arXiv subjects
Publications and source records attributed to Ranjan Chaudhury.
A quantum spin model representing tautomeric mutation is proposed for any DNA molecule. Based on this model, the quantum mechanical calculations for mutational rate and complementarity restoring repair rate in the replication processes are carried out. A possible application to a real biological system is discussed.
The spin dynamics of the semiclassical Heisenberg model with uniaxial anisotropy, on the layered triangular lattice with antiferromagnetic coupling for both intralayer nearest neighbor interaction and interlayer interaction is studied both in the ordered phase and in the paramagnetic phase, using the Monte Carlo-molecular dynamics technique. The important quantities calculated are the full dynamic structure function $S(\bf q, ω)$, the chiral dynamic structure function $S_{chi}(ω)$, the static order parameter and some thermodynamic quantities. Our results show the existence of propagating modes corresponding to both $S(\bf q, ω)$ and $S_{chi}(ω)$ in the ordered phase, supporting the recent conjectures. Our results for the static properties show the magnetic ordering in each layer to be of coplanar 3-sublattice type deviating from 120 degree structure. In the presence of magnetic trimerization however, we find the 3-sublattice structure to be weakened alongwith the tendency towards non-coplanarity of the spins.
An effective theory for quantum spin system in low dimension is constructed in the finite-q regime. It is shown that there are field configurations for which Wess-Zumino term contributes to the partition functions as topological term for ferromagnet as well as antiferromagnet in both one and two dimensional lattice,in contrast to the long wave length regime.
The possibility of existence of topological excitations in the anisotropic quantum Heisenberg model in one and two spatial dimensions is studied using coherent state method. It is found that a part of the Wess-Zumino term contributes to the partition function, as a topological term for ferromagnets in the long wavelength limit in both one and two dimensions. In particular, the XY limit of the two-dimensional anisotropic ferromagnet is shown to retain the topological excitations, as expected from the quantum Kosterlitz-Thouless scenario.
Van der Waerden's (VDW) colouring theorem in combinatoric number theory [1] has scope for physical applications.The solution of the two colour case has enabled the construction of an explicit mapping of an infinite, one dimensional antiferromagnetic Ising system to an effective pseudo- ferromagnetic one with the coupling constants in the two cases becoming related [2].Here the three colour problem is solved and the results are used to obtain new insights in the theory of complex lattices, particularly those relating to ternary alloys. The existence of these mappings of a multicolour lattice onto a monochromatic one with different couplings illustrates {\it a new form of duality}.