Energija osnovnog stanja u proširenom 2D Hubbardovom modelu za konačan sustav s egzaktnom dijagonalizacijom

Using an exact analytical diagonalization for an extended Hubbard model, we study the first nearest-neighbour repulsion effect on the behaviour of a two-dimensional system of finite size at low density of electrons. The obtained results show that the introduction of the nearest-neighbour off-site interaction allows the correlation effects to become more remarkable and to play an essential role in the electron dynamics, and this off-site interaction encourages the formation of double occupancies.Primjenom egzaktne analitičke dijagonalizacije za proširen Hubbardov model proučavamo učinak odbojne sile među prvim susjedima na svojstva konačnog dvodimenzijskog sustava pri niskim gustoćama elektrona. Postignuti ishodi pokazuju da uvođenje prvo-susjedskog međudjelovanja izvan sustava omogućuje pojačanje korelacijskih učinaka, igra bitnu ulogu u dinamici elektrona, te to međudjelovanje izvan sustava podstiče stvaranje dvostrukih popunjenja

Chaplygin gas braneworld inflation according to WMAP7 data

We consider a Chaplygin gas model with an exponential potential in framework of braneworld inflation. We apply the slow-roll approximation in the high-energy limit to derive various inflationary spectrum perturbation parameters. We show that the inflation observables depend only on the e-folding number N and the final value of the slow-roll parameter e(end). Whereas for small running of the scalar spectral index dns/dlnk, the inflation observables are in good agreement with recent WMAP7 data.Comment: 5 pages, 3 figure

Energija osnovnog stanja u proširenom 2D Hubbardovom modelu za konačan sustav s egzaktnom dijagonalizacijom

Using an exact analytical diagonalization for an extended Hubbard model, we study the first nearest-neighbour repulsion effect on the behaviour of a two-dimensional system of finite size at low density of electrons. The obtained results show that the introduction of the nearest-neighbour off-site interaction allows the correlation effects to become more remarkable and to play an essential role in the electron dynamics, and this off-site interaction encourages the formation of double occupancies.Primjenom egzaktne analitičke dijagonalizacije za proširen Hubbardov model proučavamo učinak odbojne sile među prvim susjedima na svojstva konačnog dvodimenzijskog sustava pri niskim gustoćama elektrona. Postignuti ishodi pokazuju da uvođenje prvo-susjedskog međudjelovanja izvan sustava omogućuje pojačanje korelacijskih učinaka, igra bitnu ulogu u dinamici elektrona, te to međudjelovanje izvan sustava podstiče stvaranje dvostrukih popunjenja

Extension of Self Consistent RPA method to off-site Hubbard Model

We are interested in the possibility that a generalization of Self Consistent Random Phase Approximation (SCRPA) to the Extended Hubbard Model can lead us to accurate estimations of the ground state energy, for closed chains in one dimension with periodic boundary conditions: N=2 (two states problem). We have considered an extended Hubbard model including on-site and off-site interactions, we have compared the SCRPA with a Direct Analytical(DA) results for the ground state energy, and have shown that SCRPA solves the two states problem exactly for any value of U (on-site interaction energy), V2 (off-site interaction energy with opposite spins) and (off-site interaction energy with same spins).We are interested in the possibility that a generalization of Self Consistent Random Phase Approximation (SCRPA) to the Extended Hubbard Model can lead us to accurate estimations of the ground state energy, for closed chains in one dimension with periodic boundary conditions: N=2 (two states problem). We have considered an extended Hubbard model including on-site and off-site interactions, we have compared the SCRPA with a Direct Analytical(DA) results for the ground state energy, and have shown that SCRPA solves the two states problem exactly for any value of U (on-site interaction energy), V2 (off-site interaction energy with opposite spins) and (off-site interaction energy with same spins)