arXiv subjects
Publications and source records attributed to Nikolay Vitanov.
The multistate Majorana model in the presence of dissipation and dephasing is considered. It is proven that increasing the Hilbert space dimension the system becomes more and more fragile to quantum noise. The impossibility to recast the problem in the form of a set of independent spin-$1/2$ problems because of the presence of the noise is pointed out.
The formulation of the variational problems for the solute transport in a fluid layer in presence of double-diffusive thermal convection is discussed. It is shown that the variational functional obtained by Strauss can be generalized and the general functional leads to accurate upper bounds on the solute transport for the case of small and intermediate values of the Rayleigh number. The general functional however is a non-homogeneous one but for asymptotically large Rayleigh numbers it converges to the Strauss approximation. Thus for small and intermediate values of the Rayleigh numbers one should use the general functional and for vary large values of the Rayleigh numbers one can use the functional of Strauss.