Starting from a Born-Oppenheimer decomposition of the Wheeler-DeWitt equation for quantum cosmology matter-gravity system, we have performed Wigner-Weyl transformation and obtained equations involving Wigner function scale factor its conjugate momentum. This has allowed us to study in more detail than previously approach classical limit gravitation way time emerges such limit. To lowest order r...

In the Born-Oppenheimer approximation, the electronic wave function is typically real-valued and hence the electronic flux density (current density) seems to vanish. This is unfortunate for chemistry, because it precludes the possibility to monitor the electronic motion associated with the nuclear motion during chemical rearrangements from a Born-Oppenheimer simulation of the process. We study ...

We investigate spin effects in four-quark systems consisting of two heavy anti-bottom quarks and two light up/down quarks. To this end we use the Born-Oppenheimer approximation. We utilize potentials of two static antiquarks in the presence of two quarks of finite mass computed via lattice QCD and solve a coupled-channel Schrödinger equation for the anti-bottom-anti-bottom separation. Without t...

We present a method to identify transition states and minimum energy paths for martensitic solid-solid phase transformations, thereby allowing quantification of the activation energies of such transformations. Our approach is a generalization of a previous method for identifying transition states for chemical reactions, namely the climbing image-nudged elastic band algorithm, where here the glo...

Numerical studies of the vector electromagnetic fields in plano-concave microresonators have recently revealed that a photonic analogue of spin-orbit coupling can occur in paraxial geometries. Laguerre-Gauss modes with circular polarization are then no longer the correct eigenstates, even if the resonator is axially symmetric. A crucial role in this effect is played by the presence of a boundar...

The calculation of linear and nonlinear optical response as well as nonadiabatic curve crossing processes depends on the time evolution of the electronic coherences ~off-diagonal elements of the density matrix!. Unlike their diagonal counterparts, the off-diagonal elements do not have an obvious classical limit. A semiclassical approximation for the nonlinear optical response function, which re...

Tetraquarks QQq¯q¯ are found to be described remarkably well with the Quantum Chromodynamics version of Hydrogen bond, as treated Born-Oppenheimer approximation. We show robustness method by computing mass observed Tcc tetraquark following two different paths. Relying on this, we provide a prediction for expected Tbb particle. The average sizes tetraquarks estimated approximately 3–5GeV−1. As c...

The spectrum of D3+ is analyzed using a spectroscopically determined effective H3+ potential [B. M. Dinelli, S. Miller, and J. Tennyson, J. Mol. Spectrosc. 1BS, 71 (1994)] and an accurate ab initio potential [G. C. Lie and D. Frye, J. Chem. Phys. 9B, 6784 (1992)]. Calculations suggest that the major error in the potential of Lie and Frye is due to the Born-Oppenheimer approximation. D3+ spectro...

The development of theories and methods devoted to the accurate calculation of the electronic quasi-particle states and levels of molecules, clusters and solids is of prime importance to interpret the experimental data. These quantum systems are often modelled by using the Born-Oppenheimer approximation where the coupling between the electrons and vibrational modes is not fully taken into accou...