Effective spin-fermion model for strongly correlated electrons

A modified spin-fermion model is proposed to describe the physics of the underdoped phase of the t-J model of strongly correlated electron

Limitations of the mean field slave-particle approximations

We show that the transformation properties of the mean field slave boson/fermion order parameters under an action of the global SU(2) group impose certain restrictions on their applications to describe the phase diagram of the t-J model.Comment: to appear in Phys. Rev.

Paracamallanus amazonensis sp. n. (Nematoda: Camallanidae) a parasite of the catfish, Hypophthalmus edentatus (Pisces: Hypophthalmidae) of the Brazilian Amazon

Paracamallanus amazonensis sp. n. (Nematoda: Camallanidae) is described from the intestine of a fish called "mapará", Hypophthalmus edentatus (Pisces: Hypophthalmidae) from Marchantaria Island, Solimões River, Amazonas State, Brazil. Of the six species described in the genus, P. amazonensis sp. n. resembles only P. cyathopharynx (BAYUS, 1923) because both have a buccal cavity divided into two parts posterior to the valves. The new species differs from P. cyathopharyrnx in having: 1) a buccal cavity without teeth; 2) 6 pairs of precloacal papillae and a single spicule in the male; 3) a vulva with the posterior lip in the form of a fold which projects anteriorly; 4) a pointed tail in the female. This is the first report of a genus of Paracamallanus YORKE & MAPLESTONE, 1926, in South America

Breakdown of the Fermi-liquid regime in the 2D Hubbard model from a two-loop field-theoretical renormalization group approach

We analyze the particle-hole symmetric two-dimensional Hubbard model on a square lattice starting from weak-to-moderate couplings by means of the field-theoretical renormalization group (RG) approach up to two-loop order. This method is essential in order to evaluate the effect of the momentum-resolved anomalous dimension $\eta(\textbf{p})$ which arises in the normal phase of this model on the corresponding low-energy single-particle excitations. As a result, we find important indications pointing to the existence of a non-Fermi liquid (NFL) regime at temperature $T\to 0$ displaying a truncated Fermi surface (FS) for a doping range exactly in between the well-known antiferromagnetic insulating and the $d_{x^2-y^2}$-wave singlet superconducting phases. This NFL evolves as a function of doping into a correlated metal with a large FS before the $d_{x^2-y^2}$-wave pairing susceptibility finally produces the dominant instability in the low-energy limit.Comment: 9 pages, 9 figures; published in Phys. Rev.

Ising t-J model close to half filling: A Monte Carlo study

Within the recently proposed doped-carrier representation of the projected lattice electron operators we derive a full Ising version of the t-J model. This model possesses the global discrete Z_2 symmetry as a maximal spin symmetry of the Hamiltonian at any values of the coupling constants, t and J. In contrast, in the spin anisotropic limit of the t-J model, usually referred to as the t-J_z model, the global SU(2) invariance is fully restored at J_z=0, so that only the spin-spin interaction has in that model the true Ising form. We discuss a relationship between those two models and the standard isotropic t-J model. We show that the low-energy quasiparticles in all three models share the qualitatively similar properties at low doping and small values of J/t. The main advantage of the proposed Ising t-J model over the t-J_z one is that the former allows for the unbiased Monte Carlo calculations on large clusters of up to 10^3 sites. Within this model we discuss in detail the destruction of the antiferromagnetic order by doping as well as the interplay between the AF order and hole mobility. We also discuss the effect of the exchange interaction and that of the next nearest neighbour hoppings on the destruction of the AF order at finite doping. We show that the short-range AF order is observed in a wide range of temperatures and dopings, much beyond the boundaries of the AF phase. We explicitly demonstrate that the local no double occupancy constraint plays the dominant role in destroying the magnetic order at finite doping. Finally, a role of inhomogeneities is discussed.Comment: 24 pages, 10 figure

The impact of the resource-based view and sustainability on the luxury fashion: A bibliometric review analysis

Interest in sustainable practices has increased in the luxury fashion industry. Resource-based view theory emerges as a strategic approach that guides companies to achieve a competitive advantage using sustainability. In this context, this thesis examines the influence of resource-based view and sustainability in luxury fashion. From a database consisting of 383 articles on resource-based view and sustainability, as well as 292 articles on luxury fashion, selected from the last five years of research, the main objective of this study is to create a bibliometric map that relates concepts and keywords. A rigorous screening process was used to make this selection, in addition to an analysis of the references cited in the articles. The aim of this study is to discuss and review the intrinsic meanings of this concept map, which is composed of three main subtopics: (1) Resource-based view, (2) Sustainability, and (3) Luxury fashion.O interesse em práticas sustentáveis tem aumentado na indústria da moda de luxo. A teoria da visão baseada em recursos surge como uma abordagem estratégica que orienta as empresas para alcançar uma vantagem competitiva usando a sustentabilidade. Nesse contexto, esta tese examina uma influência da visão baseada em recursos e sustentabilidade na moda de luxo. A partir de uma base de dados composta por 383 artigos sobre visão baseada em recursos e sustentabilidade, bem como 292 artigos sobre moda de luxo, selecionados a partir dos últimos cinco anos de pesquisa, o objetivo principal deste estudo é criar um mapa bibliométrico que relacione conceitos e palavras- chave. Um rigoroso processo de triagem foi usado para fazer essa seleção, além de uma análise das referências citadas nos artigos. O objetivo deste estudo é discutir e revisar os significados intrínsecos desse mapa de conceitos, que é composto por três subtópicos principais: (1) Visão baseada em recursos, (2) Sustentabilidade, (3) Moda de luxo