analytical results derived from linearized ZNG hydrodynamic equations. We show that the second-sound mode makes the dominant contribution to condensate motion at relatively high temperature, while the first-sound mode makes an appreciable contribution.
Collective modes of a one-dimensional trapped Bose gas in the presence of the anomalous density
NASA Astrophysics Data System (ADS)
Boudjemâa, Abdelâali
2016-11-01
We study the collective modes of a one-dimensional harmonically trapped Bose-Einstein condensate in the presence of the anomalous density using the time-dependent Hartree-Fock-Bogoliubov theory. Within the hydrodynamic equations, we derive analytical expressions for the mode frequencies and the density fluctuations of the anomalous density which constitutes the minority component at very low temperature and feels an effective external potential exerted by the majority component, i.e., the condensate. On the other hand, we numerically examine the temperature dependence of the breathing mode oscillations of the condensate at finite temperature in the weak-coupling regime. At zero temperature, we compare our predictions with available experimental data, theoretical treatments, and Monte carlo simulations in all interaction regimes and the remaining hindrances are emphasized. We show that the anomalous correlations have a non-negligible role on the collective modes at both zero and finite temperatures.
Guiding-center dynamics of vortex dipoles in Bose-Einstein condensates
Middelkamp, S.; Schmelcher, P.; Torres, P. J.; Kevrekidis, P. G.; Frantzeskakis, D. J.; Carretero-Gonzalez, R.; Freilich, D. V.; Hall, D. S.
2011-07-15
A quantized vortex dipole is the simplest vortex molecule, comprising two countercirculating vortex lines in a superfluid. Although vortex dipoles are endemic in two-dimensional superfluids, the precise details of their dynamics have remained largely unexplored. We present here several striking observations of vortex dipoles in dilute-gas Bose-Einstein condensates, and develop a vortex-particle model that generates vortex line trajectories that are in good agreement with the experimental data. Interestingly, these diverse trajectories exhibit essentially identical quasiperiodic behavior, in which the vortex lines undergo stable epicyclic orbits.
NASA Astrophysics Data System (ADS)
Hellmann, Robert
2014-10-01
A four-dimensional intermolecular potential energy surface (PES) for two rigid carbon dioxide molecules was determined from quantum-chemical ab initio calculations. Interaction energies for 1229 CO2-CO2 configurations were computed at the CCSD(T) level of theory using basis sets up to aug-cc-pVQZ supplemented with bond functions. An analytical site-site potential function with seven sites per CO2 molecule was fitted to the interaction energies. The PES was validated by calculating the second virial coefficient as well as viscosity and thermal conductivity in the dilute-gas limit.
Driskell, W Jack; Shih, Ming; Needham, Larry L; Barr, Dana B
2002-01-01
An isotope dilution gas chromatography-tandem mass spectrometric (GC-MS-MS) method was developed for quantitating the urinary metabolites of the organophosphorus nerve agents sarin, soman, tabun (GA), VX, and GF. Urine samples were concentrated by codistillation with acetonitrile, derivatized by methylation with diazomethane, and analyzed by GC-MS-MS. The limits of detection were less than 4 microg/L for all the analytes except for the GA metabolite, which had a limit of detection of less than 20 microg/L.
Stryjek, R.; Bobbo, S.; Camporese, R.; Zilio, C.
1999-05-01
Activity coefficients at infinite dilution have been measured by gas chromatography for 14 refrigerants (R12, R22, R32, R124, R125, R134a, R142b, R143a, RE170, R236ea, R290, R600, R600a, and R236fa) as solutes, using a polyol ester oil (POE), EMKARATE by ICI, as a stationary phase (solvent). Instrumental analysis (NMR, IR) showed that the main components of the oil are pentaerithritol esters of carboxylic acids, and electrospray ionization spectrometry revealed an average molecular mass of the POE of 618 g/mol. The measurements were performed within a temperature range of 244 K to 313 K, but a specific temperature range for each refrigerant was adopted depending on its retention data. The experimental findings are well-represented by the equation: ln {gamma}{sub i}{sup {infinity}} = a{sub i} {minus} b{sub i}/T. Some refrigerants, i.e., R22, R124, R125, R236ea, and R236fa, show quite a considerable positive temperature dependence of their activity coefficients at infinite dilution, which can be attributed to hydrogen bonding with the POE, unlike other refrigerants that show a small, either positive or negative temperature dependence. To the authors` knowledge, there are no data in the literature on activity coefficients at infinite dilution for refrigerant and oil (lubricant) systems, and details on the solubility of refrigerants in oils are also extremely scarce.
Pérez, José J.; Williams, Megan K.; Weerasekera, Gayanga; Smith, Kimberly; Whyatt, Robin M.; Needham, Larry L.; Barr, Dana Boyd
2010-01-01
We have developed a gas chromatography-high resolution mass spectrometry method for measuring pyrethroid, organophosphorus, carbamate and fipronil pesticides and the synergist piperonyl butoxide in human plasma. Plasma samples were extracted using solid phase extraction and were then concentrated for injection and analysis using isotope dilution gas chromatography-high resolution mass spectrometry. The limits of detection ranged from 10 to 158 pg/mL with relative recoveries at concentrations near the LODs (e.g., 25 or 250 pg/mL) ranging from 87% to 156% (9 of the 16 compounds were withing ± 15% of 100%). The extraction recoveries ranged from 20% to 98% and the overall method relative standard deviations were typically less than 20% with some exceptions. Analytical characteristics were determined at 25, 250, and 1000 pg/mL. PMID:20434413
Thermophoretic force on micro- and nanoparticles in dilute binary gas mixtures.
Wang, Jun; Li, Zhigang
2011-08-01
We theoretically investigate the thermophoretic force on spherical particles in binary monatomic gas mixtures in the free molecular regime. Based on gas kinetic theory and by considering the gas-particle interactions, we derive the analytical formulas of the thermophoretic force for two limiting gas-particle collision models; namely, specular and diffuse scattering scenarios. The formulas are consistent with those in simple gases and apply to both micro- and nanoparticles; for the latter the intermolecular interactions are important. As an example, the thermophoretic force on Ag nanoparticles in He-Ar mixtures is illustrated.
Competition between Bose-Einstein Condensation and Spin Dynamics.
Naylor, B; Brewczyk, M; Gajda, M; Gorceix, O; Maréchal, E; Vernac, L; Laburthe-Tolra, B
2016-10-28
We study the impact of spin-exchange collisions on the dynamics of Bose-Einstein condensation by rapidly cooling a chromium multicomponent Bose gas. Despite relatively strong spin-dependent interactions, the critical temperature for Bose-Einstein condensation is reached before the spin degrees of freedom fully thermalize. The increase in density due to Bose-Einstein condensation then triggers spin dynamics, hampering the formation of condensates in spin-excited states. Small metastable spinor condensates are, nevertheless, produced, and they manifest in strong spin fluctuations.
Ground-state phases of the spin-orbit-coupled spin-1 Bose gas in a toroidal trap
NASA Astrophysics Data System (ADS)
Wang, Ji-Guo; Xu, Liang-Liang; Yang, Shi-Jie
2017-09-01
We consider the spin-1 Bose-Einstein condensates with the isotropic Rashba spin-orbit coupling in a two-dimensional toroidal trap. Three types of striped phases are found in a nonrotational system, i.e., the stripe phase with the periodic density modulation along the azimuthal direction, the stripe phase with the periodic density modulation along both the azimuthal and the radial directions, and the stripe phase with the periodic density modulation along the radial direction. By adding the rotation, the condensates occupy the mF=0 component for small rotational frequency, while they occupy both the mF=1 and mF=-1 components for large rotational frequency when both the relative interaction and the spin-orbit coupling are weak. For the stronger relative interaction and spin-orbit coupling, the vortices of the system are elongated along the radial direction and linked one after another. As the rotational frequency further increases, the density evolves from the elongated effect of the vortices into a laminar vortex ring.
Efficient gas-separation process to upgrade dilute methane stream for use as fuel
Wijmans, Johannes G [Menlo Park, CA; Merkel, Timothy C [Menlo Park, CA; Lin, Haiqing [Mountain View, CA; Thompson, Scott [Brecksville, OH; Daniels, Ramin [San Jose, CA
2012-03-06
A membrane-based gas separation process for treating gas streams that contain methane in low concentrations. The invention involves flowing the stream to be treated across the feed side of a membrane and flowing a sweep gas stream, usually air, across the permeate side. Carbon dioxide permeates the membrane preferentially and is picked up in the sweep air stream on the permeate side; oxygen permeates in the other direction and is picked up in the methane-containing stream. The resulting residue stream is enriched in methane as well as oxygen and has an EMC value enabling it to be either flared or combusted by mixing with ordinary air.
In Vivo Measurements Of Coronary Blood Volumi By Dye And Inert Gas Dilution Technic
NASA Astrophysics Data System (ADS)
Hoeft, A.; Korb, H.; Wolpers, H. G.
1984-10-01
The application of a double fiberoptic device for measurements of arterial and coronary venous dye dilution curves facilitates the determination of coronary mean transit times even under clinical conditions. Since the dye, indocyanine green, is an intravascular tracer, the calculation of tissue blood flow would be possible if the intracoronary blood volume per unit of muscular weight is known. This study was therefore designed to investigate the physiologic range and the influence of coronary vasodilation and different hemodynamic conditions on the amount of myocardial blood volume. All experiments were carried out on anaesthetized close chest mongrel dogs in heart catheterization technic. Myocardial preload, afterload and inotropism and coronary vascular tone were varied by induction of hypo-, normo- and hypervolemia as well as by intravenous application of catecholamines, 13-blocking agents and vasodilating drugs. The determination of coronary blood volume was based on arterial and coronary venous kinetics of the intravascular tracer indocyanine green and the freely diffusible tracers helium and argon. Simultaneous measurements of the dye and the inert gases were obtained by a double fiberoptic system and a twin mass spectrometer, respectively. The intravascular and the tissue mean transit times as well as the coronary blood volume per unit of tissue weight were computed from the impulse response functions obtained by numerical deconvolution of the arterial and coronary venous indicator dilution curves. In contrast to reports of other authors coronary blood volume did not increase to a major extend during coronary vasodilation or elevated afterload. These new results suggest that the variation of coronary blood volume described in the literature is mainly due to methodological errors resulting from monoexponential extrapolation and distortion of the dye signal by the sampling catheter. These systematic errors, which, in particular, lead to an overestimation of
Abdullaev, F.Kh.; Garnier, J.
2004-11-01
The collective oscillations of one-dimensional (1D) repulsive Bose gas with external harmonic confinement in two different regimes are studied. The first regime is the mean-field regime when the density is high. The second regime is the Tonks-Girardeau regime when the density is low. We investigate the resonances under periodic modulations of the trap potential and the effective nonlinearity. Modulations of the effective nonlinear coefficient result from modulations of the atomic scattering length by the Feshbach resonance method or variations of the transverse trap frequency. In the mean-field regime we predict bistability in the nonlinear oscillations of the condensate. In the Tonks-Girardeau regime the resonance has the character of a linear parametric resonance. In the case of rapid strong modulations of the nonlinear coefficient we find analytical expressions for the nonlinearity managed soliton width and the frequency of the slow secondary oscillations near the fixed point. We confirm the analytical predictions by direct numerical simulations of the 1D Gross-Pitaevskii equation and the effective nonlinear Schroedinger equation with quintic nonlinearity and trap potential.
Sakhel, Asaad R.; Qashou, Saleem I.; Sakhel, Roger R.; Ghassib, Humam B.
2010-12-15
The static fluctuation approximation (SFA) is applied to compute the thermodynamic properties of a trapped two-dimensional (2D) interacting hard-sphere (HS) Bose gas in the weakly and strongly interacting regime. A mean-field approach involving a variational wave function is used to compute the mean-field energy as a function of temperature for each harmonic oscillator (HO) state plugged into the SFA technique. In the variational approach, a parameter {alpha} is introduced into the harmonic oscillator wave function in order to take into account the changes in the width when the repulsive interactions between the bosons are increased. In the weakly interacting regime, below the critical temperature, the total energy of all HO states (evaluated by our model) matches the noninteracting result very well. However, beyond the critical temperature, we 'fit' our energies to the classical limit for 2D bosons in a trap by using a suitably proposed weighting function. We compare our results to earlier results of mean-field theory. Further, we evaluate the density matrix arising from correlations between the HO orbitals.
Johnson-Ajinwo, Okiemute Rosa; Li, Wen-Wu
2014-06-18
Black cumin seed (Nigella sativa L.) is a widely used spice and herb, where thymoquinone (2-isopropyl-5-methyl-1,4-benzoquinone) is the major bioactive compound. Here, a stable isotope dilution (SID) gas chromatography-mass spectrometry (GC-MS) technique was developed for the quantification of thymoquinone. A doubly deuterated thymoquinone ([(2)H2]-thymoquinone) was synthesized for the first time with more than 93% deuteration degree shown by mass spectrometry and proton nuclear magnetic resonance ((1)H NMR). This compound was used as an internal standard for the quantification of thymoquinone using a SID GC-MS method. The validation experiment showed a recovery rate of 99.1 ± 1.1% relative standard deviation (RSD). Standard addition and external calibration methods have also been used to quantify thymoquinone, which cross-validated the developed stable isotope dilution assay (SIDA). In comparison to external calibration and standard addition methods, the SIDA method is robust and accurate. The concentration of thymoquinone in five marketed black cumin seed oils ranged between 3.34 and 10.8 mg/mL by use of SID GC-MS.
Feng, Yunzi; Cai, Yu; Sun-Waterhouse, Dongxiao; Cui, Chun; Su, Guowan; Lin, Lianzhu; Zhao, Mouming
2015-11-15
Aroma extract dilution analysis (AEDA) is widely used for the screening of aroma-active compounds in gas chromatography-olfactometry (GC-O). In this study, three aroma dilution methods, (I) using different test sample volumes, (II) diluting samples, and (III) adjusting the GC injector split ratio, were compared for the analysis of volatiles by using HS-SPME-AEDA. Results showed that adjusting the GC injector split ratio (III) was the most desirable approach, based on the linearity relationships between Ln (normalised peak area) and Ln (normalised flavour dilution factors). Thereafter this dilution method was applied in the analysis of aroma-active compounds in Japanese soy sauce and 36 key odorants were found in this study. The most intense aroma-active components in Japanese soy sauce were: ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl 4-methylpentanoate, 3-(methylthio)propanal, 1-octen-3-ol, 2-methoxyphenol, 4-ethyl-2-methoxyphenol, 2-methoxy-4-vinylphenol, 2-phenylethanol, and 4-hydroxy-5-ethyl-2-methyl-3(2H)-furanone. Copyright © 2015. Published by Elsevier Ltd.
Bose Polarons in the Strongly Interacting Regime
NASA Astrophysics Data System (ADS)
Hu, Ming-Guang; Van de Graaff, Michael J.; Kedar, Dhruv; Corson, John P.; Cornell, Eric A.; Jin, Deborah S.
2016-07-01
When an impurity is immersed in a Bose-Einstein condensate, impurity-boson interactions are expected to dress the impurity into a quasiparticle, the Bose polaron. We superimpose an ultracold atomic gas of 87Rb with a much lower density gas of fermionic 40 impurities. Through the use of a Feshbach resonance and radio-frequency spectroscopy, we characterize the energy, spectral width, and lifetime of the resultant polaron on both the attractive and the repulsive branches in the strongly interacting regime. The width of the polaron in the attractive branch is narrow compared to its binding energy, even as the two-body scattering length diverges.
Satyendra Nath Bose and nanophotonics
NASA Astrophysics Data System (ADS)
Gaponenko, Sergey V.
2014-01-01
This paper is devoted to the 90th anniversary of the 1924 publication of the seminal paper by Bose titled "Planck's law and the hypothesis on light quanta" (Zeitschrift für Physik 26, 178-181). The paper has been the cornerstone quantum statistical physics. Remarkably, the very starting idea is the discreteness of phase space expressed in the form of the density of states. Bose considered equilibrium electromagnetic radiation as gas of photons and, therefore, introduced the photon density of states notion into the physics though without using directly the term "density of states." Today, engineering photon density of states to modify light-matter interaction in nanostructures including both spontaneous emission and spontaneous scattering of photons constitutes the solid part of nanophotonics.
Huang, L.Q.
1989-03-01
A multiresidue method was developed for the simultaneous determination of low parts per billion (ppb) concentrations of the herbicides alachlor, metolachlor, atrazine, and simazine in water and soil using isotope dilution gas chromatography/mass spectrometry (GC/MS). Known amounts of /sup 15/N,/sup 13/C-alachlor and /sup 2/H/sub 5/-atrazine were added to each sample as internal standards. The samples were then prepared by a solid phase extraction with no further cleanup. A high resolution GC/low resolution MS system with data acquisition in selected ion monitoring mode was used to quantitate herbicides in the extract. The limit of detection was 0.05 ppb for water and 0.5 ppb for soil. Accuracy greater than 80% and precision better than 4% was demonstrated with spiked samples.
Müller, Karsten; Seubert, Andreas
2014-06-01
The accurate ultra-trace analysis of six fluorobenzoic acids (FBAs) via isotope dilution gas chromatography mass spectrometry through their deuterated analogues is described. North Sea reservoir and ground water samples were spiked with six deuterated FBAs (dFBAs), enriched using solid-phase extraction (SPE) and analysed using GC/MS after derivatisation with BF 3· MeOH. All FBAs were enriched and determined simultaneously. SPE allowed a 250-fold enrichment of the acids if 100 mL of sample volume was used. The method enables the determination of FBAs down to the range of 8-37 ng L (-1) with recoveries between 66 % and 85 %. It uses low amounts of chemicals and is adaptable to larger and smaller sample volumes.
Cao, Xu-Liang; Casey, Valerie; Seaman, Steve; Tague, Brett; Becalski, Adam
2007-01-01
An automated, simple, and reproducible method was developed for the determination of benzene in soft drinks, based on isotope dilution headspace gas chromatography/mass spectrometry in the selected-ion monitoring mode. The method was used to assess benzene levels in samples of 124 soft drinks and beverages. Benzene was not detected in 60% of the 124 products. The average benzene levels in 6 products exceeded the Canadian maximum acceptable concentration of 5 microg/L for benzene in drinking water, and 2 of the 6 products had benzene levels above the World Health Organization guideline of 10 microg/L. The highest level of benzene, 23 microg/L, was found in a soft drink product specifically marketed to children.
Emergence of an excitonic collective mode in the dilute electron gas
NASA Astrophysics Data System (ADS)
Takada, Yasutami
2016-12-01
By comparing two expressions for the polarization function Π (q ,i ω ) given in terms of two different local-field factors, G+(q ,i ω ) and Gs(q ,i ω ) , we have derived the kinetic-energy-fluctuation (or sixth-power) sum rule for the momentum distribution function n (p ) in the three-dimensional electron gas. With use of this sum rule, together with the total-number (or second-power) and the kinetic-energy (or fourth-power) sum rules, we have obtained n (p ) in the low-density electron gas at negative compressibility (namely, rs>5.25 with rs being the conventional density parameter) up to rs≈22 by improving on the interpolation scheme due to Gori-Giorge and Ziesche proposed in 2002. The obtained results for n (p ) combined with the improved form for Gs(q ,ω +i 0+) are employed to calculate the dynamical structure factor S (q ,ω ) to reveal that a giant peak, even bigger than the plasmon peak, originating from an excitonic collective mode made of electron-hole pair excitations, emerges in the low-ω region at |q | near 2 pF (pF: the Fermi wave number). Connected with this mode, we have discovered a singular point in the retarded dielectric function at ω =0 and |q | ≈2 pF .
Yeo, Hyeongu; An, Junyeong; Reid, Robertson; Rittmann, Bruce E; Lee, Hyung-Sool
2015-09-01
The mechanisms controlling the accumulation of dissolved methane in anaerobic membrane bioreactors (AnMBRs) treating a synthetic dilute wastewater (a glucose medium) were assessed experimentally and theoretically. The AnMBR was maintained at a temperature of 24-26 °C as the organic loading rate increased from 0.39 to 1.1 kg COD/m(3)-d. The measured concentration of dissolved methane was consistently 2.2- to 2.5-fold larger than the concentration of dissolved methane at thermodynamic equilibrium with the measured CH4 partial pressure, and the fraction of dissolved methane was as high as 76% of the total methane produced. The low gas production rate in the AnMBR significantly slowed the mass transport of dissolved methane to the gas phase. Although the production rate of total methane increased linearly with the COD loading rate, the concentration of dissolved methane only slightly increased with an increasing organic loading rate, because the mass-transfer rate increased by almost 5-fold as the COD loading increased from 0.39 to 1.1 kg COD/m(3)-d. Thus, slow mass transport kinetics exacerbated the situation in which dissolved methane accounted for a substantial fraction of the total methane generated from the AnMBR.
Neil J. Robinson; Caux, Jean -Sebastien; Konik, Robert M.
2016-04-07
We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. In conclusion, when the impurity is injected with a finite center-of-mass momentum,more » the impurity moves through the background gas in a snaking manner, arising from a quantum Newton’s cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.« less
Neil J. Robinson; Caux, Jean -Sebastien; Konik, Robert M.
2016-04-07
We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. In conclusion, when the impurity is injected with a finite center-of-mass momentum, the impurity moves through the background gas in a snaking manner, arising from a quantum Newton’s cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.
NASA Astrophysics Data System (ADS)
Robinson, Neil J.; Caux, Jean-Sébastien; Konik, Robert M.
2016-04-01
We consider the real-time dynamics of an initially localized distinguishable impurity injected into the ground state of the Lieb-Liniger model. Focusing on the case where integrability is preserved, we numerically compute the time evolution of the impurity density operator in regimes far from analytically tractable limits. We find that the injected impurity undergoes a stuttering motion as it moves and expands. For an initially stationary impurity, the interaction-driven formation of a quasibound state with a hole in the background gas leads to arrested expansion—a period of quasistationary behavior. When the impurity is injected with a finite center-of-mass momentum, the impurity moves through the background gas in a snaking manner, arising from a quantum Newton's cradlelike scenario where momentum is exchanged back and forth between the impurity and the background gas.
Density fluctuation dynamics in a dissipative self-gravitating dilute gas revisited
NASA Astrophysics Data System (ADS)
Méndez, A. R.; García-Perciante, A. L.
2016-11-01
The analysis of the behavior of density fluctuations in a dissipative self gravitating gas in the linear regime is revisited. A factorization for the dispersion relation given by approximate roots is proposed, which is analogous to the one introduced in the case without gravitational field. The threshold for the onset of a gravitational instability, namely Jeans wavenumber, is found to be unaltered by the presence of thermal and viscous dissipation. However, the behavior of damped modes does not correspond to the usual Rayleigh-Brillouin spectrum when the gravitational field is taken into account. Additional to the usual central Rayleigh peak and Brillouin doublet, both corrected due to the presence of the field, non-Lorentizan terms are included in the structure factor. These terms are larger in the presence of the gravitational field and may lead in principle to relevant differences in the general properties of the spectrum. The possible mathematical origin of these modifications is briefly discussed.
Accretion of pristine gas and dilution during the formation of multiple-population globular clusters
NASA Astrophysics Data System (ADS)
D'Ercole, A.; D'Antona, F.; Vesperini, E.
2016-10-01
We study the interaction of the early spherical GC wind powered by Type II supernovae (SNe II) with the surrounding ambient medium consisting of the gaseous disc of a star-forming galaxy at redshift z ≳ 2. The bubble formed by the wind eventually breaks out of the disc, and most of the wind moves directly out of the galaxy and is definitively lost. The fraction of the wind moving nearly parallel to the galactic plane carves a hole in the disc which will contract after the end of the SN activity. During the interval of time between the end of the SN explosions and the `closure' of the hole, very O-poor stars (the Extreme population) can form out of the super-AGB (asymptotic giant branch) ejecta collected in the GC centre. Once the hole contracts, the AGB ejecta mix with the pristine gas, allowing the formation of stars with an oxygen abundance intermediate between that of the very O-poor stars and that of the pristine gas. We show that this mechanism may explain why Extreme populations are present only in massive clusters, and can also produce a correlation between the spread in helium and the cluster mass. Finally, we also explore the possibility that our proposed mechanism can be extended to the case of multiple populations showing bimodality in the iron content, with the presence of two populations characterized by a small difference in [Fe/H]. Such a result can be obtained taking into account the contribution of delayed SN II.
Xu, Ying
2004-01-01
Many particle-laden flows in engineering applications involve turbulent gas flows. Modeling multiphase turbulent flows is an important research topic with applications in fluidized beds and particle conveying. A predictive multiphase turbulence model can help CFD codes to be more useful for engineering applications, such as the scale-up in the design of circulating fluidized combustor and coal gasifications. In engineering applications, the particle volume fraction can vary from dilute (<10^{-4}) to dense (~ 50%). It is reasonable to expect that multiphase turbulence models should at least satisfy some basic modeling and performance criteria and give reasonable predictions for the canonical problems in dilute particle-laden turbulent flows. In this research, a comparative assessment of predictions from Simonin and Ahmadi's turbulence models is performed with direct numerical simulation (DNS) for two canonical problems in particle-laden turbulent flows. Based on the comparative assessment, some criteria and the areas for model improvement are identified: (1) model for interphase TKE transfer, especially the time scale of interphase TKE transfer, and (2) correct prediction of TKE evolution with variation of particle Stokes number. Some deficiencies that are identified in the Simonin and Ahmadi models, limit the applicability. A new multiphase turbulence model, the Equilibration of Energy Model (EEM), is proposed in this work. In EEM, a multiscale interaction time scale is proposed to account for the interaction of a particle with a range of eddy sizes. EEM shows good agreement with the DNS results for particle-laden isotropic turbulence. For particle-laden homogeneous shear flows, model predictions from EEM can be further improved if the dissipation rate in fluid phase is modeled with more accuracy.
Kozłowska, Marta Karolina; Domańska, Urszula; Lempert, Małgorzata; Rogalski, Marek
2005-03-18
The partial molar volumes, V1(M), and the molar volume of isotactic crystalline low-molecular-weight poly(1-butene), iPBu-1, V1, have been calculated from the measured density of {iPBu-1 + solvent (n-hexane, n-heptane, n-nonane, n-decane, p-xylene, cyclohexane and chloroform)} systems. Some of the thermodynamic quantities were also obtained for the iPBu-1 with eight hydrocarbons (n-octane, n-decane, n-undecane, n-dodecane, n-tridecane, o-xylene, m-xylene, p-xylene) by the method of inverse gas chromatography at various temperatures. The weight fraction activity coefficients of the solvent at infinite dilution, omega2(infinity) and the Flory-Huggins thermodynamic interaction parameters, chi21(infinity), between polymer and solvents were determined. The partial molar free energy, deltaG2(infinity), the partial molar heat of mixing, deltaH2(infinity), at infinite dilution and the polymer solubility parameter, delta1, were calculated. Additionally, the (solid + liquid) binary mixtures equilibria, SLE, of iPBu-1 with three hydrocarbons (n-octane, n-decane and m-xylene) were studied by a dynamic method. By performing these experiments over a large concentration range, the T-x phase diagrams of the polymer-solvent systems were constructed. The excess Gibbs energy models were used to describe the nonideal behaviour of the liquid phase. The omega2(infinity) were determined from the solubility measurements and were predicted by using the UNIFAC FV model.
Experiments on hydrodynamic transport in ultra-cold bose gasses
NASA Astrophysics Data System (ADS)
Koller, S. B.
2012-09-01
At temperatures near the absolut zero, a gas, here atomic sodium vapour, with high enough density cannot be described as tiny balls moving around as in classical physics. Since the temperature is low, the atoms are so slow that the matterwave of each atom starts to extend over the size of the atom and even over the interatomic distance. Therefore, they start to interfere like waves. Quantum mechanics start to dominate the physics in this regime. Further, depending on the sort of atoms (bosons or fermions) the atoms prefer to be in the same state or avoid to be in the same state. In the case of bosons as in the thesis, if the temperature is lowered to sub micro Kelvin temperature, a new state of matter appears after a phase transition - a macroscopic, standing wave, the Bose-Einstein condensate. This leads to a new phenomena: superfluidity - frictionless flow, second sound, vorticity and coherent scattering effects to name a few. The atoms are trapped in a elongated trap as in most of the experiments in ultra cold gasses. Usually experiments are done in a regime where the atoms seldomly collide with each other while travelling from one end to the other end of the cloud. In this experiment, however, the atoms collide many times with each other when they oscillate in the trap. This means that the cloud is hydrodynamic and leads to a very different behaviour. Two different sound waves (first and second sound), heat conduction, and collisional dominated transport can be observed in this case. The fact that the gas is weakly interacting allows comparison with current theory. At very low temperatures as in the experiments described in the thesis, the Bose character strongly alters the collisions of the atoms. The outcome of the collision does not only depend on the colliding atoms, but also on the atoms near by in phase space. The experiments outlined in this thesis cover some aspects of physics involved. Vortices have been created and observed in the Bose
Revelli, Anne-Laure; Sprunger, Laura; Gibbs, Jennifer; Acree, William; Baker, Gary A; Mutelet, Fabrice
2009-01-01
Activity coefficients at infinite dilution of organic compounds in the ionic liquid (IL) trihexyl(tetradecyl) phosphonium bis(trifluoromethylsulfonyl)imide were determined using inverse gas chromatography at three temperatures, T ) (302.45, 322.35, and 342.45) K. Linear free energy relationship (LFER) correlations have been obtained for describing the gas-to-IL and water-to-IL partition coefficients.
Inhibition of Coherence in Trapped Bose-Einstein Condensates
Imamoglu, A.; Lewenstein, M.
1997-03-01
We analyze the dependence of the collapse and revival of many-atom coherence of a trapped Bose-Einstein condensate on the trap potential, dimensionality of the gas, and atom number fluctuations. We show that in a class of experimentally relevant systems the collapse time vanishes in the limit of a large number of atoms, implying that the trapped Bose gas cannot sustain a well-defined quantum phase. {copyright} {ital 1997} {ital The American Physical Society}
Molecular simulation study of the surface barrier effect. Dilute gas limit
Ford, D.M.; Glandt, E.D.
1995-07-20
The mass transfer resistance associated with penetrating the mouth of a very small pore is evaluated using classical molecular dynamics simulation techniques. The effects of temperature, pore size, and thermal motion of the adsorbent atoms are studied for a slit pore mouth model. Adsorption followed by surface diffusion to the pore mouth makes a significant contribution to the mass transfer when the temperature is low or, equivalently, when the adsorptive potential is strong. Thermal vibrations of the adsorbent atoms have little effect on the adsorption/surface diffusion mechanisms but cause fluctuations in the effective pore mouth area which can significantly affect transport rates. Perhaps the most important observation is that when the pore size approaches the kinetic diameter of the gas molecules, changes of a few percent in the pore size cause order-of-magnitude changes in the resistance. Therefore, it is possible that the surface barrier effect observed in zeolites and carbon molecular sieves is governed by highly localized (single atomic layer) structural details. 19 refs., 7 figs., 1 tab.
Zhou Kezhao; Liang Zhaoxin; Zhang Zhidong; Hu Ying
2010-10-15
We investigate a dilute Bose gas confined in a tight one-dimensional (1D) optical lattice plus a superimposed random potential at zero temperature. Accordingly, the ground-state energy, quantum depletion, and superfluid density are calculated. The presence of the lattice introduces a crossover to the quasi-two-dimensional (2D) regime, where we analyze asymptotically the 2D behavior of the system, particularly the effects of disorder. We thereby offer an analytical expression for the ground-state energy of a purely 2D Bose gas in a random potential. The obtained disorder-induced normal fluid density n{sub n} and quantum depletion n{sub d} both exhibit a characteristic 1/ln(1/n{sub 2D}a{sub 2D}{sup 2}) dependence. Their ratio n{sub n}/n{sub d} increases to 2 compared to the familiar 4/3 in lattice-free three-dimensional (3D) geometry, signifying a more pronounced contrast between superfluidity and Bose-Einstein condensation in low dimensions. The conditions for possible experimental realization of our scenario are also proposed.
Quantum phase transition of a Bose gas in a lattice with a controlled number of atoms per site
NASA Astrophysics Data System (ADS)
Du, Xu
2005-05-01
We have studied the superfluid-Mott insulator quantum phase transition [1] of a gas of ^87Rb atoms in an optical lattice. We are able to prepare the gas with a controllable number of one, two, or three atoms per lattice site, as verified with photoassociation spectroscopy. We measure momentum distributions using standard time-of-flight imaging techniques. These are similar to those of ref. [1], and exhibit narrow peaks at moderate lattice strengths. We find that the width of these peaks increases for lattice heights greater than about 13 times the recoil energy [2], and we observe interesting differences in this behavior, depending on the number of atoms per site. The data suggest that the quantum phase transition occurs at higher lattice strength with larger site occupation. We acknowledge the support of this work by the R. A. Welch Foundation, The N. S. F., and the D.O.E. Quantum Optics Initiative. [1] Markus Greiner et al., Nature 415, 39 (2002). [2] Thilo St"oferle et al., Phys. Rev. Lett. 92, 130403 (2004).
Tang, Chen; Liu, Qipeng; Tian, Zhenyu; Xie, Huiting; Wang, Mengjing; Liu, Wenbin
2014-09-01
A method for the determination of mono- to tri-chlorinated dibenzo-p-dioxins and dibenzofurans (mono- to tri-CDD/Fs) in stack gas using isotope dilution high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS) was developed. The sam- ples were extracted by Soxhlet extraction, and then the extracts were concentrated and purified using a multilayer silica gel column and a basic alumina column. The analytes were separated by HRGC on a DB-5MS column (30 m x 0.25 mm x 0.25 μm) and determined by HRMS. The identi- fication of mono- to tri-CDD/Fs was based on the retention times of 13C-labelled standard and the abundance ratios of the two exacted mass-to-charge ratios. The quantitative analysis was performed using the ratios of the integrated areas of the 13C-labelled standards. This method had the recoveries ranging from 66.6% to 112.5% and the relative standard deviations (RSD) ranging from 19.9% to 40.5% (n = 5). The limits of detection (LODs) of this method for the mono- to tri-CDD/Fs were ranging from 0.027 to 0.485 μg/L. Three stack gas samples from waste incinerators were measured using this method, with the recoveries ranging from 85.7% to 137.0% and the concentrations ranging from 11.4 to 9,183 pg/Nm3. The results indicated that the method can be applied to the precise determination of mono- to tri-CDD/Fs at trace level in stack gas.
Trinh, Trang; Harden, Nick B; Coleman, Heather M; Khan, Stuart J
2011-03-25
A rapid gas chromatography-tandem mass spectrometry (GC-MS/MS) analytical method was developed for the simultaneous analysis of 7 estrogenic hormones (17α-estradiol, 17β-estradiol, estrone, mestranol, 17α-ethynylestradiol, levonorgestrel, estriol) and 5 androgenic hormones (testosterone, androsterone, etiocholanolone, dihydrotestosterone, androstenedione) in aqueous matrices. This method is unique in its inclusion of all 12 of these estrogens and androgens and is of particular value due to its very short chromatographic run time of 15 min. The use of isotope dilution for all analytes ensures the accurate quantification, accounting for analytical variabilities that may be introduced during sample processing and instrumental analysis. Direct isotopically labelled analogues were used for 8 of the 12 hormones and satisfactory isotope standards were identified for the remaining 4 hormones. Method detection levels (MDLs) were determined to describe analyte concentrations sufficient to provide a signal with 99% certainty of detection. The established MDLs for most analytes were 1-5 ngL(-1) in a variety of aqueous matrices. However, slightly higher MDLs were observed for etiocholanolone, androstenedione, testosterone, levonorgestrel and dihydrotestosterone in some aqueous matrices. Sample matrices were observed to have only a minor impact on MDLs and the method validation confirmed satisfactory method stability over intra-day and inter-day analyses of surface water and tertiary treated effluent samples. Copyright © 2011 Elsevier B.V. All rights reserved.
Dilution and permeation standards for the generation of NO, NO2 and SO2 calibration gas mixtures
NASA Astrophysics Data System (ADS)
Haerri, H.-P.; Macé, T.; Waldén, J.; Pascale, C.; Niederhauser, B.; Wirtz, K.; Stovcik, V.; Sutour, C.; Couette, J.; Waldén, T.
2017-03-01
The evaluation results of the metrological performance of a dilution and a permeation standard for generating SI-traceable calibration gas mixtures of NO, SO2 and NO2 for ambient air measurements are presented. The composition of the in situ produced reference gas mixtures is calculated from the instantaneous values of the input quantities of the generating standards. In a measurement comparison, the calibration and measurement capabilities of five laboratories were evaluated for the three analytes at limiting amount of substance fractions in ambient air between 20 and 150 nmol mol-1. For the upper generated reference values the target relative uncertainties of ⩽2% (for NO and SO2) and ⩽3% (for NO2) for evaluating the laboratory results were fulfilled in 12 out of 13 cases. For the analytical results seven out of nine laboratories met the criteria for the upper values for NO and NO2, for SO2 it was one out of four. From the negative degrees of equivalence of all NO2 comparison results it was supposed that the permeation rate of NO2 through the FEP polymer membrane of the permeator was different in air and N2. Subsequent precision permeation measurements with various carrier gases revealed that the permeation rate of NO2 was ≈0.8% lower in synthetic air compared to N2. With the corrected NO2 reference values for air the degrees of equivalence of the laboratory results were improved and closer to be symmetrically distributed.
Stability analysis for n-component Bose-Einstein condensate
Roberts, David C.; Ueda, Masahito
2006-05-15
We derive the dynamic and thermodynamic stability conditions for dilute multicomponent Bose-Einstein condensates (BECs). These stability conditions, generalized for n-component BECs, are found to be equivalent and are shown to be consistent with the phase diagrams of two- and three-component condensates that are derived from energetic arguments.
Topological aspects in spinor Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Ueda, Masahito
2014-12-01
This article overviews topological excitations in spinor Bose-Einstein condensates of dilute atomic gases. Various types of line defects, point defects and skyrmions are discussed. A brief review of homotopy theory is presented for use in the classification of possible topological excitations in individual quantum phases. Some recent experiments are also reviewed.
Diletti, Gianfranco; Scortichini, Giampiero; Scarpone, Rossana; Gatti, Giuseppe; Torreti, Luigi; Migliorati, Giacomo
2005-01-14
A gas chromatographic (GC) method with mass spectrometry detection (MS) for the determination of eight polycyclic aromatic hydrocarbons (PAHs) in olive pomace oil has been developed. The oil was diluted with n-pentane and extracted by liquid-liquid partition with dimethyl sulphoxide (DMSO). After water addition and back-extraction with cyclohexane, a thin-layer chromatography on silica gel was performed as a further purification step. The PAHs spot was scraped off from the plate and the final extract was concentrated and analysed by GC-MS in full scan mode. The eight PAHs under investigation were determined in the presence of the corresponding labelled compounds added as internal standards to the sample at the beginning of the analytical process. The identified PAHs were then quantified by the isotope dilution methodology assuring the compensation of the concentration of each analyte for any variation in the sample preparation. The method precision was satisfactory with relative standard deviation (R.S.D.) values in the range 3.6-12.7% for all PAHs. The average recovery rates ranged from 69.0 to 97.5%. Accuracy was also calculated for benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene by analysing a certified reference material (CRM 458, coconut oil) with adequate results. All response curves exhibited a linear fit from 0.1 to 10 microg ml(-1) and the determination coefficients R2 were better than 0.9942. The limits of detection (0.1-0.4 microg kg(-1)) were acceptable when compared with the maximum permitted limit of 2 microg kg(-1) for each of the eight considered PAHs and 5 microg kg(-1) for the sum of the eight PAHs established by the Italian legislation. Measurement uncertainty was finally calculated identifying and quantifying the uncertainty components of the analytical process. The relative expanded uncertainties (Uc), expressed as percent values were in the range 8.5-11.4% thus appropriate for residues quantification in the
NASA Astrophysics Data System (ADS)
Solís, Miguel A.; Sevilla, Francisco J.; Fortes, Mauricio; de Llano, Manuel
2002-03-01
Cooper pair formation is studied in a 2D electron gas interacting pairwise through a finite-range, separable interfermion potential in wavevector space V_ kk^' =-(v_0/L^2)g_kg_k^' , where L^2 is the system area, v0 >= 0 the interaction strength, g_k≡ (1+k^2/k_0^2)-1/2 with k0 the inverse interaction range. The interaction strength v0 is eliminated [1] in favor of the (positive) binding energy B2 of an electron pair in vacuum under the same interfermion interaction. For finite range, i.e., 1/k_0>0, we report numerical calculations of the gap, the critical temperature and the chemical potential as functions of B2 and 1/k_0. For k_0= ∞ or zero-range (viz., a delta potential well) we recover at T=0 the well-known Miyake [2] results. Finally, the gap-to-Tc ratio is exhibited as a function of B2 and compared with other calculations as well as with empirical values for cuprate superconductors. [1] S.K. Adhikari, M. Casas, A. Puente, A. Rigo, M. Fortes, M.A. Solís, M. de Llano, A.A. Valladares and O. Rojo, Phys. Rev. B 62, 8671 (2000). [2] K. Miyake, Prog. Theor. Phys. 69, 1794 (1983). We thank UNAM-DGAPA-PAPIIT # IN102198 and CONACyT # 27828E for partial support.
Ground state energy of the δ-Bose and Fermi gas at weak coupling from double extrapolation
NASA Astrophysics Data System (ADS)
Prolhac, Sylvain
2017-04-01
We consider the ground state energy of the Lieb–Liniger gas with δ interaction in the weak coupling regime γ \\to 0 . For bosons with repulsive interaction, previous studies gave the expansion {{e}\\text{B}}≤ft(γ \\right)≃ γ -4{γ3/2}/3π +≤ft(1/6-1/{π2}\\right){γ2} . Using a numerical solution of the Lieb–Liniger integral equation discretized with M points and finite strength γ of the interaction, we obtain very accurate numerics for the next orders after extrapolation on M and γ. The coefficient of {γ5/2} in the expansion is found to be approximately equal to -0.001 587 699 865 505 944 989 29 , accurate within all digits shown. This value is supported by a numerical solution of the Bethe equations with N particles, followed by extrapolation on N and γ. It was identified as ≤ft(3\\zeta (3)/8-1/2\\right)/{π3} by G Lang. The next two coefficients are also guessed from the numerics. For balanced spin 1/2 fermions with attractive interaction, the best result so far for the ground state energy has been {{e}\\text{F}}≤ft(γ \\right)≃ {π2}/12-γ /2+{γ2}/6 . An analogue double extrapolation scheme leads to the value -\\zeta (3)/{π4} for the coefficient of {γ3} .
Bose-Einstein Condensation: Where Many Become One and So There is Plenty of Room at the Bottom
NASA Astrophysics Data System (ADS)
Kumar, N.
Classically identical particles become quantum mechanically indistinguishable. Satyendra Nath Bose taught us, in 1924, how to correctly count the distinct microstates for the indistinguishables, and for a gas of light quanta (later photons), whose number is not conserved, e.g. can vary with temperature, he gave a proper derivation of Planck's law of black body radiation. Einstein, in 1925, generalized the Bose statistics to a quantum gas of material particles whose number is now fixed, or conserved, e.g. 4He, and thus opened a new direction in condensed matter physics: He showed that for low enough temperatures (˜1 Kelvin and below), a oscopic number of the particles must accumulate in the lowest one-particle state. This degenerate gas with an extensively occupied single one-particle state is the Bose-Einstein condensate, now called BEC. (Fragmented BEC involving a multiplicity of internal states of non-scalar Bose atoms is, however, also realizable now.) Initially thought to be a pathology of an ideal non-interacting Bose system, the BEC turned out to be robust against interactions. Thus, the Bose-Einstein condensation is a quantum phase transition, but one with a difference — it is a purely quantum statistical effect, and requires no inter-particle interaction for its occurrence. Indeed, it happens in spite of it. The condensate fraction, however, diminishes with increasing interaction strength — to less than ten per cent for 4He. The BEC turned out to underlie superfluidity, namely that the superfluid may flow through finest atomic capillaries without any viscosity. Interaction, however, seems essential to superfluidity. But, the precise connection between BEC and the superfluidity remains elusive. Thus, for example, we may have superfluidity in two-dimensions where there is no condensate! Seventy years later now, the BEC has come alive with the breakthrough in 1995 when near-ideal BEC was created in dilute alkali gases of 87Rb and 23Na atoms cooled in the
Condensate fluctuations of interacting Bose gases within a microcanonical ensemble.
Wang, Jianhui; He, Jizhou; Ma, Yongli
2011-05-01
Based on counting statistics and Bogoliubov theory, we present a recurrence relation for the microcanonical partition function for a weakly interacting Bose gas with a finite number of particles in a cubic box. According to this microcanonical partition function, we calculate numerically the distribution function, condensate fraction, and condensate fluctuations for a finite and isolated Bose-Einstein condensate. For ideal and weakly interacting Bose gases, we compare the condensate fluctuations with those in the canonical ensemble. The present approach yields an accurate account of the condensate fluctuations for temperatures close to the critical region. We emphasize that the interactions between excited atoms turn out to be important for moderate temperatures.
Condensate fluctuations of interacting Bose gases within a microcanonical ensemble
Wang Jianhui; He Jizhou; Ma Yongli
2011-05-15
Based on counting statistics and Bogoliubov theory, we present a recurrence relation for the microcanonical partition function for a weakly interacting Bose gas with a finite number of particles in a cubic box. According to this microcanonical partition function, we calculate numerically the distribution function, condensate fraction, and condensate fluctuations for a finite and isolated Bose-Einstein condensate. For ideal and weakly interacting Bose gases, we compare the condensate fluctuations with those in the canonical ensemble. The present approach yields an accurate account of the condensate fluctuations for temperatures close to the critical region. We emphasize that the interactions between excited atoms turn out to be important for moderate temperatures.
Bose-Einstein condensate strings
NASA Astrophysics Data System (ADS)
Harko, Tiberiu; Lake, Matthew J.
2015-02-01
We consider the possible existence of gravitationally bound general relativistic strings consisting of Bose-Einstein condensate (BEC) matter which is described, in the Newtonian limit, by the zero temperature time-dependent nonlinear Schrödinger equation (the Gross-Pitaevskii equation), with repulsive interparticle interactions. In the Madelung representation of the wave function, the quantum dynamics of the condensate can be formulated in terms of the classical continuity equation and the hydrodynamic Euler equations. In the case of a condensate with quartic nonlinearity, the condensates can be described as a gas with two pressure terms, the interaction pressure, which is proportional to the square of the matter density, and the quantum pressure, which is without any classical analogue, though, when the number of particles in the system is high enough, the latter may be neglected. Assuming cylindrical symmetry, we analyze the physical properties of the BEC strings in both the interaction pressure and quantum pressure dominated limits, by numerically integrating the gravitational field equations. In this way we obtain a large class of stable stringlike astrophysical objects, whose basic parameters (mass density and radius) depend sensitively on the mass and scattering length of the condensate particle, as well as on the quantum pressure of the Bose-Einstein gas.
Three-body physics in quenched unitary Bose gases
NASA Astrophysics Data System (ADS)
D'Incao, Jose P.; Sykes, Andrew G.; Corson, John P.; Koller, Andrew P.; Greene, Chris H.; Rey, Ana M.; Hazzard, Kaden R. A.; Bohn, John L.
2014-05-01
A degenerate Bose gas, quenched to unitarity, displays rapid losses that are attributed to three-body recombination. The rate at which this occurs is an item of keen interest in producing and probing a unitary Bose gas. In this work we explore the three-body physics relevant for unitary Bose gases using the hyperspherical adiabatic representation and determine the population of Efimov states formed during the quench and their subsequent decay rate by assuming a local interaction model in which a harmonic potential mimics the finite density of other particles. Our findings, consistent with experiments at JILA, indicate that the three-body loss time scales are generally longer than the system's equilibration time, therefore bolstering this scheme as an efficient route to create and explore the dynamics of unitary Bose gases. Supported by National Science Foundation, AFOSR-MURI, ARO-MURI, NDSEG and NRC.
Kuhara, T
2001-07-05
This review will be concerned primarily with a practical yet comprehensive diagnostic procedure for the diagnosis or even mass screening of a variety of metabolic disorders. This rapid, highly sensitive procedure offers possibilities for clinical chemistry laboratories to extend their diagnostic capacity to new areas of metabolic disorders. The diagnostic procedure consists of the use of urine or filter paper urine, preincubation of urine with urease, stable isotope dilution, and gas chromatography-mass spectrometry. Sample preparation from urine or filter paper urine, creatinine determination, stable isotope-labeled compounds used, and GC-MS measurement conditions are described. Not only organic acids or polar ones but also amino acids, sugars, polyols, purines, pyrimidines and other compounds are simultaneously analyzed and quantified. In this review, a pilot study for screening of 22 target diseases in newborns we are conducting in Japan is described. A neonate with presymptomatic propionic acidemia was detected among 10,000 neonates in the pilot study. The metabolic profiles of patients with ornithine carbamoyl transferase deficiency, fructose-1,6-bisphosphatase deficiency or succinic semialdehyde dehydrogenase deficiency obtained by this method are presented as examples. They were compared to those obtained by the conventional solvent extraction methods or by the tandem mass spectrometric method currently done with dried filter blood spots. The highly sensitive, specific and comprehensive features of our procedure are also demonstrated by its use in establishing the chemical diagnosis of pyrimidine degradation defects in order to prevent side effects of pyrimidine analogs such as 5-flurouracil, and the differential diagnosis of three types of homocystinuria, orotic aciduria, uraciluria and other urea cycle disorders. Evaluation of the effects of liver transplantation or nutritional conditions such as folate deficiency in patients with inborn errors of
Vortices in a Bose-Einstein Condensate
NASA Astrophysics Data System (ADS)
Haljan, Paul C.
2004-05-01
Since the advent of Bose-Einstein condensation in the dilute alkalis, there has been considerable interest in observing effects in atomic condensates akin to the hallmark effects associated with superfluidity and superconductivity. In particular, the study of quantized vortices and vortex lattices represents an important connection between the traditional ``super" systems such as liquid Helium and this new atomic system. This thesis explores some of the first vortex experiments in a condensate of magnetically trapped Rubidium-87. Single vortex lines and rings are created using a wavefunction engineering technique, which is an ideal starting point to study the dynamical behavior of vortices within the condensate. An entirely different approach of ``intrinsic nucleation" has been developed to create rapidly rotating condensates with large amounts of vorticity. A novel variation of forced evaporation is used to simultaneously cool and spin up an ultracold gas. In this way, condensates can be formed that are rotating in excess of 95% of the centrifugal limit and contain large, extraordinarily regular lattices of well over 100 vortices. Direct detection of the vortex cores makes it possible to study the microscopic structure of the vortex arrangements both at equilibrium and under dynamical conditions where severe applied stresses distort the lattice far from its equilibrium configuration. In conclusion, the techniques developed in this work have helped to open up a new area of rotating condensate physics and, in the future, may lead to regimes of extreme rotation and quantum Hall physics. This work was performed at the University of Colorado, Boulder, under the supervision of Prof. Eric A. Cornell.
Ferroelectricity by Bose-Einstein condensation in a quantum magnet
NASA Astrophysics Data System (ADS)
Kimura, S.; Kakihata, K.; Sawada, Y.; Watanabe, K.; Matsumoto, M.; Hagiwara, M.; Tanaka, H.
2016-09-01
The Bose-Einstein condensation is a fascinating phenomenon, which results from quantum statistics for identical particles with an integer spin. Surprising properties, such as superfluidity, vortex quantization or Josephson effect, appear owing to the macroscopic quantum coherence, which spontaneously develops in Bose-Einstein condensates. Realization of Bose-Einstein condensation is not restricted in fluids like liquid helium, a superconducting phase of paired electrons in a metal and laser-cooled dilute alkali atoms. Bosonic quasi-particles like exciton-polariton and magnon in solids-state systems can also undergo Bose-Einstein condensation in certain conditions. Here, we report that the quantum coherence in Bose-Einstein condensate of the magnon quasi particles yields spontaneous electric polarization in the quantum magnet TlCuCl3, leading to remarkable magnetoelectric effect. Very soft ferroelectricity is realized as a consequence of the O(2) symmetry breaking by magnon Bose-Einstein condensation. The finding of this ferroelectricity will open a new window to explore multi-functionality of quantum magnets.
Ferroelectricity by Bose-Einstein condensation in a quantum magnet.
Kimura, S; Kakihata, K; Sawada, Y; Watanabe, K; Matsumoto, M; Hagiwara, M; Tanaka, H
2016-09-26
The Bose-Einstein condensation is a fascinating phenomenon, which results from quantum statistics for identical particles with an integer spin. Surprising properties, such as superfluidity, vortex quantization or Josephson effect, appear owing to the macroscopic quantum coherence, which spontaneously develops in Bose-Einstein condensates. Realization of Bose-Einstein condensation is not restricted in fluids like liquid helium, a superconducting phase of paired electrons in a metal and laser-cooled dilute alkali atoms. Bosonic quasi-particles like exciton-polariton and magnon in solids-state systems can also undergo Bose-Einstein condensation in certain conditions. Here, we report that the quantum coherence in Bose-Einstein condensate of the magnon quasi particles yields spontaneous electric polarization in the quantum magnet TlCuCl3, leading to remarkable magnetoelectric effect. Very soft ferroelectricity is realized as a consequence of the O(2) symmetry breaking by magnon Bose-Einstein condensation. The finding of this ferroelectricity will open a new window to explore multi-functionality of quantum magnets.
ERIC Educational Resources Information Center
Sudarshan, E. C. G.
1975-01-01
Describes a four page paper written by S. Bose who helped found quantum statistics. The consequences of the paper to modern physics are presented. Contrasted are the scientific relationships of Einstein, Dirac, and Bose. (GH)
ERIC Educational Resources Information Center
Sudarshan, E. C. G.
1975-01-01
Describes a four page paper written by S. Bose who helped found quantum statistics. The consequences of the paper to modern physics are presented. Contrasted are the scientific relationships of Einstein, Dirac, and Bose. (GH)
NASA Astrophysics Data System (ADS)
Darareh, M. Davoudi; Naderi, M. H.; Soltanolkotabi, M.
2009-12-01
We consider the interaction between an f-deformed Bose-Einstein condensate and a single-mode quantized light field. By using the Gardiner's phonon operators, we find that there exists a natural deformation in the model which modifies the Bogoliubov approximation under the condition of large but finite number of particles in condensate. This approach introduces an intrinsically deformed Bose-Einstein condensate, where the deformation parameter, well-defined by the particle number N in condensate, controls the strength of the associated nonlinearity. By introducing the deformed Gardiner's phonon operators we modify the very dilute-gas approximation through including atomic collisions in condensate. The rate of atomic collisions κ, as a new deformation parameter in the deformed Bose-Einstein condensate, controls the nonlinearity related to the atomic collisions. We show that by controlling the nonlinearities in the f-deformed atomic condensate through the two atomic parameters N and κ, it is possible to generate and manipulate the nonclassical quantum statistical properties of radiation field, such as, the sub-Poissonian photon statistics and quadrature squeezing. Also, it is possible to control the collapses and revivals phenomena in the average number of photons by atomic parameters N and κ.
NASA Astrophysics Data System (ADS)
Ardila, L. A. Peña; Giorgini, S.
2015-09-01
We investigate the properties of an impurity immersed in a dilute Bose gas at zero temperature using quantum Monte Carlo methods. The interactions between bosons are modeled by a hard-sphere potential with scattering length a , whereas the interactions between the impurity and the bosons are modeled by a short-range, square-well potential where both the sign and the strength of the scattering length b can be varied by adjusting the well depth. We characterize the attractive and the repulsive polaron branch by calculating the binding energy and the effective mass of the impurity. Furthermore, we investigate the structural properties of the bath, such as the impurity-boson contact parameter and the change of the density profile around the impurity. At the unitary limit of the impurity-boson interaction, we find that the effective mass of the impurity remains smaller than twice its bare mass, while the binding energy scales with ℏ2n2 /3/m , where n is the density of the bath and m is the common mass of the impurity and the bosons in the bath. The implications for the phase diagram of binary Bose-Bose mixtures at low concentrations are also discussed.
Reservoir interactions of a vortex in a trapped three-dimensional Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Rooney, S. J.; Allen, A. J.; Zülicke, U.; Proukakis, N. P.; Bradley, A. S.
2016-06-01
We simulate the dissipative evolution of a vortex in a trapped finite-temperature dilute-gas Bose-Einstein condensate using first-principles open-systems theory. Simulations of the complete stochastic projected Gross-Pitaevskii equation for a partially condensed Bose gas containing a single quantum vortex show that the transfer of condensate energy to the incoherent thermal component without population transfer provides an important channel for vortex decay. For the lower temperatures considered, this effect is significantly larger that the population transfer process underpinning the standard theory of vortex decay, and is the dominant determinant of the vortex lifetime. A comparison with the Zaremba-Nikuni-Griffin kinetic (two-fluid) theory further elucidates the role of the particle transfer interaction, and suggests the need for experimental testing of reservoir interaction theory. The dominance of this particular energetic decay mechanism for this open quantum system should be testable with current experimental setups, and its observation would have broad implications for the dynamics of atomic matter waves and experimental studies of dissipative phenomena.
Tokarczyk, Ryszard; Jiang, Ying; Poole, Gary; Turle, Richard
2010-10-29
A gas chromatography-mass spectrometry isotope dilution (GC-MS ID) method was developed and tested for the determination of 14 common glycol ethers in consumer products. Stable isotope labelled standards, 2-methoxyethanol-D(7) and 2-butoxyethanol-(13)C(2) (CDN isotopes) were employed to enhance the accuracy and precision of the glycol ethers determination. A 1000-fold sample dilution with methanol was applied to avoid column overload and contamination. At this dilution matrix effects were in most cases negligible and did not interfere with the analysis. The instrument detection limit (IDL) for analysed compounds varied from 0.01 to 1 μg/mL; while the estimated limit of quantification (LoQ) varied between different glycol ethers from 0.02 to 3.4 μg/mL. Calibration was tested in the range of 0.1-200 μg/mL and showed that the linear fit is upheld from 0.1 to 10 μg/mL, and extends beyond this range for some of the analytes. Recoveries of glycol ethers from products with different matrices were similar. The recoveries varied from 87% to 116% between the analysed compounds, while measurements precision varied between 2% and 14%. The method is applicable to products with glycol ether concentrations above 0.002-0.2% (w/w). The concentration range can be extended below the specified limits by decreasing the dilution factor; however, with lower dilution the sample matrix effect is expected to be stronger. Products with very high concentrations of glycol ether (>20%) may need to be further diluted prior to injection to avoid column overload. The method can be used for testing liquid and aerosol products designed for household use, such as cleaners, paints, solvents and paint stripers, for compliance and enforcement of regulations which limit glycol ethers content.
Auxiliary field formalism for dilute fermionic atom gases with tunable interactions
Mihaila, Bogdan; Chien, Chih-Chun; Timmermans, Eddy; Dawson, John F.; Cooper, Fred
2011-05-15
We develop the auxiliary field formalism corresponding to a dilute system of spin-1/2 fermions. This theory represents the Fermi counterpart of the Bose-Einstein condensation (BEC) theory developed recently by F. Cooper et al. [Phys. Rev. Lett. 105, 240402 (2010)] to describe a dilute gas of Bose particles. Assuming tunable interactions, this formalism is appropriate for the study of the crossover from the regime of Bardeen-Cooper-Schriffer (BCS) pairing to the regime of BEC in ultracold fermionic atom gases. We show that when applied to the Fermi case at zero temperature, the leading-order auxiliary field (LOAF) approximation gives the same equations as obtained in the standard BCS variational picture. At finite temperature, LOAF leads to the theory discussed by Sa de Melo, Randeria, and Engelbrecht [Phys. Rev. Lett. 71, 3202 (1993); Phys. Rev. B 55, 15153 (1997)]. As such, LOAF provides a unified framework to study the interacting Fermi gas. The mean-field results discussed here can be systematically improved on by calculating the one-particle irreducible action corrections, order by order.
Mixed-dimensional Bose polaron
NASA Astrophysics Data System (ADS)
Loft, Niels Jakob Søe; Wu, Zhigang; Bruun, G. M.
2017-09-01
A new generation of cold atom experiments trapping atomic mixtures in species-selective optical potentials opens up the intriguing possibility to create systems in which different atoms live in different spatial dimensions. Inspired by this, we investigate a mixed-dimensional Bose polaron consisting of an impurity particle moving in a two-dimensional (2D) layer immersed in a 3D Bose-Einstein condensate (BEC), using a theory that includes the mixed-dimensional vacuum scattering between the impurity and the bosons exactly. We show that similarly to the pure 3D case, this system exhibits a well-defined polaron state for attractive boson-impurity interaction that evolves smoothly into a mixed-dimensional dimer for strong attraction, as well as a well-defined polaron state for weak repulsive interaction, which becomes overdamped for strong interaction. We furthermore find that the properties of the polaron depend only weakly on the gas parameter of the BEC as long as the Bogoliubov theory remains a valid description for the BEC. This indicates that higher-order correlations between the impurity and the bosons are suppressed by the mixed-dimensional geometry in comparison to a pure 3D system, which led us to speculate that the mixed-dimensional polaron has universal properties in the unitarity limit of the impurity-boson interaction.
Nguyen, Ngoc N.; Nguyen, Anh V.; Nguyen, Khoi T.; Rintoul, Llew; Dang, Liem X.
2016-12-01
Gas hydrates formed under moderated conditions open up novel approaches to tackling issues related to energy supply, gas separation, and CO_{2} sequestration. Several additives like tetra-n-butylammonium bromide (TBAB) have been empirically developed and used to promote gas hydrate formation. Here we report unexpected experimental results which show that TBAB inhibits CO_{2} gas hydrate formation when used at minuscule concentration. We also used spectroscopic techniques and molecular dynamics simulation to gain further insights and explain the experimental results. They have revealed the critical role of water alignment at the gas-water interface induced by surface adsorption of tetra-n-butylammonium cation (TBA^{+}) which gives rise to the unexpected inhibition of dilute TBAB solution. The water perturbation by TBA^{+} in the bulk is attributed to the promotion effect of high TBAB concentration on gas hydrate formation. We explain our finding using the concept of activation energy of gas hydrate formation. Our results provide a step toward to mastering the control of gas hydrate formation.
Pavez, Carolina; Agosin, Eduardo; Steinhaus, Martin
2016-05-04
The sensory impact of thiols in Vitis vinifera 'Carmenere' red wines was evaluated. For this purpose, aroma extract dilution analysis was applied to the thiols isolated from a Carmenere red wine by affinity chromatography with a mercurated agarose gel. Results revealed the presence of four odorants, identified as 2-furanylmethanethiol, 3-sulfanylhexyl acetate, 3-sulfanyl-1-hexanol, and 2-methyl-3-sulfanyl-1-butanol, with the latter being described here for the first time in Carmenere red wines. Quantitation of the four thiols in the Carmenere wine screened by aroma extract dilution analysis and in three additional Carmenere wines by stable isotope dilution assays resulted in concentrations above the respective orthonasal odor detection threshold values. Triangle tests applied to wine model solutions with and without the addition of the four thiols showed significant differences, thus suggesting that the compounds do have the potential to influence the overall aroma of red wine.
Predicted signatures of rotating Bose-Einstein Condensates
Butts, D.A.; Rokhsar, D.S.
1999-01-01
Superfluids are distinguished from normal fluidsby theirpeculiar response1 to rotation: circulating flow in superfuid helium2,3,astrongly coupled Bose liquid, can appear only as quantized vortices4-6.The newly created Bose-Einstein condensates7,9--clouds of millions ofultracold, weakly interacting alkali-metal atoms that occupy a singlequantum state Doffer the possibility of investigating superuidity in theweak-coupling regime. An outstanding question is whether Bose-Einsteincondensates exhibit a mesoscopic quantum analogue of the macroscopicvortices in superfluids, and what its experimental signature would be.Here we report calculations of the low-energy states of a rotating,weakly interacting Bose gas. We find a succession of transitions betweenstab reement with observations5 of rotating super-fluid helium, astrong-coupling superfuid. Counterintuitively, the angular momentum perparticle is not quantized. Some angular momenta are forbidden,corresponding to asymmetrical unstablestates that provide a physicalmechanism for the entry of vorticity into the condensate.
Kang, Kyung-Mo; Baek, Hyung-Hee
2014-02-15
The objective of this study was to assess aroma quality of gochujang using purge and trap, simultaneous steam distillation and solvent extraction (SDE), and headspace solid-phase microextraction (HS-SPME), followed by gas chromatography-olfactometry (GC-O). Nineteen and 28 aroma-active compounds were detected by aroma extract dilution analysis of purge and trap and SDE, respectively. Diallyl disulfide and 3-isobutyl-2-methoxypyrazine played a significant role in the aroma quality of gochujang. Twelve aroma-active compounds were detected by HS-SPME-GC-O based on sample dilution analysis. Methional, diallyl disulfide, and 3-isobutyl-2-methoxypyrazine were the most intense aroma-active compounds. 3-Isobutyl-2-methoxypyrazine was identified for the first time in gochujang.
Observation of Vortex Dipoles in an Oblate Bose-Einstein Condensate
Neely, T. W.; Samson, E. C.; Bradley, A. S.; Davis, M. J.; Anderson, B. P.
2010-04-23
We report experimental observations and numerical simulations of the formation, dynamics, and lifetimes of single and multiply charged quantized vortex dipoles in highly oblate dilute-gas Bose-Einstein condensates (BECs). We nucleate pairs of vortices of opposite charge (vortex dipoles) by forcing superfluid flow around a repulsive Gaussian obstacle within the BEC. By controlling the flow velocity we determine the critical velocity for the nucleation of a single vortex dipole, with excellent agreement between experimental and numerical results. We present measurements of vortex dipole dynamics, finding that the vortex cores of opposite charge can exist for many seconds and that annihilation is inhibited in our trap geometry. For sufficiently rapid flow velocities, clusters of like-charge vortices aggregate into long-lived multiply charged dipolar flow structures.
Signals of Bose Einstein condensation and Fermi quenching in the decay of hot nuclear systems
NASA Astrophysics Data System (ADS)
Marini, P.; Zheng, H.; Boisjoli, M.; Verde, G.; Chbihi, A.; Napolitani, P.; Ademard, G.; Augey, L.; Bhattacharya, C.; Borderie, B.; Bougault, R.; Frankland, J. D.; Fable, Q.; Galichet, E.; Gruyer, D.; Kundu, S.; La Commara, M.; Lombardo, I.; Lopez, O.; Mukherjee, G.; Parlog, M.; Rivet, M. F.; Rosato, E.; Roy, R.; Spadaccini, G.; Vigilante, M.; Wigg, P. C.; Bonasera, A.
2016-05-01
We report on first experimental observations of nuclear fermionic and bosonic components displaying different behaviours in the decay of hot Ca projectile-like sources produced in mid-peripheral collisions at sub-Fermi energies. The experimental setup, constituted by the coupling of the INDRA 4π detector array to the forward angle VAMOS magnetic spectrometer, allowed to reconstruct the mass, charge and excitation energy of the decaying hot projectile-like sources. By means of quantum-fluctuation analysis techniques, temperatures and local partial densities of bosons and fermions could be correlated to the excitation energy of the reconstructed system. The results are consistent with the production of dilute mixed systems of bosons and fermions, where bosons experience higher phase-space and energy density as compared to the surrounding fermionic gas. Our findings recall phenomena observed in the study of Bose condensates and Fermi gases in atomic traps despite the different scales.
Observation of vortex dipoles in an oblate Bose-Einstein condensate.
Neely, T W; Samson, E C; Bradley, A S; Davis, M J; Anderson, B P
2010-04-23
We report experimental observations and numerical simulations of the formation, dynamics, and lifetimes of single and multiply charged quantized vortex dipoles in highly oblate dilute-gas Bose-Einstein condensates (BECs). We nucleate pairs of vortices of opposite charge (vortex dipoles) by forcing superfluid flow around a repulsive Gaussian obstacle within the BEC. By controlling the flow velocity we determine the critical velocity for the nucleation of a single vortex dipole, with excellent agreement between experimental and numerical results. We present measurements of vortex dipole dynamics, finding that the vortex cores of opposite charge can exist for many seconds and that annihilation is inhibited in our trap geometry. For sufficiently rapid flow velocities, clusters of like-charge vortices aggregate into long-lived multiply charged dipolar flow structures.
NASA Astrophysics Data System (ADS)
Wang, Botao; Jiang, Ying
2016-11-01
We investigate the disorder effect on coherent fraction and the quantum phase transition of ultracold dilute Bose gases trapped in disordered optical lattices. Within the framework of Bogoliubov theory, an analytical expression for the particle density is derived and the dependence of coherent fraction on disorder strength as well as on lattice depth is discussed. In weak disorder regime, we find a decreased sensitivity of coherent fraction to disorder with the increase of on-site interaction strength. For strong disorder, the quantum phase boundary between superfluid phase and Bose glass phase in the disordered Bose-Hubbard system in weak interaction regime is discussed qualitatively. The obtained phase diagram is in agreement with the empirical square-root law. The dependence of the corresponding critical value of the disorder strength on optical lattice depth is presented as well, and may serve as a reference object for possible experimental investigation.
Dilute Nitride GaNP Wide Bandgap Solar Cells Grown by Gas-Source Molecular Beam Epitaxy
NASA Astrophysics Data System (ADS)
Sukrittanon, Supanee
Integration of III-V semiconductors and Si is a very attractive means to achieve low-cost high-efficiency solar cells. A promising configuration is to utilize a dual-junction solar cell, in which Si is employed as the bottom junction and a wide-bandgap III-V semiconductor as the top junction. The use of a III-V semiconductor as a top junction offers the potential to achieve higher efficiencies than today's best Si solar cell. Dilute nitride GaNP is a promising candidate for the top cell in dual-junction solar cells because it possesses several extremely important attributes: a direct-bandgap that is also tunable as well as easily-attained lattice-match with Si. As a first step towards integration of GaNP solar cells onto Si, the goal of this dissertation is to optimize and demonstrate GaNP solar cells grown by gas-source molecular beam epitaxy (GSMBE) on GaP (001) substrate. The dissertation is divided into three major parts. In the first part, we demonstrate ˜ 2.05 eV ([N]˜ 1.8%) dilute nitride GaNP thin film solar cells, in which the GaNP is closely lattice-matched to Si, on GaP substrates. From transmission electron microscopy (TEM), the device exhibits defects only at the GaNP/GaP interface, and no threading dislocations in an active layer are observed. Our best GaNP solar cell achieved an efficiency of 7.9% with anti-reflection (AR) coating and no window layer. This GaNP solar cell's efficiency is higher than the most efficient GaP solar cell to date and higher than other solar cells with similar direct bandgap (InGaP, GaAsP). Through a systematic study of the structural, electrical, and optical properties of the device, efficient broadband optical absorption and enhanced solar cell performance using GaNP are demonstrated. In the second part, we demonstrate the successful fabrication of GaP/GaNP core/shell microwires utilizing a novel technique: top-down reactive-ion etching (RIE) to create the cores and MBE to create the shells. Systematic studies have been
Barr, John R; Driskell, W J; Aston, Linda S; Martinez, Rodolfo A
2004-01-01
Organophosphorus nerve agents are among the most toxic organic compounds known and continue to be a threat for both military and terrorist use. We have developed an isotope-dilution gas chromatography-tandem mass spectrometric (GC-MS-MS) method for quantitating the urinary metabolites of the organophosphorus nerve agents sarin (GB), soman (GD), VX, Russian VX (RVX), and cyclohexylsarin (GF). Urine samples were acidified, extracted into ether-acetonitrile, derivatized by methylation with diazomethane, and analyzed by GC-MS-MS. The limits of detection were less than 1 micro g/L for all analytes.
Constraints on Bose-Einstein-condensed axion dark matter from the Hi nearby galaxy survey data
NASA Astrophysics Data System (ADS)
Li, Ming-Hua; Li, Zhi-Bing
2014-05-01
One of the leading candidates for dark matter is the axion or axionlike particle in the form of a Bose-Einstein condensate (BEC). In this paper, we present an analysis of 17 high-resolution galactic rotation curves from the Hi nearby galaxy survey (THINGS) data [F. Walter et al., Astron. J. 136, 2563 (2008)] in the context of the axionic Bose-Einstein condensed dark matter model. Assuming a repulsive two-body interaction, we solve the nonrelativistic Gross-Pitaevskii equation for N gravitationally trapped bosons in the Thomas-Fermi approximation. We obtain the maximum possible radius R and the mass profile M(r) of a dilute axionic Bose-Einstein condensed gas cloud. A standard least- χ2 method is employed to find the best-fit values of the total mass M of the axion BEC and its radius R. The local mass density of BEC axion dark matter is ρa ≃0.02 GeV /cm3, which agrees with that presented by Beck [C. Beck, Phys. Rev. Lett. 111, 231801 (2013)]. The axion mass ma we obtain depends not only on the best-fit value of R, but also on the s-wave scattering length a (ma∝a1/3). The transition temperature Ta of an axion BEC on galactic scales is also estimated. Comparing the calculated Ta with the ambient temperature of galaxies and galaxy clusters implies that a ˜10-3 fm. The corresponding axion mass is ma≃0.58 meV. We compare our results with others.
NASA Astrophysics Data System (ADS)
Nedea, S. V.; Frijns, A. J. H.; van Steenhoven, A. A.; Markvoort, A. J.; Hilbers, P. A. J.
2005-05-01
We present a hybrid method to study the properties of hard-sphere gas molecules confined between two hard walls of a microchannel. The coupling between Molecular Dynamics(MD) and Monte Carlo(MC) simulations is introduced in order to combine the advantages of the MD and MC simulations, by performing MD near the boundaries for the accuracy of the interactions with the wall, and MC in the bulk because of the low computational cost. The effect of different gas densities, starting from a rarefied gas (reduced density η=πna3/6=0.001, where n=number density, a=molecular diameter) to a dense hard-sphere gas (η=0.25), is investigated. We characterize the influence of different η's and size of molecules on the equilibrium properties of the gas in a microchannel. The effect of the particle size on the simulation results, which is very small in case of a dilute gas, is increasing with η. Comparisons between MD, MC and hybrid MD-MC simulation results are done, and comparisons between MD, MC, and hybrid MD-MC computational costs are outlined.
Noise thermometry with two weakly coupled Bose-Einstein condensates.
Gati, Rudolf; Hemmerling, Börge; Fölling, Jonas; Albiez, Michael; Oberthaler, Markus K
2006-04-07
Here we report on the experimental investigation of thermally induced fluctuations of the relative phase between two Bose-Einstein condensates which are coupled via tunneling. The experimental control over the coupling strength and the temperature of the thermal background allows for the quantitative analysis of the phase fluctuations. Furthermore, we demonstrate the application of these measurements for thermometry in a regime where standard methods fail. With this we confirm that the heat capacity of an ideal Bose gas deviates from that of a classical gas as predicted by the third law of thermodynamics.
Composite fermion basis for M-component Bose gases
NASA Astrophysics Data System (ADS)
Skogvoll, V.; Liabøtrø, O.
2017-10-01
The composite fermion (CF) formalism produces wave functions that are not always linearly independent. This is especially so in the low angular momentum regime in the lowest Landau level, where a subclass of CF states, known as simple states, gives a good description of the low energy spectrum. For the two-component Bose gas, explicit bases avoiding the large number of redundant states have been found. We generalize one of these bases to the M-component Bose gas and prove its validity. We also show that the numbers of linearly independent simple states for different values of angular momentum are given by coefficients of q-multinomials.
Analytical approach to relaxation dynamics of condensed Bose gases
Escobedo, Miguel; Pezzotti, Federica; Valle, Manuel
2011-04-15
Research Highlights: > Time evolution of perturbations from equilibrium in a condensed Bose gas is studied. > Just below the critical temperature the perturbations vanish algebraically. > Anisotropic perturbations are unstable. > At very low temperature perturbations decay exponentially. - Abstract: The temporal evolution of a perturbation of the equilibrium distribution of a condensed Bose gas is investigated using the kinetic equation which describes collision between condensate and noncondensate atoms. The dynamics is studied in the low momentum limit where an analytical treatment is feasible. Explicit results are given for the behavior at large times in different temperature regimes.
Ferreira, V; Aznar, M; López, R; Cacho, J
2001-10-01
Four Spanish aged red wines made in different wine-making areas have been extracted, and the extracts and their 1:5, 1:50, and 1:500 dilutions have been analyzed by a gas chromatography-olfactometry (GC-O) approach in which three judges evaluated odor intensity on a four-point scale. Sixty-nine different odor regions were detected in the GC-O profiles of wines, 63 of which could be identified. GC-O data have been processed to calculate averaged flavor dilution factors (FD). Different ANOVA strategies have been further applied on FD and on intensity data to check for significant differences among wines and to assess the effects of dilution and the judge. Data show that FD and the average intensity of the odorants are strongly correlated (r(2) = 0.892). However, the measurement of intensity represents a quantitative advantage in terms of detecting differences. For some odorants, dilution exerts a critical role in the detection of differences. Significant differences among wines have been found in 30 of the 69 odorants detected in the experiment. Most of these differences are introduced by grape compounds such as methyl benzoate and terpenols, by compounds released by the wood, such as furfural, (Z)-whiskey lactone, Furaneol, 4-propylguaiacol, eugenol, 4-ethylphenol, 2,6-dimethoxyphenol, isoeugenol, and ethyl vanillate, by compounds formed by lactic acid bacteria, such as 2,3-butanedione and acetoine, or by compounds formed during the oxidative storage of wines, such as methional, sotolon, o-aminoacetophenone, and phenylacetic acid. The most important differences from a quantitative point of view are due to 2-methyl-3-mercaptofuran, 4-propylguaiacol, 2,6-dimethoxyphenol, and isoeugenol.
Oscillons in coupled Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Su, Shih-Wei; Gou, Shih-Chuan; Liu, I.-Kang; Bradley, Ashton S.; Fialko, Oleksandr; Brand, Joachim
2015-02-01
Long-lived, spatially localized, and temporally oscillating nonlinear excitations are predicted by numerical simulation of coupled Gross-Pitaevskii equations. These oscillons closely resemble the time-periodic breather solutions of the sine-Gordon equation but decay slowly by radiating Bogoliubov phonons. Their time-dependent profile is closely matched with solutions of the sine-Gordon equation, which emerges as an effective field theory for the relative phase of two linearly coupled Bose fields in the weak-coupling limit. For strong coupling the long-lived oscillons persist and involve both relative and total phase fields. The oscillons decay via Bogoliubov phonon radiation that is increasingly suppressed for decreasing oscillon amplitude. Possibilities for creating oscillons are addressed in atomic gas experiments by collision of oppositely charged Bose-Josephson vortices and direct phase imprinting.
Rotons in Interacting Ultracold Bose Gases
Cormack, Samuel C.; Schumayer, Daniel; Hutchinson, David A. W.
2011-09-30
In three dimensions, noninteracting bosons undergo Bose-Einstein condensation at a critical temperature, T{sub c}, which is slightly shifted by {Delta}T{sub c}, if the particles interact. We calculate the excitation spectrum of interacting Bose systems, {sup 4}He and {sup 87}Rb, and show that a roton minimum emerges in the spectrum above a threshold value of the gas parameter. We provide a general theoretical argument for why the roton minimum and the maximal upward critical temperature shift are related. We also suggest two experimental avenues to observe rotons in condensates. These results, based upon a path-integral Monte Carlo approach, provide a microscopic explanation of the shift in the critical temperature and also show that a roton minimum does emerge in the excitation spectrum of particles with a structureless, short-range, two-body interaction.
England, Glenn C; Watson, John G; Chow, Judith C; Zielinska, Barbara; Chang, M C Oliver; Loos, Karl R; Hidy, George M
2007-01-01
With the recent focus on fine particle matter (PM2.5), new, self-consistent data are needed to characterize emissions from combustion sources. Such data are necessary for health assessment and air quality modeling. To address this need, emissions data for gas-fired combustors are presented here, using dilution sampling as the reference. The dilution method allows for collection of emitted particles under conditions simulating cooling and dilution during entry from the stack into the air. The sampling and analysis of the collected particles in the presence of precursor gases, SO2 nitrogen oxide, volatile organic compound, and NH3 is discussed; the results include data from eight gas fired units, including a dual-fuel institutional boiler and a diesel engine powered electricity generator. These data are compared with results in the literature for heavy-duty diesel vehicles and stationary sources using coal or wood as fuels. The results show that the gas-fired combustors have very low PM2.5 mass emission rates in the range of approximately 10(-4) lb/million Btu (MMBTU) compared with the diesel backup generator with particle filter, with approximately 5 x 10(-3) lb/MMBTU. Even higher mass emission rates are found in coal-fired systems, with rates of approximately 0.07 lb/MMBTU for a bag-filter-controlled pilot unit burning eastern bituminous coal. The characterization of PM2.5 chemical composition from the gas-fired units indicates that much of the measured primary particle mass in PM2.5 samples is organic or elemental carbon and, to a much less extent, sulfate. Metal emissions are quite low compared with the diesel engines and the coal- or wood-fueled combustors. The metals found in the gas-fired combustor particles are low in concentration, similar in concentration to ambient particles. The interpretation of the particulate carbon emissions is complicated by the fact that an approximately equal amount of particulate carbon (mainly organic carbon) is found on the
NASA Astrophysics Data System (ADS)
Moret-Bailly, J.
In the study of experiments of laser spectroscopy, there appears a convergence of the methods of quantum electrodynamics and classical optics: for instance stochastic electrodynamics used for the study of "squeezed states" is common to both theories, and the quantum coherent states are almost classical states. The author shows that this convergence allows to explain the paradoxes of quantum mechanics. The interaction of ultrashort laser pulses with ordinary matter is equivalent to the interaction of incoherent light with extremely dilute gases. Thus, the interaction of light from stars with cosmic gas produces a redshift similar to the Doppler redshift. In a very low pressure gas, the absorption of incoherent light disappears completely, so that the "black matter" could be simply H2 and its products of decomposition by high-frequency radiation.
NASA Astrophysics Data System (ADS)
Wang, Chao; Zhang, Jingyu; Gao, Wenbin; Ding, Hongbing; Wu, Weiping
2015-11-01
The gas-solid two-phase flow has been widely applied in the power, chemical and metallurgical industries. It is of great significance in the research of gas-solid two-phase flow to measure particle velocity at different locations in the pipeline. Thus, an electrostatic sensor array comprising eight arc-shaped electrodes was designed. The relationship between the cross-correlation (CC) velocity and the distribution of particle velocity, charge density and electrode spatial sensitivity was analysed. Then the CC sensitivity and its calculation method were proposed. According to the distribution of CC sensitivity, it was found that, between different electrode pairs, it had different focus areas. The CC focus method was proposed for particle velocity measurement at different locations and validated by a belt-style electrostatic induction experiment facility. Finally, the particle velocities at different locations with different flow conditions were measured to research the particle velocity distribution in a dilute horizontal pneumatic conveying pipeline.
NASA Astrophysics Data System (ADS)
Abe, Yusuke; Ishikawa, Kenji; Takeda, Keigo; Tsutsumi, Takayoshi; Fukushima, Atsushi; Kondo, Hiroki; Sekine, Makoto; Hori, Masaru
2017-01-01
Microcrystalline hydrogenated silicon films were produced at a high deposition rate of about 2 nm/s by using a capacitively coupled plasma under a practical pressure of around 1 kPa. The SiH4 source gas was almost fully dissociated when highly diluted with H2 gas, and the dominant species in the gas phase were found to be SiH3 radicals, which are film-growth precursors, and H atoms. The absolute density of these species was measured as the partial pressure of SiH4 gas was varied. With the increasing SiH4 gas flow rate, the SiH3 radical density, which was on the order of 1012 cm-3, increased linearly, while the H-atom density remained constant at about 1012 cm-3. The film growth mechanism was described in terms of precursors, based on the measured flux of SiH3 radicals and H atoms, and the relative fraction of higher-order radicals.
Nedea, S V; van Steenhoven, A A; Markvoort, A J; Spijker, P; Giordano, D
2014-05-01
The influence of gas-surface interactions of a dilute gas confined between two parallel walls on the heat flux predictions is investigated using a combined Monte Carlo (MC) and molecular dynamics (MD) approach. The accommodation coefficients are computed from the temperature of incident and reflected molecules in molecular dynamics and used as effective coefficients in Maxwell-like boundary conditions in Monte Carlo simulations. Hydrophobic and hydrophilic wall interactions are studied, and the effect of the gas-surface interaction potential on the heat flux and other characteristic parameters like density and temperature is shown. The heat flux dependence on the accommodation coefficient is shown for different fluid-wall mass ratios. We find that the accommodation coefficient is increasing considerably when the mass ratio is decreased. An effective map of the heat flux depending on the accommodation coefficient is given and we show that MC heat flux predictions using Maxwell boundary conditions based on the accommodation coefficient give good results when compared to pure molecular dynamics heat predictions. The accommodation coefficients computed for a dilute gas for different gas-wall interaction parameters and mass ratios are transferred to compute the heat flux predictions for a dense gas. Comparison of the heat fluxes derived using explicit MD, MC with Maxwell-like boundary conditions based on the accommodation coefficients, and pure Maxwell boundary conditions are discussed. A map of the heat flux dependence on the accommodation coefficients for a dense gas, and the effective accommodation coefficients for different gas-wall interactions are given. In the end, this approach is applied to study the gas-surface interactions of argon and xenon molecules on a platinum surface. The derived accommodation coefficients are compared with values of experimental results.
Two-component Bose gases under rotation
Bargi, S.; Kaerkkaeinen, K.; Christensson, J.; Reimann, S. M.; Kavoulakis, G. M.; Manninen, M.
2008-04-04
We examine the formation of vortices in a one- and two-component gas of bosonic atoms in a harmonic trap that is set rotating. Both the mean-field Gross-Pitaevskii approach, and the numerical diagonalization method are employed. For a two-component Bose gas, we show that beside the well-known coreless vortices of single quantization, the interatomic interactions between the two species may lead to coreless vortices of multiple quantization. We furthermore comment on the geometries of the interlaced vortex patterns. In the limit of weak interactions, we finally demonstrate a number of exact results.
NASA Astrophysics Data System (ADS)
Sargent, S.; Somers, J. M.
2015-12-01
Trace-gas eddy covariance flux measurement can be made with open-path or closed-path analyzers. Traditional closed-path trace-gas analyzers use multipass absorption cells that behave as mixing volumes, requiring high sample flow rates to achieve useful frequency response. The high sample flow rate and the need to keep the multipass cell extremely clean dictates the use of a fine-pore filter that may clog quickly. A large-capacity filter cannot be used because it would degrade the EC system frequency response. The high flow rate also requires a powerful vacuum pump, which will typically consume on the order of 1000 W. The analyzer must measure water vapor for spectroscopic and dilution corrections. Open-path analyzers are available for methane, but not for nitrous oxide. The currently available methane analyzers have low power consumption, but are very large. Their large size degrades frequency response and disturbs the air flow near the sonic anemometer. They require significant maintenance to keep the exposed multipass optical surfaces clean. Water vapor measurements for dilution and spectroscopic corrections require a separate water vapor analyzer. A new closed-path eddy covariance system for measuring nitrous oxide or methane fluxes provides an elegant solution. The analyzer (TGA200A, Campbell Scientific, Inc.) uses a thermoelectrically-cooled interband cascade laser. Its small sample-cell volume and unique sample-cell configuration (200 ml, 1.5 m single pass) provide excellent frequency response with a low-power scroll pump (240 W). A new single-tube Nafion® dryer removes most of the water vapor, and attenuates fluctuations in the residual water vapor. Finally, a vortex intake assembly eliminates the need for an intake filter without adding volume that would degrade system frequency response. Laboratory testing shows the system attenuates the water vapor dilution term by more than 99% and achieves a half-power band width of 3.5 Hz.
Cueto Díaz, Sergio; Ruiz Encinar, Jorge; Sanz-Medel, Alfredo; García Alonso, J Ignacio
2010-08-15
A quadrupole GC-MS instrument with an electron ionization (EI) source has been modified to enable application of postcolumn isotope dilution analysis for the standardless quantification of organic compounds injected in the gas chromatograph. Instrumental modifications included the quantitative conversion of the separated compounds into CO(2), using a postcolumn combustion furnace, and the subsequent mixing of the gas with a constant flow of (13)CO(2) diluted in helium. The online measurement of the (12)CO(2)/(13)CO(2) (44/45) ratio in the EI-MS allowed us to obtain quantitative data without resorting to compound-specific standards. Validation of the procedure involved the analysis of standard solutions containing different families of organic compounds (C(9)-C(20) linear hydrocarbons, BTEX and esters) obtaining satisfactory results in all cases in terms of absolute errors (<6%) and precision (<4% RSD). The developed procedure showed excellent linearity over the range assayed (2 orders of magnitude) and adequate detection limits for carbon containing compounds (0.8 pg C s(-1)). The generic value of this compound-independent calibration approach was assessed by studying the quantitative performance of Head Space-Solid Phase Microextraction (HS-SPME). The proposed compound-independent quantification by EI-MS permits comparison of the performance of different fibers by assessing analyte recoveries with extreme robustness, simplicity, and precision.
NASA Astrophysics Data System (ADS)
Leuenberger, Daiana; Pascale, Céline; Guillevic, Myriam; Ackermann, Andreas; Niederhauser, Bernhard
2017-04-01
Ammonia (NH3) in the atmosphere is the major precursor for neutralising atmospheric acids and is thus affecting not only the long-range transport of sulphur dioxide and nitrogen oxides but also stabilises secondary particulate matter. These aerosols have negative impacts on air quality and human health. Moreover, they negatively affect terrestrial ecosystems after deposition. NH3 has been included in the air quality monitoring networks and emission reduction directives of European nations. Atmospheric concentrations are in the order of 0.5-500 nmol/mol. However, the lowest substance amount fraction of available certified reference material (CRM) is 10 μmol/mol. This due to the fact that adsorption on the walls of aluminium cylinders and desorption as pressure in the cylinder decreases cause substantial instabilities in the amount fractions of the gas mixtures. Moreover, analytical techniques to be calibrated are very diverse and cause challenges for the production and application of CRM. The Federal Institute of Metrology METAS has developed, partially in the framework of EMRP JRP ENV55 MetNH3, an infrastructure to meet with the different requirements in order to generate SI-traceable NH3 reference gas mixtures dynamically in the amount fraction range 0.5-500 nmol/mol and with uncertainties UNH3 <3%. The infrastructure consists of a stationary as well as a mobile device for full flexibility in the application: In the stationary system, a magnetic suspension balance monitors the specific temperature and pressure dependent mass loss over time of the pure substance in a permeation tube (here NH3) by permeation through a membrane into a constant flow of carrier gas. Subsequently, this mixture is diluted with a system of thermal mass flow controllers in one or two consecutive steps to desired amount fractions. The permeation tube with calibrated permeation rate (mass loss over time previously determined in the magnetic suspension balance) can be transferred into the
Multiple condensed phases in attractively interacting Bose systems
NASA Astrophysics Data System (ADS)
Männel, M.; Morawetz, K.; Lipavský, P.
2010-03-01
We investigate a Bose gas with finite-range interaction using a scheme to eliminate unphysical processes in the T-matrix approximation. In this way the corrected T-matrix becomes suitable to calculate properties below the critical temperature. For attractive interaction, an Evans-Rashid transition occurs between a quasi-ideal Bose gas and a Bardeen-Cooper-Schrieffer-like phase with a gap dispersion. The gap decreases with increasing density and vanishes at a critical density where the single-particle dispersion becomes linear for small momenta, indicating Bose-Einstein condensation. The investigation of the pressure shows, however, that the mentioned quantum phase transitions might be inaccessible due to a preceding first-order transition.
Kochereshko, Vladimir P.; Durnev, Mikhail V.; Besombes, Lucien; Mariette, Henri; Sapega, Victor F.; Askitopoulos, Alexis; Savenko, Ivan G.; Liew, Timothy C. H.; Shelykh, Ivan A.; Platonov, Alexey V.; Tsintzos, Simeon I.; Hatzopoulos, Z.; Savvidis, Pavlos G.; Kalevich, Vladimir K.; Afanasiev, Mikhail M.; Lukoshkin, Vladimir A.; Schneider, Christian; Amthor, Matthias; Metzger, Christian; Kamp, Martin; Hoefling, Sven; Lagoudakis, Pavlos; Kavokin, Alexey
2016-01-01
Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also been developed based on Bose-Einstein condensates of exciton-polaritons in semiconductor microcavities. These electrically neutral bosons coexist with charged electrons and holes. In the presence of magnetic fields, the charged particles are bound to their cyclotron orbits, while the neutral exciton-polaritons move freely. We demonstrate how magnetic fields affect dramatically the phase diagram of mixed Bose-Fermi systems, switching between fermionic lasing, incoherent emission and bosonic lasing regimes in planar and pillar microcavities with optical and electrical pumping. We collected and analyzed the data taken on pillar and planar microcavity structures at continuous wave and pulsed optical excitation as well as injecting electrons and holes electronically. Our results evidence the transition from a Bose gas to a Fermi liquid mediated by magnetic fields and light-matter coupling. PMID:26822483
NASA Astrophysics Data System (ADS)
Kochereshko, Vladimir P.; Durnev, Mikhail V.; Besombes, Lucien; Mariette, Henri; Sapega, Victor F.; Askitopoulos, Alexis; Savenko, Ivan G.; Liew, Timothy C. H.; Shelykh, Ivan A.; Platonov, Alexey V.; Tsintzos, Simeon I.; Hatzopoulos, Z.; Savvidis, Pavlos G.; Kalevich, Vladimir K.; Afanasiev, Mikhail M.; Lukoshkin, Vladimir A.; Schneider, Christian; Amthor, Matthias; Metzger, Christian; Kamp, Martin; Hoefling, Sven; Lagoudakis, Pavlos; Kavokin, Alexey
2016-01-01
Light amplification by stimulated emission of radiation, well-known for revolutionising photonic science, has been realised primarily in fermionic systems including widely applied diode lasers. The prerequisite for fermionic lasing is the inversion of electronic population, which governs the lasing threshold. More recently, bosonic lasers have also been developed based on Bose-Einstein condensates of exciton-polaritons in semiconductor microcavities. These electrically neutral bosons coexist with charged electrons and holes. In the presence of magnetic fields, the charged particles are bound to their cyclotron orbits, while the neutral exciton-polaritons move freely. We demonstrate how magnetic fields affect dramatically the phase diagram of mixed Bose-Fermi systems, switching between fermionic lasing, incoherent emission and bosonic lasing regimes in planar and pillar microcavities with optical and electrical pumping. We collected and analyzed the data taken on pillar and planar microcavity structures at continuous wave and pulsed optical excitation as well as injecting electrons and holes electronically. Our results evidence the transition from a Bose gas to a Fermi liquid mediated by magnetic fields and light-matter coupling.
Critical properties of weakly interacting Bose gases as modified by a harmonic confinement
NASA Astrophysics Data System (ADS)
Reyes-Ayala, I.; Poveda-Cuevas, F. J.; Seman, J. A.; Romero-Rochín, V.
2017-07-01
The critical properties of the phase transition from a normal gas to a Bose-Einstein condensate (superfluid) of a harmonically confined Bose gas are addressed with the knowledge of an equation of state of the underlying homogeneous Bose fluid. It is shown that while the presence of the confinement trap arrests the usual divergences of the isothermal compressibility and heat capacities, the critical behavior manifests itself now in the divergence of derivatives of the mentioned susceptibilities. This result is illustrated with a mean-field like model of an equation of state for the homogeneous particle density as a function of the chemical potential and temperature of the gas. The model assumes the form of an ideal Bose gas in the normal fluid while in the superfluid state a function is proposed such that, both, asymptotically reaches the Thomas-Fermi solution of a weakly interacting Bose gas at large densities and low temperatures and, at the transition, matches the critical properties of the ideal Bose gas. With this model we obtain the global thermodynamics of the harmonically confined gas, from which we analyze its critical properties. We discuss how these properties can be experimentally tested.
Jones, H A; Lakshminarayan, S; Becket, J M; Hughes, J M
1991-06-01
The aim was to measure cardiac output while rebreathing tidal volumes, by correction of soluble gas uptake for gaseous mixing. Simultaneous measurements of cardiac output by indocyanin green and freon 22 uptake during rebreathing were made. Mixing for a hypothetical gas of identical gaseous diffusivity to freon 22 was calculated by interpolation between concentrations of two insoluble gases, helium and sulphur hexafluoride. Mixing efficiency was estimated by the number of breaths for helium to become 99% equilibrated with lung gas (n99-He). Five anaesthetised dogs rebreathed at intervals with 300 ml of test gas. 63 comparisons of cardiac output using indocyanin green and freon 22 uptake (over breaths 7-13 using the mean mixed volume of distribution), gave a mean (95% confidence interval) underestimation of 0.345 (0.093-0.597) litre.min-1 (14%). Exclusion of 12 points in which n99-He was greater than 15 resulted in a mean underestimation of 0.052(-0.163-0.267) litre.min-1 (2%). Without correction for gaseous mixing, freon 22 uptake for these data overestimated blood flow by a mean of 1.31 litre.min-1 (overestimation = 2.7 over breaths 5-11). Use of the equilibrium volume of distribution resulted in an overestimation of blood flow relative to green dye of 1.2 litre.min-1 (breaths 5-11) and 0.76 litre.min-1 (breaths 7-13). Estimates of cardiac output by soluble gas uptake are optimal when correction is made for mixing of gas of identical diffusivity. The mean mixed gas volume gives the best correlation with the reference method, implying a selective distribution of blood flow to the better ventilated areas.
Thermalization and Bose-Einstein condensation of quantum light in bulk nonlinear media
NASA Astrophysics Data System (ADS)
Chiocchetta, A.; Larré, P.-É.; Carusotto, I.
2016-07-01
We study the thermalization and the Bose-Einstein condensation of a paraxial, spectrally narrow beam of quantum light propagating in a lossless bulk Kerr medium. The spatiotemporal evolution of the quantum optical field is ruled by a Heisenberg equation analogous to the quantum nonlinear Schrödinger equation of dilute atomic Bose gases. Correspondingly, in the weak-nonlinearity regime, the phase-space density evolves according to the Boltzmann equation. Expressions for the thermalization time and for the temperature and the chemical potential of the eventual Bose-Einstein distribution are found. After discussing experimental issues, we introduce an optical setup allowing the evaporative cooling of a guided beam of light towards Bose-Einstein condensation. This might serve as a novel source of coherent light.
Observation of Coupled Vortex Lattices in a Mass-Imbalance Bose and Fermi Superfluid Mixture.
Yao, Xing-Can; Chen, Hao-Ze; Wu, Yu-Ping; Liu, Xiang-Pei; Wang, Xiao-Qiong; Jiang, Xiao; Deng, Youjin; Chen, Yu-Ao; Pan, Jian-Wei
2016-09-30
Quantized vortices play an essential role in diverse superfluid phenomena. In a Bose-Fermi superfluid mixture, especially of two mass-imbalance species, such macroscopic quantum phenomena are particularly rich due to the interplay between the Bose and Fermi superfluidity. However, generating a Bose-Fermi two-species superfluid, producing coupled vortex lattices within, and further probing interspecies interaction effects remain challenging. Here, we experimentally realize a two-species superfluid with dilute gases of lithium-6 and potassium-41, having a mass ratio of about seven. By rotating the superfluid mixture, we simultaneously produce coupled vortex lattices of the two species and thus present a definitive visual evidence for the double superfluidity. Moreover, we report several unconventional behaviors, due to the Bose-Fermi interaction, on the formation and decay of two-species vortices.
Zhou, Xiaoji; Xu, Xu; Yin, Lan; Liu, W M; Chen, Xuzong
2010-07-19
We propose a new method of detecting quantum coherence of a Bose gas trapped in a one-dimensional optical lattice by measuring the light intensity from Raman scattering in cavity. After pump and displacement process, the intensity or amplitude of scattering light is different for different quantum states of a Bose gas, such as superfluid and Mott-Insulator states. This method can also be useful to detect quantum states of atoms with two components in an optical lattice.
Stupfel, M; Valleron, A J; Radford, E
1983-12-15
Male pathogen free CFE albino Sprague Dawley rats were exposed 8 h per day, 5 days per week, for three years to a 1/1000 dilution of automotive exhaust gas, containing 58 ppm carbon monoxide, 0.37% carbon dioxide, 23 ppm nitrogen oxides, 2 ppm aldehydes, less than 5 mg/l hydrocarbons and 8.5 micrograms/m3 lead. Lead, cadmium, iron, zinc, calcium and magnesium were measured by atomic absorption in the femurs and tibias of the rats which died during the experiment. A comparison with two control groups revealed that the only significant difference in the elements measured in the bones was a 500% increase in lead concentration. The calculations of the correlations between the percentages of the elements in bones, the ages and the body weights of the rats, as well as cluster analysis, did not show consistent variations of the water, calcium, magnesium concentrations nor of the other studied metals related to this increase in lead concentration. Moreover, longevity was the same in the 3 groups of rats, but the body weight was statistically smaller (4%) in the group exposed to the auto exhaust dilution.
Wu, Kuen-Yuh; Huang, Yu-Fang; Chen, Ming-Feng; Shih, Tung-Shen; Uang, Shi-Nian; Mao, I-Fang; Chen, Mei-Lien
2010-07-01
To develop a highly sensitive analytical method for very low acrylamide (AA) exposure and to conduct an occupational exposure assessment by the developed method. Seventy-five air samples from four plants were collected and analyzed using an isotope-dilution gas chromatography coupled with mass spectrometry (GC/MS). This isotope-dilution GC-MS method is sufficiently sensitive for assessing very low AA level as 4.37 ng m(-3), which is 10- to 7500-fold lower than the current analytical method. Field study showed that most airborne AA was gaseous rather than particulate. The personal exposure levels in workers ranged from 4.37 x 10(-3) microg m(-3) to 94.90 microg m(-3) with a mean of 12.08 microg m(-3). Fifty percent of personal 8-h time-weighted average (TWA) concentrations in the AA production plant exceeded the threshold limit value of 30 microg m(-3) set by American Conference of Governmental Industrial Hygienists. The field study indicated that 8-h TWA concentrations in workers varied by two orders of magnitude. The highly sensitive method can be used in future health risk assessment of AA exposure, such as those in fast-food restaurants.
Pickard, Stephanie; Becker, Irina; Merz, Karl-Heinz; Richling, Elke
2013-07-03
A stable isotope dilution analysis based on gas chromatography-mass spectrometry analysis (SIDA-GC-MS) was developed for the quantitative analysis of 12 alkylpyrazines found in commercially available coffee samples. These compounds contribute to coffee flavor. The accuracy of this method was tested by analyzing model mixtures of alkylpyrazines. Comparisons of alkylpyrazine-concentrations suggested that water as extraction solvent was superior to dichloromethane. The distribution patterns of alkylpyrazines in different roasted coffees were quite similar. The most abundant alkylpyrazine in each coffee sample was 2-methylpyrazine, followed by 2,6-dimethylpyrazine, 2,5-dimethylpyrazine, 2-ethylpyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-5-methylpyrazine, and 2,3,5-trimethylpyrazine, respectively. Among the alkylpyrazines tested, 2,3-dimethylpyrazine, 2-ethyl-3-methylpyrazine, 2-ethyl-3,6-dimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine revealed the lowest concentrations in roasted coffee. By the use of isotope dilution analysis, the total concentrations of alkylpyrazines in commercially available ground coffee ranged between 82.1 and 211.6 mg/kg, respectively. Decaffeinated coffee samples were found to contain lower amounts of alkylpyrazines than regular coffee samples by a factor of 0.3-0.7, which might be a result of the decaffeination procedure.
Bose gases, Bose–Einstein condensation, and the Bogoliubov approximation
Seiringer, Robert
2014-07-15
We review recent progress towards a rigorous understanding of the Bogoliubov approximation for bosonic quantum many-body systems. We focus, in particular, on the excitation spectrum of a Bose gas in the mean-field (Hartree) limit. A list of open problems will be discussed at the end.
Wudy, S A; Wachter, U A; Homoki, J; Teller, W M
1995-07-01
Using stable isotope dilution/gas chromatography-mass spectrometry (ID/GC-MS), a physicochemical method, we have profiled the plasma steroids 17 alpha-hydroxyprogesterone, 4-androstenedione, and testosterone in normal children of various age groups. Comparison of our values with those obtained by direct immunologic assays and those using an extraction or purification step showed that immunoassays in general overestimate steroid concentrations. This was especially true for plasma samples in the neonatal period and was most expressed for the concentrations of 17 alpha-hydroxyprogesterone. Our study demonstrated the applicability of ID/GC-MS to routine clinical steroid analysis. The application of ID/GC-MS is recommended whenever problems from matrix effects or cross-reactivity are likely to arise or suspicious results by immunoassays need to be rechecked.
NASA Astrophysics Data System (ADS)
Sandoval-Villalbazo, A.; Garcia-Perciante, A. L.; Sagaceta-Mejia, A. R.
2015-11-01
Kinetic theory is used to establish the explicit form of the particle flux associated to the Hall effect for the case of a dilute single component charged gas, using the Chapman-Enskog method and the BGK approximation for the collision Kernel. It is shown that when the system evolves towards mechanical equilibrium, the standard treatment using the concept of external force fails to describe the Hall effect. It is also shown that the use of a five-dimensional curved space-time in the description of the dynamics of the charged particle in the kinetic treatment (Kaluza's theory) formally solves the problem. The implications of this result are briefly discussed. The authors acknowledge support from CONACyT (Mexico) through grant CB2011/167563.
Talwar, Devki N.; Yang, Tzuen-Rong; Hsiung Lin, Hao; Chuan Feng, Zhe
2013-02-04
Vibrational spectra of gas-source molecular beam epitaxy grown dilute InN{sub x}As{sub 1-x}/InP (001) alloys are obtained using a Fourier-transform infrared (IR) spectroscopy. A triply degenerate N{sub As} local vibrational mode of T{sub d}-symmetry is observed near 438 cm{sup -1} corresponding to the In-N bond energy. The analysis of composition dependent infrared reflectivity spectra in InNAs has predicted a two-phonon-mode behavior. In In(Ga)-rich GaInNAs alloys the observed splitting of the N{sub As} local mode into a doublet for the N{sub As}-Ga{sub 1}(In{sub 1})In{sub 3}(Ga{sub 3}) pair-defect of C{sub 3v}-symmetry is consistent with our simulated results based on a sophisticated Green's function theory.
Xiao, Zuobing; Li, Jing; Niu, Yunwei; Liu, Qiang; Liu, Junhua
2017-03-28
Rose oil is much too expensive but very popular. It's well known that the flower oil's aroma profile hasn't been intensively investigated. In order to verify the aroma profile of rose oil, the synthetic blend of odorants was prepared and then compared with the original rose oil using electronic nose analysis (ENA) combined with quantitative descriptive analysis (QDA). The odorants from rose oils were screened out by Gas Chromatography-Olfactometry/aroma extract dilution analysis (GC-O/AEDA) combined with odour activity value (OAV). Both ENA and QDA indicated the recombination model derived from OAV and GC-O/AEDA closely resembled the original rose oil. The experiment results show that rose oxide, linalool, α-pinene, β-pinene, nonanal, heptanal citronellal, phenyl ethyl alcohol, benzyl alcohol, eugenol, methyl eugenol, β-citronellol, hexyl acetate, β-ionone, nerol, etc. are very important constituent to rose oil aroma profile.
Jönsson, S; Gustavsson, L; van Bavel, B
2007-09-14
A solid-phase microextraction (SPME) method using gas chromatography-electron-capture negative ionisation mass spectrometry (GC-ECNI-MS) and isotope dilution quantification for the analysis of nitroaromatic compounds in complex, water based samples has been optimised. For ionisation, ECNI was the most sensitive and selective method. SPME was compared to solid-phase extraction (SPE) and found to be more sensitive for these small volume samples. LODs were in the range 0.02-38ngL(-1) for SPME and 6-184ngL(-1) for SPE, respectively. The SPME method was applied on samples in the ngL(-1) level from artificial reed beds treated with sludge containing residues from explosives and pharmaceuticals.
Prendergast, Jocelyn L; Sniegoski, Lorna T; Welch, Michael J; Phinney, Karen W
2010-07-01
The definitive method (DM), now known as the reference measurement procedure (RMP), for the analysis of glucose in serum was originally published in 1982 by the National Institute of Standards and Technology (NIST). Over the years the method has been subject to a number of modifications to adapt to newer technologies and simplify sample preparation. We discuss here an adaptation of the method associated with serum glucose measurements using a modified isotope dilution gas chromatography/mass spectrometry (ID-GC/MS) method. NIST has used this modified method to certify the concentrations of glucose in SRM 965b, Glucose in Frozen Human Serum, and SRM 1950, Metabolites in Human Plasma. Comparison of results from the revised method with certified values for existing Standard Reference Materials (SRMs) demonstrated that these modifications have not affected the quality of the measurements, giving both good precision and accuracy, while reducing the sample preparation time by a day and a half.
England, G.C.; Watson, J.G.; Chow, J.C.; Zielinska, B.; Chang, M.C.O.; Loos, K.R.; Hidy. G.M.
2007-01-15
With the recent focus on fine particle matter (PM2.5), new, self- consistent data are needed to characterize emissions from combustion sources. Emissions data for gas-fired combustors are presented, using dilution sampling as the reference. The sampling and analysis of the collected particles in the presence of precursor gases, SO{sub 2}, nitrogen oxide, volatile organic compound, and NH{sub 3} is discussed; the results include data from eight gas fired units, including a dual- fuel institutional boiler and a diesel engine powered electricity generator. These data are compared with results in the literature for heavy-duty diesel vehicles and stationary sources using coal or wood as fuels. The results show that the gas-fired combustors have very low PM2.5 mass emission rates in the range of {approximately}10{sup -4} lb/million Btu (MMBTU) compared with the diesel backup generator with particle filter, with {approximately} 5 x 10{sup -3} lb/MMBTU. Even higher mass emission rates are found in coal-fired systems, with rates of {approximately} 0.07 lb/MMBTU for a bag-filter-controlled pilot unit burning eastern bituminous coal. The characterization of PM2.5 chemical composition from the gas-fired units indicates that much of the measured primary particle mass in PM2.5 samples is organic or elemental carbon and, to a much less extent, sulfate. Metal emissions are low compared with the diesel engines and the coal- or wood-fueled combustors. The metals found in the gas- fired combustor particles are low in concentration. The interpretation of the particulate carbon emissions is complicated by the fact that an approximately equal amount of particulate carbon is found on the particle collector and a backup filter. It is likely that measurement artifacts are positively biasing 'true' particulate carbon emissions results. 49 refs., 1 fig., 12 tabs.
Machrafi, Hatim; Cavadias, Simeon; Guibert, Philippe
2008-11-15
In order to contribute to the solution of controlling the autoignition in a homogeneous charge compression ignition (HCCI) engine, parameters linked to external gas recirculation (EGR) seem to be of particular interest. Experiments performed with EGR present some difficulties in interpreting results using only the diluting and thermal aspect of EGR. Lately, the chemical aspect of EGR is taken more into consideration, because this aspect causes a complex interaction with the dilution and thermal aspects of EGR. This paper studies the influence of EGR on the autoignition process and particularly the chemical aspect of EGR. The diluents present in EGR are simulated by N{sub 2} and CO{sub 2}, with dilution factors going from 0 to 46 vol%. For the chemically active species that could be present in EGR, the species CO, NO, and CH{sub 2}O are used. The initial concentration in the inlet mixture of CO and NO is varied between 0 and 170 ppm, while that of CH{sub 2}O alters between 0 and 1400 ppm. For the investigation of the effect of the chemical species on the autoignition, a fixed dilution factor of 23 vol% and a fixed EGR temperature of 70 C are maintained. The inlet temperature is held at 70 C, the equivalence ratios between 0.29 and 0.41, and the compression ratio at 10.2. The fuels used for the autoignition are n-heptane and PRF40. It appeared that CO, in the investigated domain, did not influence the ignition delays, while NO had two different effects. At concentrations up until 45 ppm, NO advanced the ignition delays for the PRF40 and at higher concentrations, the ignition delayed. The influence of NO on the autoignition of n-heptane seemed to be insignificant, probably due to the higher burn rate of n-heptane. CH{sub 2}O seemed to delay the ignition. The results suggested that especially the formation of OH radicals or their consumption by the chemical additives determines how the reactivity of the autoignition changed. (author)
Kaur, Navneet; Cabral, Jean-Louis; Morin, André; Waldron, Karen C
2011-01-14
Advanced smoke generation systems, such as the Borgwaldt RM20S(®) smoking machine used in combination with the BAT exposure chamber, allow for the generation, dilution and delivery of fresh cigarette smoke to cell or tissue cultures for in vitro cell culture analyses. Recently, our group confirmed that the Borgwaldt RM20S(®) is a reliable tool to generate and deliver repeatable and reproducible exposure concentrations of whole smoke to in vitro cultures. However, the relationship between dose and diluted smoke components found within the exposure chamber has not been characterized. The current study focused on the development of a headspace stir bar sorptive extraction (HSSE) method to chemically characterize some of the vapor phase components of cigarette smoke generated by the Borgwaldt RM20S(®) and collected within a cell culture exposure chamber. The method was based on passive sampling within the chamber by HSSE using a Twister™ stir bar. Following exposure, sorbed analytes were recovered using a thermal desorption unit and a cooled injection system coupled to gas chromatograph/mass spectrometry for identification and quantification. Using the HSSE method, sixteen compounds were identified. The desorption parameters were assessed using ten reference compounds and the following conditions led to the maximal response: desorption temperature of 200°C for 2 min with cryofocussing temperature of -75°C. During transfer of the stir bars to the thermal desorption system, significant losses of analytes were observed as a function of time; therefore, the exposure-to-desorption time interval was kept at the minimum of 10±0.5 min. Repeatability of the HSSE method was assessed by monitoring five reference compounds present in the vapor phase (10.1-12.9% RSD) and n-butyl acetate, the internal standard (18.5% RSD). The smoke dilution precision was found to be 17.2, 6.2 and 11.7% RSD for exposure concentrations of 1, 2 and 5% (v/v) cigarette vapor phase in air
Davis, William E; Li, Yongtao
2008-07-15
A new isotope dilution gas chromatography/chemical ionization/tandem mass spectrometric method was developed for the analysis of carcinogenic hydrazine in drinking water. The sample preparation was performed by using the optimized derivatization and multiple liquid-liquid extraction techniques. Using the direct aqueous-phase derivatization with acetone, hydrazine and isotopically labeled hydrazine-(15)N2 used as the surrogate standard formed acetone azine and acetone azine-(15)N2, respectively. These derivatives were then extracted with dichloromethane. Prior to analysis using methanol as the chemical ionization reagent gas, the extract was dried with anhydrous sodium sulfate, concentrated through evaporation, and then fortified with isotopically labeled N-nitrosodimethylamine-d6 used as the internal standard to quantify the extracted acetone azine-(15)N2. The extracted acetone azine was quantified against the extracted acetone azine-(15)N2. The isotope dilution standard calibration curve resulted in a linear regression correlation coefficient (R) of 0.999. The obtained method detection limit was 0.70 ng/L for hydrazine in reagent water samples, fortified at a concentration of 1.0 ng/L. For reagent water samples fortified at a concentration of 20.0 ng/L, the mean recoveries were 102% with a relative standard deviation of 13.7% for hydrazine and 106% with a relative standard deviation of 12.5% for hydrazine-(15)N2. Hydrazine at 0.5-2.6 ng/L was detected in 7 out of 13 chloraminated drinking water samples but was not detected in the rest of the chloraminated drinking water samples and the studied chlorinated drinking water sample.
Lopez-Avila, V.; Hirata, P.; Kraska, S.; Flanagan, M.; Taylor, J.H. Jr.; Hern, S.C.
1985-12-01
This paper describes an isotope dilution GC/MS technique for the analysis of low-parts-per-billion concentrations of atrazine, lindane, pentachlorophenol, and diazinon in water and soil. Known amounts of stable-labeled isotopes such as atrazine-d/sub 5/, lindane-d/sub 6/, pentachlorophenol-/sup 13/C/sub 6/, and diazinon-d/sub 10/ are spiked into each sample prior to extraction. Water samples are extracted with methylene chloride; soil samples are extracted with acetone/hexane. Analysis is performed by high-resolution GC/MS with the mass spectrometer operated in the selected ion monitoring mode. Accuracy greater than 86% and precision better than 8% were demonstrated by use of spiked samples. This technique has been used successfully in the analysis of over 300 water and 300 soil samples. Detection limits of 0.1-1.0 ppb were achieved for the test compounds by selected ion monitoring GC/MS. 8 references, 2 figures, 4 tables.
Real-time dynamics of single vortex lines and vortex dipoles in a Bose-Einstein condensate.
Freilich, D V; Bianchi, D M; Kaufman, A M; Langin, T K; Hall, D S
2010-09-03
Understanding the behavior of quantized vortices is essential to gaining insight into diverse superfluid phenomena, from critical-current densities in superconductors to quantum turbulence in superfluids. We observe the real-time dynamics of quantized vortices in trapped dilute-gas Bose-Einstein condensates by repeatedly imaging the vortex cores. The precession frequency of a single vortex is measured by explicitly observing its time dependence and is found to be in good agreement with theory. We further characterize the dynamics of vortex dipoles in two distinct configurations: (i) an asymmetric configuration, in which the vortex trajectories are dynamic and nontrivial, and (ii) a stable, symmetric configuration, in which the dipole is stationary.
NASA Astrophysics Data System (ADS)
Anderson, Brian P.; Neely, Tyler W.; Carlo Samson, E.; Wright, Ewan M.; Rooney, Sam J.; Bradley, Ashton S.; Davis, Matthew J.; Law, Kody J. H.; Carretero-Gonzalez, Ricardo; Kevrekidis, Panayotis G.
2011-05-01
We report the formation of persistent currents from the decay of turbulence in Bose- Einstein condensates (BECs). In our experiments, a BEC is pierced with a blue-detuned laser beam. By moving the trap center relative to the beam's position, vortices are stirred into the BEC, creating a quantum turbulent state. At finite temperatures, the turbulent state can decay to a persistent current about the blue-detuned laser beam that can last for up to 50 seconds; winding numbers up to 8 have been observed. Our experimental observations correspond well with numerical simulations of the non-equilibrium dynamics and calculations of vortex pinning by a laser beam. We interpret our results as evidence for an inverse energy cascade in dilute-gas BECs. This work is supported by the US National Science Foundation, the Army Research Office, and the New Zealand Foundation for Research, Science, and Technology.
Dilution Confusion: Conventions for Defining a Dilution
ERIC Educational Resources Information Center
Fishel, Laurence A.
2010-01-01
Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…
Dilution Confusion: Conventions for Defining a Dilution
ERIC Educational Resources Information Center
Fishel, Laurence A.
2010-01-01
Two conventions for preparing dilutions are used in clinical laboratories. The first convention defines an "a:b" dilution as "a" volumes of solution A plus "b" volumes of solution B. The second convention defines an "a:b" dilution as "a" volumes of solution A diluted into a final volume of "b". Use of the incorrect dilution convention could affect…
Bose-Einstein condensation on closed Robertson-Walker spacetimes
NASA Astrophysics Data System (ADS)
Trucks, M.
1998-12-01
In this letter we summarize our analysis of Bose-Einstein condensation on closed Robertson-Walker spacetimes. In a previous work we defined an adiabatic KMS state on the Weyl-algebra of the free massive Klein-Gordon field [M. Trucks, M. Keyl, Phys. Lett. B 399 (1997) 223, M. Trucks, Commun. Math. Phys. 197 (1998) 387]. This state describes a free Bose gas on Robertson-Walker spacetimes. We use this state to analyze the possibility of Bose-Einstein condensation on closed Robertson-Walker spacetimes. We take into account the effects due to the finiteness of the spatial volume and show that they are not relevant in the early universe. Furthermore we show that a critical radius can be defined. The condensate disappears above the critical radius.
Bose-Einstein condensation of photons in an optical microcavity.
Klaers, Jan; Schmitt, Julian; Vewinger, Frank; Weitz, Martin
2010-11-25
Bose-Einstein condensation (BEC)-the macroscopic ground-state accumulation of particles with integer spin (bosons) at low temperature and high density-has been observed in several physical systems, including cold atomic gases and solid-state quasiparticles. However, the most omnipresent Bose gas, blackbody radiation (radiation in thermal equilibrium with the cavity walls) does not show this phase transition. In such systems photons have a vanishing chemical potential, meaning that their number is not conserved when the temperature of the photon gas is varied; at low temperatures, photons disappear in the cavity walls instead of occupying the cavity ground state. Theoretical works have considered thermalization processes that conserve photon number (a prerequisite for BEC), involving Compton scattering with a gas of thermal electrons or photon-photon scattering in a nonlinear resonator configuration. Number-conserving thermalization was experimentally observed for a two-dimensional photon gas in a dye-filled optical microcavity, which acts as a 'white-wall' box. Here we report the observation of a Bose-Einstein condensate of photons in this system. The cavity mirrors provide both a confining potential and a non-vanishing effective photon mass, making the system formally equivalent to a two-dimensional gas of trapped, massive bosons. The photons thermalize to the temperature of the dye solution (room temperature) by multiple scattering with the dye molecules. Upon increasing the photon density, we observe the following BEC signatures: the photon energies have a Bose-Einstein distribution with a massively populated ground-state mode on top of a broad thermal wing; the phase transition occurs at the expected photon density and exhibits the predicted dependence on cavity geometry; and the ground-state mode emerges even for a spatially displaced pump spot. The prospects of the observed effects include studies of extremely weakly interacting low-dimensional Bose gases and
Rodríguez-Cea, Andrés; Rodríguez-González, Pablo; Font Cardona, Nuria; Aranda Mares, José Luís; Ballester Nebot, Salomé; García Alonso, J Ignacio
2015-12-18
The current EU legislation lays down the Environmental Quality Standards (EQS) of 45 priority substances in surface water bodies. In particular, the concentration of tributyltin (TBT) must not exceed 0.2ngL(-1) and analytical methodologies with a Limit of Quantification (LOQ) equal or below 0.06ngL(-1) are urged to be developed. This work presents a procedure for the determination of ultratrace levels of TBT in water samples by Isotope Dilution and GC-MS/MS operating in Selected Reaction Monitoring (SRM) mode which meets current EU requirements. The method requires the monitorization of five consecutive transitions (287>175 to 291>179) for the sensitive and selective detection of TBT. The measured isotopic distribution of TBT fragment ions was in agreement with the theoretical values computed by a polynomial expansion algorithm. The combined use of Tandem Mass Spectrometry, a sample volume of 250mL, the preconcentration of 1mL of organic phase to 30μL and an injection volume of 25μL by Programmed Temperature Vaporization provided a LOQ of 0.0426ngL(-1) for TBT (calculated as ten times the standard deviation of nine independent blanks). The recovery for TBT calculated in Milli-Q water at the EQS level was 106.3±4%. A similar procedure was also developed for the quantification of dibutyltin (DBT) and monobutyltin (MBT) in water samples showing satisfactory results. The method was finally implemented in a routine testing laboratory to demonstrate its applicability to real samples obtaining quantitative recoveries for TBT at the EQS level in mineral water, river water and seawater. Copyright © 2015 Elsevier B.V. All rights reserved.
Niebler, Johannes; Buettner, Andrea
2015-01-01
Frankincense has been known, traded and used throughout the ages for its exceptional aroma properties, and is still commonly used in both secular and religious settings to convey a pleasant odor. Surprisingly, the odoriferous principle(s) underlying its unique odor profile have never been published. In this study, resin samples of Boswellia sacra Flueck. from both Somalia and Oman were investigated by aroma extract dilution analysis. In a comprehensive, odor-activity guided approach both chemo-analytical and human-sensory parameters were used to identify odor active constituents of the volatile fraction of B. sacra. Among the key odorants found were α-pinene, β-myrcene, linalool, p-cresol and two unidentified sesquiterpenoids. Overall, a total of 23 odorants were detected and analyzed by gas chromatography-olfactometry and heart-cut two-dimensional gas chromatography-mass spectrometry/olfactometry. The majority of the identified odorant compounds were oxygenated monoterpenes, along with some relevant mono- and sesquiterpenes and only one diterpenoid substance. Several of these compounds were reported here for the first time as odorous constituents in B. sacra. Identifying bioactive compounds might support a better understanding with regard to the potential benefits of frankincense, for example in aromatherapy or ecclesial settings.
NASA Technical Reports Server (NTRS)
Bandy, Alan R.; Thornton, Donald C.; Driedger, Arthur R., III
1993-01-01
A gas chromatograph/mass spectrometer is described for determining atmospheric sulfur dioxide, carbon disulfide, dimethyl sulfide, and carbonyl sulfide from aircraft and ship platforms. Isotopically labelled variants of each analyte were used as internal standards to achieve high precision. The lower limit of detection for each species for an integration time of 3 min was 1 pptv for sulfur dioxide and dimethyl sulfide and 0.2 pptv for carbon disulfide and carbonyl sulfide. All four species were simultaneously determined with a sample frequency of one sample per 6 min or greater. When only one or two species were determined, a frequency of one sample per 4 min was achieved. Because a calibration is included in each sample, no separate calibration sequence was needed. Instrument warmup was only a few minutes. The instrument was very robust in field deployments, requiring little maintenance.
NASA Technical Reports Server (NTRS)
Bandy, Alan R.; Thornton, Donald C.; Driedger, Arthur R., III
1993-01-01
A gas chromatograph/mass spectrometer is described for determining atmospheric sulfur dioxide, carbon disulfide, dimethyl sulfide, and carbonyl sulfide from aircraft and ship platforms. Isotopically labelled variants of each analyte were used as internal standards to achieve high precision. The lower limit of detection for each species for an integration time of 3 min was 1 pptv for sulfur dioxide and dimethyl sulfide and 0.2 pptv for carbon disulfide and carbonyl sulfide. All four species were simultaneously determined with a sample frequency of one sample per 6 min or greater. When only one or two species were determined, a frequency of one sample per 4 min was achieved. Because a calibration is included in each sample, no separate calibration sequence was needed. Instrument warmup was only a few minutes. The instrument was very robust in field deployments, requiring little maintenance.
Campo, Laura; Fustinoni, Silvia; Bertazzi, Pieralberto
2011-08-01
Polycyclic aromatic hydrocarbons (PAHs) are pollutants found in living and working environments. The aim of this study was to develop a solid-phase microextraction (SPME) gas chromatography (GC)-isotope dilution mass spectrometry method for the quantification of 10 four- to six-ring PAHs in urine samples. Seven of the selected PAHs have been classified as carcinogenic. Under the final conditions, analytes were sampled with a 100-μm polydimethylsiloxane SPME fibre for 60 min at 80 °C and desorbed in the injection port of the GC at 270 °C. Fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, indeno[1,2,3-cd]pyrene and benzo[ghi]perylene were separated using a highly arylene-modified phase capillary column and quantified by MS using eight deuterated PAHs as surrogate internal standards. Limits of quantification (LOQ) were in the 0.5- to 2.2-ng/L range. Validation showed linear dynamic ranges up to 340 ng/L, inter- and intra-run precisions <20%, and accuracies within 20% of spiked concentrations. Matrix effect evaluation and the use of control charts to monitor process performances showed that the isotope dilution approach allowed for the control of bias sources. Urinary PAHs were above or equal to LOQ, depending on different compounds, in 58-100% (min-max), 40-100% and 5-39% of samples from coke oven workers (n = 12), asphalt workers (n = 10) and individuals not occupationally exposed to PAHs (n = 18), respectively. Chrysene was the most abundant PAH determined with median levels of 62.6, 6.9 and <0.6 ng/L, respectively. These results show that the method is suitable for quantifying carcinogenic PAHs in specimens from individuals with different levels of PAH exposure.
Using custom potentials to access quantum Hall states in rotating Bose gases
NASA Astrophysics Data System (ADS)
Morris, Alexis G.; Feder, David L.
2007-03-01
The exact ground states of zero-temperature rotating Bose gases confined in quasi-two-dimensional harmonic traps are studied numerically, for small numbers of alkali atoms. As the rotation frequency increases, the interacting Bose gas undergoes a series of transitions from one quantum Hall state to another. We have investigated the possibility of facilitating access to specific quantum Hall states through the addition of customized potentials to the existing trapping potential. For the right choice of potential, we show that creation of predetermined quantum Hall states in rotating Bose gases should be possible using current experimental setups. (Research supported by NSERC, iCORE and CFI)
Landau damping in a dipolar Bose-Fermi mixture in the Bose-Einstein condensation (BEC) limit
NASA Astrophysics Data System (ADS)
Moniri, S. M.; Yavari, H.; Darsheshdar, E.
2016-12-01
By using a mean-field approximation which describes the coupled oscillations of condensate and noncondensate atoms in the collisionless regime, Landau damping in a dilute dipolar Bose-Fermi mixture in the BEC limit where Fermi superfluid is treated as tightly bounded molecules, is investigated. In the case of a uniform quasi-two-dimensional (2D) case, the results for the Landau damping due to the Bose-Fermi interaction are obtained at low and high temperatures. It is shown that at low temperatures, the Landau damping rate is exponentially suppressed. By increasing the strength of dipolar interaction, and the energy of boson quasiparticles, Landau damping is suppressed over a broader temperature range.
Huang, Wenlin; Blount, Benjamin C; Watson, Clifford H; Watson, Christina; Chambers, David M
2017-02-15
To accurately measure menthol levels in human urine, we developed a method using gas chromatography/electron ionization mass spectrometry with menthol-d4 stable isotope internal standardization. We used solid phase microextraction (SPME) headspace sampling for collection, preconcentration and automation. Conjugated forms of menthol were released using β-glucuronidase/sulfatase to allow for measuring total menthol. Additionally, we processed the specimens without using β-glucuronidase/sulfatase to quantify the levels of unconjugated (free) menthol in urine. This method was developed to verify mentholated cigarette smoking status to study the influence of menthol on smoking behaviour and exposure. This objective was accomplished with this method, which has no carryover or memory from the SPME fiber assembly, a method detection limit of 0.0017μg/mL, a broad linear range of 0.002-0.5μg/mL for free menthol and 0.01-10μg/mL for total menthol, a 7.6% precision and 88.5% accuracy, and an analysis runtime of 17min. We applied this method in analysis of urine specimens collected from cigarette smokers who smoke either mentholated or non-mentholated cigarettes. Among these smokers, the average total urinary menthol levels was three-fold higher (p<0.001) among mentholated cigarette smokers compared with non-mentholated cigarette smokers.
Roggendorf, W; Thron, N L; Ast, D; Köhler, P R
1981-01-01
Regarding the potential impact of traffic-born air pollutants on public health, attention during the last years has been increasingly focused on the possible effects in high-risk groups of the population. In order to evaluated this point further, the combined influence of both, chronic arterial hypertension and long-time exhaust gas exposure on the CNS has been studied. Both, normotensive Wistar) and spontaneously hypertensive rats (SHR) of either sex were exposed 5 X 8 hours per week for up to 18 months to atmospheres polluted by the emissions of an idling Otto engine with CO concentrations held constant at about 0,90 and 250 ppm, respectively. Biochemical data, body weight, and blood pressure were checked regularly. Characteristic histomorphological findings in the non-exposed SHR brains were hyalinosis and hyperplasia of intracerebral arterioles and -- in some cases -- small focal hemorrhages and infarcts. In the exposed SHR brains, large infarcts of the hemisphere and in the basal ganglia were found, which possibly corresponds to the increase of the mortality rate in SHR. We assume that the increase hematocrit plays an important role in the disturbance of microcirculation of the CNS.
Havenith, George; Zhang, Ping; Hatcher, Kent; Daanen, Hein
2010-04-01
Clothing microclimate ventilation is an important parameter in climatic stress and in contaminated environments. The two main methods for its determination (Crockford et al. (CR) 1972 and Lotens and Havenith (LH) 1988) were, after further development, compared in terms of reproducibility, validity and usability. Both methods were shown to have a good sensitivity and reproducibility (with average coefficients of variation 1.5-2.3% for the method alone and up to 7% for method and clothing/movement effects combined). They produced values very close to calibration values in forced ventilation tests (r = 0.988). Weak points for the CR method were the limits in the time constant of the measurement apparatus, causing an upper limit to the ventilation that can be reliably measured (around 800 l/min) and the method of measuring clothing microclimate volume. The original 'vacuum oversuit' (CR) method was cumbersome and prone to large errors. Alternative methods of measuring clothing microclimate volume (whole body scanner or manual circumference measurements) were shown to produce good results. For the LH method, the distribution of the tracer gas over the whole skin surface became a problem factor at very high ventilations (above 1000 l/min). As all methods use tracer gases (O(2), Ar, CO(2), SF(6)) with diffusivities smaller than that of water vapour, this potentially creates a problem in the calculation of vapour resistance from the ventilation values in the region where the emphasis of vapour transfer moves from diffusion to convection. In most real-life situations, where body and air movement are present, a correction is not however required because the error remains below 10%. STATEMENT OF RELEVANCE: Clothing ventilation indicates heat loss potential as well as risk of pollutants entering the clothing. Two main methods for its determination are compared and validated, identifying a number of issues. An in-depth analysis is given of the advantages and disadvantages of
Haag, G.L.
1983-09-01
The removal of trace components from gas streams via irreversible gas-solid reactions in an area of interest to the chemical engineering profession. This research effort addresses the use of fixed beds of Ba(OH)/sub 2/ hydrate flakes for the removal of an acid gas, CO/sub 2/, from air that contains approx. 330 ppM/sub v/ CO/sub 2/. Areas of investigation encompassed: (1) an extensive literature review of Ba(OH)/sub 2/ hydrate chemistry, (2) microscale studies on 0.150-g samples to develop a better understanding of the reaction, (3) process studies at the macroscale level with 10.2-cm-ID fixed-bed reactors, and (4) the development of a model for predicting fixed-bed performance. Experimental studies indicated fixed beds of commercial Ba(OH)/sub 2/.8H/sub 2/O flakes at ambient temperatures to be capable of high CO/sub 2/-removal efficiencies (effluent concentrations <100 ppB), high reactant utilization (>99%), and an acceptable pressure drop (1.8 kPa/m at a superficial gas velocity of 13 cm/s). Ba(OH)/sub 2/.8H/sub 2/O was determined to be more reactive toward CO/sub 2/ than either Ba(OH)/sub 2/.3H/sub 2/O or Ba(OH)/sub 2/.1H/sub 2/O. A key variable in the development of this fixed-bed process was relative humidity. Operation at conditions with effluent relative humidities >60% resulted in significant recrystallization and restructuring of the flake and subsequent pressure-drop problems.
Two characteristic temperatures for a Bose-Einstein condensate of a finite number of particles
Idziaszek, Z.; Rzazewski, K.
2003-09-01
We consider two characteristic temperatures for a Bose-Einstein condensate, which are related to certain properties of the condensate statistics. We calculate them for an ideal gas confined in power-law traps and show that they approach the critical temperature in the limit of large number of particles. The considered characteristic temperatures can be useful in the studies of Bose-Einstein condensates of a finite number of atoms indicating the point of a phase transition.
The Condensate Wave Function of a Trapped Atomic Gas
Dalfovo, F.; Pitaevskii, L.; Stringari, S.
1996-01-01
We discuss various properties of the ground state of a Bose-condensed dilute gas confined by an external potential. We devote particular attention to the role played by the interaction in determining the kinetic energy of the system and the aspect ratio of the velocity distribution. The structure of the wave function near the classical turning point is discussed and the drawback of the Thomas-Fermi approximation is explicitly pointed out. We consider also states with quantized vorticity and calculate the critical angular velocity for the production of vortices. The presence of vortex states is found to increases the stability of the condensate in the case of attractive interactions. PMID:27805106
Wu, Pinggu; Zhang, Liqun; Yang, Dajin; Zhang, Jing; Hu, Zhengyan; Wang, Liyuan; Ma, Bingjie
2016-03-01
By the combination of solid-phase extraction as well as isotope dilution gas chromatography with mass spectrometry, a sensitive and reliable method for the determination of endocrine-disrupting chemicals including bisphenol A, 4-octylphenol, and 4-nonylphenol in vegetable oils was established. The application of a silica/N-(n-propyl)ethylenediamine mixed solid-phase extraction cartridge achieved relatively low matrix effects for bisphenol A, 4-octylphenol, and 4-nonylphenol in vegetable oils. Experiments were designed to evaluate the effects of derivatization, and the extraction parameters were optimized. The estimated limits of detection and quantification for bisphenol A, 4-octylphenol, and 4-nonylphenol were 0.83 and 2.5 μg/kg, respectively. In a spiked experiment in vegetable oils, the recovery of the added bisphenol A was 97.5-110.3%, recovery of the added 4-octylphenol was 64.4-87.4%, and that of 4-nonylphenol was 68.2-89.3%. This sensitive method was then applied to real vegetable oil samples from Zhejiang Province of China, and none of the target compounds were detected.
Maraval, Isabelle; Sen, Kemal; Agrebi, Abdelhamid; Menut, Chantal; Morere, Alain; Boulanger, Renaud; Gay, Frédéric; Mestres, Christian; Gunata, Ziya
2010-08-24
A new and convenient synthesis of 2-acetyl-1-pyrroline (2AP), a potent flavor compound in rice, and its ring-deuterated analog, 2-acetyl-1-d(2)-pyrroline (2AP-d(2)), was reported. A stable isotope dilution assay (SIDA), involving headspace solid-phase microextraction (HS-SPME) combined with gas chromatography-positive chemical ionization-ion trap-tandem mass spectrometry (GC-PCI-IT-MS-MS), was developed for 2AP quantification. A divinylbenzene/carboxen/polydimethylsiloxane (DVB/CAR/PDMS) fiber was used for HS-SPME procedure and parameters affecting analytes recovery, such as extraction time and temperature, pH and salt, were studied. The repeatability of the method (n=10) expressed as relative standard deviation (RSD) was 11.6%. A good linearity was observed from 5.9 to 779 ng of 2AP (r(2)=0.9989). Limits of detection (LOD) and quantification (LOQ) for 2AP were 0.1 and 0.4 ng g(-1) of rice, respectively. The recovery of spiked 2AP from rice matrix was almost complete. The developed method was applied to the quantification of 2AP in aerial parts and grains of scented and non-scented rice cultivars.
Cares-Pacheco, M G; Vaca-Medina, G; Calvet, R; Espitalier, F; Letourneau, J-J; Rouilly, A; Rodier, E
2014-11-20
Nowadays, it is well known that surface interactions play a preponderant role in mechanical operations, which are fundamental in pharmaceutical processing and formulation. Nevertheless, it is difficult to correlate surface behaviour in processes to physical properties measurement. Indeed, most pharmaceutical solids have multiple surface energies because of varying forms, crystal faces and impurities contents or physical defects, among others. In this paper, D-mannitol polymorphs (α, β and δ) were studied through different characterization techniques highlighting bulk and surface behaviour differences. Due to the low adsorption behaviour of β and δ polymorphs, special emphasis has been paid to surface energy analysis by inverse gas chromatography, IGC. Surface energy behaviour has been studied in Henry's domain showing that, for some organic solids, the classical IGC infinite dilution zone is never reached. IGC studies highlighted, without precedent in literature, dispersive surface energy differences between α and β mannitol, with a most energetically active α form with a γ(s)(d) of 74.9 mJ·m⁻². Surface heterogeneity studies showed a highly heterogeneous α mannitol with a more homogeneous β (40.0 mJ·m⁻²) and δ mannitol (40.3 mJ·m⁻²). Moreover, these last two forms behaved similarly considering surface energy at different probe concentrations.
Eljack, Mahmoud D; Wilson, Rachael E; Hussam, Abul; Khan, Shahamat U
2015-02-27
Fulvic acid (FA), the most important water soluble fraction of humic substances in nature, is known to form aggregate pseudophase and complexes with organic and inorganic species. Here, we report a novel equilibrium headspace gas chromatography (eHSGC) and a two-step reaction model to measure n-alkylbenzene-FA association constant (K11) and n-alkylbenzene-pseudophase FAn association constant (Kn1) without solute concentration and response factor. The K11 and Kn1 values were 2-3 orders of magnitude higher than those for sodium dodecylsulfate. Changes in peak area were used to calculate the critical FA-aggregation concentration (cfc), mole fraction based partition coefficients (Kx), activity coefficients of solute inside the aggregate pseudophase (γm(∞)), and transfer free energies of alkyl CH2 at infinite dilution. The cfc was found to be 10±0.5μM. The Kx values are of the order of 10(7) in the FA-aggregate pseudophase. The data shows that benzene has the lowest (0.0002) and n-butylbenzene has the highest (0.01) γm(∞) values, which are seven orders of magnitude smaller than γw(∞) in water. The transfer free energy of association of a CH2 group, -155cal/mol, compared to that of benzene, -9722cal/mol, indicates that the FA-aggregate pseudophase is more polarizable benzene-like and less n-alkane aliphatic-like.
Lin, Ying; Chen, Jia; Yan, Long; Guo, Lei; Wu, Bidong; Li, Chunzheng; Feng, Jianlin; Liu, Qin; Xie, Jianwei
2014-08-01
A simple and sensitive method has been developed and validated for determining ethyl methylphosphonic acid (EMPA), isopropyl methylphosphonic acid (IMPA), isobutyl methylphosphonic acid (iBuMPA), and pinacolyl methylphosphonic acid (PMPA) in human urine using gas chromatography-tandem mass spectrometry (GC-MS/MS) coupled with solid phase derivatization (SPD). These four alkyl methylphosphonic acids (AMPAs) are specific hydrolysis products and biomarkers of exposure to classic organophosphorus (OP) nerve agents VX, sarin, RVX, and soman. The AMPAs in urine samples were directly derivatized with pentafluorobenzyl bromide on a solid support and then extracted by liquid-liquid extraction. The analytes were quantified with isotope-dilution by negative chemical ionization (NCI) GC-MS/MS in a selected reaction monitoring (SRM) mode. This method is highly sensitive, with the limits of detection of 0.02 ng/mL for each compound in a 0.2 mL sample of human urine, and an excellent linearity from 0.1 to 50 ng/mL. It is proven to be very suitable for the qualitative and quantitative analyses of degradation markers of OP nerve agents in biomedical samples.
Woudneh, Million B; Sekela, Mark; Tuominen, Taina; Gledhill, Melissa
2006-11-10
In this work, an isotope dilution method for determination of selected acidic herbicides by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) was developed for surface water samples. Average percent recoveries of native analytes were observed to be between 70.8 and 93.5% and average recoveries of labeled quantification standards [(13)C(6)]2,4-D and [(13)C(6)]2,4,5-T were 85.5 and 101%, respectively. Using this method, detection limits of 0.05 ng/L for dicamba, MCPA, MCPP, and triclopyr, and 0.5 ng/L for 2,4-D were routinely achieved. The method was applied to measuring the concentration of these analytes in surface water samples collected from five sampling locations in the Lower Fraser Valley region of British Columbia, Canada. All of the herbicides monitored were detected at varying levels in the surface water samples collected. The highest concentrations detected for each analyte were 345 ng/L for 2,4-D, 317 ng/L for MCPA, 271 ng/L for MCPP, 15.7 ng/L for dicamba, and 2.18 ng/L for triclopyr. Average detection frequencies of the herbicides were 95% for MCPA, 80% for MCPP, 70% for dicamba, 65% for 2,4-D, and 46% for triclopyr. Seasonal variations of herbicide levels are also discussed.
Thurman, E.M.; Zimmerman, L.R.; Aga, D.S.; Gilliom, R.J.
2001-01-01
Gas chromatography with isotope dilution mass spectrometry (GC-MS) and enzyme-linked immunosorbent assay (ELISA) were used in regional National Water Quality Assessment studies of the herbicides, 2,4-D and dicamba, in river water across the United States. The GC-MS method involved solid-phase extraction, derivatized with deutemted 2,4-D, and analysis by selected ion monitoring. The ELISA method was applied after preconcentration with solid-phase extraction. The ELISA method was unreliable because of interference from humic substances that were also isolated by solid-phase extraction. Therefore, GC-MS was used to analyzed 80 samples from river water from 14 basins. The frequency of detection of dicamba (28%) was higher than that for 2,4-D (16%). Concentrations were higher for dicamba than for 2,4-D, ranging from less than the detection limit (<0.05 ??g/L) to 3.77 ??g/L, in spite of 5 times more annual use of 2,4-D as compared to dicamba. These results suggest that 2,4-D degrades more rapidly in the environment than dicamba.
Campo, Laura; Mercadante, Rosa; Rossella, Federica; Fustinoni, Silvia
2009-01-12
Polycyclic aromatic hydrocarbons (PAHs) are common environmental pollutants in both living and working environments. The aim of this study was the development of a headspace solid-phase microextraction gas chromatography-isotope dilution mass spectrometry (HS-SPME/GC-IDMS) method for the simultaneous quantification of 13 PAHs in urine samples. Different parameters affecting PAHs extraction by HS-SPME were considered and optimized: type/thickness of fiber coatings, extraction temperature/time, desorption temperature/time, ionic strength and sample agitation. The stability of spiked PAHs solutions and of real urine samples stored up to 90 days in containers of different materials was evaluated. In the optimized method, analytes were absorbed for 60min at 80 degrees C in the sample headspace with a 100mum polydimethylsiloxane fiber. The method is very specific, with linear range from the limit of quantification to 8.67 x 10(3)ngL(-1), a within-run precision of <20% and a between-run precision of <20% for 2-, 3- and 4-ring compounds and of <30% for 5-ring compounds, trueness within 20% of the spiked concentration, and limit of quantification in the 2.28-2.28 x 10(1)ngL(-1) range. An application of the proposed method using 15 urine samples from subjects exposed to PAHs at different environmental levels is shown.
D'Autry, Ward; Zheng, Chao; Bugalama, John; Wolfs, Kris; Hoogmartens, Jos; Adams, Erwin; Wang, Bochu; Van Schepdael, Ann
2011-07-15
Residual solvents are volatile organic compounds which can be present in pharmaceutical substances. A generic static headspace-gas chromatography analysis method for the identification and control of residual solvents is described in the European Pharmacopoeia. Although this method is proved to be suitable for the majority of samples and residual solvents, the method may lack sensitivity for high boiling point residual solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide and benzyl alcohol. In this study, liquid paraffin was investigated as new dilution medium for the analysis of these residual solvents. The headspace-gas chromatography method was developed and optimized taking the official Pharmacopoeia method as a starting point. The optimized method was validated according to ICH criteria. It was found that the detection limits were below 1μg/vial for each compound, indicating a drastically increased sensitivity compared to the Pharmacopoeia method, which failed to detect the compounds at their respective limit concentrations. Linearity was evaluated based on the R(2) values, which were above 0.997 for all compounds, and inspection of residual plots. Instrument and method precision were examined by calculating the relative standard deviations (RSD) of repeated analyses within the linearity and accuracy experiments, respectively. It was found that all RSD values were below 10%. Accuracy was checked by a recovery experiment at three different levels. Mean recovery values were all in the range 95-105%. Finally, the optimized method was applied to residual DMSO analysis in four different Kollicoat(®) sample batches.
Energies and damping rates of elementary excitations in spin-1 Bose-Einstein-condensed gases
NASA Astrophysics Data System (ADS)
Szirmai, Gergely; Szépfalusy, Péter; Kis-Szabó, Krisztián
2003-08-01
The finite temperature Green’s function technique is used to calculate the energies and damping rates of the elementary excitations of homogeneous, dilute, spin-1 Bose gases below the Bose-Einstein condensation temperature in both the density and spin channels. For this purpose a self-consistent dynamical Hartree-Fock model is formulated, which takes into account the direct and exchange processes on equal footing by summing up certain classes of Feynman diagrams. The model is shown to satisfy the Goldstone theorem and to exhibit the hybridization of one-particle and collective excitations correctly. The results are applied to gases of 23Na and 87Rb atoms.
Brownian motion of solitons in a Bose-Einstein condensate.
Aycock, Lauren M; Hurst, Hilary M; Efimkin, Dmitry K; Genkina, Dina; Lu, Hsin-I; Galitski, Victor M; Spielman, I B
2017-03-07
We observed and controlled the Brownian motion of solitons. We launched solitonic excitations in highly elongated [Formula: see text] Bose-Einstein condensates (BECs) and showed that a dilute background of impurity atoms in a different internal state dramatically affects the soliton. With no impurities and in one dimension (1D), these solitons would have an infinite lifetime, a consequence of integrability. In our experiment, the added impurities scatter off the much larger soliton, contributing to its Brownian motion and decreasing its lifetime. We describe the soliton's diffusive behavior using a quasi-1D scattering theory of impurity atoms interacting with a soliton, giving diffusion coefficients consistent with experiment.
Bose-Einstein condensation in binary mixture of Bose gases
Tran Huu Phat; Le Viet Hoa; Nguyen Tuan Anh Nguyen Van Long
2009-10-15
The Bose-Einstein condensation (BEC) in a binary mixture of Bose gases is studied by means of the Cornwall-Jackiw-Tomboulis (CJT) effective action approach. The equations of state (EoS) and various scenarios of phase transitions of the system are considered in detail, in particular, the numerical computations are carried out for symmetry restoration (SR), symmetry nonrestoration (SNR) and inverse symmetry breaking (ISB) for getting an insight into their physical nature. It is shown that due to the cross interaction between distinct components of mixture there occur two interesting phenomena: the high temperature BEC and the inverse BEC, which could be tested in experiments.
Diffusion dynamics in the disordered Bose Hubbard model
NASA Astrophysics Data System (ADS)
Wadleigh, Laura; Russ, Philip; Demarco, Brian
2016-05-01
We explore the dynamics of diffusion for out-of-equilibrium superfluid, Mott insulator, and Bose glass states using an atomic realization of the disordered Bose Hubbard (DBH) model. Dynamics in strongly correlated systems, especially far from equilibrium, are not well understood. The introduction of disorder further complicates these systems. We realize the DBH model--which has been central to our understanding of quantum phase transitions in disordered systems--using ultracold Rubidium-87 atoms trapped in a cubic disordered optical lattice. By tightly focusing a beam into the center of the gas, we create a hole in the atomic density profile. We achieve Mott insulator, superfluid, or Bose glass states by varying the interaction and disorder strength, and measure the time evolution of the density profile after removing the central barrier. This allows us to infer diffusion rates from the velocities at the edge of the hole and to look for signatures of superfluid puddles in the Bose glass state. We acknowledge funding from NSF Grant PHY 15-05468, NSF Grant DGE-1144245, and ARO Grant W911NF-12-1-0462.
D-dimensional Bose gases and the Lambert W function
NASA Astrophysics Data System (ADS)
Tanguay, J.; Gil, M.; Jeffrey, D. J.; Valluri, S. R.
2010-12-01
The applications of the Lambert W function (also known as the W function) to D-dimensional Bose gases are presented. We introduce two sets of families of logarithmic transcendental equations that occur frequently in thermodynamics and statistical mechanics and present their solution in terms of the W function. The low temperature T behavior of free ideal Bose gases is considered in three and four dimensions. It is shown that near condensation in four dimensions, the chemical potential μ and pressure P can be expressed in terms of T through the W function. The low T behavior of one- and two-dimensional ideal Bose gases in a harmonic trap is studied. In 1D, the W function is used to express the condensate temperature, T_C, in terms of the number of particles N; in 2D, it is used to express μ in terms of T. In the low T limit of the 1D hard-core and the 3D Bose gas, T can be expressed in terms of P and μ through the W function. Our analysis allows for the possibility to consider μ, T, and P as complex variables. The importance of the underlying logarithmic structure in ideal quantum gases is seen in the polylogarithmic and W function expressions relating thermodynamic variables such as μ, T, and P.
Thermodynamic equivalence of two-dimensional imperfect attractive Fermi and repulsive Bose gases
NASA Astrophysics Data System (ADS)
Napiórkowski, Marek; Piasecki, Jarosław
2017-06-01
We consider two-dimensional imperfect attractive Fermi and repulsive Bose gases consisting of spinless point particles whose total interparticle interaction energy is represented by a N2/2 V with a =-aF≤0 for fermions and a =aB≥0 for bosons. We show that, in spite of the attraction, the thermodynamics of a d =2 imperfect Fermi gas remains well defined for 0 ≤aF≤a0=h2/2 π m , and is exactly the same as the one of the repulsive imperfect Bose gas with aB=a0-aF . In particular, for aF=a0 one observes the thermodynamic equivalence of the attractive imperfect Fermi gas and the ideal Bose gas.
Bose polaron problem: Effect of mass imbalance on binding energy
NASA Astrophysics Data System (ADS)
Ardila, L. A. Peña; Giorgini, S.
2016-12-01
By means of quantum Monte Carlo methods we calculate the binding energy of an impurity immersed in a Bose-Einstein condensate at T =0 . The focus is on the attractive branch of the Bose polaron and on the role played by the mass imbalance between the impurity and the surrounding particles. For an impurity resonantly coupled to the bath, we investigate the dependence of the binding energy on the mass ratio and on the interaction strength within the medium. In particular, we determine the equation of state in the case of a static (infinite mass) impurity, where three-body correlations are irrelevant and the result is expected to be a universal function of the gas parameter. For the mass ratio corresponding to 40K impurities in a gas of 87Rb atoms, we provide an explicit comparison with the experimental findings of a recent study carried out at JILA.
Evolution and dynamical properties of Bose-Einstein condensate dark matter stars
NASA Astrophysics Data System (ADS)
Madarassy, Eniko J. M.; Toth, Viktor T.
2015-02-01
Using recently developed nonrelativistic numerical simulation code, we investigate the stability properties of compact astrophysical objects that may be formed due to the Bose-Einstein condensation of dark matter. Once the temperature of a boson gas is less than the critical temperature, a Bose-Einstein condensation process can always take place during the cosmic history of the Universe. Because of dark matter accretion, a Bose-Einstein condensed core can also be formed inside massive astrophysical objects such as neutron stars or white dwarfs, for example. Numerically solving the Gross-Pitaevskii-Poisson system of coupled differential equations, we demonstrate, with longer simulation runs, that within the computational limits of the simulation the objects we investigate are stable. Physical properties of a self-gravitating Bose-Einstein condensate are examined both in nonrotating and rotating cases.
Performance analysis and parametric optimum criteria of an irreversible Bose-Otto engine
NASA Astrophysics Data System (ADS)
Wang, Hao; Liu, Sanqiu; He, Jizhou
2009-04-01
An irreversible cycle model of a Bose-Otto engine is established, in which finite time thermodynamic processes and the irreversibility result from the nonisentropic compression and expansion processes are taken into account. Based on the model, expressions for the power output and efficiency of the Bose-Otto engine are derived. On the basis of the thermodynamic properties of ideal Bose gas, the effects of the irreversibility and the compression ratio of the two isochoric processes on the performance of the Bose-Otto engine are revealed and some important performance parameters are optimized. Furthermore, some optimal operating regions including those for the power output, efficiency, and the temperatures of the cyclic working substance at two important state points are determined and evaluated. Finally, several special cases are discussed in detail.
Coherent tunneling of atoms from Bose-condensed gases at finite temperatures
NASA Astrophysics Data System (ADS)
Luxat, David L.; Griffin, Allan
2002-04-01
Tunneling of atoms between two trapped Bose-condensed gases at finite temperatures is explored using a many-body linear-response tunneling formalism similar to that used in superconductors. To lowest order, the tunneling currents can be expressed quite generally in terms of the single-particle Green's functions of isolated Bose gases. A coherent first-order tunneling Josephson current between two atomic Bose-Einstein condensates is found, in addition to coherent and dissipative contributions from second-order condensate-noncondensate and noncondensate-noncondensate tunneling. Our work is a generalization of Meier and Zwerger, who recently treated tunneling between uniform atomic Bose gases. We apply our formalism to the analysis of an out-coupling experiment induced by light wave fields, using a simple Bogoliubov-Popov quasiparticle approximation for the trapped Bose gas. For tunneling into the vacuum, we recover the results of Japha, Choi, Burnett, and Band, who recently pointed out the usefulness of studying the spectrum of out-coupled atoms. In particular, we show that the small tunneling current of noncondensate atoms from a trapped Bose gas has a broad spectrum of energies, with a characteristic structure associated with the Bogoliubov quasiparticle u2 and v2 amplitudes.
Bose-Einstein condensation of quasi-equilibrium magnons at room temperature under pumping.
Demokritov, S O; Demidov, V E; Dzyapko, O; Melkov, G A; Serga, A A; Hillebrands, B; Slavin, A N
2006-09-28
Bose-Einstein condensation is one of the most fascinating phenomena predicted by quantum mechanics. It involves the formation of a collective quantum state composed of identical particles with integer angular momentum (bosons), if the particle density exceeds a critical value. To achieve Bose-Einstein condensation, one can either decrease the temperature or increase the density of bosons. It has been predicted that a quasi-equilibrium system of bosons could undergo Bose-Einstein condensation even at relatively high temperatures, if the flow rate of energy pumped into the system exceeds a critical value. Here we report the observation of Bose-Einstein condensation in a gas of magnons at room temperature. Magnons are the quanta of magnetic excitations in a magnetically ordered ensemble of magnetic moments. In thermal equilibrium, they can be described by Bose-Einstein statistics with zero chemical potential and a temperature-dependent density. In the experiments presented here, we show that by using a technique of microwave pumping it is possible to excite additional magnons and to create a gas of quasi-equilibrium magnons with a non-zero chemical potential. With increasing pumping intensity, the chemical potential reaches the energy of the lowest magnon state, and a Bose condensate of magnons is formed.
Three-Body Losses in Trapped Bose-Einstein Condensed Gases
NASA Astrophysics Data System (ADS)
Kim, Yeong E.; Zubarev, Alexander L.
2004-05-01
A time-dependent Kohn-Sham (KS)-like equation for N bosons in a trap [1] is generalized for the case of inelastic collisions [2]. We derive adiabatic equations which are used to calculate the nonlinear dynamics of the Bose-Einstein condensate (BEC) and non-mean field corrections due to the three-body recombination. We find that the calculated corrections are about 13 times larger for 3D trapped dilute bose gases and about 7 times larger for 1D trapped weakly interacting bose gases when compared with the corresponding corrections for the ground state energy and for the collective frequencies. The comparising of the our numerical calculations with corresponding experimental data will be discussed. [1] Y.E. Kim and A.L. Zubarev, Phys. Rev. A67, 015602 (2003). [2] Y.E. Kim and A.L. Zubarev, Phys. Rev. A (in print); cond-mat/0305089.
Chen, Yizhao; Liu, Qinde; Yong, Sharon; Teo, Hui Ling; Lee, Tong Kooi
2014-01-20
Triglycerides are widely tested in clinical laboratories using enzymatic methods for lipid profiling. As enzymatic methods can be affected by interferences from biological samples, this together with the non-specific nature of triglycerides measurement makes it necessary to verify the accuracy of the test results with a reference measurement procedure. Several such measurement procedures had been published. These procedures generally involved lengthy and laborious sample preparation steps. In this paper, an improved reference measurement procedure for triglycerides and total glycerides was reported which simplifies the sample preparation steps and greatly shortens the time taken. The procedure was based on isotope dilution gas chromatography-mass spectrometry (IDGC-MS)with tripalmitin as the calibration standard. Serum samples were first spiked with isotope-labeled tripalmitin. For the measurement of triglycerides, the serum samples were subjected to lipid extraction followed by separation of triglycerides from diglycerides and monoglycerides. Triglycerides were then hydrolyzed to glycerol, derivatized and injected into the GC–MS for quantification. For the measurement of total glycerides, the serum samples were hydrolyzed directly and derivatized before injection into the GC-MS for quantification. All measurement results showed good precision with CV <1%. A certified reference material (CRM) of lipids in frozen human serum was used to verify the accuracy of the measurement. The obtained values for both triglycerides and total glycerides were well within the certified ranges of the CRM, with deviation <0.4% from the certified values. The relative expanded uncertainties were also comparable with the uncertainties associated with the certified values of the CRM. The validated procedure was used in an External Quality Assessment (EQA) Program organized by our laboratory to establish the assigned values for triglycerides and total glycerides.
Andreis, Elisabeth; Küllmer, Kai
2014-01-01
Self-monitoring of blood glucose (BG) by means of handheld BG systems is a cornerstone in diabetes therapy. The aim of this article is to describe a procedure with proven traceability for calibration and evaluation of BG systems to guarantee reliable BG measurements. Isotope dilution gas chromatography mass spectrometry (ID/GC/MS) is a method that fulfills all requirements to be used in a higher-order reference measurement procedure. However, this method is not applicable for routine measurements because of the time-consuming sample preparation. A hexokinase method with perchloric acid (PCA) sample pretreatment is used in a measurement procedure for such purposes. This method is directly linked to the ID/GC/MS method by calibration with a glucose solution that has an ID/GC/MS-determined target value. BG systems are calibrated with whole blood samples. The glucose levels in such samples are analyzed by this ID/GC/MS-linked hexokinase method to establish traceability to higher-order reference material. For method comparison, the glucose concentrations in 577 whole blood samples were measured using the PCA-hexokinase method and the ID/GC/MS method; this resulted in a mean deviation of 0.1%. The mean deviation between BG levels measured in >500 valid whole blood samples with BG systems and the ID/GC/MS was 1.1%. BG systems allow a reliable glucose measurement if a true reference measurement procedure, with a noninterrupted traceability chain using ID/GC/MS linked hexokinase method for calibration of BG systems, is implemented. Systems should be calibrated by means of a traceable and defined measurement procedure to avoid bias. PMID:24876614
Andreis, Elisabeth; Küllmer, Kai; Appel, Matthias
2014-05-01
Self-monitoring of blood glucose (BG) by means of handheld BG systems is a cornerstone in diabetes therapy. The aim of this article is to describe a procedure with proven traceability for calibration and evaluation of BG systems to guarantee reliable BG measurements. Isotope dilution gas chromatography mass spectrometry (ID/GC/MS) is a method that fulfills all requirements to be used in a higher-order reference measurement procedure. However, this method is not applicable for routine measurements because of the time-consuming sample preparation. A hexokinase method with perchloric acid (PCA) sample pretreatment is used in a measurement procedure for such purposes. This method is directly linked to the ID/GC/MS method by calibration with a glucose solution that has an ID/GC/MS-determined target value. BG systems are calibrated with whole blood samples. The glucose levels in such samples are analyzed by this ID/GC/MS-linked hexokinase method to establish traceability to higher-order reference material. For method comparison, the glucose concentrations in 577 whole blood samples were measured using the PCA-hexokinase method and the ID/GC/MS method; this resulted in a mean deviation of 0.1%. The mean deviation between BG levels measured in >500 valid whole blood samples with BG systems and the ID/GC/MS was 1.1%. BG systems allow a reliable glucose measurement if a true reference measurement procedure, with a noninterrupted traceability chain using ID/GC/MS linked hexokinase method for calibration of BG systems, is implemented. Systems should be calibrated by means of a traceable and defined measurement procedure to avoid bias.
Wang, Sheng-Meng; Wang, Ting-Cheng; Giang, Yun-Seng
2005-02-25
A simple, rapid, reliable, and economic analytical scheme starting with in situ liquid-liquid extraction and asymmetric (or diastereomeric) chemical derivatization (ChD) followed by gas chromatography (GC)-isotope dilution mass spectrometry (MS) is described for the simultaneous determination of D- and L-amphetamine (AP) and methamphetamine (MA) in urine which could have resulted from the administration of various forms of questioned amphetamines or amphetamines-generating drugs. By using L-N-trifluoroacetyl-1-prolyl chloride (L-TPC) as chiral derivatizing agent, resolutions of 2.2 and 2.0 were achieved for the separation of AP and MA enantiomeric pairs, respectively, on an ordinary HP-5MS capillary column. The GC-MS quantitation was carried out in the selected ion monitoring (SIM) mode using m/z 237 and 251 as the quantifier ions for the respective diastereomeric pairs of AP-L-TPC and MA-L-TPC. The calibration curves plotted for the two pairs of analytes stretch with good linearity down to 45 ng/mL, and the limits of detection and quantitation determined were as low as 40 and 45 ng/mL, respectively. Also, a comparative study using 10 real-case urine specimens previously screened as positive for MA administration showed mostly tolerable biases between the two sums (of concentration) of D- and L-MA obtained via an asymmetric L-TPC-ChD approach and via an ordinary pentafluoropropionylation (PFPA-ChD) approach, respectively, as well as between the two sums of D- and L-AP obtained thereupon, thus validating the proposed analytical scheme as a promising forensic protocol for the detailed analysis of enantiomeric amphetamines in urine.
Bose-Einstein condensation and indirect excitons: a review
NASA Astrophysics Data System (ADS)
Combescot, Monique; Combescot, Roland; Dubin, François
2017-06-01
We review recent progress on Bose-Einstein condensation (BEC) of semiconductor excitons. The first part deals with theory, the second part with experiments. This Review is written at a time where the problem of exciton Bose-Einstein condensation has just been revived by the understanding that the exciton condensate must be dark because the exciton ground state is not coupled to light. Here, we theoretically discuss this missed understanding before providing its experimental support through experiments that scrutinize indirect excitons made of spatially separated electrons and holes. The theoretical part first discusses condensation of elementary bosons. In particular, the necessary inhibition of condensate fragmentation by exchange interaction is stressed, before extending the discussion to interacting bosons with spin degrees of freedom. The theoretical part then considers composite bosons made of two fermions like semiconductor excitons. The spin structure of the excitons is detailed, with emphasis on the crucial fact that ground-state excitons are dark: indeed, this imposes the exciton Bose-Einstein condensate to be not coupled to light in the dilute regime. Condensate fragmentations are then reconsidered. In particular, it is shown that while at low density, the exciton condensate is fully dark, it acquires a bright component, coherent with the dark one, beyond a density threshold: in this regime, the exciton condensate is ‘gray’. The experimental part first discusses optical creation of indirect excitons in quantum wells, and the detection of their photoluminescence. Exciton thermalisation is also addressed, as well as available approaches to estimate the exciton density. We then switch to specific experiments where indirect excitons form a macroscopic fragmented ring. We show that such ring provides efficient electrostatic trapping in the region of the fragments where an essentially-dark exciton Bose-Einstein condensate is formed at sub-Kelvin bath
Bose-Einstein condensation and indirect excitons: a review.
Combescot, Monique; Combescot, Roland; Dubin, François
2017-06-01
We review recent progress on Bose-Einstein condensation (BEC) of semiconductor excitons. The first part deals with theory, the second part with experiments. This Review is written at a time where the problem of exciton Bose-Einstein condensation has just been revived by the understanding that the exciton condensate must be dark because the exciton ground state is not coupled to light. Here, we theoretically discuss this missed understanding before providing its experimental support through experiments that scrutinize indirect excitons made of spatially separated electrons and holes. The theoretical part first discusses condensation of elementary bosons. In particular, the necessary inhibition of condensate fragmentation by exchange interaction is stressed, before extending the discussion to interacting bosons with spin degrees of freedom. The theoretical part then considers composite bosons made of two fermions like semiconductor excitons. The spin structure of the excitons is detailed, with emphasis on the crucial fact that ground-state excitons are dark: indeed, this imposes the exciton Bose-Einstein condensate to be not coupled to light in the dilute regime. Condensate fragmentations are then reconsidered. In particular, it is shown that while at low density, the exciton condensate is fully dark, it acquires a bright component, coherent with the dark one, beyond a density threshold: in this regime, the exciton condensate is 'gray'. The experimental part first discusses optical creation of indirect excitons in quantum wells, and the detection of their photoluminescence. Exciton thermalisation is also addressed, as well as available approaches to estimate the exciton density. We then switch to specific experiments where indirect excitons form a macroscopic fragmented ring. We show that such ring provides efficient electrostatic trapping in the region of the fragments where an essentially-dark exciton Bose-Einstein condensate is formed at sub-Kelvin bath
Dilution in single pass arc welds
DuPont, J.N.; Marder, A.R.
1996-06-01
A study was conducted on dilution of single pass arc welds of type 308 stainless steel filler metal deposited onto A36 carbon steel by the plasma arc welding (PAW), gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. Knowledge of the arc and melting efficiency was used in a simple energy balance to develop an expression for dilution as a function of welding variables and thermophysical properties of the filler metal and substrate. Comparison of calculated and experimentally determined dilution values shows the approach provides reasonable predictions of dilution when the melting efficiency can be accurately predicted. The conditions under which such accuracy is obtained are discussed. A diagram is developed from the dilution equation which readily reveals the effect of processing parameters on dilution to aid in parameter optimization.
Solitonic vortices in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Tylutki, M.; Donadello, S.; Serafini, S.; Pitaevskii, L. P.; Dalfovo, F.; Lamporesi, G.; Ferrari, G.
2015-04-01
We analyse, theoretically and experimentally, the nature of solitonic vortices (SV) in an elongated Bose-Einstein condensate. In the experiment, such defects are created via the Kibble-Zurek mechanism, when the temperature of a gas of sodium atoms is quenched across the BEC transition, and are imaged after a free expansion of the condensate. By using the Gross-Pitaevskii equation, we calculate the in-trap density and phase distributions characterizing a SV in the crossover from an elongated quasi-1D to a bulk 3D regime. The simulations show that the free expansion strongly amplifies the key features of a SV and produces a remarkable twist of the solitonic plane due to the quantized vorticity associated with the defect. Good agreement is found between simulations and experiments.
Approaching Bose-Einstein Condensation
ERIC Educational Resources Information Center
Ferrari, Loris
2011-01-01
Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…
Approaching Bose-Einstein Condensation
ERIC Educational Resources Information Center
Ferrari, Loris
2011-01-01
Bose-Einstein condensation (BEC) is discussed at the level of an advanced course of statistical thermodynamics, clarifying some formal and physical aspects that are usually not covered by the standard pedagogical literature. The non-conventional approach adopted starts by showing that the continuum limit, in certain cases, cancels out the crucial…
Thermodynamics of Dilute Solutions.
ERIC Educational Resources Information Center
Jancso, Gabor; Fenby, David V.
1983-01-01
Discusses principles and definitions related to the thermodynamics of dilute solutions. Topics considered include dilute solution, Gibbs-Duhem equation, reference systems (pure gases and gaseous mixtures, liquid mixtures, dilute solutions), real dilute solutions (focusing on solute and solvent), terminology, standard states, and reference systems.…
Number-conserving approaches to n-component Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Mason, Peter; Gardiner, Simon A.
2014-04-01
We develop the number-conserving approach, which has previously been used in a single-component Bose-Einstein condensed dilute atomic gas, to describe consistent coupled condensate and noncondensate number dynamics, to an n-component condensate. The resulting system of equations is comprised, for each component, of a generalized Gross-Pitaevskii equation coupled to modified Bogoliubov-de Gennes equations. Lower order approximations yield general formulations for multicomponent Gross-Pitaevskii equations, and systems of multicomponent Gross-Pitaevskii equations coupled to multicomponent modified number-conserving Bogoliubov-de Gennes equations. The analysis is left general, such that, in the n-component condensate, there may or may not be mutually coherent components. An expansion in powers of the ratio of noncondensate-to-condensate particle numbers for each coherent set is used to derive the self-consistent, second-order, dynamical equations of motion. The advantage of the analysis developed in this article is in its applications to dynamical instabilities that appear when two (or more) components are in conflict and where a significant noncondensed fraction of atoms is expected to appear.
Gross-Pitaevskii Approximation for the Bose-Einstein Condensation: Green Function Formalism.
NASA Astrophysics Data System (ADS)
Trallero-Giner, Carlos; Trallero-Herrero, Carlos; Birman, Joseph L.
2003-03-01
Using the Green function method we solved the time-independent, T=O K, one-dimension, Gross-Pitaevskii equation (G-PE) for the Bose-Einstein condensation in dilute atomic alkali gases. We are able to formally obtain an analytical solution for the order parameter Ψ (x) and for the chemical potential μ as a function of the trapping frequency ω and the effective interaction constant \\overlineΛ . A Bonn-Neuman iterative procedure is implemented for solving the non-linear system of equations obtained from the G-PE equations into the formalism. Also, we compare the G.f. formalism and two other method of solution: variational (soliton solution) and perturbation theory for the universal parameter, \\overlineΛ /(lhbar ω ) (l is the magnetic length), which characterize the atomic gas condensation. Generalization of the above mentioned methods for two order parameter Ψ _i(x); i=1,2 (i.e. two species of alkali atoms) is also presented.
Zinke, Maximilian; Hanff, Erik; Böhmer, Anke; Supuran, Claudiu T; Tsikas, Dimitrios
2016-01-01
The intrinsic activity of carbonic anhydrase (CA) is the hydration of CO2 to carbonic acid and its dehydration to CO2. CA may also function as esterase and phosphatase. Recently, we demonstrated that renal CA is mainly responsible for the reabsorption of nitrite (NO2(-)) which is the most abundant reservoir of the biologically highly potent nitric oxide (NO). By means of a stable-isotope dilution GC-MS method, we discovered a novel CA activity which strictly depends upon nitrite. We found that bovine erythrocytic CAII (beCAII) catalyses the incorporation of (18)O from H2 (18)O into nitrite at pH 7.4. After derivatization with pentafluorobenzyl bromide, gas chromatographic separation and mass spectrometric analysis, we detected ions at m/z 48 for singly (18)O-labelled nitrite ((16)O=N-(18)O(-)/(18)O=N-(16)O(-)) and at m/z 50 for doubly (18)O-labelled nitrite ((18)O=N-(18)O(-)) in addition to m/z 46 for unlabelled nitrite. Using (15)N-labelled nitrite ((15)NO2 (-), m/z 47) as an internal standard and selected-ion monitoring of m/z 46, m/z 48, m/z 50 and m/z 47, we developed a GC-MS microassay for the quantitative determination of the nitrite-dependent beCAII activity. The CA inhibitors acetazolamide and FC5 207A did not alter beCAII-catalysed formation of singly and doubly (18)O-labelled nitrite. Cysteine and the experimental CA inhibitor DIDS (a diisothiocyanate) increased several fold the beCAII-catalysed formation of the (18)O-labelled nitrite species. Cysteine, acetazolamide, FC5 207A, and DIDS by themselves had no effect on the incorporation of (18)O from H2 (18)O into nitrite. We conclude that erythrocytic CA possesses a nitrite-dependent activity which can only be detected when nitrite is used as the substrate and the reaction is performed in buffers of neutral pH values prepared in H2 (18)O. This novel CA activity, i.e., the nitrous acid anhydrase activity, represents a bioactivation of nitrite and may have both beneficial (via S-nitrosylation and subsequent
Nie, Zhiyong; Zhang, Yajiao; Chen, Jia; Lin, Ying; Wu, Bidong; Dong, Yuan; Feng, Jianlin; Liu, Qin; Xie, Jianwei
2014-08-01
A highly sensitive method for the determination of sulfur mustard (SM) metabolites thiodiglycol (TDG) and thiodiglycol sulfoxide (TDGO) in urine was established and validated using isotope-dilution negative-ion chemical ionization (NICI) gas chromatography-mass spectrometry (GC-MS). TDGO in the samples was reduced with TiCl3, and then determined together with TDG as a single analyte. The sample preparation procedures, including two solid-phase-extraction (SPE) clean-up steps, were optimized to improve the sensitivity of the method. The limits of detection (LOD) for both TDG and TDG plus TDGO (TDG + TDGO) were 0.1 ng mL(-1), and the limits of quantitation (LOQ) for both were 0.3 ng mL(-1). The method was used in a rabbit cutaneous SM exposure model. Domestic rabbits were exposed to neat liquid SM at three dosage levels (0.02, 0.05, and 0.15 LD50), and the urinary excretion of four species of hydrolysis metabolites, namely free TDG, free plus conjugated TDG (total TDG), free TDG + TDGO, and free plus conjugated TDG + TDGO (total TDG + TDGO), was evaluated to investigate the metabolic processes. The total urinary excretion profiles of the metabolites, including the peak time, time window, and dose-response and time-response relationships, were clarified. The results revealed that the concentrations of TDG and TDG + TDGO in the urine increased quickly and then decreased rapidly in the first two days after SM exposure. The cumulative amount of total TDG + TDGO excreted in urine during the first five days accounted for 0.5-1% of the applied dose of SM. It is also concluded that TDG and TDGO in urine existed mainly in free form, the levels of glucuronide and of sulfate conjugates of TDG or TDGO were very low, and most hydrolysis metabolites were present in the oxidized form (TDGO). The study indicates that the abnormal increase of TDG and TDGO excretion levels can be used as a diagnostic indicator and establishes a reference time-window for retrospective analysis and
Collisions of Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Reinhardt, William P.; Clark, Charles W.
1997-03-01
Recent experiments(N. J. van Druten et al.), preprint (1996) have begun to study collisions of dilute Bose-Einstein condensates (BECs), and we are exploring BEC collisional phenomena in a simplified model. Two BECs are separated by a barrier, which is dropped to allow them to interact; in the initial configuration, the two BECs may have different phases. Time evolution is described by numerically solving the time-dependent nonlinear Schrödinger equation for a BEC confined by hard walls in a region of constant external potential. We find that zero--energy collisions between ground state condensates that are separately prepared, and then juxtaposed, are dominated by solitons, and that soliton properties are controlled by the phase difference and initial separation of the colliding condensates. The basic ideas of Anderson(P. W. Anderson, Basic Notions of Condensed Matter Physics) (Addison Wesley, Reading, MA, 1984) p. 18 relating to phase rigidity of ``cold quantum matter'' display themselves in a robust manner; this suggests the inevitability of Josephson-type effects for artificially separated but weakly interacting BEC ground states. Partial results are presented in remote figures. goes between the ; the system generates the footnote number.
Bose glass and Mott glass of quasiparticles in a doped quantum magnet.
Yu, Rong; Yin, Liang; Sullivan, Neil S; Xia, J S; Huan, Chao; Paduan-Filho, Armando; Oliveira, Nei F; Haas, Stephan; Steppke, Alexander; Miclea, Corneliu F; Weickert, Franziska; Movshovich, Roman; Mun, Eun-Deok; Scott, Brian L; Zapf, Vivien S; Roscilde, Tommaso
2012-09-20
The low-temperature states of bosonic fluids exhibit fundamental quantum effects at the macroscopic scale: the best-known examples are Bose-Einstein condensation and superfluidity, which have been tested experimentally in a variety of different systems. When bosons interact, disorder can destroy condensation, leading to a 'Bose glass'. This phase has been very elusive in experiments owing to the absence of any broken symmetry and to the simultaneous absence of a finite energy gap in the spectrum. Here we report the observation of a Bose glass of field-induced magnetic quasiparticles in a doped quantum magnet (bromine-doped dichloro-tetrakis-thiourea-nickel, DTN). The physics of DTN in a magnetic field is equivalent to that of a lattice gas of bosons in the grand canonical ensemble; bromine doping introduces disorder into the hopping and interaction strength of the bosons, leading to their localization into a Bose glass down to zero field, where it becomes an incompressible Mott glass. The transition from the Bose glass (corresponding to a gapless spin liquid) to the Bose-Einstein condensate (corresponding to a magnetically ordered phase) is marked by a universal exponent that governs the scaling of the critical temperature with the applied field, in excellent agreement with theoretical predictions. Our study represents a quantitative experimental account of the universal features of disordered bosons in the grand canonical ensemble.
The effect of adiabaticity on strongly quenched Bose Einstein Condensates
NASA Astrophysics Data System (ADS)
Ling, Hong; Kain, Ben
2015-05-01
We study the properties of a Bose-Einstein condensate following a deep quench to a large scattering length during which the condensate fraction nc changes with time. We construct a closed set of equations that highlight the role of the adiabaticity or equivalently, dnc/dt, the rate change of nc, which is to induce an (imaginary) effective interaction between quasiparticles. We show analytically that such a system supports a steady state characterized by a constant condensate density and a steady but periodically changing momentum distribution, whose time average is described exactly by the generalized Gibbs ensemble. We discuss how the nc -induced effective interaction, which cannot be ignored on the grounds of the adiabatic approximation for modes near the gapless Goldstone mode, can significantly affect condensate populations and Tan's contact for a Bose gas that has undergone a deep quench. In particular, we find that even when the Bose gas is quenched to unitarity, nc(t) does not completely deplete, approaching, instead, to a steady state with a finite condensate fraction. ITAMP, Harvard-Smithsonian Center for Astrophysics; KITP, University of Santa Barbara.
Internal Josephson effects in spinor dipolar Bose-Einstein condensates
Yasunaga, Masashi; Tsubota, Makoto
2010-02-15
We theoretically study the internal Josephson effect, which is driven by spin-exchange interactions and magnetic dipole-dipole interactions, in a three-level system for spin-1 Bose-Einstein condensates, obtaining novel spin dynamics. We introduce single spatial mode approximations into the Gross-Pitaevskii equations and derive the Josephson-type equations, which are analogous to tunneling currents through three junctions between three superconductors. From an analogy with two interacting nonrigid pendulums, we identify unique varied oscillational modes, called the 0-{pi}, 0-running, running-running, 2n{pi} and running-2{pi}, single nonrigid pendulum, and two rigid pendulums phase modes. These Josephson modes in the three states are expected to be found in real atomic Bose gas systems.
Landau criterion for an anisotropic Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Yu, Zeng-Qiang
2017-03-01
In this work we discuss the Landau criterion for anisotropic superfluidity. To this end we consider a pointlike impurity moving in a uniform Bose-Einstein condensate with either interparticle dipole-dipole interaction or Raman-induced spin-orbit coupling. In both cases we find that the Landau critical velocity vc is generally smaller than the sound velocity in the moving direction. Beyond vc, the energy dissipation rate is explicitly calculated via a perturbation approach. In the plane-wave phase of a spin-orbit-coupled Bose gas, the dissipationless motion is suppressed by the Raman coupling even in the direction orthogonal to the recoil momentum. Our predictions can be tested in the experiments with ultracold atoms.
Sideband Rabi spectroscopy of finite-temperature trapped Bose gases
NASA Astrophysics Data System (ADS)
Allard, Baptiste; Fadel, Matteo; Schmied, Roman; Treutlein, Philipp
2016-04-01
We use Rabi spectroscopy to explore the low-energy excitation spectrum of a finite-temperature Bose gas of rubidium atoms across the phase transition to a Bose-Einstein condensate (BEC). To record this spectrum, we coherently drive the atomic population between two spin states. A small relative displacement of the spin-specific trapping potentials enables sideband transitions between different motional states. The intrinsic nonlinearity of the motional spectrum, mainly originating from two-body interactions, makes it possible to resolve and address individual excitation lines. Together with sensitive atom counting, this constitutes a feasible technique to count single excited atoms of a BEC and to determine the temperature of nearly pure condensates. As an example, we show that for a nearly pure BEC of N =800 atoms the first excited state has a population of less than five atoms, corresponding to an upper bound on the temperature of 30 nK .
Observation of collective atomic recoil motion in a degenerate fermion gas.
Wang, Pengjun; Deng, L; Hagley, E W; Fu, Zhengkun; Chai, Shijie; Zhang, Jing
2011-05-27
We demonstrate collective atomic recoil motion with a dilute, ultracold, degenerate fermion gas in a single spin state. By utilizing an adiabatically decompressed magnetic trap with an aspect ratio different from that of the initial trap, a momentum-squeezed fermion cloud is achieved. With a single pump pulse of the proper polarization, we observe, for the first time, multiple wave-mixing processes that result in distinct collective atomic recoil motion modes in a degenerate fermion cloud. Contrary to the case with Bose condensates, no pump-laser detuning asymmetry is present.
Bose polarons in the strongly interacting regime
NASA Astrophysics Data System (ADS)
Kedar, Dhruv; Hu, Ming-Guang; van de Graaff, Michael; Corson, John; Cornell, Eric; Jin, Deborah
2016-05-01
Impurities immersed in and interacting with a Bose-Einstein condensate (BEC) are predicted to form quasiparticle excitations called Bose polarons. I will present experimental evidence of Bose polarons in cold atoms obtained using radio-frequency spectroscopy to measure the excitation spectrum of fermionic K-40 impurities interacting with a BEC of Rb-87 atoms. We use an interspecies Feshbach resonance to tune the interactions between the impurities and the bosons, and we take data in the strongly interacting regime.
Dipole oscillations of a Bose-Einstein condensate in the presence of defects and disorder.
Albert, M; Paul, T; Pavloff, N; Leboeuf, P
2008-06-27
We consider dipole oscillations of a trapped dilute Bose-Einstein condensate in the presence of a scattering potential consisting either in a localized defect or in an extended disordered potential. In both cases the breaking of superfluidity and the damping of the oscillations are shown to be related to the appearance of a nonlinear dissipative flow. At supersonic velocities the flow becomes asymptotically dissipationless.
Fernández-Fernández, Mario; Rodríguez-González, Pablo; Añón Álvarez, M Elena; Rodríguez, Felix; Menéndez, Francisco V Álvarez; García Alonso, J Ignacio
2015-04-07
This work describes the first multiple spiking isotope dilution procedure for organic compounds using (13)C labeling. A double-spiking isotope dilution method capable of correcting and quantifying the creatine-creatinine interconversion occurring during the analytical determination of both compounds in human serum is presented. The determination of serum creatinine may be affected by the interconversion between creatine and creatinine during sample preparation or by inefficient chemical separation of those compounds by solid phase extraction (SPE). The methodology is based on the use differently labeled (13)C analogues ((13)C1-creatinine and (13)C2-creatine), the measurement of the isotopic distribution of creatine and creatinine by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and the application of multiple linear regression. Five different lyophilized serum-based controls and two certified human serum reference materials (ERM-DA252a and ERM-DA253a) were analyzed to evaluate the accuracy and precision of the proposed double-spike LC-MS/MS method. The methodology was applied to study the creatine-creatinine interconversion during LC-MS/MS and gas chromatography-mass spectrometry (GC-MS) analyses and the separation efficiency of the SPE step required in the traditional gas chromatography-isotope dilution mass spectrometry (GC-IDMS) reference methods employed for the determination of serum creatinine. The analysis of real serum samples by GC-MS showed that creatine-creatinine separation by SPE can be a nonquantitative step that may induce creatinine overestimations up to 28% in samples containing high amounts of creatine. Also, a detectable conversion of creatine into creatinine was observed during sample preparation for LC-MS/MS. The developed double-spike LC-MS/MS improves the current state of the art for the determination of creatinine in human serum by isotope dilution mass spectrometry (IDMS), because corrections are made for all the possible errors
Polymer Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Castellanos, E.; Chacón-Acosta, G.
2013-05-01
In this work we analyze a non-interacting one-dimensional polymer Bose-Einstein condensate in a harmonic trap within the semiclassical approximation. We use an effective Hamiltonian coming from the polymer quantization that arises in loop quantum gravity. We calculate the number of particles in order to obtain the critical temperature. The Bose-Einstein functions are replaced by series, whose high order terms are related to powers of the polymer length. It is shown that the condensation temperature presents a shift respect to the standard case, for small values of the polymer scale. In typical experimental conditions, it is possible to establish a bound for λ2 up to ≲10-16 m2. To improve this bound we should decrease the frequency of the trap and also decrease the number of particles.
Bose-Einstein condensation of {alpha} particles and Airy structure in nuclear rainbow scattering
Ohkubo, S.; Hirabayashi, Y.
2004-10-01
It is shown that the dilute density distribution of {alpha} particles in nuclei can be observed in the Airy structure in nuclear rainbow scattering. We have analyzed {alpha}+{sup 12}C rainbow scattering to the 0{sub 2}{sup +} (7.65 MeV) state of {sup 12}C in a coupled-channel method with the precise wave functions for {sup 12}C. It is found that the enhanced Airy oscillations in the experimental angular distributions for the 0{sub 2}{sup +} state is caused by the dilute density distribution of this state in agreement for the idea of Bose-Einstein condensation of the three alpha particles.
ERIC Educational Resources Information Center
Kamin, Lawrence
1996-01-01
Presents problems appropriate for high school and college students that highlight dilution methods. Promotes an understanding of dilution methods in order to prevent the unnecessary waste of chemicals and glassware in biology laboratories. (JRH)
ERIC Educational Resources Information Center
Kamin, Lawrence
1996-01-01
Presents problems appropriate for high school and college students that highlight dilution methods. Promotes an understanding of dilution methods in order to prevent the unnecessary waste of chemicals and glassware in biology laboratories. (JRH)
Soliton resonance in bose-einstein condensate
NASA Technical Reports Server (NTRS)
Zak, Michail; Kulikov, I.
2002-01-01
A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.
Soliton resonance in bose-einstein condensate
NASA Technical Reports Server (NTRS)
Zak, Michail; Kulikov, I.
2002-01-01
A new phenomenon in nonlinear dispersive systems, including a Bose-Einstein Condensate (BEC), has been described. It is based upon a resonance between an externally induced soliton and 'eigen-solitons' of the homogeneous cubic Schrodinger equation. There have been shown that a moving source of positive /negative potential induces bright /dark solitons in an attractive / repulsive Bose condensate.
Collision of Bose Condensate Dark Matter structures
Guzman, F. S.
2008-12-04
The status of the scalar field or Bose condensate dark matter model is presented. Results about the solitonic behavior in collision of structures is presented as a possible explanation to the recent-possibly-solitonic behavior in the bullet cluster merger. Some estimates about the possibility to simulate the bullet cluster under the Bose Condensate dark matter model are indicated.
Serial Dilution Simulation Lab
ERIC Educational Resources Information Center
Keler, Cynthia; Balutis, Tabitha; Bergen, Kim; Laudenslager, Bryanna; Rubino, Deanna
2010-01-01
Serial dilution is often a difficult concept for students to understand. In this short dry lab exercise, students perform serial dilutions using seed beads. This exercise helps students gain skill at performing dilutions without using reagents, bacterial cultures, or viral cultures, while being able to visualize the process.
Serial Dilution Simulation Lab
ERIC Educational Resources Information Center
Keler, Cynthia; Balutis, Tabitha; Bergen, Kim; Laudenslager, Bryanna; Rubino, Deanna
2010-01-01
Serial dilution is often a difficult concept for students to understand. In this short dry lab exercise, students perform serial dilutions using seed beads. This exercise helps students gain skill at performing dilutions without using reagents, bacterial cultures, or viral cultures, while being able to visualize the process.
Bose-Einstein condensation of light: general theory.
Sob'yanin, Denis Nikolaevich
2013-08-01
A theory of Bose-Einstein condensation of light in a dye-filled optical microcavity is presented. The theory is based on the hierarchical maximum entropy principle and allows one to investigate the fluctuating behavior of the photon gas in the microcavity for all numbers of photons, dye molecules, and excitations at all temperatures, including the whole critical region. The master equation describing the interaction between photons and dye molecules in the microcavity is derived and the equivalence between the hierarchical maximum entropy principle and the master equation approach is shown. The cases of a fixed mean total photon number and a fixed total excitation number are considered, and a much sharper, nonparabolic onset of a macroscopic Bose-Einstein condensation of light in the latter case is demonstrated. The theory does not use the grand canonical approximation, takes into account the photon polarization degeneracy, and exactly describes the microscopic, mesoscopic, and macroscopic Bose-Einstein condensation of light. Under certain conditions, it predicts sub-Poissonian statistics of the photon condensate and the polarized photon condensate, and a universal relation takes place between the degrees of second-order coherence for these condensates. In the macroscopic case, there appear a sharp jump in the degrees of second-order coherence, a sharp jump and kink in the reduced standard deviations of the fluctuating numbers of photons in the polarized and whole condensates, and a sharp peak, a cusp, of the Mandel parameter for the whole condensate in the critical region. The possibility of nonclassical light generation in the microcavity with the photon Bose-Einstein condensate is predicted.
Radial vortex core oscillations in Bose-Einstein condensates
NASA Astrophysics Data System (ADS)
Verhelst, N.; Ichmoukhamedov, T.; Tempere, J.
2017-07-01
Dilute ultracold quantum gases form an ideal and highly tunable system in which superfluidity can be studied. Recently quantum turbulence in Bose-Einstein condensates was reported [PRL 103, 045310 (2009)], opening up a new experimental system that can be used to study quantum turbulence. A novel feature of this system is that vortex cores now have a finite size. This means that the vortices are no longer one dimensional features in the condensate, but that the radial behaviour and excitations might also play an important role in the study of quantum turbulence in Bose-Einstein condensates. In this paper we investigate these radial modes using a simplified variational model for the vortex core. This study results in the frequencies of the radial modes, which can be compared with the frequencies of the thoroughly studied Kelvin modes. From this comparison we find that the lowest (l = 0) radial mode has a frequency in the same order of magnitude as the Kelvin modes. However the radial modes still have a larger energy than the Kelvin modes, meaning that the Kelvin modes will still constitute the preferred channel for energy decay in quantum turbulence.
Quantum Monte Carlo method for the Bose-Hubbard model with harmonic confining potential.
Kato, Yasuyuki; Kawashima, Naoki
2009-02-01
We study the Bose-Hubbard model with an external harmonic field, which is effective for modeling a cold atomic Bose gas trapped in an optical lattice. We modify the directed-loop algorithm to simulate large systems efficiently. As a demonstration we carry out the simulation of a system consisting of 1. 8 x 10{5} particles on a 64{3} lattice. These numbers are comparable to those in the pioneering experimental work by Greiner [Nature (London) 415, 39 (2002)]. Furthermore, we observe coherence between two superfluid spheres separated by a Mott insulator region in a "wedding-cake" structure.
Bose-Einstein condensate on a persistent-supercurrent atom chip
NASA Astrophysics Data System (ADS)
Imai, Hiromitsu; Inaba, Kensuke; Tanji-Suzuki, Haruka; Yamashita, Makoto; Mukai, Tetsuya
2014-09-01
A Bose-Einstein condensate was achieved in a stable magnetic trap on a persistent-supercurrent atom chip with a superconducting closed-loop circuit. We determined precisely the shape of the magnetic trapping potential by systematically controlling the persistent supercurrent. The condensation was verified by time-of-flight imaging and by atom number decay measurements. The measured decay rates agreed quantitatively with numerical simulations on the three-body loss process assuming all of the atoms to be a condensate. We also discuss the feasibility of creating a quasi-one-dimensional Bose gas on our atom chip.
Superfluid-insulator transition of two-dimensional disordered Bose gases
NASA Astrophysics Data System (ADS)
Saliba, Joseph; Lugan, Pierre; Savona, Vincenzo
2014-09-01
We study the two-dimensional weakly repulsive Bose gas at zero temperature in the presence of correlated disorder. Using large-scale simulations, we show that the low-energy Bogoliubov cumulative density of states remains quadratic up to a critical disorder strength, beyond which a power law with disorder-dependent exponent β <2 sets in. We associate this threshold behavior with the transition from superfluid to Bose glass, and compare the resulting mean-field phase diagram with scaling laws and the Thomas-Fermi percolation threshold of the mean-field density profile.
NASA Astrophysics Data System (ADS)
Adhikari, S. K.; de Llano, M.; Sevilla, F. J.; Solís, M. A.; Valencia, J. J.
2007-03-01
We contrast four distinct versions of the BCS-Bose statistical crossover theory according to the form assumed for the electron-number equation that accompanies the BCS gap equation. The four versions correspond to explicitly accounting for two-hole-(2h) as well as two-electron-(2e) Cooper pairs (CPs), or both in equal proportions, or only either kind. This follows from a recent generalization of the Bose-Einstein condensation (GBEC) statistical theory that includes not boson-boson interactions but rather 2e- and also (without loss of generality) 2h-CPs interacting with unpaired electrons and holes in a single-band model that is easily converted into a two-band model. The GBEC theory is essentially an extension of the Friedberg-Lee 1989 BEC theory of superconductors that excludes 2h-CPs. It can thus recover, when the numbers of 2h- and 2e-CPs in both BE-condensed and non-condensed states are separately equal, the BCS gap equation for all temperatures and couplings as well as the zero-temperature BCS (rigorous-upper-bound) condensation energy for all couplings. But ignoring either 2h- or 2e-CPs it can do neither. In particular, only half the BCS condensation energy is obtained in the two crossover versions ignoring either kind of CPs. We show how critical temperatures Tc from the original BCS-Bose crossover theory in 2D require unphysically large couplings for the Cooper/BCS model interaction to differ significantly from the Tcs of ordinary BCS theory (where the number equation is substituted by the assumption that the chemical potential equals the Fermi energy).
NASA Astrophysics Data System (ADS)
Dorfner, F.; Heidrich-Meisner, F.
2016-06-01
We study properties of the single-site reduced density matrix in the Bose-Bose resonance model as a function of system parameters. This model describes a single-component Bose gas with a resonant coupling to a diatomic molecular state, here defined on a lattice. A main goal is to demonstrate that the eigenstates of the single-site reduced density matrix have structures that are characteristic for the various quantum phases of this system. Since the Hamiltonian conserves only the global particle number but not the number of bosons and molecules individually, these eigenstates, referred to as optimal modes, can be nontrivial linear combinations of bare eigenstates of the molecular and boson particle number. We numerically analyze the optimal modes and their weights, the latter giving the importance of the corresponding state, in the ground state of the Bose-Bose resonance model. We find that the single-site von Neumann entropy is sensitive to the location of the phase boundaries. We explain the structure of the optimal modes and their weight spectra using perturbation theory and via a comparison to results for the single-component Bose-Hubbard model. We further study the dynamical evolution of the optimal modes and of the single-site entanglement entropy in two quantum quenches that cross phase boundaries of the model and show that these quantities are thermal in the steady state. For our numerical calculations, we use the density-matrix renormalization group method for ground-state calculations and time evolution in a Krylov subspace for the quench dynamics as well as exact diagonalization.
Optical Devices for Cold Atoms and Bose-Einstein Condensates
Gaaloul, Naceur; Jaouadi, Amine; Telmini, Mourad; Pruvost, Laurence; Charron, Eric
2007-09-19
The manipulation of cold atoms with optical fields is a very promising technique for a variety of applications ranging from laser cooling and trapping to coherent atom transport and matter wave interferometry. Optical fields have also been proposed as interesting tools for quantum information processing with cold atoms. In this paper, we present a theoretical study of the dynamics of a cold {sup 87}Rb atomic cloud falling in the gravity field in the presence of two crossing dipole guides. The cloud is either deflected or split between the two branches of this guide. We explore the possibilities of optimization of this device and present preliminary results obtained in the case of zero-temperature dilute Bose-Einstein condensates.
Pairing and condensation in a resonant Bose-Fermi mixture
NASA Astrophysics Data System (ADS)
Fratini, Elisa; Pieri, Pierbiagio
2010-05-01
We study by diagrammatic means a Bose-Fermi mixture, with boson-fermion coupling tuned by a Fano-Feshbach resonance. For increasing coupling, the growing boson-fermion pairing correlations progressively reduce the boson condensation temperature and make it eventually vanish at a critical coupling. Such quantum critical point depends very weakly on the population imbalance and, for vanishing boson densities, coincides with that found for the polaron-molecule transition in a strongly imbalanced Fermi gas, thus bridging two quite distinct physical systems.
Robustness of discrete semifluxons in closed Bose-Hubbard chains
NASA Astrophysics Data System (ADS)
Gallemí, A.; Guilleumas, M.; Martorell, J.; Mayol, R.; Polls, A.; Juliá-Díaz, B.
2016-07-01
We present the properties of the ground state and low-energy excitations of Bose-Hubbard chains with a geometry that varies from open to closed and with a tunable twisted link. In the vicinity of the symmetric π-flux case the system behaves as an interacting gas of discrete semifluxons for finite chains and interactions in the Josephson regime. The energy spectrum of the system is studied by direct diagonalization and by solving the corresponding Bogoliubov-de Gennes equations. The atom-atom interactions are found to enhance the presence of strongly correlated macroscopic superpositions of semifluxons.
Superfluidity of a nonequilibrium Bose-Einstein condensate of polaritons
Wouters, Michiel; Savona, Vincenzo
2010-02-01
We study theoretically superfluidity in a driven-dissipative Bose gas out of thermal equilibrium, and discuss the relation with conventional superfluids. We show how the superfluid behavior is characterized by a dramatic increase in the lifetime of a quantized vortex and point out the influence of the spatial geometry of the condensate. We apply our study to a condensate of polaritons in a semiconductor microcavity, whose properties can be directly inferred from optical spectroscopy. We propose three different experimental schemes to measure the vorticity of the polariton condensate.
Topological Superfluid in a Fermi-Bose Mixture with a High Critical Temperature
NASA Astrophysics Data System (ADS)
Wu, Zhigang; Bruun, G. M.
2016-12-01
We show that a 2D spin-polarized Fermi gas immersed in a 3D Bose-Einstein condensate constitutes a very promising system for realizing a px+i py superfluid. The fermions attract each other via an induced interaction mediated by the bosons, and the resulting pairing is analyzed with retardation effects fully taken into account. This is further combined with Berezinskii-Kosterlitz-Thouless (BKT) theory to obtain reliable results for the superfluid critical temperature. We show that both the strength and the range of the induced interaction can be tuned experimentally, which can be used to make the critical temperature approach the maximum value allowed by general BKT theory. Moreover, this is achieved while keeping the Fermi-Bose interaction weak so that three-body losses are small. Our results show that realizing a topological superfluid with atomic Fermi-Bose mixtures is within experimental reach.
Probing the Bose glass-superfluid transition using quantum quenches of disorder
NASA Astrophysics Data System (ADS)
Meldgin, Carolyn; Ray, Ushnish; Russ, Philip; Chen, David; Ceperley, David M.; Demarco, Brian
2016-07-01
The disordered Bose-Hubbard model--a paradigm for strongly correlated and disordered bosonic systems--is central to our understanding of quantum phase transitions. Despite extensive theoretical work on the disordered Bose-Hubbard model, little is known about the impact of temperature, the dynamical behaviour of quantum phases, and how equilibrium is affected during quantum phase transitions. These issues are critically important to applications such as quantum annealing and electronics based on quantum phase transitions. Here, we use a quantum quench of disorder in an ultracold lattice gas to dynamically probe the superfluid-Bose glass quantum phase transition at non-zero temperature ( Fig. 1). By measuring excitations generated during the quench, we provide evidence for superfluid puddles in the Bose glass phase and produce a superfluid-Bose glass phase diagram consistent with completely constrained, finite temperature, and equilibrium quantum Monte Carlo simulations. The residual energy from the quench, which is an efficacy measure for optimization through quantum annealing, is unchanged for quench times spanning nearly a hundred tunnelling times.
Microfluidic serial dilution ladder.
Ahrar, Siavash; Hwang, Michelle; Duncan, Philip N; Hui, Elliot E
2014-01-07
Serial dilution is a fundamental procedure that is common to a large number of laboratory protocols. Automation of serial dilution is thus a valuable component for lab-on-a-chip systems. While a handful of different microfluidic strategies for serial dilution have been reported, approaches based on continuous flow mixing inherently consume larger amounts of sample volume and chip real estate. We employ valve-driven circulatory mixing to address these issues and also introduce a novel device structure to store each stage of the dilution process. The dilution strategy is based on sequentially mixing the rungs of a ladder structure. We demonstrate a 7-stage series of 1 : 1 dilutions with R(2) equal to 0.995 in an active device area of 1 cm(2).
Perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases.
Mohammadzadeh, Hosein; Adli, Fereshteh; Nouri, Sahereh
2016-12-01
We investigate perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases. We show that the intrinsic statistical interaction of nonextensive Bose (Fermi) gas is attractive (repulsive) similar to the extensive case but the value of thermodynamic curvature is changed by a nonextensive parameter. In contrary to the extensive ideal classical gas, the nonextensive one may be divided to two different regimes. According to the deviation parameter of the system to the nonextensive case, one can find a special value of fugacity, z^{*}, where the sign of thermodynamic curvature is changed. Therefore, we argue that the nonextensive parameter induces an attractive (repulsive) statistical interaction for z
Perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases
NASA Astrophysics Data System (ADS)
Mohammadzadeh, Hosein; Adli, Fereshteh; Nouri, Sahereh
2016-12-01
We investigate perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases. We show that the intrinsic statistical interaction of nonextensive Bose (Fermi) gas is attractive (repulsive) similar to the extensive case but the value of thermodynamic curvature is changed by a nonextensive parameter. In contrary to the extensive ideal classical gas, the nonextensive one may be divided to two different regimes. According to the deviation parameter of the system to the nonextensive case, one can find a special value of fugacity, z*, where the sign of thermodynamic curvature is changed. Therefore, we argue that the nonextensive parameter induces an attractive (repulsive) statistical interaction for z
Bose-Einstein Condensation in low dimensionality
NASA Astrophysics Data System (ADS)
Nho, Kwangsik; Landau, D. P.
2006-03-01
Using path integral Monte Carlo simulation methods[1], we have studied properties of Bose-Einstein Condensates harmonically trapped in low dimemsion. Each boson has a hard-sphere potential whose core radius equals its corresponding scattering length. We have tightly confined the motion of trapped particles in one or more direction by increasing the trap anisotropy in order to simulate lower dimensional atomic gases. We have investigated the effect of both the temperature and the dimemsionality on the energetics and structural properties such as the total energy, the density profile, and the superfluid fraction. Our results show that the physics of low dimensional bosonic systems is very different from that of their three dimensional counterparts[2]. The superfluid fraction for a quasi-2D boson gas decreases faster than that for both a quasi-1D system[3] and a true 3D system with increasing temperature. The superfluid fraction decreases gradually as the two-body interaction strength increases although it shows no noticable dependence for both a quasi-1D system and a true 3D system. [1] K. Nho and D. P. Landau, Phys. Rev. A. 70, 53614 (2004).[2] N. D. Mermin and H. Wagner, Phys. Rev. Lett. 22, 1133 (1966);1.5inP. C. Hohenberg, Phys. Rev. 158, 383 (1967).[3] K. Nho and D. Blume, Phys. Rev. Lett. 95, 193601 (2005).
NASA Astrophysics Data System (ADS)
Mori, Takanori; Sakurai, Takachika; Sato, Taiki; Shirakura, Akira; Suzuki, Tetsuya
2016-04-01
Hydrogenated amorphous carbon films with various thicknesses were synthesized by dielectric barrier discharge-based plasma deposition under atmospheric pressure diluted with nitrogen (N2) and helium (He) at various pulse frequencies. The C2H2/N2 film showed cauliflower-like-particles that grew bigger with the increase in film’s thickness. At 5 kHz, the film with a thickness of 2.7 µm and smooth surface was synthesized. On the other hand, the films synthesized from C2H2/He had a smooth surface and was densely packed with domed particles. The domed particles extended with the increase in the film thickness, enabling it to grow successfully to 37 µm with a smooth surface.
Isotope dilution mass spectrometry
NASA Astrophysics Data System (ADS)
Heumann, Klaus G.
1992-09-01
In the past isotope dilution mass spectrometry (IDMS) has usually been applied using the formation of positive thermal ions of metals. Especially in calibrating other analytical methods and for the certification of standard reference materials this type of IDMS became a routine method. Today, the progress in this field lies in the determination of ultra trace amounts of elements, e.g. of heavy metals in Antarctic ice and in aerosols in remote areas down to the sub-pg g-1 and sub-pg m-3 levels respectively, in the analysis of uranium and thorium at concentrations of a few pg g-1 in sputter targets for the production of micro- electronic devices or in the determination of sub-picogram amounts of230Th in corals for geochemical age determinations and of226Ra in rock samples. During the last few years negative thermal ionization IDMS has become a frequently used method. The determination of very small amounts of selenium and technetium as well as of other transition metals such as vanadium, chromium, molybdenum and tungsten are important examples in this field. Also the measurement of silicon in connection with a re-determination of Avogadro's number and osmium analyses for geological age determinations by the Re/Os method are of special interest. Inductively-coupled plasma mass spectrometry is increasingly being used for multi-element analyses by the isotope dilution technique. Determinations of heavy metals in samples of marine origin are representative examples for this type of multi-element analysis by IDMS. Gas chromatography-mass spectrometry systems have also been successfully applied after chelation of metals (for example Pt determination in clinical samples) or for the determination of volatile element species in the environment, e.g. dimethyl sulfide. However, IDMS--specially at low concentration levels in the environment--seems likely to be one of the most powerful analytical methods for speciation in the future. This has been shown, up to now, for species of
Dark-bright solitons in a superfluid Bose-Fermi mixture
NASA Astrophysics Data System (ADS)
Tylutki, Marek; Recati, Alessio; Dalfovo, Franco; Stringari, Sandro
2016-05-01
The recent experimental realisation of Bose-Fermi superfluid mixtures of dilute ultracold atomic gases has opened new perspectives in the study of quantum many-body systems. Depending on the values of the scattering lengths and the amount of bosons and fermions, a uniform Bose-Fermi mixture is predicted to exhibit a fully mixed phase, a fully separated phase or, in addition, a purely fermionic phase coexisting with a mixed phase. The occurrence of this intermediate configuration has interesting consequences when the system is nonuniform. In this work we theoretically investigate the case of solitonic solutions of coupled Bogoliubov-de Gennes and Gross-Pitaevskii equations for the fermionic and bosonic components, respectively. We show that, in the partially separated phase, a dark soliton in Fermi superfluid is accompanied by a broad bosonic component in the soliton, forming a dark-bright soliton which keeps full spatial coherence.
Recent developments in Bose-Einstein condensation
Kalman, G.
1997-09-22
This paper contains viewgraphs on developments on Bose-Einstein condensation. Some topics covered are: strongly coupled coulomb systems; standard response functions of the first and second kind; dynamical mean field theory; quasi localized charge approximation; and the main equations.
Forming a Bose-Einstein Condensate
2014-09-26
This sequence of false-color images shows the formation of a Bose-Einstein condensate in the Cold Atom Laboratory prototype at NASA Jet Propulsion Laboratory as the temperature gets progressively closer to absolute zero.
Atomic Phase Conjugation From a Bose Condensate
1996-07-01
Schrödinger equation that we use in this paper is not the Gross - Pitaevskii nonlinear Schrödinger equation familiar in the description of Bose conden...dipole- dipole interaction as local, so that our nonlinear Schrödinger equation is itself local, just like the Gross - Pitaevskii equation. However, the...dynamics of a Bose condensate is described by the Gross - Pitaevskii nonlinear Schrödinger equation [15], in which the nonlinearity results from short
Bose-Einstein condensates in rotating lattices.
Bhat, Rajiv; Holland, M J; Carr, L D
2006-02-17
Strongly interacting bosons in a two-dimensional rotating square lattice are investigated via a modified Bose-Hubbard Hamiltonian. Such a system corresponds to a rotating lattice potential imprinted on a trapped Bose-Einstein condensate. Second-order quantum phase transitions between states of different symmetries are observed at discrete rotation rates. For the square lattice we study, there are four possible ground-state symmetries.
Ultracold Gas Theory from the Top-Down and Bottom-Up
NASA Astrophysics Data System (ADS)
Colussi, Victor E.
Advances in trapping and cooling of ultracold gases over the last several decades have made it possible to test many formerly outstanding predictions from disparate branches of physics. This thesis touches on three historical problems that have found new life recently in the context of ultracold Bose gases of alkali atoms. The first problem revolves around an outstanding prediction from Boltzmann over a century and half old that the breathing mode of a isotropically trapped classical gas should oscillate indefinitely. I analyze recent experimental results, and attribute observed damping sources to trap imperfections. The second question is about the analogue of first and second sound modes from liquid helium in trapped dilute gases. I present the results of a joint theoretical/experimental investigation of the breathing mode of a finite temperature Bose-Einstein condensate (BEC), attributing a striking collapse revival behavior of the resultant oscillation to in-phase and out-of-phase normal modes of the thermal cloud and condensate. The third problem is that of the formation of Borromean ring-like three-body bound states, referred to as Efimov trimers, in strongly-interacting few-body systems. I extend the predicted spectrum of Efimov states into the realm of many degenerate internal levels, and investigate the difficult three-body elastic scattering problem. These questions are part of the broader theme of this thesis: How can our understanding of few-body physics in the ultracold limit be translated into statements about the bulk behavior of an ultracold gas? For weakly-interacting Bose gases, this translation is well-known: the many-body properties of the gas are well-described by the tracking just the one and two particle correlations. I analyze a generalization of this procedure to higher order correlations, the general connection between few-body physics and correlations in a dilute gas, and results for the emergence of Efimov physics in the magnetic phase
Van Uytfanghe, K; Stöckl, D; Kaufman, J M; Fiers, T; De Leenheer, A; Thienpont, L M
2005-03-01
The analytical validity of free testosterone (FTe) analog immunoassays is subject to much controversy. We revisited the validation of 4 analog assays and 1 FTe calculation procedure with a metrologically traceable reference measurement procedure (RMP) based on ultrafiltration and isotope dilution-mass spectrometry for direct measurement of Te in the ultrafiltrate. To this end, we performed split-sample measurements of 40 male sera. Deming regression showed that 3 of the immunoassays had moderate to good correlation (0.8474 < or = r < or = 0.9241) with the RMP; however, the slope was markedly below 1. The FTe calculation procedure was in good agreement with this result. The Sy/x values for all assays were higher than the combined imprecision values, which indicate their susceptibility to matrix-related effects. The study demonstrated substantial differences in analytical quality of FTe assays; however, the results suggested that after extending the validation with a larger variety of samples, recalibration of some analog assays might be worth further investigation.
NASA Astrophysics Data System (ADS)
Beswick, Benjamin T.; Hughes, Ifan G.; Gardiner, Simon A.; Astier, Hippolyte P. A. G.; Andersen, Mikkel F.; Daszuta, Boris
2016-12-01
Atom interferometers are a useful tool for precision measurements of fundamental physical phenomena, ranging from the local gravitational-field strength to the atomic fine-structure constant. In such experiments, it is desirable to implement a high-momentum-transfer "beam splitter," which may be achieved by inducing quantum resonance in a finite-temperature laser-driven atomic gas. We use Monte Carlo simulations to investigate these quantum resonances in the regime where the gas receives laser pulses of finite duration and derive an ɛ -classical model for the dynamics of the gas atoms which is capable of reproducing quantum resonant behavior for both zero-temperature and finite-temperature noninteracting gases. We show that this model agrees well with the fully quantum treatment of the system over a time scale set by the choice of experimental parameters. We also show that this model is capable of correctly treating the time-reversal mechanism necessary for implementing an interferometer with this physical configuration and that it explains an unexpected universality in the dynamics.
Takasuga, Takumi; Senthilkumar, Kurunthachalam; Matsumura, Tohru; Shiozaki, Ken; Sakai, Shin-ichi
2006-01-01
Special polychlorinated biphenyls (PCBs) standards (native and isotope labeled) were analyzed by isotope dilution method using HRGC-HRMS. Multiple analysis of special PCBs standards by three different laboratories produced the relative response factors (RRFs) and relative standard deviations (RSDs %) was in the average of 0.979 and 3.86, respectively. Additionally, inter-laboratory analysis of various forms of transformer oil revealed the PCBs concentrations were in the following order; PCBs fortified transformer oil (940-1300 ng/g)>PCB polluted transformer oil (490-680 ng/g)>chemically degraded-transformer oil (480-490 ng/g) and PCBs free oil (ND-17 ng/g). Chemical degradation resulted in an order of magnitude decrease in the PCB concentrations. Specifically, higher chlorinated PCBs degraded into lower chlorinated PCBs. Also, composition of PCBs have been determined in PCB formulations from Japan (Kanechlor), Germany (Clophen), USA (Aroclor), Russia (Sovol) and Poland (Chlorofen). Major PCBs (24-PCB congeners) contributed 54-67%, 55-68%, 16-69%, 71% and 72% in Kanechlor, Clophen, Aroclor, Sovol and Chlorofen, respectively to total PCBs. The homologue pattern of Kanechlor, Aroclor and Clophen in technical fromulation was similar (e.g., Kanechlor-300 resembled to those of Clophen A-30 and Aroclor-1242). Furthermore, congener-specific distributions of major PCBs/dioxin-like PCBs and toxic equivalency quantities (TEQ) were calculated. Based on our tentative assumption calculations, cumulative production of five different technical PCB formulations, WHO-TEQ emission was estimated to be approximately 16.05 tons.
Microcanonical fluctuations of the condensate in weakly interacting Bose gases
Idziaszek, Zbigniew
2005-05-15
We study fluctuations of the number of Bose condensed atoms in a weakly interacting homogeneous and trapped gases. For a homogeneous system we apply the particle-number-conserving formulation of the Bogoliubov theory and calculate the condensate fluctuations within the canonical and the microcanonical ensembles. We demonstrate that, at least in the low-temperature regime, predictions of the particle-number-conserving and traditional, nonconserving theory are identical, and lead to the anomalous scaling of fluctuations. Furthermore, the microcanonical fluctuations differ from the canonical ones by a quantity which scales normally in the number of particles, thus predictions of both ensembles are equivalent in the thermodynamic limit. We observe a similar behavior for a weakly interacting gas in a harmonic trap. This is in contrast to the trapped, ideal gas, where microcanonical and canonical fluctuations are different in the thermodynamic limit.
NASA Astrophysics Data System (ADS)
Kharga, Digvijay; Inotani, Daisuke; Hanai, Ryo; Ohashi, Yoji
2017-08-01
We theoretically investigate normal-state properties of a gas mixture of single-component bosons and fermions with a hetero-nuclear Feshbach resonance. Including strong hetero-pairing fluctuations associated with the Feshbach resonance, we calculate single-particle density of states, as well as the spectral weight at various interaction strengths. For this purpose, we employ an improved T-matrix approximation (TMA), where the bare Bose Green's function in the non-selfconsistent TMA self-energy is modified so as to satisfy the Hugenholtz-Pines relation at the Bose-Einstein condensation (BEC) temperature TBEC. In the unitary regime at TBEC, we show that hetero-pairing fluctuations couple Fermi atomic excitations with Fermi molecular excitations, as well as with Bose atomic excitations. Although a similar coupling phenomenon by pairing fluctuations is known to give a pseudo-gapped density of states in the unitary regime of a two-component Fermi gas, such a dip structure is found to not appear even in the unitary limit of a Bose-Fermi mixture. It only appears in the strong-coupling regime. Instead, a spectral peak along the molecular dispersion appears in the spectral weight. We also clarify how this coupling phenomenon is seen in the Bose channel. Since a hetero-nuclear Feshbach resonance, as well as the formation of Bose-Fermi molecules, have been realized, our results would be useful for the study of strong-coupling properties of this unique quantum gas.
Bogoliubov theory of acoustic Hawking radiation in Bose-Einstein condensates
Recati, A.; Pavloff, N.; Carusotto, I.
2009-10-15
We apply the microscopic Bogoliubov theory of dilute Bose-Einstein condensates to analyze quantum and thermal fluctuations in a flowing atomic condensate in the presence of a sonic horizon. For the simplest case of a step-like horizon, closed-form analytical expressions are found for the spectral distribution of the analog Hawking radiation and for the density correlation function. The peculiar long-distance density correlations that appear as a consequence of the Hawking emission features turns out to be reinforced by a finite initial temperature of the condensate. The analytical results are in good quantitative agreement with first principle numerical calculations.
Ground-state properties of trapped Bose-Fermi mixtures: Role of exchange correlation
Albus, Alexander P.; Wilkens, Martin; Illuminati, Fabrizio
2003-06-01
We introduce density-functional theory for inhomogeneous Bose-Fermi mixtures, derive the associated Kohn-Sham equations, and determine the exchange-correlation energy in local-density approximation. We solve numerically the Kohn-Sham system, and determine the boson and fermion density distributions and the ground-state energy of a trapped, dilute mixture beyond mean-field approximation. The importance of the corrections due to exchange correlation is discussed by a comparison with current experiments; in particular, we investigate the effect of the repulsive potential-energy contribution due to exchange correlation on the stability of the mixture against collapse.
A Ring with a Spin: Superfluidity in a toroidal Bose-Einstein condensate
NASA Astrophysics Data System (ADS)
Ramanathan, Anand Krishnan
2011-12-01
Superfluidity is a remarkable phenomenon. Superfluidity was initially characterized by flow without friction, first seen in liquid helium in 1938, and has been studied extensively since. Superfluidity is believed to be related to, but not identical to Bose-Einstein condensation, a statistical mechanical phenomena predicted by Albert Einstein in 1924 based on the statistics of Satyendra Nath Bose, where bosonic atoms make a phase transition to form a Bose-Einstein condensate (BEC), a gas which has macroscopic occupation of a single quantum state. Developments in laser cooling of neutral atoms and the subsequent realization of Bose-Einstein condensates in ultracold gases have opened a new window into the study of superfluidity and its relation to Bose-Einstein condensation. In our atomic sodium BEC experiment, we studied superfluidity and dissipationless flow in an all-optical toroidal trap, constructed using the combination of a horizontal "sheet"-like beam and vertical "ring"-like beam, which, like a circuit loop, allows flow around the ring. On inducing a single quantum of circulation in the condensate, the smoothness and uniformity of the toroidal BEC enabled the sustaining of a persistent current lasting 40 seconds, limited by the lifetime of the BEC due to background gas pressure. This success set the stage for further experiments studying superfluidity. In a first set of experiments, we studied the stability of the persistent current by inserting a barrier in the flow path of the ring. The superflow stopped abruptly at a barrier strength such that the local flow velocity at the barrier exceeded a critical velocity, which supported decay via the creation of a vortex-antivortex pair. Our precise control in inducing and arresting superflow in the BEC is a first step toward studying other aspects of superfluidity, such as the effect of temperature and dimensionality. This thesis discusses these experiments and also details partial-transfer absorption imaging, an
Domain walls and bubble droplets in immiscible binary Bose gases
NASA Astrophysics Data System (ADS)
Filatrella, G.; Malomed, Boris A.; Salerno, Mario
2014-10-01
The existence and stability of domain walls (DWs) and bubble-droplet (BD) states in binary mixtures of quasi-one-dimensional ultracold Bose gases with inter- and intraspecies repulsive interactions is considered. Previously, DWs were studied by means of coupled systems of Gross-Pitaevskii equations (GPEs) with cubic terms, which model immiscible binary Bose-Einstein condensates (BECs). We address immiscible BECs with two- and three-body repulsive interactions, as well as binary Tonks-Girardeau (TG) gases, using systems of GPEs with cubic and quintic nonlinearities for the binary BEC, and coupled nonlinear Schrödinger equations with quintic terms for the TG gases. Exact DW solutions are found for the symmetric BEC mixture, with equal intraspecies scattering lengths. Stable asymmetric DWs in the BEC mixtures with dissimilar interactions in the two components, as well as of symmetric and asymmetric DWs in the binary TG gas, are found by means of numerical and approximate analytical methods. In the BEC system, DWs can be easily put in motion by phase imprinting. Combining a DW and anti-DW on a ring, we construct BD states for both the BEC and TG models. These consist of a dark soliton in one component (the "bubble"), and a bright soliton (the "droplet") in the other. In the BEC system, these composite states are mobile, too.
Yegemova, Saltanat; Bakaikina, Nadezhda V; Kenessov, Bulat; Koziel, Jacek A; Nauryzbayev, Mikhail
2015-10-01
Environmental monitoring of Central Kazakhstan territories where heavy space booster rockets land requires fast, efficient, and inexpensive analytical methods. The goal of this study was to develop a method for quantitation of the most stable transformation product of rocket fuel, i.e., highly toxic unsymmetrical dimethylhydrazine - 1-methyl-1H-1,2,4-triazole (MTA) in soils using solid-phase microextraction (SPME) in combination with gas chromatography-mass spectrometry. Quantitation of organic compounds in soil samples by SPME is complicated by a matrix effect. Thus, an isotope dilution method was chosen using deuterated analyte (1-(trideuteromethyl)-1H-1,2,4-triazole; MTA-d3) for matrix effect control. The work included study of the matrix effect, optimization of a sample equilibration stage (time and temperature) after spiking MTA-d3 and validation of the developed method. Soils of different type and water content showed an order of magnitude difference in SPME effectiveness of the analyte. Isotope dilution minimized matrix effects. However, proper equilibration of MTA-d3 in soil was required. Complete MTA-d3 equilibration at temperatures below 40°C was not observed. Increase of temperature to 60°C and 80°C enhanced equilibration reaching theoretical MTA/MTA-d3 response ratios after 13 and 3h, respectively. Recoveries of MTA depended on concentrations of spiked MTA-d3 during method validation. Lowest spiked MTA-d3 concentration (0.24 mg kg(-1)) provided best MTA recoveries (91-121%). Addition of excess water to soil sample prior to SPME increased equilibration rate, but it also decreased method sensitivity. Method detection limit depended on soil type, water content, and was always below 1 mg kg(-1). The newly developed method is fully automated, and requires much lower time, labor and financial resources compared to known methods. Copyright © 2015 Elsevier B.V. All rights reserved.
Atomtronics with Ultracold Bose Gases
NASA Astrophysics Data System (ADS)
Ott, Herwig
Neutral atom systems can exhibit similar transport properties like solid state devices. For instance, a neutral atom current is induced by a difference in chemical potential very much in the same way as a voltage drives an electric current. Employing Bose-Einstein condensed atomic gases allows observing superfluid transport phenomena, thus drawing connections to superconductivity. With help of light fields, the atomic current can additionally be guided in engineered potential landscapes in which one can also incorporate tunneling junctions. Eventually, the different components and elements can be integrated in atomtronic circuits which shed light on fundamental transport properties of many-body quantum systems. In this talk, I will present two fundamental atomtronic devices. The first is the observation of negative differential conductivity, which occurs at a multimode tunneling junction for ultracold atoms. The second is the appearance of a DC Josephson current in a biased tunneling junction, which features bistable transport characteristics. I will discuss the prospects of these basic elements for more complex atomtronic circuits.
NASA Astrophysics Data System (ADS)
Yin, L.; Xia, J. S.; Sullivan, N. S.; Zapf, V. S.; Paduan-Filho, A.; Yu, R.; Roscilde, T.
2012-12-01
We report measurements of the AC susceptibility of a site-diluted quantum magnet Ni0.85Cd0.15Cl2-4SC(NH2)2 (15% Cd-doped dichloro-tetrakis-thiourea-Nickel, or Cd-DTN) down to 10 mK Below a crossover temperature Tcr ≍ 100 ~ 200mK, we find that the critical fields Hc for Bose-Einstein condensation obey the scaling relation |Hc(T)-Hc(0)| ~ Tα, with a novel and universal scaling exponent α ≍ 0.9, which is in agreement with numerical results from a theoretical model. Our findings provide strong evidence of the existence of a Bose glass phase in Cd-DTN, and they display a quantitative signature of the transition between a Bose glass and a Bose Einstein condensate.
Bose polarons: Dynamical decay and RF signatures
NASA Astrophysics Data System (ADS)
Corson, John; Bohn, John
2016-05-01
Interactions of a single impurity with a quantum many-body environment are known to alter the character of the impurity, thereby forming a ``quasiparticle''. The condensed matter tradition often identifies quasiparticles as poles of a Green function in the complex plane, a notion whose sophistication sometimes obscures the underlying physics. The problem of a single quantum impurity in a Bose condensate, or Bose polaron, is an illustrative example where the meaning of the impurity Green function, and hence the quasiparticle itself, becomes especially transparent. Using direct diagonalization in a truncated Hilbert space, we examine the dynamical evolution and quasiparticle decay of the repulsive Bose polaron. This approach also allows us to simulate RF spectroscopy across a Feshbach resonance and outside the linear regime, as well as account for motional and thermal effects in a harmonic trap.
A Simple Model of Bose-Einstein Condensation of Interacting Particles
NASA Astrophysics Data System (ADS)
Poluektov, Yu. M.
2017-03-01
A simple model of Bose-Einstein condensation of interacting particles is proposed. It is shown that in the condensate state the dependence of thermodynamic quantities on the interaction constant does not allow an expansion in powers of the coupling constant. Therefore, it is impossible to pass to the Einstein model of condensation in an ideal Bose gas by means of a limiting passage, setting the interaction constant to zero. The account for the interaction between particles eliminates difficulties in the description of condensation available in the model of an ideal gas, which are connected with the fulfillment of thermodynamic relations and an infinite value of the particle number fluctuation in the condensate phase.
Quantum phase transitions of atom-molecule Bose mixtures in a double-well potential.
Relaño, A; Dukelsky, J; Pérez-Fernández, P; Arias, J M
2014-10-01
The ground state and spectral properties of Bose gases in double-well potentials are studied in two different scenarios: (i) an interacting atomic Bose gas, and (ii) a mixture of an atomic gas interacting with diatomic molecules. A ground state second-order quantum phase transition is observed in both scenarios. For large attractive values of the atom-atom interaction, the ground state is degenerate. For repulsive and small attractive interaction, the ground state is not degenerate and is well approximated by a boson coherent state. Both systems depict an excited state quantum phase transition. In both cases, a critical energy separates a region in which all the energy levels are degenerate in pairs, from another region in which there are no degeneracies. For the atomic system, the critical point displays a singularity in the density of states, whereas this behavior is largely smoothed for the mixed atom-molecule system.
Bose-Einstein condensation in low dimensional systems with deformed bosons
NASA Astrophysics Data System (ADS)
Algin, Abdullah; Olkun, Ali
2017-08-01
We study the low and high temperature thermostatistical properties of a deformed boson gas constructed by the bosonic intermediate-statistics particles confined in low spatial dimensions. Many of the deformed thermodynamical functions of the system such as internal energy and entropy are investigated by means of some elements of the Fibonacci calculus. Particular emphasis is given to a careful analysis on low dimensional systems of such deformed bosons, and the conditions under which the Bose-Einstein condensation would occur in such systems are discussed. We show that low dimensional systems with deformed bosons exhibit the Bose-Einstein condensation for values of the model deformation parameters (p , q) greater than one. We also study possible anyonic behavior of the model for high temperatures. The results obtained in this work reveal that the present deformed boson gas model can be used for modeling nonlinear behavior of systems with quasiparticles encountered in several areas of research particularly in quantum science.
Microfluidic serial dilution circuit.
Paegel, Brian M; Grover, William H; Skelley, Alison M; Mathies, Richard A; Joyce, Gerald F
2006-11-01
In vitro evolution of RNA molecules requires a method for executing many consecutive serial dilutions. To solve this problem, a microfluidic circuit has been fabricated in a three-layer glass-PDMS-glass device. The 400-nL serial dilution circuit contains five integrated membrane valves: three two-way valves arranged in a loop to drive cyclic mixing of the diluent and carryover, and two bus valves to control fluidic access to the circuit through input and output channels. By varying the valve placement in the circuit, carryover fractions from 0.04 to 0.2 were obtained. Each dilution process, which is composed of a diluent flush cycle followed by a mixing cycle, is carried out with no pipeting, and a sample volume of 400 nL is sufficient for conducting an arbitrary number of serial dilutions. Mixing is precisely controlled by changing the cyclic pumping rate, with a minimum mixing time of 22 s. This microfluidic circuit is generally applicable for integrating automated serial dilution and sample preparation in almost any microfluidic architecture.
Nakahara, Y; Takahashi, K; Shimamine, M; Takeda, Y
1991-01-01
Determination of methamphetamine and amphetamine in hair was performed by gas chromatography/mass spectrometry using stable isotope-labeled internal standards, 2-methylamino-1-phenylpropane-2,3,3,3-d4 and 2-amino-1-phenylpropane-2,3,3,3-d4. Extraction of hair with methanol/5M hydrochloric acid (20:1) using ultrasonication was chosen as the standard method. The calibration curves for amphetamines in the hair were linear from 1 to 100 ng/mg (r greater than 0.99). The detection limit was 0.5 ng/mg at the 95% confidence level. The coefficients of variation (CV) (n = 8) of analysis using the spiked hair with methamphetamine were from 0.7 to 6%. The CV (n = 8) of analysis of the methamphetamine abuser's hair was 17.5%. Sectional analysis of monkey and human hair after methamphetamine ingestion suggested a good correlation between the duration of drug use and drug distribution in the hair.
Bose-Einstein condensation. Twenty years after
Bagnato, V. S.; Frantzeskakis, D. J.; Kevrekidis, P. G.; Malomed, B. A.; Mihalache, D.
2015-02-23
The aim of this introductory article is two-fold. First, we aim to offer a general introduction to the theme of Bose-Einstein condensates, and briefly discuss the evolution of a number of relevant research directions during the last two decades. Second, we introduce and present the articles that appear in this Special Volume of Romanian Reports in Physics celebrating the conclusion of the second decade since the experimental creation of Bose-Einstein condensation in ultracold gases of alkali-metal atoms.