10 research outputs found
Surface state atoms and their contribution to the surface tension of quantum liquids
We investigate the new type of excitations on the surface of liquid helium.
These excitations, called surfons, appear because helium atoms have discrete
energy level at the liquid surface, being attracted to the surface by the van
der Waals force and repulsed at a hard-core interatomic distance. The
concentration of the surfons increases with temperature. The surfons propagate
along the surface and form a two-dimensional gas. Basing on the simple model of
the surfon microscopic structure, we estimate the surfon activation energy and
effective mass for both helium isotopes. We also calculate the contribution of
the surfons to the temperature dependence of the surface tension. This
contribution explains the great and long-standing discrepancy between theory
and experiment on this temperature dependence in both helium isotopes. The
achieved agreement between our theory and experiment is extremely high. The
comparison with experiment allows to extract the surfon activation energy and
effective mass. The values of these surfon microscopic parameters are in a
reasonable agreement with the calculated from the proposed simple model of
surfon structure.Comment: 10 pages, 6 figure
Critical temperature of the superfluid transition in bose liquids
A phenomenological criterion for the superfluid transition is proposed, which
is similar to the Lindemann criterion for the crystal melting. Then we derive a
new formula for the critical temperature, relating to the mean
kinetic energy per particle above the transition. The suppression of the
critical temperature in a sufficiently dense liquid is described as a result of
the quantum decoherence phenomenon. The theory can account for the observed
dependence of on density in liquid helium and results in an
estimate K for molecular hydrogen.Comment: 4 pages, 1 fi
Negative Kaons in Dense Baryonic Matter
Kaon polarization operator in dense baryonic matter of arbitrary isotopic
composition is calculated including s- and p-wave kaon-baryon interactions. The
regular part of the polarization operator is extracted from the realistic
kaon-nucleon interaction based on the chiral and 1/N_c expansion. Contributions
of the Lambda(1116), Sigma(1195), Sigma*(1385) resonances are taken explicitly
into account in the pole and regular terms with inclusion of mean-field
potentials. The baryon-baryon correlations are incorporated and fluctuation
contributions are estimated. Results are applied for K- in neutron star matter.
Within our model a second-order phase transition to the s-wave K- condensate
state occurs at rho_c \gsim 4 \rho_0 once the baryon-baryon correlations are
included. We show that the second-order phase transition to the p-wave
condensate state may occur at densities in
dependence on the parameter choice. We demonstrate that a first-order phase
transition to a proton-enriched (approximately isospin-symmetric) nucleon
matter with a p-wave K- condensate can occur at smaller densities, \rho\lsim 2
\rho_0. The transition is accompanied by the suppression of hyperon
concentrations.Comment: 41 pages, 24 figures, revtex4 styl
Neutrino Cooling of Neutron Stars. Medium effects
This review demonstrates that neutrino emission from dense hadronic component
in neutron stars is subject of strong modifications due to collective effects
in the nuclear matter. With the most important in-medium processes incorporated
in the cooling code an overall agreement with available soft X ray data can be
easily achieved. With these findings so called "standard" and "non-standard"
cooling scenarios are replaced by one general "nuclear medium cooling scenario"
which relates slow and rapid neutron star coolings to the star masses (interior
densities). In-medium effects take important part also at early hot stage of
neutron star evolution decreasing the neutrino opacity for less massive and
increasing for more massive neutron stars. A formalism for calculation of
neutrino radiation from nuclear matter is presented that treats on equal
footing one-nucleon and multiple-nucleon processes as well as reactions with
resonance bosons and condensates. Cooling history of neutron stars with quark
cores is also discussed.Comment: To be published in "Physics of Neutron Star Interiors", Eds. D.
Blaschke, N.K. Glendenning, A. Sedrakian, Springer, Heidelberg (2001
Theory of quantum nondegenerated liquids
We propose a theory of nondegenerated quantum liquids which is insensitive to the kind of particle statistics and which is applied to condensed helium. We take explicitly into account the fact that the atomic mass and the polarizability are small. We take as the zeroth approximation a system of hard spheres while the attractive forces and the softness of the atom are taken into account as small effects. We show that for temperatures T which are larger than the degeneracy temperature, but less than the temperature at which the atoms are destroyed (ionized), the only characteristic energy scale of the liquid is the energy K0 of its zero point oscillations - the value of the mean kinetic energy of an atom at T = 0. As a result of this fact the "quantum scaling" occurs, i.e., scale invariance of the thermodynamic and kinetic characteristics of the liquid under those changes in T and the density n which leave the reduced temperature T* = T/K unchanged. Through a transformation of the scales of T and n one can determine the thermodynamic functions of any quantum liquid, using the known experimental data of He4. We obtain relations between the thermodynamic characteristics of liquid He 3 and He4