Science.gov

Sample records for ideal fermi gas

  1. Insulating behavior of a trapped ideal Fermi gas.

    PubMed

    Pezzè, L; Pitaevskii, L; Smerzi, A; Stringari, S; Modugno, G; de Mirandes, E; Ferlaino, F; Ott, H; Roati, G; Inguscio, M

    2004-09-17

    We investigate theoretically and experimentally the center-of-mass motion of an ideal Fermi gas in a combined periodic and harmonic potential. We find a crossover from a conducting to an insulating regime as the Fermi energy moves from the first Bloch band into the band gap of the lattice. The conducting regime is characterized by an oscillation of the cloud about the potential minimum, while in the insulating case the center of mass remains on one side of the potential.

  2. Born-Kothari condensation in an ideal Fermi gas

    NASA Astrophysics Data System (ADS)

    Ghosh, Arnab; Ray, Deb Shankar

    2017-02-01

    ``Condensation" in Fermi-Dirac statistics [D. S. Kothari and B. Nath, Nature 151, 420 (1943), 10.1038/151420a0], which appears as a natural consequence of Born's reciprocity principle [M. Born, Proc. R. Soc. London A 165, 291 (1938), 10.1098/rspa.1938.0060; M. Born, Nature 141, 328 (1938), 10.1038/141327a0], is examined from a theoretical perspective. Since fermions obey the Pauli exclusion principle, it is conceptually different from Bose-Einstein condensation, which permits macroscopic occupation of bosons at the single-particle level below a critical temperature. Yet, in accordance with the Cahill and Glauber [Phys. Rev. A 59, 1538 (1999)], 10.1103/PhysRevA.59.1538 formulation for fermionic fields, and in close kinship to bosonic fields, we have shown that in analogy to Bose-Einstein condensation, it is possible to associate an intrinsic notion of symmetry breaking and the thermodynamic "order parameter" to characterize the foregoing hitherto unexplored phenomenon in an ideal Fermi-Dirac gas as condensation-like coherence within fermions.

  3. Isobaric expansion coefficient and isothermal compressibility for a finite-size ideal Fermi gas system

    NASA Astrophysics Data System (ADS)

    Su, Guozhen; Chen, Liwei; Chen, Jincan

    2014-06-01

    Due to quantum size effects (QSEs), the isobaric thermal expansion coefficient and isothermal compressibility well defined for macroscopic systems are invalid for finite-size systems. The two parameters are redefined and calculated for a finite-size ideal Fermi gas confined in a rectangular container. It is found that the isobaric thermal expansion coefficient and isothermal compressibility are generally anisotropic, i.e., they are generally different in different directions. Moreover, it is found the thermal expansion coefficient may be negative in some directions under the condition that the pressures in all directions are kept constant.

  4. A note on the Fermi energy of an ideal Fermi gas trapped under a generic power law potential in d-dimension

    NASA Astrophysics Data System (ADS)

    Mehedi Faruk, Mir

    2015-09-01

    The average energy per fermion in the case of a Fermi gas with any kinematic characteristic, trapped under the most general power law potential in d-dimension has been calculated at zero temperature. In a previous paper (Acharyya M 2010 Eur. J Phys. 31 L89) it was shown, in the case of a free ideal Fermi gas, as the dimension increases the average energy approaches the Fermi energy and in infinite dimension the average energy becomes equal to the Fermi energy at T = 0. In this letter it is shown that, for a trapped system at finite dimension the average energy depends on a power law exponent, but as the dimension tends to infinity the average energy coincides with the Fermi energy for any power law exponent. The result obtained in this manuscript is more general, as we can describe the free system as well as any trapped system with an appropriate choice of power law exponent, and is true for any kinematic parameter.

  5. Distribution of Zeros and the Equation of State. III ---Cluster Series, the Ideal Fermi-Dirac Gas and Other Problems---

    NASA Astrophysics Data System (ADS)

    Ikeda, K.

    1982-08-01

    The radius of convergence of the cluster series (expressing the equation of state) is discussed in connection with the distribution of zeros of the grand partition function on the complex z(=activity) plane, by giving various examples of circular distribution. Anomalous phase transitions and phase transitions of third order are considered by showing some examples of circular distribution of zeros. For the ideal Fermi-Dirac gas, the distribution function of zeros, lying on the part of the negative real axis from -λ-3 to -∞ [where λ=h(2 π mkT)-1/ 2], is calculated , and the function-theoretical structure of the equation of state is investigated. The distribution of zeros for this gas is compared with that for Tonks' gas (having purely repulsive interparticle forces). The two-dimensional and one-dimensional Fermi-Dirac gases are dealt with from the point of view of the distribution of zeros.

  6. Self-energy of an impurity in an ideal Fermi gas to second order in the interaction strength

    NASA Astrophysics Data System (ADS)

    Trefzger, Christian; Castin, Yvan

    2014-09-01

    We study in three dimensions the problem of a spatially homogeneous zero-temperature ideal Fermi gas of spin-polarized particles of mass m perturbed by the presence of a single distinguishable impurity of mass M. The interaction between the impurity and the fermions involves only the partial s wave through the scattering length a and has negligible range b compared to the inverse Fermi wave number 1/kF of the gas. Through the interactions with the Fermi gas the impurity gives birth to a quasiparticle, which will be here a Fermi polaron (or more precisely a monomeron). We consider the general case of an impurity moving with wave vector K ≠0: Then the quasiparticle acquires a finite lifetime in its initial momentum channel because it can radiate particle-hole pairs in the Fermi sea. A description of the system using a variational approach, based on a finite number of particle-hole excitations of the Fermi sea, then becomes inappropriate around K =0. We rely thus upon perturbation theory, where the small and negative parameter kFa→0- excludes any branches other than the monomeronic one in the ground state (as, e.g., the dimeronic one), and allows us a systematic study of the system. We calculate the impurity self-energy Σ(2)(K,ω) up to second order included in a. Remarkably, we obtain an analytical explicit expression for Σ(2)(K,ω), allowing us to study its derivatives in the plane (K,ω). These present interesting singularities, which in general appear in the third-order derivatives ∂3Σ(2)(K,ω). In the special case of equal masses, M =m, singularities appear already in the physically more accessible second-order derivatives ∂2Σ(2)(K,ω); using a self-consistent heuristic approach based on Σ(2) we then regularize the divergence of the second-order derivative ∂K2ΔE(K) of the complex energy of the quasiparticle found in Trefzger and Castin [Europhys. Lett. 104, 50005 (2013), 10.1209/0295-5075/104/50005] at K =kF, and we predict an interesting scaling

  7. Optimum performance analysis of an irreversible quantum cryogenic refrigeration cycle working with an ideal Bose or Fermi gas

    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.

  8. Energy Fluctuation of Ideal Fermi Gas Trapped under Generic Power Law Potential U=\\sum_{i=1}^{d} c_i\\vert x_{i}/a_{i}\\vert^{n_{i} } in d Dimensions

    NASA Astrophysics Data System (ADS)

    Mehedi Faruk, Mir; Muktadir Rahman, Md.; Debnath, Dwaipayan; Sakhawat Hossain Himel, Md.

    2016-04-01

    Energy fluctuation of ideal Fermi gas trapped under generic power law potential U=\\sumi=1d ci \\vertxi/ai \\vert n_i has been calculated in arbitrary dimensions. Energy fluctuation is scrutinized further in the degenerate limit μ ≫ KBT with the help of Sommerfeld expansion. The dependence of energy fluctuation on dimensionality and power law potential is studied in detail. Most importantly our general result can not only exactly reproduce the recently published result regarding free and harmonically trapped ideal Fermi gas in d = 3 but also can describe the outcome for any power law potential in arbitrary dimension.

  9. Suppression of Density Fluctuations in a Quantum Degenerate Fermi Gas

    SciTech Connect

    Sanner, Christian; Su, Edward J.; Keshet, Aviv; Gommers, Ralf; Shin, Yong-il; Huang Wujie; Ketterle, Wolfgang

    2010-07-23

    We study density profiles of an ideal Fermi gas and observe Pauli suppression of density fluctuations (atom shot noise) for cold clouds deep in the quantum degenerate regime. Strong suppression is observed for probe volumes containing more than 10 000 atoms. Measuring the level of suppression provides sensitive thermometry at low temperatures. After this method of sensitive noise measurements has been validated with an ideal Fermi gas, it can now be applied to characterize phase transitions in strongly correlated many-body systems.

  10. Perturbative thermodynamic geometry of nonextensive ideal classical, Bose, and Fermi gases.

    PubMed

    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 zz^{*}) for an ideal classical gas. Also, according to the singular point of thermodynamic curvature, we consider the condensation of nonextensive Boson gas.

  11. 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 z* ) for an ideal classical gas. Also, according to the singular point of thermodynamic curvature, we consider the condensation of nonextensive Boson gas.

  12. Fermi Gas Microscope

    NASA Astrophysics Data System (ADS)

    Setiawan, Widagdo

    Recent advances in using microscopes in ultracold atom experiment have allowed experimenters for the first time to directly observe and manipulate individual atoms in individual lattice sites. This technique enhances our capability to simulate strongly correlated systems such as Mott insulator and high temperature superconductivity. Currently, all ultracold atom experiments with high resolution imaging capability use bosonic atoms. In this thesis, I present our progress towards creating the fermionic version of the microscope experiment which is more suitable for simulating real condensed matter systems. Lithium is ideal due to the existence of both fermionic and bosonic isotopes, its light mass, which means faster experiment time scales that suppresses many sources of technical noise, and also due to the existence of a broad Feshbach resonance, which can be used to tune the inter-particle interaction strength over a wide range from attractive, non-interacting, and repulsive interactions. A high numerical aperture objective will be used to image and manipulate the atoms with single lattice site resolution. This setup should allow us to implement the Hubbard hamiltonian which could describe interesting quantum phases such as antiferromagnetism, d-wave superfluidity, and high temperature superconductivity. I will also discuss the feasibility of the Raman sideband cooling method for cooling the atoms during the imaging process. We have also developed a new electronic control system to control the sequence of the experiment. This electronic system is very scalable in order to keep up with the increasing complexity of atomic physics experiments. Furthermore, the system is also designed to be more precise in order to keep up with the faster time scale of lithium experiment.

  13. Massive Fermi gas in the expanding universe

    NASA Astrophysics Data System (ADS)

    Trautner, Andreas

    2017-03-01

    The behavior of a decoupled ideal Fermi gas in a homogeneously expanding three-dimensional volume is investigated, starting from an equilibrium spectrum. In case the gas is massless and/or completely degenerate, the spectrum of the gas can be described by an effective temperature and/or an effective chemical potential, both of which scale down with the volume expansion. In contrast, the spectrum of a decoupled massive and non-degenerate gas can only be described by an effective temperature if there are strong enough self-interactions such as to maintain an equilibrium distribution. Assuming perpetual equilibration, we study a decoupled gas which is relativistic at decoupling and then is red-shifted until it becomes non-relativistic. We find expressions for the effective temperature and effective chemical potential which allow us to calculate the final spectrum for arbitrary initial conditions. This calculation is enabled by a new expansion of the Fermi-Dirac integral, which is for our purpose superior to the well-known Sommerfeld expansion. We also compute the behavior of the phase space density under expansion and compare it to the case of real temperature and real chemical potential. Using our results for the degenerate case, we also obtain the mean relic velocity of the recently proposed non-thermal cosmic neutrino background.

  14. Temperature and the Ideal Gas

    ERIC Educational Resources Information Center

    Daisley, R. E.

    1973-01-01

    Presents some organized ideas in thermodynamics which are suitable for use with high school (GCE A level or ONC) students. Emphases are placed upon macroscopic observations and intimate connection of the modern definition of temperature with the concept of ideal gas. (CC)

  15. Temperature and the Ideal Gas

    ERIC Educational Resources Information Center

    Daisley, R. E.

    1973-01-01

    Presents some organized ideas in thermodynamics which are suitable for use with high school (GCE A level or ONC) students. Emphases are placed upon macroscopic observations and intimate connection of the modern definition of temperature with the concept of ideal gas. (CC)

  16. The Equation of State of a Strongly Interacting Fermi Gas

    NASA Astrophysics Data System (ADS)

    Navon, Nir; Nascimbène, Sylvain; Jiang, Kaijun; Chevy, Frédéric; Salomon, Christophe

    2010-03-01

    In this talk, we will present recent experimental work on the thermodynamics of strongly interacting Fermi gases. We have developed a general method to probe with high precision the Equation of State (EoS) of locally homogeneous ultracold gases [1]. This allows stringent tests of recent many-body theories. First, we focus on the finite-temperature EoS of the unpolarized unitary gas. Precise thermometry is provided by adding to the Fermi gas of ^6Li a trace of bosonic ^7Li. We show that the low-temperature properties of the strongly interacting normal phase are well described by Fermi liquid theory and we localize the superfluid transition. Second, we address the zero-temperature EoS of the spin-polarized system. Surprisingly, despite strong interactions, the polarized phase behaves as a mixture of two ideal gases: a Fermi gas of majority atoms and a non-interacting gas of dressed quasi-particles, the Fermi polarons. Finally, we will report on work in progress on the extension of our study to the BEC-BCS crossover [2]. [4pt] [1] S. Nascimbene and N. Navon, K. Jiang, F. Chevy, C. Salomon, arXiv:0911.0747, Nature (in press, 2010) [0pt] [2] N. Navon and S. Nascimbene, F. Chevy, C. Salomon, in preparation (2010)

  17. Exploring the thermodynamics of a universal Fermi gas.

    PubMed

    Nascimbène, S; Navon, N; Jiang, K J; Chevy, F; Salomon, C

    2010-02-25

    One of the greatest challenges in modern physics is to understand the behaviour of an ensemble of strongly interacting particles. A class of quantum many-body systems (such as neutron star matter and cold Fermi gases) share the same universal thermodynamic properties when interactions reach the maximum effective value allowed by quantum mechanics, the so-called unitary limit. This makes it possible in principle to simulate some astrophysical phenomena inside the highly controlled environment of an atomic physics laboratory. Previous work on the thermodynamics of a two-component Fermi gas led to thermodynamic quantities averaged over the trap, making comparisons with many-body theories developed for uniform gases difficult. Here we develop a general experimental method that yields the equation of state of a uniform gas, as well as enabling a detailed comparison with existing theories. The precision of our equation of state leads to new physical insights into the unitary gas. For the unpolarized gas, we show that the low-temperature thermodynamics of the strongly interacting normal phase is well described by Fermi liquid theory, and we localize the superfluid transition. For a spin-polarized system, our equation of state at zero temperature has a 2 per cent accuracy and extends work on the phase diagram to a new regime of precision. We show in particular that, despite strong interactions, the normal phase behaves as a mixture of two ideal gases: a Fermi gas of bare majority atoms and a non-interacting gas of dressed quasi-particles, the fermionic polarons.

  18. Adiabatic swimming in an ideal quantum gas.

    PubMed

    Avron, J E; Gutkin, B; Oaknin, D H

    2006-04-07

    Interference effects are important for swimming of mesoscopic systems that are small relative to the coherence length of the surrounding quantum medium. Swimming is geometric for slow swimmers and the distance covered in each stroke is determined, explicitly, in terms of the on-shell scattering matrix. Remarkably, for a one-dimensional Fermi gas at zero temperature we find that slow swimming is topological: the swimming distance covered in one stroke is quantized in half integer multiples of the Fermi wavelength. In addition, a careful choice of the swimming stroke can eliminate dissipation.

  19. Probing the Contact Locally in a Trapped Unitary Fermi Gas

    NASA Astrophysics Data System (ADS)

    Paudel, Rabin; Sagi, Yoav; Drake, Tara; Jin, Deborah

    2013-03-01

    The inherent density inhomogeneity of a trapped gas can complicate interpretation of experiments and can wash out sharp features. This is especially important for a Fermi gas, where interaction effects as well as the local Fermi energy, or Fermi momentum, depend on the density. We report on experiments that use optical pumping with shaped light beams to spatially select the center part of a trapped gas for probing. This technique is compatible with momentum resolved measurements. For a weakly interacting Fermi gas of 40K atoms, we present measurements of the momentum distribution that reveal for the first time a sharp Fermi surface. We then apply this technique to a strongly interacting Fermi gas at the Feshbach resonance, where we measured the temperature dependence of the Tan's contact locally in the trapped gas.

  20. Ideal Gas Laws: Experiments for General Chemistry

    ERIC Educational Resources Information Center

    Deal, Walter J.

    1975-01-01

    Describes a series of experiments designed to verify the various relationships implicit in the ideal gas equation and shows that the success of the Graham's law effusion experiments can be explained by elementary hydrodynamics. (GS)

  1. Ideal Gas Laws: Experiments for General Chemistry

    ERIC Educational Resources Information Center

    Deal, Walter J.

    1975-01-01

    Describes a series of experiments designed to verify the various relationships implicit in the ideal gas equation and shows that the success of the Graham's law effusion experiments can be explained by elementary hydrodynamics. (GS)

  2. Dark solitons in a superfluid Fermi gas

    SciTech Connect

    Antezza, Mauro; Dalfovo, Franco; Stringari, Sandro; Pitaevskii, Lev P.

    2007-10-15

    We investigate the behavior of dark solitons in a superfluid Fermi gas along the BCS-BEC crossover by solving the Bogoliubov-de Gennes equations and looking for real and odd solutions for the order parameter. We show that in the resonance unitary region, where the scattering length is large, the density profile of the soliton has a deep minimum, differently from what happens in the BCS regime. The superfluid gap is found to be significantly quenched by the presence of the soliton due to the occurrence of Andreev fermionic bound states localized near the nodal plane of the order parameter.

  3. Orientifolding of the ABJ Fermi gas

    NASA Astrophysics Data System (ADS)

    Okuyama, Kazumi

    2016-03-01

    The grand partition functions of ABJ theory can be factorized into even and odd parts under the reflection of fermion coordinate in the Fermi gas approach. In some cases, the even/odd part of ABJ grand partition function is equal to that of {N}=5O(n)× USp({n}^') theory, hence it is natural to think of the even/odd projection of grand partition function as an orientifolding of ABJ Fermi gas system. By a systematic WKB analysis, we determine the coefficients in the perturbative part of grand potential of such orientifold ABJ theory. We also find the exact form of the first few "half-instanton" corrections coming from the twisted sector of the reflection of fermion coordinate. For the Chern-Simons level k = 2 ,4 ,8 we find closed form expressions of the grand partition functions of orientifold ABJ theory, and for k = 2 , 4 we prove the functional relations among the grand partition functions conjectured in arXiv:1410.7658.

  4. Seiberg-Witten theory as a Fermi gas

    NASA Astrophysics Data System (ADS)

    Bonelli, Giulio; Grassi, Alba; Tanzini, Alessandro

    2017-01-01

    We explore a new connection between Seiberg-Witten theory and quantum statistical systems by relating the dual partition function of SU(2) Super Yang-Mills theory in a self-dual Ω background to the spectral determinant of an ideal Fermi gas. We show that the spectrum of this gas is encoded in the zeroes of the Painlevé III_3 τ function. In addition, we find that the Nekrasov partition function on this background can be expressed as an O(2) matrix model. Our construction arises as a four-dimensional limit of a recently proposed conjecture relating topological strings and spectral theory. In this limit, we provide a mathematical proof of the conjecture for the local P^1 × P^1 geometry.

  5. Derivation of the Ideal Gas Law

    ERIC Educational Resources Information Center

    Laugier, Alexander; Garai, Jozsef

    2007-01-01

    Undergraduate and graduate physics and chemistry books usually state that combining the gas laws results in the ideal gas law. Leaving the derivation to the students implies that this should be a simple task, most likely a substitution. Boyle's law, Charles's law, and the Avogadro's principle are given under certain conditions; therefore, direct…

  6. Derivation of the Ideal Gas Law

    ERIC Educational Resources Information Center

    Laugier, Alexander; Garai, Jozsef

    2007-01-01

    Undergraduate and graduate physics and chemistry books usually state that combining the gas laws results in the ideal gas law. Leaving the derivation to the students implies that this should be a simple task, most likely a substitution. Boyle's law, Charles's law, and the Avogadro's principle are given under certain conditions; therefore, direct…

  7. Virial expansion for a strongly correlated Fermi gas with imbalanced spin populations

    NASA Astrophysics Data System (ADS)

    Liu, Xia-Ji; Hu, Hui

    2010-10-01

    Quantum virial expansion provides an ideal tool to investigate the high-temperature properties of a strongly correlated Fermi gas. Here, we construct the virial expansion in the presence of spin-population imbalance. Up to the third order, we calculate the high-temperature free energy of a unitary Fermi gas as a function of spin imbalance, with infinitely large attractive or repulsive interactions. In the latter repulsive case, we show that there is no itinerant ferromagnetism when quantum virial expansion is applicable. We therefore estimate an upper bound for the ferromagnetic transition temperature Tc. For a harmonically trapped Fermi gas at unitarity, we find that (Tc)upperFermi temperature at the center of the trap. Our result for the high-temperature equations of state may confront future high-precision thermodynamic measurements.

  8. How Is the Ideal Gas Law Explanatory?

    ERIC Educational Resources Information Center

    Woody, Andrea I.

    2013-01-01

    Using the ideal gas law as a comparative example, this essay reviews contemporary research in philosophy of science concerning scientific explanation. It outlines the inferential, causal, unification, and erotetic conceptions of explanation and discusses an alternative project, the functional perspective. In each case, the aim is to highlight…

  9. How Is the Ideal Gas Law Explanatory?

    ERIC Educational Resources Information Center

    Woody, Andrea I.

    2013-01-01

    Using the ideal gas law as a comparative example, this essay reviews contemporary research in philosophy of science concerning scientific explanation. It outlines the inferential, causal, unification, and erotetic conceptions of explanation and discusses an alternative project, the functional perspective. In each case, the aim is to highlight…

  10. Performance of a multilevel quantum heat engine of an ideal N-particle Fermi system.

    PubMed

    Wang, Rui; Wang, Jianhui; He, Jizhou; Ma, Yongli

    2012-08-01

    We generalize the quantum heat engine (QHE) model which was first proposed by Bender et al. [J. Phys. A 33, 4427 (2000)] to the case in which an ideal Fermi gas with an arbitrary number N of particles in a box trap is used as the working substance. Besides two quantum adiabatic processes, the engine model contains two isoenergetic processes, during which the particles are coupled to energy baths at a high constant energy E(h) and a low constant energy E(c), respectively. Directly employing the finite-time thermodynamics, we find that the power output is enhanced by increasing particle number N (or decreasing minimum trap size L(A)) for given L(A) (or N), without reduction in the efficiency. By use of global optimization, the efficiency at possible maximum power output (EPMP) is found to be universal and independent of any parameter contained in the engine model. For an engine model with any particle-number N, the efficiency at maximum power output (EMP) can be determined under the condition that it should be closest to the EPMP. Moreover, we extend the heat engine to a more general multilevel engine model with an arbitrary 1D power-law potential. Comparison between our engine model and the Carnot cycle shows that, under the same conditions, the efficiency η = 1 - E(c)/E(h) of the engine cycle is bounded from above the Carnot value η(c) =1 - T(c)/T(h).

  11. Performance of a multilevel quantum heat engine of an ideal N-particle Fermi system

    NASA Astrophysics Data System (ADS)

    Wang, Rui; Wang, Jianhui; He, Jizhou; Ma, Yongli

    2012-08-01

    We generalize the quantum heat engine (QHE) model which was first proposed by Bender [J. Phys. A10.1088/0305-4470/33/24/302 33, 4427 (2000)] to the case in which an ideal Fermi gas with an arbitrary number N of particles in a box trap is used as the working substance. Besides two quantum adiabatic processes, the engine model contains two isoenergetic processes, during which the particles are coupled to energy baths at a high constant energy Eh and a low constant energy Ec, respectively. Directly employing the finite-time thermodynamics, we find that the power output is enhanced by increasing particle number N (or decreasing minimum trap size LA) for given LA (or N), without reduction in the efficiency. By use of global optimization, the efficiency at possible maximum power output (EPMP) is found to be universal and independent of any parameter contained in the engine model. For an engine model with any particle-number N, the efficiency at maximum power output (EMP) can be determined under the condition that it should be closest to the EPMP. Moreover, we extend the heat engine to a more general multilevel engine model with an arbitrary 1D power-law potential. Comparison between our engine model and the Carnot cycle shows that, under the same conditions, the efficiency η=1-(Ec)/(Eh) of the engine cycle is bounded from above the Carnot value ηc=1-(Tc)/(Th).

  12. Degenerate Fermi gas perturbations at standard background cosmology

    SciTech Connect

    Bernardini, A.E.; Perico, E.L.D. E-mail: elduarte@ifi.unicamp.br

    2011-01-01

    The hypothesis of a tiny fraction of the cosmic inventory evolving cosmologically as a degenerate Fermi gas test fluid at some dominant cosmological background is investigated. Our analytical results allow for performing preliminary computations to the evolution of perturbations for relativistic and non-relativistic test fluids. The density fluctuation, δ, the fluid velocity divergence, θ, and an explicit expression for the dynamics of the shear stress, σ, are obtained for a degenerate Fermi gas in the background regime of radiation. Extensions to the dominance of matter and to the ΛCDM cosmological background are also investigated and lessons concerning the formation of large structures of degenerate Fermi gas are depicted.

  13. Structural arrest in an ideal gas.

    PubMed

    van Ketel, Willem; Das, Chinmay; Frenkel, Daan

    2005-04-08

    We report a molecular dynamics study of a simple model system that has the static properties of an ideal gas, yet exhibits nontrivial "glassy" dynamics behavior at high densities. The constituent molecules of this system are constructs of three infinitely thin hard rods of length L, rigidly joined at their midpoints. The crosses have random but fixed orientation. The static properties of this system are those of an ideal gas, and its collision frequency can be computed analytically. For number densities NL(3)/V>1, the single-particle diffusivity goes to zero. As the system is completely structureless, standard mode-coupling theory cannot describe the observed structural arrest. Nevertheless, the system exhibits many dynamical features that appear to be mode-coupling-like. All high-density incoherent intermediate scattering functions collapse onto master curves that depend only on the wave vector.

  14. Umklapp superradiance with a collisionless quantum degenerate Fermi gas.

    PubMed

    Piazza, Francesco; Strack, Philipp

    2014-04-11

    The quantum dynamics of the electromagnetic light mode of an optical cavity filled with a coherently driven Fermi gas of ultracold atoms strongly depends on the geometry of the Fermi surface. Superradiant light generation and self-organization of the atoms can be achieved at low pumping threshold due to resonant atom-photon umklapp processes, where the fermions are scattered from one side of the Fermi surface to the other by exchanging photon momenta. The cavity spectrum exhibits sidebands that, despite strong atom-light coupling and cavity decay, retain narrow linewidth, due to absorptionless transparency windows outside the atomic particle-hole continuum and the suppression of broadening and thermal fluctuations in the collisionless Fermi gas.

  15. Hydrodynamics in a Degenerate, Strongly Attractive Fermi Gas

    NASA Technical Reports Server (NTRS)

    Thomas, John E.; Kinast, Joseph; Hemmer, Staci; Turlapov, Andrey; O'Hara, Ken; Gehm, Mike; Granade, Stephen

    2004-01-01

    In summary, we use all-optical methods with evaporative cooling near a Feshbach resonance to produce a strongly interacting degenerate Fermi gas. We observe hydrodynamic behavior in the expansion dynamics. At low temperatures, collisions may not explain the expansion dynamics. We observe hydrodynamics in the trapped gas. Our observations include collisionally-damped excitation spectra at high temperature which were not discussed above. In addition, we observe weakly damped breathing modes at low temperature. The observed temperature dependence of the damping time and hydrodynamic frequency are not consistent with collisional dynamics nor with collisionless mean field interactions. These observations constitute the first evidence for superfluid hydrodynamics in a Fermi gas.

  16. Thermodynamics of the relativistic Fermi gas in D dimensions

    NASA Astrophysics Data System (ADS)

    Sevilla, Francisco J.; Piña, Omar

    2017-09-01

    The influence of spatial dimensionality and particle-antiparticle pair production on the thermodynamic properties of the relativistic Fermi gas, at finite chemical potential, is studied. Resembling a ;phase transition;, qualitatively different behaviors of the thermodynamic susceptibilities, namely the isothermal compressibility and the specific heat, are markedly observed at different temperature regimes as function of the system dimensionality and of the rest mass of the particles. A minimum in the temperature dependence of the isothermal compressibility marks a characteristic temperature, in the range of tenths of the Fermi temperature, at which the system transit from a ;normal; phase, to a phase where the gas compressibility grows as a power law of the temperature.

  17. Trapping effect on the sound velocity of a multilayer Fermi gas

    NASA Astrophysics Data System (ADS)

    Salas, Patricia; Solís, M. A.

    2015-03-01

    We present the trapping effect on the behavior of the isothermal compressibility and sound velocity for an interactionless Fermi gas immersed in a periodic interconnected multilayer structure created by an external Dirac comb potential which can vary both in spacing and in the intensity that controls the impenetrability of the layer edge (the wall). At T = 0 , for a given layer width and respect to the free ideal Fermi gas values, the isothermal compressibility as a function of the impenetrability starts in one and then monotonically increases to reach a larger constant value which is width dependent. The sound velocity as a function of impenetrability starts in one and for a range of impenetrabilities shows a bump which suggests that the presence of the structure increases the speed. For a finite temperature, given a separation between the walls and several values of their impenetrabilities, both properties start their evolution in temperature from the ideal Fermi gas value, unfold at temperatures near and under TF, and then recover the behavior of a classical gas at higher temperatures. We acknowledge partial support from PAPIIT IN111613 and CONACyT 221030.

  18. Chemical potentials and thermodynamic characteristics of ideal Bose- and Fermi-gases in the region of quantum degeneracy

    NASA Astrophysics Data System (ADS)

    Sotnikov, A. G.; Sereda, K. V.; Slyusarenko, Yu. V.

    2017-01-01

    Calculations of chemical potentials for ideal monatomic gases with Bose-Einstein and Fermi-Dirac statistics as functions of temperature, across the temperature region that is typical for the collective quantum degeneracy effect, are presented. Numerical calculations are performed without any additional approximations, and explicit dependences of the chemical potentials on temperature are constructed at a fixed density of gas particles. Approximate polynomial dependences of chemical potentials on temperature are obtained that allow for the results to be used in further studies without re-applying the involved numerical methods. The ease of using the obtained representations is demonstrated on examples of deformation of distribution for a population of energy states at low temperatures, and on the impact of quantum statistics (exchange interaction) on the equations of state for ideal gases and some of the thermodynamic properties thereof. The results of this study essentially unify two opposite limiting cases in an intermediate region that are used to describe the equilibrium states of ideal gases, which are well known from university courses on statistical physics, thus adding value from an educational point of view.

  19. Model for overscreened Kondo effect in ultracold Fermi gas

    NASA Astrophysics Data System (ADS)

    Kuzmenko, I.; Kuzmenko, T.; Avishai, Y.; Kikoin, K.

    2015-04-01

    The feasibility of realizing the overscreened Kondo effect in ultracold Fermi gas of atoms with spin s ≥ 3/2 in the presence of a localized magnetic impurity atom is proved realistic. Specifying (as a mere example) a system of ultracold 22Na Fermi gas and a trapped 6Li impurity, the mechanism of exchange interaction between the Na and Li atoms is elucidated and the exchange constant is found to be positive (antiferromagnetic). The corresponding exchange Hamiltonian is derived, and the Kondo temperature is estimated at the order of 500 nK. Within a weak-coupling renormalization group scheme, it is shown that the coupling renormalizes to the non-Fermi-liquid fixed point. An observable displaying multichannel features even in the weak-coupling regime is the impurity magnetization that is negative for T ≫TK and becomes positive with decreasing temperature.

  20. Universal equation of state and pseudogap in the two-dimensional Fermi gas.

    PubMed

    Bauer, Marianne; Parish, Meera M; Enss, Tilman

    2014-04-04

    We determine the thermodynamic properties and the spectral function for a homogeneous two-dimensional Fermi gas in the normal state using the Luttinger-Ward, or self-consistent T-matrix, approach. The density equation of state deviates strongly from that of the ideal Fermi gas even for moderate interactions, and our calculations suggest that temperature has a pronounced effect on the pressure in the crossover from weak to strong coupling, consistent with recent experiments. We also compute the superfluid transition temperature for a finite system in the crossover region. There is a pronounced pseudogap regime above the transition temperature: the spectral function shows a Bogoliubov-like dispersion with backbending, and the density of states is significantly suppressed near the chemical potential. The contact density at low temperatures increases with interaction and compares well with both experiment and zero-temperature Monte Carlo results.

  1. Degenerate Fermi Gas of Sr87

    NASA Astrophysics Data System (ADS)

    Desalvo, B. J.; Yan, M.; Mickelson, P. G.; Martinez de Escobar, Y. N.; Killian, T. C.

    2010-07-01

    We report quantum degeneracy in a gas of ultracold fermionic Sr87 atoms. By evaporatively cooling a mixture of spin states in an optical dipole trap for 10.5 s, we obtain samples well into the degenerate regime with T/TF=0.26-0.06+0.05. The main signature of degeneracy is a change in the momentum distribution as measured by time-of-flight imaging, and we also observe a decrease in evaporation efficiency below T/TF˜0.5.

  2. Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving.

    PubMed

    Li, Jiaming; de Melo, Leonardo F; Luo, Le

    2017-03-30

    We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling. This experimental protocol starts with a magneto-optical trap (MOT) that is loaded by a Zeeman slower. The precooled atoms in the MOT are then transferred to an ODT, and a bias magnetic field is applied to create an interacting Fermi gas. We then lower the trapping potential to prepare a cold Fermi gas near the degenerate temperature. After that, we sweep the magnetic field to the noninteracting regime of the Fermi gas, in which the parametric cooling can be manifested by modulating the intensity of the optical trapping beams. We find that the parametric cooling effect strongly depends on the modulation frequencies and amplitudes. With the optimized frequency and amplitude, we measure the dependence of the cloud energy on the modulation time. We observe that the cloud energy is changed in an anisotropic way, where the energy of the axial direction is significantly reduced by parametric driving. The cooling effect is limited to the axial direction because the dominant anharmonicity of the crossed-beam ODT is along the axial direction. Finally, we propose to extend this protocol for the trapping potentials of large anharmonicity in all directions, which provides a promising scheme for cooling quantum gases using external driving.

  3. Fermi acceleration in the randomized driven Lorentz gas and the Fermi-Ulam model.

    PubMed

    Karlis, A K; Papachristou, P K; Diakonos, F K; Constantoudis, V; Schmelcher, P

    2007-07-01

    Fermi acceleration of an ensemble of noninteracting particles evolving in a stochastic two-moving wall variant of the Fermi-Ulam model (FUM) and the phase randomized harmonically driven periodic Lorentz gas is investigated. As shown in [A. K. Karlis, P. K. Papachristou, F. K. Diakonos, V. Constantoudis, and P. Schmelcher, Phys. Rev. Lett. 97, 194102 (2006)], the static wall approximation, which ignores scatterer displacement upon collision, leads to a substantial underestimation of the mean energy gain per collision. In this paper, we clarify the mechanism leading to the increased acceleration. Furthermore, the recently introduced hopping wall approximation is generalized for application in the randomized driven Lorentz gas. Utilizing the hopping approximation the asymptotic probability distribution function of the particle velocity is derived. Moreover, it is shown that, for harmonic driving, scatterer displacement upon collision increases the acceleration in both the driven Lorentz gas and the FUM by the same amount. On the other hand, the investigation of a randomized FUM, comprising one fixed and one moving wall driven by a sawtooth force function, reveals that the presence of a particular asymmetry of the driving function leads to an increase of acceleration that is different from that gained when symmetrical force functions are considered, for all finite number of collisions. This fact helps open up the prospect of designing accelerator devices by combining driving laws with specific symmetries to acquire a desired acceleration behavior for the ensemble of particles.

  4. Ideal gas behavior of a strongly coupled complex (dusty) plasma.

    PubMed

    Oxtoby, Neil P; Griffith, Elias J; Durniak, Céline; Ralph, Jason F; Samsonov, Dmitry

    2013-07-05

    In a laboratory, a two-dimensional complex (dusty) plasma consists of a low-density ionized gas containing a confined suspension of Yukawa-coupled plastic microspheres. For an initial crystal-like form, we report ideal gas behavior in this strongly coupled system during shock-wave experiments. This evidence supports the use of the ideal gas law as the equation of state for soft crystals such as those formed by dusty plasmas.

  5. Laser cooling of a trapped two-component Fermi gas

    SciTech Connect

    Idziaszek, Z.; Santos, L.; Lewenstein, M.; Baranov, M.

    2003-04-01

    We study the collective Raman cooling of a trapped two-component Fermi gas using quantum master equation in the festina lente regime, where the heating due to photon reabsorption can be neglected. The Monte Carlo simulations show that three-dimensional temperatures of the order of 0.008T{sub F} can be achieved. We analyze the heating related to background losses, and show that our laser-cooling scheme can maintain the temperature of the gas without significant additional losses.

  6. Higgs Mode in a Trapped Superfluid Fermi Gas

    NASA Astrophysics Data System (ADS)

    Tokimoto, Jun; Tsuchiya, Shunji; Nikuni, Tetsuro

    2017-03-01

    In quantum many-body systems with spontaneous breaking of a continuous symmetry, Higgs modes emerge as collective amplitude oscillations of order parameters. Recently, Higgs modes have been observed in superconductors and in Bose gases in optical lattices. However, it has yet to be observed in Fermi gases. In the present paper, we use the time-dependent Bogoliubov-de Gennes equations to investigate Higgs amplitude oscillations of the superfluid order parameter in a trapped Fermi gas induced by a sudden changes of the { s} -wave scattering length. In particular, we investigate the Higgs mode with different values of the initial scattering length and discuss how the frequency and damping of the Higgs mode changes around the unitarity regime.

  7. Do the Particles of an Ideal Gas Collide?

    ERIC Educational Resources Information Center

    Lesk, Arthur M.

    1974-01-01

    Describes the collisional properties as a logically essential component of the ideal gas model since an actual intraparticle process cannot support observable anisotropic velocity distributions without collisions taken into account. (CC)

  8. Computer program for calculation of ideal gas thermodynamic data

    NASA Technical Reports Server (NTRS)

    Gordon, S.; Mc Bride, B. J.

    1968-01-01

    Computer program calculates ideal gas thermodynamic properties for any species for which molecular constant data is available. Partial functions and derivatives from formulas based on statistical mechanics are provided by the program which is written in FORTRAN 4 and MAP.

  9. Transverse demagnetization dynamics of a unitary Fermi gas.

    PubMed

    Bardon, A B; Beattie, S; Luciuk, C; Cairncross, W; Fine, D; Cheng, N S; Edge, G J A; Taylor, E; Zhang, S; Trotzky, S; Thywissen, J H

    2014-05-16

    Understanding the quantum dynamics of strongly interacting fermions is a problem relevant to diverse forms of matter, including high-temperature superconductors, neutron stars, and quark-gluon plasma. An appealing benchmark is offered by cold atomic gases in the unitary limit of strong interactions. Here, we study the dynamics of a transversely magnetized unitary Fermi gas in an inhomogeneous magnetic field. We observe the demagnetization of the gas, caused by diffusive spin transport. At low temperatures, the diffusion constant saturates to the conjectured quantum-mechanical lower bound ≃ ħ/m, where m is the particle mass. The development of pair correlations, indicating the transformation of the initially noninteracting gas toward a unitary spin mixture, is observed by measuring Tan's contact parameter. Copyright © 2014, American Association for the Advancement of Science.

  10. Creation of ultracold molecules from a Fermi gas of atoms.

    PubMed

    Regal, Cindy A; Ticknor, Christopher; Bohn, John L; Jin, Deborah S

    2003-07-03

    Following the realization of Bose-Einstein condensates in atomic gases, an experimental challenge is the production of molecular gases in the quantum regime. A promising approach is to create the molecular gas directly from an ultracold atomic gas; for example, bosonic atoms in a Bose-Einstein condensate have been coupled to electronic ground-state molecules through photoassociation or a magnetic field Feshbach resonance. The availability of atomic Fermi gases offers the prospect of coupling fermionic atoms to bosonic molecules, thus altering the quantum statistics of the system. Such a coupling would be closely related to the pairing mechanism in a fermionic superfluid, predicted to occur near a Feshbach resonance. Here we report the creation and quantitative characterization of ultracold 40K2 molecules. Starting with a quantum degenerate Fermi gas of atoms at a temperature of less than 150 nK, we scan the system over a Feshbach resonance to create adiabatically more than 250,000 trapped molecules; these can be converted back to atoms by reversing the scan. The small binding energy of the molecules is controlled by detuning the magnetic field away from the Feshbach resonance, and can be varied over a wide range. We directly detect these weakly bound molecules through their radio-frequency photodissociation spectra; these probe the molecular wavefunction, and yield binding energies that are consistent with theory.

  11. First and second sound in a strongly interacting Fermi gas

    NASA Astrophysics Data System (ADS)

    Taylor, E.; Hu, H.; Liu, X.-J.; Pitaevskii, L. P.; Griffin, A.; Stringari, S.

    2009-11-01

    Using a variational approach, we solve the equations of two-fluid hydrodynamics for a uniform and trapped Fermi gas at unitarity. In the uniform case, we find that the first and second sound modes are remarkably similar to those in superfluid helium, a consequence of strong interactions. In the presence of harmonic trapping, first and second sound become degenerate at certain temperatures. At these points, second sound hybridizes with first sound and is strongly coupled with density fluctuations, giving a promising way of observing second sound. We also discuss the possibility of exciting second sound by generating local heat perturbations.

  12. Itinerant ferromagnetism in a polarized two-component Fermi gas.

    PubMed

    Massignan, Pietro; Yu, Zhenhua; Bruun, Georg M

    2013-06-07

    We analyze when a repulsively interacting two-component Fermi gas becomes thermodynamically unstable against phase separation. We focus on the strongly polarized limit, where the free energy of the homogeneous mixture can be calculated accurately in terms of well-defined quasiparticles, the repulsive polarons. Phase diagrams as a function of polarization, temperature, mass imbalance, and repulsive polaron energy, as well as scattering length and range parameter, are provided. We show that the lifetime of the repulsive polaron increases significantly with the interaction range and the mass of the minority atoms, raising the prospects of detecting the transition to the elusive itinerant ferromagnetic state with ultracold atoms.

  13. Collective oscillations of a Fermi gas near a Feshbach resonance

    SciTech Connect

    De Silva, Theja N.; Mueller, Erich J.

    2005-12-15

    A sum rule approach is used to calculate the zero temperature oscillation frequencies of a two component trapped atomic Fermi gas in the Bardeen, Cooper, and Schrieffer-Bose Einstein condensation crossover region. These sum rules are evaluated using a local density approximation which explicitly includes Feshbach molecules. Breathing modes show nonmonotonic behavior as a function of the interaction strength, while quadrupole modes are insensitive to interactions for both spherically symmetric and axially symmetric traps. Quantitative agreement is found with experiments on atomic {sup 6}Li systems and with other theoretical approaches.

  14. Virial Expansion for a Strongly Correlated Fermi Gas

    NASA Astrophysics Data System (ADS)

    Hu, Hui

    2011-03-01

    Few-body physics can give considerable insight into the challenging many-body problem. A concrete example is the exact Tan relations linking the ``hard'' (few-body) physics at short distance, large-momentum and high frequency to the ``soft'' physics of the equation of state via a contact parameter. This has been demonstrated clearly using the operator product expansion (OPE) method which separates in a natural way few-body from many-body physics. In this talk, we present another example: the quantum virial expansion that bridges few-body and many-body physics. At large temperatures, the properties of a strongly correlated Fermi gas, either static or dynamic, can be expanded in terms of virial coefficients or expansion functions, calculable from the few-fermion solutions. For the equation of state in the resonant unitarity limit, we obtain for the first time an accurate third order virial coefficient. This has been experimentally verified in a measurement at ENS (Paris). For the single-particle spectral function, we demonstrate that an expansion up to second order is able to explain the main features of momentum-resolved RF spectroscopy in a resonantly interacting Fermi gas, as recently reported by JILA. We also obtain a virial expansion of the dynamic structure function, as measured at Swinburne University (Melbourne), and check that the second order expansion functions give the correct OPE coefficients in the limit of large momentum and frequency. The important feature of this expansion is the existence of a small parameter, the fugacity, even for strong interactions. In the future, we anticipate that higher-order virial expansions of dynamic properties such as the single-particle spectral function may provide useful insights into clarifying the debate on the pseudo-gap issue in resonantly interacting Fermi gases.

  15. Low-lying excitations in a strongly interacting Fermi gas

    NASA Astrophysics Data System (ADS)

    Vale, Christopher; Hoinka, Sascha; Dyke, Paul; Lingham, Marcus

    2016-05-01

    We present measurements of the low-lying excitation spectrum of a strongly interacting Fermi gas across the Bardeen-Cooper-Schrieffer (BCS) to Bose-Einstein condensate (BEC) crossover using Bragg spectroscopy. By focussing the Bragg lasers onto the central volume of the cloud we can probe atoms at near-uniform density allowing measurement of the homogeneous density-density response function. The Bragg wavevector is set to be approximately half of the Fermi wavevector to probe the collective response. Below the superfluid transition temperature the Bragg spectra dominated by the Bogoliubov-Anderson phonon mode. Single particle excitations become visible at energies greater than twice the pairing gap. As interactions are tuned from the BCS to BEC regime the phonon and single particle modes separate apart and both the pairing gap and speed of sound can be directly read off in certain regions of the crossover. Single particle pair-breaking excitations become heavily suppressed as interactions are tuned from the BCS to BEC regimes.

  16. Simulating strongly correlated electrons with a strongly interacting Fermi gas

    SciTech Connect

    Thomas, John E.

    2013-05-28

    The quantum many-body physics of strongly-correlated fermions is studied in a degenerate, strongly- interacting atomic Fermi gas, first realized by our group with DOE support in 2002. This system, which exhibits strong spin pairing, is now widely studied and provides an important paradigm for testing predictions based on state-of-the-art many-body theory in fields ranging from nuclear matter to high temperature superfluidity and superconductivity. As the system is strongly interacting, both the superfluid and the normal fluid are nontrivial and of great interest. A central part of our program on Fermi gases is the connection between the study of thermodynamics, supported by DOE and the study of hydrodynamic transport, supported by NSF. This connection is especially interesting in view of a recent conjecture from the string theory community on the concept of nearly perfect normal fluids, which exhibit a minimum ratio of shear viscosity to entropy density in strongly-interacting, scale-invariant systems.

  17. Thermodynamics of an ideal generalized gas: I. Thermodynamic laws.

    PubMed

    Lavenda, B H

    2005-11-01

    The equations of state for an ideal relativistic, or generalized, gas, like an ideal quantum gas, are expressed in terms of power laws of the temperature. In contrast to an ideal classical gas, the internal energy is a function of volume at constant temperature, implying that the ideal generalized gas will show either attractive or repulsive interactions. This is a necessary condition in order that the third law be obeyed and for matter to have an electromagnetic origin. The transition from an ideal generalized to a classical gas occurs when the two independent solutions of the subsidiary equation to Lagrange's equation coalesce. The equation of state relating the pressure to the internal energy encompasses the full range of cosmological scenarios, from the radiation to the matter dominated universes and finally to the vacuum energy, enabling the coefficient of proportionality, analogous to the Grüeisen ratio, to be interpreted in terms of the degrees of freedom related to the temperature exponents of the internal energy and the absolute temperature expressed in terms of a power of the empirical temperature. The limit where these exponents merge is shown to be the ideal classical gas limit. A corollary to Carnot's theorem is proved, asserting that the ratio of the work done over a cycle to the heat absorbed to increase the temperature at constant volume is the same for all bodies at the same volume. As power means, the energy and entropy are incomparable, and a new adiabatic potential is introduced by showing that the volume raised to a characteristic exponent is also the integrating factor for the quantity of heat so that the second law can be based on the property that power means are monotonically increasing functions of their order. The vanishing of the chemical potential in extensive systems implies that energy cannot be transported without matter and is equivalent to the condition that Clapeyron's equation be satisfied.

  18. Thermodynamics of an ideal generalized gas: I. Thermodynamic laws

    NASA Astrophysics Data System (ADS)

    Lavenda, B. H.

    2005-11-01

    The equations of state for an ideal relativistic, or generalized, gas, like an ideal quantum gas, are expressed in terms of power laws of the temperature. In contrast to an ideal classical gas, the internal energy is a function of volume at constant temperature, implying that the ideal generalized gas will show either attractive or repulsive interactions. This is a necessary condition in order that the third law be obeyed and for matter to have an electromagnetic origin. The transition from an ideal generalized to a classical gas occurs when the two independent solutions of the subsidiary equation to Lagrange's equation coalesce. The equation of state relating the pressure to the internal energy encompasses the full range of cosmological scenarios, from the radiation to the matter dominated universes and finally to the vacuum energy, enabling the coefficient of proportionality, analogous to the Grüeisen ratio, to be interpreted in terms of the degrees of freedom related to the temperature exponents of the internal energy and the absolute temperature expressed in terms of a power of the empirical temperature. The limit where these exponents merge is shown to be the ideal classical gas limit. A corollary to Carnot's theorem is proved, asserting that the ratio of the work done over a cycle to the heat absorbed to increase the temperature at constant volume is the same for all bodies at the same volume. As power means, the energy and entropy are incomparable, and a new adiabatic potential is introduced by showing that the volume raised to a characteristic exponent is also the integrating factor for the quantity of heat so that the second law can be based on the property that power means are monotonically increasing functions of their order. The vanishing of the chemical potential in extensive systems implies that energy cannot be transported without matter and is equivalent to the condition that Clapeyron's equation be satisfied.

  19. Trapped 173Yb Fermi gas across an orbital Feshbach resonance

    NASA Astrophysics Data System (ADS)

    Iskin, M.

    2017-01-01

    Starting with the two-band description of an orbital Feshbach resonance, we study superfluid properties of a trapped 173Yb Fermi gas under the assumptions of a local-density approximation for the trapping potential and a mean-field approximation for the intraband Cooper pairings. In particular, we investigate the competition and interplay between the pair-breaking effect that is caused by the interband detuning energy, and the pair-breaking and thermal-broadening effects that are simultaneously caused by the temperature. We predict several experimental signatures that are directly caused by this interplay including a spatial separation of superfluid and normal phases within the trap, and could play decisive roles in probing two-band superfluidity in these systems.

  20. Contact interaction in an unitary ultracold Fermi gas

    SciTech Connect

    Pessoa, Renato; Gandolfi, Stefano; Vitiello, S. A.; Schmidt, Kevin E.

    2015-12-16

    An ultracold Fermi atomic gas at unitarity presents universal properties that in the dilute limit can be well described by a contact interaction. By employing a guiding function with correct boundary conditions and making simple modifications to the sampling procedure we are able to calculate the properties of a true contact interaction with the diffusion Monte Carlo method. The results are obtained with small variances. Our calculations for the Bertsch and contact parameters are in excellent agreement with published experiments. The possibility of using a more faithful description of ultracold atomic gases can help uncover additional features of ultracold atomic gases. In addition, this work paves the way to perform quantum Monte Carlo calculations for other systems interacting with contact interactions, where the description using potentials with finite effective range might not be accurate.

  1. Unitary Fermi Gas, ɛ Expansion, and Nonrelativistic Conformal Field Theories

    NASA Astrophysics Data System (ADS)

    Nishida, Yusuke; Son, Dam Thanh

    We review theoretical aspects of unitary Fermi gas (UFG), which has been realized in ultracold atom experiments. We first introduce the ɛ expansion technique based on a systematic expansion in terms of the dimensionality of space. We apply this technique to compute the thermodynamic quantities, the quasiparticle cum, and the criticl temperature of UFG. We then discuss consequences of the scale and conformal invariance of UFG. We prove a correspondence between primary operators in nonrelativistic conformal field theories and energy eigenstates in a harmonic potential. We use this correspondence to compute energies of fermions at unitarity in a harmonic potential. The scale and conformal invariance together with the general coordinate invariance constrains the properties of UFG. We show the vanishing bulk viscosities of UFG and derive the low-energy effective Lagrangian for the superfluid UFG. Finally we propose other systems exhibiting the nonrelativistic scaling and conformal symmetries that can be in principle realized in ultracold atom experiments.

  2. Contact interaction in an unitary ultracold Fermi gas

    DOE PAGES

    Pessoa, Renato; Gandolfi, Stefano; Vitiello, S. A.; ...

    2015-12-16

    An ultracold Fermi atomic gas at unitarity presents universal properties that in the dilute limit can be well described by a contact interaction. By employing a guiding function with correct boundary conditions and making simple modifications to the sampling procedure we are able to calculate the properties of a true contact interaction with the diffusion Monte Carlo method. The results are obtained with small variances. Our calculations for the Bertsch and contact parameters are in excellent agreement with published experiments. The possibility of using a more faithful description of ultracold atomic gases can help uncover additional features of ultracold atomicmore » gases. In addition, this work paves the way to perform quantum Monte Carlo calculations for other systems interacting with contact interactions, where the description using potentials with finite effective range might not be accurate.« less

  3. Solitonic Vortex in a Strongly-Interacting Fermi Gas

    NASA Astrophysics Data System (ADS)

    Ku, Mark; Ji, Wenjie; Mukherjee, Biswaroop; Cheuk, Lawrence; Sanchez, Elmer; Yefsah, Tarik; Zwierlein, Martin

    2014-05-01

    We investigate the solitonic excitation observed in our previous experiments [Yefsah et al., Nature 499, 426 (2013)] for a unitary Fermi gas with tomographic imaging. In this work, we directly access the local density of our 3D clouds by imaging a thin layer of atoms, which we achieve with a masked pumping beam that transfers atoms outside of the selected layer into an undetected state. Using the tomographic imaging, which circumvents the density integration along the probing axis, we identify unambiguously this excitation as a solitonic vortex. In particular, we rule out the vortex ring scenario predicted by several theory groups. Our measurements provide a quantitative benchmark for the theories of non-equilibrium dynamics of strongly-interacting superfluids.

  4. A Demonstration of Ideal Gas Principles Using a Football.

    ERIC Educational Resources Information Center

    Bare, William D.; Andrews, Lester

    1999-01-01

    Uses a true-to-life story of accusations made against a college football team to illustrate ideal gas laws. Students are asked to decide whether helium-filled footballs would increase punt distances and how to determine whether a football contained air or helium. (WRM)

  5. Fluctuation theorem for the effusion of an ideal gas.

    PubMed

    Cleuren, B; Van den Broeck, C; Kawai, R

    2006-08-01

    The probability distribution of the entropy production for the effusion of an ideal gas between two compartments is calculated explicitly. The fluctuation theorem is verified. The analytic results are in good agreement with numerical data from hard disk molecular dynamics simulations.

  6. Shock wave structure in an ideal dissociating gas

    NASA Technical Reports Server (NTRS)

    Liu, K. H.

    1975-01-01

    Composition changes within the shock layer due to chemical reactions are considered. The Lighthill ideal dissociating gas model was used in an effort to describe the oxygen type molecule. First, the two limiting cases, when the chemical reaction rates are very slow and very fast in comparison to local convective rates, are investigated. Then, the problem is solved for arbitrary chemical reaction rates.

  7. Condensation of an ideal gas obeying non-Abelian statistics.

    PubMed

    Mirza, Behrouz; Mohammadzadeh, Hosein

    2011-09-01

    We consider the thermodynamic geometry of an ideal non-Abelian gas. We show that, for a certain value of the fractional parameter and at the relevant maximum value of fugacity, the thermodynamic curvature has a singular point. This indicates a condensation such as Bose-Einstein condensation for non-Abelian statistics and we work out the phase transition temperature in various dimensions.

  8. From Free Expansion to Abrupt Compression of an Ideal Gas

    ERIC Educational Resources Information Center

    Anacleto, Joaquim; Pereira, Mario G.

    2009-01-01

    Using macroscopic thermodynamics, the general law for adiabatic processes carried out by an ideal gas was studied. It was shown that the process reversibility is characterized by the adiabatic reversibility coefficient r, in the range 0 [less than or equal] r [less than or equal] 1 for expansions and r [greater than or equal] 1 for compressions.…

  9. Experimental Verification of Boyle's Law and the Ideal Gas Law

    ERIC Educational Resources Information Center

    Ivanov, Dragia Trifonov

    2007-01-01

    Two new experiments are offered concerning the experimental verification of Boyle's law and the ideal gas law. To carry out the experiments, glass tubes, water, a syringe and a metal manometer are used. The pressure of the saturated water vapour is taken into consideration. For educational purposes, the experiments are characterized by their…

  10. A Demonstration of Ideal Gas Principles Using a Football.

    ERIC Educational Resources Information Center

    Bare, William D.; Andrews, Lester

    1999-01-01

    Uses a true-to-life story of accusations made against a college football team to illustrate ideal gas laws. Students are asked to decide whether helium-filled footballs would increase punt distances and how to determine whether a football contained air or helium. (WRM)

  11. From Free Expansion to Abrupt Compression of an Ideal Gas

    ERIC Educational Resources Information Center

    Anacleto, Joaquim; Pereira, Mario G.

    2009-01-01

    Using macroscopic thermodynamics, the general law for adiabatic processes carried out by an ideal gas was studied. It was shown that the process reversibility is characterized by the adiabatic reversibility coefficient r, in the range 0 [less than or equal] r [less than or equal] 1 for expansions and r [greater than or equal] 1 for compressions.…

  12. Experimental Verification of Boyle's Law and the Ideal Gas Law

    ERIC Educational Resources Information Center

    Ivanov, Dragia Trifonov

    2007-01-01

    Two new experiments are offered concerning the experimental verification of Boyle's law and the ideal gas law. To carry out the experiments, glass tubes, water, a syringe and a metal manometer are used. The pressure of the saturated water vapour is taken into consideration. For educational purposes, the experiments are characterized by their…

  13. Aharony-Bergman-Jafferis-Maldacena Wilson Loops in the Fermi Gas Approach

    NASA Astrophysics Data System (ADS)

    Klemm, Albrecht; Mariño, Marcos; Soroush, Masoud

    2013-02-01

    The matrix model of the Aharony-Bergman-Jafferis-Maldacena theory can be formulated in terms of an ideal Fermi gas with a non-trivial one-particle Hamiltonian. We show that, in this formalism, vacuum expectation values (vevs) of Wilson loops correspond to averages of operators in the statistical-mechanical problem. This makes it possible to calculate these vevs at all orders in 1/N, up to exponentially small corrections, and for arbitrary Chern-Simons coupling, by using the Wentzel- Kramer-Brillouin expansion.We present explicit results for the vevs of 1/6 and the 1/2 Bogomolnyi- Prasad-Sommerfield Wilson loops, at any winding number, in terms of Airy functions. Our expressions are shown to reproduce the low genus results obtained previously in the 't Hooft expansion.

  14. Collisional Properties of a Polarized Fermi Gas with Resonant Interactions

    SciTech Connect

    Bruun, G. M.; Recati, A.; Stringari, S.; Pethick, C. J.; Smith, H.

    2008-06-20

    Highly polarized mixtures of atomic Fermi gases constitute a novel Fermi liquid. We demonstrate how information on thermodynamic properties may be used to calculate quasiparticle scattering amplitudes even when the interaction is resonant and apply the results to evaluate the damping of the spin dipole mode. We estimate that under current experimental conditions the mode would be intermediate between the hydrodynamic and collisionless limits.

  15. Bose-Einstein Condensation in the Relativistic Ideal Bose Gas

    SciTech Connect

    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.

  16. Bose-Einstein condensation in the relativistic ideal Bose gas.

    PubMed

    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.

  17. Viscosity and scale invariance in the unitary Fermi gas

    SciTech Connect

    Enss, Tilman; Haussmann, Rudolf; Zwerger, Wilhelm

    2011-03-15

    We compute the shear viscosity of the unitary Fermi gas above the superfluid transition temperature, using a diagrammatic technique that starts from the exact Kubo formula. The formalism obeys a Ward identity associated with scale invariance which guarantees that the bulk viscosity vanishes identically. For the shear viscosity, vertex corrections and the associated Aslamazov-Larkin contributions are shown to be crucial to reproduce the full Boltzmann equation result in the high-temperature, low fugacity limit. The frequency dependent shear viscosity {eta}({omega}) exhibits a Drude-like transport peak and a power-law tail at large frequencies which is proportional to the Tan contact. The weight in the transport peak is given by the equilibrium pressure, in agreement with a sum rule due to Taylor and Randeria. Near the superfluid transition the peak width is of the order of 0.5T{sub F}, thus invalidating a quasiparticle description. The ratio {eta}/s between the static shear viscosity and the entropy density exhibits a minimum near the superfluid transition temperature whose value is larger than the string theory bound h/(4{pi}k{sub B}) by a factor of about seven.

  18. Exciting Quantized Vortex Rings in a Superfluid Unitary Fermi Gas

    NASA Astrophysics Data System (ADS)

    Bulgac, Aurel

    2014-03-01

    In a recent article, Yefsah et al., Nature 499, 426 (2013) report the observation of an unusual quantum excitation mode in an elongated harmonically trapped unitary Fermi gas. After phase imprinting a domain wall, they observe collective oscillations of the superfluid atomic cloud with a period almost an order of magnitude larger than that predicted by any theory of domain walls, which they interpret as a possible new quantum phenomenon dubbed ``a heavy soliton'' with an inertial mass some 50 times larger than one expected for a domain wall. We present compelling evidence that this ``heavy soliton'' is instead a quantized vortex ring by showing that the main aspects of the experiment can be naturally explained within an extension of the time-dependent density functional theory (TDDFT) to superfluid systems. The numerical simulations required the solution of some 260,000 nonlinear coupled time-dependent 3-dimensional partial differential equations and was implemented on 2048 GPUs on the Cray XK7 supercomputer Titan of the Oak Ridge Leadership Computing Facility.

  19. Computations of ideal and real gas high altitude plume flows

    NASA Technical Reports Server (NTRS)

    Feiereisen, William J.; Venkatapathy, Ethiraj

    1988-01-01

    In the present work, complete flow fields around generic space vehicles in supersonic and hypersonic flight regimes are studied numerically. Numerical simulation is performed with a flux-split, time asymptotic viscous flow solver that incorporates a generalized equilibrium chemistry model. Solutions to generic problems at various altitude and flight conditions show the complexity of the flow, the equilibrium chemical dissociation and its effect on the overall flow field. Viscous ideal gas solutions are compared against equilibrium gas solutions to illustrate the effect of equilibrium chemistry. Improved solution accuracy is achieved through adaptive grid refinement.

  20. Measurement of optical Feshbach resonances in an ideal gas.

    PubMed

    Blatt, S; Nicholson, T L; Bloom, B J; Williams, J R; Thomsen, J W; Julienne, P S; Ye, J

    2011-08-12

    Using a narrow intercombination line in alkaline earth atoms to mitigate large inelastic losses, we explore the optical Feshbach resonance effect in an ultracold gas of bosonic (88)Sr. A systematic measurement of three resonances allows precise determinations of the optical Feshbach resonance strength and scaling law, in agreement with coupled-channel theory. Resonant enhancement of the complex scattering length leads to thermalization mediated by elastic and inelastic collisions in an otherwise ideal gas. Optical Feshbach resonance could be used to control atomic interactions with high spatial and temporal resolution.

  1. Wilson loops in 3d {N} = 4 SQCD from Fermi gas

    NASA Astrophysics Data System (ADS)

    Okuyama, Kazumi

    2016-11-01

    We study 1/2 BPS Wilson loops in 3d {N} = 4 U( N ) Yang-Mills theory with one adjoint and N f fundamental hypermultiplets from the Fermi gas approach. By numerical fitting, we find the first few worldsheet instanton corrections to the Wilson loops with winding numbers 1, 2 and 3. We verify that our Fermi gas results are consistent with the matrix model results in the planar limit.

  2. Ultracold strongly coupled gas: A near-ideal liquid

    NASA Astrophysics Data System (ADS)

    Gelman, Boris A.; Shuryak, Edward V.; Zahed, Ismail

    2005-10-01

    Feshbach resonances of trapped ultracold alkali-metal atoms allow to vary the atomic scattering length a . At very large values of a the system enters an universal strongly coupled regime in which its properties—the ground-state energy, pressure, etc.—become independent of a . We discuss the transport properties of such systems. In particular, the universality arguments imply that the shear viscosity of ultracold Fermi atoms at the Feschbach resonance is proportional to the particle number density n and the Plank constant ℏ : η=ℏnαη , where αη is a universal constant. Using Heisenberg uncertainty principle and Einstein’s relation between diffusion and viscosity we argue that the viscosity has the lower bound given by αη⩽(6π)-1 . We relate the damping of low-frequency density oscillations of ultracold optically trapped Li6 atoms to viscosity and find that the value of the coefficient αη is about 0.3. We also show that such a small viscosity cannot be explained by kinetic theory based on binary scattering. We conclude that the system of ultracold atoms near the Feshbach resonance is a near-ideal liquid.

  3. Ultracold strongly coupled gas: A near-ideal liquid

    SciTech Connect

    Gelman, Boris A.; Shuryak, Edward V.; Zahed, Ismail

    2005-10-15

    Feshbach resonances of trapped ultracold alkali-metal atoms allow to vary the atomic scattering length a. At very large values of a the system enters an universal strongly coupled regime in which its properties--the ground-state energy, pressure, etc.--become independent of a. We discuss the transport properties of such systems. In particular, the universality arguments imply that the shear viscosity of ultracold Fermi atoms at the Feschbach resonance is proportional to the particle number density n and the Plank constant ({Dirac_h}/2{pi}): {eta}=({Dirac_h}/2{pi})n{alpha}{sub {eta}}, where {alpha}{sub {eta}} is a universal constant. Using Heisenberg uncertainty principle and Einstein's relation between diffusion and viscosity we argue that the viscosity has the lower bound given by {alpha}{sub {eta}}{<=}(6{pi}){sup -1}. We relate the damping of low-frequency density oscillations of ultracold optically trapped {sup 6}Li atoms to viscosity and find that the value of the coefficient {alpha}{sub {eta}} is about 0.3. We also show that such a small viscosity cannot be explained by kinetic theory based on binary scattering. We conclude that the system of ultracold atoms near the Feshbach resonance is a near-ideal liquid.

  4. Universal spin transport in a strongly interacting Fermi gas.

    PubMed

    Sommer, Ariel; Ku, Mark; Roati, Giacomo; Zwierlein, Martin W

    2011-04-14

    Transport of fermions, particles with half-integer spin, is central to many fields of physics. Electron transport runs modern technology, defining states of matter such as superconductors and insulators, and electron spin is being explored as a new carrier of information. Neutrino transport energizes supernova explosions following the collapse of a dying star, and hydrodynamic transport of the quark-gluon plasma governed the expansion of the early Universe. However, our understanding of non-equilibrium dynamics in such strongly interacting fermionic matter is still limited. Ultracold gases of fermionic atoms realize a pristine model for such systems and can be studied in real time with the precision of atomic physics. Even above the superfluid transition, such gases flow as an almost perfect fluid with very low viscosity when interactions are tuned to a scattering resonance. In this hydrodynamic regime, collective density excitations are weakly damped. Here we experimentally investigate spin excitations in a Fermi gas of (6)Li atoms, finding that, in contrast, they are maximally damped. A spin current is induced by spatially separating two spin components and observing their evolution in an external trapping potential. We demonstrate that interactions can be strong enough to reverse spin currents, with components of opposite spin reflecting off each other. Near equilibrium, we obtain the spin drag coefficient, the spin diffusivity and the spin susceptibility as a function of temperature on resonance and show that they obey universal laws at high temperatures. In the degenerate regime, the spin diffusivity approaches a value set by [planck]/m, the quantum limit of diffusion, where [planck]/m is Planck's constant divided by 2π and m the atomic mass. For repulsive interactions, our measurements seem to exclude a metastable ferromagnetic state.

  5. Observations of density fluctuations in an elongated Bose gas: ideal gas and quasicondensate regimes.

    PubMed

    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.

  6. Strong-coupling corrections to ground-state properties of a superfluid Fermi gas

    NASA Astrophysics Data System (ADS)

    Tajima, Hiroyuki; van Wyk, Pieter; Hanai, Ryo; Kagamihara, Daichi; Inotani, Daisuke; Horikoshi, Munekazu; Ohashi, Yoji

    2017-04-01

    We theoretically present an economical and convenient way to study ground-state properties of a strongly interacting superfluid Fermi gas. Our strategy is that complicated strong-coupling calculations are used only to evaluate quantum fluctuation corrections to the chemical potential μ . Then, without any further strong-coupling calculations, we calculate the compressibility, sound velocity, internal energy, pressure, and Tan's contact, from the calculated μ without loss of accuracy, by using exact thermodynamic identities. Using a recent precise measurement of μ in a superfluid 6Li Fermi gas, we show that an extended T -matrix approximation (ETMA) is suitable for our purpose, especially in the BCS-unitary regime, where our results indicate that many-body corrections are dominated by superfluid fluctuations. Since precise determinations of physical quantities are not always easy in cold Fermi gas physics, our approach would greatly reduce experimental and theoretical efforts toward the understanding of ground-state properties of this strongly interacting Fermi system.

  7. Ferromagnetism in the upper branch of the Feshbach resonance and the hard-sphere Fermi gas

    PubMed Central

    Chang, Soon-Yong; Randeria, Mohit; Trivedi, Nandini

    2011-01-01

    We address the question of ferromagnetism in repulsive Fermi gas, a problem of fundamental interest, using quantum Monte Carlo simulations that include backflow corrections. We investigate a two-component Fermi gas on the upper branch of a Feshbach resonance and contrast it with the hard-sphere gas. We find that, in both cases, the Fermi liquid becomes unstable to ferromagnetism at a kFa smaller than the mean field result, where kF is the Fermi wavevector and a is the scattering length. Even though the total energies E(kFa) are similar in the two cases, their pair correlations and kinetic energies are completely different, reflecting the underlying potentials. We discuss the extent to which our calculations shed light on recent experiments.

  8. Conical flow near singular rays. [shock generation in ideal gas

    NASA Technical Reports Server (NTRS)

    Zahalak, G. I.; Myers, M. K.

    1974-01-01

    The steady flow of an ideal gas past a conical body is investigated by the method of matched asymptotic expansions, with particular emphasis on the flow near the singular ray occurring in linearized theory. The first-order problem governing the flow in this region is formulated, leading to the equation of Kuo, and an approximate solution is obtained in the case of compressive flow behind the main front. This solution is compared with the results of previous investigations with a view to assessing the applicability of the Lighthill-Whitham theories.

  9. Microeconomics of the ideal gas like market models

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Anindya S.; Chakrabarti, Bikas K.

    2009-10-01

    We develop a framework based on microeconomic theory from which the ideal gas like market models can be addressed. A kinetic exchange model based on that framework is proposed and its distributional features have been studied by considering its moments. Next, we derive the moments of the CC model (Eur. Phys. J. B 17 (2000) 167) as well. Some precise solutions are obtained which conform with the solutions obtained earlier. Finally, an output market is introduced with global price determination in the model with some necessary modifications.

  10. Boltzmann equations for a binary one-dimensional ideal gas.

    PubMed

    Boozer, A D

    2011-09-01

    We consider a time-reversal invariant dynamical model of a binary ideal gas of N molecules in one spatial dimension. By making time-asymmetric assumptions about the behavior of the gas, we derive Boltzmann and anti-Boltzmann equations that describe the evolution of the single-molecule velocity distribution functions for an ensemble of such systems. We show that for a special class of initial states of the ensemble one can obtain an exact expression for the N-molecule velocity distribution function, and we use this expression to rigorously prove that the time-asymmetric assumptions needed to derive the Boltzmann and anti-Boltzmann equations hold in the limit of large N. Our results clarify some subtle issues regarding the origin of the time asymmetry of Boltzmann's H theorem.

  11. Convection in an ideal gas at high Rayleigh numbers.

    PubMed

    Tilgner, A

    2011-08-01

    Numerical simulations of convection in a layer filled with ideal gas are presented. The control parameters are chosen such that there is a significant variation of density of the gas in going from the bottom to the top of the layer. The relations between the Rayleigh, Peclet, and Nusselt numbers depend on the density stratification. It is proposed to use a data reduction which accounts for the variable density by introducing into the scaling laws an effective density. The relevant density is the geometric mean of the maximum and minimum densities in the layer. A good fit to the data is then obtained with power laws with the same exponent as for fluids in the Boussinesq limit. Two relations connect the top and bottom boundary layers: The kinetic energy densities computed from free fall velocities are equal at the top and bottom, and the products of free fall velocities and maximum horizontal velocities are equal for both boundaries.

  12. Strong-Coupling Properties of a p-Wave Interacting Fermi Gas on the Viewpoint of Specific Heat at Constant Volume

    NASA Astrophysics Data System (ADS)

    Inotani, Daisuke; van Wyk, Pieter; Ohashi, Yoji

    2017-02-01

    We theoretically investigate the specific heat CV at constant volume in the normal state of a p-wave interacting Fermi gas. Including fluctuations in the p-wave Cooper channel within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink, we clarify how CV as a function of temperature varies, as one moves from the weak-coupling regime to the strong-coupling limit. In the weak-coupling regime, CV is shown to be enhanced by p-wave pairing fluctuations, near the superfluid phase transition temperature Tc. Similar enhancement of CV(T ≃ Tc) is also obtained in the strong-coupling regime, which, however, reflects that system is close an ideal Bose gas of p-wave two-body bound molecules. Using these results, we classify the normal state into (1) the normal Fermi gas regime, (2) the p-wave molecular Bose gas regime, and (3) the region between the two, where p-wave pairing fluctuations are dominant. Since the current experiments can only access the normal phase of a p-wave interacting Fermi gas, our results would be useful for experiments to understand strong-coupling properties of this Fermi system above Tc.

  13. Finite size effect on classical ideal gas revisited

    NASA Astrophysics Data System (ADS)

    Ghosh, P.; Ghosh, S.; Mitra, J.; Bera, N.

    2015-09-01

    Finite size effects on classical ideal gas are revisited. The micro-canonical partition function for a collection of ideal particles confined in a box is evaluated using Euler-Maclaurin’s as well as Poisson's summation formula. In Poisson's summation formula there are some exponential terms which are absent in Euler-Maclaurin’s formula. In the thermodynamic limit the exponential correction is negligibly small but in the macro/nano dimensions and at low temperatures they may have a great significance. The consequences of finite size effects have been illustrated by redoing the calculations in one and three dimensions keeping the exponential corrections. Global and local thermodynamic properties, diffusion driven by the finite size effect, and effect on speed of sound have been discussed. Thermo-size effects, similar to thermoelectric effects, have been described in detail and may be a theoretical basis with which to design nano-scaled devices. This paper can also be very helpful for undergraduate and graduate students in physics and chemistry as an instructive exercise for a good course in statistical mechanics.

  14. On the Stability of Vortices in an Ideal Gas

    NASA Astrophysics Data System (ADS)

    Leblanc, Stephane; Le Duc, Anne; Le Penven, Lionel

    Two distinct mechanisms of three-dimensional instability in compressible planar vortices in an ideal gas are presented. Both mechanisms have been obtained with the geometrical optics (WKB) stability theory which consists in studying the evolution of short-wavelength disturbances localized along the trajectories of the vortex. The first one corresponds to parametric resonances arising when a vortex is periodically compressed; the resulting instabilities are localized in the core of the vortex. On the contrary, in the second case, which corresponds to the generalization to compressible flows of the Rayleigh stability criterion for centrifugal instability, the growing perturbation surrounds the vortex at a given radius. In the latter case, the structure of the corresponding discrete eigenmodes may be described exactly, thus complementing and improving the WKB theory.

  15. A Novel Route to Reach a p-Wave Superfluid Fermi Gas

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Tokitake; Inotani, Daisuke; Ohashi, Yoji

    2017-01-01

    We theoretically propose an idea to realize a p-wave superfluid Fermi gas. To overcome the experimental difficulty that a p-wave pairing interaction to form p-wave Cooper pairs damages the system before the condensation growth, we first prepare a p-wave pair amplitude (Φp) in a spin-orbit coupled s-wave superfluid Fermi gas, without any p-wave interaction. Then, by suddenly changing the s-wave interaction with a p-wave one (Up) by using a Feshbach resonance, we reach the p-wave superfluid phase with the p-wave superfluid order parameter being symbolically written as Δp ˜ UpΦp. In this letter, we assess this scenario within the framework of a time-dependent Bogoliubov-de Gennes theory. Our results would contribute to the study toward the realization of unconventional pairing states in an ultracold Fermi gas.

  16. Emergence of a Metallic Quantum Solid Phase in a Rydberg-Dressed Fermi Gas.

    PubMed

    Li, Wei-Han; Hsieh, Tzu-Chi; Mou, Chung-Yu; Wang, Daw-Wei

    2016-07-15

    We examine possible low-temperature phases of a repulsively Rydberg-dressed Fermi gas in a three-dimensional free space. It is shown that the collective density excitations develop a roton minimum, which is softened at a wave vector smaller than the Fermi wave vector when the particle density is above a critical value. The mean field calculation shows that, unlike the insulating density wave states often observed in conventional condensed matters, a self-assembled metallic density wave state emerges at low temperatures. In particular, the density wave state supports a Fermi surface and a body-centered-cubic crystal order at the same time with the estimated critical temperature being about one tenth of the noninteracting Fermi energy. Our results suggest the emergence of a fermionic quantum solid that should be observable in the current experimental setup.

  17. Numerical solutions of ideal quantum gas dynamical flows governed by semiclassical ellipsoidal-statistical distribution.

    PubMed

    Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin

    2014-01-08

    The ideal quantum gas dynamics as manifested by the semiclassical ellipsoidal-statistical (ES) equilibrium distribution derived in Wu et al. (Wu et al. 2012 Proc. R. Soc. A468, 1799-1823 (doi:10.1098/rspa.2011.0673)) is numerically studied for particles of three statistics. This anisotropic ES equilibrium distribution was derived using the maximum entropy principle and conserves the mass, momentum and energy, but differs from the standard Fermi-Dirac or Bose-Einstein distribution. The present numerical method combines the discrete velocity (or momentum) ordinate method in momentum space and the high-resolution shock-capturing method in physical space. A decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. Computations of two-dimensional Riemann problems are presented, and various contours of the quantities unique to this ES model are illustrated. The main flow features, such as shock waves, expansion waves and slip lines and their complex nonlinear interactions, are depicted and found to be consistent with existing calculations for a classical gas.

  18. Chemical potential for the interacting classical gas and the ideal quantum gas obeying a generalized exclusion principle

    NASA Astrophysics Data System (ADS)

    Sevilla, F. J.; Olivares-Quiroz, L.

    2012-05-01

    In this work, we address the concept of the chemical potential μ in classical and quantum gases towards the calculation of the equation of state μ = μ(n, T) where n is the particle density and T the absolute temperature using the methods of equilibrium statistical mechanics. Two cases seldom discussed in elementary textbooks are presented with detailed calculations. The first one refers to the explicit calculation of μ for the interacting classical gas exemplified by van der Waals gas. For this purpose, we used the method described by van Kampen (1961 Physica 27 783). The second one refers to the calculation of μ for ideal quantum gases that obey a generalized Pauli's exclusion principle that leads to statistics that go beyond the Bose-Einstein and Fermi-Dirac cases. The audience targeted in this work corresponds mainly to advanced undergraduates and graduate students in the physical-chemical sciences but it is not restricted to them. In regard of this, we have put a special emphasis on showing some additional details of calculations that usually do not appear explicitly in textbooks.

  19. Condensate fraction of a two-dimensional attractive Fermi gas

    SciTech Connect

    Salasnich, Luca

    2007-07-15

    We investigate the Bose-Einstein condensation of fermionic pairs in a two-dimensional uniform two-component Fermi superfluid obtaining an explicit formula for the condensate density as a function of the chemical potential and the energy gap. By using the mean-field extended Bardeen-Cooper-Schrieffer theory, we analyze, as a function of the bound-state energy, the off-diagonal long-range order in the crossover from the Bardeen-Cooper-Schrieffer state of weakly bound Cooper pairs to the Bose-Einstein condensate of strongly-bound molecular dimers.

  20. Comparison between theory and experiment for universal thermodynamics of a homogeneous, strongly correlated Fermi gas

    SciTech Connect

    Hu Hui; Liu Xiaji; Drummond, Peter D.

    2011-06-15

    We compare the theoretical predictions for universal thermodynamics of a homogeneous, strongly correlated Fermi gas with the latest experimental measurements reported by the ENS group [S. Nascimbene et al., Nature (London) 463, 1057 (2010)] and the Tokyo group [M. Horikoshi et al., Science 327, 442 (2010)]. The theoretical results are obtained using two diagrammatic theories, together with a virial expansion theory combined with a Pade approximation. We find good agreement between theory and experiment. In particular, the virial expansion, using a Pade approximation up to third order, describes the experimental results extremely well down to the superfluid transition temperature, T{sub c{approx}}0.16T{sub F}, where T{sub F} is the Fermi temperature. The comparison in this work complements our previous comparative study on the universal thermodynamics of a strongly correlated but trapped Fermi gas. The comparison also raises interesting issues about the unitary entropy and the applicability of the Pade approximation.

  1. Large-scale behaviour of local and entanglement entropy of the free Fermi gas at any temperature

    NASA Astrophysics Data System (ADS)

    Leschke, Hajo; Sobolev, Alexander V.; Spitzer, Wolfgang

    2016-07-01

    The leading asymptotic large-scale behaviour of the spatially bipartite entanglement entropy (EE) of the free Fermi gas infinitely extended in multidimensional Euclidean space at zero absolute temperature, T = 0, is by now well understood. Here, we present and discuss the first rigorous results for the corresponding EE of thermal equilibrium states at T\\gt 0. The leading large-scale term of this thermal EE turns out to be twice the first-order finite-size correction to the infinite-volume thermal entropy (density). Not surprisingly, this correction is just the thermal entropy on the interface of the bipartition. However, it is given by a rather complicated integral derived from a semiclassical trace formula for a certain operator on the underlying one-particle Hilbert space. But in the zero-temperature limit T\\downarrow 0, the leading large-scale term of the thermal EE considerably simplifies and displays a {ln}(1/T)-singularity which one may identify with the known logarithmic enhancement at T = 0 of the so-called area-law scaling. birthday of the ideal Fermi gas.

  2. Monopole excitations of a harmonically trapped one-dimensional Bose gas from the ideal gas to the Tonks-Girardeau regime.

    PubMed

    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.

  3. On the ground state energy of the delta-function Fermi gas

    NASA Astrophysics Data System (ADS)

    Tracy, Craig A.; Widom, Harold

    2016-10-01

    The weak coupling asymptotics to order γ of the ground state energy of the delta-function Fermi gas, derived heuristically in the literature, is here made rigorous. Further asymptotics are in principle computable. The analysis applies to the Gaudin integral equation, a method previously used by one of the authors for the asymptotics of large Toeplitz matrices.

  4. Dynamical heterogeneity in a glass-forming ideal gas.

    PubMed

    Charbonneau, Patrick; Das, Chinmay; Frenkel, Daan

    2008-07-01

    We conduct a numerical study of the dynamical behavior of a system of three-dimensional "crosses," particles that consist of three mutually perpendicular line segments of length sigma rigidly joined at their midpoints. In an earlier study [W. van Ketel, Phys. Rev. Lett. 94, 135703 (2005)] we showed that this model has the structural properties of an ideal gas, yet the dynamical properties of a strong glass former. In the present paper we report an extensive study of the dynamical heterogeneities that appear in this system in the regime where glassy behavior sets in. On the one hand, we find that the propensity of a particle to diffuse is determined by the structure of its local environment. The local density around mobile particles is significantly less than the average density, but there is little clustering of mobile particles, and the clusters observed tend to be small. On the other hand, dynamical susceptibility results indicate that a large dynamical length scale develops even at moderate densities. This suggests that propensity and other mobility measures are an incomplete measure of the dynamical length scales in this system.

  5. From free expansion to abrupt compression of an ideal gas

    NASA Astrophysics Data System (ADS)

    Anacleto, Joaquim; Pereira, Mário G.

    2009-01-01

    Using macroscopic thermodynamics, the general law for adiabatic processes carried out by an ideal gas was studied. It was shown that the process reversibility is characterized by the adiabatic reversibility coefficient r, in the range 0 <= r <= 1 for expansions and r >= 1 for compressions. The particular cases of free expansion and reversible adiabatic processes correspond to r = 0 and r = 1, respectively. To conclude the interpretation of r, the relation between r and the variation of the system entropy was also obtained. Comparison between this study and one restricted to expansions following a microscopic point of view showed not only equivalent interpretations but also that our approach is more general, since it also comprises compressions, provides an objective relation between r and entropy change and considers instantaneous varying values of the adiabatic reversibility coefficient. Finally, simulations of selected adiabatic processes are performed and numerical calculations of r are presented. This paper is intended primarily for the undergraduate student, although a comparison with the aforementioned work also requires a background in thermodynamics and kinetic theory.

  6. Breathing modes of a fast rotating Fermi gas

    NASA Astrophysics Data System (ADS)

    Antezza, Mauro; Cozzini, Marco; Stringari, Sandro

    2007-05-01

    We derive the frequency spectrum of the lowest compressional oscillations of a three-dimensional harmonically trapped Fermi superfluid in the presence of a vortex lattice, treated in the diffused vorticity approximation within a hydrodynamic approach. We consider the general case of a superfluid at T=0 characterized by a polytropic equation of state (˜nγ) , which includes both the Bose-Einstein condensed regime of dimers (γ=1) and the unitary limit of infinite scattering length (γ=2/3) . Important limiting cases are considered, including the centrifugal limit, the isotropic trapping, and the cigar geometry. The conditions required to enter the lowest Landau level and quantum Hall regimes at unitarity are also discussed.

  7. Structure of a Quantized Vortex in Fermi Atom Gas

    SciTech Connect

    Machida, Masahiko; Koyama, Tomio

    2006-09-07

    In atomic Fermi gases, the pairing character changes from BCS-like to BEC-like when one decreases the threshold energy of the Feshbach resonance. With this crossover, the system enters the strong-coupling regime through the population enhancement of diatom molecules, and the vortex structure becomes much different from well-known core structures in BCS superfluid since the superfluid order parameter is given by a sum of BCS pairs and BEC molecular condensates. In this paper, we study the structure of a vortex by numerically solving the generalized Bogoliubov-de Gennes equation derived from the fermion-boson model and clarify how the vortex structure changes with the threshold energy of the Feshbach resonance. We find that the diatom boson condensate enhances the matter density depletion inside the vortex core and the discreteness of localized quasi-particle spectrum.

  8. Shock Waves in the BEC to BCS Crossover of a Fermi Gas

    NASA Astrophysics Data System (ADS)

    Baird, Lorin; Joseph, James; Thomas, John

    2016-05-01

    We observe shock waves in a Fermi gas near a Feshbach resonance, using a micro-mirror array to create a spatially controlled, blue-detuned, repulsive optical potential. We separate an optically-trapped gas of 6 Li into two clouds with steep density profiles. When the repulsive potential beam is extinguished, the two halves of the cloud collide in the optical trap, producing shock waves. Using in-situ imaging, we find that the steep density gradients associated with shockwaves are most pronounced near resonance and become less pronounced as the magnetic field is tuned above resonance to create a weakly interacting Fermi gas or below resonance to create a weakly interacting Bose gas of dimers. Using this method, we study the crossover from dispersive to dissipative non-linear hydrodynamics as a function of interaction strength and temperature. Funding by: NSF, DOE, ARO, and AFOSR.

  9. Phase separation in a polarized Fermi gas with spin-orbit coupling

    SciTech Connect

    Yi, W.; Guo, G.-C.

    2011-09-15

    We study the phase separation of a spin-polarized Fermi gas with spin-orbit coupling near a wide Feshbach resonance. As a result of the competition between spin-orbit coupling and population imbalance, the phase diagram for a uniform gas develops a rich structure of phase separation involving topologically nontrivial gapless superfluid states. We then demonstrate the phase separation induced by an external trapping potential and discuss the optimal parameter region for the experimental observation of the gapless superfluid phases.

  10. Universal relations for the two-dimensional spin-1/2 Fermi gas with contact interactions

    SciTech Connect

    Valiente, Manuel; Zinner, Nikolaj T.; Moelmer, Klaus

    2011-12-15

    We present universal relations for a two-dimensional Fermi gas with pairwise contact interactions. The derivation of these relations is made possible by obtaining the explicit form of a generalized function--selector--in the momentum representation. The selector implements the short-distance boundary condition between two fermions in a straightforward manner and leads to simple derivations of the universal relations, in the spirit of Tan's original method for the three-dimensional gas.

  11. Radio-Frequency Spectroscopy of a Strongly Interacting Two-Dimensional Fermi Gas

    SciTech Connect

    Froehlich, Bernd; Feld, Michael; Vogt, Enrico; Koschorreck, Marco; Koehl, Michael; Zwerger, Wilhelm

    2011-03-11

    We realize and study a strongly interacting two-component atomic Fermi gas confined to two dimensions in an optical lattice. Using radio-frequency spectroscopy we measure the interaction energy of the strongly interacting gas. We observe the confinement-induced Feshbach resonance on the attractive side of the 3D Feshbach resonance and find the existence of confinement-induced molecules in very good agreement with theoretical predictions.

  12. High School Forum. The Solution: "Derivation of the Ideal Gas Law."

    ERIC Educational Resources Information Center

    Herron, J. Dudley, Ed.

    1980-01-01

    Presents responses to an earlier report concerning a procedure for the derivation of the Ideal Gas Law from Charles', Boyle's, and other gas laws. Logic errors and solutions that work are discussed. (CS)

  13. High School Forum. The Solution: "Derivation of the Ideal Gas Law."

    ERIC Educational Resources Information Center

    Herron, J. Dudley, Ed.

    1980-01-01

    Presents responses to an earlier report concerning a procedure for the derivation of the Ideal Gas Law from Charles', Boyle's, and other gas laws. Logic errors and solutions that work are discussed. (CS)

  14. Quantum mixed phases of a two-dimensional polarized degenerate Fermi gas in an optical cavity.

    PubMed

    Feng, Yanlin; Zhang, Kuang; Fan, Jingtao; Mei, Feng; Chen, Gang; Jia, Suotang

    2017-09-05

    The coupling of ultracold fermions to a high-finesse optical cavity can result in novel many-body phenomena, and has attracted significant interests at present. Here we consider a realization of the Fermi-Dicke model with controllable parameters, based on a two-dimensional polarized degenerate Fermi gas coupled to an optical cavity. We analytically investigate the ground-state properties of such system under the mean-field approximation. We find the system can exhibit a rich phase diagram depending on the fermion-photon coupling strength and the atomic resonant frequency. Contrasting to the bosonic counterpart, a first-order quantum phase transition between the superradiant phase and the normal phase featuring two Fermi surfaces can occur for the weak atomic resonant frequency, and there is a unique mixed phase where this normal phase and the superradiant phase coexist. The experimental detection of our results is also discussed.

  15. Collective mode damping and viscosity in a 1D unitary Fermi gas

    NASA Astrophysics Data System (ADS)

    Punk, M.; Zwerger, W.

    2006-08-01

    We calculate the damping of the Bogoliubov Anderson mode in a one-dimensional (1D) two-component attractive Fermi gas for arbitrary coupling strength within a quantum hydrodynamic approach. Using the Bethe-ansatz solution of the 1D BCS-BEC crossover problem, we derive analytic results for the viscosity covering the full range from a Luther Emery liquid of weakly bound pairs to a Lieb Liniger gas of strongly bound bosonic dimers. At the unitarity point, the system is a Tonks Girardeau gas with a universal constant αζ = 0.38 in the viscosity ζ = αζplanck n for T = 0. For the trapped case, we calculate the Q-factor of the breathing mode and show that the damping provides a sensitive measure of temperature in 1D Fermi gases.

  16. Response Functions for the Two-Dimensional Ultracold Fermi Gas: Dynamical BCS Theory and Beyond

    NASA Astrophysics Data System (ADS)

    Vitali, Ettore; Shi, Hao; Qin, Mingpu; Zhang, Shiwei

    2017-08-01

    Response functions are central objects in physics. They provide crucial information about the behavior of physical systems, and they can be directly compared with scattering experiments involving particles such as neutrons or photons. Calculations of such functions starting from the many-body Hamiltonian of a physical system are challenging and extremely valuable. In this paper, we focus on the two-dimensional (2D) ultracold Fermi atomic gas which has been realized experimentally. We present an application of the dynamical BCS theory to obtain response functions for different regimes of interaction strengths in the 2D gas with zero-range attractive interaction. We also discuss auxiliary-field quantum Monte Carlo (AFQMC) methods for the calculation of imaginary time correlations in these dilute Fermi gas systems. Illustrative results are given and comparisons are made between AFQMC and dynamical BCS theory results to assess the accuracy of the latter.

  17. Ideal gas thermodynamic properties for the phenyl, phenoxy, and o-biphenyl radicals

    NASA Technical Reports Server (NTRS)

    Burcat, A.; Zeleznik, F. J.; Mcbride, B. J.

    1985-01-01

    Ideal gas thermodynamic properties of the phenyl and o-biphenyl radicals, their deuterated analogs and the phenoxy radical were calculated to 5000 K using estimated vibrational frequencies and structures. The ideal gas thermodynamic properties of benzene, biphenyl, their deuterated analogs and phenyl were also calculated.

  18. Propagation of second sound in a superfluid Fermi gas in the unitary limit

    SciTech Connect

    Arahata, Emiko; Nikuni, Tetsuro

    2009-10-15

    We study sound propagation in a uniform superfluid gas of Fermi atoms in the unitary limit. The existence of normal and superfluid components leads to appearance of two sound modes in the collisional regime, referred to as first and second sounds. The second sound is of particular interest as it is a clear signal of a superfluid component. Using Landau's two-fluid hydrodynamic theory, we calculate hydrodynamic sound velocities and these weights in the density response function. The latter is used to calculate the response to a sudden modification of the external potential generating pulse propagation. The amplitude of a pulse which is proportional to the weight in the response function is calculated, the basis of the approach of Nozieres and Schmitt-Rink for the BCS-BEC. We show that, in a superfluid Fermi gas at unitarity, the second-sound pulse is excited with an appreciate amplitude by density perturbations.

  19. Density-functional theory of the trapped two-dimensional Fermi gas in the unitary regime

    SciTech Connect

    Zyl, Brandon P. van; Need, Melodie; Hutchinson, D. A. W.

    2007-08-15

    A recent paper by T. Papenbrock [Phys. Rev. A 72, 041602(R) (2005)] suggests that a determination of the universal factor {xi}{sub 3D} for a harmonically trapped, unpolarized dilute Fermi gas in the unitary regime may be obtained within the framework of a simple density-functional theory (DFT). One of the key results of that work is an estimate for the universal factor {xi}{sub 3D}{approx_equal}0.54, which is within 20% of the generally accepted quantum Monte Carlo simulation value of {xi}{sub 3D}=0.44{+-}0.01. Motivated by this result, this report investigates the determination of the universal factor {xi}{sub 2D} for a two-dimensional trapped Fermi gas, and suggests that the simple DFT approach of Papenbrock provides an exact result of {xi}{sub 2D}=1 in two dimensions.

  20. Production of Long-Lived Ultracold LI2 Molecules from a Fermi Gas

    NASA Astrophysics Data System (ADS)

    Cubizolles, J.; Bourdel, T.; Kokkelmans, S. J. J. M. F.; Salomon, C.; Shlyapnikov, G. V.

    2004-12-01

    We create weakly-bound Li2 molecules from a degenerate two-component Fermi gas by sweeping a magnetic field across a Feshbach resonance. The atom-molecule transfer efficiency can reach 85 % and is studied as a function of magnetic field and initial temperature. The bosonic molecules remain trapped for 0.5s and their temperature is within a factor of two of the Bose-Einstein condensation temperature. A thermodynamical model reproduces qualitatively the experimental findings.

  1. Site-Resolved Imaging with the Fermi Gas Microscope

    NASA Astrophysics Data System (ADS)

    Huber, Florian Gerhard

    The recent development of quantum gas microscopy for bosonic rubidium atoms trapped in optical lattices has made it possible to study local structure and correlations in quantum many-body systems. Quantum gas microscopes are a perfect platform to perform quantum simulation of condensed matter systems, offering unprecedented control over both internal and external degrees of freedom at a single-site level. In this thesis, this technique is extended to fermionic particles, paving the way to fermionic quantum simulation, which emulate electrons in real solids. Our implementation uses lithium, the lightest atom amenable to laser cooling. The absolute timescales of dynamics in optical lattices are inversely proportional to the mass. Therefore, experiments are more than six times faster than for the only other fermionic alkali atom, potassium, and more then fourteen times faster than an equivalent rubidium experiment. Scattering and collecting a sufficient number of photons with our high-resolution imaging system requires continuous cooling of the atoms during the fluorescence imaging. The lack of a resolved excited hyperfine structure on the D2 line of lithium prevents efficient conventional sub-Doppler cooling. To address this challenge we have applied a Raman sideband cooling scheme and achieved the first site-resolved imaging of ultracold fermions in an optical lattice.

  2. Spectral zeta function and non-perturbative effects in ABJM Fermi-gas

    NASA Astrophysics Data System (ADS)

    Hatsuda, Yasuyuki

    2015-11-01

    The exact partition function in ABJM theory on three-sphere can be regarded as a canonical partition function of a non-interacting Fermi-gas with an unconventional Hamiltonian. All the information on the partition function is encoded in the discrete spectrum of this Hamiltonian. We explain how (quantum mechanical) non-perturbative corrections in the Fermi-gas system appear from a spectral consideration. Basic tools in our analysis are a Mellin-Barnes type integral representation and a spectral zeta function. From a consistency with known results, we conjecture that the spectral zeta function in the ABJM Fermi-gas has an infinite number of "non-perturbative" poles, which are invisible in the semi-classical expansion of the Planck constant. We observe that these poles indeed appear after summing up perturbative corrections. As a consequence, the perturbative resummation of the spectral zeta function causes non-perturbative corrections to the grand canonical partition function. We also present another example associated with a spectral problem in topological string theory. A conjectured non-perturbative free energy on the resolved conifold is successfully reproduced in this framework.

  3. Itinerant ferromagnetism in an interacting Fermi gas with mass imbalance

    NASA Astrophysics Data System (ADS)

    von Keyserlingk, C. W.; Conduit, G. J.

    2011-05-01

    We study the emergence of itinerant ferromagnetism in an ultracold atomic gas with a variable mass ratio between the up- and down-spin species. Mass imbalance breaks the SU(2) spin symmetry, leading to a modified Stoner criterion. We first elucidate the phase behavior in both the grand canonical and canonical ensembles. Second, we apply the formalism to a harmonic trap to demonstrate how a mass imbalance delivers unique experimental signatures of ferromagnetism. These could help future experiments to better identify the putative ferromagnetic state. Furthermore, we highlight how a mass imbalance suppresses the three-body loss processes that handicap the formation of a ferromagnetic state. Finally, we study the time-dependent formation of the ferromagnetic phase following a quench in the interaction strength.

  4. Itinerant ferromagnetism in an interacting Fermi gas with mass imbalance

    SciTech Connect

    Keyserlingk, C. W. von; Conduit, G. J.

    2011-05-15

    We study the emergence of itinerant ferromagnetism in an ultracold atomic gas with a variable mass ratio between the up- and down-spin species. Mass imbalance breaks the SU(2) spin symmetry, leading to a modified Stoner criterion. We first elucidate the phase behavior in both the grand canonical and canonical ensembles. Second, we apply the formalism to a harmonic trap to demonstrate how a mass imbalance delivers unique experimental signatures of ferromagnetism. These could help future experiments to better identify the putative ferromagnetic state. Furthermore, we highlight how a mass imbalance suppresses the three-body loss processes that handicap the formation of a ferromagnetic state. Finally, we study the time-dependent formation of the ferromagnetic phase following a quench in the interaction strength.

  5. Local Observation of Pair Condensation in a Fermi Gas at Unitarity

    NASA Astrophysics Data System (ADS)

    Lingham, M. G.; Fenech, K.; Hoinka, S.; Vale, C. J.

    2014-03-01

    We present measurements of the local (homogeneous) density-density response function of a Fermi gas at unitarity using spatially resolved Bragg spectroscopy. By analyzing the Bragg response across one axis of the cloud, we extract the response function for a uniform gas which shows a clear signature of the Bose-Einstein condensation of pairs of fermions when the local temperature drops below the superfluid transition temperature. The method we use for local measurement generalizes a scheme for obtaining the local pressure in a harmonically trapped cloud from the line density and can be adapted to provide any homogeneous parameter satisfying the local density approximation.

  6. Dynamics of a Highly-Degenerate Strongly-Interacting Fermi Gas

    NASA Astrophysics Data System (ADS)

    Thomas, J. E.; Hemmer, S. L.; Kinast, J. M.; Turlapov, A. V.; Gehm, M. E.; O'Hara, K. M.

    2004-12-01

    We use all-optical methods to produce a highly-degenerate, Fermi gas of 6Li atoms near a Feshbach resonance, where strong interactions are predicted. In this regime, the zero-energy scattering length is larger than the interparticle spacing, and both the mean field energy and the collision rate take on universal forms as a consequence of unitarity and many-body interactions. We observe strong interactions in the highly anisotropic expansion of the gas upon release from the trap and discuss the interpretation of the data in terms of collisional and superfluid hydrodynamics in the universal limit.

  7. Universality of the unitary Fermi gas: a few-body perspective

    NASA Astrophysics Data System (ADS)

    Levinsen, Jesper; Massignan, Pietro; Endo, Shimpei; Parish, Meera M.

    2017-04-01

    We revisit the properties of the two-component Fermi gas with short-range interactions in three dimensions, in the limit where the s-wave scattering length diverges. Such a unitary Fermi gas possesses universal thermodynamic and dynamical observables that are independent of any interaction length scale. Focusing on trapped systems of N fermions, where N≤slant 10, we investigate how well we can determine the zero-temperature behavior of the many-body system from published few-body data on the ground-state energy and the contact. For the unpolarized case, we find that the Bertsch parameters extracted from trapped few-body systems all lie within 15% of the established value. Furthermore, the few-body values for the contact are well within the range of values determined in the literature for the many-body system. In the limit of large spin polarization, we obtain a similar accuracy for the polaron energy, and we estimate the polaron’s effective mass from the dependence of its energy on N. We also compute an upper bound for the squared wave-function overlap between the unitary Fermi system and the non-interacting ground state, both for the trapped and uniform cases. This allows us to prove that the trapped unpolarized ground state at unitarity has zero overlap with its non-interacting counterpart in the many-body limit N\\to ∞ .

  8. Improving Students' Understanding of the Connections between the Concepts of Real-Gas Mixtures, Gas Ideal-Solutions, and Perfect-Gas Mixtures

    ERIC Educational Resources Information Center

    Privat, Romain; Jaubert, Jean-Noël; Moine, Edouard

    2016-01-01

    In many textbooks of chemical-engineering thermodynamics, a gas mixture obeying the fundamental law pV[subscript m] = RT is most often called ideal-gas mixture (in some rare cases, the term perfect-gas mixture can be found). These textbooks also define the fundamental concept of ideal solution which in theory, can be applied indifferently to…

  9. Improving Students' Understanding of the Connections between the Concepts of Real-Gas Mixtures, Gas Ideal-Solutions, and Perfect-Gas Mixtures

    ERIC Educational Resources Information Center

    Privat, Romain; Jaubert, Jean-Noël; Moine, Edouard

    2016-01-01

    In many textbooks of chemical-engineering thermodynamics, a gas mixture obeying the fundamental law pV[subscript m] = RT is most often called ideal-gas mixture (in some rare cases, the term perfect-gas mixture can be found). These textbooks also define the fundamental concept of ideal solution which in theory, can be applied indifferently to…

  10. The Ideal Gas and Real Gas Heat Capacity of Sodium Atoms

    NASA Astrophysics Data System (ADS)

    Biolsi, Louis

    2014-10-01

    The ideal gas heat capacity of sodium atoms in the vapor phase is calculated to high temperatures using statistical mechanics. Since there are, in principle, an infinite number of atomic energy levels, the partition function and the heat capacity will grow very large unless the summation over energy levels is constrained as temperature increases. At higher temperatures, the increasing size of the atoms, which is a consequence of the increased population of highly excited energy levels, is used as a mechanism for limiting the summation over energy levels. The "" and "Bethe" procedures for cutting off the summation over energy levels will be discussed, and the results obtained using the two methods will be compared. In addition, although experimental information is available about lower atomic energy levels and some theoretical calculations are available for excited energy levels, information is lacking for most individual atomic states associated with highly excited energy levels. A "fill" procedure for approximating the energy of the unknown states will be discussed. Sodium vapor will also be considered to be a real gas that obeys the virial equation of state. The first non-ideal term in the power series expansion of the heat capacity in terms of virial coefficients involves the second virial coefficient, . This depends on the interaction potential energy between two sodium atoms, i.e., the potential energy curves for the sodium dimer. Accurate interaction potential energies can be obtained from either experimental or theoretical information for the lowest ten electronic states of the sodium dimer. These are used to calculate for each state, and the averaged value of for all ten states is used to calculate the non-ideal contribution to the heat capacity of sodium atoms as a function of temperature.

  11. Itinerant ferromagnetism in a Fermi gas with contact interaction: Magnetic properties in a dilute Hubbard model

    SciTech Connect

    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.

  12. General coordinate invariance and conformal invariance in nonrelativistic physics: Unitary Fermi gas

    SciTech Connect

    Son, D.T.; Wingate, M. . E-mail: wingate@phys.washington.edu

    2006-01-15

    We show that the Lagrangian for interacting nonrelativistic particles can be coupled to an external gauge field and metric tensor in a way that exhibits a nonrelativistic version of general coordinate invariance. We explore the consequences of this invariance on the example of the degenerate Fermi gas at infinite scattering length, where conformal invariance also plays an important role. We find the most general effective Lagrangian consistent with both general coordinate and conformal invariance to leading and next-to-leading orders in the momentum expansion. At the leading order the Lagrangian contains one phenomenological constant and reproduces the results of the Thomas-Fermi theory and superfluid hydrodynamics. At the next-to-leading order there are two additional constants. We express various physical quantities through these constants.

  13. Anomalous conductance of a strongly interacting Fermi gas through a quantum point contact

    NASA Astrophysics Data System (ADS)

    Liu, Boyang; Zhai, Hui; Zhang, Shizhong

    2017-01-01

    In this work we study the particle conductance of a strongly interacting Fermi gas through a quantum point contact. With an atom-molecule two-channel model, we compute the contribution to particle conductance by both the fermionic atoms and the bosonic molecules using the Keldysh formalism. Focusing on the regime above the Fermi superfluid transition temperature, we find that the fermionic contribution to the conductance is reduced by interaction compared with the quantized value for the noninteracting case; while the bosonic contribution to the conductance exhibits a plateau with nonuniversal values that is larger than the quantized conductance. This feature is particularly profound at temperature close to the superfluid transition. We emphasize that the enhanced conductance arises because of the bosonic nature of closed channel molecules and the low dimensionality of the quantum point contact.

  14. Fluctuation theorem for entropy production during effusion of a relativistic ideal gas.

    PubMed

    Cleuren, B; Willaert, K; Engel, A; Van den Broeck, C

    2008-02-01

    The probability distribution of the entropy production for the effusion of a relativistic ideal gas is calculated explicitly. This result is then extended to include particle and antiparticle pair production and annihilation. In both cases, the fluctuation theorem is verified.

  15. 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.

  16. Statistical simulation of the flow of an ideal monatomic gas

    NASA Astrophysics Data System (ADS)

    Belotserkovskii, O. M.; Ianitskii, V. E.

    1980-06-01

    The particle in cell method is an effective tool for solving the Eular and Navier-Stokes equations. In the present paper, an attempt is made to use the ideas of this method to solve problems of rarefied gas dynamics. A statistical version of the particle in cell method is developed for calculating spatially inhomogeneous and unsteady rarefied monatomic gas streams. The approach proposed is shown to be just as effective as Bird's (1970) method, but to provide a better approximation of the Boltzmann equation.

  17. Real-gas effects 1: Simulation of ideal gas flow by cryogenic nitrogen and other selected gases

    NASA Technical Reports Server (NTRS)

    Hall, R. M.

    1980-01-01

    The thermodynamic properties of nitrogen gas do not thermodynamically approximate an ideal, diatomic gas at cryogenic temperatures. Choice of a suitable equation of state to model its behavior is discussed and the equation of Beattie and Bridgeman is selected as best meeting the needs for cryogenic wind tunnel use. The real gas behavior of nitrogen gas is compared to an ideal, diatomic gas for the following flow processes: isentropic expansion; normal shocks; boundary layers; and shock wave boundary layer interactions. The only differences in predicted pressure ratio between nitrogen and an ideal gas that may limit the minimum operating temperatures of transonic cryogenic wind tunnels seem to occur at total pressures approaching 9atmospheres and total temperatures 10 K below the corresponding saturation temperature, where the differences approach 1 percent for both isentropic expansions and normal shocks. Several alternative cryogenic test gases - air, helium, and hydrogen - are also analyzed. Differences in air from an ideal, diatomic gas are similar in magnitude to those of nitrogen. Differences for helium and hydrogen are over an order of magnitude greater than those for nitrogen or air. Helium and hydrogen do not approximate the compressible flow of an ideal, diatomic gas.

  18. Real-gas effects 1: Simulation of ideal gas flow by cryogenic nitrogen and other selected gases

    NASA Technical Reports Server (NTRS)

    Hall, R. M.

    1980-01-01

    The thermodynamic properties of nitrogen gas do not thermodynamically approximate an ideal, diatomic gas at cryogenic temperatures. Choice of a suitable equation of state to model its behavior is discussed and the equation of Beattie and Bridgeman is selected as best meeting the needs for cryogenic wind tunnel use. The real gas behavior of nitrogen gas is compared to an ideal, diatomic gas for the following flow processes: isentropic expansion; normal shocks; boundary layers; and shock wave boundary layer interactions. The only differences in predicted pressure ratio between nitrogen and an ideal gas that may limit the minimum operating temperatures of transonic cryogenic wind tunnels seem to occur at total pressures approaching 9atmospheres and total temperatures 10 K below the corresponding saturation temperature, where the differences approach 1 percent for both isentropic expansions and normal shocks. Several alternative cryogenic test gases - air, helium, and hydrogen - are also analyzed. Differences in air from an ideal, diatomic gas are similar in magnitude to those of nitrogen. Differences for helium and hydrogen are over an order of magnitude greater than those for nitrogen or air. Helium and hydrogen do not approximate the compressible flow of an ideal, diatomic gas.

  19. Getting Pumped Up on the Ideal Gas Law

    NASA Astrophysics Data System (ADS)

    Houser, Jolene; Johnson, Doug; Siegel, Peter

    2002-10-01

    An experiment is described in which the pressure P and the number of moles n of a gas are varied. Using common materials, the student can verify that P is proportional to n when the volume and temperature are held constant.

  20. Anomalous heat conduction in a one-dimensional ideal gas.

    PubMed

    Casati, Giulio; Prosen, Tomaz

    2003-01-01

    We provide firm convincing evidence that the energy transport in a one-dimensional gas of elastically colliding free particles of unequal masses is anomalous, i.e., the Fourier law does not hold. Our conclusions are confirmed by a theoretical and numerical analysis based on a Green-Kubo-type approach specialized to momentum-conserving lattices.

  1. Fermi-edge superfluorescence from a quantum-degenerate electron-hole gas

    PubMed Central

    Kim, Ji-Hee; II, G. Timothy Noe; McGill, Stephen A.; Wang, Yongrui; Wójcik, Aleksander K.; Belyanin, Alexey A.; Kono, Junichiro

    2013-01-01

    Nonequilibrium can be a source of order. This rather counterintuitive statement has been proven to be true through a variety of fluctuation-driven, self-organization behaviors exhibited by out-of-equilibrium, many-body systems in nature (physical, chemical, and biological), resulting in the spontaneous appearance of macroscopic coherence. Here, we report on the observation of spontaneous bursts of coherent radiation from a quantum-degenerate gas of nonequilibrium electron-hole pairs in semiconductor quantum wells. Unlike typical spontaneous emission from semiconductors, which occurs at the band edge, the observed emission occurs at the quasi-Fermi edge of the carrier distribution. As the carriers are consumed by recombination, the quasi-Fermi energy goes down toward the band edge, and we observe a continuously red-shifting streak. We interpret this emission as cooperative spontaneous recombination of electron-hole pairs, or superfluorescence (SF), which is enhanced by Coulomb interactions near the Fermi edge. This novel many-body enhancement allows the magnitude of the spontaneously developed macroscopic polarization to exceed the maximum value for ordinary SF, making electron-hole SF even more “super” than atomic SF. PMID:24257510

  2. Leaky Fermi accelerators.

    PubMed

    Shah, Kushal; Gelfreich, Vassili; Rom-Kedar, Vered; Turaev, Dmitry

    2015-06-01

    A Fermi accelerator is a billiard with oscillating walls. A leaky accelerator interacts with an environment of an ideal gas at equilibrium by exchange of particles through a small hole on its boundary. Such interaction may heat the gas: we estimate the net energy flow through the hole under the assumption that the particles inside the billiard do not collide with each other and remain in the accelerator for a sufficiently long time. The heat production is found to depend strongly on the type of Fermi accelerator. An ergodic accelerator, i.e., one that has a single ergodic component, produces a weaker energy flow than a multicomponent accelerator. Specifically, in the ergodic case the energy gain is independent of the hole size, whereas in the multicomponent case the energy flow may be significantly increased by shrinking the hole size.

  3. Low-temperature thermodynamics of the unitary Fermi gas: Superfluid fraction, first sound, and second sound

    SciTech Connect

    Salasnich, Luca

    2010-12-15

    We investigate the low-temperature thermodynamics of the unitary Fermi gas by introducing a model based on the zero-temperature spectra of both bosonic collective modes and fermonic single-particle excitations. We calculate the Helmholtz free energy and from it we obtain the entropy, the internal energy, and the chemical potential as a function of the temperature. By using these quantities and the Landau's expression for the superfluid density we determine analytically the superfluid fraction, the critical temperature, the first sound velocity, and the second sound velocity. We compare our analytical results with other theoretical predictions and experimental data of ultracold atoms and dilute neutron matter.

  4. Observation of ShockWaves in a Strongly Interacting Fermi Gas

    SciTech Connect

    Kulkarni, M.; Joseph, J.A.; Thomas, J.E.; Abanov, A.G.

    2011-04-11

    We study collisions between two strongly interacting atomic Fermi gas clouds. We observe exotic nonlinear hydrodynamic behavior, distinguished by the formation of a very sharp and stable density peak as the clouds collide and subsequent evolution into a boxlike shape. We model the nonlinear dynamics of these collisions by using quasi-1D hydrodynamic equations. Our simulations of the time-dependent density profiles agree very well with the data and provide clear evidence of shock wave formation in this universal quantum hydrodynamic system.

  5. Symmetry-Broken Phase Separation of a Two-Component Dipolar Fermi Gas in a Spherically Symmetric Harmonic Trap

    NASA Astrophysics Data System (ADS)

    Miyakawa, Takahiko; Nakamura, Shin; Yabu, Hiroyuki

    2017-03-01

    We study the ground state of a two-component dipolar Fermi gas in a spherically symmetric harmonic trap at zero temperature. On the basis of the Thomas-Fermi-von Weizsäcker approximation, we obtain a phase diagram of the system with equal but opposite values of the magnetic moment. We find that a phase-separated state, which spontaneously breaks the spherical symmetry of the system, emerges.

  6. Investigation of the non-relativistic fermi-gas model by considering the position-dependent mass

    NASA Astrophysics Data System (ADS)

    Zare, S.; de Montigny, M.; Hassanabadi, H.

    2017-01-01

    We investigate the Schrödinger equation in the position-dependent mass framework with an infinite square well potential. We apply this approach to a Fermi gas, calculate the density of states of the gas, examine the information entropy, some expectation values and the uncertainty principle.

  7. Observation of a pairing pseudogap in a two-dimensional Fermi gas.

    PubMed

    Feld, Michael; Fröhlich, Bernd; Vogt, Enrico; Koschorreck, Marco; Köhl, Michael

    2011-11-30

    Pairing of fermions is ubiquitous in nature, underlying many phenomena. Examples include superconductivity, superfluidity of (3)He, the anomalous rotation of neutron stars, and the crossover between Bose-Einstein condensation of dimers and the BCS (Bardeen, Cooper and Schrieffer) regime in strongly interacting Fermi gases. When confined to two dimensions, interacting many-body systems show even more subtle effects, many of which are not understood at a fundamental level. Most striking is the (as yet unexplained) phenomenon of high-temperature superconductivity in copper oxides, which is intimately related to the two-dimensional geometry of the crystal structure. In particular, it is not understood how the many-body pairing is established at high temperature, and whether it precedes superconductivity. Here we report the observation of a many-body pairing gap above the superfluid transition temperature in a harmonically trapped, two-dimensional atomic Fermi gas in the regime of strong coupling. Our measurements of the spectral function of the gas are performed using momentum-resolved photoemission spectroscopy, analogous to angle-resolved photoemission spectroscopy in the solid state. Our observations mark a significant step in the emulation of layered two-dimensional strongly correlated superconductors using ultracold atomic gases.

  8. Large-momentum distribution of a polarized Fermi gas and p -wave contacts

    NASA Astrophysics Data System (ADS)

    Peng, Shi-Guo; Liu, Xia-Ji; Hu, Hui

    2016-12-01

    We present a derivation of the adiabatic energy relations as well as the large momentum distribution of a polarized Fermi gas near p -wave Feshbach resonances. The leading asymptotic behavior k-2 and subleading behavior k-4 of the large momentum distribution have recently been predicted by Z. Yu et al. [Phys. Rev. Lett. 115, 135304 (2015), 10.1103/PhysRevLett.115.135304] and by M. Y. He et al. [Phys. Rev. Lett. 116, 045301 (2016), 10.1103/PhysRevLett.116.045301] using two different approaches. Here, we show that the subleading asymptotic behavior (˜k-4 ) cannot fully be captured by the contact defined from the adiabatic energy relation related to the p -wave effective range, and there should be an extra term resulting from the center-of-mass motion of the pairs. The omission of this extra term is perhaps a reasonable approximation at zero temperature. However, it should be taken into account at finite temperature and should have significant importance to understand the recently measured momentum distribution in a resonant p -wave Fermi gas of ultracold 40K atoms [C. Luciuk et al., Nat. Phys. 12, 599 (2016), 10.1038/nphys3670].

  9. One-dimensional repulsive Fermi gas in a tunable periodic potential

    NASA Astrophysics Data System (ADS)

    Pilati, Sebastiano; Barbiero, Luca; Fazio, Rosario; Dell'Anna, Luca

    2017-08-01

    By using unbiased continuous-space quantum Monte Carlo simulations, we investigate the ground-state properties of a one-dimensional repulsive Fermi gas subjected to a commensurate periodic optical lattice (OL) of arbitrary intensity. The equation of state and the magnetic structure factor are determined as a function of the interaction strength and of the OL intensity. In the weak OL limit, Yang's theory for the energy of a homogeneous Fermi gas [C.-N. Yang, Phys. Rev. Lett. 19, 1312 (1967), 10.1103/PhysRevLett.19.1312] is recovered. In the opposite limit (deep OL), we analyze the convergence to the Lieb-Wu theory for the Hubbard model [E. H. Lieb and F. Y. Wu, Phys. Rev. Lett. 20, 1445 (1968), 10.1103/PhysRevLett.20.1445], comparing two approaches to map the continuous space to the discrete-lattice model: The first is based on (noninteracting) Wannier functions and the second effectively takes into account strong-interaction effects within a parabolic approximation of the OL wells. We find that strong antiferromagnetic correlations emerge in deep OLs and also in very shallow OLs if the interaction strength approaches the Tonks-Girardeau limit. In deep OLs we find quantitative agreement with density-matrix renormalization-group calculations for the Hubbard model. The spatial decay of the antiferromagnetic correlations is consistent with quasi-long-range order even in shallow OLs, in agreement with previous theories for the half-filled Hubbard model.

  10. Strongly interacting p -wave Fermi gas in two dimensions: Universal relations and breathing mode

    NASA Astrophysics Data System (ADS)

    Zhang, Yi-Cai; Zhang, Shizhong

    2017-02-01

    The contact is an important concept that characterizes the universal properties of a strongly interacting quantum gas. It appears in both thermodynamic (energy, pressure, etc.) and dynamic quantities (radio-frequency and Bragg spectroscopies, etc.) of the system. Very recently, the concept of contact was extended to higher partial waves; in particular, the p -wave contacts have been experimentally probed in recent experiments. So far, discussions on p -wave contacts have been limited to three dimensions. In this paper, we generalize the p -wave contacts to two dimensions and derive a series of universal relations, including the adiabatic relations, high-momentum distribution, virial theorem, and pressure relation. At the high-temperature and low-density limit, we calculate the p -wave contacts explicitly using virial expansion. A formula which directly connects the shift of the breathing-mode frequency and the p -wave contacts is given in a harmonically trapped system. Finally, we also derive the relationships between interaction parameters in three- and two-dimensional Fermi gases and discuss possible experimental realization of a two-dimensional Fermi gas with p -wave interactions.

  11. Ferromagnetic transition in harmonically trapped Fermi gas with higher partial-wave interactions

    NASA Astrophysics Data System (ADS)

    Sun, Zongli; Gu, Qiang

    2017-01-01

    Spontaneous ferromagnetic transition in trapped Fermi gas is studied in the presence of a higher partial-wave interaction. At the mean-field level, the ground-state energy contribution from an arbitrary partial wave is derived, with which the equilibrium density profile of each spin component can be calculated. Our results show that, in the spin-\\tfrac{1}{2} Fermi gas, the individual repulsive d-wave interaction can induce ferromagnetic transition; while the individual repulsive or attractive p- and f-wave interactions fail. In addition, the higher partial waves can have a remarkable influence on the ferromagnetic phase induced by the s-wave interaction. The repulsive d-wave interaction and attractive p- or f-wave interactions lower the s-wave Stoner point and critical particle number, while the attractive d-wave interaction and repulsive p- or f-wave interactions increase them. In addition, our results also show that both repulsive d-wave interaction and attractive p- or f-wave interactions can enhance the ferromagnetic state induced by s-wave interaction.

  12. High-temperature behavior of a deformed Fermi gas obeying interpolating statistics

    NASA Astrophysics Data System (ADS)

    Algin, Abdullah; Senay, Mustafa

    2012-04-01

    An outstanding idea originally introduced by Greenberg is to investigate whether there is equivalence between intermediate statistics, which may be different from anyonic statistics, and q-deformed particle algebra. Also, a model to be studied for addressing such an idea could possibly provide us some new consequences about the interactions of particles as well as their internal structures. Motivated mainly by this idea, in this work, we consider a q-deformed Fermi gas model whose statistical properties enable us to effectively study interpolating statistics. Starting with a generalized Fermi-Dirac distribution function, we derive several thermostatistical functions of a gas of these deformed fermions in the thermodynamical limit. We study the high-temperature behavior of the system by analyzing the effects of q deformation on the most important thermostatistical characteristics of the system such as the entropy, specific heat, and equation of state. It is shown that such a deformed fermion model in two and three spatial dimensions exhibits the interpolating statistics in a specific interval of the model deformation parameter 0 < q < 1. In particular, for two and three spatial dimensions, it is found from the behavior of the third virial coefficient of the model that the deformation parameter q interpolates completely between attractive and repulsive systems, including the free boson and fermion cases. From the results obtained in this work, we conclude that such a model could provide much physical insight into some interacting theories of fermions, and could be useful to further study the particle systems with intermediate statistics.

  13. Larkin-Ovchinnikov superfluidity in a two-dimensional imbalanced atomic Fermi gas

    NASA Astrophysics Data System (ADS)

    Toniolo, Umberto; Mulkerin, Brendan; Liu, Xia-Ji; Hu, Hui

    2017-01-01

    We present an extensive study of two-dimensional Larkin-Ovchinnikov (LO) superfluidity in a spin-imbalanced two-component atomic Fermi gas. In the context of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) phase, we explore a wide and generic class of pairing gap functions with explicit spatial dependency. The mean-field theory of such phases is applied through the Bogoliubov-de Gennes equations in which the pairing gap can be determined self-consistently. To systematically explore the configuration space we consider both the canonical and grand canonical ensembles where we control the polarization or chemical potentials of the system, respectively. The mean-field calculations enable us to understand the nature of the phase transitions in the fully paired Bardeen-Cooper-Schrieffer (BCS) state, exotic LO phase, and partially polarized free Fermi gas (NPP). The order of the phase transitions has been examined and, in particular, we find a weak first-order phase transition between the exotic inhomogeneous LO phase and the BCS phase. In comparison to the three-dimensional case, where the phase diagram is dominated by a generic separation phase, we predict a broader parameter space for the spatially inhomogeneous LO phase. By computing the superfluid density of the LO phase at different polarization, we show how the superfluidity of the system is suppressed with increasing spin polarization.

  14. 1D to 3D Crossover of a Spin-Imbalanced Fermi Gas

    NASA Astrophysics Data System (ADS)

    Revelle, Melissa C.; Fry, Jacob A.; Olsen, Ben A.; Hulet, Randall G.

    2016-12-01

    We have characterized the one-dimensional (1D) to three-dimensional (3D) crossover of a two-component spin-imbalanced Fermi gas of 6Li atoms in a 2D optical lattice by varying the lattice tunneling and the interactions. The gas phase separates, and we detect the phase boundaries using in situ imaging of the inhomogeneous density profiles. The locations of the phases are inverted in 1D as compared to 3D, thus providing a clear signature of the crossover. By scaling the tunneling rate t with respect to the pair binding energy ɛB, we observe a collapse of the data to a universal crossover point at a scaled tunneling value of t˜c=0.025 (7 ).

  15. Itinerant ferromagnetism of a repulsive atomic Fermi gas: a quantum monte carlo study.

    PubMed

    Pilati, S; Bertaina, G; Giorgini, S; Troyer, M

    2010-07-16

    We investigate the phase diagram of a two-component repulsive Fermi gas at T=0 by means of quantum Monte Carlo simulations. Both purely repulsive and resonant attractive model potentials are considered in order to analyze the limits of the universal regime where the details of interatomic forces can be neglected. The equation of state of both balanced and unbalanced systems is calculated as a function of the interaction strength and the critical density for the onset of ferromagnetism is determined. The energy of the strongly polarized gas is calculated and parametrized in terms of the physical properties of repulsive polarons, which are relevant for the stability of the fully ferromagnetic state. Finally, we analyze the phase diagram in the interaction-polarization plane under the assumption that only phases with homogeneous magnetization can be produced.

  16. Molecule and polaron in a highly polarized two-dimensional fermi gas with spin-orbit coupling.

    PubMed

    Yi, Wei; Zhang, Wei

    2012-10-05

    We show that spin-orbit coupling (SOC) gives rise to pairing instability in a highly polarized two-dimensional Fermi gas for an arbitrary interaction strength. The pairing instability can lead to a Fulde-Ferrell-Larkin-Ovchinnikov-like molecular state, which undergoes a first-order transition into a pairing state with zero center-of-mass momentum as the parameters are tuned. These pairing states are metastable against a polaron state dressed by particle-hole fluctuations for small SOC. At large SOC, a polaron-molecule transition exists, which suggests a phase transition between the topological superfluid state and the normal state for a highly polarized Fermi gas in the thermodynamic limit. As polarization in a Fermi gas with SOC is induced by the effective Zeeman field, we also discuss the influences of the effective Zeeman field on the ground state of the system. Our findings may be tested directly in future experiments.

  17. Specific Heat of Ultracold Fermi Gas with a Uniaxially Anisotropic p-Wave Interaction at the Superfluid Transition Temperature

    NASA Astrophysics Data System (ADS)

    Inotani, D.; van Wyk, P.; Ohashi, Y.

    2017-06-01

    We theoretically investigate the specific heat at constant volume C_V and strong-coupling effects in a Fermi gas with p-wave interaction. In a ^{40}K Fermi gas, a uniaxial anisotropy of a p-wave interaction associated with a p-wave Feshbach resonance is expected as a result of the split of the p-wave Feshbach resonance by a dipole interaction. Including this, as well as pairing fluctuations, we show that C_V is significantly affected by this anisotropy in the strong-coupling regime. We also discuss the physical origin of this effect. Our results would contribute to the further understanding of an ultracold p-wave Fermi gas.

  18. A Unified Theory of Non-Ideal Gas Lattice Boltzmann Models

    NASA Technical Reports Server (NTRS)

    Luo, Li-Shi

    1998-01-01

    A non-ideal gas lattice Boltzmann model is directly derived, in an a priori fashion, from the Enskog equation for dense gases. The model is rigorously obtained by a systematic procedure to discretize the Enskog equation (in the presence of an external force) in both phase space and time. The lattice Boltzmann model derived here is thermodynamically consistent and is free of the defects which exist in previous lattice Boltzmann models for non-ideal gases. The existing lattice Boltzmann models for non-ideal gases are analyzed and compared with the model derived here.

  19. Universal High-Momentum Asymptote and Thermodynamic Relations in a Spinless Fermi Gas with a Resonant p -Wave Interaction

    NASA Astrophysics Data System (ADS)

    Yoshida, Shuhei M.; Ueda, Masahito

    2015-09-01

    We investigate universal relations in a spinless Fermi gas near a p -wave Feshbach resonance, and show that the momentum distribution nk has an asymptote proportional to k-2 with the proportionality constant—the p -wave contact—scaling with the number of closed-channel molecules. We prove the adiabatic sweep theorem for a p -wave resonance which reveals the thermodynamic implication of the p -wave contact. In contrast to the unitary Fermi gas in which Tan's contact is universal, the p -wave contact depends on the short-range details of the interaction.

  20. How do quantum numbers generally vary in the adiabatic transformation of an ideal gas?

    NASA Astrophysics Data System (ADS)

    Yarman, T.; L. Kholmetskii, A.

    2011-10-01

    We continue to analyse the known law of adiabatic transformation for an ideal gas PV5/3 = Constant, where P is the pressure and V is the volume, and following the approach of non-relativistic quantum mechanics which we suggested in a previous work (Yarman et al. 2010 Int. J. Phys. Sci. 5 1524). We explicitly determine the constant for the general parallelepiped geometry of a container. We also disclose how the quantum numbers associated with molecules of an ideal gas vary through an arbitrary adiabatic transformation. Physical implications of the results obtained are discussed.

  1. Thermodynamic properties of the polarized ideal gas in the presence of a minimal length

    NASA Astrophysics Data System (ADS)

    Khosropour, B.

    2017-07-01

    In this work, we attempt to investigate the effect of minimal length on the thermodynamic properties of a polarized ideal gas. The modified electric field in three spatial dimensions based on the Kempf algebra is obtained. The modifications of the thermodynamic parameters of the polarized ideal gas such as the mean energy and entropy are found. Also, we obtain the polarization and dielectric constant in the presence of a minimal length. By considering the values of experimental characteristics, the upper bound on the deformation parameter is estimated.

  2. Low temperatures shear viscosity of a two-component dipolar Fermi gas with unequal population

    NASA Astrophysics Data System (ADS)

    Darsheshdar, E.; Yavari, H.; Zangeneh, Z.

    2016-07-01

    By using the Green's functions method and linear response theory we calculate the shear viscosity of a two-component dipolar Fermi gas with population imbalance (spin polarized) in the low temperatures limit. In the strong-coupling Bose-Einstein condensation (BEC) region where a Feshbach resonance gives rise to tightly bound dimer molecules, a spin-polarized Fermi superfluid reduces to a simple Bose-Fermi mixture of Bose-condensed dimers and the leftover unpaired fermions (atoms). The interactions between dimer-atom, dimer-dimer, and atom-atom take into account to the viscous relaxation time (τη) . By evaluating the self-energies in the ladder approximation we determine the relaxation times due to dimer-atom (τDA) , dimer-dimer (τcDD ,τdDD) , and atom-atom (τAA) interactions. We will show that relaxation rates due to these interactions τDA-1 ,τcDD-1, τdDD-1, and τAA-1 have T2, T4, e - E /kB T (E is the spectrum of the dimer atoms), and T 3 / 2 behavior respectively in the low temperature limit (T → 0) and consequently, the atom-atom interaction plays the dominant role in the shear viscosity in this rang of temperatures. For small polarization (τDA ,τAA ≫τcDD ,τdDD), the low temperatures shear viscosity is determined by contact interaction between dimers and the shear viscosity varies as T-5 which has the same behavior as the viscosity of other superfluid systems such as superfluid neutron stars, and liquid helium.

  3. Observation of hydrodynamic expansion in a strongly-interacting Fermi gas: Signature of superfluidity?

    NASA Astrophysics Data System (ADS)

    O'Hara, K. M.; Hemmer, S. L.; Gehm, M. E.; Thomas, J. E.

    2003-05-01

    Atomic Fermi gases with magnetically tunable, strong interactions provide a desktop laboratory for exploring new nonperturbative theories in systems ranging from superconductors to neutron stars. We use all-optical methods to produce a highly degenerate, two-component gas of ^6Li atoms in an applied magnetic field (910 G) near a Feshbach resonance where strong interactions are observed [1]. The s-wave scattering length is estimated to be a_S=-10^4 a_0, which is large compared to the interparticle spacing. Exciting new predictions for this regime include unitarity-limited universal interactions [2] and the onset of resonance superfluidity at a very high transition temperature [3-5]. Forced evaporation is accomplished by lowering the trap laser intensity over a period of 3.5 seconds and then recompressing the trap to full depth. Abrupt release of the cloud at 910 G results in a highly anisotropic expansion, where the gas expands rapidly in the transverse directions while remaining nearly stationary in the axial direction [1]. This anisotropic energy release has been predicted recently to be a signature of superfluidity in a Fermi gas [6]. We will discuss interpretations of the data in terms of superfluidity and unitarity-limited collision dynamics. References 1. K. M. O'Hara et al., Science, 298, 2179 (2002). 2. H. Heiselberg, Phys. Rev. A 63, 043606 (2001). 3. M. Holland, et al., Phys. Rev. Lett. 87, 120406 (2001). 4. E. Timmermans, et al., Phys. Lett. A 285, 228 (2001). 5. Y. Ohashi and A. Griffin, Phys. Rev. Lett. 89, 130402 (2002). 6. C. Menotti, et al., Phys. Rev. Lett. 89, 250402 (2002).

  4. Strong-coupling ansatz for the one-dimensional Fermi gas in a harmonic potential

    PubMed Central

    Levinsen, Jesper; Massignan, Pietro; Bruun, Georg M.; Parish, Meera M.

    2015-01-01

    A major challenge in modern physics is to accurately describe strongly interacting quantum many-body systems. One-dimensional systems provide fundamental insights because they are often amenable to exact methods. However, no exact solution is known for the experimentally relevant case of external confinement. We propose a powerful ansatz for the one-dimensional Fermi gas in a harmonic potential near the limit of infinite short-range repulsion. For the case of a single impurity in a Fermi sea, we show that our ansatz is indistinguishable from numerically exact results in both the few- and many-body limits. We furthermore derive an effective Heisenberg spin-chain model corresponding to our ansatz, valid for any spin-mixture, within which we obtain the impurity eigenstates analytically. In particular, the classical Pascal’s triangle emerges in the expression for the ground-state wave function. As well as providing an important benchmark for strongly correlated physics, our results are relevant for emerging quantum technologies, where a precise knowledge of one-dimensional quantum states is paramount. PMID:26601220

  5. 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.

  6. Correlations in the low-density Fermi gas: Fermi-liquid state, dimerization, and Bardeen-Cooper-Schrieffer pairing

    NASA Astrophysics Data System (ADS)

    Fan, H. H.; Krotscheck, E.; Lichtenegger, T.; Mateo, D.; Zillich, R. E.

    2015-08-01

    We present ground-state calculations for low-density Fermi gases described by two model interactions, an attractive square-well potential and a Lennard-Jones potential, of varying strength. We use the optimized Fermi-hypernetted chain integral equation method, which has been proved to provide, in the density regimes of interest here, an accuracy of better than 1%. We first examine the low-density expansion of the energy and compare it with the exact answer of H. Huang and C. N. Yang [Phys. Rev. 105, 767 (1957), 10.1103/PhysRev.105.767]. It is shown that a locally correlated wave function of the Jastrow-Feenberg type does not recover the quadratic term in the expansion of the energy in powers of a0kF , where a0 is the vacuum s -wave scattering length and kF the Fermi wave number. The problem is cured by adding second-order perturbation corrections in a correlated basis. Going to higher densities and/or more strongly coupled systems, we encounter an instability of the normal state of the system which is characterized by a divergence of the in-medium scattering length. We interpret this divergence as a phonon-exchange-driven dimerization of the system, similar to what occurs at zero density when the vacuum scattering length a0 diverges. We then study, in the stable regime, the superfluid gap and its dependence on the density and the interaction strength. We identify two corrections to low-density expansions: One is medium corrections to the pairing interaction, and the other is finite-range corrections. We show that the most important finite-range corrections are a direct manifestation of the many-body nature of the system.

  7. The Interaction of the Fermi Bubbles with the Milky Way’s Hot Gas Halo

    NASA Astrophysics Data System (ADS)

    Miller, Matthew J.; Bregman, Joel N.

    2016-09-01

    The Fermi bubbles are two lobes filled with non-thermal particles that emit gamma rays, extend ≈ 10 {{kpc}} vertically from the Galactic center, and formed from either nuclear star formation or accretion activity on Sgr A*. Simulations predict a range of shock strengths as the bubbles expand into the surrounding hot gas halo ({T}{halo}≈ 2× {10}6 K), but with significant uncertainties in the energetics, age, and thermal gas structure. The bubbles should contain thermal gas with temperatures between 106 and 108 K, with potential X-ray signatures. In this work, we constrain the bubbles’ thermal gas structure by modeling O vii and O viii emission line strengths from archival XMM-Newton and Suzaku data. Our emission model includes a hot thermal volume-filled bubble component cospatial with the gamma-ray region, and a shell of compressed material. We find that a bubble/shell model with n≈ 1× {10}-3 cm-3 and with log(T) ≈ 6.60-6.70 is consistent with the observed line intensities. In the framework of a continuous Galactic outflow, we infer a bubble expansion rate, age, and energy injection rate of {490}-77+230 km s-1, {4.3}-1.4+0.8 Myr, and {2.3}-0.9+5.1× {10}42 erg s-1. These estimates are consistent with the bubbles forming from a Sgr A* accretion event rather than from nuclear star formation.

  8. Quantized vortices in the ideal bose gas: a physical realization of random polynomials.

    PubMed

    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.

  9. Theoretical test of Jarzynski's equality for reversible volume-switching processes of an ideal gas system.

    PubMed

    Sung, Jaeyoung

    2007-07-01

    We present an exact theoretical test of Jarzynski's equality (JE) for reversible volume-switching processes of an ideal gas system. The exact analysis shows that the prediction of JE for the free energy difference is the same as the work done on the gas system during the reversible process that is dependent on the shape of path of the reversible volume-switching process.

  10. Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover

    SciTech Connect

    Huang Kun; Yu Zengqiang; Yin Lan

    2009-05-15

    The Ginzburg-Landau theory of a trapped Fermi gas with a BEC-BCS crossover is derived by the path-integral method. In addition to the standard Ginzburg-Landau equation, a second equation describing the total atom density is obtained. These two coupled equations are necessary to describe both homogeneous and inhomogeneous systems. The Ginzburg-Landau theory is valid near the transition temperature T{sub c} on both sides of the crossover. In the weakly interacting BEC region, it is also accurate at zero temperature where the Ginzburg-Landau equation can be mapped onto the Gross-Pitaevskii (GP) equation. The applicability of GP equation at finite temperature is discussed. On the BEC side, the fluctuation of the order parameter is studied and the renormalization to the molecule coupling constant is obtained.

  11. Protocol to engineer Fulde-Ferrell-Larkin-Ovchinnikov states in a cold Fermi gas

    NASA Astrophysics Data System (ADS)

    Dutta, Shovan; Mueller, Erich J.

    2017-08-01

    We propose a two-step experimental protocol to directly engineer Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states in a cold two-component Fermi gas loaded into a quasi-one-dimensional trap. First, one uses phase imprinting to create a train of domain walls in a superfluid with equal number of ↑- and ↓-spins. Second, one applies a radio-frequency sweep to selectively break Cooper pairs near the domain walls and transfer the ↑-spins to a third spin state, which does not interact with the ↑- and ↓-spins. The resulting FFLO state has exactly one unpaired ↓-spin in each domain wall and is stable for all values of domain-wall separation and interaction strength. We show that the protocol can be implemented with high fidelity at sufficiently strong interactions for a wide range of parameters available in present-day experimental conditions.

  12. Meissner-like effect on normal-superfluid interface of imbalanced Fermi gas

    NASA Astrophysics Data System (ADS)

    Ebrahimian, N.; Mehrafarin, M.

    2013-06-01

    We examine the N-SF interface of a polarized Fermi gas with two spin species a and b, in the presence of a weak external magnetic field. In our analysis we shall, therefore, consider the possibility of the Meissner effect too. We use perturbation theory to solve the Bogoliubov equations and obtain the wave functions. We consider the various scattering regions of the BCS regime and analytically obtain the transmission coefficients and the heat conductivity across the interface. We describe how the heat conductivity is affected by the Meissner effect and the species imbalance. It suffices to remark that the leading order term in transmission coefficients are independent of energy E. Also the additional heat conductivity is found to be proportional to λ 2 ( λ is penetration depth). The corresponding graphs is also plotted and discussed.

  13. Strong-Coupling Effects and Shear Viscosity in an Ultracold Fermi Gas

    NASA Astrophysics Data System (ADS)

    Kagamihara, D.; Ohashi, Y.

    2017-06-01

    We theoretically investigate the shear viscosity η , as well as the entropy density s, in the normal state of an ultracold Fermi gas. Including pairing fluctuations within the framework of a T-matrix approximation, we calculate these quantities in the Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein condensation (BEC) crossover region. We also evaluate η / s, to compare it with the lower bound of this ratio, conjectured by Kovtun, Son, and Starinets (KSS bound). In the weak-coupling BCS side, we show that the shear viscosity η is remarkably suppressed near the superfluid phase transition temperature Tc, due to the so-called pseudogap phenomenon. In the strong-coupling BEC side, we find that, within the neglect of the vertex corrections, one cannot correctly describe η . We also show that η / s decreases with increasing the interaction strength, to become very close to the KSS bound, \\hbar /4π kB, on the BEC side.

  14. Dynamic structure factor of the normal Fermi gas from the collisionless to the hydrodynamic regime

    SciTech Connect

    Watabe, Shohei; Nikuni, Tetsuro

    2010-09-15

    The dynamic structure factor of a normal Fermi gas is investigated by using the moment method for the Boltzmann equation. We determine the spectral function at finite temperatures over the full range of crossover from the collisionless regime to the hydrodynamic regime. We find that the Brillouin peak in the dynamic structure factor exhibits a smooth crossover from zero to first sound as functions of temperature and interaction strength. The dynamic structure factor obtained using the moment method also exhibits a definite Rayleigh peak ({omega}{approx}0), which is a characteristic of the hydrodynamic regime. We compare the dynamic structure factor obtained by the moment method with that obtained from the hydrodynamic equations.

  15. Spin-orbit-induced resonances and threshold anomalies in a reduced-dimension Fermi gas

    NASA Astrophysics Data System (ADS)

    Wang, Su-Ju; Greene, Chris H.

    2016-11-01

    We calculate the reflection and transmission probabilities in a one-dimensional Fermi gas with an equal mixing of the Rashba and Dresselhaus spin-orbit coupling (RD-SOC) produced by an external Raman laser field. These probabilities are computed over multiple relevant energy ranges within the pseudopotential approximation. Strong scattering resonances are found whenever the incident energy approaches either a scattering threshold or a quasibound state attached to one of the energetically closed higher dispersion branches. A striking difference is demonstrated between two very different regimes set by the Raman laser intensity, namely, between scattering for the single-minimum dispersion versus the double-minimum dispersion at the lowest threshold. The presence of RD-SOC together with the Raman field fundamentally changes the scattering behavior and enables the realization of very different one-dimensional theoretical models in a single experimental setup when combined with a confinement-induced resonance.

  16. Few-Body Precursor of the Higgs Mode in a Fermi Gas.

    PubMed

    Bjerlin, J; Reimann, S M; Bruun, G M

    2016-04-15

    We demonstrate that an undamped few-body precursor of the Higgs mode can be investigated in a harmonically trapped Fermi gas. Using exact diagonalization, the lowest monopole mode frequency is shown to depend nonmonotonically on the interaction strength, having a minimum in a crossover region. The minimum deepens with increasing particle number, reflecting that the mode is the few-body analogue of a many-body Higgs mode in the superfluid phase, which has a vanishing frequency at the quantum phase transition point to the normal phase. We show that this mode mainly consists of coherent excitations of time-reversed pairs, and that it can be selectively excited by modulating the interaction strength, using, for instance, a Feshbach resonance in cold atomic gases.

  17. Measuring Spin-Charge Separation in a 1D Fermi Gas

    NASA Astrophysics Data System (ADS)

    Fry, Jacob A.; Revelle, Melissa C.; Hulet, Randall G.

    2016-05-01

    We present progress on measurement of spin-charge separation in a two-component, strongly interacting, 1D gas of fermionic lithium. A characteristic feature of interacting 1D Fermi gases is that the velocity of a charge excitation propagates faster than a spin excitation. We create an excitation by applying a dipole force at the center of the cloud using a sheet of light. Depending on the detuning of this beam, we can either excite both spin species equally (charge excitation) or preferentially (spin excitation). Once this beam is turned off, the excitations propagate to the edges of the atomic cloud at a velocity determined by coupling strength. A magnetically tuned Feshbach resonance enables us to vary this coupling and map out the velocities of spin and charge excitations. Supported by an ARO MURI Grant, NSF, and The Welch Foundation

  18. Kinetic Models for Adiabatic Reversible Expansion of a Monatomic Ideal Gas.

    ERIC Educational Resources Information Center

    Chang, On-Kok

    1983-01-01

    A fixed amount of an ideal gas is confined in an adiabatic cylinder and piston device. The relation between temperature and volume in initial/final phases can be derived from the first law of thermodynamics. However, the relation can also be derived based on kinetic models. Several of these models are discussed. (JN)

  19. 40 CFR 1065.645 - Amount of water in an ideal gas.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 33 2011-07-01 2011-07-01 false Amount of water in an ideal gas. 1065.645 Section 1065.645 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.645 Amount of...

  20. How Incorrect Is the Classical Partition Function for the Ideal Gas?

    ERIC Educational Resources Information Center

    Kroemer, Herbert

    1980-01-01

    Discussed is the classical partition function for the ideal gas and how it differs from the exact value for bosons or fermions in the classical regime. The differences in the two values are negligible hence the classical treatment leads in the end to correct answers for all observables. (Author/DS)

  1. 40 CFR 1065.645 - Amount of water in an ideal gas.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Amount of water in an ideal gas. 1065.645 Section 1065.645 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS ENGINE-TESTING PROCEDURES Calculations and Data Requirements § 1065.645 Amount of...

  2. Cooking under Pressure: Applying the Ideal Gas Law in the Kitchen

    ERIC Educational Resources Information Center

    Chen, Ling; Anderson, Jennifer Y.; Wang, Diane R.

    2010-01-01

    This case study uses a daily cooking scenario to demonstrate how the boiling point of water is directly related to the external pressures in order to reinforce the concepts of boiling and boiling point, apply ideal gas law, and relate chemical reaction rates with temperatures. It also extends its teaching to autoclaves used to destroy…

  3. Kinetic Models for Adiabatic Reversible Expansion of a Monatomic Ideal Gas.

    ERIC Educational Resources Information Center

    Chang, On-Kok

    1983-01-01

    A fixed amount of an ideal gas is confined in an adiabatic cylinder and piston device. The relation between temperature and volume in initial/final phases can be derived from the first law of thermodynamics. However, the relation can also be derived based on kinetic models. Several of these models are discussed. (JN)

  4. Cooking under Pressure: Applying the Ideal Gas Law in the Kitchen

    ERIC Educational Resources Information Center

    Chen, Ling; Anderson, Jennifer Y.; Wang, Diane R.

    2010-01-01

    This case study uses a daily cooking scenario to demonstrate how the boiling point of water is directly related to the external pressures in order to reinforce the concepts of boiling and boiling point, apply ideal gas law, and relate chemical reaction rates with temperatures. It also extends its teaching to autoclaves used to destroy…

  5. How Incorrect Is the Classical Partition Function for the Ideal Gas?

    ERIC Educational Resources Information Center

    Kroemer, Herbert

    1980-01-01

    Discussed is the classical partition function for the ideal gas and how it differs from the exact value for bosons or fermions in the classical regime. The differences in the two values are negligible hence the classical treatment leads in the end to correct answers for all observables. (Author/DS)

  6. Self-consistent theory for molecular instabilities in a normal degenerate Fermi gas in the BEC-BCS crossover

    SciTech Connect

    Combescot, R.; Leyronas, X.; Kagan, M. Yu.

    2006-02-15

    We investigate within a self-consistent theory the molecular instabilities arising in the normal state of a homogeneous degenerate Fermi gas, covering the whole Bose-Einstein condensate (BEC) to BCS crossover. These are the standard instability for molecular formation, the BCS instability which corresponds to the formation of Cooper pairs, and the related Bose-Einstein instability. These instabilities manifest themselves in the properties of the particle-particle vertex, which we calculate in a ladder approximation. To find the critical temperatures corresponding to these various instabilities, we handle the properties of the interacting Fermi gas on the same footing as the instabilities by making use of the same vertex. This approximate treatment is shown to be quite satisfactory in a number of limiting situations where it agrees with known exact results. The results for the BCS critical temperature and for the BE condensation are found to be in fair agreement with earlier results. The threshold for formation of molecules at rest undergoes a sizable shift toward the BEC side, due to quantum effects arising from the presence of the degenerate Fermi gas. This should make its experimental observation fairly easy. This shift remains important at least up to temperatures comparable to the Fermi energy of the gas.

  7. Ballistic and diffusive dynamics in a two-dimensional ideal gas of macroscopic chaotic Faraday waves.

    PubMed

    Welch, Kyle J; Hastings-Hauss, Isaac; Parthasarathy, Raghuveer; Corwin, Eric I

    2014-04-01

    We have constructed a macroscopic driven system of chaotic Faraday waves whose statistical mechanics, we find, are surprisingly simple, mimicking those of a thermal gas. We use real-time tracking of a single floating probe, energy equipartition, and the Stokes-Einstein relation to define and measure a pseudotemperature and diffusion constant and then self-consistently determine a coefficient of viscous friction for a test particle in this pseudothermal gas. Because of its simplicity, this system can serve as a model for direct experimental investigation of nonequilibrium statistical mechanics, much as the ideal gas epitomizes equilibrium statistical mechanics.

  8. Pairing fluctuations and an anisotropic pseudogap phenomenon in an ultracold superfluid Fermi gas with plural p -wave superfluid phases

    NASA Astrophysics Data System (ADS)

    Inotani, Daisuke; Ohashi, Yoji

    2015-12-01

    We investigate the superfluid properties of a one-component Fermi gas with a uniaxially anisotropic p -wave pairing interaction, Ux>Uy=Uz [where Ui(i =x ,y ,z ) is a pi-wave pairing interaction]. This type of interaction is considered to be realized in a 40K Fermi gas. Including pairing fluctuations within a strong-coupling T -matrix theory, we determine the px-wave superfluid phase transition temperature Tcpx, as well as the other phase transition temperature Tcpx+i py(Fermi superfluid with a nodal superfluid order parameter. Since the p -wave Fermi superfluid is the most promising non-s -wave pairing state in an ultracold Fermi gas, our results would contribute to understanding how the anisotropic pairing fluctuations, as well as the existence of plural superfluid phases, affect many-body properties of this unconventional Fermi superfluid.

  9. Damped oscillations of a frictionless piston in an adiabatic cylinder enclosing an ideal gas

    NASA Astrophysics Data System (ADS)

    Mungan, Carl E.

    2017-05-01

    Suppose that a piston of nonzero mass encloses an ideal gas in a vertical cylinder. The piston and cylinder are thermally insulated so that no energy is lost by heat transfer to the surroundings. If the piston is set into motion, it oscillates like a block on a spring. However, the motion is damped because the gas density and pressure immediately adjacent to the piston are higher or lower than the bulk values, depending on whether the piston is compressing or expanding the gas, respectively. That automatically gives rise to a drag force linear in the velocity of the piston. It is not necessary to add extra dissipative terms such as kinetic friction between the piston and cylinder, or viscosity of the gas, to damp out the motion of the piston. The ideas should thus be helpful to undergraduate students performing a Rüchardt experiment to measure the ratio of the heat capacities of a gas.

  10. Oscillatory conductive heat transfer for a fiber in an ideal gas

    NASA Technical Reports Server (NTRS)

    Kuntz, H. L.; Perreira, N. D.

    1985-01-01

    A description of the thermal effects created by placing a cylindrical fiber in an inviscid, ideal gas, through which an acoustic wave propagates, is presented. The fibers and the gas have finite heat capacities and thermal conductivities. Expressions for the temperature distribution in the gas and in the material are determined. The temperature distribution is caused by pressure oscillations in the gas which, in turn, are caused by the passage of an acoustic wave. The relative value of a dimensionless parameter is found to be indicative of whether the exact or approximate equations should be used in the solution. This parameter is a function of the thermal conductivities and heat capacities of the fiber and gas, the acoustic frequency, and the fiber diameter.

  11. Novel Superfluidity in a Trapped Gas of Fermi Atoms with Repulsive Interaction Loaded on an Optical Lattice

    NASA Astrophysics Data System (ADS)

    Machida, M.; Yamada, S.; Ohashi, Y.; Matsumoto, H.

    2004-11-01

    We investigate a possibility of superfluidity in a trapped gas of Fermi atoms with a repulsive interaction in the presence of an optical lattice. Applying the exact diagonalization method to a one-dimensional Hubbard model including the trap potential, we find that, when the strength of the repulsive interaction exceeds a critical value, the binding energy of two Fermi atoms becomes negative below the half-filling case, indicating that an attractive interaction effectively works between Fermi atoms. In this case, a “Mott insulating core” appears in the center of the trap, where each site is occupied by one atom. The Cooper-pair correlation strongly develops between atoms in the left- and right-hand sides of this core.

  12. Contact Tensor in a p-Wave Fermi Gas with Anisotropic Feshbach Resonances

    NASA Astrophysics Data System (ADS)

    Yoshida, Shuhei M.; Ueda, Masahito

    2016-05-01

    Recent theoretical and experimental investigations have revealed that a Fermi gas with a p-wave Feshbach resonance has universal relations between the system's high-momentum behavior and thermodynamics. A new feature introduced by the p-wave interaction is anisotropy in the Feshbach resonances; three degenerate p-wave resonances split according to the magnetic quantum number of the closed-channel molecules | m | due to the magnetic dipole-dipole interaction. Here, we investigate the consequences of the anisotropy. We show that the momentum distribution has a high-momentum asymptote nk ~k-2 ∑ m, m' = - 1 1 >Cm, m'Y1m * (\\kcirc)Y1m' (\\kcirc) , in which we introduce the p-wave contact tensor Cm ,m'. In contrast to the previous studies, it has nine components. We identify them as the number, angular momentum, and nematicity of the closed-channel molecules. We also discuss two examples, the anisotropic p-wave superfluid and a gas confined in a cigar-shaped trap, which exhibit a nematicity component in the p-wave contact tensor.

  13. Probing the 1D-3D Crossover of a Spin-Imbalanced Fermi Gas

    NASA Astrophysics Data System (ADS)

    Revelle, Melissa; Olsen, Ben A.; Liao, Yean-An; Hulet, Randall G.

    2012-06-01

    We have previously mapped the phase diagram of a 1D spin-imbalanced Fermi gas by confining the atoms in an array of tubes using a 2D optical lattice.ootnotetextY.A. Liao et al., Nature 467, 567 (2010). Within each tube we observed separation of the atoms into a partially polarized superfluid core and fully paired or fully polarized wings (depending on the spin polarization). In 3D, the phase separation is inverted, such that the cloud center is fully paired.ootnotetextG. B. Partridge et al., Science 311, 503 (2006); Y. Shin et al., Phys. Rev. Lett. 97, 030401 (2006). We investigate the transition from a 1D to 3D gas by smoothly varying the lattice depth which changes the tunneling between the tubes. This allows us to study how the spin density changes as a function of inter-tube coupling. By varying the lattice depth quickly, we can measure the spin transport properties in a strongly interacting system. Progress will be reported.

  14. Using Rubber-Elastic Material-Ideal Gas Analogies To Teach Introductory Thermodynamics. Part I: Equations of State.

    ERIC Educational Resources Information Center

    Smith, Brent

    2002-01-01

    Describes equations of state as a supplement to an introductory thermodynamics undergraduate course. Uses rubber-elastic materials (REM) which have strong analogies to the concept of an ideal gas and explains the molar basis of REM. Provides examples of the analogies between ideal gas and REM and mathematical analogies. (Contains 22 references.)…

  15. Using Rubber-Elastic Material-Ideal Gas Analogies To Teach Introductory Thermodynamics. Part II: The Laws of Thermodynamics.

    ERIC Educational Resources Information Center

    Smith, Brent

    2002-01-01

    Describes the laws of thermodynamics as a supplement to an introductory thermodynamics undergraduate course. Uses rubber-elastic materials (REM) which have strong analogies to the concept of ideal gas. Provides examples of the analogies between ideal gas and REM and mathematical analogies. (YDS)

  16. Using Rubber-Elastic Material-Ideal Gas Analogies To Teach Introductory Thermodynamics. Part II: The Laws of Thermodynamics.

    ERIC Educational Resources Information Center

    Smith, Brent

    2002-01-01

    Describes the laws of thermodynamics as a supplement to an introductory thermodynamics undergraduate course. Uses rubber-elastic materials (REM) which have strong analogies to the concept of ideal gas. Provides examples of the analogies between ideal gas and REM and mathematical analogies. (YDS)

  17. Using Rubber-Elastic Material-Ideal Gas Analogies To Teach Introductory Thermodynamics. Part I: Equations of State.

    ERIC Educational Resources Information Center

    Smith, Brent

    2002-01-01

    Describes equations of state as a supplement to an introductory thermodynamics undergraduate course. Uses rubber-elastic materials (REM) which have strong analogies to the concept of an ideal gas and explains the molar basis of REM. Provides examples of the analogies between ideal gas and REM and mathematical analogies. (Contains 22 references.)…

  18. Homogeneous Atomic Fermi Gases

    NASA Astrophysics Data System (ADS)

    Mukherjee, Biswaroop; Yan, Zhenjie; Patel, Parth B.; Hadzibabic, Zoran; Yefsah, Tarik; Struck, Julian; Zwierlein, Martin W.

    2017-03-01

    We report on the creation of homogeneous Fermi gases of ultracold atoms in a uniform potential. In the momentum distribution of a spin-polarized gas, we observe the emergence of the Fermi surface and the saturated occupation of one particle per momentum state: the striking consequence of Pauli blocking in momentum space for a degenerate gas. Cooling a spin-balanced Fermi gas at unitarity, we create homogeneous superfluids and observe spatially uniform pair condensates. For thermodynamic measurements, we introduce a hybrid potential that is harmonic in one dimension and uniform in the other two. The spatially resolved compressibility reveals the superfluid transition in a spin-balanced Fermi gas, saturation in a fully polarized Fermi gas, and strong attraction in the polaronic regime of a partially polarized Fermi gas.

  19. Enthalpy, Entropy, and Exergy Flows — Real Gas Effects in Ideal Pulse Tube Cryocoolers

    NASA Astrophysics Data System (ADS)

    Kittel, P.

    2006-04-01

    The enthalpy, entropy, and exergy flows in ideal pulse tube cryocoolers and some of the losses in non-ideal pulse tube cryocoolers have been described previously. This paper will describe how these flows are affected by real gas phenomena in ideal pulse tube cryocoolers. Frequently such descriptions take an energy-centric view, concentrating on the first law of thermodynamics, the conservation of energy. This approach can result in a complex description of the cooler in terms of energy and enthalpy flows. An alternative is to take an entropy-centric approach. Closely related to this is the exergy-centric approach. These descriptions concentrate on the second law of thermodynamics, the generation of entropy or the destruction of exergy. Both the energy-centric and exergy/entropy-centric approaches make use of both the laws of thermodynamics and both approaches give equivalent descriptions of a cryocooler. However, the latter approach can be more useful as it can yield a simpler description, one that emphasis loss mechanisms. This paper applies the second law approach to pulse tube cryocoolers. The non-ideal gas effects in the various components on the exergy, entropy, and enthalpy flows are discussed. The discussion applies to basic, orifice, and inertance type pulse tubes and can be easily extended to other types of regenerative cryocoolers such as Gifford-McMahon and Stirling cryocoolers.

  20. 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.

  1. Advantages and challenges in coupling an ideal gas to atomistic models in adaptive resolution simulations

    NASA Astrophysics Data System (ADS)

    Kreis, K.; Fogarty, A. C.; Kremer, K.; Potestio, R.

    2015-09-01

    In adaptive resolution simulations, molecular fluids are modeled employing different levels of resolution in different subregions of the system. When traveling from one region to the other, particles change their resolution on the fly. One of the main advantages of such approaches is the computational efficiency gained in the coarse-grained region. In this respect the best coarse-grained system to employ in the low resolution region would be the ideal gas, making intermolecular force calculations in the coarse-grained subdomain redundant. In this case, however, a smooth coupling is challenging due to the high energetic imbalance between typical liquids and a system of non-interacting particles. In the present work, we investigate this approach, using as a test case the most biologically relevant fluid, water. We demonstrate that a successful coupling of water to the ideal gas can be achieved with current adaptive resolution methods, and discuss the issues that remain to be addressed.

  2. Critical behavior of the ideal-gas Bose-Einstein condensation in the Apollonian network.

    PubMed

    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.

  3. Use, misuse and extensions of "ideal gas" models of animal encounter.

    PubMed

    Hutchinson, John M C; Waser, Peter M

    2007-08-01

    Biologists have repeatedly rediscovered classical models from physics predicting collision rates in an ideal gas. These models, and their two-dimensional analogues, have been used to predict rates and durations of encounters among animals or social groups that move randomly and independently, given population density, velocity, and distance at which an encounter occurs. They have helped to separate cases of mixed-species association based on behavioural attraction from those that simply reflect high population densities, and to detect cases of attraction or avoidance among conspecifics. They have been used to estimate the impact of population density, speeds of movement and size on rates of encounter between members of the opposite sex, between gametes, between predators and prey, and between observers and the individuals that they are counting. One limitation of published models has been that they predict rates of encounter, but give no means of determining whether observations differ significantly from predictions. Another uncertainty is the robustness of the predictions when animal movements deviate from the model's assumptions in specific, biologically relevant ways. Here, we review applications of the ideal gas model, derive extensions of the model to cover some more realistic movement patterns, correct several errors that have arisen in the literature, and show how to generate confidence limits for expected rates of encounter among independently moving individuals. We illustrate these results using data from mangabey monkeys originally used along with the ideal gas model to argue that groups avoid each other. Although agent-based simulations provide a more flexible alternative approach, the ideal gas model remains both a valuable null model and a useful, less onerous, approximation to biological reality.

  4. Modeling shock waves in an ideal gas: combining the Burnett approximation and Holian's conjecture.

    PubMed

    He, Yi-Guang; Tang, Xiu-Zhang; Pu, Yi-Kang

    2008-07-01

    We model a shock wave in an ideal gas by combining the Burnett approximation and Holian's conjecture. We use the temperature in the direction of shock propagation rather than the average temperature in the Burnett transport coefficients. The shock wave profiles and shock thickness are compared with other theories. The results are found to agree better with the nonequilibrium molecular dynamics (NEMD) and direct simulation Monte Carlo (DSMC) data than the Burnett equations and the modified Navier-Stokes theory.

  5. Fluctuation theorem for entropy production during effusion of an ideal gas with momentum transfer.

    PubMed

    Wood, Kevin; Van den Broeck, C; Kawai, R; Lindenberg, Katja

    2007-06-01

    We derive an exact expression for entropy production during effusion of an ideal gas driven by momentum transfer in addition to energy and particle flux. Following the treatment in Cleuren [Phys. Rev. E 74, 021117 (2006)], we construct a master equation formulation of the process and explicitly verify the thermodynamic fluctuation theorem, thereby directly exhibiting its extended applicability to particle flows and hence to hydrodynamic systems.

  6. Thermodynamics of a one-dimensional ideal gas with fractional exclusion statistics

    SciTech Connect

    Murthy, M.V.N.; Shankar, R. )

    1994-12-19

    We show that the particles in the Calogero-Sutherland model obey fractional exclusion statistics as defined by Haldane. We construct anyon number densities and derive the energy distribution function. We show that the partition function factorizes in the form characteristic of an ideal gas. The virial expansion is exactly computable and interestingly it is only the second virial coefficient that encodes the statistics information.

  7. Zero-Temperature Properties of a Strongly Interacting Superfluid Fermi Gas in the BCS-BEC Crossover Region

    NASA Astrophysics Data System (ADS)

    Tajima, H.; van Wyk, P.; Hanai, R.; Kagamihara, D.; Inotani, D.; Horikoshi, M.; Ohashi, Y.

    2016-11-01

    We investigate thermodynamic properties and effects of quantum fluctuations in the Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein condensation (BEC) crossover region of a superfluid Fermi gas in the low-temperature limit. Including strong-coupling corrections within the framework of an extended T-matrix approximation, we numerically compute the isothermal compressibility χ _n . While quantum fluctuation effects on χ _n in the strong-coupling BEC regime are explained by the quantum depletion due to a repulsive interaction between tightly bound molecules, effects of self-energy shift on the Fermi chemical potential are found to enhance χ _n in the weak-coupling BCS region. We also show that the calculated χ _n agrees well with the recent experiment on a ^6 Li Fermi gas done from the weak-coupling region to the unitarity limit. Our result would be useful for the study of many-body quantum corrections in the BCS-BEC crossover region of a strongly interacting Fermi superfluid.

  8. Zero-Temperature Properties of a Strongly Interacting Superfluid Fermi Gas in the BCS-BEC Crossover Region

    NASA Astrophysics Data System (ADS)

    Tajima, H.; van Wyk, P.; Hanai, R.; Kagamihara, D.; Inotani, D.; Horikoshi, M.; Ohashi, Y.

    2017-06-01

    We investigate thermodynamic properties and effects of quantum fluctuations in the Bardeen-Cooper-Schrieffer (BCS)-Bose-Einstein condensation (BEC) crossover region of a superfluid Fermi gas in the low-temperature limit. Including strong-coupling corrections within the framework of an extended T-matrix approximation, we numerically compute the isothermal compressibility χ _n. While quantum fluctuation effects on χ _n in the strong-coupling BEC regime are explained by the quantum depletion due to a repulsive interaction between tightly bound molecules, effects of self-energy shift on the Fermi chemical potential are found to enhance χ _n in the weak-coupling BCS region. We also show that the calculated χ _n agrees well with the recent experiment on a ^6Li Fermi gas done from the weak-coupling region to the unitarity limit. Our result would be useful for the study of many-body quantum corrections in the BCS-BEC crossover region of a strongly interacting Fermi superfluid.

  9. 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.

  10. Clock shifts in a Fermi gas interacting with a minority component: A soluble model

    SciTech Connect

    Bruun, G. M.; Pethick, C. J.; Yu Zhenhua

    2010-03-15

    We consider the absorption spectrum of a Fermi gas mixed with a minority species when majority fermions are transferred to another internal state by an external probe. In the limit when the minority species is much more massive than the majority one, we show that the minority species may be treated as static impurities and the problem can be solved in closed form. The analytical results bring out the importance of vertex corrections, which change qualitatively the nature of the absorption spectrum. It is demonstrated that large line shifts are not associated with resonant interactions in general. We also show that the commonly used ladder approximation fails when the majority component is degenerate for large mass ratios between the minority and majority species and that bubble diagrams, which correspond to the creation of many particle-hole pairs, must be taken into account. We carry out detailed numerical calculations, which confirm the analytical insights, and we point out the connection to shadowing phenomena in nuclear physics.

  11. Chiral superfluidity with p-wave symmetry from an interacting s-wave atomic Fermi gas.

    PubMed

    Liu, Bo; Li, Xiaopeng; Wu, Biao; Liu, W Vincent

    2014-09-30

    Chiral p-wave superfluids are fascinating topological quantum states of matter that have been found in the liquid (3)He-A phase and arguably in the electronic Sr2RuO4 superconductor. They are fundamentally related to the fractional 5/2 quantum Hall state, which supports fractional exotic excitations. Past studies show that they require spin-triplet pairing of fermions by p-wave interaction. Here we report that a p-wave chiral superfluid state can arise from spin-singlet pairing for an s-wave interacting atomic Fermi gas in an optical lattice. This p-wave state is conceptually distinct from all previous conventional p-wave states as it is for the centre-of-mass motion, instead of the relative motion. It leads to spontaneous generation of angular momentum, finite Chern numbers and topologically protected chiral fermionic zero modes bounded to domain walls, all occuring at a higher critical temperature in relative scales. Signature quantities are predicted for the cold atom experimental condition.

  12. Repulsive Fermi gas in a harmonic trap: Ferromagnetism and spin textures

    NASA Astrophysics Data System (ADS)

    Leblanc, L. J.; Thywissen, J. H.; Burkov, A. A.; Paramekanti, A.

    2009-07-01

    We study ferromagnetism in a repulsively interacting two-component Fermi gas in a harmonic trap. Within a local density approximation, the two components phase separate beyond a critical interaction strength, with one species having a higher density at the trap center. We discuss several easily observable experimental signatures of this transition. The mean-field release energy, its separate kinetic and interaction contributions, as well as the potential energy all depend on the interaction strength and contain a sharp signature of this transition. In addition, the conversion rate of atoms to molecules, arising from three-body collisions, peaks at an interaction strength just beyond the ferromagnetic transition point. We then go beyond the local density approximation and derive an energy functional that includes a term that depends on the local magnetization gradient and acts as a “surface tension.” Using this energy functional, we numerically study the energetics of some candidate spin textures that may be stabilized in a harmonic trapping potential at zero net magnetization. We find that a hedgehog state has a lower energy than an “in-out” domain-wall state in an isotropic trap. Upon inclusion of trap anisotropy we find that the hedgehog magnetization profile gets distorted due to the surface tension term, this distortion being more apparent for small atom numbers. We estimate that the magnetic dipole interaction does not play a significant role in this system. We consider possible implications for experiments on trapped L6i and K40 gases.

  13. Numerical analysis of spin-orbit-coupled one-dimensional Fermi gas in a magnetic field

    NASA Astrophysics Data System (ADS)

    Chan, Y. H.

    2015-06-01

    Based on the density-matrix renormalization group and the infinite time-evolving block decimation methods we study the interacting spin-orbit-coupled 1D Fermi gas in a transverse magnetic field. We find that the system with an attractive interaction can have a polarized insulator phase, a superconducting (SC) phase, a Luther-Emery (LE) phase, and a band insulator phase as we vary the chemical potential and the strength of the magnetic field. Spin-orbit coupling (SOC) enhances the triplet pairing order at zero momentum in both the SC and the LE phase, which leads to an algebraically decaying correlation with the same exponent as that of the singlet pairing one. In contrast to the Fulde-Ferrell-Larkin-Ovchinnikov phase found in the spin imbalanced system without SOC, pairings at finite momentum in these two phases have larger exponents hence do not dictate the long-range behavior. We also test for the presence of Majorana fermions in this system. Unlike results from the mean-field study, we do not find positive evidence of Majorana fermions.

  14. Repulsive Fermi gas in a harmonic trap: Ferromagnetism and spin textures

    SciTech Connect

    LeBlanc, L. J.; Thywissen, J. H.; Paramekanti, A.; Burkov, A. A.

    2009-07-15

    We study ferromagnetism in a repulsively interacting two-component Fermi gas in a harmonic trap. Within a local density approximation, the two components phase separate beyond a critical interaction strength, with one species having a higher density at the trap center. We discuss several easily observable experimental signatures of this transition. The mean-field release energy, its separate kinetic and interaction contributions, as well as the potential energy all depend on the interaction strength and contain a sharp signature of this transition. In addition, the conversion rate of atoms to molecules, arising from three-body collisions, peaks at an interaction strength just beyond the ferromagnetic transition point. We then go beyond the local density approximation and derive an energy functional that includes a term that depends on the local magnetization gradient and acts as a 'surface tension'. Using this energy functional, we numerically study the energetics of some candidate spin textures that may be stabilized in a harmonic trapping potential at zero net magnetization. We find that a hedgehog state has a lower energy than an 'in-out' domain-wall state in an isotropic trap. Upon inclusion of trap anisotropy we find that the hedgehog magnetization profile gets distorted due to the surface tension term, this distortion being more apparent for small atom numbers. We estimate that the magnetic dipole interaction does not play a significant role in this system. We consider possible implications for experiments on trapped {sup 6}Li and {sup 40}K gases.

  15. Observing the 1D-3D Crossover in a Spin-Imbalanced Fermi Gas

    NASA Astrophysics Data System (ADS)

    Revelle, Melissa C.; Fry, Jacob A.; Olsen, Ben A.; Hulet, Randall G.

    2016-05-01

    Trapped two-component Fermi gases phase separate into superfluid and normal phases when their spin populations are imbalanced. In 3D, a balanced superfluid core is surrounded by shells of partially polarized and normal phases, while in 1D, the balanced superfluid occupies the low density wings. We explored the crossover from 3D to 1D using a two-spin component ultracold atomic gas of 6 Li prepared in the lowest two hyperfine sublevels, where the interactions are tuned by a Feshbach resonance. The atoms are confined to 1D tubes where the tunneling rate t between tubes is varied by changing the depth of a 2D optical lattice. We observe the transition from 1D to 3D-like phase separation by varying t and interaction strength which changes the pair binding energy ɛB. We find a universal scaling of the dimensional crossover with t /ɛB , in agreement with previous theory. The crossover region is believed to be the most promising to find the exotic FFLO superfluid phase. Supported by the NSF and the Welch Foundation.

  16. Reproducing neutrino effects on the matter power spectrum through a degenerate Fermi gas approach

    SciTech Connect

    Perico, E.L.D.; Bernardini, A.E. E-mail: alexeb@ufscar.br

    2011-06-01

    Modifications on the predictions about the matter power spectrum based on the hypothesis of a tiny contribution from a degenerate Fermi gas (DFG) test-fluid to some dominant cosmological scenario are investigated. Reporting about the systematic way of accounting for all the cosmological perturbations, through the Boltzmann equation we obtain the analytical results for density fluctuation, δ, and fluid velocity divergence, θ, of the DFG. Small contributions to the matter power spectrum are analytically obtained for the radiation-dominated background, through an ultra-relativistic approximation, and for the matter-dominated and Λ-dominated eras, through a non-relativistic approximation. The results can be numerically reproduced and compared with those of considering non-relativistic and ultra-relativistic neutrinos into the computation of the matter power spectrum. Lessons concerning the formation of large scale structures of a DFG are depicted, and consequent deviations from standard ΛCDM predictions for the matter power spectrum (with and without neutrinos) are quantified.

  17. Equation of state of an ideal gas with nonergodic behavior in two connected vessels.

    PubMed

    Naplekov, D M; Semynozhenko, V P; Yanovsky, V V

    2014-01-01

    We consider a two-dimensional collisionless ideal gas in the two vessels connected through a small hole. One of them is a well-behaved chaotic billiard, another one is known to be nonergodic. A significant part of the second vessel's phase space is occupied by an island of stability. In the works of Zaslavsky and coauthors, distribution of Poincaré recurrence times in similar systems was considered. We study the gas pressure in the vessels; it is uniform in the first vessel and not uniform in second one. An equation of the gas state in the first vessel is obtained. Despite the very different phase-space structure, behavior of the second vessel is found to be very close to the behavior of a good ergodic billiard but of different volume. The equation of state differs from the ordinary equation of ideal gas state by an amendment to the vessel's volume. Correlation of this amendment with a share of the phase space under remaining intact islands of stability is shown.

  18. The success of Fermi gas model for overall scaling of 2D metal-to-insulator transition data

    NASA Astrophysics Data System (ADS)

    Cheremisin, M. V.

    2017-03-01

    The melting condition for two-dimensional Wigner solid (Platzman and Fukuyama, 1974) [14] is shown to contain an error of a factor of π. The analysis of experimental data for apparent 2D metal-to-insulator transition shows that the Wigner solidification (Tanatar and Ceperley, 1989) [16] has been never achieved. Within routine Fermi gas model both the metallic and insulating behavior of different 2D system for actual range of carrier densities and temperatures is explained.

  19. Determination of the Density and Temperature Dependence of the Shear Viscosity of a Unitary Fermi Gas Based on Hydrodynamic Flow

    NASA Astrophysics Data System (ADS)

    Bluhm, Marcus; Hou, Jiaxun; Schäfer, Thomas

    2017-08-01

    We determine the shear viscosity of the ultracold Fermi gas at unitarity in the normal phase using hydrodynamic expansion data. The analysis is based on a generalized fluid dynamic framework which ensures a smooth transition between the fluid dynamic core of the cloud and the ballistic corona. We use expansion data taken by Joseph, Elliott, and Thomas [Shear Viscosity of a Universal Fermi Gas Near the Superfluid Phase Transition, Phys. Rev. Lett. 115, 020401 (2015)., 10.1103/PhysRevLett.115.020401] and measurements of the equation of state by Ku et al. [Revealing the superfluid lambda transition in the universal thermodynamics of a unitary Fermi gas, Science 335, 563 (2012)., 10.1126/science.1214987]. We find that the shear viscosity to particle density ratio just above the critical temperature is η /n |Tc=0.41 ±0.11 . We also obtain evidence that the shear viscosity to entropy density ratio has a minimum slightly above Tc with η /s| min=0.50 ±0.10 .

  20. A combustion model for studying the effects of ideal gas properties on jet noise

    NASA Astrophysics Data System (ADS)

    Jacobs, Jerin; Tinney, Charles

    2016-11-01

    A theoretical combustion model is developed to simulate the influence of ideal gas effects on various aeroacoustic parameters over a range of equivalence ratios. The motivation is to narrow the gap between laboratory and full-scale jet noise testing. The combustion model is used to model propane combustion in air and kerosene combustion in air. Gas properties from the combustion model are compared to real lab data acquired at the National Center for Physical Acoustics at the University of Mississippi as well as outputs from NASA's Chemical Equilibrium Analysis code. Different jet properties are then studied over a range of equivalence ratios and pressure ratios for propane combustion in air, kerosene combustion in air and heated air. The findings reveal negligible differences between the three constituents where the density and sound speed ratios are concerned. Albeit, the area ratio required for perfectly expanded flow is shown to be more sensitive to gas properties, relative to changes in the temperature ratio.

  1. Binary Collision Density in a Non-Ideal Gas as a Function of Particle Density, Collision Diameter, and Temperature

    NASA Astrophysics Data System (ADS)

    Mohazzabi, Pirooz

    2017-09-01

    Using molecular dynamics simulations, binary collision density in a dense non-ideal gas with Lennard-Jones interactions is investigated. It is shown that the functional form of the dependence of collision density on particle density and collision diameter remains the same as that for an ideal gas. The temperature dependence of the collision density, however, has a very different form at low temperatures, where it decreases as temperature increases. But at higher temperatures the functional form becomes the same as that for an ideal gas.

  2. Asymptotic correlation functions and FFLO signature for the one-dimensional attractive spin-1/2 Fermi gas

    PubMed Central

    Lee, J.Y.; Guan, X.W.

    2011-01-01

    We investigate the long distance asymptotics of various correlation functions for the one-dimensional spin-1/2 Fermi gas with attractive interactions using the dressed charge formalism. In the spin polarized phase, these correlation functions exhibit spatial oscillations with a power-law decay whereby their critical exponents are found through conformal field theory. We show that spatial oscillations of the leading terms in the pair correlation function and the spin correlation function solely depend on ΔkF and 2ΔkF, respectively. Here ΔkF=π(n↑−n↓) denotes the mismatch between the Fermi surfaces of spin-up and spin-down fermions. Such spatial modulations are characteristics of a Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state. Our key observation is that backscattering among the Fermi points of bound pairs and unpaired fermions results in a one-dimensional analog of the FFLO state and displays a microscopic origin of the FFLO nature. Furthermore, we show that the pair correlation function in momentum space has a peak at the point of mismatch between both Fermi surfaces k=ΔkF, which has recently been observed in numerous numerical studies. PMID:26594088

  3. Speed of sound and ideal-gas heat capacity of freon R-236ea

    NASA Astrophysics Data System (ADS)

    Komarov, S. G.; Gruzdev, V. A.; Stankus, S. V.

    2008-09-01

    Speed of sound in the gaseous freon R-236ea with the purity of 99.68 mol. % has been measured by the method of ultrasonic interferometer in the range from 263 to 423 K and at pressures from 17 kPA to 4.2 MPa. Errors of temperature, pressure, and speed of sound measurement were estimated to be within +/- 20 mK, ± 1.5 kPa, and ±(0.1+0.2) % respectively. Temperature dependence of ideal-gas heat capacity of R-236ea has been calculated on the basis of the obtained data.

  4. Probability theory for 3-layer remote sensing in ideal gas law environment.

    PubMed

    Ben-David, Avishai; Davidson, Charles E

    2013-08-26

    We extend the probability model for 3-layer radiative transfer [Opt. Express 20, 10004 (2012)] to ideal gas conditions where a correlation exists between transmission and temperature of each of the 3 layers. The effect on the probability density function for the at-sensor radiances is surprisingly small, and thus the added complexity of addressing the correlation can be avoided. The small overall effect is due to (a) small perturbations by the correlation on variance population parameters and (b) cancellation of perturbation terms that appear with opposite signs in the model moment expressions.

  5. On the accuracy of Whitham's method. [for steady ideal gas flow past cones

    NASA Technical Reports Server (NTRS)

    Zahalak, G. I.; Myers, M. K.

    1974-01-01

    The steady flow of an ideal gas past a conical body is studied by the method of matched asymptotic expansions and by Whitham's method in order to assess the accuracy of the latter. It is found that while Whitham's method does not yield a correct asymptotic representation of the perturbation field to second order in regions where the flow ahead of the Mach cone of the apex is disturbed, it does correctly predict the changes of the second-order perturbation quantities across a shock (the first-order shock strength). The results of the analysis are illustrated by a special case of a flat, rectangular plate at incidence.

  6. A complete theory for the magnetism of an ideal gas of electrons

    SciTech Connect

    Biswas, Shyamal; Jana, Debnarayan; Sen, Swati

    2013-05-15

    We have explored Pauli paramagnetism, Landau diamagnetism, and de Haas-van Alphen effect in a single framework, and unified these three effects for all temperatures as well as for all strengths of magnetic field. Our result goes beyond Pauli-Landau result on the magnetism of the 3-D ideal gas of electrons, and is able to describe crossover of the de Haas-van Alphen oscillation to the saturation of magnetization. We also have obtained a novel asymptotic series expansion for the low temperature properties of the system.

  7. Ideal-gas-like market models with savings: Quenched and annealed cases

    NASA Astrophysics Data System (ADS)

    Chatterjee, Arnab; Chakrabarti, Bikas K.

    2007-08-01

    We analyze the ideal-gas-like models of markets and review the different cases where a ‘savings’ factor changes the nature and shape of the distribution of wealth. These models can produce similar distribution of wealth as observed across varied economies. We present a more realistic model where the saving factor can vary over time (annealed savings) and yet produce Pareto distribution of wealth in certain cases. We discuss the relevance of such models in the context of wealth distribution, and address some recent issues in the context of these models.

  8. Greenberger-Horne-Zeilinger and W entanglement witnesses for the noninteracting Fermi gas

    SciTech Connect

    Habibian, Hessam; Clark, John W.; Behbood, Naeimeh; Hingerl, Kurt

    2010-03-15

    The existence and nature of tripartite entanglement of a noninteracting Fermi gas (NIFG) is investigated. Three classes of parametrized entanglement witnesses (EWs) are introduced with the aim of detecting genuine tripartite entanglement in the three-body reduced density matrix and discriminating between the presence of the two types of genuine tripartite entanglement, W/B and GHZ/W (the convex set of B states is comprised of mixed states of product and biseparable states; that of W states is comprised of mixed states of B states and W-type pure entangled states; and the GHZ (Greenberger-Horne-Zeilinger) set contains generic mixtures of any kind for a tripartite system). By choosing appropriate EW operators, the problem of finding GHZ and W EWs is reduced to linear programming. Specifically, we devise W EWs based on a spin-chain model with periodic boundary conditions, and we construct a class of parametrized GHZ EWs by linearly combining projection operators corresponding to all the different state-vector types arising for a three-fermion system. A third class of EWs is provided by a GHZ stabilizer operator capable of distinguishing W/B from GHZ/B entanglement, which is not possible with W EWs. Implementing these classes of EWs, it is found that all states containing genuine tripartite entanglement are of W type, and hence states containing GHZ/W genuine tripartite entanglement do not arise. Some genuine tripartite entangled states that have a positive partial transpose (PPT) with respect to some bipartition are detected. Finally, it is demonstrated that a NIFG does not exhibit 'pure'W/B genuine tripartite entanglement: three-party entanglement without any separable or biseparable admixture does not occur.

  9. Testing the nonlocal kinetic energy functional of an inhomogeneous, two-dimensional degenerate Fermi gas within the average density approximation

    NASA Astrophysics Data System (ADS)

    Towers, J.; van Zyl, B. P.; Kirkby, W.

    2015-08-01

    In a recent paper [B. P. van Zyl et al., Phys. Rev. A 89, 022503 (2014), 10.1103/PhysRevA.89.022503], the average density approximation (ADA) was implemented to develop a parameter-free, nonlocal kinetic energy functional to be used in the orbital-free density functional theory of an inhomogeneous, two-dimensional (2D) Fermi gas. In this work, we provide a detailed comparison of self-consistent calculations within the ADA with the exact results of the Kohn-Sham density functional theory and the elementary Thomas-Fermi (TF) approximation. We demonstrate that the ADA for the 2D kinetic energy functional works very well under a wide variety of confinement potentials, even for relatively small particle numbers. Remarkably, the TF approximation for the kinetic energy functional, without any gradient corrections, also yields good agreement with the exact kinetic energy for all confining potentials considered, although at the expense of the spatial and kinetic energy densities exhibiting poor pointwise agreement, particularly near the TF radius. Our findings illustrate that the ADA kinetic energy functional yields accurate results for both the local and global equilibrium properties of an inhomogeneous 2D Fermi gas, without the need for any fitting parameters.

  10. 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

  11. Gas-Kinetic Theory Based Flux Splitting Method for Ideal Magnetohydrodynamics

    NASA Technical Reports Server (NTRS)

    Xu, Kun

    1998-01-01

    A gas-kinetic solver is developed for the ideal magnetohydrodynamics (MHD) equations. The new scheme is based on the direct splitting of the flux function of the MHD equations with the inclusion of "particle" collisions in the transport process. Consequently, the artificial dissipation in the new scheme is much reduced in comparison with the MHD Flux Vector Splitting Scheme. At the same time, the new scheme is compared with the well-developed Roe-type MHD solver. It is concluded that the kinetic MHD scheme is more robust and efficient than the Roe- type method, and the accuracy is competitive. In this paper the general principle of splitting the macroscopic flux function based on the gas-kinetic theory is presented. The flux construction strategy may shed some light on the possible modification of AUSM- and CUSP-type schemes for the compressible Euler equations, as well as to the development of new schemes for a non-strictly hyperbolic system.

  12. Supersonic beams at high particle densities: model description beyond the ideal gas approximation.

    PubMed

    Christen, Wolfgang; Rademann, Klaus; Even, Uzi

    2010-10-28

    Supersonic molecular beams constitute a very powerful technique in modern chemical physics. They offer several unique features such as a directed, collision-free flow of particles, very high luminosity, and an unsurpassed strong adiabatic cooling during the jet expansion. While it is generally recognized that their maximum flow velocity depends on the molecular weight and the temperature of the working fluid in the stagnation reservoir, not a lot is known on the effects of elevated particle densities. Frequently, the characteristics of supersonic beams are treated in diverse approximations of an ideal gas expansion. In these simplified model descriptions, the real gas character of fluid systems is ignored, although particle associations are responsible for fundamental processes such as the formation of clusters, both in the reservoir at increased densities and during the jet expansion. In this contribution, the various assumptions of ideal gas treatments of supersonic beams and their shortcomings are reviewed. It is shown in detail that a straightforward thermodynamic approach considering the initial and final enthalpy is capable of characterizing the terminal mean beam velocity, even at the liquid-vapor phase boundary and the critical point. Fluid properties are obtained using the most accurate equations of state available at present. This procedure provides the opportunity to naturally include the dramatic effects of nonideal gas behavior for a large variety of fluid systems. Besides the prediction of the terminal flow velocity, thermodynamic models of isentropic jet expansions permit an estimate of the upper limit of the beam temperature and the amount of condensation in the beam. These descriptions can even be extended to include spinodal decomposition processes, thus providing a generally applicable tool for investigating the two-phase region of high supersaturations not easily accessible otherwise.

  13. The Ideal and Real Gas Heat Capacity of Potassium Atoms at High Temperatures

    NASA Astrophysics Data System (ADS)

    Biolsi, Louis; Biolsi, Michael

    2016-04-01

    The ideal gas heat capacity, Cp, of potassium atoms is calculated to high temperatures using statistical mechanics. Since there are a large number of electronic energy levels in the partition function (Boltzmann sum) below the first ionization potential, the partition function and Cp will become very large as the temperature increases unless the number of energy levels contributing to the partition function is constrained. Two primary categories of arguments are used to do this. First, at high temperatures, the increased size of the atoms constrains the sum (Bethe method). Second, an argument based on the existence of interacting charged species at higher temperatures is used to constrain the sum (ionization potential lowering method). When potassium atoms are assumed to constitute a real gas that obeys the virial equation of state, the lowest non-ideal contribution to Cp depends on the second derivative of the second virial coefficient, B( T), which depends on the interaction potential energy curves between two potassium atoms. When two ground-state (2{S}) atoms interact, they can follow either of the two potential energy curves. When a 2{S} atom interacts with an atom in the first electronically excited (2{P}) state, they can follow any of the eight potential energy curves. The values of B( T) for the ten states are determined, then averaged, and used to calculate the nonideal contribution to Cp.

  14. Recommended Ideal-Gas Thermochemical Functions for Heavy Water and its Substituent Isotopologues

    NASA Astrophysics Data System (ADS)

    Simkó, Irén; Furtenbacher, Tibor; Hrubý, Jan; Zobov, Nikolai F.; Polyansky, Oleg L.; Tennyson, Jonathan; Gamache, Robert R.; Szidarovszky, Tamás; Dénes, Nóra; Császár, Attila G.

    2017-06-01

    Accurate temperature-dependent ideal-gas internal partition functions, Qint(T), and several derived thermochemical functions are reported for heavy water, with an oxygen content corresponding to the isotopic composition of Vienna Standard Mean Ocean Water (VSMOW), and its constituent isotopologues, D216O, D217O, and D218O, for temperatures between 0 and 6000 K. The nuclear-spin-dependent partition functions are obtained by the direct summation technique, involving altogether about 16 000 measured and more than nine million computed bound rovibrational energy levels for the three molecules. Reliable standard uncertainties, as a function of temperature, are estimated for each thermochemical quantity determined, including the enthalpy, the entropy, and the isobaric heat capacity of the individual nuclear-spin-equilibrated isotopologues and of heavy water. The accuracy of the heavy-water ideal-gas Cp(T) is unprecedented, below 0.01% up to 1800 K. All the thermochemical functions are reported, in 1 K increments, in the supplementary material.

  15. Numerical estimation of ultrasonic production of hydrogen: Effect of ideal and real gas based models.

    PubMed

    Kerboua, Kaouther; Hamdaoui, Oualid

    2018-01-01

    Based on two different assumptions regarding the equation describing the state of the gases within an acoustic cavitation bubble, this paper studies the sonochemical production of hydrogen, through two numerical models treating the evolution of a chemical mechanism within a single bubble saturated with oxygen during an oscillation cycle in water. The first approach is built on an ideal gas model, while the second one is founded on Van der Waals equation, and the main objective was to analyze the effect of the considered state equation on the ultrasonic hydrogen production retrieved by simulation under various operating conditions. The obtained results show that even when the second approach gives higher values of temperature, pressure and total free radicals production, yield of hydrogen does not follow the same trend. When comparing the results released by both models regarding hydrogen production, it was noticed that the ratio of the molar amount of hydrogen is frequency and acoustic amplitude dependent. The use of Van der Waals equation leads to higher quantities of hydrogen under low acoustic amplitude and high frequencies, while employing ideal gas law based model gains the upper hand regarding hydrogen production at low frequencies and high acoustic amplitudes. Copyright © 2017 Elsevier B.V. All rights reserved.

  16. Collision of BEC dark matter structures and comparison with the collision of ideal gas structures

    SciTech Connect

    Guzman, F. S.; Gonzalez, J. A.

    2010-12-07

    In this work we present an important feature of the Bose Einstein Condensate (BEC) dark matter model, that is, the head-on collision of BEC dark matter virialized structures. This model of dark matter is assumed to be ruled by the Schroedinger-Poisson system of equations, which is interpreted as the Gross-Pitaevskii equation with a gravitational potential sourced by the density of probability. It has been shown recently that during the collision of two structures a pattern formation in the density of probability appears. We explore the pattern formation for various initial dynamical conditions during the collision. In order to know whether or not the pattern formation is a particular property of the BEC dark matter, we compare with the collision of two structures of virialized ideal gas under similar dynamical initial conditions, which is a model more consistent with usual models of dark matter. In order to do so, we also solve Euler's equations using a smoothed particle hydrodynamics approach. We found that the collision of the ideal gas structures does not show interference patterns, which in turn implies that the pattern formation is a property of the BEC dark matter.

  17. Cylindrical shock waves in rotational axisymmetric non-ideal dusty gas with increasing energy under the action of monochromatic radiation

    NASA Astrophysics Data System (ADS)

    Sahu, P. K.

    2017-08-01

    The propagation of a cylindrical shock wave in a rotational axisymmetric non-ideal dusty gas under the action of monochromatic radiation with increasing energy, which has variable azimuthal and axial components of fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. Similarity solutions are obtained as well as the effects of the variation of the radiation parameters, the parameter of non-idealness of the gas, the mass concentration of solid particles in the mixture, the ratio of the density of solid particles to the initial density of the gas, and the piston velocity index are worked out in detail. The total energy of the shock wave is varying and increases with time. It is observed that the radiation parameter and the piston velocity index have opposite behaviour on the flow variables as well as the shock strength.

  18. Propagation of exponential shock wave in an axisymmetric rotating non-ideal dusty gas

    NASA Astrophysics Data System (ADS)

    Nath, G.

    2016-09-01

    One-dimensional unsteady isothermal and adiabatic flow behind a strong exponential shock wave propagating in a rotational axisymmetric mixture of non-ideal gas and small solid particles, which has variable azimuthal and axial fluid velocities, is analyzed. The shock wave is driven out by a piston moving with time according to exponential law. The azimuthal and axial components of the fluid velocity in the ambient medium are assumed to be varying and obeying exponential laws. In the present work, small solid particles are considered as pseudo-fluid with the assumption that the equilibrium flow-conditions are maintained in the flow-field, and the viscous-stress and heat conduction of the mixture are negligible. Solutions are obtained in both the cases, when the flow between the shock and the piston is isothermal or adiabatic by taking into account the components of vorticity vector and compressibility. It is found that the assumption of zero temperature gradient brings a profound change in the density, axial component of vorticity vector and compressibility distributions as compared to that of the adiabatic case. To investigate the behavior of the flow variables and the influence on the shock wave propagation by the parameter of non-idealness of the gas overline{b} in the mixture as well as by the mass concentration of solid particles in the mixture Kp and by the ratio of the density of solid particles to the initial density of the gas G1 are worked out in detail. It is interesting to note that the shock strength increases with an increase in G1 ; whereas it decreases with an increase in overline{b} . Also, a comparison between the solutions in the cases of isothermal and adiabatic flows is made.

  19. Dip-Hump Temperature Dependence of Specific Heat and Effects of Pairing Fluctuations in the Weak-Coupling Side of a P-Wave Interacting Fermi Gas

    NASA Astrophysics Data System (ADS)

    Inotani, Daisuke; van Wyk, Pieter; Ohashi, Yoji

    2016-12-01

    We investigate the specific heat CV at constant volume in the normal state of a p-wave interacting Fermi gas. Including p-wave pairing fluctuations within the strong-coupling theory developed by Nozières and Schmitt-Rink, we show that, in the weak-coupling side, CV exhibits a dip-hump behavior as a function of the temperature. While the dip is associated with the pseudogap phenomenon near Tc, the hump structure is found to come from the suppression of Fermi quasiparticle scattering into a p-wave molecular state in the Fermi degenerate regime. Since the latter phenomenon does not occur in the ordinary s-wave interacting Fermi gas, it may be viewed as a characteristic phenomenon associated with a p-wave pairing interaction.

  20. Equation of State and Collective Frequencies of a Trapped Fermi Gas Along the BEC-Unitarity Crossover

    SciTech Connect

    Astrakharchik, G.E.; Combescot, R.; Leyronas, X.; Stringari, S.

    2005-07-15

    We show that the study of the collective oscillations in a harmonic trap provides a very sensitive test of the equation of state of a Fermi gas near a Feshbach resonance. Using a scaling approach, whose high accuracy is proven by comparison with exact hydrodynamic solutions, the frequencies of the lowest compressional modes are calculated at T=0 in terms of a dimensionless parameter characterizing the equation of state. The predictions for the collective frequencies, obtained from the equations of state of mean-field BCS theory and of recent Monte Carlo calculations, are discussed in detail.

  1. Density response of a trapped Fermi gas: A crossover from the pair vibration mode to the Goldstone mode

    SciTech Connect

    Korolyuk, A.; Kinnunen, J. J.; Toermae, P.

    2011-09-15

    We consider the density response of a trapped two-component Fermi gas. Combining the Bogoliubov-deGennes method with the random phase approximation allows the study of both collective and single-particle excitations. Calculating the density response across a wide range of interactions, we observe a crossover from a weakly interacting pair vibration mode to a strongly interacting Goldstone mode. The crossover is associated with a depressed collective mode frequency and an increased damping rate, in agreement with density response experiments performed in strongly interacting atomic gases.

  2. Condensate fraction of a resonant Fermi gas with spin-orbit coupling in three and two dimensions

    SciTech Connect

    Dell'Anna, L.; Mazzarella, G.; Salasnich, L.

    2011-09-15

    We study the effects of laser-induced Rashba-like spin-orbit coupling along the Bardeen-Cooper-Schrieffer-Bose-Einstein condensate (BCS-BEC) crossover of a Feshbach resonance for a two-spin-component Fermi gas. We calculate the condensate fraction in three and two dimensions and find that this quantity characterizes the crossover better than other quantities, like the chemical potential or the pairing gap. By considering both the singlet and the triplet pairings, we calculate the condensate fraction and show that a large-enough spin-orbit interaction enhances the singlet condensate fraction in the BCS side while suppressing it on the BEC side.

  3. A Complete 2D Stability Analysis of Fast MHD Shocks in an Ideal Gas

    NASA Astrophysics Data System (ADS)

    Trakhinin, Yuri

    An algorithm of numerical testing of the uniform Lopatinski condition for linearized stability problems for 1-shocks is suggested. The algorithm is used for finding the domains of uniform stability, neutral stability, and instability of planar fast MHD shocks. A complete stability analysis of fast MHD shock waves is first carried out in two space dimensions for the case of an ideal gas. Main results are given for the adiabatic constant γ=5/3 (mono-atomic gas), that is most natural for the MHD model. The cases γ=7/5 (two-atomic gas) and γ>5/3 are briefly discussed. Not only the domains of instability and linear (in the usual sense) stability, but also the domains of uniform stability, for which a corresponding linearized stability problem satisfies the uniform Lopatinski condition, are numerically found for different given angles of inclination of the magnetic field behind the shock to the planar shock front. As is known, uniform linearized stability implies the nonlinear stability, that is local existence of discontinuous shock front solutions of a quasilinear system of hyperbolic conservation laws.

  4. Isobars of an ideal Bose gas within the grand canonical ensemble

    SciTech Connect

    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.

  5. 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.

  6. Generic features of the wealth distribution in ideal-gas-like markets.

    PubMed

    Mohanty, P K

    2006-07-01

    We provide an exact solution to the ideal-gas-like models studied in econophysics to understand the microscopic origin of Pareto law. In these classes of models the key ingredient necessary for having a self-organized scale-free steady-state distribution is the trading or collision rule where agents or particles save a definite fraction of their wealth or energy and invest the rest for trading. Using a Gibbs ensemble approach we could obtain the exact distribution of wealth in this model. Moreover we show that in this model (a) good savers are always rich and (b) every agent poor or rich invests the same amount for trading. Nonlinear trading rules could alter the generic scenario observed here.

  7. 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.

  8. Configuration-specific kinetic theory applied to an ideal binary gas mixture.

    PubMed

    Wiseman, Floyd L

    2006-10-05

    This paper is the second in a two-part series dealing with the configuration-specific analyses for molecular collision events of hard, spherical molecules at thermal equilibrium. The first paper analyzed a single-component system, and the reader is referred to it for the fundamental concepts. In this paper, the expressions for the configuration-specific collision frequencies and the average line-of-centers collision angles and speeds are derived for an ideal binary gas mixture. The analyses show that the average line-of-centers quantities are all dependent upon the ratio of the masses of the two components, but not upon molecular size. Of course, the configuration-specific collision frequencies do depend on molecular size. The expression for the overall binary collision frequency is a simple sum of the configuration-specific collision frequencies and is identical to the conventional expression.

  9. Fluctuating ideal-gas lattice Boltzmann method with fluctuation dissipation theorem for nonvanishing velocities.

    PubMed

    Kaehler, G; Wagner, A J

    2013-06-01

    Current implementations of fluctuating ideal-gas descriptions with the lattice Boltzmann methods are based on a fluctuation dissipation theorem, which, while greatly simplifying the implementation, strictly holds only for zero mean velocity and small fluctuations. We show how to derive the fluctuation dissipation theorem for all k, which was done only for k=0 in previous derivations. The consistent derivation requires, in principle, locally velocity-dependent multirelaxation time transforms. Such an implementation is computationally prohibitively expensive but, with a small computational trick, it is feasible to reproduce the correct FDT without overhead in computation time. It is then shown that the previous standard implementations perform poorly for non vanishing mean velocity as indicated by violations of Galilean invariance of measured structure factors. Results obtained with the method introduced here show a significant reduction of the Galilean invariance violations.

  10. Heat-flow equation motivated by the ideal-gas shock wave.

    PubMed

    Holian, Brad Lee; Mareschal, Michel

    2010-08-01

    We present an equation for the heat-flux vector that goes beyond Fourier's Law of heat conduction, in order to model shockwave propagation in gases. Our approach is motivated by the observation of a disequilibrium among the three components of temperature, namely, the difference between the temperature component in the direction of a planar shock wave, versus those in the transverse directions. This difference is most prominent near the shock front. We test our heat-flow equation for the case of strong shock waves in the ideal gas, which has been studied in the past and compared to Navier-Stokes solutions. The new heat-flow treatment improves the agreement with nonequilibrium molecular-dynamics simulations of hard spheres under strong shockwave conditions.

  11. Determination of some pure compound ideal-gas enthalpies of formation

    SciTech Connect

    Steele, W. V.; Chirico, R. D.; Nguyen, A.; Hossenlopp, I. A.; Smith, N. K.

    1989-06-01

    The results of a study aimed at improvement of group-additivity methodology for estimation of thermodynamic properties of organic substances are reported. Specific weaknesses where ring corrections were unknown or next-nearest-neighbor interactions were only estimated because of lack of experimental data are addressed by experimental studies of enthalpies of combustion in the condensed- phase and vapor pressure measurements. Ideal-gas enthalpies of formation are reported for acrylamide, succinimide, ..gamma..-butyrolactone, 2-pyrrolidone, 2,3-dihydrofuran, 3,4-dihydro-2H-pyran, 1,3-cyclohexadiene, 1,4-cyclohexadiene, and 1-methyl-1-phenylhydrazine. Ring corrections, group terms, and next-nearest-neighbor interaction terms useful in the application of group additivity correlations are derived. 44 refs., 2 figs., 59 tabs.

  12. Definitive Ideal-Gas Thermochemical Functions of the H216O Molecule

    NASA Astrophysics Data System (ADS)

    Furtenbacher, Tibor; Szidarovszky, Tamás; Hrubý, Jan; Kyuberis, Aleksandra A.; Zobov, Nikolai F.; Polyansky, Oleg L.; Tennyson, Jonathan; Császár, Attila G.

    2016-12-01

    A much improved temperature-dependent ideal-gas internal partition function, Qint(T), of the H216O molecule is reported for temperatures between 0 and 6000 K. Determination of Qint(T) is principally based on the direct summation technique involving all accurate experimental energy levels known for H216O (almost 20 000 rovibrational energies including an almost complete list up to a relative energy of 7500 cm-1), augmented with a less accurate but complete list of first-principles computed rovibrational energy levels up to the first dissociation limit, about 41 000 cm-1 (the latter list includes close to one million bound rovibrational energy levels up to J = 69, where J is the rotational quantum number). Partition functions are developed for ortho- and para-H216O as well as for their equilibrium mixture. Unbound rovibrational states of H216O above the first dissociation limit are considered using an approximate model treatment. The effect of the excited electronic states on the thermochemical functions is neglected, as their contribution to the thermochemical functions is negligible even at the highest temperatures considered. Based on the high-accuracy Qint(T) and its first two moments, definitive results, in 1 K increments, are obtained for the following thermochemical functions: Gibbs energy, enthalpy, entropy, and isobaric heat capacity. Reliable uncertainties (approximately two standard deviations) are estimated as a function of temperature for each quantity determined. These uncertainties emphasize that the present results are the most accurate ideal-gas thermochemical functions ever produced for H216O. It is recommended that the new value determined for the standard molar enthalpy increment at 298.15 K, 9.904 04 ± 0.000 01 kJ mol-1, should replace the old CODATA datum, 9.905 ± 0.005 kJ mol-1.

  13. Spin susceptibility and effects of a harmonic trap in the BCS-BEC crossover regime of an ultracold Fermi gas

    NASA Astrophysics Data System (ADS)

    Tajima, Hiroyuki; Hanai, Ryo; Ohashi, Yoji

    2017-09-01

    We theoretically investigate magnetic properties of a trapped ultracold Fermi gas. Including pairing fluctuations within the framework of an extended T -matrix approximation, as well as effects of a harmonic trap in the local density approximation, we calculate the local spin susceptibility χt(r ,T ) in the Bardeen-Cooper-Schrieffer-Bose-Einstein condensation crossover region. We show that pairing fluctuations cause nonmonotonic temperature dependence of χt(r ,T ) . Although this behavior looks similar to the spin-gap phenomenon associated with pairing fluctuations in a uniform Fermi gas, the trapped case is found to also be influenced by the temperature-dependent density profile, in addition to pairing fluctuations. We demonstrate how to remove this extrinsic effect from χt(r ,T ) , to study the interesting spin-gap phenomenon purely originating from pairing fluctuations. Since experiments in cold-atom physics are always done in a trap, our results would be useful for the assessment of preformed pair scenario, from the viewpoint of spin-gap phenomenon.

  14. Manifestly Hermitian semiclassical expansion for the one-particle density matrix of a two-dimensional Fermi gas

    NASA Astrophysics Data System (ADS)

    Bencheikh, K.; van Zyl, B. P.; Berkane, K.

    2016-08-01

    The semiclassical ℏ expansion of the one-particle density matrix for a two-dimensional Fermi gas is calculated within the Wigner transform method of B. Grammaticos and A. Voros [Ann. Phys. (N.Y.) 123, 359 (1979), 10.1016/0003-4916(79)90343-9], originally developed in the context of nuclear physics. The method of Grammaticos and Voros has the virtue of preserving both the Hermiticity and idempotency of the density matrix to all orders in the ℏ expansion. As a topical application, we use our semiclassical expansion to go beyond the local-density approximation for the construction of the total dipole-dipole interaction energy functional of a two-dimensional, spin-polarized dipolar Fermi gas. We find a finite, second-order gradient correction to the Hartree-Fock energy, which takes the form ɛ (∇ρ ) 2/√{ρ } , with ɛ being small (|ɛ |≪1 ) and negative. We test the quality of the corrected energy by comparing it with the exact results available for harmonic confinement. Even for small particle numbers, the gradient correction to the dipole-dipole energy provides a significant improvement over the local-density approximation.

  15. Pseudogap Phenomena Near the BKT Transition of a Two-Dimensional Ultracold Fermi Gas in the Crossover Region

    NASA Astrophysics Data System (ADS)

    Matsumoto, M.; Hanai, R.; Inotani, D.; Ohashi, Y.

    2017-06-01

    We investigate strong-coupling properties of a two-dimensional ultracold Fermi gas in the normal phase. In the three-dimensional case, it has been shown that the so-called pseudogap phenomena can be well described by a (non-self-consistent) T-matrix approximation (TMA). In the two-dimensional case, while this strong-coupling theory can explain the pseudogap phenomenon in the strong-coupling regime, it unphysically gives large pseudogap size in the crossover region, as well as in the weak-coupling regime. We show that this difficulty can be overcome when one improves TMA to include higher-order pairing fluctuations within the framework of a self-consistent T-matrix approximation (SCTMA). The essence of this improvement is also explained. Since the observation of the BKT transition has recently been reported in a two-dimensional ^6{Li} Fermi gas, our results would be useful for the study of strong-coupling physics associated with this quasi-long-range order.

  16. Numerical solutions of ideal quantum gas dynamical flows governed by semiclassical ellipsoidal-statistical distribution

    PubMed Central

    Yang, Jaw-Yen; Yan, Chih-Yuan; Diaz, Manuel; Huang, Juan-Chen; Li, Zhihui; Zhang, Hanxin

    2014-01-01

    The ideal quantum gas dynamics as manifested by the semiclassical ellipsoidal-statistical (ES) equilibrium distribution derived in Wu et al. (Wu et al. 2012 Proc. R. Soc. A 468, 1799–1823 (doi:10.1098/rspa.2011.0673)) is numerically studied for particles of three statistics. This anisotropic ES equilibrium distribution was derived using the maximum entropy principle and conserves the mass, momentum and energy, but differs from the standard Fermi–Dirac or Bose–Einstein distribution. The present numerical method combines the discrete velocity (or momentum) ordinate method in momentum space and the high-resolution shock-capturing method in physical space. A decoding procedure to obtain the necessary parameters for determining the ES distribution is also devised. Computations of two-dimensional Riemann problems are presented, and various contours of the quantities unique to this ES model are illustrated. The main flow features, such as shock waves, expansion waves and slip lines and their complex nonlinear interactions, are depicted and found to be consistent with existing calculations for a classical gas. PMID:24399919

  17. Slippage and boundary layer probed in an almost ideal gas by a nanomechanical oscillator.

    PubMed

    Defoort, M; Lulla, K J; Crozes, T; Maillet, O; Bourgeois, O; Collin, E

    2014-09-26

    We measure the interaction between ⁴He gas at 4.2 K and a high-quality nanoelectromechanical string device for its first three symmetric modes (resonating at 2.2, 6.7, and 11 MHz with quality factor Q>0.1×10⁶) over almost 6 orders of magnitude in pressure. This fluid can be viewed as the best experimental implementation of an almost ideal monoatomic and inert gas of which properties are tabulated. The experiment ranges from high pressure where the flow is of laminar Stokes-type presenting slippage down to very low pressures where the flow is molecular. In the molecular regime, when the mean-free path is of the order of the distance between the suspended nanomechanical probe and the bottom of the trench, we resolve for the first time the signature of the boundary (Knudsen) layer onto the measured dissipation. Our results are discussed in the framework of the most recent theories investigating boundary effects in fluids (both analytic approaches and direct simulation Monte Carlo methods).

  18. Smoothed MHD equations for numerical simulations of ideal quasi-neutral gas dynamic flows

    NASA Astrophysics Data System (ADS)

    Popov, Mikhail V.; Elizarova, Tatiana G.

    2015-11-01

    We introduce a mathematical model and related numerical method for numerical modeling of ideal magnetohydrodynamic (MHD) gas flows as an extension of previously known quasi-gasdynamic (QGD) equations. This approach is based on smoothing, or averaging of the original MHD equation system over a small time interval that leads to a new equation system, named quasi-MHD, or QMHD system. The QMHD equations are closely related to the original MHD system except for additional strongly non-linear dissipative τ-terms with a small parameter τ as a factor. The τ-terms depend on the solution itself and decrease in regions with the small space gradients of the solution. In this sense the QMHD system could be regarded as an approach with adaptive artificial dissipation. The QMHD is a generalization of regularized (or quasi-) gas dynamic equation system suggested in last three decades. In the QMHD numerical method the evolution of all physical variables is presented in a non-split divergence form. Divergence-free evolution of the magnetic field provides by using a constrained transport method based on Faraday's law of induction. Accuracy and convergence of the QMHD method is verified on a wide set of standard MHD tests including the 3D Orszag-Tang vortex flow.

  19. Single-particle spectral density of the unitary Fermi gas: Novel approach based on the operator product expansion, sum rules and the maximum entropy method

    SciTech Connect

    Gubler, Philipp; Yamamoto, Naoki; Hatsuda, Tetsuo; Nishida, Yusuke

    2015-05-15

    Making use of the operator product expansion, we derive a general class of sum rules for the imaginary part of the single-particle self-energy of the unitary Fermi gas. The sum rules are analyzed numerically with the help of the maximum entropy method, which allows us to extract the single-particle spectral density as a function of both energy and momentum. These spectral densities contain basic information on the properties of the unitary Fermi gas, such as the dispersion relation and the superfluid pairing gap, for which we obtain reasonable agreement with the available results based on quantum Monte-Carlo simulations.

  20. Induced Interactions and the Superfluid Transition Temperature in a Three-Component Fermi Gas

    SciTech Connect

    Martikainen, J.-P.; Kinnunen, J. J.; Toermae, P.; Pethick, C. J.

    2009-12-31

    We study many-body contributions to the effective interaction between fermions in a three-component Fermi mixture. We find that effective interactions induced by the third component can lead to a phase diagram different from that predicted if interactions with the third component are neglected. As a result, in a confining potential a superfluid shell structure can arise even for equal populations of the components. We also find a critical temperature for the BCS transition in a {sup 6}Li mixture which can deviate strongly from the one in a weakly interacting two-component system.

  1. Collisions of ideal gas molecules with a rough/fractal surface. A computational study.

    PubMed

    Panczyk, Tomasz

    2007-02-01

    The frequency of collisions of ideal gas molecules (argon) with a rough surface has been studied. The rough/fractal surface was created using random deposition technique. By applying various depositions, the roughness of the surface was controlled and, as a measure of the irregularity, the fractal dimensions of the surfaces were determined. The surfaces were next immersed in argon (under pressures 2 x 10(3) to 2 x 10(5) Pa) and the numbers of collisions with these surfaces were counted. The calculations were carried out using a simplified molecular dynamics simulation technique (only hard core repulsions were assumed). As a result, it was stated that the frequency of collisions is a linear function of pressure for all fractal dimensions studied (D = 2, ..., 2.5). The frequency per unit pressure is quite complex function of the fractal dimension; however, the changes of that frequency with the fractal dimension are not strong. It was found that the frequency of collisions is controlled by the number of weakly folded sites on the surfaces and there is some mapping between the shape of adsorption energy distribution functions and this number of weakly folded sites. The results for the rough/fractal surfaces were compared with the prediction given by the Langmuir-Hertz equation (valid for smooth surface), generally the departure from the Langmuir-Hertz equation is not higher than 48% for the studied systems (i.e. for the surfaces created using the random deposition technique).

  2. Thermodynamics of an ideal generalized gas: II. Means of order alpha.

    PubMed

    Lavenda, B H

    2005-11-01

    The property that power means are monotonically increasing functions of their order is shown to be the basis of the second laws not only for processes involving heat conduction, but also for processes involving deformations. This generalizes earlier work involving only pure heat conduction and underlines the incomparability of the internal energy and adiabatic potentials when expressed as powers of the adiabatic variable. In an L-potential equilibration, the final state will be one of maximum entropy, whereas in an entropy equilibration, the final state will be one of minimum L. Unlike classical equilibrium thermodynamic phase space, which lacks an intrinsic metric structure insofar as distances and other geometrical concepts do not have an intrinsic thermodynamic significance in such spaces, a metric space can be constructed for the power means: the distance between means of different order is related to the Carnot efficiency. In the ideal classical gas limit, the average change in the entropy is shown to be proportional to the difference between the Shannon and Rényi entropies for nonextensive systems that are multifractal in nature. The L potential, like the internal energy, is a Schur convex function of the empirical temperature, which satisfies Jensen's inequality, and serves as a measure of the tendency to uniformity in processes involving pure thermal conduction.

  3. Determination of ideal-gas enthalpies of formation for key compounds:

    SciTech Connect

    Steele, W.V.; Chirico, R.D.; Nguyen, A.; Hossenlopp, I.A.; Smith, N.K.

    1991-10-01

    The results of a study aimed at improvement of group-contribution methodology for estimation of thermodynamic properties of organic and organosilicon substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in the condensed phase, vapor-pressure measurements, and differential scanning calorimetric (d.s.c.) heat-capacity measurements. Ideal-gas enthalpies of formation of ({plus minus})-butan-2-ol, tetradecan-1-ol, hexan-1,6-diol, methacrylamide, benzoyl formic acid, naphthalene-2,6-dicarboxylic acid dimethyl ester, and tetraethylsilane are reported. A crystalline-phase enthalpy of formation at 298.15 K was determined for naphthalene-2,6-dicarboxylic acid, which decomposed at 695 K before melting. The combustion calorimetry of tetraethylsilane used the proven fluorine-additivity methodology. Critical temperature and critical density were determined for tetraethylsilane with differential scanning calorimeter and the critical pressure was derived. Group-additivity parameters useful in the application of group- contribution correlations are derived. 112 refs., 13 figs., 19 tabs.

  4. Path integral Monte Carlo determination of the fourth-order virial coefficient for unitary two-component Fermi gas with zero-range interactions

    NASA Astrophysics Data System (ADS)

    Yan, Yangqian; Blume, D.

    2016-05-01

    The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astro physics. This work determines the fourth-order virial coefficient b4 of such a strongly-interacting Fermi gas using a customized ab inito path integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b4, our b4 agrees with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly anti-symmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions. We gratefully acknowledge support by the NSF.

  5. Path-Integral Monte Carlo Determination of the Fourth-Order Virial Coefficient for a Unitary Two-Component Fermi Gas with Zero-Range Interactions

    NASA Astrophysics Data System (ADS)

    Yan, Yangqian; Blume, D.

    2016-06-01

    The unitary equal-mass Fermi gas with zero-range interactions constitutes a paradigmatic model system that is relevant to atomic, condensed matter, nuclear, particle, and astrophysics. This work determines the fourth-order virial coefficient b4 of such a strongly interacting Fermi gas using a customized ab initio path-integral Monte Carlo (PIMC) algorithm. In contrast to earlier theoretical results, which disagreed on the sign and magnitude of b4 , our b4 agrees within error bars with the experimentally determined value, thereby resolving an ongoing literature debate. Utilizing a trap regulator, our PIMC approach determines the fourth-order virial coefficient by directly sampling the partition function. An on-the-fly antisymmetrization avoids the Thomas collapse and, combined with the use of the exact two-body zero-range propagator, establishes an efficient general means to treat small Fermi systems with zero-range interactions.

  6. University Students Explaining Adiabatic Compression of an Ideal Gas--A New Phenomenon in Introductory Thermal Physics

    ERIC Educational Resources Information Center

    Leinonen, Risto; Asikainen, Mervi A.; Hirvonen, Pekka E.

    2012-01-01

    This study focuses on second-year university students' explanations and reasoning related to adiabatic compression of an ideal gas. The phenomenon was new to the students, but it was one which they should have been capable of explaining using their previous upper secondary school knowledge. The students' explanations and reasoning were…

  7. University Students Explaining Adiabatic Compression of an Ideal Gas--A New Phenomenon in Introductory Thermal Physics

    ERIC Educational Resources Information Center

    Leinonen, Risto; Asikainen, Mervi A.; Hirvonen, Pekka E.

    2012-01-01

    This study focuses on second-year university students' explanations and reasoning related to adiabatic compression of an ideal gas. The phenomenon was new to the students, but it was one which they should have been capable of explaining using their previous upper secondary school knowledge. The students' explanations and reasoning were…

  8. Reduction of furnace temperature in ultra long carbon nanotube growth by plasmonic excitation of electron Fermi gas of catalytic nanocluster

    SciTech Connect

    Saeidi, Mohammadreza E-mail: m.saeidi@shahed.ac.ir

    2016-06-15

    In this paper, a novel physical method is presented to reduce the temperature of the furnace and prevent loss of thermal energy in ultra long carbon nanotube (CNT) growth process by catalytic chemical vapor deposition. This method is based on the plasmonic excitation of electron Fermi gas of catalytic nanocluster sitting at tip end of CNT by ultraviolet (UV) irradiation. Physical concepts of the method are explained in detail. The results of applying the presented method consequences to an appropriate tip-growth mechanism of the ultra long CNTs show that, in the presence of plasmonic excitation, the growth rate of the CNT is enhanced. Demonstration of temperature reduction and simultaneous increase in CNT length by UV irradiation with the proper frequency are the most important and practical result of the paper. All results are interpreted and discussed.

  9. Cascade of Solitonic Excitations in a Superfluid Fermi gas: From Planar Solitons to Vortex Rings and Lines

    NASA Astrophysics Data System (ADS)

    Ku, Mark J. H.; Mukherjee, Biswaroop; Yefsah, Tarik; Zwierlein, Martin W.

    2016-01-01

    We follow the time evolution of a superfluid Fermi gas of resonantly interacting 6 atoms after a phase imprint. Via tomographic imaging, we observe the formation of a planar dark soliton, its subsequent snaking, and its decay into a vortex ring, which, in turn, breaks to finally leave behind a single solitonic vortex. In intermediate stages, we find evidence for an exotic structure resembling the Φ soliton, a combination of a vortex ring and a vortex line. Direct imaging of the nodal surface reveals its undulation dynamics and its decay via the puncture of the initial soliton plane. The observed evolution of the nodal surface represents dynamics beyond superfluid hydrodynamics, calling for a microscopic description of unitary fermionic superfluids out of equilibrium.

  10. Equation of state of a polarized Fermi gas in the Bose-Einstein-condensate limit

    SciTech Connect

    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.

  11. Spin-anisotropic magnetic impurity in a Fermi gas: Integration of poor man's scaling equations

    NASA Astrophysics Data System (ADS)

    Kogan, Eugene; Noda, Kazuto; Yunoki, Seiji

    2017-04-01

    We consider a single magnetic impurity described by the spin-anisotropic s -d (f ) exchange (Kondo) model and formulate a scaling equation for the spin-anisotropic model when the density of states (DOS) of electrons is a power-law function of energy (measured relative to the Fermi energy). We solve this equation containing terms up to the second order in coupling constants in terms of elliptic functions. From the obtained solution we find the phases corresponding to the infinite isotropic antiferromagnetic Heisenberg exchange, to the impurity spin decoupled from the electron environment (only for the pseudogap DOS), and to the infinite Ising exchange (only for the diverging DOS). We analyze the critical surfaces, corresponding to the finite isotropic antiferromagnetic Heisenberg exchange for the pseudogap DOS.

  12. Interplay between Rashba spin-orbit coupling and adiabatic rotation in a two-dimensional Fermi gas

    NASA Astrophysics Data System (ADS)

    Doko, E.; Subaşı, A. L.; Iskin, M.

    2017-01-01

    We explore the trap profiles of a two-dimensional atomic Fermi gas in the presence of a Rashba spin-orbit coupling and under an adiabatic rotation. We first consider a noninteracting gas and show that the competition between the effects of Rashba coupling on the local density of single-particle states and the Coriolis effects caused by rotation gives rise to a characteristic ring-shaped density profile that survives at experimentally accessible temperatures. Furthermore, Rashba splitting of the Landau levels gives the density profiles a ziggurat shape in the rapid-rotation limit. We then consider an interacting gas under the BCS mean-field approximation for local pairing, and study the pair-breaking mechanism that is induced by the Coriolis effects on superfluidity, where we calculate the critical rotation frequencies both for the onset of pair breaking and for the complete destruction of superfluidity in the system. In particular, by comparing the results of a fully-quantum-mechanical Bogoliubov-de Gennes approach with those of a semiclassical local-density approximation, we construct extensive phase diagrams for a wide range of parameter regimes in the trap where the aforementioned competition may, e.g., favor an outer normal edge that is completely phase separated from the central superfluid core by vacuum.

  13. Finite-density corrections to the unitary Fermi gas: A lattice perspective from dynamical mean-field theory

    SciTech Connect

    Privitera, Antonio; Capone, Massimo; Castellani, Claudio

    2010-01-01

    We investigate the approach to the universal regime of the dilute unitary Fermi gas as the density is reduced to zero in a lattice model. To this end we study the chemical potential, superfluid order parameter and internal energy of the attractive Hubbard model in three different lattices with densities of states (DOSs) which share the same low-energy behavior of fermions in three-dimensional free space: a cubic lattice, a 'Bethe lattice' with a semicircular DOS, and a 'lattice gas' with parabolic dispersion and a sharp energy cutoff that ensures the normalization of the DOS. The model is solved using dynamical mean-field theory, that treats directly the thermodynamic limit and arbitrarily low densities, eliminating finite-size effects. At densities on the order of one fermion per site the lattice and its specific form dominate the results. The evolution to the low-density limit is smooth and it does not allow to define an unambiguous low-density regime. Such finite-density effects are significantly reduced using the lattice gas, and they are maximal for the three-dimensional cubic lattice. Even though dynamical mean-field theory is bound to reduce to the more standard static mean field in the limit of zero density due to the local nature of the self-energy and of the vertex functions, it compares well with accurate Monte Carlo simulations down to the lowest densities accessible to the latter.

  14. The role of multiparticle correlations and Cooper pairing in the formation of molecules in an ultracold gas of Fermi atoms with a negative scattering length

    SciTech Connect

    Babichenko, V. S. Kagan, Yu.

    2012-11-15

    The influence of multiparticle correlation effects and Cooper pairing in an ultracold Fermi gas with a negative scattering length on the formation rate of molecules is investigated. Cooper pairing is shown to cause the formation rate of molecules to increase, as distinct from the influence of Bose-Einstein condensation in a Bose gas on this rate. This trend is retained in the entire range of temperatures below the critical one.

  15. Pure Goldstone mode in the quench dynamics of a confined ultracold Fermi gas in the BCS-BEC crossover regime

    NASA Astrophysics Data System (ADS)

    Kettmann, P.; Hannibal, S.; Croitoru, M. D.; Axt, V. M.; Kuhn, T.

    2017-09-01

    We present a numerical study of the dynamic response of a confined superfluid Fermi gas to a rapid change of the scattering length (i.e., an interaction quench). Based on a fully microscopic time-dependent density-matrix approach within the full Bogoliubov-de Gennes formalism that includes a 3D harmonic confinement we simulate and identify the emergence of a Goldstone mode of the BCS gap in a cigar-shaped 6Li gas. By analyzing this Goldstone mode over a wide range of parameters, we show that its excitation spectrum is gapless and that its main frequency is not fixed by the trapping potential but that it is determined by the details of the quench. Thus we report the emergence of a pure Goldstone mode of the BCS gap that—in contrast to situations in many previous studies—maintains its gapless excitation spectrum predicted by the Goldstone theorem. Furthermore, we observe that the size-dependent superfluid resonances resulting from the atypical BCS-BEC crossover have a direct impact on this Goldstone mode. Finally, we find that the interaction quench-induced Goldstone mode leads to a low-frequency in-phase oscillation of the single-particle occupations with complete inversion of the lowest-lying single-particle states which could provide a convenient experimental access to the pure gapless Goldstone mode.

  16. Interaction energy and itinerant ferromagnetism in a strongly interacting Fermi gas in the absence of molecule formation

    SciTech Connect

    He, Lianyi

    2014-11-26

    In this study, we investigate the interaction energy and the possibility of itinerant ferromagnetism in a strongly interacting Fermi gas at zero temperature in the absence of molecule formation. The interaction energy is obtained by summing the perturbative contributions of Galitskii-Feynman type to all orders in the gas parameter. It can be expressed by a simple phase-space integral of an in-medium scattering phase shift. In both three and two dimensions (3D and 2D), the interaction energy shows a maximum before reaching the resonance from the Bose-Einstein condensate side, which provides a possible explanation of the experimental measurements of the interaction energy. This phenomenon can be theoretically explained by the qualitative change of the nature of the binary interaction in the medium. The appearance of an energy maximum has significant effects on the itinerant ferromagnetism. In 3D, the ferromagnetic transition is reentrant and itinerant ferromagnetism exists in a narrow window around the energy maximum. In 2D, the present theoretical approach suggests that itinerant ferromagnetism does not exist, which reflects the fact that the energy maximum becomes much lower than the energy of the fully polarized state.

  17. Interaction energy and itinerant ferromagnetism in a strongly interacting Fermi gas in the absence of molecule formation

    DOE PAGES

    He, Lianyi

    2014-11-26

    In this study, we investigate the interaction energy and the possibility of itinerant ferromagnetism in a strongly interacting Fermi gas at zero temperature in the absence of molecule formation. The interaction energy is obtained by summing the perturbative contributions of Galitskii-Feynman type to all orders in the gas parameter. It can be expressed by a simple phase-space integral of an in-medium scattering phase shift. In both three and two dimensions (3D and 2D), the interaction energy shows a maximum before reaching the resonance from the Bose-Einstein condensate side, which provides a possible explanation of the experimental measurements of the interactionmore » energy. This phenomenon can be theoretically explained by the qualitative change of the nature of the binary interaction in the medium. The appearance of an energy maximum has significant effects on the itinerant ferromagnetism. In 3D, the ferromagnetic transition is reentrant and itinerant ferromagnetism exists in a narrow window around the energy maximum. In 2D, the present theoretical approach suggests that itinerant ferromagnetism does not exist, which reflects the fact that the energy maximum becomes much lower than the energy of the fully polarized state.« less

  18. Bose-Einstein condensation of heteronuclear bound states formed in a Fermi gas of two atomic species: a microscopic approach

    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.

  19. Magnetogasdynamic spherical shock wave in a non-ideal gas under gravitational field with conductive and radiative heat fluxes

    NASA Astrophysics Data System (ADS)

    Nath, G.; Vishwakarma, J. P.

    2016-11-01

    Similarity solutions are obtained for the flow behind a spherical shock wave in a non-ideal gas under gravitational field with conductive and radiative heat fluxes, in the presence of a spatially decreasing azimuthal magnetic field. The shock wave is driven by a piston moving with time according to power law. The radiation is considered to be of the diffusion type for an optically thick grey gas model and the heat conduction is expressed in terms of Fourier's law for heat conduction. Similarity solutions exist only when the surrounding medium is of constant density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. It is shown that an increase of the gravitational parameter or the Alfven-Mach number or the parameter of the non-idealness of the gas decreases the compressibility of the gas in the flow-field behind the shock, and hence there is a decrease in the shock strength. The pressure and density vanish at the inner surface (piston) and hence a vacuum is formed at the center of symmetry. The shock waves in conducting non-ideal gas under gravitational field with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of a flare produced shock in the solar wind, central part of star burst galaxies, nuclear explosion etc. The solutions obtained can be used to interpret measurements carried out by space craft in the solar wind and in neighborhood of the Earth's magnetosphere.

  20. A new method for the measurement of meteorite bulk volume via ideal gas pycnometry

    NASA Astrophysics Data System (ADS)

    Li, Shijie; Wang, Shijie; Li, Xiongyao; Li, Yang; Liu, Shen; Coulson, Ian M.

    2012-10-01

    To date, of the many techniques used to measure the bulk volume of meteorites, only three methods (Archimedean bead method, 3-D laser imaging and X-ray microtomography) can be considered as nondestructive or noncontaminating. The bead method can show large, random errors for sample sizes of smaller than 5 cm3. In contrast, 3-D laser imaging is a high-accuracy method even when measuring the bulk volumes of small meteorites. This method is both costly and time consuming, however, and meteorites of a certain shape may lead to some uncertainties in the analysis. The method of X-ray microtomography suffers from the same problems as 3-D laser imaging. This study outlines a new method of high-accuracy, nondestructive and noncontaminating measurement of the bulk volume of meteorite samples. In order to measure the bulk volume of a meteorite, one must measure the total volume of the balloon vacuum packaged meteorite and the volume of balloon that had been used to enclose the meteorite using ideal gas pycnometry. The difference between the two determined volumes is the bulk volume of the meteorite. Through the measurement of zero porosity metal spheres and tempered glass fragments, our results indicate that for a sample which has a volume of between 0.5 and 2 cm3, the relative error of the measurement is less than ±0.6%. Furthermore, this error will be even smaller (less than ±0.1%) if the determined sample size is larger than 2 cm3. The precision of this method shows some volume dependence. For samples smaller than 1 cm3, the standard deviations are less than ±0.328%, and these values will fall to less than ±0.052% for samples larger than 2 cm3. The porosities of nine fragments of Jilin, GaoGuenie, Zaoyang and Zhaodong meteorites have been measured using our vacuum packaging-pycnometry method, with determined average porosities of Jilin, GaoGuenie, Zaoyang and Zhaodong of 9.0307%, 2.9277%, 17.5437% and 5.9748%, respectively. These values agree well with the porosities

  1. University student reasoning about the basic tenets of kinetic-molecular theory, Part II: Pressure of an ideal gas

    NASA Astrophysics Data System (ADS)

    Robertson, Amy D.; Shaffer, Peter S.

    2016-10-01

    We report the common justifications that university physics and chemistry students use to reason about changes in the pressure of an ideal gas from a microscopic perspective, based on our analysis of written responses from more than one thousand students. We find that these justifications vary in the extent to which they are (a) mechanistic and (b) consistent with kinetic-molecular theory. We propose that these ideas could serve as the basis for instruction and curriculum development that attends to student thinking.

  2. Matter-wave Fourier optics with a strongly interacting two-dimensional Fermi gas

    NASA Astrophysics Data System (ADS)

    Murthy, P. A.; Kedar, D.; Lompe, T.; Neidig, M.; Ries, M. G.; Wenz, A. N.; Zürn, G.; Jochim, S.

    2014-10-01

    We demonstrate and characterize an experimental technique to directly image the momentum distribution of a strongly interacting two-dimensional quantum gas with high momentum resolution. We apply the principles of Fourier optics to investigate three main operations on the expanding gas: focusing, collimation, and magnification. We focus the gas in the radial plane using a harmonic confining potential and thus gain access to the momentum distribution. We pulse a different harmonic potential to stop the rapid axial expansion, which allows us to image the momentum distribution with high resolution. Additionally, we propose a method to magnify the mapped momentum distribution to access interesting momentum scales. All these techniques can be applied to a wide range of experiments, and in particular to study many-body phases of quantum gases.

  3. Validation of the Jarzynski relation for a system with strong thermal coupling: an isothermal ideal gas model.

    PubMed

    Baule, A; Evans, R M L; Olmsted, P D

    2006-12-01

    We revisit the paradigm of an ideal gas under isothermal conditions. A moving piston performs work on an ideal gas in a container that is strongly coupled to a heat reservoir. The thermal coupling is modeled by stochastic scattering at the boundaries. In contrast to recent studies of an adiabatic ideal gas with a piston [R.C. Lua and A.Y. Grosberg, J. Phys. Chem. B 109, 6805 (2005); I. Bena, Europhys. Lett. 71, 879 (2005)], the container and piston stay in contact with the heat bath during the work process. Under this condition the heat reservoir as well as the system depend on the work parameter lambda and microscopic reversibility is broken for a moving piston. Our model is thus not included in the class of systems for which the nonequilibrium work theorem has been derived rigorously either by Hamiltonian [C. Jarzynski, J. Stat. Mech. (2004) P09005] or stochastic methods [G.E. Crooks, J. Stat. Phys. 90, 1481 (1998)]. Nevertheless the validity of the nonequilibrium work theorem is confirmed both numerically for a wide range of parameter values and analytically in the limit of a very fast moving piston, i.e., in the far nonequilibrium regime.

  4. Quasi-1D Superfluids In A Spin-Imbalanced Fermi Gas

    NASA Astrophysics Data System (ADS)

    Revelle, Melissa C.; Olsen, Ben A.; Fry, Jacob A.; Hulet, Randall G.

    2015-05-01

    We experimentally study the phases of an ultracold two-spin component gas of atomic fermions (6Li) confined to 1D tubes formed by a 2D optical lattice. The atoms are prepared in the lowest two hyperfine sublevels where their interactions are tuned by a Feshbach resonance. We previously observed phase separation into a partially-polarized superfluid core and either fully-paired or fully-polarized wings (depending on the spin polarization). In 3D, the phase separation is inverted, such that the cloud center is fully paired. We investigate the transition from a 1D to 3D gas by varying the lattice depth and interaction strength which changes the ratio of the tunneling rate between the tubes to the pair binding energy. The region of parameter space we are exploring is believed to be the most promising region for the exotic FFLO superfluid phase. Supported by ARO, NSF, ONR, and the Welch Foundation.

  5. 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.

  6. Transition and Damping of Collective Modes in a Trapped Fermi Gas between BCS and Unitary Limits near the Phase Transition

    PubMed Central

    Dong, Hang; Zhang, Wenyuan; Zhou, Li; Ma, Yongli

    2015-01-01

    We investigate the transition and damping of low-energy collective modes in a trapped unitary Fermi gas by solving the Boltzmann-Vlasov kinetic equation in a scaled form, which is combined with both the T-matrix fluctuation theory in normal phase and the mean-field theory in order phase. In order to connect the microscopic and kinetic descriptions of many-body Feshbach scattering, we adopt a phenomenological two-fluid physical approach, and derive the coupling constants in the order phase. By solving the Boltzmann-Vlasov steady-state equation in a variational form, we calculate two viscous relaxation rates with the collision probabilities of fermion’s scattering including fermions in the normal fluid and fermion pairs in the superfluid. Additionally, by considering the pairing and depairing of fermions, we get results of the frequency and damping of collective modes versus temperature and s-wave scattering length. Our theoretical results are in a remarkable agreement with the experimental data, particularly for the sharp transition between collisionless and hydrodynamic behaviour and strong damping between BCS and unitary limits near the phase transition. The sharp transition originates from the maximum of viscous relaxation rate caused by fermion-fermion pair collision at the phase transition point when the fermion depair, while the strong damping due to the fast varying of the frequency of collective modes from BCS limit to unitary limit. PMID:26522094

  7. Linear response of heat conductivity of normal-superfluid interface of a polarized Fermi gas to orbital magnetic field

    NASA Astrophysics Data System (ADS)

    Ebrahimian, N.; Mehrafarin, M.; Afzali, R.

    2012-01-01

    Using perturbed Bogoliubov equations, we study the linear response to a weak orbital magnetic field of the heat conductivity of the normal-superfluid interface of a polarized Fermi gas at sufficiently low temperature. We consider the various scattering regions of the BCS regime and analytically obtain the transmission coefficients and the heat conductivity across the interface in an arbitrary weak orbital field. For a definite choice of the field, we consider various values of the scattering length in the BCS range and numerically obtain the allowed values of the average and species-imbalance chemical potentials. Thus, taking Andreev reflection into account, we describe how the heat conductivity is affected by the field and the species imbalance. In particular, we show that the additional heat conductivity due to the orbital field increases with the species imbalance, which is more noticeable at higher temperatures. Our results indicate how the heat conductivity may be controlled, which is relevant to sensitive magnetic field sensors/regulators at the interface.

  8. On the Equipartition of Kinetic Energy in an Ideal Gas Mixture

    ERIC Educational Resources Information Center

    Peliti, L.

    2007-01-01

    A refinement of an argument due to Maxwell for the equipartition of translational kinetic energy in a mixture of ideal gases with different masses is proposed. The argument is elementary, yet it may work as an illustration of the role of symmetry and independence postulates in kinetic theory. (Contains 1 figure.)

  9. The Role of Multiple Representations in the Understanding of Ideal Gas Problems

    ERIC Educational Resources Information Center

    Madden, Sean P.; Jones, Loretta L.; Rahm, Jrene

    2011-01-01

    This study examined the representational competence of students as they solved problems dealing with the temperature-pressure relationship for ideal gases. Seven students enrolled in a first-semester general chemistry course and two advanced undergraduate science majors participated in the study. The written work and transcripts from videotaped…

  10. The Role of Multiple Representations in the Understanding of Ideal Gas Problems

    ERIC Educational Resources Information Center

    Madden, Sean P.; Jones, Loretta L.; Rahm, Jrene

    2011-01-01

    This study examined the representational competence of students as they solved problems dealing with the temperature-pressure relationship for ideal gases. Seven students enrolled in a first-semester general chemistry course and two advanced undergraduate science majors participated in the study. The written work and transcripts from videotaped…

  11. On the Equipartition of Kinetic Energy in an Ideal Gas Mixture

    ERIC Educational Resources Information Center

    Peliti, L.

    2007-01-01

    A refinement of an argument due to Maxwell for the equipartition of translational kinetic energy in a mixture of ideal gases with different masses is proposed. The argument is elementary, yet it may work as an illustration of the role of symmetry and independence postulates in kinetic theory. (Contains 1 figure.)

  12. Zero-order crystallization in the Bethe-Fermi homework and electron gas problems

    NASA Astrophysics Data System (ADS)

    Cambiaggio, M. C.; De Llano, M.; Plastino, A.; Szybisz, L.; Ramírez, S.

    1980-04-01

    Single-determinantal states consisting of localized, non-overlapping single-particle orbitals are used in comparison with those made up of plane wave ones to show that neutron matter prefers a "crystalline" configuration beyond a density of around 0.07 fm -3 for the ν0 homework potential. The total energy is not too high above the best Jastrow-correlated calculations. No such effect is found for the ν1 homework potential. The analogous question for the electron gas is also studied.

  13. Off-diagonal long-range order, cycle probabilities, and condensate fraction in the ideal Bose gas.

    PubMed

    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.

  14. Triplet pair amplitude in a trapped s -wave superfluid Fermi gas with broken spin rotation symmetry. II. Three-dimensional continuum case

    NASA Astrophysics Data System (ADS)

    Inotani, Daisuke; Hanai, Ryo; Ohashi, Yoji

    2016-10-01

    We extend our recent work [Y. Endo et al., Phys. Rev. A 92, 023610 (2015)], 10.1103/PhysRevA.92.023610 for a parity-mixing effect in a model of two-dimensional lattice fermions to a realistic three-dimensional ultracold Fermi gas. Including effects of broken local spatial inversion symmetry by a trap potential within the framework of the real-space Bogoliubov-de Gennes theory at T =0 , we point out that an odd-parity p -wave Cooper-pair amplitude is expected to have already been realized in previous experiments on an (even-parity) s -wave superfluid Fermi gas with spin imbalance. This indicates that when one suddenly changes the s -wave pairing interaction to an appropriate p -wave one by using a Feshbach technique in this case, a nonvanishing p -wave superfluid order parameter is immediately obtained, which is given by the product of the p -wave interaction and the p -wave pair amplitude that has already been induced in the spin-imbalanced s -wave superfluid Fermi gas. Thus, by definition, the system is in the p -wave superfluid state, at least just after this manipulation. Since the achievement of a p -wave superfluid state is one of the most exciting challenges in cold Fermi gas physics, our results may provide an alternative approach to this unconventional pairing state. In addition, since the parity-mixing effect cannot be explained as far as one deals with a trap potential in the local density approximation (LDA), it is considered as a crucial example which requires us to go beyond the LDA.

  15. 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.

  16. Specific Heat and Effects of Uniaxial Anisotropy of a p-Wave Pairing Interaction in a Strongly Interacting Ultracold Fermi Gas

    NASA Astrophysics Data System (ADS)

    Inotani, Daisuke; van Wyk, Pieter; Ohashi, Yoji

    2017-04-01

    We investigate the specific heat CV at constant volume and effects of uniaxial anisotropy of a p-wave attractive interaction in the normal state of an ultracold Fermi gas. Within the framework of the strong-coupling theory developed by Nozières and Schmitt-Rink, we evaluate this thermodynamic quantity as a function of temperature, in the whole interaction regime. While the uniaxial anisotropy is not crucial for CV in the weak-coupling regime, CV is found to be sensitive to the uniaxial anisotropy in the strong-coupling regime. This originates from the population imbalance among pi-wave molecules (i = x,y,z), indicating that the specific heat is a useful observable to see which kinds of p-wave molecules dominantly exist in the strong-coupling regime when the p-wave interaction has uniaxial anisotropy. Using this strong point, we classify the strong-coupling regime into some characteristic regions. Since a p-wave pairing interaction with uniaxial anisotropy has been discovered in a 40K Fermi gas, our results would be useful in considering strong-coupling properties of a p-wave interacting Fermi gas, when the interaction is uniaxially anisotropic.

  17. Planck intermediate results. XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck

    NASA Astrophysics Data System (ADS)

    Planck Collaboration; Fermi Collaboration; Ade, P. A. R.; Aghanim, N.; Aniano, G.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J.-F.; Casandjian, J. M.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Digel, S. W.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Fukui, Y.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Grenier, I. A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Natoli, P.; Nørgaard-Nielsen, H. U.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ristorcelli, I.; Rocha, G.; Roudier, G.; Rusholme, B.; Sandri, M.; Santos, D.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Strong, A. W.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Terenzi, L.; Tibaldo, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

    2015-10-01

    The nearby Chamaeleon clouds have been observed in γ rays by the Fermi Large Area Telescope (LAT) and in thermal dust emission by Planck and IRAS. Cosmic rays and large dust grains, if smoothly mixed with gas, can jointly serve with the H i and 12CO radio data to (i) map the hydrogen column densities, NH, in the different gas phases, in particular at the dark neutral medium (DNM) transition between the H i-bright and CO-bright media; (ii) constrain the CO-to-H2 conversion factor, XCO; and (iii) probe the dust properties per gas nucleon in each phase and map their spatial variations across the clouds. We have separated clouds at local, intermediate, and Galactic velocities in H i and 12CO line emission to model in parallel the γ-ray intensity recorded between 0.4 and 100 GeV; the dust optical depth at 353 GHz, τ353; the thermal radiance of the large grains; and an estimate of the dust extinction, AVQ, empirically corrected for the starlight intensity. The dust and γ-ray models have been coupled to account for the DNM gas. The consistent γ-ray emissivity spectra recorded in the different phases confirm that the GeV-TeV cosmic rays probed by the LAT uniformly permeate all gas phases up to the 12CO cores. The dust and cosmic rays both reveal large amounts of DNM gas, with comparable spatial distributions and twice as much mass as in the CO-bright clouds. We give constraints on the H i-DNM-CO transitions for five separate clouds. CO-dark H2 dominates the molecular columns up to AV ≃ 0.9 and its mass often exceeds the one-third of the molecular mass expected by theory. The corrected AVQ extinction largely provides the best fit to the total gas traced by the γ rays. Nevertheless, we find evidence for a marked rise in AVQ/NH with increasing NH and molecular fraction, and with decreasing dust temperature. The rise in τ353/NH is even steeper. We observe variations of lesser amplitude and orderliness for the specific power of the grains, except for a coherent decline

  18. Planck intermediate results: XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck $$\\star$$

    DOE PAGES

    Ade, P. A. R.; Aghanim, N.; Aniano, G.; ...

    2015-09-30

    The nearby Chamaeleon clouds have been observed in γ rays by the Fermi Large Area Telescope (LAT) and in thermal dust emission by Planck and IRAS. Cosmic rays and large dust grains, if smoothly mixed with gas, can jointly serve with the H i and 12CO radio data to (i) map the hydrogen column densities, NH, in the different gas phases, in particular at the dark neutral medium (DNM) transition between the H i-bright and CO-bright media; (ii) constrain the CO-to-H2 conversion factor, XCO; and (iii) probe the dust properties per gas nucleon in each phase and map their spatialmore » variations across the clouds. We have separated clouds at local, intermediate, and Galactic velocities in H i and 12CO line emission to model in parallel the γ-ray intensity recorded between 0.4 and 100 GeV; the dust optical depth at 353 GHz, τ353; the thermal radiance of the large grains; and an estimate of the dust extinction, AVQ, empirically corrected for the starlight intensity. Furthermore, the dust and γ-ray models have been coupled to account for the DNM gas. The consistent γ-ray emissivity spectra recorded in the different phases confirm that the GeV–TeV cosmic rays probed by the LAT uniformly permeate all gas phases up to the 12CO cores. The dust and cosmic rays both reveal large amounts of DNM gas, with comparable spatial distributions and twice as much mass as in the CO-bright clouds. We give constraints on the Hi-DNM-CO transitions for five separate clouds. CO-dark H2 dominates the molecular columns up to AV ≃ 0.9 and its mass often exceeds the one-third of the molecular mass expected by theory. The corrected AVQ extinction largely provides the best fit to the total gas traced by the γ rays. Nevertheless, we find evidence for a marked rise in AVQ/NH with increasing NH and molecular fraction, and with decreasing dust temperature. The rise in τ353/NH is even steeper. Here, we observe variations of lesser amplitude and orderliness for the specific power of the grains

  19. Effect of three-body loss on itinerant ferromagnetism in an atomic Fermi gas

    SciTech Connect

    Conduit, G. J.; Altman, E.

    2011-04-15

    A recent experiment has provided tentative evidence for itinerant ferromagnetism in an ultracold atomic gas. However, the interpretation of the results is complicated by significant atom losses. We argue that during the loss process the system gradually heats up but remains in local equilibrium.To quantify the consequences of atom loss on the putative ferromagnetic transition we adopt an extended Hertz-Millis theory. The losses damp quantum fluctuations, thus increasing the critical interaction strength needed to induce ferromagnetism and revert the transition from being first order to second order. This effect may resolve a discrepancy between the experiment and previous theoretical predictions. We further illuminate the impact of loss by studying the collective spin excitations in the ferromagnet. Even in the fully polarized state, where loss is completely suppressed, spin waves acquire a decay rate proportional to the three-body loss coefficient.

  20. 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.

  1. Measuring the Speed of Sound in a 1D Fermi Gas

    NASA Astrophysics Data System (ADS)

    Fry, Jacob; Revelle, Melissa; Hulet, Randall

    2016-05-01

    We report measurements of the speed of sound in a two-spin component, 1D gas of fermionic lithium. The 1D system is an array of one-dimensional tubes created by a 2D optical lattice. By increasing the lattice depth, the tunneling between tubes is sufficiently small to make each an independent 1D system. To measure the speed of sound, we create a density notch at the center of the atom cloud using a sheet of light tuned far from resonance. The dipole force felt by both spin states will be equivalent, so this notch can be thought of as a charge excitation. Once this beam is turned off, the notch propagates to the edge of the atomic cloud with a velocity that depends on the strength of interatomic interactions. We control interactions using a magnetically tuned Feshbach resonance, allowing us to measure the speed of sound over a wide range of interaction. This method may be used to extract the Luttinger parameter vs. interaction strength. Supported by an ARO MURI Grant, NSF, and The Welch Foundation.

  2. Threshold singularities in a Fermi gas with attractive potential in one dimension

    NASA Astrophysics Data System (ADS)

    Schlottmann, P.; Zvyagin, A. A.

    2015-03-01

    We consider the one-dimensional gas of fermions with spin S interacting via an attractive δ-function potential using the Bethe Ansatz solution. In zero magnetic field the atoms form bound states of N = 2 S + 1 fermions, i.e. generalized Cooper states with each atom having a different spin component. For low energy excitations the system is a Luttinger liquid and is properly described by a conformal field theory with conformal charge c = 1. The linear dispersion of a Luttinger liquid is asymptotically exact in the low-energy limit where the band curvature terms in the dispersion are irrelevant. For higher energy excitations, however, the spectral function displays deviations in the neighborhood of the single-particle (hole) energy, which can be described by an effective X-ray edge type model. Using the Bethe Ansatz solution we obtain expressions for the critical exponents for the single-particle (hole) Green's function. This model can be relevant in the context of ultracold atoms with effective total spin S confined to an elongated optical trap.

  3. Interferograms, schlieren, and shadowgraphs constructed from real- and ideal-gas, two- and three-dimensional computed flowfields

    NASA Technical Reports Server (NTRS)

    Yates, Leslie A.

    1993-01-01

    The construction of interferograms, schlieren, and shadowgraphs from computed flowfield solutions permits one-to-one comparisons of computed and experimental results. A method of constructing these images from both ideal- and real-gas, two and three-dimensional computed flowfields is described. The computational grids can be structured or unstructured, and multiple grids are an option. Constructed images are shown for several types of computed flows including nozzle, wake, and reacting flows; comparisons to experimental images are also shown. In addition, th sensitivity of these images to errors in the flowfield solution is demonstrated, and the constructed images can be used to identify problem areas in the computations.

  4. Interferograms, Schlieren, and Shadowgraphs Constructed from Real- and Ideal-Gas, Two- and Three-Dimensional Computed Flowfields

    NASA Technical Reports Server (NTRS)

    Yates, Leslie A.

    1992-01-01

    The construction of interferograms, schlieren, and shadowgraphs from computed flowfield solutions permits one-to-one comparisons of computed and experimental results. A method for constructing these images from both ideal- and real-gas, two- and three-dimensional computed flowfields is described. The computational grids can be structured or unstructured, and multiple grids are an option. Constructed images are shown for several types of computed flows including nozzle, wake, and reacting flows; comparisons to experimental images are also shown. In addition, the sensitivity of these images to errors in the flowfield solution is demonstrated, and the constructed images can be used to identify problem areas in the computations.

  5. Investigation of Bose Condensation in Ideal Bose Gas Trapped under Generic Power Law Potential in d Dimension

    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.

  6. On ideals and idealization.

    PubMed

    Morrison, Andrew P

    2009-04-01

    This chapter repositions ideals away from their role as defensive structures restraining aggressive and lustful drives (as traditionally viewed) toward their place in shaping creativity and love. We select and mold our particular ideals in providing meaning and in this manner help to create those selfobjects needed to resolve or soothe our needs. This creative process may include "reshaping" of the available object to represent the "idealized other." From this perspective, Kohut's view of idealization and the idealized parental imago will be considered, including my own notion of a one-and-a-half person psychology. Our ideals inevitably conflict and clash, leading to internal self-conflicts that generate what I call the dialectic of narcissism. Narcissism is here considered broadly, reflecting all attributes of self-experience. Shame plays an important role in this dialectic, relating to failure with regard to ideals and to falling short of cherished goals. Ultimately, it is the shaping of, and approximation to, flexible and meaningful ideals that comprise that lofty, ineffable, human ideal--wisdom. Clinical vignettes will be offered to illustrate these themes.

  7. Inflation of the early cold Universe filled with a nonlinear scalar field and a nonideal relativistic Fermi gas

    NASA Astrophysics Data System (ADS)

    Pashitskii, E. A.; Pentegov, V. I.

    2017-03-01

    We consider a possible scenario for the evolution of the early cold Universe born from a fairly large quantum fluctuation in a vacuum with a size a 0 ≫ l P (where l P is the Planck length) and filled with both a nonlinear scalar field φ, whose potential energy density U(φ) determines the vacuum energy density λ, and a nonideal Fermi gas with short-range repulsion between particles, whose equation of state is characterized by the ratio of pressure P( n F ) to energy density ɛ( n F ) dependent on the number density of fermions n F . As the early Universe expands, the dimensionless quantity ν( n F ) = P( n F )/ɛ( n F ) decreases with decreasing n F from its maximum value νmax = 1 for n F → ∞ to zero for n F → 0. The interaction of the scalar and gravitational fields, which is characterized by a dimensionless constant ξ, is proportional to the scalar curvature of four-dimensional space R = κ[3 P( n F )-ɛ( n F )-4λ] (where κ is Einstein's gravitational constant), and contains terms both quadratic and linear in φ. As a result, the expanding early Universe reaches the point of first-order phase transition in a finite time interval at critical values of the scalar curvature R = R c =-μ2/ξ and radius a c ≫ a 0. Thereafter, the early closed Universe "rolls down" from the flat inflection point of the potential U(φ) to the zero potential minimum in a finite time. The release of the total potential energy of the scalar field in the entire volume of the expanding Universe as it "rolls down" must be accompanied by the production of a large number of massive particles and antiparticles of various kinds, whose annihilation plays the role of the Big Bang. We also discuss the fundamental nature of Newton' gravitational constant G N .

  8. Propagation of a cylindrical shock wave in a mixture of a non-ideal gas and small solid particles under the action of monochromatic radiation

    NASA Astrophysics Data System (ADS)

    Sahu, Praveen Kumar; Nath, Gorakh

    2016-07-01

    Cylindrical shock wave in a dusty gas is discussed under the action of monochromatic radiation into stellar atmosphere with a constant intensity on unit area. The gas is assumed to be grey and opaque and shock to be transparent. The dusty gas is assumed to be a mixture of non-ideal gas and small solid particles. To obtain some essential features of the shock propagation, small solid particles are taken as pseudo-fluid and it is assumed that the equilibrium flow condition is maintained in the flow-field. The effects of variation of the parameters of the non-idealness of the gas, the mass concentration of solid particles in the mixture, the ratio of the density of solid particles to the initial density of the gas and the radiation parameter are investigated. It is shown that an increase in the parameters of the non-idealness of the gas and the radiation parameter have decaying effect on the shock waves; whereas with an increase in the ratio of the density of solid particles to the initial density of the gas the shock strength increases. It is found that an increase in the parameter non-idealness of the gas and the ratio of the density of solid particles to the initial density of the gas have opposite behaviour on fluid velocity, pressure and shock strength. Also, it is shown that an increase in the radiation parameter has effect to decrease the flow variables and the shock strength.

  9. Simulation of ideal-gas flow by nitrogen and other selected gases at cryogenic temperatures. [transonic flow in cryogenic wind tunnels

    NASA Technical Reports Server (NTRS)

    Hall, R. M.; Adcock, J. B.

    1981-01-01

    The real gas behavior of nitrogen, the gas normally used in transonic cryogenic tunnels, is reported for the following flow processes: isentropic expansion, normal shocks, boundary layers, and interactions between shock waves and boundary layers. The only difference in predicted pressure ratio between nitrogen and an ideal gas which may limit the minimum operating temperature of transonic cryogenic wind tunnels occur at total pressures approaching 9 atm and total temperatures 10 K below the corresponding saturation temperature. These pressure differences approach 1 percent for both isentropic expansions and normal shocks. Alternative cryogenic test gases were also analyzed. Differences between air and an ideal diatomic gas are similar in magnitude to those for nitrogen and should present no difficulty. However, differences for helium and hydrogen are over an order of magnitude greater than those for nitrogen or air. It is concluded that helium and cryogenic hydrogen would not approximate the compressible flow of an ideal diatomic gas.

  10. Idealized gas turbine combustor for performance research and validation of large eddy simulations.

    PubMed

    Williams, Timothy C; Schefer, Robert W; Oefelein, Joseph C; Shaddix, Christopher R

    2007-03-01

    This paper details the design of a premixed, swirl-stabilized combustor that was designed and built for the express purpose of obtaining validation-quality data for the development of large eddy simulations (LES) of gas turbine combustors. The combustor features nonambiguous boundary conditions, a geometrically simple design that retains the essential fluid dynamics and thermochemical processes that occur in actual gas turbine combustors, and unrestrictive access for laser and optical diagnostic measurements. After discussing the design detail, a preliminary investigation of the performance and operating envelope of the combustor is presented. With the combustor operating on premixed methane/air, both the equivalence ratio and the inlet velocity were systematically varied and the flame structure was recorded via digital photography. Interesting lean flame blowout and resonance characteristics were observed. In addition, the combustor exhibited a large region of stable, acoustically clean combustion that is suitable for preliminary validation of LES models.

  11. Choking of ideal-gas flow in convergent nozzles and integral nozzle characteristics

    SciTech Connect

    Yagudin, S.V.

    1995-05-01

    The results of a numerical and theoretical investigation of the local and integral characteristics of convergent nozzles are presented. It is shown that self-similar (choked) nozzle flow, when the gas flow rate does not depend on the external pressure, may occur at subcritical values of the pressure ratio {pi}{sub c} this nozzle will have a higher thrust coefficient than the initial conical nozzle.

  12. The ideal oxygen/nitrous oxide fresh gas flow sequence with the Anesthesia Delivery Unit machine.

    PubMed

    Hendrickx, Jan F A; Cardinael, Sara; Carette, Rik; Lemmens, Hendrikus J M; De Wolf, Andre M

    2007-06-01

    To determine whether early reduction of oxygen and nitrous oxide fresh gas flow from 6 L/min to 0.7 L/min could be accomplished while maintaining end-expired nitrous oxide concentration > or =50% with an Anesthesia Delivery Unit anesthesia machine. Prospective, randomized clinical study. Large teaching hospital in Belgium. 53 ASA physical status I and II patients requiring general endotracheal anesthesia and controlled mechanical ventilation. Patients were randomly assigned to one of 4 groups depending on the duration of high oxygen/nitrous oxide fresh gas flow (two and 4 L/min, respectively) before lowering total fresh gas flow to 0.7 L/min (0.3 and 0.4 L/min oxygen and nitrous oxide, respectively): one, two, three, or 5 minutes (1-minute group, 2-minute group, 3-minute group, and 5-minute group), with n = 10, 12, 13, and 8, respectively. The course of the end-expired nitrous oxide concentration and bellows volume deficit at end-expiration was compared among the 4 groups during the first 30 minutes. At the end of the high-flow period the end-expired nitrous oxide concentration was 35.6 +/- 6.2%, 48.4 +/- 4.8%, 53.7 +/- 8.7%, and 57.3 +/- 1.6% in the 4 groups, respectively. Thereafter, the end-expired nitrous oxide concentration decreased to a nadir of 36.1 +/- 4.5%, 45.4 +/- 3.8%, 50.9 +/- 6.1%, and 55.4 +/- 2.8% after three, 4, 6, and 8 minutes after flows were lowered in the 1- to 5-minute groups, respectively. A decrease in bellows volume was observed in most patients, but was most pronounced in the 2-minute group. The bellows volume deficit gradually faded within 15 to 20 minutes in all 4 groups. A 3-minute high-flow period (oxygen and nitrous oxide fresh gas flow of 2 and 4 L/min, respectively) suffices to attain and maintain end-expired nitrous oxide concentration > or =50% and ensures an adequate bellows volume during the ensuing low-flow period.

  13. Multi-gas interaction modeling on decorated semiconductor interfaces: A novel Fermi distribution-based response isotherm and the inverse hard/soft acid/base concept

    NASA Astrophysics Data System (ADS)

    Laminack, William; Gole, James

    2015-12-01

    A unique MEMS/NEMS approach is presented for the modeling of a detection platform for mixed gas interactions. Mixed gas analytes interact with nanostructured decorating metal oxide island sites supported on a microporous silicon substrate. The Inverse Hard/Soft acid/base (IHSAB) concept is used to assess a diversity of conductometric responses for mixed gas interactions as a function of these nanostructured metal oxides. The analyte conductometric responses are well represented using a combination diffusion/absorption-based model for multi-gas interactions where a newly developed response absorption isotherm, based on the Fermi distribution function is applied. A further coupling of this model with the IHSAB concept describes the considerations in modeling of multi-gas mixed analyte-interface, and analyte-analyte interactions. Taking into account the molecular electronic interaction of both the analytes with each other and an extrinsic semiconductor interface we demonstrate how the presence of one gas can enhance or diminish the reversible interaction of a second gas with the extrinsic semiconductor interface. These concepts demonstrate important considerations in the array-based formats for multi-gas sensing and its applications.

  14. Ideal gas solubilities and solubility selectivities in a binary mixture of room-temperature ionic liquids

    SciTech Connect

    Finotello Alexia; Bara Jason E.; Narayan Suguna; Campder Dean; Noble Richard D.

    2008-07-01

    This study focuses on the solubility behaviors of CO{sub 2}, CH{sub 4}, and N{sub 2} gases in binary mixtures of imidazolium-based room-temperature ionic liquids (RTILs) using l-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide ((C{sub 2}mim)(Tf{sub 2}N)) and l-ethyl-3-methylimidazolium tetrafluoroborate ((C{sub 2}mim)(BF{sub 4})) at 40{sup o}C and low pressures (about 1 atm). The mixtures tested were 0, 25, 50, 75, 90, 95, and 100 mol % (C{sub 2}mim)(BF{sub 4}) in (C{sub 2}-mim)(Tf2{sub N}). Results show that regular solution theory (RST) can be used to describe the gas solubility and selectivity behaviors in RTIL mixtures using an average mixture solubility parameter or an average measured mixture molar volume. Interestingly, the solubility selectivity, defined as the ratio of gas mole fractions in the RTIL mixture, of CO{sub 2} with N{sub 2} or CH{sub 4} in pure (C{sub 2}mim)(BF4) can be enhanced by adding 5 mol% (C{sub 2}-mim)(Tf{sub 2}N).

  15. Ideal quantum gas in an expanding cavity: nature of nonadiabatic force.

    PubMed

    Nakamura, K; Avazbaev, S K; Sobirov, Z A; Matrasulov, D U; Monnai, T

    2011-04-01

    We consider a quantum gas of noninteracting particles confined in the expanding cavity and investigate the nature of the nonadiabatic force which is generated from the gas and acts on the cavity wall. First, with use of the time-dependent canonical transformation, which transforms the expanding cavity to the nonexpanding one, we can define the force operator. Second, applying the perturbative theory, which works when the cavity wall begins to move at time origin, we find that the nonadiabatic force is quadratic in the wall velocity and thereby does not break the time-reversal symmetry, in contrast with general belief. Finally, using an assembly of the transitionless quantum states, we obtain the nonadiabatic force exactly. The exact result justifies the validity of both the definition of the force operator and the issue of the perturbative theory. The mysterious mechanism of nonadiabatic transition with the use of transitionless quantum states is also explained. The study is done for both cases of the hard- and soft-wall confinement with the time-dependent confining length. ©2011 American Physical Society

  16. Ideal gas solubilities and solubility selectivities in a binary mixture of room-temperature ionic liquids.

    PubMed

    Finotello, Alexia; Bara, Jason E; Narayan, Suguna; Camper, Dean; Noble, Richard D

    2008-02-28

    This study focuses on the solubility behaviors of CO2, CH4, and N2 gases in binary mixtures of imidazolium-based room-temperature ionic liquids (RTILs) using 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2mim][Tf2N]) and 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]) at 40 degrees C and low pressures (approximately 1 atm). The mixtures tested were 0, 25, 50, 75, 90, 95, and 100 mol % [C2mim][BF4] in [C2mim][Tf2N]. Results show that regular solution theory (RST) can be used to describe the gas solubility and selectivity behaviors in RTIL mixtures using an average mixture solubility parameter or an average measured mixture molar volume. Interestingly, the solubility selectivity, defined as the ratio of gas mole fractions in the RTIL mixture, of CO2 with N2 or CH4 in pure [C2mim][BF4] can be enhanced by adding 5 mol % [C2mim][Tf2N].

  17. Steady Secondary Flows Generated by Periodic Compression and Expansion of an Ideal Gas in a Pulse Tube

    NASA Technical Reports Server (NTRS)

    Lee, Jeffrey M.

    1999-01-01

    This study establishes a consistent set of differential equations for use in describing the steady secondary flows generated by periodic compression and expansion of an ideal gas in pulse tubes. Also considered is heat transfer between the gas and the tube wall of finite thickness. A small-amplitude series expansion solution in the inverse Strouhal number is proposed for the two-dimensional axisymmetric mass, momentum and energy equations. The anelastic approach applies when shock and acoustic energies are small compared with the energy needed to compress and expand the gas. An analytic solution to the ordered series is obtained in the strong temperature limit where the zeroth-order temperature is constant. The solution shows steady velocities increase linearly for small Valensi number and can be of order I for large Valensi number. A conversion of steady work flow to heat flow occurs whenever temperature, velocity or phase angle gradients are present. Steady enthalpy flow is reduced by heat transfer and is scaled by the Prandtl times Valensi numbers. Particle velocities from a smoke-wire experiment were compared with predictions for the basic and orifice pulse tube configurations. The theory accurately predicted the observed steady streaming.

  18. Thermodynamics and kinetics of binary nucleation in ideal-gas mixtures.

    PubMed

    Alekseechkin, Nikolay V

    2015-08-07

    The nonisothermal single-component theory of droplet nucleation [N. V. Alekseechkin, Physica A 412, 186 (2014)] is extended to binary case; the droplet volume V, composition x, and temperature T are the variables of the theory. An approach based on macroscopic kinetics (in contrast to the standard microscopic model of nucleation operating with the probabilities of monomer attachment and detachment) is developed for the droplet evolution and results in the derived droplet motion equations in the space (V, x, T)—equations for V̇≡dV/dt, ẋ, and Ṫ. The work W(V, x, T) of the droplet formation is obtained in the vicinity of the saddle point as a quadratic form with diagonal matrix. Also, the problem of generalizing the single-component Kelvin equation for the equilibrium vapor pressure to binary case is solved; it is presented here as a problem of integrability of a Pfaffian equation. The equation for Ṫ is shown to be the first law of thermodynamics for the droplet, which is a consequence of Onsager's reciprocal relations and the linked-fluxes concept. As an example of ideal solution for demonstrative numerical calculations, the o-xylene-m-xylene system is employed. Both nonisothermal and enrichment effects are shown to exist; the mean steady-state overheat of droplets and their mean steady-state enrichment are calculated with the help of the 3D distribution function. Some qualitative peculiarities of the nucleation thermodynamics and kinetics in the water-sulfuric acid system are considered in the model of regular solution. It is shown that there is a small kinetic parameter in the theory due to the small amount of the acid in the vapor and, as a consequence, the nucleation process is isothermal.

  19. Thermodynamics and kinetics of binary nucleation in ideal-gas mixtures

    NASA Astrophysics Data System (ADS)

    Alekseechkin, Nikolay V.

    2015-08-01

    The nonisothermal single-component theory of droplet nucleation [N. V. Alekseechkin, Physica A 412, 186 (2014)] is extended to binary case; the droplet volume V, composition x, and temperature T are the variables of the theory. An approach based on macroscopic kinetics (in contrast to the standard microscopic model of nucleation operating with the probabilities of monomer attachment and detachment) is developed for the droplet evolution and results in the derived droplet motion equations in the space (V, x, T)—equations for V ˙ ≡ d V / d t , x ˙ , and T ˙ . The work W(V, x, T) of the droplet formation is obtained in the vicinity of the saddle point as a quadratic form with diagonal matrix. Also, the problem of generalizing the single-component Kelvin equation for the equilibrium vapor pressure to binary case is solved; it is presented here as a problem of integrability of a Pfaffian equation. The equation for T ˙ is shown to be the first law of thermodynamics for the droplet, which is a consequence of Onsager's reciprocal relations and the linked-fluxes concept. As an example of ideal solution for demonstrative numerical calculations, the o-xylene-m-xylene system is employed. Both nonisothermal and enrichment effects are shown to exist; the mean steady-state overheat of droplets and their mean steady-state enrichment are calculated with the help of the 3D distribution function. Some qualitative peculiarities of the nucleation thermodynamics and kinetics in the water-sulfuric acid system are considered in the model of regular solution. It is shown that there is a small kinetic parameter in the theory due to the small amount of the acid in the vapor and, as a consequence, the nucleation process is isothermal.

  20. Remembering Fermi

    SciTech Connect

    Cronin, James

    2005-03-30

    A combination of the discovery of nuclear fission and the circumstances of the 2nd World War brought Enrico Fermi to Chicago, where he led the team that produced the first controlled, self-sustained nuclear chain reaction. Following the war in 1945 Chancellor Hutchins, William Zachariasen, and Walter Bartky convinced Fermi to accept a professorship at the University of Chicago, where the Institute for Nuclear Studies was established. Fermi served as the leading figure in surely the greatest collection of scientists the world has ever seen. Fermi's tenure at Chicago was cut short by his death in 1954. My talk will concentrate on the years 1945-54. Examples of his research notebooks, his speeches, his teaching, and his correspondence will be discussed.

  1. Magnetic-modulation spectroscopy of an atomic Fermi gas in the BCS-BEC crossover: Dissociation spectra in the Bose-Einstein condensate 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.

  2. Thermodynamics of ideal quantum gas with fractional statistics in D dimensions.

    PubMed

    Potter, Geoffrey G; Müller, Gerhard; Karbach, Michael

    2007-06-01

    We present exact and explicit results for the thermodynamic properties (isochores, isotherms, isobars, response functions, velocity of sound) of a quantum gas in dimensions D > or = 1 and with fractional exclusion statistics 0 < or = g < or =1 connecting bosons (g=0) and fermions (g=1) . In D=1 the results are equivalent to those of the Calogero-Sutherland model. Emphasis is given to the crossover between bosonlike and fermionlike features, caused by aspects of the statistical interaction that mimic long-range attraction and short-range repulsion. A phase transition along the isobar occurs at a nonzero temperature in all dimensions. The T dependence of the velocity of sound is in simple relation to isochores and isobars. The effects of soft container walls are accounted for rigorously for the case of a pure power-law potential.

  3. Unified first principles description from warm dense matter to ideal ionized gas plasma: electron-ion collisions induced friction.

    PubMed

    Dai, Jiayu; Hou, Yong; Yuan, Jianmin

    2010-06-18

    Electron-ion interactions are central to numerous phenomena in the warm dense matter (WDM) regime and at higher temperature. The electron-ion collisions induced friction at high temperature is introduced in the procedure of ab initio molecular dynamics using the Langevin equation based on density functional theory. In this framework, as a test for Fe and H up to 1000 eV, the equation of state and the transition of electronic structures of the materials with very wide density and temperature can be described, which covers a full range of WDM up to high energy density physics. A unified first principles description from condensed matter to ideal ionized gas plasma is constructed.

  4. Ideal-gas specific heat and second virial coefficient of HFC-125 based on sound-velocity measurements

    SciTech Connect

    Hozumi, T.; Sato, H.; Watanabe, K.

    1996-05-01

    The sound velocity in gaseous pentafluoroethane (HFC-125, CF{sub 3}CHF{sub 2}) has been measured by means of a spherical acoustic resonator. Seventy-two sound-velocity values were measured with an uncertainty of {plus_minus}0.01% at temperatures form 273 to 343 K and pressures form 10 to 250 kPa. The ideal-gas specific heats and the second acoustic-virial coefficients have been determined on the basis of the sound-velocity measurements. The second virial coefficients calculated from the present sound-velocity measurements agree with literature values which were determined from PVT measurements by means of a Burnett method.

  5. Entransy analysis and optimization of performance of nano-scale irreversible Otto cycle operating with Maxwell-Boltzmann ideal gas

    NASA Astrophysics Data System (ADS)

    Ahmadi, Mohammad H.; Ahmadi, Mohammad Ali; Pourfayaz, Fathollah; Bidi, Mokhtar

    2016-08-01

    This paper made attempt to investigate thermodynamically a nano scale irreversible Otto cycle for optimizing its performance. This system employed an ideal Maxwell-Boltzmann gas as a working fluid. Two different scenarios were proposed in the multi-objective optimization process and the results of each of the scenarios were examined separately. The first scenario made attempt to maximize the dimensionless ecological function and minimize the dimensionless entransy dissipation of the system. Furthermore, the second scenario tried to maximize the ecological coefficient of performance and minimize the dimensionless entransy dissipation of the system. The multi objective evolutionary method integrated with non-dominated sorting genetic algorithm was used to optimize the proposed objective functions. To determine the final output of each scenario, three efficient decision makers were employed. Finally, error analysis was employed to determine the deviation of solutions chosen by decision makers.

  6. Rigorous investigation of the reduced density matrix for the ideal Bose gas in harmonic traps by a loop-gas-like approach

    SciTech Connect

    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.

  7. Theory versus Practice in the Twentieth-Century Search for the Ideal Anaesthetic Gas.

    PubMed

    Rae, Ian D

    2016-02-01

    At the beginning of the twentieth century, an anaesthetist could choose between nitrous oxide, chloroform, and ether (diethyl ether) for the induction of painrelieving unconsciousness. By the end of century, the choice was between a small number of fluorinated aliphatic ethers such as Enflurane, Desflurane, and Sevoflurane, and (in some jurisdictions) the rare gas, xenon. Between these endpoints researchers had identified a surprisingly broad range of hydrocarbons, noble gases, organohalogens, and aliphatic ethers that possessed anaesthetic properties. None was entirely satisfactory, but clinicians at various times and in various places employed substances in each of these categories. Behind the search for new anaesthetic gases was a theory of action (Meyer- Overton theory) that was known to be inadequate, but as no alternative was strong enough to displace it the search continued on purely empirical grounds, while lip-service was paid to the theory. By the time a theory couched in more modern terms was proposed, a suite of modern anaesthetic gases was in place, and there have been no attempts to use that theory to drive a new search.

  8. Gas-particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology.

    PubMed

    Shiraiwa, Manabu; Zuend, Andreas; Bertram, Allan K; Seinfeld, John H

    2013-07-21

    Atmospheric aerosols, comprising organic compounds and inorganic salts, play a key role in air quality and climate. Mounting evidence exists that these particles frequently exhibit phase separation into predominantly organic and aqueous electrolyte-rich phases. As well, the presence of amorphous semi-solid or glassy particle phases has been established. Using the canonical system of ammonium sulfate mixed with organics from the ozone oxidation of α-pinene, we illustrate theoretically the interplay of physical state, non-ideality, and particle morphology affecting aerosol mass concentration and the characteristic timescale of gas-particle mass transfer. Phase separation can significantly affect overall particle mass and chemical composition. Semi-solid or glassy phases can kinetically inhibit the partitioning of semivolatile components and hygroscopic growth, in contrast to the traditional assumption that organic compounds exist in quasi-instantaneous gas-particle equilibrium. These effects have significant implications for the interpretation of laboratory data and the development of improved atmospheric air quality and climate models.

  9. Rashbon Bound States Associated with a Spherical Spin-Orbit Coupling in an Ultracold Fermi Gas with an s-Wave Interaction

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Inotani, D.; Ohashi, Y.

    2016-05-01

    We investigate the formation of rashbon bound states and strong-coupling effects in an ultracold Fermi gas with a spherical spin-orbit interaction, H_so=λ {\\varvec{p}}\\cdot {σ } (where {σ }=(σ _x,σ _y,σ _z) are Pauli matrices). Extending the strong-coupling theory developed by Nozières and Schmitt-Rink (NSR) to include this spin-orbit coupling, we determine the superfluid phase transition temperature T_c, as functions of the strength of a pairing interaction U_s, as well as the spin-orbit coupling strength λ . Evaluating poles of the NSR particle-particle scattering matrix describing fluctuations in the Cooper channel, we clarify the region where rashbon bound states dominate the superfluid phase transition in the U_s-λ phase diagram. Since the antisymmetric spin-orbit interaction H_so breaks the inversion symmetry of the system, rashbon bound states naturally have not only a spin-singlet and even-parity symmetry, but also a spin-triplet and odd-parity symmetry. Thus, our results would be also useful for the study of this parity-mixing effect in the BCS-BEC crossover regime of a spin-orbit coupled Fermi gas.

  10. Thermal contribution to thermodynamic functions in the Thomas-Fermi model

    NASA Astrophysics Data System (ADS)

    Shemyakin, O. P.; Levashov, P. R.; Obruchkova, L. R.; Khishchenko, K. V.

    2010-08-01

    We propose a method of calculation of thermodynamic functions in the Thomas-Fermi model at finite temperature θ. Expressions for first and second derivatives of the free energy are analytically obtained in the framework of the model. A special treatment of thermodynamic functions at low temperatures is provided by asymptotic series expansion at θ → 0. A special algorithm is used to ensure required accuracy for all values in a wide range of volumes and temperatures. We compare the results of our computations with ideal Boltzmann and Fermi gas models.

  11. Ultrafast and Ultrasensitive Gas Sensors Derived from a Large Fermi-Level Shift in the Schottky Junction with Sieve-Layer Modulation.

    PubMed

    Cheng, Ching-Cheng; Wu, Chia-Lin; Liao, Yu-Ming; Chen, Yang-Fang

    2016-07-13

    Gas sensors play an important role in numerous fields, covering a wide range of applications, including intelligent systems and detection of harmful and toxic gases. Even though they have attracted much attention, the response time on the order of seconds to minutes is still very slow. To circumvent the existing problems, here, we provide a seminal attempt with the integration of graphene, semiconductor, and an addition sieve layer forming a nanocomposite gas sensor with ultrahigh sensitivity and ultrafast response. The designed sieve layer has a suitable band structure that can serve as a blocking layer to prevent transfer of the charges induced by adsorbed gas molecules into the underlying semiconductor layer. We found that the sensitivity can be reduced to the parts per million level, and the ultrafast response of around 60 ms is unprecedented compared with published graphene-based gas sensors. The achieved high performance can be interpreted well by the large change of the Fermi level of graphene due to its inherent nature of the low density of states and blocking of the sieve layer to prevent charge transfer from graphene to the underlying semiconductor layer. Accordingly, our work is very useful and timely for the development of gas sensors with high performance for practical applications.

  12. DIPPER project 871 determination of ideal-gas enthalpies of formation for key compounds, The 1991 project results

    SciTech Connect

    Steele, W.V.; Chirico, R.D.; Knipmeyer, S.E.; Nguyen, A.; Tasker, I.R.

    1993-09-01

    Results of a study aimed at improving group-contribution methodology for estimating thermodynamic properties of organic substances are reported. Specific weaknesses where particular group-contribution terms were unknown, or estimated because of lack of experimental data, are addressed by experimental studies of enthalpies of combustion in condensed phase, vapor-pressure measurements, and differential scanning calorimetric (d.s.c.) heat-capacity measurements. Ideal-gas enthalpies of formation of cyclohexene, phthalan (2,5-dihydrobenzo-3,4-furan), isoxazole, n-octylamine, di-n-octylamine, tri-n-octylamine, phenyl isocyanate, and 1,4,5,6-tetrahydropyrimidine are reported. Two-phase (liquid + vapor) heat capacities were determined for phthalan, isoxazole, the three octylamines, and phenyl isocyanate. Liquid-phase densities along the saturation line were measured for phthalan and isoxazole at 298 to 425 K. The critical temperature and critical density of n-octylamine were determined from d.s.c. results and critical pressure derived from the fitting procedures. Fitting procedures were used to derive critical temperatures, pressures, and densities for cyclohexene (pressure and density only), phthalan, isoxazole, di-n-octylamine, and phenyl isocyanate. Group-additivity parameters or ring-correction terms are derived.

  13. Condensation of N bosons. II. Nonequilibrium analysis of an ideal Bose gas and the laser phase-transition analogy

    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.

  14. Exploring the Ideal Gas Law through a Quantitative Gasometric Analysis of Nitrogen Produced by the Reaction of Sodium Nitrite with Sulfamic Acid

    ERIC Educational Resources Information Center

    Yu, Anne

    2010-01-01

    The gasometric analysis of nitrogen produced in a reaction between sodium nitrite, NaNO[superscript 2], and sulfamic acid, H(NH[superscript 2])SO[superscript 3], provides an alternative to more common general chemistry experiments used to study the ideal gas law, such as the experiment in which magnesium is reacted with hydrochloric acid. This…

  15. Exploring the Ideal Gas Law through a Quantitative Gasometric Analysis of Nitrogen Produced by the Reaction of Sodium Nitrite with Sulfamic Acid

    ERIC Educational Resources Information Center

    Yu, Anne

    2010-01-01

    The gasometric analysis of nitrogen produced in a reaction between sodium nitrite, NaNO[superscript 2], and sulfamic acid, H(NH[superscript 2])SO[superscript 3], provides an alternative to more common general chemistry experiments used to study the ideal gas law, such as the experiment in which magnesium is reacted with hydrochloric acid. This…

  16. Cooper pairs with zero center-of-mass momentum and their first-order correlation function in a two-dimensional ultracold Fermi gas near a Berezinskii-Kosterlitz-Thouless transition

    NASA Astrophysics Data System (ADS)

    Matsumoto, Morio; Inotani, Daisuke; Ohashi, Yoji

    2016-01-01

    We investigate the center-of-mass momentum distribution nQ of Cooper pairs and their first-order correlation function g1(r ) in a strongly interacting two-dimensional Fermi gas. Recently, the Berezinskii-Kosterlitz-Thouless (BKT) transition was reported in a two-dimensional 6Li Fermi gas, based on (1) the observations of anomalous enhancement of nQ =0 [Ries et al., Phys. Rev. Lett. 114, 230401 (2015), 10.1103/PhysRevLett.114.230401] , as well as (2) a power-law behavior of g1(r ) [Murthy et al., Phys. Rev. Lett. 115, 010401 (2015), 10.1103/PhysRevLett.115.010401]. However, including pairing fluctuations within a T -matrix approximation (TMA), we show that these results can still be explained as strong-coupling properties of a normal-state two-dimensional Fermi gas. Our results indicate the importance of further experimental observations, to definitely confirm the realization of the BKT transition in this system. Since the BKT transition has been realized in a two-dimensional ultracold Bose gas, our results would be useful for the achievement of this quasi-long-range order in an ultracold Fermi gas.

  17. Quantum dynamics of impurities coupled to a Fermi sea

    NASA Astrophysics Data System (ADS)

    Parish, Meera M.; Levinsen, Jesper

    2016-11-01

    We consider the dynamics of an impurity atom immersed in an ideal Fermi gas at zero temperature. We focus on the coherent quantum evolution of the impurity following a quench to strong impurity-fermion interactions, where the interactions are assumed to be short range like in cold-atom experiments. To approximately model the many-body time evolution, we use a truncated basis method, where at most two particle-hole excitations of the Fermi sea are included. When the system is initially noninteracting, we show that our method exactly captures the short-time dynamics following the quench, and we find that the overlap between initial and final states displays a universal nonanalytic dependence on time in this limit. We further demonstrate how our method can be used to compute the impurity spectral function, as well as describe many-body phenomena involving coupled impurity spin states, such as Rabi oscillations in a medium or highly engineered quantum quenches.

  18. Magnetogasdynamics shock waves in a rotational axisymmetric non-ideal gas with increasing energy and conductive and radiative heat-fluxes

    NASA Astrophysics Data System (ADS)

    Nath, Gorakh

    2016-07-01

    Self-similar solutions are obtained for one-dimensional adiabatic flow behind a magnetogasdynamics cylindrical shock wave propagating in a rotational axisymmetric non ideal gas with increasing energy and conductive and radiative heat fluxes in presence of an azimuthal magnetic field. The fluid velocities and the azimuthal magnetic field in the ambient medium are assume to be varying and obeying power laws. In order to find the similarity solutions the angular velocity of the ambient medium is taken to be decreasing as the distance from the axis increases. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be the diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density. The effects of the presence of radiation and conduction, the non-idealness of the gas and the magnetic field on the shock propagation and the flow behind the shock are investigated.

  19. Similarity solution for the flow behind a shock wave in a non-ideal gas with heat conduction and radiation heat-flux in magnetogasdynamics

    NASA Astrophysics Data System (ADS)

    Nath, G.; Vishwakarma, J. P.

    2014-05-01

    The propagation of a spherical (or cylindrical) shock wave in a non-ideal gas with heat conduction and radiation heat-flux, in the presence of a spacially decreasing azimuthal magnetic field, driven out by a moving piston is investigated. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient αR are assumed to vary with temperature and density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Similarity solutions are obtained for the flow-field behind the shock and the effects of variation of the heat transfer parameters, the parameter of the non-idealness of the gas, both, decreases the compressibility of the gas and hence there is a decrease in the shock strength. Further, it is investigated that with an increase in the parameters of radiative and conductive heat transfer the tendency of formation of maxima in the distributions of heat flux, density and isothermal speed of sound decreases. The pressure and density vanish at the inner surface (piston) and hence a vacuum is form at the center of symmetry. The shock waves in conducting non-ideal gas with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of central part of star burst galaxies, nuclear explosion, chemical detonation, rupture of a pressurized vessels, in the analysis of data from exploding wire experiments, and cylindrically symmetric hypersonic flow problems associated with meteors or reentry vehicles, etc. The findings of the present works provided a clear picture of whether and how the non-idealness parameter, conductive and radiative heat transfer parameters and the magnetic field affect the flow behind the shock

  20. Pressure profiles of nonuniform two-dimensional atomic Fermi gases

    NASA Astrophysics Data System (ADS)

    Martiyanov, Kirill; Barmashova, Tatiana; Makhalov, Vasiliy; Turlapov, Andrey

    2016-06-01

    Spatial profiles of the pressure have been measured in atomic Fermi gases with primarily two-dimensional (2D) kinematics. The in-plane motion of the particles is confined by a Gaussian-shape potential. The two-component deeply degenerate Fermi gases are prepared at different values of the s -wave attraction. The pressure profile is found using the force-balance equation, from the measured density profile and the trapping potential. The pressure is compared to zero-temperature models within the local density approximation. In the weakly interacting regime, the pressure lies above a Landau Fermi-liquid theory and below the ideal-Fermi-gas model, whose prediction coincides with that of the Cooper-pair mean-field theory. The values closest to the data are provided by the approach where the mean field of Cooper pairs is supplemented with fluctuations. In the regime of strong interactions, in response to the increasing attraction, the pressure shifts below this model reaching lower values calculated within Monte Carlo methods. Comparison to models shows that interaction-induced departure from 2D kinematics is either small or absent. In particular, comparison with a lattice Monte Carlo suggests that kinematics is two dimensional in the strongly interacting regime.

  1. Level density of a Fermi gas and integer partitions: A Gumbel-like finite-size correction

    SciTech Connect

    Roccia, Jerome; Leboeuf, Patricio

    2010-04-15

    We investigate the many-body level density of a gas of noninteracting fermions. We determine its behavior as a function of the temperature and the number of particles. As the temperature increases, and beyond the usual Sommerfeld expansion that describes the degenerate gas behavior, corrections due to a finite number of particles lead to Gumbel-like contributions. We discuss connections with the partition problem in number theory, extreme value statistics, and differences with respect to the Bose gas.

  2. Enrico Fermi

    NASA Astrophysics Data System (ADS)

    Yang, Chen Ning

    2013-05-01

    Enrico Fermi was, of all the great physicists of the 20th century, among the most respected and admired. He was respected and admired because of his contributions to both theoretical and experimental physics, because of his leadership in discovering for mankind a powerful new source of energy, and above all, because of his personal character. He was always reliable and trustworthy. He had both of his feet on the ground all the time. He had great strength, but never threw his weight around. He did not play to the gallery. He did not practise one-up-manship. He exemplified, I always believe, the perfect Confucian gentleman...

  3. Unconventional pairings of spin-orbit coupled attractive degenerate Fermi gas in a one-dimensional optical lattice

    PubMed Central

    Liang, Junjun; Zhou, Xiaofan; Chui, Pak Hong; Zhang, Kuang; Gu, Shi-jian; Gong, Ming; Chen, Gang; Jia, Suotang

    2015-01-01

    Understanding novel pairings in attractive degenerate Fermi gases is crucial for exploring rich superfluid physics. In this report, we reveal unconventional pairings induced by spin-orbit coupling (SOC) in a one-dimensional optical lattice, using a state-of-the-art density-matrix renormalization group method. When both bands are partially occupied, we find a strong competition between the interband Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) and intraband Bardeen-Cooper-Schrieffer (BCS) pairings. In particular, for the weak and moderate SOC strengths, these two pairings can coexist, giving rise to a new phase called the FFLO-BCS phase, which exhibits a unique three-peak structure in pairing momentum distribution. For the strong SOC strength, the intraband BCS pairing always dominates in the whole parameter regime, including the half filling. We figure out the whole phase diagrams as functions of filling factor, SOC strength, and Zeeman field. Our results are qualitatively different from recent mean-field predictions. Finally, we address that our predictions could be observed in a weaker trapped potential. PMID:26443006

  4. Evolution of the vortex state in the BCS-BEC crossover of a quasi two-dimensional superfluid Fermi gas

    NASA Astrophysics Data System (ADS)

    Luo, Xuebing; Zhou, Kezhao; Zhang, Zhidong

    2016-11-01

    We use the path-integral formalism to investigate the vortex properties of a quasi-two dimensional (2D) Fermi superfluid system trapped in an optical lattice potential. Within the framework of mean-field theory, the cooper pair density, the atom number density, and the vortex core size are calculated from weakly interacting BCS regime to strongly coupled while weakly interacting BEC regime. Numerical results show that the atoms gradually penetrate into the vortex core as the system evolves from BEC to BCS regime. Meanwhile, the presence of the optical lattice allows us to analyze the vortex properties in the crossover from three-dimensional (3D) to 2D case. Furthermore, using a simple re-normalization procedure, we find that the two-body bound state exists only when the interaction is stronger than a critical one denoted by G c which is obtained as a function of the lattice potential’s parameter. Finally, we investigate the vortex core size and find that it grows with increasing interaction strength. In particular, by analyzing the behavior of the vortex core size in both BCS and BEC regimes, we find that the vortex core size behaves quite differently for positive and negative chemical potentials. Project supported by the National Natural Science Foundation of China (Grant Nos. 51331006, 51590883, and 11204321) and the Project of Chinese Academy of Sciences (Grant No. KJZD-EW-M05-3).

  5. Static Magnetic Response of Non-Fermi-Liquid Density

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Yuan

    2017-09-01

    We consider the response of the density of a fermion ensemble to an applied weak static magnetic field. It is known that, for a noninteracting Fermi gas, this response is fully characterized by the Fermi volume and the Berry curvature on the Fermi surface. Here we show the same result holds for interacting fermions, including a Fermi liquid and a non-Fermi liquid, to all orders in perturbation theory. Our result relies only on the assumption of a well-defined Fermi surface and the general analytic properties of quantum field theory, and is completely model independent.

  6. Joule-Thomson coefficient of ideal anyons within fractional exclusion statistics

    SciTech Connect

    Qin Fang; Chen Jisheng

    2011-02-15

    The analytical expressions of the Joule-Thomson coefficient for homogeneous and harmonically trapped three-dimensional ideal anyons which obey Haldane fractional exclusion statistics are derived. For an ideal Fermi gas, the Joule-Thomson coefficient is negative, which means that there is no maximum Joule-Thomson inversion temperature. With careful study, it is found that there exists a Joule-Thomson inversion temperature in the fractional exclusion statistics model. Furthermore, the relations between the Joule-Thomson inversion temperature and the statistical parameter g are investigated.

  7. Joule-Thomson coefficient of ideal anyons within fractional exclusion statistics.

    PubMed

    Qin, Fang; Chen, Ji-sheng

    2011-02-01

    The analytical expressions of the Joule-Thomson coefficient for homogeneous and harmonically trapped three-dimensional ideal anyons which obey Haldane fractional exclusion statistics are derived. For an ideal Fermi gas, the Joule-Thomson coefficient is negative, which means that there is no maximum Joule-Thomson inversion temperature. With careful study, it is found that there exists a Joule-Thomson inversion temperature in the fractional exclusion statistics model. Furthermore, the relations between the Joule-Thomson inversion temperature and the statistical parameter g are investigated.

  8. Self-similar solution of cylindrical shock wave propagation in a rotational axisymmetric mixture of a non-ideal gas and small solid particles

    NASA Astrophysics Data System (ADS)

    Nath, Gorakh

    Similarity solutions are obtained for one-dimensional isothermal and adiabatic unsteady flow behind a strong cylindrical shock wave propagating in a rotational axisymmetric dusty gas, which has a variable azimuthal fluid velocity together with a variable axial fluid velocity. The experimental studies and astrophysical observations show that the outer atmosphere of the planets rotates due to rotation of the planets. Macroscopic motion with supersonic speed occurs in an interplanetary atmosphere and shock waves are generated. Thus rotation of planets or stars significantly affect the process taking place in their outer layers, therefore question connected with the explosions in rotating gas atmospheres are of definite astrophysical interest. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-condition is maintained and variable energy input is continuously supplied by the piston. The shock Mach number is not infinite, but has a finite value. The azimuthal and axial component of the fluid velocity in the ambient medium are assume to be vary and obey power laws, and the density of the ambient medium is assumed to be constant. In order to obtain the similarity solutions the angular velocity of the ambient medium is assume to be decreasing as the distance from the axis increases. Effects of the variation of the parameter of non-idealness of the gas in the mixture, the mass concentration of solid particles and the ratio of the density of solid particles to the initial density of the gas are investigated.

  9. The Cosmic-Ray and Gas Content of the Cygnus Region as Measured in Gamma Rays by the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Belfiore, A.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Harding, A. K.; Hays, E.; Thompson, D. J.; Troja, E.

    2011-01-01

    Context. The Cygnus region hosts a giant molecular-cloud complex which actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at y-ray energies. Several gamma-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyse the gamma-ray emission measured by the Fermi Large Area Telescope in the energy range from 100 Me V to 100 Ge V in order to probe the gas and cosmic-ray content over the scale of the whole Cygnus complex. The gamma-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is largely reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse gamma-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. and a global model of the region, including other pulsars and gamma-ray sources, is sought. Results. The integral H I emissivity above 100 MeV averaged over the whole Cygnus complex amounts to 12.06 +/- 0.11 (stat.) (+0.15 -0.84) (syst.J] x 10(exp -26) photons /s / sr / H-atom, where the systematic error is dominated by the uncertainty on the H I opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average X(sub co) N(H2)/W(sub co) ratio is found to be [1.68 +/- 0.05 (stat.) (H I opacity)] x 1020 molecules cm-2 (K km/s /r, consistent with other LAT measurements in the Local Arm. We detect significant gamma-ray emission from dark neutral gas for a mass corresponding to approx 40% of that traced by CO. The total interstellar mass in the Cygnus complex inferred from its gamma-ray emission amounts to 8(+5 -1) x 10(exp 6) Solar M at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and large

  10. The cosmic-ray and gas content of the Cygnus region as measured in γ -rays by the Fermi Large Area Telescope

    SciTech Connect

    Ackermann, M.

    2012-02-01

    Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individual sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral Hi emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.) +0.15 -0.84 (syst.)] × 10-26 photons s-1 sr-1 H-atom-1, where the systematic error is dominated by the uncertainty on the Hi opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average XCO = N(H2)/WCO ratio is found to be [1.68 ± 0.05 (stat.) +0.87 -0.10 (Hi opacity)] × 1020 molecules cm-2 (K km s-1)-1, consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ~ 40% of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 +5 -1 × 106M⊙ at a distance of 1.4 kpc. Conclusions. Despite the conspicuous

  11. The cosmic-ray and gas content of the Cygnus region as measured in γ -rays by the Fermi Large Area Telescope

    DOE PAGES

    Ackermann, M.

    2012-02-01

    Context. The Cygnus region hosts a giant molecular-cloud complex that actively forms massive stars. Interactions of cosmic rays with interstellar gas and radiation fields make it shine at γ-ray energies. Several γ-ray pulsars and other energetic sources are seen in this direction. Aims. In this paper we analyze the γ-ray emission measured by the Fermi Large Area Telescope in the energy range from 100 MeV to 100 GeV in order to probe the gas and cosmic-ray content on the scale of the whole Cygnus complex. The γ-ray emission on the scale of the central massive stellar clusters and from individualmore » sources is addressed elsewhere. Methods. The signal from bright pulsars is greatly reduced by selecting photons in their off-pulse phase intervals. We compare the diffuse γ-ray emission with interstellar gas maps derived from radio/mm-wave lines and visual extinction data. A general model of the region, including other pulsars and γ-ray sources, is sought. Results. The integral Hi emissivity above 100 MeV averaged over the whole Cygnus complex amounts to [2.06 ± 0.11 (stat.) +0.15 -0.84 (syst.)] × 10-26 photons s-1 sr-1 H-atom-1, where the systematic error is dominated by the uncertainty on the Hi opacity to calculate its column densities. The integral emissivity and its spectral energy distribution are both consistent within the systematics with LAT measurements in the interstellar space near the solar system. The average XCO = N(H2)/WCO ratio is found to be [1.68 ± 0.05 (stat.) +0.87 -0.10 (Hi opacity)] × 1020 molecules cm-2 (K km s-1)-1, consistent with other LAT measurements in the Local Arm. We detect significant γ-ray emission from dark neutral gas for a mass corresponding to ~ 40% of what is traced by CO. The total interstellar mass in the Cygnus complex inferred from its γ-ray emission amounts to 8 +5 -1 × 106M⊙ at a distance of 1.4 kpc. Conclusions. Despite the conspicuous star formation activity and high masses of the interstellar clouds, the

  12. Quantum-tunneling dynamics of a spin-polarized Fermi gas in a double-well potential

    SciTech Connect

    Salasnich, L.; Mazzarella, G.; Toigo, F.; Salerno, M.

    2010-02-15

    We study the exact dynamics of a one-dimensional spin-polarized gas of fermions in a double-well potential at zero and finite temperature. Despite the system being made of noninteracting fermions, its dynamics can be quite complex, showing strongly aperiodic spatio-temporal patterns during the tunneling. The extension of these results to the case of mixtures of spin-polarized fermions interacting with self-trapped Bose-Einstein condensates (BECs) at zero temperature is considered as well. In this case we show that the fermionic dynamics remains qualitatively similar to that observed in the absence of BEC but with the Rabi frequencies of fermionic excited states explicitly depending on the number of bosons and on the boson-fermion interaction strength. From this, the possibility of controlling quantum fermionic dynamics by means of Feshbach resonances is suggested.

  13. A proof of the Biswas-Mitra-Bhattacharyya conjecture for the ideal quantum gas trapped under the generic power law potential U=\\sum\

    NASA Astrophysics Data System (ADS)

    Mehedi Faruk, Mir; Muktadir Rahman, Md

    2016-03-01

    The well known relation for ideal classical gas $\\Delta \\epsilon^2=kT^2 C_V$ which does not remain valid for quantum system is revisited. A new connection is established between energy fluctuation and specific heat for quantum gases, valid in the classical limit and the degenerate quantum regime as well. Most importantly the proposed Biswas-Mitra-Bhattacharyya (BMB) conjecture (Biswas $et.$ $al.$, J. Stat. Mech. P03013, 2015.) relating hump in energy fluctuation and discontinuity of specific heat is proved and precised in this manuscript.

  14. Quantum-mechanical engines working with an ideal gas with a finite number of particles confined in a power-law trap

    NASA Astrophysics Data System (ADS)

    Wang, Jianhui; Ma, Yongli; He, Jizhou

    2015-07-01

    Based on quantum thermodynamic processes, we make a quantum-mechanical (QM) extension of the typical heat engine cycles, such as the Carnot, Brayton, Otto, Diesel cycles, etc., with no introduction of the concept of temperature. When these QM engine cycles are implemented by an ideal gas confined in an arbitrary power-law trap, a relation between the quantum adiabatic exponent and trap exponent is found. The differences and similarities between the efficiency of a given QM engine cycle and its classical counterpart are revealed and discussed.

  15. Finite-Difference Solution for Laminar or Turbulent Boundary Layer Flow over Axisymmetric Bodies with Ideal Gas, CF4, or Equilibrium Air Chemistry

    NASA Technical Reports Server (NTRS)

    Hamilton, H. Harris, II; Millman, Daniel R.; Greendyke, Robert B.

    1992-01-01

    A computer code was developed that uses an implicit finite-difference technique to solve nonsimilar, axisymmetric boundary layer equations for both laminar and turbulent flow. The code can treat ideal gases, air in chemical equilibrium, and carbon tetrafluoride (CF4), which is a useful gas for hypersonic blunt-body simulations. This is the only known boundary layer code that can treat CF4. Comparisons with experimental data have demonstrated that accurate solutions are obtained. The method should prove useful as an analysis tool for comparing calculations with wind tunnel experiments and for making calculations about flight vehicles where equilibrium air chemistry assumptions are valid.

  16. In-flight and collisional dissipation as a mechanism to suppress Fermi acceleration in a breathing Lorentz gas.

    PubMed

    Oliveira, Diego F M; Leonel, Edson D

    2012-06-01

    Some dynamical properties for a time dependent Lorentz gas considering both the dissipative and non dissipative dynamics are studied. The model is described by using a four-dimensional nonlinear mapping. For the conservative dynamics, scaling laws are obtained for the behavior of the average velocity for an ensemble of non interacting particles and the unlimited energy growth is confirmed. For the dissipative case, four different kinds of damping forces are considered namely: (i) restitution coefficient which makes the particle experiences a loss of energy upon collisions; and in-flight dissipation given by (ii) F=-ηV(2); (iii) F=-ηV(μ) with μ≠1 and μ≠2 and; (iv) F=-ηV, where η is the dissipation parameter. Extensive numerical simulations were made and our results confirm that the unlimited energy growth, observed for the conservative dynamics, is suppressed for the dissipative case. The behaviour of the average velocity is described using scaling arguments and classes of universalities are defined.

  17. 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} .

  18. Propagation of a spherical shock wave in mixture of non-ideal gas and small solid particles under gravitational field with conductive and radiative heat fluxes

    NASA Astrophysics Data System (ADS)

    Nath, Gorakh

    Self-similar solutions are obtained for one-dimensional unsteady adiabatic flow behind a spherical shock wave propagating in a dusty gas with conductive and radiative heat fluxes under a gravitational field. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the piston. The heat conduction is express in terms of Fourier’s law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density. The medium is assumed to be under a gravitational field due to heavy nucleus at the origin (Roche Model). The unsteady model of Roche consists of a dusty gas distributed with spherical symmetry around a nucleus having large mass It is assumed that the gravitational effect of the mixture itself can be neglected compared with the attraction of the heavy nucleus. The density of the ambient medium is taken to be constant. Our analysis reveals that after inclusion of gravitational field effect surprisingly the shock strength increases and remarkable difference can be found in the distribution of flow variables. The effects of the variation of the heat transfer parameters, the gravitational parameter and non-idealness of the gas in the mixture are investigated. Also, the effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are investigated. It is found that the shock strength is increased with an increase in the value of gravitational parameter. Further, it is investigated that the presence of gravitational field increases the

  19. Dynamic density and spin responses of a superfluid Fermi gas in the BCS-BEC crossover: Path integral formulation and pair fluctuation theory

    NASA Astrophysics Data System (ADS)

    He, Lianyi

    2016-10-01

    We present a standard field theoretical derivation of the dynamic density and spin linear response functions of a dilute superfluid Fermi gas in the BCS-BEC crossover in both three and two dimensions. The derivation of the response functions is based on the elegant functional path integral approach which allows us to calculate the density-density and spin-spin correlation functions by introducing the external sources for the density and the spin density. Since the generating functional cannot be evaluated exactly, we consider two gapless approximations which ensure a gapless collective mode (Goldstone mode) in the superfluid state: the BCS-Leggett mean-field theory and the Gaussian-pair-fluctuation (GPF) theory. In the mean-field theory, our results of the response functions agree with the known results from the random phase approximation. We further consider the pair fluctuation effects and establish a theoretical framework for the dynamic responses within the GPF theory. We show that the GPF response theory naturally recovers three kinds of famous diagrammatic contributions: the Self-Energy contribution, the Aslamazov-Lakin contribution, and the Maki-Thompson contribution. We also show that unlike the equilibrium state, in evaluating the response functions, the linear (first-order) terms in the external sources as well as the induced order parameter perturbations should be treated carefully. In the superfluid state, there is an additional order parameter contribution which ensures that in the static and long wavelength limit, the density response function recovers the result of the compressibility (compressibility sum rule). We expect that the f-sum rule is manifested by the full number equation which includes the contribution from the Gaussian pair fluctuations. The dynamic density and spin response functions in the normal phase (above the superfluid critical temperature) are also derived within the Nozières-Schmitt-Rink (NSR) theory.

  20. Impact of non-idealities in gas-tracer tests on the estimation of reaeration, respiration, and photosynthesis rates in streams.

    PubMed

    Knapp, Julia L A; Osenbrück, Karsten; Cirpka, Olaf A

    2015-10-15

    Estimating respiration and photosynthesis rates in streams usually requires good knowledge of reaeration at the given locations. For this purpose, gas-tracer tests can be conducted, and reaeration rate coefficients are determined from the decrease in gas concentration along the river stretch. The typical procedure for analysis of such tests is based on simplifying assumptions, as it neglects dispersion altogether and does not consider possible fluctuations and trends in the input signal. We mathematically derive the influence of these non-idealities on estimated reaeration rates and how they are propagated onto the evaluation of aerobic respiration and photosynthesis rates from oxygen monitoring. We apply the approach to field data obtained from a gas-tracer test using propane in a second-order stream in Southwest Germany. We calculate the reaeration rate coefficients accounting for dispersion as well as trends and uncertainty in the input signals and compare them to the standard approach. We show that neglecting dispersion significantly underestimates reaeration, and results between sections cannot be compared if trends in the input signal of the gas tracer are disregarded. Using time series of dissolved oxygen and the various estimates of reaeration, we infer respiration and photosynthesis rates for the same stream section, demonstrating that the bias and uncertainty of reaeration using the different approaches significantly affects the calculation of metabolic rates.

  1. Fermi Pulsar Analysis

    NASA Image and Video Library

    This animation illustrates how analysis of Fermi data reveals new pulsars. Fermi's LAT records the precise arrival time and approximate direction of the gamma rays it detects, but to identify a pul...

  2. Role of single-point mutations and deletions on transition temperatures in ideal proteinogenic heteropolymer chains in the gas phase.

    PubMed

    Olivares-Quiroz, L

    2016-07-01

    A coarse-grained statistical mechanics-based model for ideal heteropolymer proteinogenic chains of non-interacting residues is presented in terms of the size K of the chain and the set of helical propensities [Formula: see text] associated with each residue j along the chain. For this model, we provide an algorithm to compute the degeneracy tensor [Formula: see text] associated with energy level [Formula: see text] where [Formula: see text] is the number of residues with a native contact in a given conformation. From these results, we calculate the equilibrium partition function [Formula: see text] and characteristic temperature [Formula: see text] at which a transition from a low to a high entropy states is observed. The formalism is applied to analyze the effect on characteristic temperatures [Formula: see text] of single-point mutations and deletions of specific amino acids [Formula: see text] along the chain. Two probe systems are considered. First, we address the case of a random heteropolymer of size K and given helical propensities [Formula: see text] on a conformational phase space. Second, we focus our attention to a particular set of neuropentapeptides, [Met-5] and [Leu-5] enkephalins whose thermodynamic stability is a key feature on their coupling to [Formula: see text] and [Formula: see text] receptors and the triggering of biochemical responses.

  3. Ideal CO2/Light Gas Separation Performance of Poly(vinylimidazolium) Membranes and Poly(vinylimidazolium)-Ionic Liquid Composite Films

    SciTech Connect

    Carlisle, TK; Wiesenauer, EF; Nicodemus, GD; Gin, DL; Noble, RD

    2013-01-23

    Six vinyl-based, imidazolium room-temperature ionic liquid (RTIL) monomers were synthesized and photopolymerized to form dense poly(RTIL) membranes. The effect of polymer backbone (i.e., poly(ethylene), poly(styrene), and poly(acrylate)) and functional cationic substituent (e.g., alkyl, fluoroalkyl, oligo(ethylene glycol), and disiloxane) on ideal CO2/N-2 and CO2/CH4 membrane separation performance was investigated. The vinyl-based poly(RTIL)s were found to be generally less CO2-selective compared to analogous styrene- and acrylate-based poly(RTIL)s. The CO2 permeability of n-hexyl-(69 barrers) and disiloxane- (130 barrers) substituted vinyl-based poly(RTIL)s were found to be exceptionally larger than that of previously studied styrene and acrylate poly(RTIL)s. The CO2 selectivity of oligo(ethylene glycol)-functionalized vinyl poly(RTIL)s was enhanced, and the CO2 permeability was reduced when compared to the n-hexyl-substituted vinyl-based poly(RTIL). Nominal improvement in CO2/CH4 selectivity was observed upon fluorination of the n-hexyl vinyl-based poly(RTIL), with no observed change in CO2 permeability. However, rather dramatic improvements in both CO2 permeability and selectivity were observed upon blending 20 mol % RTIL (emim Tf2N) into the n-hexyl- and disiloxane-functionalized vinyl poly(RTIL)s to form solid liquid composite films.

  4. A Method to Simulate Linear Stability of Impulsively Accelerated Density Interfaces in Ideal-MHD and Gas Dynamics

    SciTech Connect

    Ravi Samtaney

    2009-02-10

    We present a numerical method to solve the linear stability of impulsively accelerated density interfaces in two dimensions such as those arising in the Richtmyer-Meshkov instability. The method uses an Eulerian approach, and is based on an unwind method to compute the temporally evolving base state and a flux vector splitting method for the perturbations. The method is applicable to either gas dynamics or magnetohydrodynamics. Numerical examples are presented for cases in which a hydrodynamic shock interacts with a single or double density interface, and a doubly shocked single density interface. Convergence tests show that the method is spatially second order accurate for smooth flows, and between first and second order accurate for flows with shocks.

  5. Norm preserving stochastic field equation for an ideal Bose gas in a trap: numerical implementation and applications

    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.

  6. Quantum-statistical equilibrium and the ``law'' of constant Fermi potential

    NASA Astrophysics Data System (ADS)

    Le Coz, Yannick L.

    2003-02-01

    We apply the general quantum-statistical density-matrix formalism to an independent-electron gas within a space-dependent external electric potential, under equilibrium conditions. This problem is analogous to an ideal semiconductor homojunction diode. We solve the resulting equilibrium density-matrix equation using a perturbation theory. Next, we derive a first-order quantum correction to the classical Maxwell-Boltzmann density-potential formula. The correction appears as an added curvature term in external potential. It represents expected quantum-mechanical scattering against a spatially varying potential. Our results indicate that the commonly encountered thermodynamic or statistical-mechanical "law" of constant, equilibrium Fermi potential—with Fermi potential a parameter in the Maxwell-Boltzmann density-potential formula—is not fundamentally exact. In a general space-dependent potential, this "law," we prove, is simply a classical approximation.

  7. Van der Waals and ideal gas models for compressibility by means of pressure in pneumatic pipes from 1 to 100 Lpm.

    PubMed

    Mugruza Vassallo, Carlos

    2004-01-01

    The general aim is to develop a Venturi flow sensor for the inspiration line to be used in mechanical ventilation. This work is an advance for the development and construction of this sensor and to explain some of its characteristics in mechanical ventilation. The Mach number in this sensor grows with the pipe diameter, but it is less than 0.3 to diameters higher than 3mm, and according to the traditional bibliography it can be used as incompressible fluid for the design. For this reason the simulations were done between 2:1 and 6:1 to simulation pressures from 15 to 16.5 Psi (mechanical ventilation range). The results of these simulations are: it needs to consider the gas compressibility levels for Mach numbers smaller than 0.3 because the error of flow measure can be between 5 and 15% for the pattern of ideal gas and enter 7.5 to 20% for the Van Der Waals model above the incompressibility pattern, and these results were used for the construction of the small reduction the Venturi's pipe from 3 to 78 Lpm, taken from absolute pressure to complete the norm ISO9360.

  8. Comments on "Advantages and challenges in coupling an ideal gas to atomistic models in adaptive resolution simulations" by K. Kreis, A.C. Fogarty, K. Kremer and R. Potestio

    NASA Astrophysics Data System (ADS)

    Klein, R.

    2015-09-01

    Kreis et al. (Eur. Phys. J. Special Topics, this issue, 2015, doi: 10.1140/epjst/e2015-02412-1) discuss the option of minimizing the complexity of the coarse-grained model in adaptive resolution molecular dynamics simulations (AdResS) by adopting a collisionless ideal gas model for this purpose. Here we discuss the technical detail of how an ideal gas model is implemented, the effective role in the simulation that is left to the coarse-grained model when it is drastically simplified as suggested, and relations between the force and potential interpolations adopted in different variants of AdResS.

  9. Itinerant magnetic phases and quantum Lifshitz transitions in a three-dimensional repulsively interacting Fermi gas with spin-orbit coupling

    NASA Astrophysics Data System (ADS)

    Zhang, Shang-Shun; Ye, Jinwu; Liu, Wu-Ming

    2016-09-01

    Magnetic phenomena in itinerant electron systems have been at the forefront of materials science. Here we show that the Weyl spin-orbit coupling (SOC) in three-dimensional repulsively interacting itinerant Fermi systems opens up a platform to host new itinerant magnetic phases, excitations, and phase transitions. A putative ferromagnetic state (FM) is always unstable against a stripe spiral spin density wave (S-SDW) or a stripe longitudinal SDW (LSDW) at small or large SOC strengths, respectively. The stripe-ordering wave vector is given by the nesting momentum of the two SOC-split Fermi surfaces with the same or opposite helicities at small or large SOC strengths, respectively. The LSDW is accompanied by a charge density wave (CDW) with half of its pitch. The transition from the paramagnet to the SSDW or LSDW+CDW is described by quantum Lifshitz-type actions, in sharp contrast to the Hertz-Millis types for itinerant electron systems without SOC. The collective excitations and Fermi surface reconstructions inside the SSDW and LSDW+CDW are also studied. The effects of a harmonic trap in cold-atom experiments are briefly discussed. In view of recent ground-breaking experimental advances in generating two-dimensional SOC in cold atoms, these phenomena can be observed in current or near-future cold-atom experiments even at very weak interactions. They may also be relevant to some itinerant magnetic materials with a strong SOC.

  10. The Ideal Electron Gas Thermometer

    NASA Astrophysics Data System (ADS)

    Spietz, Lafe; Lehnert, K. W.; Siddiqi, Irfan; Schoelkopf, R. J.

    2003-03-01

    The wide range of thermometers used in cryogenic systems today all suffer from some combination of lack of absolute accuracy, complexity, and sensitivity to magnetic fields. We describe a primary thermometer that is fast, compact, insensitive to magnetic fields, and operates over a range from millikelvin temperatures to room temperature. The thermometer consists of a 50 Ohm tunnel junction whose noise power is measured by standard techniques of microwave radiometry. In such a junction, the thermal-shot noise is an elementary function of the applied bias voltage, the electron's charge, the Boltzmann constant, and the temperature. In contrast to Johnson noise thermometry, this method is self-calibrating and depends only on applied DC voltage, temperature, and fundamental constants. Hence this system may have metrological applications. We demonstrate the operation of this thermometer over more than three decades in temperature.

  11. Effects of a finite number of particles on the thermodynamic properties of a harmonically trapped ideal charged Bose gas in a constant magnetic field

    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.

  12. Sex Education and Ideals

    ERIC Educational Resources Information Center

    de Ruyter, Doret J.; Spiecker, Ben

    2008-01-01

    This article argues that sex education should include sexual ideals. Sexual ideals are divided into sexual ideals in the strict sense and sexual ideals in the broad sense. It is argued that ideals that refer to the context that is deemed to be most ideal for the gratification of sexual ideals in the strict sense are rightfully called sexual…

  13. Sex Education and Ideals

    ERIC Educational Resources Information Center

    de Ruyter, Doret J.; Spiecker, Ben

    2008-01-01

    This article argues that sex education should include sexual ideals. Sexual ideals are divided into sexual ideals in the strict sense and sexual ideals in the broad sense. It is argued that ideals that refer to the context that is deemed to be most ideal for the gratification of sexual ideals in the strict sense are rightfully called sexual…

  14. SU (N ) Fermi liquid at finite temperature

    NASA Astrophysics Data System (ADS)

    Cheng, Chi-Ho; Yip, S.-K.

    2017-03-01

    We consider the thermodynamic potential Ω of an N component Fermi gas with a short-range interaction obeying SU (N ) symmetry. We analyze especially the nonanalytic part of Ω in the temperature T at low T . We examine the temperature range where one can observe this T4lnT contribution and discuss how it can be extracted experimentally.

  15. Quantum phases of Fermi-Fermi mixtures in optical lattices

    NASA Astrophysics Data System (ADS)

    Iskin, M.; Sá de Melo, C. A. R.

    2008-07-01

    The ground-state phase diagram of Fermi-Fermi mixtures in optical lattices is analyzed as a function of interaction strength, population imbalance, filling fraction, and tunneling parameters. It is shown that population imbalanced Fermi-Fermi mixtures reduce to strongly interacting Bose-Fermi mixtures in the molecular limit, in sharp contrast to homogeneous or harmonically trapped systems, where the resulting Bose-Fermi mixture is weakly interacting. Furthermore, insulating phases are found in optical lattices of Fermi-Fermi mixtures in addition to the standard phase-separated or coexisting superfluid-excess-fermion phases found in homogeneous systems. The insulating states can be a molecular Bose-Mott insulator (BMI), a Fermi-Pauli insulator (FPI), a phase-separated BMI-FPI mixture, or a Bose-Fermi checkerboard.

  16. Buoyancy-Driven Heat Transfer During Application of a Thermal Gradient for the Study of Vapor Deposition at Low Pressure Using and Ideal Gas

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Hung, R. J.; Paley, M. S.; Penn, B. G.; Long, Y. T.

    1996-01-01

    A mathematical model has been developed to determine heat transfer during vapor deposition of source materials under a variety of orientations relative to gravitational accelerations. The model demonstrates that convection can occur at total pressures as low as 10-2 mm Hg. Through numerical computation, using physical material parameters of air, a series of time steps demonstrates the development of flow and temperature profiles during the course of vapor deposition. These computations show that in unit gravity vapor deposition occurs by transport through a fairly complicated circulating flow pattern when applying heat to the bottom of the vessel with parallel orientation with respect to the gravity vector. The model material parameters for air predict the effect of kinematic viscosity to be of the same order as thermal diffusivity, which is the case for Prandtl number approx. 1 fluids. Qualitative agreement between experiment and the model indicates that 6-(2-methyl-4-nitroanilino)-2,4-hexadiyn-l-ol (DAMNA) at these pressures indeed approximates an ideal gas at the experiment temperatures, and may validate the use of air physical constants. It is apparent that complicated nonuniform temperature distribution in the vapor could dramatically affect the homogeneity, orientation, and quality of deposited films. The experimental test i's a qualitative comparison of film thickness using ultraviolet-visible spectroscopy on films generated in appropriately oriented vapor deposition cells. In the case where heating of the reaction vessel occurs from the top, deposition of vapor does not normally occur by convection due to a stable stratified medium. When vapor deposition occurs in vessels heated at the bottom, but oriented relative to the gravity vector between these two extremes, horizontal thermal gradients induce a complex flow pattern. In the plane parallel to the tilt axis, the flow pattern is symmetrical and opposite in direction from that where the vessel is

  17. Fermi, Szilard and Trinity

    ERIC Educational Resources Information Center

    Anderson, Herbert L.

    1974-01-01

    The final installment of the author's recollections of his work with physicists Enrico Fermi, Leo Szilard and others in developing the first controlled nuclear chain reaction and in preparing the test explosion of the first atomic bomb. (GS)

  18. Fermi at Six Months

    NASA Technical Reports Server (NTRS)

    Hays, Elizabeth

    2009-01-01

    An overview of the Fermi Gamma-ray Space Telescope's first 6 months in operation is provided. The Fermi Gamma-ray Space Telescope, formerly called GLAST, is a mission to measure the cosmic gamma-ray flux in the energy rage 20 MeV to more than 300 GeV, with supporting measurements for gamma-ray bursts from 8 keV to 30 MeV. It contains a Large Area Telescope capable of viewing the entire sky every 3 hours and a Gamma-ray Burst Monitor for viewing the entire unocculted sky. Since its launch on June 11, 2008 Fermi has provided information on pulsars, gamma ray bursts, relativistic jets, the active galactic nucleus, and a globular star cluster. This presentation describes Fermi's development, mission, instruments and recent findings.

  19. Fermi Galactic Center Zoom

    NASA Image and Video Library

    This animation zooms into an image of the Milky Way, shown in visible light, and superimposes a gamma-ray map of the galactic center from NASA's Fermi. Raw data transitions to a view with all known...

  20. Fermi, Szilard and Trinity

    ERIC Educational Resources Information Center

    Anderson, Herbert L.

    1974-01-01

    The final installment of the author's recollections of his work with physicists Enrico Fermi, Leo Szilard and others in developing the first controlled nuclear chain reaction and in preparing the test explosion of the first atomic bomb. (GS)

  1. Connecting Few-Body Inelastic Decay to Quantum Correlations in a Many-Body System: A Weakly Coupled Impurity in a Resonant Fermi Gas

    NASA Astrophysics Data System (ADS)

    Laurent, Sébastien; Pierce, Matthieu; Delehaye, Marion; Yefsah, Tarik; Chevy, Frédéric; Salomon, Christophe

    2017-03-01

    We study three-body recombination in an ultracold Bose-Fermi mixture. We first show theoretically that, for weak interspecies coupling, the loss rate is proportional to Tan's contact. Second, using a Li 7 /Li 6 mixture we probe the recombination rate in both the thermal and dual superfluid regimes. We find excellent agreement with our model in the BEC-BCS crossover. At unitarity where the fermion-fermion scattering length diverges, we show that the loss rate is proportional to nf4 /3 , where nf is the fermionic density. This unusual exponent signals nontrivial two-body correlations in the system. Our results demonstrate that few-body losses can be used as a quantitative probe of quantum correlations in many-body ensembles.

  2. Connecting Few-Body Inelastic Decay to Quantum Correlations in a Many-Body System: A Weakly Coupled Impurity in a Resonant Fermi Gas.

    PubMed

    Laurent, Sébastien; Pierce, Matthieu; Delehaye, Marion; Yefsah, Tarik; Chevy, Frédéric; Salomon, Christophe

    2017-03-10

    We study three-body recombination in an ultracold Bose-Fermi mixture. We first show theoretically that, for weak interspecies coupling, the loss rate is proportional to Tan's contact. Second, using a ^{7}Li/^{6}Li mixture we probe the recombination rate in both the thermal and dual superfluid regimes. We find excellent agreement with our model in the BEC-BCS crossover. At unitarity where the fermion-fermion scattering length diverges, we show that the loss rate is proportional to n_{f}^{4/3}, where n_{f} is the fermionic density. This unusual exponent signals nontrivial two-body correlations in the system. Our results demonstrate that few-body losses can be used as a quantitative probe of quantum correlations in many-body ensembles.

  3. Relativistic quantum thermodynamics of ideal gases in two dimensions.

    PubMed

    Blas, H; Pimentel, B M; Tomazelli, J L

    1999-11-01

    In this work we study the behavior of relativistic ideal Bose and Fermi gases in two space dimensions. Making use of polylogarithm functions we derive a closed and unified expression for their densities. It is shown that both type of gases are essentially inequivalent, and only in the non-relativistic limit the spinless and equal mass Bose and Fermi gases are equivalent as known in the literature.

  4. Single-particle excitations in a trapped gas of Fermi atoms in the BCS-BEC crossover region. II. Broad Feshbach resonance

    SciTech Connect

    Ohashi, Y.; Griffin, A.

    2005-12-15

    We apply the formulation developed in a recent paper [Y. Ohashi and A. Griffin, Phys. Rev. A 72, 013601 (2005)] for single-particle excitations in the BCS-BEC crossover to the case of a broad Feshbach resonance. At T=0, we solve the Bogoliubov-de Gennes coupled equations taking into account a Bose condensate of bound states (molecules). In the case of a broad resonance, the density profile n(r), as well as the profile of the superfluid order parameter {delta}-tilde(r), are spatially spread out to the Thomas-Fermi radius, even in the crossover region. This order parameter {delta}-tilde(r) suppresses the effects of low-energy Andreev bound states on the rf tunneling current. As a result, the peak energy in the rf spectrum is found to occur at an energy equal to the superfluid order parameter {delta}-tilde(r=0) at the center of the trap, in contrast to the case of a narrow resonance, and in agreement with recent measurements. The local density approximation is found to give a good approximation for the rf-tunneling spectrum.

  5. Nested-Fermi-liquid theory

    SciTech Connect

    Virosztek, A.; Ruvalds, J. )

    1990-09-01

    The susceptibility and quasiparticle self-energy are found to exhibit anomalous behavior in nested-Fermi-liquid (NFL) systems that have nearly parallel sections of the Fermi surface. Electron-electron scattering yields damping much stronger than the conventional electron-gas result and predicts a linear temperature variation of the resistivity. The susceptibility {chi}{sub NFL}{sup {prime}{prime}}({bold q},{omega}) for nested fermions is calculated at {bold q}{approx equal}{bold Q}, where {bold Q} is a typical nesting wave vector. The NFL susceptibility is linear in frequency up to a crossover region near {omega}{approx equal}4{ital T} where a saturation to a constant value occurs. The above features, as well as various theoretical constraints, are highly sensitive to the strength of the electron-electron coupling and to the degree of nesting. The relevance of the NFL results to superconducting oxides is briefly examined, with emphasis on the resistivity and the photoemission data, which supports the calculated damping {Gamma}({omega}{gt}{ital T}){approx equal}{alpha}{omega} with an intermediate on-site Coulomb coupling.

  6. Bragg spectroscopy of strongly interacting Fermi gases

    NASA Astrophysics Data System (ADS)

    Lingham, M. G.; Fenech, K.; Peppler, T.; Hoinka, S.; Dyke, P.; Hannaford, P.; Vale, C. J.

    2016-10-01

    This article provides an overview of recent developments and emerging topics in the study of two-component Fermi gases using Bragg spectroscopy. Bragg scattering is achieved by exposing a gas to two intersecting laser beams with a slight frequency difference and measuring the momentum transferred to the atoms. By varying the Bragg laser detuning, it is possible to measure either the density or spin response functions which characterize the basic excitations present in the gas. Specifically, one can measure properties such as the dynamic and static structure factors, Tan's universal contact parameter and observe signatures for the onset of pair condensation locally within a gas.

  7. FermiGrid

    SciTech Connect

    Yocum, D.R.; Berman, E.; Canal, P.; Chadwick, K.; Hesselroth, T.; Garzoglio, G.; Levshina, T.; Sergeev, V.; Sfiligoi, I.; Sharma, N.; Timm, S.; /Fermilab

    2007-05-01

    As one of the founding members of the Open Science Grid Consortium (OSG), Fermilab enables coherent access to its production resources through the Grid infrastructure system called FermiGrid. This system successfully provides for centrally managed grid services, opportunistic resource access, development of OSG Interfaces for Fermilab, and an interface to the Fermilab dCache system. FermiGrid supports virtual organizations (VOs) including high energy physics experiments (USCMS, MINOS, D0, CDF, ILC), astrophysics experiments (SDSS, Auger, DES), biology experiments (GADU, Nanohub) and educational activities.

  8. Thomas-Fermi and Thomas-Fermi-Dirac models in two-dimension - Effect of strong quantizing magnetic field

    NASA Astrophysics Data System (ADS)

    De, Sanchari; Chakrabarty, Somenath

    2017-01-01

    Using Thomas-Fermi (TF) and Thomas-Fermi-Dirac (TFD) models, we have investigated the properties of electron gas inside two-dimensional (2D) Wigner-Seitz (WS) cells in presence of a strong orthogonal quantizing magnetic field. The electron-electron Coulomb exchange interaction in quasi-2D case is obtained. The exact form of exchange term in 2D is derived making the width of the system tending to zero. Further, using the exchange term, the Thomas-Fermi-Dirac equation in 2D is established. It has been observed that only the ionized WS cell can have finite radius in the Thomas-Fermi model, even in presence of a strong quantizing magnetic field. On the other hand, in the Thomas-Fermi-Dirac model a neutral WS cell can have finite radius.

  9. Nonequilibrium steady states of ideal bosonic and fermionic quantum gases.

    PubMed

    Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André

    2015-12-01

    We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013)]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.

  10. Nonequilibrium steady states of ideal bosonic and fermionic quantum gases

    NASA Astrophysics Data System (ADS)

    Vorberg, Daniel; Wustmann, Waltraut; Schomerus, Henning; Ketzmerick, Roland; Eckardt, André

    2015-12-01

    We investigate nonequilibrium steady states of driven-dissipative ideal quantum gases of both bosons and fermions. We focus on systems of sharp particle number that are driven out of equilibrium either by the coupling to several heat baths of different temperature or by time-periodic driving in combination with the coupling to a heat bath. Within the framework of (Floquet-)Born-Markov theory, several analytical and numerical methods are described in detail. This includes a mean-field theory in terms of occupation numbers, an augmented mean-field theory taking into account also nontrivial two-particle correlations, and quantum-jump-type Monte Carlo simulations. For the case of the ideal Fermi gas, these methods are applied to simple lattice models and the possibility of achieving exotic states via bath engineering is pointed out. The largest part of this work is devoted to bosonic quantum gases and the phenomenon of Bose selection, a nonequilibrium generalization of Bose condensation, where multiple single-particle states are selected to acquire a large occupation [Phys. Rev. Lett. 111, 240405 (2013), 10.1103/PhysRevLett.111.240405]. In this context, among others, we provide a theory for transitions where the set of selected states changes, describe an efficient algorithm for finding the set of selected states, investigate beyond-mean-field effects, and identify the dominant mechanisms for heat transport in the Bose-selected state.

  11. Fermi TGF detection map

    NASA Image and Video Library

    Fermi’s Gamma-ray Burst Monitor detected 130 TGFs from August 2008 to the end of 2010. Thanks to instrument tweaks, the team has been able to improve the detection rate to several TGFs per week. ...

  12. Interaction quenches of Fermi gases

    SciTech Connect

    Uhrig, Goetz S.

    2009-12-15

    It is shown that the jump in the momentum distribution of Fermi gases evolves smoothly for small and intermediate times once an interaction between the fermions is suddenly switched on. The jump does not vanish abruptly. The loci in momentum space where the jumps occur are those of the noninteracting Fermi sea. No relaxation of the Fermi surface geometry takes place.

  13. University student and K-12 teacher reasoning about the basic tenets of kinetic-molecular theory, Part I: Volume of an ideal gas

    NASA Astrophysics Data System (ADS)

    Robertson, Amy D.; Shaffer, Peter S.

    2013-04-01

    This article reports on a long-term investigation of student and teacher reasoning about the basic tenets of kinetic-molecular theory as they relate to the concept of volume. This research grew out of the finding that university-level students and practicing K-12 teachers often treat the volume of a gas as different from that of its enclosing container. We examined the extent to which this tendency might be associated with incorrect reasoning about the motions of the particles in the gas. The results suggest that teachers and students often justify incorrect answers about the volume of a gas with incorrect statements about the motion of gas particles.

  14. Research on Non-Ideal Plasmas.

    DTIC Science & Technology

    1978-07-24

    Based on Modified Debye — Huckel Theory (DUO). ... . . . . . . . 107 3.1$ Argon: Mollier Chart for Electrical Con— ductivity Using Rogov’s Asymptotic...are relegated to Section 3 .3 . 3.2.3 The Debye — Huckel Correction to Ideal Gas Theory The Debye — Huckel theory (References 3.1 to 3.14) has been...the same. — 3.2.4 Validity of the Ideal Gas Approximations and the Debye — Huckel Theory The ideal gas approach is based on the presumption that particle

  15. Fermi GBM transient searches with ADWO

    NASA Astrophysics Data System (ADS)

    Bagoly, Z.; Szécsi, D.; Balázs, L. G.; Csabai, I.; Dobos, L.; Horváth, I.; Lichtenberger, J.; Tóth, L. V.

    2017-07-01

    We present the method called Automatized Detector Weight Optimization (ADWO). This method searches for non-triggered, short-duration transients in the data-set of the Fermi's Gamma-ray Burst Monitor. The data of all available detectors and energy channels are combined. Therefore, ADWO is ideal to search for electromagnetic counterparts of gravitational wave events. We present the successful identification of all short-duration gamma-ray bursts, as well as that of the possible electromagnetic counterparts of gravitational wave transients GW150914 and LVT151012.

  16. Fermi-liquid theory of ultracold trapped Fermi gases: Implications for pseudogap physics and other strongly correlated phases

    SciTech Connect

    Chien, Chih-Chun; Levin, K.

    2010-07-15

    We show how Fermi-liquid theory can be applied to ultracold Fermi gases, thereby expanding their ''simulation'' capabilities to a class of problems of interest to multiple physics subdisciplines. We introduce procedures for measuring and calculating position-dependent Landau parameters. This lays the groundwork for addressing important controversial issues: (i) the suggestion that thermodynamically, the normal state of a unitary gas is indistinguishable from a Fermi liquid and (ii) that a fermionic system with strong repulsive contact interactions is associated with either ferromagnetism or localization; this relates as well to {sup 3}He and its p-wave superfluidity.

  17. Molecular structure and conformational composition of 1,3-dihydroxyacetone studied by combined analysis of gas-phase electron diffraction data, rotational constants, and results of theoretical calculations. Ideal gas thermodynamic properties of 1,3-dihydroxyacetone.

    PubMed

    Dorofeeva, Olga V; Vogt, Natalja; Vogt, Jürgen; Popik, Mikhail V; Rykov, Anatolii N; Vilkov, Lev V

    2007-07-19

    The molecular structure of 1,3-dihydroxyacetone (DHA) has been studied by gas-phase electron diffraction (GED), combined analysis of GED and microwave (MW) data, ab initio, and density functional theory calculations. The equilibrium re structure of DHA was determined by a joint analysis of the GED data and rotational constants taken from the literature. The anharmonic vibrational corrections to the internuclear distances (re-ra) and to the rotational constants (B(i)e-B(i)0) needed for the estimation of the re structure were calculated from the B3LYP/cc-pVTZ cubic force field. It was found that the experimental data are well reproduced by assuming that DHA consists of a mixture of three conformers. The most stable conformer of C2v symmetry has two hydrogen bonds, whereas the next two lowest energy conformers (Cs and C1 symmetry) have one hydrogen bond and their abundance is about 30% in total. A combined analysis of GED and MW data led to the following equilibrium structural parameters (re) of the most abundant conformer of DHA (the uncertainties in parentheses are 3 times the standard deviations): r(C=O)=1.215(2) A, r(C-C)=1.516(2) A, r(C-O)=1.393(2) A, r(C-H)=1.096(4) A, r(O-H)=0.967(4) A, angleC-C=O=119.9(2) degrees, angleC-C-O=111.0(2) degrees, angleC-C-H=108.2(7) degrees, angleC-O-H=106.5(7) degrees. These structural parameters reproduce the experimental B(i)0 values within 0.05 MHz. The experimental structural parameters are in good agreement with those obtained from theoretical calculations. Ideal gas thermodynamic functions (S degrees (T), C degrees p(T), and H degrees (T)-H degrees (0)) of DHA were calculated on the basis of experimental and theoretical molecular parameters obtained in this work. The enthalpy of formation of DHA, -523+/-4 kJ/mol, was calculated by the atomization procedure using the G3X method.

  18. Is highly overdoped LSCO a Fermi liquid?

    NASA Astrophysics Data System (ADS)

    Armstrong, Nathan; Hall, Jesse; Dabkowski, Antoni; Zhang, Hao; Wei, J. Y. T.; Timusk, Thomas

    2013-03-01

    According to Fermi liquid theory the ac resistivity of a metal at low temperatures should follow ρ =A' (ω2 + b(πT) 2) +ρ0 , where the coefficient b = 4 for electron-electron umklapp scattering. However, if resonant elastic electron-impurity scattering is predominant then b ~ 1 as shown by Chubukov and Maslov. A search for the ideal Fermi liquid behavior has revealed 7 known cases where b can be determined, all of which show b < 2 . 5 . Notably, not a single case approaches b = 4 as expected for a Fermi liquid. Highly overdoped La1.65Sr0.35CuO4 (LSCO), which is far beyond the superconducting dome, shows T2 resistivity at low temperature and provides another system where the nature of the scattering mechanism can be studied by optical spectroscopy. We will present our far-infrared measurements of the ab-plane of epitaxial LSCO grown by pulsed laser-ablated deposition on a substrate of SrTiO4. The authors would like to thank NSERC, CFI-OIT and CIFAR for support.

  19. A simple probabilistic model of ideal gases

    NASA Astrophysics Data System (ADS)

    Sossinsky, A. B.

    2016-01-01

    We describe a discrete 3D model of ideal gas based on the idea that, on the microscopic level, the particles move randomly (as in ASEP models), instead of obeying Newton's laws as prescribed by Boltzmann.

  20. Planck intermediate results: XXVIII. Interstellar gas and dust in the Chamaeleon clouds as seen by Fermi LAT and Planck $\\star$

    SciTech Connect

    Ade, P. A. R.; Aghanim, N.; Aniano, G.; Arnaud, M.; Ashdown, M.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Bartolo, N.; Battaner, E.; Benabed, K.; Benoit-Lévy, A.; Bernard, J. -P.; Bersanelli, M.; Bielewicz, P.; Bonaldi, A.; Bonavera, L.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Burigana, C.; Butler, R. C.; Calabrese, E.; Cardoso, J. -F.; Casandjian, J. M.; Catalano, A.; Chamballu, A.; Chiang, H. C.; Christensen, P. R.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Désert, F. -X.; Dickinson, C.; Diego, J. M.; Digel, S. W.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Ducout, A.; Dupac, X.; Efstathiou, G.; Elsner, F.; Enßlin, T. A.; Eriksen, H. K.; Falgarone, E.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Frejsel, A.; Fukui, Y.; Galeotta, S.; Galli, S.; Ganga, K.; Ghosh, T.; Giard, M.; Gjerløw, E.; González-Nuevo, J.; Górski, K. M.; Gregorio, A.; Grenier, I. A.; Gruppuso, A.; Hansen, F. K.; Hanson, D.; Harrison, D. L.; Henrot-Versillé, S.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J. -M.; Lasenby, A.; Lattanzi, M.; Lawrence, C. R.; Leonardi, R.; Levrier, F.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; Maffei, B.; Maino, D.; Mandolesi, N.; Maris, M.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Matarrese, S.; Mazzotta, P.; Melchiorri, A.; Mendes, L.; Mennella, A.; Migliaccio, M.; Miville-Deschênes, M. -A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Natoli, P.; Nørgaard-Nielsen, H. U.; Novikov, D.; Novikov, I.; Oxborrow, C. A.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Perdereau, O.; Perotto, L.; Perrotta, F.; Pettorino, V.; Piacentini, F.; Piat, M.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Popa, L.; Pratt, G. W.; Prunet, S.; Puget, J. -L.; Rachen, J. P.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ristorcelli, I.; Rocha, G.; Roudier, G.; Rusholme, B.; Sandri, M.; Santos, D.; Scott, D.; Spencer, L. D.; Stolyarov, V.; Strong, A. W.; Sudiwala, R.; Sunyaev, R.; Sutton, D.; Suur-Uski, A. -S.; Sygnet, J. -F.; Tauber, J. A.; Terenzi, L.; Tibaldo, L.; Toffolatti, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vielva, P.; Villa, F.; Wade, L. A.; Wandelt, B. D.; Wehus, I. K.; Yvon, D.; Zacchei, A.; Zonca, A.

    2015-09-30

    The nearby Chamaeleon clouds have been observed in γ rays by the Fermi Large Area Telescope (LAT) and in thermal dust emission by Planck and IRAS. Cosmic rays and large dust grains, if smoothly mixed with gas, can jointly serve with the H i and 12CO radio data to (i) map the hydrogen column densities, NH, in the different gas phases, in particular at the dark neutral medium (DNM) transition between the H i-bright and CO-bright media; (ii) constrain the CO-to-H2 conversion factor, XCO; and (iii) probe the dust properties per gas nucleon in each phase and map their spatial variations across the clouds. We have separated clouds at local, intermediate, and Galactic velocities in H i and 12CO line emission to model in parallel the γ-ray intensity recorded between 0.4 and 100 GeV; the dust optical depth at 353 GHz, τ353; the thermal radiance of the large grains; and an estimate of the dust extinction, AVQ, empirically corrected for the starlight intensity. Furthermore, the dust and γ-ray models have been coupled to account for the DNM gas. The consistent γ-ray emissivity spectra recorded in the different phases confirm that the GeV–TeV cosmic rays probed by the LAT uniformly permeate all gas phases up to the 12CO cores. The dust and cosmic rays both reveal large amounts of DNM gas, with comparable spatial distributions and twice as much mass as in the CO-bright clouds. We give constraints on the Hi-DNM-CO transitions for five separate clouds. CO-dark H2 dominates the molecular columns up to AV ≃ 0.9 and its mass often exceeds the one-third of the molecular mass expected by theory. The corrected AVQ extinction largely provides the best fit to the total gas traced by the γ rays. Nevertheless, we find evidence for a marked rise in AVQ/NH with increasing NH and molecular fraction

  1. Symmetry-protected ideal Weyl semimetal in HgTe-class materials.

    PubMed

    Ruan, Jiawei; Jian, Shao-Kai; Yao, Hong; Zhang, Haijun; Zhang, Shou-Cheng; Xing, Dingyu

    2016-04-01

    Ideal Weyl semimetals with all Weyl nodes exactly at the Fermi level and no coexisting trivial Fermi surfaces in the bulk, similar to graphene, could feature deep physics such as exotic transport phenomena induced by the chiral anomaly. Here, we show that HgTe and half-Heusler compounds, under a broad range of in-plane compressive strain, could be materials in nature realizing ideal Weyl semimetals with four pairs of Weyl nodes and topological surface Fermi arcs. Generically, we find that the HgTe-class materials with nontrivial band inversion and noncentrosymmetry provide a promising arena to realize ideal Weyl semimetals. Such ideal Weyl semimetals could further provide a unique platform to study emergent phenomena such as the interplay between ideal Weyl fermions and superconductivity in the half-Heusler compound LaPtBi.

  2. Symmetry-protected ideal Weyl semimetal in HgTe-class materials

    NASA Astrophysics Data System (ADS)

    Ruan, Jiawei; Jian, Shao-Kai; Yao, Hong; Zhang, Haijun; Zhang, Shou-Cheng; Xing, Dingyu

    2016-04-01

    Ideal Weyl semimetals with all Weyl nodes exactly at the Fermi level and no coexisting trivial Fermi surfaces in the bulk, similar to graphene, could feature deep physics such as exotic transport phenomena induced by the chiral anomaly. Here, we show that HgTe and half-Heusler compounds, under a broad range of in-plane compressive strain, could be materials in nature realizing ideal Weyl semimetals with four pairs of Weyl nodes and topological surface Fermi arcs. Generically, we find that the HgTe-class materials with nontrivial band inversion and noncentrosymmetry provide a promising arena to realize ideal Weyl semimetals. Such ideal Weyl semimetals could further provide a unique platform to study emergent phenomena such as the interplay between ideal Weyl fermions and superconductivity in the half-Heusler compound LaPtBi.

  3. Symmetry-protected ideal Weyl semimetal in HgTe-class materials

    NASA Astrophysics Data System (ADS)

    Jian, Shao-Kai; Ruan, Jiawei; Yao, Hong; Zhang, Haijun; Zhang, Shou-Cheng; Xing, Dingyu

    Ideal Weyl semimetals with all Weyl nodes exactly at the Fermi level and no coexisting trivial Fermi surfaces in the bulk, similar to graphene, could feature deep and novel physics such as exotic transport phenomena induced by the chiral anomaly. Here, we show that HgTe and half-Heusler compounds, under a broad range of inplane compressive strain, could be the first materials in nature realizing ideal Weyl semimetals with four pairs of Weyl nodes and topological surface Fermi arcs. Generically, we find that the HgTe-class materials with nontrivial band inversion and noncentrosymmetry provide a promising arena to realize ideal Weyl semimetals. Such ideal Weyl semimetals could further provide a unique platform to study emergent phenomena such as the interplay between ideal Weyl fermions and superconductivity in the half-Heusler compound LaPtBi.

  4. Symmetry-protected ideal Weyl semimetal in HgTe-class materials

    PubMed Central

    Ruan, Jiawei; Jian, Shao-Kai; Yao, Hong; Zhang, Haijun; Zhang, Shou-Cheng; Xing, Dingyu

    2016-01-01

    Ideal Weyl semimetals with all Weyl nodes exactly at the Fermi level and no coexisting trivial Fermi surfaces in the bulk, similar to graphene, could feature deep physics such as exotic transport phenomena induced by the chiral anomaly. Here, we show that HgTe and half-Heusler compounds, under a broad range of in-plane compressive strain, could be materials in nature realizing ideal Weyl semimetals with four pairs of Weyl nodes and topological surface Fermi arcs. Generically, we find that the HgTe-class materials with nontrivial band inversion and noncentrosymmetry provide a promising arena to realize ideal Weyl semimetals. Such ideal Weyl semimetals could further provide a unique platform to study emergent phenomena such as the interplay between ideal Weyl fermions and superconductivity in the half-Heusler compound LaPtBi. PMID:27033588

  5. Renormalization group and the superconducting susceptibility of a Fermi liquid

    NASA Astrophysics Data System (ADS)

    Parameswaran, S. A.; Shankar, R.; Sondhi, S. L.

    2010-11-01

    A free Fermi gas has, famously, a superconducting susceptibility that diverges logarithmically at zero temperature. In this paper we ask whether this is still true for a Fermi liquid and find that the answer is that it does not. From the perspective of the renormalization group for interacting fermions, the question arises because a repulsive interaction in the Cooper channel is a marginally irrelevant operator at the Fermi liquid fixed point and thus is also expected to infect various physical quantities with logarithms. Somewhat surprisingly, at least from the renormalization group viewpoint, the result for the superconducting susceptibility is that two logarithms are not better than one. In the course of this investigation we derive a Callan-Symanzik equation for the repulsive Fermi liquid using the momentum-shell renormalization group, and use it to compute the long-wavelength behavior of the superconducting correlation function in the emergent low-energy theory. We expect this technique to be of broader interest.

  6. Novel Superfluidity of Trapped Fermi Atoms Loaded on Optical Lattices

    NASA Astrophysics Data System (ADS)

    Machida, Masahiko; Yamada, Susumu

    2005-03-01

    We investigate a possibility of superfluidity in a trapped gas of Fermi atoms with a repulsive interaction in the presence of an optical lattice. Applying the exact diagonalization method to a one-dimensional Hubbard model including the trap potential, we find that, when the strength of the repulsive interaction exceeds a critical value, the binding energy of two Fermi atoms becomes negative below the half-filling case, indicating that an attractive interaction effectively works between Fermi atoms. In this case, a "Mott insulating core" appears in the center of the trap, where each site is occupied by one atom. The Cooper-pair correlation strongly develops between atoms in the left and right hand sides of this core. Furthermore, we show a ground-state phase diagram including the superfluidity on the trapped Fermi atoms loaded on optical lattices.

  7. Renormalization group and the superconducting susceptibility of a Fermi liquid

    SciTech Connect

    Parameswaran, S. A.; Sondhi, S. L.; Shankar, R.

    2010-11-15

    A free Fermi gas has, famously, a superconducting susceptibility that diverges logarithmically at zero temperature. In this paper we ask whether this is still true for a Fermi liquid and find that the answer is that it does not. From the perspective of the renormalization group for interacting fermions, the question arises because a repulsive interaction in the Cooper channel is a marginally irrelevant operator at the Fermi liquid fixed point and thus is also expected to infect various physical quantities with logarithms. Somewhat surprisingly, at least from the renormalization group viewpoint, the result for the superconducting susceptibility is that two logarithms are not better than one. In the course of this investigation we derive a Callan-Symanzik equation for the repulsive Fermi liquid using the momentum-shell renormalization group, and use it to compute the long-wavelength behavior of the superconducting correlation function in the emergent low-energy theory. We expect this technique to be of broader interest.

  8. Chiral non-Fermi liquids

    NASA Astrophysics Data System (ADS)

    Sur, Shouvik; Lee, Sung-Sik

    2014-07-01

    A non-Fermi liquid state without time-reversal and parity symmetries arises when a chiral Fermi surface is coupled with a soft collective mode in two space dimensions. The full Fermi surface is described by a direct sum of chiral patch theories, which are decoupled from each other in the low-energy limit. Each patch includes low-energy excitations near a set of points on the Fermi surface with a common tangent vector. General patch theories are classified by the local shape of the Fermi surface, the dispersion of the critical boson, and the symmetry group, which form the data for distinct universality classes. We prove that a large class of chiral non-Fermi liquid states exists as stable critical states of matter. For this, we use a renormalization group scheme where low-energy excitations of the Fermi surface are interpreted as a collection of (1+1)-dimensional chiral fermions with a continuous flavor labeling the momentum along the Fermi surface. Due to chirality, the Wilsonian effective action is strictly UV finite. This allows one to extract the exact scaling exponents although the theories flow to strongly interacting field theories at low energies. In general, the low-energy effective theory of the full Fermi surface includes patch theories of more than one universality classes. As a result, physical responses include multiple universal components at low temperatures. We also point out that, in quantum field theories with extended Fermi surface, a noncommutative structure naturally emerges between a coordinate and a momentum which are orthogonal to each other. We show that the invalidity of patch description for Fermi liquid states is tied with the presence of UV/IR mixing associated with the emergent noncommutativity. On the other hand, UV/IR mixing is suppressed in non-Fermi liquid states due to UV insensitivity, and the patch description is valid.

  9. Universal nodal Fermi velocity

    SciTech Connect

    Zhou, X.J.; Yoshida, T.; Lanzara, A.; Bogdanov, P.V.; Kellar, S.A.; Shen, K.M.; Yang, W.L.; Ronning, F.; Sasagawa, T.; Kakeshita, T.; Noda, T.; Eisaki, H.; Uchida, S.; Lin, C.T.; Zhou, F.; Xiong, J.W.; Ti, W.X.; Zhao, Z.X.; Fujimori, A.; Hussain, Z.; Shen, Z.-X.

    2003-05-27

    The physical properties of cuprate superconductors vary dramatically as a function of doping, evolving from antiferromagnetic insulator to superconductors, and to normal metal upon doping. They also vary among different families of compounds, most prominent being the superconducting transition temperature (Tc), which ranges from 38 K for optimally-doped (La2-xSrx)CuO4 (x=0.15) to 135 K for Hg2Ba2Ca2Cu3O10. Such dramatic changes with doping and material family have been observed in transport properties, optical response, magnetic excitation spectra, the superconducting condensation energy and superfluid density. All these seem to imply that the underlying microscopic quantities of cup rates are generally non-universal. This paper presents a striking exception by providing experimental evidence that the nodal Fermi velocity, a quantity that governs the low-energy quasiparticle dynamics along the (0,0)-(p,p) direction where the d-wave superconducting gap is zero in cuprate superconductors , is actually universal. This conclusion is based on extensive measurements from a wide range of doping, and from five families of hole-doped cuprates whose maximum Tc varies by a factor of three or more. The invariance of the nodal Fermi velocity all the way to the Mott insulator boundary clearly signals the breakdown of the conventional Fermi liquid theory where the metal-insulator transition is realized by the divergence of the effective mass near the insulator boundary. A possible way to understand this behavior is the nanoscale phase separation where doped holes tend to create a preferred local environment so that the behavior of the individual hole is more or less the same for low energy dynamics

  10. Berry Fermi liquid theory

    NASA Astrophysics Data System (ADS)

    Chen, Jing-Yuan; Son, Dam Thanh

    2017-02-01

    We develop an extension of the Landau Fermi liquid theory to systems of interacting fermions with non-trivial Berry curvature. We propose a kinetic equation and a constitutive relation for the electromagnetic current that together encode the linear response of such systems to external electromagnetic perturbations, to leading and next-to-leading orders in the expansion over the frequency and wave number of the perturbations. We analyze the Feynman diagrams in a large class of interacting quantum field theories and show that, after summing up all orders in perturbation theory, the current-current correlator exactly matches with the result obtained from the kinetic theory.

  11. New physics of metals: fermi surfaces without Fermi liquids.

    PubMed Central

    Anderson, P W

    1995-01-01

    I relate the historic successes, and present difficulties, of the renormalized quasiparticle theory of metals ("AGD" or Fermi liquid theory). I then describe the best-understood example of a non-Fermi liquid, the normal metallic state of the cuprate superconductors. PMID:11607559

  12. Conformal Fermi Coordinates

    SciTech Connect

    Dai, Liang; Pajer, Enrico; Schmidt, Fabian E-mail: Enrico.pajer@gmail.com

    2015-11-01

    Fermi Normal Coordinates (FNC) are a useful frame for isolating the locally observable, physical effects of a long-wavelength spacetime perturbation. Their cosmological application, however, is hampered by the fact that they are only valid on scales much smaller than the horizon. We introduce a generalization that we call Conformal Fermi Coordinates (CFC). CFC preserve all the advantages of FNC, but in addition are valid outside the horizon. They allow us to calculate the coupling of long- and short-wavelength modes on all scales larger than the sound horizon of the cosmological fluid, starting from the epoch of inflation until today, by removing the complications of the second order Einstein equations to a large extent, and eliminating all gauge ambiguities. As an application, we present a calculation of the effect of long-wavelength tensor modes on small scale density fluctuations. We recover previous results, but clarify the physical content of the individual contributions in terms of locally measurable effects and ''projection'' terms.

  13. From weakly to strongly interacting 2D Fermi gases

    NASA Astrophysics Data System (ADS)

    Dyke, Paul; Fenech, Kristian; Lingham, Marcus; Peppler, Tyson; Hoinka, Sascha; Vale, Chris

    2014-05-01

    We study ultracold 2D Fermi gases of 6Li formed in a highly oblate trapping potential. The potential is generated by a cylindrically focused, blue detuned TEM01 mode laser beam. Weak magnetic field curvature provides highly harmonic confinement in the radial direction and we can readily produce single clouds with an aspect ratio of 230. Our experiments investigate the dimensional crossover from 3D to 2D for a two component Fermi gas in the Bose-Einstein Condensate to Bardeen Cooper Schrieffer crossover. Observation of an elbow in measurements of the cloud width vs. atom number is consistent with populating only the lowest transverse harmonic oscillator state for weak attractive interactions. This measurement is extended to the strongly interacting region using the broad Feshbach resonance at 832 G. We also report our progress towards measurement of the 2D equation of state for an interacting 2D Fermi gas via in-situ absorption imaging.

  14. The Fermi Paradox Is Neither Fermi's Nor a Paradox

    NASA Astrophysics Data System (ADS)

    Gray, Robert H.

    2015-03-01

    The so-called Fermi paradox claims that if technological life existed anywhere else, we would see evidence of its visits to Earth-and since we do not, such life does not exist, or some special explanation is needed. Enrico Fermi, however, never published anything on this topic. On the one occasion he is known to have mentioned it, he asked 'where is everybody?'- apparently suggesting that we don't see extraterrestrials on Earth because interstellar travel may not be feasible, but not suggesting that intelligent extraterrestrial life does not exist, or suggesting its absence is paradoxical. The claim 'they are not here; therefore they do not exist' was first published by Michael Hart, claiming that interstellar travel and colonization of the galaxy would be inevitable if intelligent extraterrestrial life existed, and taking its absence here as proof that it does not exist anywhere. The Fermi paradox appears to originate in Hart's argument, not Fermi's question. Clarifying the origin of these ideas is important, because the Fermi paradox is seen by some as an authoritative objection to searching for evidence of extraterrestrial intelligence-cited in the U. S. Congress as a reason for killing NASA's SETI program on one occasion-but evidence indicates that it misrepresents Fermi's views, misappropriates his authority, deprives the actual authors of credit, and is not a valid paradox. Keywords: Astrobiology, SETI, Fermi paradox, extraterrestrial life

  15. Metastability in spin-polarized Fermi gases.

    PubMed

    Liao, Y A; Revelle, M; Paprotta, T; Rittner, A S C; Li, Wenhui; Partridge, G B; Hulet, R G

    2011-09-30

    We study the role of particle transport and evaporation on the phase separation of an ultracold, spin-polarized atomic Fermi gas. We show that the previously observed deformation of the superfluid paired core is a result of evaporative depolarization of the superfluid due to a combination of enhanced evaporation at the center of the trap and the inhibition of spin transport at the normal-superfluid phase boundary. These factors contribute to a nonequilibrium jump in the chemical potentials at the phase boundary. Once formed, the deformed state is highly metastable, persisting for times of up to 2 s.

  16. Structure, conformations, vibrations, and ideal-gas properties of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic pairs and constituent ions.

    PubMed

    Paulechka, Yauheni U; Kabo, Gennady J; Emel'yanenko, Vladimir N

    2008-12-11

    Energies, geometries, and frequencies of normal vibrations have been calculated by quantum-chemical methods for different conformers of a bis(trifluoromethylsulfonyl)imide anion (NTf2-), 1-alkyl-3-methylimidazolium cations ([C(n)mim]+, n = 2, 4, 6, 8), and [C(n)mim]NTf2 ionic pairs. The assignment of frequencies for NTf2-, [C2mim]+, and [C4mim]+ in the vibrational spectra of ionic liquids have been performed. Thermodynamic properties of [C(n)mim]NTf2, [C(n)mim]+, and NTf2- in the gas state have been calculated by the statistical thermodynamic methods. The resulting entropies are in satisfactory agreement with the values obtained from the experimental data previously reported in literature.

  17. Statistical mechanics of light elements at high pressure. V Three-dimensional Thomas-Fermi-Dirac theory. [relevant to Jovian planetary interiors

    NASA Technical Reports Server (NTRS)

    Macfarlane, J. J.; Hubbard, W. B.

    1983-01-01

    A numerical technique for solving the Thomas-Fermi-Dirac (TED) equation in three dimensions, for an array of ions obeying periodic boundary conditions, is presented. The technique is then used to calculate deviations from ideal mixing for an alloy of hydrogen and helium at zero temperature and high presures. Results are compared with alternative models which apply perturbation theory to calculation of the electron distribution, based upon the assumption of weak response of the electron gas to the ions. The TFD theory, which permits strong electron response, always predicts smaller deviations from ideal mixing than would be predicted by perturbation theory. The results indicate that predicted phase separation curves for hydrogen-helium alloys under conditions prevailing in the metallic zones of Jupiter and Saturn are very model dependent.

  18. Statistical mechanics of light elements at high pressure. V Three-dimensional Thomas-Fermi-Dirac theory. [relevant to Jovian planetary interiors

    NASA Technical Reports Server (NTRS)

    Macfarlane, J. J.; Hubbard, W. B.

    1983-01-01

    A numerical technique for solving the Thomas-Fermi-Dirac (TED) equation in three dimensions, for an array of ions obeying periodic boundary conditions, is presented. The technique is then used to calculate deviations from ideal mixing for an alloy of hydrogen and helium at zero temperature and high presures. Results are compared with alternative models which apply perturbation theory to calculation of the electron distribution, based upon the assumption of weak response of the electron gas to the ions. The TFD theory, which permits strong electron response, always predicts smaller deviations from ideal mixing than would be predicted by perturbation theory. The results indicate that predicted phase separation curves for hydrogen-helium alloys under conditions prevailing in the metallic zones of Jupiter and Saturn are very model dependent.

  19. Vortex line in the unitary Fermi gas

    SciTech Connect

    Madeira, Lucas; Vitiello, Silvio A.; Gandolfi, Stefano; Schmidt, Kevin E.

    2016-04-06

    Here, we report diffusion Monte Carlo results for the ground state of unpolarized spin-1/2 fermions in a cylindrical container and properties of the system with a vortex-line excitation. The density profile of the system with a vortex line presents a nonzero density at the core. We also calculate the ground-state energy per particle, the superfluid pairing gap, and the excitation energy per particle. Finally, these simulations can be extended to calculate the properties of vortex excitations in other strongly interacting systems such as superfluid neutron matter using realistic nuclear Hamiltonians.

  20. Strong photoassociation in a degenerate fermi gas

    NASA Astrophysics Data System (ADS)

    Rvachov, Timur; Jamison, Alan; Jing, Li; Son, Hyungmok; Ebadi, Sepehr; Jiang, Yijun; Zwierlein, Martin; Ketterle, Wolfgang

    2016-05-01

    Despite many studies there remain open questions about strong photoassociation in ultracold gases. We study the effects of strong photoassociation in ultracold fermions. Photoassociation occurs only at short range and thus can be used as a tool to probe and control the two-body correlation function in an interacting many-body system. We study the effects of strong photoassociation in 6 Li, the onset of saturation, and its effects on spin polarized and interacting spin-mixtures. This work was funded by the NSF, ARO-MURI, SAMSUNG, and NSERC.

  1. Propagation of a spherical shock wave in mixture of non-ideal gas and small solid particles under the influence of gravitational field with conductive and radiative heat fluxes

    NASA Astrophysics Data System (ADS)

    Nath, G.

    2016-01-01

    Self-similar solutions are obtained for one-dimensional unsteady adiabatic flow behind a spherical shock wave propagating in a dusty gas with conductive and radiative heat fluxes under the influence of a gravitational field. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal gas and small solid particles, in which solid particles are uniformly distributed. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the piston. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient αR are assumed to vary with temperature and density. The medium is assumed to be under the influence of a gravitational field due to central mass ( bar{m} ) at the origin (Roche Model). It is assumed that the gravitational effect of the mixture itself can be neglected compared with the attraction of the central mass. The initial density of the ambient medium is taken to be always constant. The effects of the variation of the gravitational parameter and nonidealness of the gas in the mixture are investigated. Also, the effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are investigated. It is shown that due to an increase in the gravitational parameter the compressibility of the medium at any point in the flow-field behind the shock decreases and all other flow variables and the shock strength are increased. Further, it is found that the presence of gravitational field increases the compressibility of the medium, due to which it is compressed and therefore the distance between the piston and the shock surface is reduced. The shock waves in dusty gas under the influence of a

  2. Surface Tension in Unitary Fermi Gases with Population Imbalance

    SciTech Connect

    De Silva, Theja N.; Mueller, Erich J.

    2006-08-18

    We study the effects of surface tension between normal and superfluid regions of a trapped Fermi gas at unitarity. We find that surface tension causes notable distortions in the shape of large aspect ratio clouds. Including these distortions in our theories resolves many of the apparent discrepancies among different experiments and between theory and experiments.

  3. Anisotropic non-Fermi liquids

    NASA Astrophysics Data System (ADS)

    Sur, Shouvik; Lee, Sung-Sik

    2016-11-01

    We study non-Fermi-liquid states that arise at the quantum critical points associated with the spin density wave (SDW) and charge density wave (CDW) transitions in metals with twofold rotational symmetry. We use the dimensional regularization scheme, where a one-dimensional Fermi surface is embedded in (3 -ɛ ) -dimensional momentum space. In three dimensions, quasilocal marginal Fermi liquids arise both at the SDW and CDW critical points: the speed of the collective mode along the ordering wave vector is logarithmically renormalized to zero compared to that of Fermi velocity. Below three dimensions, however, the SDW and CDW critical points exhibit drastically different behaviors. At the SDW critical point, a stable anisotropic non-Fermi-liquid state is realized for small ɛ , where not only time but also different spatial coordinates develop distinct anomalous dimensions. The non-Fermi liquid exhibits an emergent algebraic nesting as the patches of Fermi surface are deformed into a universal power-law shape near the hot spots. Due to the anisotropic scaling, the energy of incoherent spin fluctuations disperse with different power laws in different momentum directions. At the CDW critical point, on the other hand, the perturbative expansion breaks down immediately below three dimensions as the interaction renormalizes the speed of charge fluctuations to zero within a finite renormalization group scale through a two-loop effect. The difference originates from the fact that the vertex correction antiscreens the coupling at the SDW critical point whereas it screens at the CDW critical point.

  4. Ideals and Category Typicality

    ERIC Educational Resources Information Center

    Kim, ShinWoo; Murphy, Gregory L.

    2011-01-01

    Barsalou (1985) argued that exemplars that serve category goals become more typical category members. Although this claim has received support, we investigated (a) whether categories have a single ideal, as negatively valenced categories (e.g., cigarette) often have conflicting goals, and (b) whether ideal items are in fact typical, as they often…

  5. Ideals and Category Typicality

    ERIC Educational Resources Information Center

    Kim, ShinWoo; Murphy, Gregory L.

    2011-01-01

    Barsalou (1985) argued that exemplars that serve category goals become more typical category members. Although this claim has received support, we investigated (a) whether categories have a single ideal, as negatively valenced categories (e.g., cigarette) often have conflicting goals, and (b) whether ideal items are in fact typical, as they often…

  6. The Statistical Fermi Paradox

    NASA Astrophysics Data System (ADS)

    Maccone, C.

    In this paper is provided the statistical generalization of the Fermi paradox. The statistics of habitable planets may be based on a set of ten (and possibly more) astrobiological requirements first pointed out by Stephen H. Dole in his book Habitable planets for man (1964). The statistical generalization of the original and by now too simplistic Dole equation is provided by replacing a product of ten positive numbers by the product of ten positive random variables. This is denoted the SEH, an acronym standing for “Statistical Equation for Habitables”. The proof in this paper is based on the Central Limit Theorem (CLT) of Statistics, stating that the sum of any number of independent random variables, each of which may be ARBITRARILY distributed, approaches a Gaussian (i.e. normal) random variable (Lyapunov form of the CLT). It is then shown that: 1. The new random variable NHab, yielding the number of habitables (i.e. habitable planets) in the Galaxy, follows the log- normal distribution. By construction, the mean value of this log-normal distribution is the total number of habitable planets as given by the statistical Dole equation. 2. The ten (or more) astrobiological factors are now positive random variables. The probability distribution of each random variable may be arbitrary. The CLT in the so-called Lyapunov or Lindeberg forms (that both do not assume the factors to be identically distributed) allows for that. In other words, the CLT "translates" into the SEH by allowing an arbitrary probability distribution for each factor. This is both astrobiologically realistic and useful for any further investigations. 3. By applying the SEH it is shown that the (average) distance between any two nearby habitable planets in the Galaxy may be shown to be inversely proportional to the cubic root of NHab. This distance is denoted by new random variable D. The relevant probability density function is derived, which was named the "Maccone distribution" by Paul Davies in

  7. The fermi paradox is neither Fermi's nor a paradox.

    PubMed

    Gray, Robert H

    2015-03-01

    The so-called Fermi paradox claims that if technological life existed anywhere else, we would see evidence of its visits to Earth--and since we do not, such life does not exist, or some special explanation is needed. Enrico Fermi, however, never published anything on this topic. On the one occasion he is known to have mentioned it, he asked "Where is everybody?"--apparently suggesting that we do not see extraterrestrials on Earth because interstellar travel may not be feasible, but not suggesting that intelligent extraterrestrial life does not exist or suggesting its absence is paradoxical. The claim "they are not here; therefore they do not exist" was first published by Michael Hart, claiming that interstellar travel and colonization of the Galaxy would be inevitable if intelligent extraterrestrial life existed, and taking its absence here as proof that it does not exist anywhere. The Fermi paradox appears to originate in Hart's argument, not Fermi's question. Clarifying the origin of these ideas is important, because the Fermi paradox is seen by some as an authoritative objection to searching for evidence of extraterrestrial intelligence--cited in the U.S. Congress as a reason for killing NASA's SETI program on one occasion. But evidence indicates that it misrepresents Fermi's views, misappropriates his authority, deprives the actual authors of credit, and is not a valid paradox.

  8. Nonperturbative effects on the ferromagnetic transition in repulsive Fermi gases

    NASA Astrophysics Data System (ADS)

    He, Lianyi; Huang, Xu-Guang

    2012-04-01

    It is generally believed that a dilute spin-(1)/(2) Fermi gas with repulsive interactions can undergo a ferromagnetic phase transition to a spin-polarized state at a critical gas parameter (kFa)c. Previous theoretical predictions of the ferromagnetic phase transition have been based on the perturbation theory, which treats the gas parameter as a small number. On the other hand, Belitz, Kirkpatrick, and Vojta (BKV) have argued that the phase transition in clean itinerant ferromagnets is generically of first order at low temperatures, due to the correlation effects that lead to a nonanalytic term in the free energy. The second-order perturbation theory predicts a first-order phase transition at (kFa)c=1.054, consistent with the BKV argument. However, since the critical gas parameter is expected to be of order O(1), perturbative predictions may be unreliable. In this paper we study the nonperturbative effects on the ferromagnetic phase transition by summing the particle-particle ladder diagrams to all orders in the gas parameter. We consider a universal repulsive Fermi gas where the effective range effects can be neglected, which can be realized in a two-component Fermi gas of 6Li atoms by using a nonadiabatic field switch to the upper branch of a Feshbach resonance with a positive s-wave scattering length. Our theory predicts a second-order phase transition, which indicates that ferromagnetic transition in dilute Fermi gases is possibly a counterexample to the BKV argument. The predicted critical gas parameter (kFa)c=0.858 is in good agreement with the recent quantum Monte Carlo result (kFa)c=0.86 for a nearly zero-range potential [S. Pilati , Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.030405 105, 030405 (2010)]. We also compare the spin susceptibility with the quantum Monte Carlo result and find good agreement.

  9. 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.

  10. Fermi's New Pulsar Detection Technique

    NASA Image and Video Library

    To locate a pulsar in Fermi LAT data requires knowledge of the object’s sky position, its pulse period, and how the pulse rate slows over time. Computers check many different combinations of posi...

  11. The Fermi LAT Pulsars

    NASA Astrophysics Data System (ADS)

    Romani, Roger W.

    2011-08-01

    The Large Area Telescope on the Fermi satellite is an impressive pulsar discovery machine, with over 75 pulse detections and counting. The populations of radio-selected, γ-selected and millisecond pulsars are now large enough to display observational patterns in the light curves and luminosities. These patterns are starting to teach us about the physics of the emission zone, which seems dominated by open field lines near the speed of light cylinder. The sample also provides initial inferences about the pulsar population. Apparently a large fraction of neutron stars have a young energetic γ-ray emitting phase, making these objects a good probe of massive star evolution. The long-lived millisecond γ-ray pulsars are even more ubiquitous and may produce a significant fraction of the γ-ray background. In any event, it is clear that the present LAT pulsar sample is dominated by nearby objects, and there is every expectation that the number, and quality, of pulsar detections will increase in years to come.

  12. Ideal female brow aesthetics.

    PubMed

    Griffin, Garrett R; Kim, Jennifer C

    2013-01-01

    The concept of the ideal female eyebrow has changed over time. Modern studies examining youthful brow aesthetics are reviewed. An analysis of ideal female brow characteristics as depicted in the Western print media between 1945 and 2011 was performed. This analysis provided objective evidence that the ideal youthful brow peak has migrated laterally over time to lie at the lateral canthus. There has been a nonstatistically significant trend toward lower and flatter brows. These findings are discussed in relation to current concepts of female brow aging, with repercussions regarding endoscopic brow lift and aesthetic forehead surgery.

  13. Detecting Friedel oscillations in ultracold Fermi gases

    NASA Astrophysics Data System (ADS)

    Riechers, Keno; Hueck, Klaus; Luick, Niclas; Lompe, Thomas; Moritz, Henning

    2017-09-01

    Investigating Friedel oscillations in ultracold gases would complement the studies performed on solid state samples with scanning-tunneling microscopes. In atomic quantum gases interactions and external potentials can be tuned freely and the inherently slower dynamics allow to access non-equilibrium dynamics following a potential or interaction quench. Here, we examine how Friedel oscillations can be observed in current ultracold gas experiments under realistic conditions. To this aim we numerically calculate the amplitude of the Friedel oscillations which are induced by a potential barrier in a 1D Fermi gas and compare it to the expected atomic and photonic shot noise in a density measurement. We find that to detect Friedel oscillations the signal from several thousand one-dimensional systems has to be averaged. However, as up to 100 parallel one-dimensional systems can be prepared in a single run with present experiments, averaging over about 100 images is sufficient.

  14. Quantum Oscillations from Fermi Arcs

    NASA Astrophysics Data System (ADS)

    Pereg-Barnea, Tamar; Refael, Gil; Franz, Marcel; Weber, Heidi; Seradjeh, Babak

    2009-03-01

    Recent experiments[1] in a variety of High Tc superconductors revel 1/B oscillations in the vortex-liquid state. The period of oscillations in underdoped samples is short and can be translated, via the Onsager relation to an area in k-space which makes up a few percents of the Brillouin zone. Quantum oscillations are usually thought of as arising from closed orbits in momentum space along the Fermi surface and are used to measure the Fermi vector. Thus, the observation of quantum oscillations in the cuprates seems to be at odds with the observation of Fermi arcs in ARPES experiments[2] due to their fragmented Fermi surface topology. In this talk we show that quantum oscillations can arise from a partially gapped Fermi surface. We adopt a phenomenological model of arcs which terminate at a regime with a superconducting gap of d-wave symmetry to describe the pseudo gap phase. Without invoking any additional order, quantization of energy is found well below the gap maximum. Semiclassically the quantization condition arises from closed orbits in real-space. When translated to momentum space, the area enclosed by the orbits is much smaller than that of the full Fermi surface. [1]N. Doiron-Leyaraud et al. nature 447, 565 (2007) [2]Kanigel et al. Nature Physics 2 447 (2006)

  15. Ideals in intimate relationships.

    PubMed

    Fletcher, G J; Simpson, J A; Thomas, G; Giles, L

    1999-01-01

    This research examined lay relationship and partner ideals in romantic relationships from both a social-cognitive and an evolutionary perspective. Studies 1 and 2 revealed that the qualities of an ideal partner were represented by 3 factors (partner warmth-trustworthiness, vitality-attractiveness, and status-resources), whereas the qualities of an ideal relationship were represented by 2 factors (relationship intimacy-loyalty and passion). A confirmatory factor analysis in Study 3 replicated these factor structures but found considerable overlap across the partner and relationship dimensions. Studies 4 and 5 produced convergent and discriminant validity evidence for all 5 factors. Study 6 indicated that the higher the consistency between the ideals and related assessments of the current partner and relationship, the more positively the current relationship was evaluated.

  16. Gas

    MedlinePlus

    ... intestine. Certain foods may cause gas. Foods that produce gas in one person may not cause gas in another. You can reduce the amount of gas you have by Drinking lots of water and non-fizzy drinks Eating more slowly so you swallow less air ...

  17. NASA's Fermi Telescope Resolves Radio Galaxy Centaurus A

    NASA Image and Video Library

    2017-09-28

    NASA release April 1, 2010 Fermi's Large Area Telescope resolved high-energy gamma rays from an extended region around the active galaxy Centaurus A. The emission corresponds to million-light-year-wide radio-emitting gas thrown out by the galaxy's supersized black hole. This inset shows an optical/gamma-ray composite of the galaxy and its location on the Fermi one-year sky map. Credit: NASA/DOE/Fermi LAT Collaboration, Capella Observatory To learn more about these images go to: www.nasa.gov/mission_pages/GLAST/news/smokestack-plumes.html NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

  18. Time evolution of excitations in normal Fermi liquids

    NASA Astrophysics Data System (ADS)

    Pavlyukh, Y.; Rubio, A.; Berakdar, J.

    2013-05-01

    We inspect the initial and the long-time evolution of excitations in Fermi liquids by analyzing the time structure of the electron spectral function. Focusing on the short-time limit we study the electron-boson model for the homogeneous electron gas and apply the first-order (in boson propagator) cumulant expansion of the electron Green's function. In addition to a quadratic decay in time upon triggering the excitation, we identify nonanalytic terms in the time expansion similar to those found in the Fermi edge singularity phenomenon. We also demonstrate that the exponential decay in time in the long-time limit is inconsistent with the GW approximation for the self-energy. The background for this is the Paley-Wiener theorem of complex analysis. To reconcile with the Fermi liquid behavior an inclusion of higher order diagrams (in the screened Coulomb interaction) is required.

  19. Developmental Idealism in China

    PubMed Central

    Thornton, Arland; Xie, Yu

    2016-01-01

    This paper examines the intersection of developmental idealism with China. It discusses how developmental idealism has been widely disseminated within China and has had enormous effects on public policy and programs, on social institutions, and on the lives of individuals and their families. This dissemination of developmental idealism to China began in the 19th century, when China met with several military defeats that led many in the country to question the place of China in the world. By the beginning of the 20th century, substantial numbers of Chinese had reacted to the country’s defeats by exploring developmental idealism as a route to independence, international respect, and prosperity. Then, with important but brief aberrations, the country began to implement many of the elements of developmental idealism, a movement that became especially important following the assumption of power by the Communist Party of China in 1949. This movement has played a substantial role in politics, in the economy, and in family life. The beliefs and values of developmental idealism have also been directly disseminated to the grassroots in China, where substantial majorities of Chinese citizens have assimilated them. These ideas are both known and endorsed by very large numbers in China today. PMID:28316833

  20. Developmental Idealism in China.

    PubMed

    Thornton, Arland; Xie, Yu

    2016-10-01

    This paper examines the intersection of developmental idealism with China. It discusses how developmental idealism has been widely disseminated within China and has had enormous effects on public policy and programs, on social institutions, and on the lives of individuals and their families. This dissemination of developmental idealism to China began in the 19(th) century, when China met with several military defeats that led many in the country to question the place of China in the world. By the beginning of the 20(th) century, substantial numbers of Chinese had reacted to the country's defeats by exploring developmental idealism as a route to independence, international respect, and prosperity. Then, with important but brief aberrations, the country began to implement many of the elements of developmental idealism, a movement that became especially important following the assumption of power by the Communist Party of China in 1949. This movement has played a substantial role in politics, in the economy, and in family life. The beliefs and values of developmental idealism have also been directly disseminated to the grassroots in China, where substantial majorities of Chinese citizens have assimilated them. These ideas are both known and endorsed by very large numbers in China today.

  1. Idealization and empirical testing

    NASA Astrophysics Data System (ADS)

    Shaffer, Michael John

    It has been argued that the presence of idealizations in physical theories implies that scientific realism is false. Furthermore, it has also been argued that because physical theories incorporate idealizations scientific theories must be accepted a priori, because the objects, processes, etc. quantified over in such expressions cannot be observed in the actual world. I argue against the former view by showing that scientific realism is compatible with the fact that all theoretical claims depend on idealizing assumptions, at least when such claims are properly regimented as a special kind of counterfactual conditional. To this end a logic incorporating such conditionals, VCP, is constructed and given a semantic basis. Given VCP, the latter problem is considered in light of extant theories of confirmation, and all are found to be incapable of dealing with the acceptance of theoretical claims that depend on idealizing assumptions. In addressing this problem it is also shown that a new problem arises for subjective Bayesians concerning prior probabilities of theoretical claims that depend on idealizing assumptions. Insofar as I claim that all theoretical claims depend on idealizing assumptions, this problem for Bayesian confirmation theory appears to be quite serious. I conclude that only inference to the best explanation, when understood in terms of VCP, can provide a rational basis for the empirical acceptance of such theoretical claims.

  2. The Fermi blazar sequence

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Righi, C.; Costamante, L.; Tavecchio, F.

    2017-07-01

    We revisit the blazar sequence exploiting the complete, flux-limited sample of blazars with known redshift detected by the Fermi satellite after 4 yr of operations (the 3LAC sample). We divide the sources into γ-ray luminosity bins, collect all the archival data for all blazars, and construct their spectral energy distribution (SED). We describe the average SED of blazars in the same luminosity bin through a simple phenomenological function consisting of two broken power laws connecting with a power law describing the radio emission. We do that separately for BL Lacs and for flat spectrum radio quasars (FSRQs) and also for all blazars together. The main results are: (i) FSRQs display approximately the same SED as the luminosity increases, but the relative importance of the high-energy peak increases; (ii) as a consequence, the X-ray spectra of FSRQs become harder for larger luminosities; (iii) BL Lacs indeed form a sequence: they become redder (i.e. smaller peak frequencies) with increasing luminosities, with a softer γ-ray slope and a larger dominance of the high-energy peak; (iv) for all blazars (BL Lacs+FSRQs), these properties become more prominent, as the highest luminosity bin is populated mostly by FSRQs and the lowest luminosity bin mostly by BL Lacs. This agrees with the original blazar sequence, although BL Lacs never have an average γ-ray slope as hard as found in the original sequence. (v) At high luminosities, a large fraction of FSRQs show signs of thermal emission from the accretion disc, contributing to the optical-UV (ultraviolet).

  3. From ultracold Fermi Gases to Neutron Stars

    NASA Astrophysics Data System (ADS)

    Salomon, Christophe

    2012-02-01

    Ultracold dilute atomic gases can be considered as model systems to address some pending problem in Many-Body physics that occur in condensed matter systems, nuclear physics, and astrophysics. We have developed a general method to probe with high precision the thermodynamics of locally homogeneous ultracold Bose and Fermi gases [1,2,3]. This method allows stringent tests of recent many-body theories. For attractive spin 1/2 fermions with tunable interaction (^6Li), we will show that the gas thermodynamic properties can continuously change from those of weakly interacting Cooper pairs described by Bardeen-Cooper-Schrieffer theory to those of strongly bound molecules undergoing Bose-Einstein condensation. First, we focus on the finite-temperature Equation of State (EoS) of the unpolarized unitary gas. Surprisingly, the low-temperature properties of the strongly interacting normal phase are well described by Fermi liquid theory [3] and we localize the superfluid phase transition. A detailed comparison with theories including recent Monte-Carlo calculations will be presented. Moving away from the unitary gas, the Lee-Huang-Yang and Lee-Yang beyond-mean-field corrections for low density bosonic and fermionic superfluids are quantitatively measured for the first time. Despite orders of magnitude difference in density and temperature, our equation of state can be used to describe low density neutron matter such as the outer shell of neutron stars. [4pt] [1] S. Nascimbène, N. Navon, K. Jiang, F. Chevy, and C. Salomon, Nature 463, 1057 (2010) [0pt] [2] N. Navon, S. Nascimbène, F. Chevy, and C. Salomon, Science 328, 729 (2010) [0pt] [3] S. Nascimbène, N. Navon, S. Pilati, F. Chevy, S. Giorgini, A. Georges, and C. Salomon, Phys. Rev. Lett. 106, 215303 (2011)

  4. The Heat Capacity of Ideal Gases

    ERIC Educational Resources Information Center

    Scott, Robert L.

    2006-01-01

    The heat capacity of an ideal gas has been shown to be calculable directly by statistical mechanics if the energies of the quantum states are known. However, unless one makes careful calculations, it is not easy for a student to understand the qualitative results. Why there are maxima (and occasionally minima) in heat capacity-temperature curves…

  5. The Heat Capacity of Ideal Gases

    ERIC Educational Resources Information Center

    Scott, Robert L.

    2006-01-01

    The heat capacity of an ideal gas has been shown to be calculable directly by statistical mechanics if the energies of the quantum states are known. However, unless one makes careful calculations, it is not easy for a student to understand the qualitative results. Why there are maxima (and occasionally minima) in heat capacity-temperature curves…

  6. The Fermiac or Fermi's Trolley

    NASA Astrophysics Data System (ADS)

    Coccetti, F.

    2016-03-01

    The Fermiac, known also as Fermi's trolley or Monte Carlo trolley, is an analog computer used to determine the change in time of the neutron population in a nuclear device, via the Monte Carlo method. It was invented by Enrico Fermi and constructed by Percy King at Los Alamos in 1947, and used for about two years. A replica of the Fermiac was built at INFN mechanical workshops of Bologna in 2015, on behalf of the Museo Storico della Fisica e Centro Studi e Ricerche "Enrico Fermi", thanks to the original drawings made available by Los Alamos National Laboratory (LANL). This reproduction of the Fermiac was put in use, and a simulation was developed.

  7. Lasing in Bose-Fermi mixtures

    PubMed Central

    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

  8. Lasing in Bose-Fermi mixtures

    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.

  9. The Ideal Academy.

    ERIC Educational Resources Information Center

    Jervis, Jane L.

    1995-01-01

    This article discusses the faculty appointment system at Evergreen State College (Washington), which does not have tenure, academic departments, or academic ranks, in light of an ideal system that might have a core of long-term faculty supplemented by short-term faculty. It considers the need to balance institutional flexibility with faculty…

  10. The ideal fluid.

    PubMed

    Russell, Lyndal; McLean, Anthony S

    2014-08-01

    The characteristics of an ideal intravenous fluid in the critically ill patient are discussed. Intravenous fluids are the most frequent drug administered to patients. Questioning the use of commonly administered intravenous fluids has resulted in an increased focus on their efficacy and safety. Discrimination between fluids currently in use has been the central theme of many recent large studies, and emerging from these findings is an understanding of characteristics that would make for an ideal fluid for critically ill patients. There is increased morbidity and mortality with high chloride-containing crystalloid solutions and hydroxyethyl starch preparations, with resultant international governmental agency warnings regarding hydroxyethyl starch . The ideal fluid is one which achieves the aim of administration while minimizing or negating adverse effects, is inexpensive, and sufficiently stable when stored to be used in a wide range of clinical settings. The ideal fluid currently does not exist. Of existing options, use of hydroxyethyl starches and high chloride-containing crystalloid solutions should be discouraged. There is a lack of direct evidence that a balanced crystalloid solution confers benefit, however, the trend of recent data would support future investigation into the advantage of balanced solution over 0.9% saline.

  11. The Ideal Promotion Effort.

    ERIC Educational Resources Information Center

    Morris, Edward L.

    The ideal promotional effort for an educational television (ETV) station is dependent on a professional approach to the problem. This means that each ETV station should employ a public relations manager and should keep him informed about all major station decisions. The Public Broadcasting Service (PBS) has a campaign of its own to bring attention…

  12. The Ideal Academy.

    ERIC Educational Resources Information Center

    Jervis, Jane L.

    1995-01-01

    This article discusses the faculty appointment system at Evergreen State College (Washington), which does not have tenure, academic departments, or academic ranks, in light of an ideal system that might have a core of long-term faculty supplemented by short-term faculty. It considers the need to balance institutional flexibility with faculty…

  13. Quaternions and ideal flows

    NASA Astrophysics Data System (ADS)

    Eshraghi, H.; Gibbon, J. D.

    2008-08-01

    After a review of some of the recent works by Holm and Gibbon on quaternions and their application to Lagrangian flows, particularly the incompressible Euler equations and the equations of ideal MHD, this paper investigates the compressible and relativistic Euler equations using these methods.

  14. Fermi Finds Youthful Pulsar Among Ancient Stars

    NASA Image and Video Library

    In three years, NASA's Fermi has detected more than 100 gamma-ray pulsars, but something new has appeared. Among a type of pulsar with ages typically numbering a billion years or more, Fermi has fo...

  15. Momentum sharing in imbalanced Fermi systems

    SciTech Connect

    Hen, O.; Sargsian, M.; Weinstein, L. B.; Piasetzky, E.

    2014-10-16

    The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions (usually neutrons) to have a higher average momentum. Our high-energy electron scattering measurements using 12C, 27Al, 56Fe and 208Pb targets show that, even in heavy neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few body systems to neutron stars and may also be observable experimentally in two-spin state, ultra-cold atomic gas systems.

  16. Momentum sharing in imbalanced Fermi systems

    DOE PAGES

    Hen, O.; Sargsian, M.; Weinstein, L. B.; ...

    2014-10-16

    The atomic nucleus is composed of two different kinds of fermions, protons and neutrons. If the protons and neutrons did not interact, the Pauli exclusion principle would force the majority fermions (usually neutrons) to have a higher average momentum. Our high-energy electron scattering measurements using 12C, 27Al, 56Fe and 208Pb targets show that, even in heavy neutron-rich nuclei, short-range interactions between the fermions form correlated high-momentum neutron-proton pairs. Thus, in neutron-rich nuclei, protons have a greater probability than neutrons to have momentum greater than the Fermi momentum. This finding has implications ranging from nuclear few body systems to neutron starsmore » and may also be observable experimentally in two-spin state, ultra-cold atomic gas systems.« less

  17. Effective-range dependence of two-dimensional Fermi gases

    NASA Astrophysics Data System (ADS)

    Schonenberg, L. M.; Verpoort, P. C.; Conduit, G. J.

    2017-08-01

    The Feshbach resonance provides precise control over the scattering length and effective range of interactions between ultracold atoms. We propose the ultratransferable pseudopotential to model effective interaction ranges -1.5 ≤kF2Reff2≤0 , where Reff is the effective range and kF is the Fermi wave vector, describing narrow to broad Feshbach resonances. We develop a mean-field treatment and exploit the pseudopotential to perform a variational and diffusion Monte Carlo study of the ground state of the two-dimensional Fermi gas, reporting on the ground-state energy, contact, condensate fraction, momentum distribution, and pair-correlation functions as a function of the effective interaction range across the BEC-BCS crossover. The limit kF2Reff2→-∞ is a gas of bosons with zero binding energy, whereas ln(kFa )→-∞ corresponds to noninteracting bosons with infinite binding energy.

  18. Quasi-two-dimensional Fermi gases at finite temperatures

    NASA Astrophysics Data System (ADS)

    Fischer, Andrea M.; Parish, Meera M.

    2014-12-01

    We consider a Fermi gas with short-range attractive interactions that is confined along one direction by a tight harmonic potential. For this quasi-two-dimensional (quasi-2D) Fermi gas, we compute the pressure equation of state, radiofrequency spectrum, and the superfluid critical temperature Tc using a mean-field theory that accounts for all the energy levels of the harmonic confinement. Our calculation for Tc provides a natural generalization of the Thouless criterion to the quasi-2D geometry, and it correctly reduces to the 3D expression derived from the local density approximation in the limit where the confinement frequency ωz→0 . Furthermore, our results suggest that Tc can be enhanced by relaxing the confinement and perturbing away from the 2D limit.

  19. CCC and the Fermi paradox

    NASA Astrophysics Data System (ADS)

    Gurzadyan, V. G.; Penrose, R.

    2016-01-01

    Within the scheme of conformal cyclic cosmology (CCC), information can be transmitted from aeon to aeon. Accordingly, the "Fermi paradox" and the SETI programme --of communication by remote civilizations-- may be examined from a novel perspective: such information could, in principle, be encoded in the cosmic microwave background. The current empirical status of CCC is also discussed.

  20. Economics and the Fermi Paradox

    NASA Astrophysics Data System (ADS)

    Hosek, W. R.

    A resolution of the Fermi paradox is proposed using common economic assumptions that should apply to all intelligent, planet-bound civilizations. It is argued that seemingly rational decisions about resource allocation will lead all civilizations to forego the commitment to interstellar exploration and colonization. Consequently humans have not, and will not, be visited by them and humans will not visit other civilizations.

  1. A Student's View of Fermi

    NASA Astrophysics Data System (ADS)

    Friedman, Jerome

    2010-02-01

    This talk will provide recollections of Fermi and the lively environment he created at the University of Chicago from the perspective of a student who had the great privilege of taking of his courses and becoming a member of his research group. The period to be covered is 1951 to 1954. )

  2. Fermi's Large Area Telescope (LAT)

    NASA Image and Video Library

    Fermi’s Large Area Telescope (LAT) is the spacecraft’s main scientificinstrument. This animation shows a gamma ray (purple) entering the LAT,where it is converted into an electron (red) and a...

  3. Fermi's β-DECAY Theory

    NASA Astrophysics Data System (ADS)

    Yang, Chen Ning

    2013-05-01

    Throughout his lifetime Enrico Fermi (1901-1954) had considered his 1934 β-decay theory as his most important contribution to theoretical physics. E. Segrè (1905-1989) had vividly written about an episode at the inception of that paper:1...

  4. Fermi GBM Early Trigger Characteristics

    SciTech Connect

    Connaughton, Valerie; Briggs, Michael; Paciesas, Bill; Meegan, Charles

    2009-05-25

    Since the launch of the Fermi observatory on June 11 2008, the Gamma-ray Burst Monitor (GBM) has seen approximately 250 triggers of which about 150 were cosmic gamma-ray bursts (GRBs). GBM operates dozens of trigger algorithms covering various energy bands and timescales and is therefore sensitive to a wide variety of phenomena, both astrophysical and not.

  5. STEM education and Fermi problems

    NASA Astrophysics Data System (ADS)

    Holubova, Renata

    2017-01-01

    One of the research areas of Physics education is the study of the educational process. Investigations in this area are aimed for example on the teaching and learning process and its results. The conception of STEM education (Science, Technology, Engineering, and Mathematics) is discussed - it is one possible approach to the preparation of the curriculum and the focus on the educational process at basic and secondary schools. At schools in the Czech Republic STEM is much more realized by the application of interdisciplinary relations between subjects Physics-Nature-Technique. In both conceptions the aim is to support pupils' creativity, critical thinking, cross-curricular links. In this context the possibility of using Fermi problems in teaching Physics was discussed (as an interdisciplinary and constructivist activity). The aim of our research was the analysis of Fermi problems solving strategies, the ability of pupils to solve Fermi problems. The outcome of our analysis was to find out methods and teaching strategies which are important to use in teaching - how to solve qualitative and interdisciplinary tasks in physics. In this paper the theoretical basis of STEM education and Fermi problems will be presented. The outcome of our findings based on the research activities will be discussed so as our experiences from 10 years of Fermi problems competition that takes place at the Science Faculty, Palacky University in Olomouc. Changes in competencies of solving tasks by our students (from the point of view in terms of modern, activating teaching methods recommended by theory of Physics education and other science subjects) will be identified.

  6. Ideal Integrating Bolometer

    NASA Technical Reports Server (NTRS)

    Kogut, A.; DiPirro, M.; Moseley, S. H.

    2004-01-01

    We describe a new "ideal integrator" bolometer as a prototype for a new generation of sensitive, flexible far-IR detectors suitable for use in large arrays. The combination of a non-dissipative sensor coupled with a fast heat switch provides breakthrough capabilities in both sensitivity and operation. The bolometer temperature varies linearly with the integrated infrared power incident on the detector, and may be sampled intermittently without loss of information between samples. The sample speed and consequent dynamic range depend only on the heat switch reset cycle and can be selected in software. Between samples, the device acts as an ideal integrator with noise significantly lower than resistive bolometers. Since there is no loss of information between samples, the device is well-suited for large arrays. A single SQUID readout could process an entire column of detectors, greatly reducing the complexity, power requirements, and cost of readout electronics for large pixel arrays.

  7. Delivering ideal employee experiences.

    PubMed

    Weiss, Marjorie D; Tyink, Steve; Kubiak, Curt

    2009-05-01

    Employee-centric strategies have moved from employee satisfaction and brand awareness to employee "affinity" or "attachment." In today's marketplace, occupational health nurses understand that differentiation (i.e., the perception of uniqueness) is the direct result of superior employee interactions, which lead to better employee care, enduring employee relationships, loyal employees, and satisfied employers. What drives employees to occupational health nurse attachment? The answer is a passion for rising above the competition to create ideal employee experiences.

  8. Equation of state for a partially ionized gas. II.

    PubMed

    Baker, George A

    2003-11-01

    The derivation of equations of state for fluid phases of a partially ionized gas or plasma is addressed from a fundamental point of view. A spherical cellular model is deduced for the hot curve limit (or ideal Fermi gas). Next the Coulomb interactions are added to the spherical cellular model for general ionic charge Z. Then an independent electron model within a Z electron cell plus several many-body effects are employed. Numerical examples of the theory for several elements (H, Li, N, Na, K, Ni, Rb, Pd, Cs, and Er) are reported. These results reduce in various limits of temperature and density to the expected behavior. They display electron, localization-delocalization phase transitions of liquid-gas character. In the higher Z elements, a second possible critical point has been found. The critical pressure, electron density and temperature for the lower-density critical points seem to obey power laws as a function of Z.

  9. Topological Fermi-liquid theory for interacting Weyl metals with time reversal symmetry breaking

    NASA Astrophysics Data System (ADS)

    Jho, Yong-Soo; Han, Jae-Ho; Kim, Ki-Seok

    2017-05-01

    Introducing both the Berry curvature and the chiral anomaly into Landau's Fermi-liquid theory, we construct a topological Fermi-liquid theory, applicable to interacting Weyl metals in the absence of time reversal symmetry. Following the Landau's Fermi-liquid theory, we obtain an effective free-energy functional in terms of the density field of chiral fermions, where the band structure is modified, involved with an emergent magnetic dipole moment due to the Berry curvature. The density field of chiral fermions is determined by a self-consistent equation, minimizing the effective free-energy functional with respect to the order-parameter field. Beyond these thermodynamic properties, we construct a Boltzmann transport theory to encode both the Berry curvature and the chiral anomaly in the presence of forward scattering of a Fermi-liquid state, essential for understanding dynamic correlations in interacting Weyl metals. This generalizes the Boltzmann transport theory for the Landau's Fermi-liquid state in the respect of incorporating the topological structure and extends that for noninteracting Weyl metals in the sense of introducing the forward scattering. Finally, we justify this topological Fermi-liquid theory, generalizing the first-quantization description for noninteracting Weyl metals into the second-quantization representation for interacting Weyl metals. First, we introduce a topological Fermi-gas theory, integrating over high-energy electronic degrees of freedom deep inside a pair of chiral Fermi surfaces. As a result, we reproduce a topologically modified Drude model with both the Berry curvature and the chiral anomaly, given by the first-quantization description. Second, we take into account interactions between such low-energy chiral fermions on the pair of chiral Fermi surfaces. Following the Landau's Fermi-liquid theory, we perform the renormalization group analysis. We find that only forward scattering turns out to be marginal above possible

  10. Topological non-Fermi liquid

    NASA Astrophysics Data System (ADS)

    Cai, Rong-Gen; Qi, Yong-Hui; Wu, Yue-Liang; Zhang, Yun-Long

    2017-06-01

    The (2 +1 )-dimensional non-Fermi liquid (NFL) has a dual description in the (3 +1 )-dimensional anti-de Sitter (AdS) spacetime. We begin with a dyonic Reissner-Nordstrom (RN) black brane background, and consider the bulk Dirac fermion field coupled with the background U (1 ) gauge field, as well an intrinsic axial gauge field which is induced by chiral anomaly. The axial gauge field is effectively induced from the topological term in the bulk, which would lead to nontrivial effects on the boundary NFL. We study these effects through calculating the retarded Green's functions of the dual NFL holographically, in both analytical and numerical approaches. We also obtain correlation functions in the low frequency limit at zero and finite temperatures, as well as the dispersion spectrum of the Dirac cones, Fermi arc of the surface states, which can be related with the experiment.

  11. Fermi resonance in optical microcavities

    NASA Astrophysics Data System (ADS)

    Yi, Chang-Hwan; Yu, Hyeon-Hye; Lee, Ji-Won; Kim, Chil-Min

    2015-04-01

    Fermi resonance is a phenomenon of quantum mechanical superposition, which most often occurs between normal and overtone modes in molecular systems that are nearly coincident in energy. We find that scarred resonances in deformed dielectric microcavities are the very phenomenon of Fermi resonance, that is, a pair of quasinormal modes interact with each other due to coupling and a pair of resonances are generated through an avoided resonance crossing. Then the quantum number difference of a pair of quasinormal modes, which is a consequence of quantum mechanical superposition, equals periodic orbits, whereby the resonances are localized on the periodic orbits. We derive the relation between the quantum number difference and the periodic orbits and confirm it in an elliptic, a rectangular, and a stadium-shaped dielectric microcavity.

  12. Fermi Timing and Synchronization System

    SciTech Connect

    Wilcox, R.; Staples, J.; Doolittle, L.; Byrd, J.; Ratti, A.; Kaertner, F.X.; Kim, J.; Chen, J.; Ilday, F.O.; Ludwig, F.; Winter, A.; Ferianis, M.; Danailov, M.; D'Auria, G.

    2006-07-19

    The Fermi FEL will depend critically on precise timing of its RF, laser and diagnostic subsystems. The timing subsystem to coordinate these functions will need to reliably maintain sub-100fs synchronicity between distant points up to 300m apart in the Fermi facility. The technology to do this is not commercially available, and has not been experimentally demonstrated in a working facility. Therefore, new technology must be developed to meet these needs. Two approaches have been researched by different groups working with the Fermi staff. At MIT, a pulse transmission scheme has been developed for synchronization of RF and laser devices. And at LBL, a CW transmission scheme has been developed for RF and laser synchronization. These respective schemes have advantages and disadvantages that will become better understood in coming years. This document presents the work done by both teams, and suggests a possible system design which integrates them both. The integrated system design provides an example of how choices can be made between the different approaches without significantly changing the basic infrastructure of the system. Overall system issues common to any synchronization scheme are also discussed.

  13. Enrico Fermi and the Dolomites

    NASA Astrophysics Data System (ADS)

    Battimelli, Giovanni; de Angelis, Alessandro

    2014-11-01

    Summer vacations in the Dolomites were a tradition among the professors of the Faculty of Mathematical and Physical Sciences at the University of Roma since the end of the XIX century. Beyond the academic walls, people like Tullio Levi-Civita, Federigo Enriques and Ugo Amaldi sr., together with their families, were meeting friends and colleagues in Cortina, San Vito, Dobbiaco, Vigo di Fassa and Selva, enjoying trekking together with scientific discussions. The tradition was transmitted to the next generations, in particular in the first half of the XX century, and the group of via Panisperna was directly connected: Edoardo Amaldi, the son of the mathematician Ugo sr., rented at least during two summers, in 1925 and in 1949, and in the winter of 1960, a house in San Vito di Cadore, and almost every year in the Dolomites; Enrico Fermi was a frequent guest. Many important steps in modern physics, in particular the development of the Fermi-Dirac statistics and the Fermi theory of beta decay, are related to scientific discussions held in the region of the Dolomites.

  14. Capturing medical students' idealism.

    PubMed

    Smith, Janice K; Weaver, Donna B

    2006-01-01

    Students' idealism and desire to work with underserved populations decline as they progress from preclinical training through clerkships and residency. With an increasingly diverse population and increasing health disparities, academic health centers need to incorporate changes in their curricula to train socially responsible and idealistic physicians. International electives can provide valuable learning experiences to help achieve these goals. Sixty-six preclinical medical students at the University of Texas Medical Branch participated in an international elective from 1997 to 2005. After 1 week of didactics, they spent 3 weeks as part of a multidisciplinary medical team in rural Nicaragua. Postelective questionnaires were administered. From students' responses, we identified common learning themes and grouped them under the categories of attitudes, awareness, and skills. Limitations included a self-selection bias, lack of a control group, and limited follow-up. After the elective, students had an increased interest in volunteerism, humanitarian efforts, and working with underserved populations both in the United States and abroad, as well as more compassion toward the underserved. Students also reported a heightened awareness of social determinants of health and public health, and a broadened global perspective, as well as increased self-awareness. Our findings illustrate that a well-structured, mentored experience in international health can have a positive impact on preclinical students' attitudes, including their compassion, volunteerism, and interest in serving under-served populations, all measures of idealism.

  15. Capturing Medical Students’ Idealism

    PubMed Central

    Smith, Janice K.; Weaver, Donna B.

    2006-01-01

    PURPOSE Students’ idealism and desire to work with underserved populations decline as they progress from preclinical training through clerkships and residency. With an increasingly diverse population and increasing health disparities, academic health centers need to incorporate changes in their curricula to train socially responsible and idealistic physicians. International electives can provide valuable learning experiences to help achieve these goals. METHODS Sixty-six preclinical medical students at the University of Texas Medical Branch participated in an international elective from 1997 to 2005. After 1 week of didactics, they spent 3 weeks as part of a multidisciplinary medical team in rural Nicaragua. Postelective questionnaires were administered. From students’ responses, we identified common learning themes and grouped them under the categories of attitudes, awareness, and skills. Limitations included a self-selection bias, lack of a control group, and limited follow-up. RESULTS After the elective, students had an increased interest in volunteerism, humanitarian efforts, and working with underserved populations both in the United States and abroad, as well as more compassion toward the underserved. Students also reported a heightened awareness of social determinants of health and public health, and a broadened global perspective, as well as increased self-awareness. CONCLUSIONS Our findings illustrate that a well-structured, mentored experience in international health can have a positive impact on preclinical students’ attitudes, including their compassion, volunteerism, and interest in serving under-served populations, all measures of idealism. PMID:17003160

  16. Fermi/Non-Fermi Mixing in SU(N) Kondo Effect

    NASA Astrophysics Data System (ADS)

    Kimura, Taro; Ozaki, Sho

    2017-08-01

    We apply conformal field theory analysis to the k-channel SU(N) Kondo system, and find a peculiar behavior in the cases N > k > 1, which we call Fermi/non-Fermi mixing: The low temperature scaling is described as the Fermi liquid, while the zero temperature infrared fixed point exhibits the non-Fermi liquid signature. We also show that the Wilson ratio is no longer universal for the cases N > k > 1. The deviation from the universal value of the Wilson ratio could be used as an experimental signal of the Fermi/non-Fermi mixing.

  17. Nonrelativisitic Ideal Gases and Lorentz Violations

    NASA Astrophysics Data System (ADS)

    Colladay, D.; McDonald, P.

    2005-04-01

    We develop statistical mechanics for a nonrelativisitic ideal gas in the presence of Lorentz violating background fields. The analysis is performed using the Standard-Model Extension (SME). We derive the corresponding laws of thermodynamics and find that, to lowest order in Lorentz violation, the scalar thermodynamic variables are corrected by a rotationally invariant combination of the Lorentz terms which can be interpreted in terms of a (frame dependent) effective mass. We find that spin couplings can induce a temperature independent polarization in the gas that is not present in the conventional case.

  18. Momentum-resolved spectroscopy of a Fermi liquid

    PubMed Central

    Doggen, Elmer V. H.; Kinnunen, Jami J.

    2015-01-01

    We consider a recent momentum-resolved radio-frequency spectroscopy experiment, in which Fermi liquid properties of a strongly interacting atomic Fermi gas were studied. Here we show that by extending the Brueckner-Goldstone model, we can formulate a theory that goes beyond basic mean-field theories and that can be used for studying spectroscopies of dilute atomic gases in the strongly interacting regime. The model hosts well-defined quasiparticles and works across a wide range of temperatures and interaction strengths. The theory provides excellent qualitative agreement with the experiment. Comparing the predictions of the present theory with the mean-field Bardeen-Cooper-Schrieffer theory yields insights into the role of pair correlations, Tan's contact, and the Hartree mean-field energy shift. PMID:25941948

  19. Landau Theory of Helical Fermi Liquids.

    PubMed

    Lundgren, Rex; Maciejko, Joseph

    2015-08-07

    We construct a phenomenological Landau theory for the two-dimensional helical Fermi liquid found on the surface of a three-dimensional time-reversal invariant topological insulator. In the presence of rotation symmetry, interactions between quasiparticles are described by ten independent Landau parameters per angular momentum channel, by contrast with the two (symmetric and antisymmetric) Landau parameters for a conventional spin-degenerate Fermi liquid. We project quasiparticle states onto the Fermi surface and obtain an effectively spinless, projected Landau theory with a single projected Landau parameter per angular momentum channel that captures the spin-momentum locking or nontrivial Berry phase of the Fermi surface. As a result of this nontrivial Berry phase, projection to the Fermi surface can increase or lower the angular momentum of the quasiparticle interactions. We derive equilibrium properties, criteria for Fermi surface instabilities, and collective mode dispersions in terms of the projected Landau parameters. We briefly discuss experimental means of measuring projected Landau parameters.

  20. Pulsar Timing with the Fermi LAT

    DTIC Science & Technology

    2010-12-01

    Pulsar Timing with the Fermi LAT Paul S. Ray∗, Matthew Kerr†, Damien Parent∗∗ and the Fermi PSC‡ ∗Naval Research Laboratory, 4555 Overlook Ave., SW...Laboratory, Washington, DC 20375, USA ‡Fermi Pulsar Search Consortium Abstract. We present an overview of precise pulsar timing using data from the Large...unbinned photon data. In addition to determining the spindown behavior of the pulsars and detecting glitches and timing noise, such timing analyses al

  1. Ideal thermodynamic processes of oscillatory-flow regenerative engines will go to ideal stirling cycle?

    NASA Astrophysics Data System (ADS)

    Luo, Ercang

    2012-06-01

    This paper analyzes the thermodynamic cycle of oscillating-flow regenerative machines. Unlike the classical analysis of thermodynamic textbooks, the assumptions for pistons' movement limitations are not needed and only ideal flowing and heat transfer should be maintained in our present analysis. Under such simple assumptions, the meso-scale thermodynamic cycles of each gas parcel in typical locations of a regenerator are analyzed. It is observed that the gas parcels in the regenerator undergo Lorentz cycle in different temperature levels, whereas the locus of all gas parcels inside the regenerator is the Ericson-like thermodynamic cycle. Based on this new finding, the author argued that ideal oscillating-flow machines without heat transfer and flowing losses is not the Stirling cycle. However, this new thermodynamic cycle can still achieve the same efficiency of the Carnot heat engine and can be considered a new reversible thermodynamic cycle under two constant-temperature heat sinks.

  2. Traces, ideals, and arithmetic means

    PubMed Central

    Kaftal, Victor; Weiss, Gary

    2002-01-01

    This article grew out of recent work of Dykema, Figiel, Weiss, and Wodzicki (Commutator structure of operator ideals) which inter alia characterizes commutator ideals in terms of arithmetic means. In this paper we study ideals that are arithmetically mean (am) stable, am-closed, am-open, soft-edged and soft-complemented. We show that many of the ideals in the literature possess such properties. We apply these notions to prove that for all the ideals considered, the linear codimension of their commutator space (the “number of traces on the ideal”) is either 0, 1, or ∞. We identify the largest ideal which supports a unique nonsingular trace as the intersection of certain Lorentz ideals. An application to elementary operators is given. We study properties of arithmetic mean operations on ideals, e.g., we prove that the am-closure of a sum of ideals is the sum of their am-closures. We obtain cancellation properties for arithmetic means: for principal ideals, a necessary and sufficient condition for first order cancellations is the regularity of the generator; for second order cancellations, sufficient conditions are that the generator satisfies the exponential Δ2-condition or is regular. We construct an example where second order cancellation fails, thus settling an open question. We also consider cancellation properties for inclusions. And we find and use lattice properties of ideals associated with the existence of “gaps.” PMID:12032287

  3. First Light on GRBs with Fermi

    DTIC Science & Technology

    2010-08-04

    two months later, in early August 2008, shortly before being renamed after Enrico Fermi . In these 16 months, <∼ 1 GRB per month was detected with the...ar X iv :1 00 8. 08 54 v1 [ as tr o- ph .H E ] 4 A ug 2 01 0 First Light on GRBs with Fermi Charles D. Dermer on behalf of the Fermi ...Collaboration Code 7653, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375-5352 USA Abstract. Fermi LAT (Large Area Telescope) and GBM

  4. Bioterrorism and the Fermi Paradox

    NASA Astrophysics Data System (ADS)

    Cooper, Joshua

    2013-04-01

    We proffer a contemporary solution to the so-called Fermi Paradox, which is concerned with conflict between Copernicanism and the apparent paucity of evidence for intelligent alien civilizations. In particular, we argue that every community of organisms that reaches its space-faring age will (1) almost immediately use its rocket-building computers to reverse-engineer its genetic chemistry and (2) self-destruct when some individual uses said technology to design an omnicidal pathogen. We discuss some of the possible approaches to prevention with regard to Homo sapiens' vulnerability to bioterrorism, particularly on a short-term basis.

  5. The ideal physician entrepreneur.

    PubMed

    Bottles, K

    2000-01-01

    How does the sometimes elusive and high-stakes world of venture capital really work? How can physician executives with innovative ideas or new technologies approach venture capitalists to help them raise capital to form a start-up company? These important questions are explored in this new column on the physician as entrepreneur. The ideal physician executive is described as: (1) an expert in an area that Wall Street perceives as hot; (2) a public speaker who can enthusiastically communicate scientific and business plans to a variety of audiences; (3) a team leader who is willing to share equity in the company with other employees; (4) a recruiter and a motivator; (5) an implementer who can achieve milestones quickly that allow the company to go public as soon as possible; and (6) a realist who does not resent the terms of the typical deal. The lucrative world of the venture capitalists is foreign territory for physician executives and requires a great idea, charisma, risk-taking, connections, patience, and perseverance to navigate it successfully.

  6. Space Sciences and Idealism

    NASA Astrophysics Data System (ADS)

    Popov, M.

    Erwin Schrodinger suggested that " Scientific knowledge forms part of the idealistic background of human life", which exalted man from a nude and savage state to true humanity [Science and Humanism, Cambridge, 1961, p9]. Modern space sciences an space exploration are a brilliant demonstration of the validity of Schrodinger's thesis on Idealism. Moreover, Schrodingers thesis could be considered also as a basic principle for the New Educational Space Philosophical Project "TIMAEUS"."TIMAEUS" is not only an attempt to to start a new dialogue between Science, the Humanities and Religion; but also it is an origin of the cultural innovations of our so strange of globilisation. TIMAEUS, thus, can reveal Idealism as something more fundamental , more refined, more developed than is now accepted by the scientific community and the piblic. TIMAEUS has a significant cultural agenda, connected with the high orbital performance of the synthetic arts, combining a knowledge of the truly spiritual as well as the universal. In particular, classical ballet as a synthetic art can be a new and powerful perfector and re-creator of the real human, real idealistic, real complex culture in orbit. As is well known, Carlo Blasis, the most important dance theorist of the 19t h .century, made probably the first attempts to use the scientific ideas of Leonardo da Vinci and Isaac Newton for the understanding of the gravitational nature of balance and allegro in ballet. In particular Blasis's idea of the limited use of the legs in classical dance realised by the gifted pupils of Enrico Cecchetti - M.Fokine, A.Pavlova and V.Nijinsky, with thinkable purity and elegance of style. V.Nijinsky in his remarkable animation of the dance of two dimensional creatures of a Euclidean flat world (L'Apres Midi d'un Faune,1912) discovered that true classical dance has some gravitational limits. For example, Nijinsky's Faunes and Nymphs mut use running on the heels (In accordance with "Partitura" 1916); they

  7. The realities of idealism.

    PubMed

    Roslyn, J J

    1993-04-01

    I started out asking the question can we achieve our goals and are our goals realistic in the 1990s? I believe that we can achieve anything that we set our minds to. Our goals of providing quality care to our patients, performing research, teaching the next generation, and having an impact on our local environment are worth pursuing. However, the rules have changed and the status quo is simply not good enough. If we are to survive, we must be prepared for the future. You have the ability to change and the power to control the future. You are the future. Seize the opportunity and get involved. Become knowledgeable about health care economics, become involved with the political process, and position yourselves so that you can be a part of the solution to our health care system's woes. Don't allow the moment to pass. Don't be afraid of the realities of today, and don't forget your ideals and principles. Confront today's challenges with the same determination that academic surgeons through the years have confronted the unknown mysteries of disease. Let me conclude by trying to synthesize my remarks in five generic recommendations: 1. We need to go forward in the research area by developing multidisciplinary programs that involve basic science. These programs can be used to highlight our clinical areas and expertise. In this manner, both areas will be benefitted. 2. We need to educate the public and the government about the virtues of research and the importance of maintaining academic surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

  8. Superfluid Thomas—Fermi approximation for trapped fermi gases

    NASA Astrophysics Data System (ADS)

    Hernández, E. S.; Capuzzi, P.; Szybisz, L.

    2009-02-01

    We present a generalization of fermionic fluiddynamics to the case of two trapped fermion species with a contact interaction. Within a mean field approximation, we derive coupled equations of motion for the particle densities, particle currents, and anomalous pair density. For an inhomogeneous system, the equilibrium situation with vanishing currents is described by a generalized Thomas-Fermi relation that includes the superfluid gap, together with a new nonlocal gap equation that replaces the usual BCS one. These equations are numericaly solved resorting to a local density approximation (LDA). Density and gap profiles are analyzed in terms of the scattering length, revealing that the current frame can exhibit microscopic details of quantum origin that are frequently absent in more macroscopic scenarios.

  9. Researching Acquisition Sequences: Idealization and De-Idealization in SLA

    ERIC Educational Resources Information Center

    Ellis, Rod

    2015-01-01

    Idealization plays a fundamental role in scientific inquiry. This article examines the case for maintaining the claim that the second language acquisition (SLA) of grammatical structures such as negation manifests identifiable stages of acquisition. It proposes that, while research has demonstrated the need for de-idealization, there is no need to…

  10. Fermi surface of YBCO by DHVA

    SciTech Connect

    Smith, J.L.; Fowler, C.M.; Freeman, B.L.; Hults, W.L.; King, J.C.; Mueller, F.M.

    1991-01-01

    These proceedings demonstrate how far scientist have come in the last four years of high temperature superconductivity. Knowledge of the energy bands and Fermi surfaces from experiment has come rather late. Photoemission, first showed proof of the validity of the energy band calculations. Positron annihilation, presented by West, after a rough start, is now giving evidence of the Fermi surface. Both of these techniques involve electronic excitations and hence, although they show the Fermi surface, do not put as severe a constraint on various models for superconductivity as does the de Haas-van Alphen (dHvA) effect. This is a true measurement of the electronic ground state in an applied magnetic field where the frequency of oscillatory magnetization yields extremal cross-sectional areas of the Fermi surface. The authors have already reported some of their Fermi surface work at two conferences but present here discussion of several more important aspects of the work. 11 refs., 2 figs.

  11. Cooling and thermometry of atomic Fermi gases

    NASA Astrophysics Data System (ADS)

    Onofrio, R.

    2016-11-01

    We review the status of cooling techniques aimed at achieving the deepest quantum degeneracy for atomic Fermi gases. We first discuss some physics motivations, providing a quantitative assessment of the need for deep quantum degeneracy in relevant physics cases, such as the search for unconventional superfluid states. Attention is then focused on the most widespread technique to reach deep quantum degeneracy for Fermi systems, sympathetic cooling of Bose - Fermi mixtures, organizing the discussion according to the specific species involved. Various proposals to circumvent some of the limitations on achieving the deepest Fermi degeneracy, and their experimental realizations, are then reviewed. Finally, we discuss the extension of these techniques to optical lattices and the implementation of precision thermometry crucial to the understanding of the phase diagram of classical and quantum phase transitions in Fermi gases.

  12. Reaching a Fermi-superfluid state near an orbital Feshbach resonance

    NASA Astrophysics Data System (ADS)

    Xu, Junjun; Zhang, Ren; Cheng, Yanting; Zhang, Peng; Qi, Ran; Zhai, Hui

    2016-09-01

    We propose to realize a strongly interacting Fermi superfluid near a narrow Feshbach resonance using the recently discovered "orbital Feshbach resonance." The orbital Feshbach resonance is a type of magnetic field tunable scattering resonance theoretically predicted and experimentally observed recently in the alkaline-earth-metal-like 173Yb atom. We first show that the orbital Feshbach resonance is a narrow resonance in energy, while it is hundreds Gauss wide in terms of magnetic field strength, taking the advantage that the magnetic moment difference between the open and closed channels is quite small. Therefore, this is an ideal platform for the experimental realization of a strongly interacting Fermi superfluid with narrow resonance. We further show that the transition temperature for the Fermi superfluid in this system, especially at the BCS side of the resonance, is even higher than that in a wide resonance, which is also due to the narrow character of this resonance. Our results will encourage experimental efforts to realize Fermi superfluid in the alikaline-earth-metal-like 173Yb system, the properties of which will be complementary to extensively studied Fermi superfluids nearby a wide resonance in alkali-metal 40K and 6Li systems.

  13. Stability of spinor Fermi gases in tight waveguides

    SciTech Connect

    Campo, A. del; Muga, J. G.; Girardeau, M. D.

    2007-07-15

    The two- and three-body correlation functions of the ground state of an optically trapped ultracold spin-(1/2) Fermi gas (SFG) in a tight waveguide [one-dimensional (1D) regime] are calculated in the plane of even- and odd-wave coupling constants, assuming a 1D attractive zero-range odd-wave interaction induced by a 3D p-wave Feshbach resonance, as well as the usual repulsive zero-range even-wave interaction stemming from 3D s-wave scattering. The calculations are based on the exact mapping from the SFG to a 'Lieb-Liniger-Heisenberg' model with delta-function repulsions depending on isotropic Heisenberg spin-spin interactions, and indicate that the SFG should be stable against three-body recombination in a large region of the coupling constant plane encompassing parts of both the ferromagnetic and antiferromagnetic phases. However, the limiting case of the fermionic Tonks-Girardeau gas, a spin-aligned 1D Fermi gas with infinitely attractive p-wave interactions, is unstable in this sense. Effects due to the dipolar interaction and a Zeeman term due to a resonance-generating magnetic field do not lead to shrinkage of the region of stability of the SFG.

  14. Enhancement effect of mass imbalance on Fulde-Ferrell-Larkin-Ovchinnikov type of pairing in Fermi-Fermi mixtures of ultracold quantum gases

    NASA Astrophysics Data System (ADS)

    Wang, Jibiao; Che, Yanming; Zhang, Leifeng; Chen, Qijin

    2017-01-01

    Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a 6Li–40K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level. We present various phase diagrams related to the FFLO states at both zero and finite temperatures, throughout the BCS-BEC crossover, and show that a large mass ratio may enhance substantially FFLO type of pairing.

  15. Enhancement effect of mass imbalance on Fulde-Ferrell-Larkin-Ovchinnikov type of pairing in Fermi-Fermi mixtures of ultracold quantum gases

    PubMed Central

    Wang, Jibiao; Che, Yanming; Zhang, Leifeng; Chen, Qijin

    2017-01-01

    Ultracold two-component Fermi gases with a tunable population imbalance have provided an excellent opportunity for studying the exotic Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states, which have been of great interest in condensed matter physics. However, the FFLO states have not been observed experimentally in Fermi gases in three dimensions (3D), possibly due to their small phase space volume and extremely low temperature required for an equal-mass Fermi gas. Here we explore possible effects of mass imbalance, mainly in a 6Li–40K mixture, on the one-plane-wave FFLO phases for a 3D homogeneous case at the mean-field level. We present various phase diagrams related to the FFLO states at both zero and finite temperatures, throughout the BCS-BEC crossover, and show that a large mass ratio may enhance substantially FFLO type of pairing. PMID:28051145

  16. Scattering properties of weakly-bound dimers of Fermi atoms

    NASA Astrophysics Data System (ADS)

    Petrov, Dmitry

    2005-03-01

    We discuss the behavior of weakly bound bosonic dimers formed in a two-component Fermi gas with a large positive scattering length for the interspecies interaction. We present a theoretical approach for solving a few-body scattering problem and describe the physics of dimer-dimer elastic and inelastic scattering. We explain why these diatomic molecules, while in the highest ro-vibrational level, are characterized by remarkable collisional stability. Co-authors are Christophe Salomon, LKB, Ecole Normale Superieure, Paris, France; Georgy Shlyapnikov, LPTMS, University of South Paris, Orsay, France.

  17. Geometrically frustrated coarsening dynamics in spinor Bose-Fermi mixtures

    NASA Astrophysics Data System (ADS)

    Phuc, Nguyen Thanh; Momoi, Tsutomu; Furukawa, Shunsuke; Kawaguchi, Yuki; Fukuhara, Takeshi; Ueda, Masahito

    2017-01-01

    Coarsening dynamics theory describes equilibration of a broad class of systems. By studying the relaxation of a periodic array of microcondensates immersed in a Fermi gas, which mediates long-range spin interactions to simulate frustrated classical magnets, we show that coarsening dynamics can be suppressed by geometrical frustration. The system is found to eventually approach a metastable state which is robust against random field noise and characterized by finite correlation lengths together with the emergence of topologically stable Z2 vortices. We find universal scaling laws with no thermal-equilibrium analog that relate the correlation lengths and the number of vortices to the degree of frustration in the system.

  18. Ideal stars and General Relativity

    NASA Astrophysics Data System (ADS)

    Frønsdal, Christian

    2007-12-01

    We study a system of differential equations that governs the distribution of matter in the theory of General Relativity. The new element in this paper is the use of a dynamical action principle that includes all the degrees of freedom, matter as well as metric. The matter lagrangian defines a relativistic version of non-viscous, isentropic hydrodynamics. The matter fields are a scalar density and a velocity potential; the conventional, four-vector velocity field is replaced by the gradient of the potential and its scale is fixed by one of the Eulerian equations of motion, an innovation that significantly affects the imposition of boundary conditions. If the density is integrable at infinity, then the metric approaches the Schwarzschild metric at large distances. There are stars without boundary and with finite total mass; the metric shows rapid variation in the neighbourhood of the Schwarzschild radius and there is a very small core where a singularity indicates that the gas laws break down. For stars with boundary there emerges a new, critical relation between the radius and the gravitational mass, a consequence of the stronger boundary conditions. Tentative applications are suggested, to certain Red Giants, and to neutron stars, but the investigation reported here was limited to homogeneous polytropes. Comparison with the results of Oppenheimer and Volkoff on neutron cores shows a close agreement of numerical results. However, in the model the boundary of the star is fixed uniquely by the required matching of the interior metric to the external Schwarzschild metric, which is not the case in the traditional approach. There are solutions for which the metric is very close to the Schwarzshild metric everywhere outside the horizon, where the source is concentrated. The Schwarzschild metric is interpreted as the metric of an ideal, limiting configuration of matter, not as the metric of empty space.

  19. Fermi surface measurements of lutetium

    NASA Astrophysics Data System (ADS)

    Johanson, W. R.; Crabtree, G. W.; Schmidt, F. A.

    1982-03-01

    We report de Haas-van Alphen (dHvA) measurements of the Fermi surface of lutetium at temperatures down to 0.3 K and in fields up to 150 kG in the (101¯0) and (112¯0) planes. Lutetium, having a filled 4f shell, serves as a nonmagnetic prototype of the structurally similar (hcp), trivalent, heavy rare earths from Gd to Tm. No complete frequency branches were observed, indicating that there are no closed pieces of surface. We observed all but one orbit predicted by relativistic-augmented-plane wave (RAPW) calculations of Keeton and Loucks, and the data support a geometry that is in good qualitative agreement with the existence of nested open electron and hole sheets.

  20. Fermi surface measurements of lutetium

    SciTech Connect

    Johanson, W.R.; Crabtree, G.W.; Schmidt, F.A.

    1982-03-01

    We report de Haas-van Alphen (dHvA) measurements of the Fermi surface of lutetium at temperatures down to 0.3 K and in fields up to 150 kG in the (1010) and (1120) planes. Lutetium, having a filled 4f shell, serves as a nonmagnetic prototype of the structurally similar (hcp), trivalent, heavy rare earths from Gd to Tm. No complete frequency branches were observed, indicating that there are no closed pieces of surface. We observed all but one orbit predicted by relativistic-augmented-plane wave (RAPW) calculations of Keeton and Loucks, and the data support a geometry that is in good qualitative agreement with the existence of nested open electron and hole sheets.