Magnetization plateaux and jumps in a class of frustrated ladders: A simple route to a complex behaviour

We study the occurrence of plateaux and jumps in the magnetization curves of a class of frustrated ladders for which the Hamiltonian can be written in terms of the total spin of a rung. We argue on the basis of exact diagonalization of finite clusters that the ground state energy as a function of magnetization can be obtained as the minimum - with Maxwell constructions if necessary - of the energies of a small set of spin chains with mixed spins. This allows us to predict with very elementary methods the existence of plateaux and jumps in the magnetization curves in a large parameter range, and to provide very accurate estimates of these magnetization curves from exact or DMRG results for the relevant spin chains.Comment: 14 pages REVTeX, 7 PostScript figures included using psfig.sty; this is the final version to appear in Eur. Phys. J B; some references added and a few other minor change

Eminent Domain - Restrictive Covenants - Compensability of Equitable Servitudes

During appellee sanitation district\u27s negotiations for the purchase of a tract of land owned by one Peterson, the eighteen appellants and thirty-seven other owners of land in the vicinity of Peterson\u27s tract executed with Peterson and each other reciprocal covenants whereby each party agreed that his land should be restricted to certain uses, the use contemplated by appellee for Peterson\u27s land being specifically excluded. When appellee and Peterson failed to reach an agreement in their negotiations and appellee filed a petition for condemnation of the land, appellants presented a cross-petition to the trial court, requesting that they be allowed to intervene in the action as parties respondent and demanding that they be awarded damages because appellee\u27s proposed use of the condemned land would violate their restrictive agreements with Peterson. On appeal from a judgment denying the cross-petition, held, affirmed. Agreements between private parties could not restrict the exercise of the power of eminent domain by an agency of the state. Such agreements could only create contract rights, not property rights compensable in a condemnation proceeding. Also, to require compensation for the taking of such rights would contravene public policy in placing a large and restrictive burden upon the condemning authority. Smith v. Clifton Sanitation District, (Colo. 1956) 300 P. (2d) 548

ENCORE: An Extended Contractor Renormalization algorithm

Contractor renormalization (CORE) is a real-space renormalization-group method to derive effective Hamiltionians for microscopic models. The original CORE method is based on a real-space decomposition of the lattice into small blocks and the effective degrees of freedom on the lattice are tensor products of those on the small blocks. We present an extension of the CORE method that overcomes this restriction. Our generalization allows the application of CORE to derive arbitrary effective models whose Hilbert space is not just a tensor product of local degrees of freedom. The method is especially well suited to search for microscopic models to emulate low-energy exotic models and can guide the design of quantum devices.Comment: 5 pages, 4 figure

Agency - Apparent Authority - Liability of Corporation on Unauthorized Note of General Manager

Welch, the general manager, executive vice-president, treasurer, and director of petitioner corporation, requested that respondent, a salesman employed by the corporation, loan petitioner $25,000. Respondent complied, and Welch executed and delivered to respondent a note for the amount of the loan, signed by himself as vice-president and treasurer. After Welch had appropriated the money to his own uses, respondent obtained a judgment by confession against petitioner on the note. On trial of a petition to open the judgment, held, dismissed. Welch had acted with apparent authority in giving respondent petitioner\u27s note, respondent had reasonably relied upon this appearance in accepting the note, and petitioner was therefore bound by the note. Petition of Mulco Products, Inc., (Del. 1956) 123 A. (2d) 95

Phase diagram of Bose-Fermi mixtures in one-dimensional optical lattices

The ground state phase diagram of the one-dimensional Bose-Fermi Hubbard model is studied in the canonical ensemble using a quantum Monte Carlo method. We focus on the case where both species have half filling in order to maximize the pairing correlations between the bosons and the fermions. In case of equal hopping we distinguish between phase separation, a Luttinger liquid phase and a phase characterized by strong singlet pairing between the species. True long-range density waves exist with unequal hopping amplitudes.Comment: 5 pages, 5 figures, replaced with published versio