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

Engineering exotic phases for topologically-protected quantum computation by emulating quantum dimer models

We use a nonperturbative extended contractor renormalization (ENCORE) method for engineering quantum devices for the implementation of topologically protected quantum bits described by an effective quantum dimer model on the triangular lattice. By tuning the couplings of the device, topological protection might be achieved if the ratio between effective two-dimer interactions and flip amplitudes lies in the liquid phase of the phase diagram of the quantum dimer model. For a proposal based on a quantum Josephson junction array [L. B. Ioffe {\it et al.}, Nature (London) {\bf 415}, 503 (2002)] our results show that optimal operational temperatures below 1 mK can only be obtained if extra interactions and dimer flips, which are not present in the standard quantum dimer model and involve three or four dimers, are included. It is unclear if these extra terms in the quantum dimer Hamiltonian destroy the liquid phase needed for quantum computation. Minimizing the effects of multi-dimer terms would require energy scales in the nano-Kelvin regime. An alternative implementation based on cold atomic or molecular gases loaded into optical lattices is also discussed, and it is shown that the small energy scales involved--implying long operational times--make such a device impractical. Given the many orders of magnitude between bare couplings in devices, and the topological gap, the realization of topological phases in quantum devices requires careful engineering and large bare interaction scales.Comment: 12 pages, 10 figure

Gauge theory on nonassociative spaces

We show how to do gauge theory on the octonions and other nonassociative algebras such as `fuzzy $R^4$' models proposed in string theory. We use the theory of quasialgebras obtained by cochain twist introduced previously. The gauge theory in this case is twisting-equivalent to usual gauge theory on the underlying classical space. We give a general U(1)-Yang-Mills example for any quasi-algebra and a full description of the moduli space of flat connections in this theory for the cube $Z_2^3$ and hence for the octonions. We also obtain further results about the octonions themselves; an explicit Moyal-product description of them as a nonassociative quantisation of functions on the cube, and a characterisation of their cochain twist as invariant under Fourier transform.Comment: 24 pages latex, two .eps figure

Braided Cyclic Cocycles and Non-Associative Geometry

We use monoidal category methods to study the noncommutative geometry of nonassociative algebras obtained by a Drinfeld-type cochain twist. These are the so-called quasialgebras and include the octonions as braided-commutative but nonassociative coordinate rings, as well as quasialgebra versions \CC_{q}(G) of the standard q-deformation quantum groups. We introduce the notion of ribbon algebras in the category, which are algebras equipped with a suitable generalised automorphism $\sigma$, and obtain the required generalisation of cyclic cohomology. We show that this \emph{braided cyclic cocohomology} is invariant under a cochain twist. We also extend to our generalisation the relation between cyclic cohomology and differential calculus on the ribbon quasialgebra. The paper includes differential calculus and cyclic cocycles on the octonions as a finite nonassociative geometry, as well as the algebraic noncommutative torus as an associative example.Comment: 36 pages latex, 9 figure

New results for the t-J model in ladders: Changes in the spin liquid state with applied magnetic field. Implications for the cuprates

Exact Diagonalization calculations are presented for the t-J model in the presence of a uniform magnetic field. Results for 2xL ladders (L=8,10,12) and 4x4 square clusters with 1 and 2 holes indicate that the diamagnetic response to a perpendicular magnetic field tends to induce a spin liquid state in the spin background. The zero-field spin liquid state of a two-leg ladder is reinforced by the magnetic field: a considerable increase of rung antiferromagnetic correlations is observed for J/t up to 0.6, for 1 and 2 holes. Pair-breaking is also clearly observed in the ladders and seems to be associated in part with changes promoted by the field in the spin correlations around the zero-field pair. In the 4x4 cluster, the numerical results seem to indicate that the field-induced spin liquid state competes with the zero-field antiferromagnetic short-range-order, the spin liquid state being favored by higher doping and smaller values of J/t. It is interesting to note that the field-effect can also be observed in a 2x2 plaquette with 1 and 2 holes. This opens up the possibility of gaining a qualitative understanding of the effect.Comment: 16 pages, 7 figures, latex New results adde

Appetite-Related Eating Behaviours: An Overview of Assessment Methods, Determinants and Effects on Children's Weight

Identifying the underlying child-eating behaviours that contribute to weight differences across growth has been a constant challenge. This report reviews the various literature approaches for assessing appetite regulation. In doing so, it attempts to understand how appetite control develops and determines the eating habits in early childhood, and its effects on children's weight status. The interaction between homeostatic and hedonic mechanisms largely explains the appetite regulation process. Homeostatic mechanisms are mediated by the biological need to maintain the body's energy reserves, increasing the motivation to eat. On the contrary, the hedonic mechanisms are mediated by food reward, increasing the craving for high-palatable foods and triggering the release of dopamine and serotonin. There are many biological methods (plasma measurements of hormones, like leptin, ghrelin and insulin) and behavioural evaluation methods of appetite. The Children's Eating Behaviour Questionnaire is most commonly used, due to its adequate psychometric properties tested in several population settings. The development of eating behaviours begins in utero, and several determinants may contribute to a decrease in the ability to self-regulate dietary intake. Examples include genetic predisposition, the first taste experiences and the family environment, a key determinant in this process. Several eating behaviours contribute most to childhood obesity. Among them, are the external eating (eating by external stimuli, such as the mere presence of the food or its smell), food restriction (which may potentiate the uninhibited increased intake of the restricted foods) and emotional eating (intake due to emotional variations, especially negative feelings). These eating behaviours have been linked to childhood obesity. (c) 2018 S. Karger AG, BaselA.O. received funds from the FCT Investigator Programme (IF/01350/2015), with FEDER funds through the Operational Programme Competitiveness and Internationalisation, in addition to national funding from the Foundation for Science and Technology (FCT; Portuguese Ministry of Science, Technology and Higher Education), co-funded by the FCT and the POPH/FSE Program

Parameter space of experimental chaotic circuits with high-precision control parameters

ACKNOWLEDGMENTS The authors thank Professor Iberê Luiz Caldas for the suggestions and encouragement. The authors F.F.G.d.S., R.M.R., J.C.S., and H.A.A. acknowledge the Brazilian agency CNPq and state agencies FAPEMIG, FAPESP, and FAPESC, and M.S.B. also acknowledges the EPSRC Grant Ref. No. EP/I032606/1.Peer reviewedPublisher PD

Melhoramento da população de milho CMS 14.

A ausencia de sistemas de produção tecnificados, a não utilizacao de insumos modernos e, principalmente a não disponibilidade de sementes melhoradas, são fatores que concorrem de maneira decisiva para as baixas produtividades de milho no Amapá. As cultivares tradicionalmente plantadas como Pretinha e Palha Roxa não apresentaram rendimentos satisfatorios. Com o objetivo de se obter uma nova variedade de milho, a partir da população CMS 14 (Pool 25), a mais produtiva que a original, realizou-se nesta população o primeiro ciclo de seleção massal estratificada. Os trabalhos foram conduzidos no município de Mazagão, em solo Gley Pouco Humico hidromorfico.bitstream/item/65042/1/AP-1985-melhoramento-populacao-milho.pd

Absorção via foliar de aminoácidos em mudas de videira cv. Thompson seedless em cultivo hidropônico.

Este trabalho teve por objetivo quantificar o teor de N proveniente dos aminoácidos, absorvidos via foliar, em mudas de videira da cultivar Thompson Seedless