Related papers: Elementary excitations and heat capacity singulari…
In this thesis we investigate the instabilities of superfluids at finite superflow by means of a hydrodynamical approach. We find that at a finite value of the background superfluid velocity a hydrodynamic collective mode crosses to the…
We continue the study of the $u(2|2)$-supersymmetric extension of the Hubbard model in one dimension. We determine the excitation spectrum at zero temperature even in the sectors where the ground states are $u(2|2)$-descendants of Bethe…
We present the results of a variational calculation of the frequencies of the low-lying Landau two-fluid hydrodynamic modes in a trapped Fermi superfluid gas at unitarity. Landau's two-fluid hydrodynamics is expected to be the correct…
The thermodynamics of liquids and supercritical fluids is notorious for eluding a general theory, as can be done for crystalline solids on the basis of phonons and crystal symmetry. The extension of solid state notions such as…
We propose a fully $ \textit{ab initio} $ approach to predicting thermal attenuation in elastic helium atom scattering amplitudes, validated through strong agreement with experiments on Nb(100) and (3$\times$1)-O/Nb(100) surfaces. Our…
We study the effects of finite stellar temperatures on the oscillations of superfluid neutron stars. The importance of these effects is illustrated with a simple example of a radially pulsating general relativistic star. Two main effects…
We analyse some phenomenological implications of the most general semi-holographic models for non-Fermi liquids that have emerged with inputs from the holographic correspondence. We find generalizations of Landau-Silin equations with few…
We calculate the spectrum of inertial oscillation modes in a slowly rotating superfluid neutron star, including, for the first time, both the effects of finite temperatures and entrainment between superfluid neutrons and protons. We work in…
The nuclear collective excitations are studied within Landau Fermi liquid theory. By using the nucleon-nucleon interaction of the linear sigma-omega model, the nuclear collective excitation energies of different values of $l$ are obtained,…
The interior of mature neutron stars is expected to contain superfluid neutrons and superconducting protons. The influence of temperature and currents on superfluid properties is studied within the self-consistent time-dependent nuclear…
Superfluidity is a well-characterized quantum phenomenon which entails frictionless-motion of mesoscopic particles through a superfluid, such as $^4$He or dilute atomic-gases at very low temperatures. As shown by Landau, the incompatibility…
We find that pancake dipolar condensates can exhibit a roton-maxon character of the excitation spectrum, so far only observed in superfluid helium. We also obtain a condition for the dynamical stability of these condensates. The spectrum…
Superconductivity, the lossless flow of electric current, occurs typically at very low temperatures. A possible exception is highly pressurized hydrogen, for which room temperature superconductivity has been predicted. However, as a result…
We study single-electron quantum dots on helium surface created by electrodes submerged into the helium. The intradot potential is electrostatically controlled. We find the electron energy spectrum and identify relaxation mechanisms. Strong…
We study elementary low energy excitations inside a supersolid. We find that the coupling between the longitudinal lattice vibration mode and the superfluid mode leads to two longitudinal modes (one upper branch and one lower branch) inside…
We study the normal state spectral properties of the fermionic excitations in the Boson-Fermion model. The fermionic single particle excitations show a flattening of the dispersion as the Fermi vector ${\bf k}_{_F}$ is approached from…
Specific heat has had an important role in the study of superfluidity and superconductivity, and could provide important information about the fractional quantum Hall effect as well. However, traditional measurements of the specific heat of…
We explore excitation and ionization by neutron impact as a novel tool for the investigation of electron-electron correlations in helium. We present single and double ionization spectra calculated in accurate numerical ab-initio simulations…
A semi-phenomenological model of a many-particle system of 4He atoms is proposed, in which a helium atom is considered as a complex consisting of a nucleus and a bound pair of electrons in the singlet state. At zero temperature, there are…
We report the first measurement of the excitation spectrum and the static structure factor of a Bose-Einstein condensate. The excitation spectrum displays a linear phonon regime, as well as a parabolic single-particle regime. The linear…