We propose numerical simulations of the Ashkin-Teller model as a foil for theoretical techniques for studying very weakly first-order phase transitions in three dimensions. The Ashkin-Teller model is a simple two-spin model whose parameters can be adjusted so that it has an arbitrarily weakly first-order phase transition. In this limit, there are quantities characterizing the firstorder transit...

In the well known Pöschl-Teller trigonometric potential well, a PT symmetric regularization x → x− i ε of the “impenetrable” end-point barriers is performed. This leads to the four different solvable generalizations of the model. As a byproduct, the scheme clarifies certain apparent paradoxes encountered in the classically forbidden coupling regime. PACS 03.65.Bz 03.65.Ca 03.65.Ge 02.60.Lj 11.3...

Moisture sorption studies have been carried out on 16 low moisture foodstuffs at 27°C and based on the major type of constituent, viz starch. fat, protein and high hygroscopicity. the isotherms have been divided into four groups. The moisture sorption behaviour over 0.060.92 water activity of the foods has indicated that the Brunauer-Emmett-Teller (BET) equation is applicable generally up to 0....

In this Communication we present the first theoretical/numerical treatment of nonadiabatic coupling terms (NACT) that originate from the Renner-Teller (RT) model, namely, those that follow from the splitting of an electronic level of a linear molecule when it becomes bent. These two newly formed states are characterized by different symmetries and are designated as A and B. Our main findings: (...

High-pressure optical-absorption measurements performed in CuWO(4) up to 20 GPa provide experimental evidence of the persistence of the Jahn-Teller (JT) distortion in the whole pressure range both in the low-pressure triclinic and in the high-pressure monoclinic phase. The electron-lattice couplings associated with the e(g)(E⊗e) and t(2g)(T⊗e) orbitals of Cu(2+) in CuWO(4) are obtained from cor...

We investigate Jahn-Teller (JT) polaritons, which emerge from the interaction of two normal-incidence electromagnetic modes with perpendicular polarizations in a Fabry-Perot cavity resonator JT active systems. These polaritons are characterized by mixed $(+/-)$--circular polarization that originates molecular vibronic coupling material subsystem. Consequently, exchange photonic and angular mome...