The isospin forbidden 1− → 0+ transition in 40Ca

The isospin forbidden transition 1^? (6.95 MeV) → 0⁺ (g.s.) in ⁴⁰Ca is explained within a model that mixes isospin through single-particle energy differences and the two-body Coulomb interaction. There is no need to introduce an isospin non-conserving part of the nucleon-nucleon interaction to explain this anomalously fast transition.     

The electronic specific heat of a one-dimensional crystal with a sinusoidal potential

Summary The electronic specific heat of a one-dimensional crystal with a sinusoidal potential is examined in the second quantized formulation. Two electrons per lattice site are assumed to be under the influence of the potential; electron-electron interactions via Coulomb repulsion are ignored. The Green’s function equation-of-motion technique is utilized to obtain an exact expression for the specific heat forK, the allowed linear momenta, restricted to two Brillouin ones. The specific heat shows metal, semiconductor-to-metal, or insulator-to-metal behavior as a function of temperature, dependent upon the well depth of the sinusoidal potential.

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Riassunto Sie esamina il calore specifico elettronico di un cristallo unidimensionale con un potenziale sinusoidale nella seconda formulazione quantizzata. Si assume che due elettroni per loco del reticolo cristallino siano sotto l’influenza del potenziale; si ignorano le interazioni elettrone-elettrone mediante repulsione di Coulomb. Si utilizza la tecnica dell’equazione di moto della funzione di Green per ottenere un’espressione esatta per il calore specifico perK, gli impulsi lineari permessi, ristretta a due zone di Brillouin. Il calore specifico mostra un comportamento tipo metallo, da semiconduttore a metallo, o da isolante a metallo in funzione della temperatura, in dipendenza dalla profondità del pozzo del potenziale sinusoidale.

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Резюме Используя метод вторичного квантования, исследуется электронная удельная теплоемкость одномерного кристалла с синусоидальным потенциалом. Предполагается, что в узле решетки имеются два электрона: электрон-электронными взаимодействиями пренебрегают. Используется уравнение функции Грина для получения точного выражения для удельной теплоемкости дляK, принимая во внимание импульсы, ограниченные двумя зонами Бриллюэна. Удельная теплоемкость обнатуживает различные свойства в зависимости от температуры и глубины ямы синусоидального потенциала.

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A modified Green's function determination of the conduction and insulator limit conductivities of the one-dimensional, half-filled band, Hubbard model

A modified Green's function determination of the conduction and insulator limit conductivities of the one-dimensional, half-filled band, Hubbard model is presented in a simplified version to avoid the difficulties which are encountered in some instances in utilizing commutator Green's functions in first order response determinations to external perturbations.