The leading in 1/N c spin-flavor symmetry breaking mass splittings, of order N 0 c , in excited non-strange Baryons are shown to be given, up to two-body operators, by three different effective Hamiltonians: Thomas precession spin-orbit, spin-isospin tensor, and spin-orbit with isospin exchange. Explicit expressions for their matrix elements between low excited Baryons are obtained, and the str...

It is demonstrated that the time evolution of the heteronuclear polarization-transfer process in a dipolar-coupled nuclear spin system can be reversed, leading to the observation of cross-polarization echoes. The cross-polarization echoes are induced by consecutive application of two pulse trains that produce effective Hamiltonians that differ only in sign. Cross-polarization echoes have been r...

The recently derived Fortuin, Kasteleyn and Ginibre (FKG) inequalities for lattice gasses are investigated for higher order Ising spin systems and multi-component lattice gasses. Conditions are given for the validity of the FKG inequalities for higher order spin systems with Hamiltonians of the form used recently as models for various physical systems, e.g. He — He mixtures. We also investigate...

We construct Hamiltonians with only 1- and 2-body interactions that exhibit an exact non-Abelian gauge symmetry (specifically, combinatiorial symmetry). Our spin Hamiltonian realizes the quantum double associated to group of quaternions. It contains ferromagnetic anti-ferromagnetic ZZ ZZ...

We apply the contractor renormalization (CORE) method to the spin half Heisenberg antiferromagnet on the frustrated checkerboard and pyrochlore lattices. Their ground states are spin-gapped singlets which break lattice symmetry. Their effective Hamiltonians describe fluctuations of orthogonal singlet pairs on tetrahedral blocks, at an emergent low energy scale. We discuss low temperature thermo...

For a two-component bosonic system, the components can be mapped onto a pseudospin degree of freedom with spin quantum number S = 1/2. We provide a rigorous proof that for a wide-range of real Hamiltonians with component independent mass and interaction, the ground state is a ferromagnetic state with pseudospin fully polarized. The spin-wave excitations are studied and found to have quadratic d...

In this manuscript we review recent developments in the numerical simulations of bipartite SU(N) spin models by quantum Monte Carlo (QMC) methods. We provide an account of a large family of newly discovered sign-problem free spin models which can be simulated in their ground states on large lattices, containing O(10) spins, using the stochastic series expansion method with efficient loop algori...

We use an n-spin system with permutation symmetric zz-interaction for simulating arbitrary pair-interaction Hamiltonians. The calculation of the required time overhead is mathematically equivalent to a separability problem of n-qubit density matrices. We derive lower and upper bounds in terms of chromatic index and the spectrum of the interaction graph. The complexity measure defined by such a ...

We present a symplectic integrator, based on the implicit midpoint method, for classical spin systems where each spin is a unit vector in R{3}. Unlike splitting methods, it is defined for all Hamiltonians and is O(3)-equivariant, i.e., coordinate-independent. It is a rare example of a generating function for symplectic maps of a noncanonical phase space. It yields a new integrable discretizatio...

6 SO COUPLINGS IN LOW-DIMENSIONAL SEMICONDUCTORS 10 6.1 Rashba coupling in bulk 2DEG . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.2 Rashba coupling in quantum wires . . . . . . . . . . . . . . . . . . . . . . . . 15 6.2.1 Energy dispersion of Rashba spin-split transverse propagating subbands 15 6.2.2 Spin precession in Rashba quantum wires . . . . . . . . . . . . . . . . . 17 6.3 Di...