相关论文: First sound velocity in liquid $^{4}$He
On the basis of the expression for the density matrix of interacting Bose particles in the coordinate representation with regard for the direct three- and four-particle correlations [I.O.\,\,Vakarchuk and O.I.\,\,Hryhorchak,…
Longitudinal sound wave propagation has been studied in an aerogel-liquid $^4$He system for various porosities of aerogel. The superfluid transition was identified as the absorption peak, whose magnitude was suppressed by aerogel. The sound…
Bulk, shear, and compressional aggregate sound velocities of hydrogen and helium in the close- packed hexagonal structure are calculated over a wide pressure range using two complementary approaches: semi-empirical lattice dynamics based on…
We investigate the first sound of a normal dilute and ultracold two-component Fermi gas in a harmonic microtube, i.e. a cylinder with harmonic transverse radial confinement in the length-scale of microns. We show that the velocity of the…
In this paper we calculate kinetic, potential and full energy with three- and four-particle direct correlations taken into account at wide temperature region on the base of the density matrix of the interacting Bose-particles [I. O.…
We present a new technique for probing the properties of quantum fluids in restricted geometries. We have confined liquid 4He within microfluidic devices formed from glass wafers, in which one dimension is on the micro scale. Using an…
The sound velocity of some liquid elements of groups IV, V and VI, as reported in the literature, displays anomalous features that set them apart from other liquid metals. In an effort to determine a possible common origin of these…
We introduce a minimal model of ultracentral heavy-ion collisions to study the relation between the speed of sound of the produced plasma and the final particles' energy and multiplicity. We discuss how the particles' multiplicity…
New theoretical formulae of the sound velocity and the B/A nonlinearity parameter for some fluids are presented in the paper. Semi--ideal and van der Waals models of gas are considered and the parameters are compared to experiment data. The…
Superfluids support many different types of sound waves. We investigate the relation between the sound waves in a relativistic and a non-relativistic superfluid by using hydrodynamics to calculate the various sound speeds. Then, using a…
A self-consistent approach is applied for the calculations within the two-time temperature Green functions formalism in the random phase approximation. The effective mass of He4 atom is computed as $m^*=1.58 m$. The excitation spectrum is…
Experimental data suggests that, at temperatures below 1 K, the pressure in liquid helium has a cubic dependence on density. Thus the speed of sound scales as a cubic root of pressure. Near a critical pressure point, this speed approaches…
In this paper we propose five different modifications of the hard sphere potential for the modeling a short-range repulsion and the calculation of thermodynamic and transport properties of liquid He4. We calculate the potential energy, the…
A new method is proposed for the calculation of full density matrix and thermodynamic functions of a many-boson system. Explicit expressions are obtained in the pair correlations approximation for an arbitrary temperature. The theory is…
Formation of fourth-sound shock waves in narrow channels filled with superfluid helium is studied. Physical and mathematical conditions at the surface of discontinuity are established. These conditions differ somewhat from those in case of…
The speed of longitudinal sound waves at 7 and 22 MHz has been measured in liquid, supecooled, and amorphous selenium, including the region around the glass transition temperature, Tg, near 35 C. In amorphous selenium the speed of shear…
Accurately determining bubble wall velocities in first-order phase transitions is of great importance for the prediction of gravitational wave signals and the matter-antimatter asymmetry. However, it is a challenging task which typically…
In this paper, a new general formula for the sound speed in adiabatic conditions ( S = const ) has been established. The sound speed depends on the mass density {\rho} (p,T ) and the internal energy per unit mass E(p,T ), both expressed as…
The speed of sound of simple dense fluids is shown to exhibit a pronounced freezing temperature scaling of the form $c_{\rm s}/v_{\rm T}\simeq \sqrt{\gamma} +\alpha (T_{\rm fr}/T)^{\beta}$, where $c_s$ is the speed of sound, $v_{\rm T}$ is…
He-4 is known to become superfluid at very low temperatures. This effect is now generally accepted to be connected with BEC (Bose-Einstein Condensation). The dispersion relation of pressure waves in superfluid He-4 has been determined at…