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تسجيل مستخدم جديدTheory for Quartet Condensation in Fermi Systems with Applications to Nuclei and Nuclear Matter
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The theory of quartet condensation is further developed. The onset of quartetting in homgeneous fermionic matter is studied with the help of an in-medium modified four fermion equation. It is found that at very low density quartetting wins over pairing. At zero temperature, in analogy to pairing, a set of equations for the quartet order parameter is given. Contrary to pairing, quartetting only exists for strong coupling and breaks down for weak coupling. Reasons for this finding are detailed. In an application to nuclear matter, the critical temperature for alpha particle condensation can reach values up to around 8 MeV. The disappearance of alpha particles with increasing density, i.e. the Mott transition, is investigated. In finite nuclei the Hoyle state, that is the second 0+ state of 12C is identified as an alpha-particle condensate state. It is conjectured that such states also exist in heavier n-alpha nuclei, like 16O, 20Ne, etc. The sixth 0+ state in 16O is proposed as an analogue to the Hoyle state. The Gross-Pitaevski equation is employed to make an estimate of the maximum number of alpha particles a condensate state can contain. Possible quartet condensation in other systems is discussed briefly.
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P. Schuck Institut de Physique Nucleaire
, Orsay
, France andn Laboratoire de Physique et de Modelisation des Milieux Condenses
2018
A comparison of pairing properties in cuprates and nuclear matter is briefly discussed. Quartet (alpha-particle) condensation is a very important aspect of nuclear physics. The physics of the Hoyle state in 12 C will be outlined and its crucial role for the existence of life on earth explained.
Current long baseline experiments aim at measuring neutrino oscillation parameters with a high precision. A critical quantity is the neutrino energy which can not be measured directly but has to be reconstructed from the observed hadrons. A good know
ledge of neutrino-nucleus interactions is thus necessary to minimize the systematic uncertainties in neutrino fluxes, backgrounds and detector responses. In particular final-state interactions inside the target nucleus modify considerably the particle yields through rescattering, charge-exchange and absorption. Nuclear effects can be described with our coupled channel GiBUU transport model where the neutrino first interacts with a bound nucleon producing secondary particles which are then transported out of the nucleus. In this contribution, we give some examples for the application of our model focusing in particular on the MiniBooNE and K2K experiments.
The relation of quarteting and clustering in atomic nuclei is discussed based on symmetry-considerations. This connection enables us to predict a complete high-energy cluster spectrum from the description of the low-energy quartet part. As an example
the $^{28}$Si nucleus is considered, including its well-established ground-state region, the recently proposed superdeformed band, and the high-lying molecular resonances.
The incompressibility (compression modulus) $K_{rm 0}$ of infinite symmetric nuclear matter at saturation density has become one of the major constraints on mean-field models of nuclear many-body systems as well as of models of high density matter in
astrophysical objects and heavy-ion collisions. We present a comprehensive re-analysis of recent data on GMR energies in even-even $^{rm 112-124}$Sn and $^{rm 106,100-116}$Cd and earlier data on 58 $le$ A $le$ 208 nuclei. The incompressibility of finite nuclei $K_{rm A}$ is expressed as a leptodermous expansion with volume, surface, isospin and Coulomb coefficients $K_{rm vol}$, $K_{rm surf}$, $K_tau$ and $K_{rm coul}$. textit{Assuming} that the volume coefficient $K_{rm vol}$ is identified with $K_{rm 0}$, the $K_{rm coul}$ = -(5.2 $pm$ 0.7) MeV and the contribution from the curvature term K$_{rm curv}$A$^{rm -2/3}$ in the expansion is neglected, compelling evidence is found for $K_{rm 0}$ to be in the range 250 $ < K_{rm 0} < $ 315 MeV, the ratio of the surface and volume coefficients $c = K_{rm surf}/K_{rm vol}$ to be between -2.4 and -1.6 and $K_{rm tau}$ between -840 and -350 MeV. We show that the generally accepted value of $K_{rm 0}$ = (240 $pm$ 20) MeV can be obtained from the fits provided $c sim$ -1, as predicted by the majority of mean-field models. However, the fits are significantly improved if $c$ is allowed to vary, leading to a range of $K_{rm 0}$, extended to higher values. A self-consistent simple (toy) model has been developed, which shows that the density dependence of the surface diffuseness of a vibrating nucleus plays a major role in determination of the ratio K$_{rm surf}/K_{rm vol}$ and yields predictions consistent with our findings.
Heavy mesons in nuclear matter and nuclei are analyzed within different frameworks, paying a special attention to unitarized coupled-channel approaches. Possible experimental signatures of the properties of these mesons in matter are addressed, in pa
rticular in connection with the future FAIR facility at GSI.
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