Emergence of classical behavior from the quantum spin

Classical Hamiltonian system of a point moving on a sphere of fixed radius is shown to emerge from the constrained evolution of quantum spin. The constrained quantum evolution corresponds to an appropriate coarse-graining of the quantum states into equivalence classes, and forces the equivalence classes to evolve as single units representing the classical states. The coarse-grained quantum spin with the constrained evolution in the limit of the large spin becomes indistinguishable from the classical system

REPRODUCTIVE PARAMETERS OF THOROUGHBRED MARES IN CROATIA

For the purpose of gaining better cognition on Thoroughbred breeding in Croatia, reproductive parameters of 87 Thoroughbred mares were analyzed. An average age of the first covering and foaling were 5.9 and 6.6 years, respectively. The average gestation length was 341.1 days and the most frequent foaling period (20.2% of foalings) was recorded between 336 to 340 days of gestation. Prolonged gestation period (p<0.05) was determined in colts. The gestation length was the longest in January (344.4 days) and the shortest in July (324.0 days). Between the gestation length and the age of the mare no significant correlation was found. There was a trend of foaling rate decreasing in mares older than 11 years. The highest number of successively registered foalings with 10 live born foals was observed on 2 individual samples. The greatest number of foalings occurred in April (30.9%), whilst there was no foaling in October. The genders were 50.6% male and 49.4% female foals. The incidence of abortions was 7.3%. Although indicators point to the breeding strategy heading towards the right direction, by educating the owners and with frequent veterinary supervision, especially for twin reduction, the reproductive performance could be enhanced

Geometric Phase for Analytically Solvable Driven Time-Dependent Two-Level Quantum Systems

Geometric phase for novel analytical solutions (Barnes and Das Sarma) of time-dependent two-level quantum systems is discussed, specifically for a general single-axis driving term, which is represented by a function J(t) in the Hamiltonian, and its corresponding evolution operator. It is demonstrated how general results for corresponding phases (total, dynamic and geometric) can be obtained. Using a specific case, it was found that over time in which the driving field is appreciably different from zero, the corresponding geometric phase changes (in the specific example by Δ β ≈ 0.8 radians) thus enabling detection. The results are relevant to qubit control and to quantum computing applications

Dancing Light: Counterpropagating Beams in Photorefractive Crystals

A review of work on the dynamical behavior of counterpropagating incoherent laser beams in photorefractive crystals is presented. Numerical study of counterpropagating beams of different type is carried out, in both space and time, using an appropriate theoretical model. The development of patterns in broad hyper-Gaussian counterpropagating beams in saturable Kerr-like media is investigated, by varying the width of beams. Rotational properties of counterpropagating mutually incoherent self-trapped vortex beams in optically induced fixed photonic lattices are also investigated numerically. One of the fundamental quantum mechanical phenomena is observed for the counterpropagating beams in photonic lattices, the tunneling of light from the first to the higher-order bands of the lattice band gap spectrum. The transfer of angular momentum from vortex beams to optically induced photonic lattices is also demonstrated. For the interacting beams it is found that the sum of angular momenta of counterpropagating components is not a conserved quantity, but the difference is. In the fixed lattices there is always a considerable loss of angular momentum