No Arabic abstract
By using a Hamiltonian based on the coupling through flux lines, we have calculated the interaction energy between two fermions via massless bosons as well as via massive particles. In the case of interaction via massless bosons we obtain an equivalent expression for the Coulombs energy on the form, where is the fine structure constant. In the case of the interaction via massive particles we obtain that the interaction energy contains a term building the potential well. Taking into account the spin-spin interaction of the nucleons, we show that this interaction modulates the interaction potential through a cosine factor. The obtained results are in good agreement with experimental data, for example, of deuteron.
We derive the free energy for fermions and bosons from fragmentation data. Inspired by the symmetry and pairing energy of the Weizsacker mass formula we obtain the free energy of fermions (nucleons) and bosons (alphas and deuterons) using Landaus free energy approach. We confirm previously obtained results for fermions and show that the free energy for alpha particles is negative and very close to the free energy for ideal Bose gases. Deuterons behave more similarly to fermions (positive free energy) rather than bosons. This is due to their low binding energy, which makes them very fragile, i.e., easily formed and destroyed. We show that the {alpha}-particle fraction is dominant at all temperatures and densities explored in this work. This is consistent with their negative free energy, which favors clusterization of nuclear matter into {alpha}-particles at subsaturation densities and finite temperatures. The role of finite open systems and Coulomb repulsion is addressed.
We propose further tests of the assumption that the mass of the heavy standard particles ($Z,W,t,...$) arises from a special coupling with dark matter. We look for effects of new interactions due to dark matter exchanges between heavy particles in several $e^+e^-$ and hadronic collision processes.
Taking a two interacting scalar toy model with interaction term $gphichi^2$, we study the production of $chi$-particles coming from the decay of an asymptotic and highly occupied beam of $phi$-particles. We perform a non-perturbative analysis coming from parametric resonant instabilities and investigate the possibility that massive $chi$-particles are produced from decays of massless $phi$-particles from the beam. Although this process is not present in a perturbative analysis, our non perturbative approach allows it to happen under certain conditions. For a momentum $p$ of the beam particles and a mass $m_chi$ of the produced ones, we find that the decay is allowed if the energy density of the beam exceeds the instability threshold $p^2mc^4/(2g^2)$. We also provide an analytical expression for the spontaneous decay rate at the earliest time.
While many physical properties of graphene can be understood qualitatively on the basis of bare Dirac bands, there is specific evidence that electron-electron (EE) and electron-phonon (EP) interactions can also play an important role. We discuss strategies for extracting separate images of the EE and EP interactions as they present themselves in the electron spectral density and related self-energies. While for momentum, $k$, equal to its Fermi value, $k_F$, a composite structure is obtained which can be difficult to separate into its two constituent parts, at smaller values of $k$ the spectral function shows distinct incoherent sidebands on the left and right of the main quasiparticle line. These image respectively the EE and EP interactions, each being most prominent in its own energy window. We employ a maximum entropy inversion technique on the self energy to reveal the electron-phonon spectral density separate from the excitation spectrum due to coulomb correlations. Our calculations show that this technique can provide important new insights into inelastic scattering processes in graphene.
We discuss the zeroes and poles of the determinant of the retarded Green function ($det G_R$) at zero frequency in a holographic system of charged massless fermions interacting via a dipole coupling. For large negative values of the dipole coupling constant $p$, $det G_R$ possesses only poles pointing to a Fermi liquid phase. We show that a duality exists relating systems of opposite $p$. This maps poles of $det G_R$ at large negative $p$ to zeroes of $det G_R$ at large positive $p$, indicating that the latter corresponds to a Mott insulator phase. This duality suggests that the properties of a Mott insulator can be studied by mapping the system to a Fermi liquid. Finally, for small values of $p$, $det G_R$ contains both poles and zeroes (pseudo-gap phase).