arXiv subjects

R. J. Lombard

Publications and source records attributed to R. J. Lombard.

7 recordsLinked to original sources

arXiv2004

Description of Heavy Quark Systems by means of Energy Dependent Potentials

We apply, for the first time, an energy dependent Schrodinger equation to describe static properties of heavy quark systems, i.e. charmonium and bottonium. We show that a good description of the eigenstates and reasonable values for the widths can be obtained. Values of the radii and of the density at the origin are also given. We compare the results to those deduced with a Schrodinger equation implemented with potentials used so far. We note that the energy dependence of the confining potential provides a natural mechanism for the saturation of the spectra. Our results introduce a new class of potentials for the description of heavy quark systems.

hep-ph↗

arXiv2003

Wave equations with energy dependent potentials

We study wave equations with energy dependent potentials. Simple analytical models are found useful to illustrate difficulties encountered with the calculation and interpretation of observables. A formal analysis shows under which conditions such equations can be handled as evolution equation of quantum theory with an energy dependent potential. Once these conditions are met, such theory can be transformed into ordinary quantum theory.

quant-ph↗

arXiv2003

Short versus long range interactions and the size of two-body weakly bound objects

Very weakly bound systems may manifest intriguing "universal" properties, independent of the specific interaction which keeps the system bound. An interesting example is given by relations between the size of the system and the separation energy, or scaling laws. So far, scaling laws have been investigated for short-range and long-range (repulsive) potentials. We report here on scaling laws for weakly bound two-body systems valid for a larger class of potentials, i.e. short-range potentials having a repulsive core and long-range attractive potentials. We emphasize analogies and differences between the short- and the long-range case. In particular, we show that the emergence of halos is a threshold phenomenon which can arise when the system is bound not only by short-range interactions but also by long-range ones, and this for any value of the orbital angular momentum $\ell$. These results enlarge the image of halo systems we are accustomed to.

nucl-th↗

arXiv1999

Nucleation in dilute 3He-4He liquid mixtures at low temperatures

We present a study of phase separation from supersaturated 3He-4He liquid mixtures at low temperatures addressing both the degree of critical supersaturation Dx and the thermal-to-quantum crossover temperature T* for the nucleation process. Two different nucleation seeds are investigated, namely 3He droplets and 4He vortex lines with cores filled with 3He. We have found that the experimental T* is reproduced when we consider that nucleation proceeds from 3He droplets, whereas Dx is reproduced when we consider 4He vortex lines filled with 3He. However, neither nucleation configuration is able to simultaneously reproduce the current experimental information on Dx and T*.

cond-mat↗

arXiv1998

Ring vortex destabilization in supersaturated 3He-4He liquid mixtures at low temperatures

The effect of ring vortices on the destabilization of supersaturated liquid helium mixtures at very low temperatures is investigated as a function of pressure. We have found that large ring vortices trigger the segregation of 3He at smaller values of the concentration than small ring vortices. Our calculations indicate that the existence of ring vortices in the mixture is a possible mechanism to understand the rather small degree of critical supersaturation found in the experiments.

cond-mat↗

arXiv1997

On the binding energy of double Λhypernuclei in the relativistic mean field theory

We calculate the binding energy of two $Λ$ hyperons bound to a nuclear core within the relativistic mean field theory. The starting point is a two-body relativistic equation of the Breit type suggested by the RMFT, and corrected for the two-particle interaction. We evaluate the 2 $Λ$ correlation energy and estimate the contribution of the $σ^*$ and $Φ$ mesons, acting solely between hyperons, to the bond energy $Δ{B_{ΛΛ}}$ of $^6_{ΛΛ}He$, $^{10}_{ΛΛ}Be$ and $^{13}_{ΛΛ}B$. Predictions of the $Δ{B_{ΛΛ}}$ A dependence are made for heavier $Λ$-hypernuclei.

nucl-th↗

arXiv1996

Quantum cavitation in liquid helium

Using a functional-integral approach, we have determined the temperature below which cavitation in liquid helium is driven by thermally assisted quantum tunneling. For both helium isotopes, we have obtained the crossover temperature in the whole range of allowed negative p essures. Our results are compatible with recent experimental results on 4He.

cond-mat↗