Spin Excitation Spectra of Anisotropic Spin-1/21/2 Triangular Lattice Heisenberg Antiferromagnets

Investigation of dynamical excitations is difficult but crucial to the understanding of many exotic quantum phenomena discovered in quantum materials. This is particularly true for highly frustrated quantum antiferromagnets whose dynamical properties deviate strongly from theoretical predictions made based on the spin-wave or other approximations. Here we present a large-scale numerical calculation on the dynamical correlation functions of spin-$1/2$ triangular Heisenberg model using a state-of-the-art tensor network renormalization group method. The calculated results allow us to gain for the first time a comprehensive picture on the nature of spin excitation spectra in this highly frustrated quantum system. It provides a quantitative account for all the key features of the dynamical spectra disclosed by inelastic neutron scattering measurements for $\rm Ba_3CoSb_2O_9$, revealing the importance of the interplay between low- and high-energy excitations and its renormalization effect to the low-energy magnon bands and high-energy continuums. We identify the longitudinal Higgs modes in the intermediate-energy scale and predict the energy and momentum dependence of spectral functions along the three principal axes that can be verified by polarized neutron scattering experiments. Furthermore, we find that the spin excitation spectra weakly depend on the anisotropic ratio of the antiferromagnetic interaction.Comment: 6 pages, 3 figures, and a Supplemental Materia

3-(4-Meth­oxy­phen­yl)pyrido[2,3-b]pyrazine

In the title mol­ecule, C14H11N3O, the benzene ring is twisted by 14.0 (2)° from the plane through the fused ring system. In the crystal, π–π inter­actions [centroid–centroid distances = 3.609 (1), 3.639 (1) and 3.735 (1) Å] form stacks of mol­ecules propagating along the b axis. The crystal packing is further stabilized by weak inter­molecular C—H⋯O and C—H⋯N hydrogen bonds

cis-Bis[2-(1,3-benzothia­zol-2-yl)-1-(4-fluoro­phen­yl)ethen­yl](pentane-2,4-dionato-κ2 O,O′)iridium(III)

In the title compound, [Ir(C15H9FNS)2(C5H7O2)], the Ir atom is hexa­coordinated by three chelating ligands, with two cyclo­metalated 2-(1,3-benzothia­zol-2-yl)-1-(4-fluoro­phen­yl)ethenyl ligands showing N,C-bidentate coordination and an O,O′-bidenate pentane-2,4-dionate anion, thereby forming a distorted octa­hedral enviroment

4-[4,5-Bis(pyridin-2-yl)-1H-imidazol-2-yl]phenol monohydrate

In the title hydrate, C19H14N4O·H2O, the dihedral angle between the two pyridine rings is 38.0 (2)°. The dihedral angle between the imidazole and benzene rings is 25.3 (2)°. The crystal structure is stabilized by inter­molecular O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds

Quantum theory of light diffraction

At present, the theory of light diffraction only has the simple wave-optical approach. In this paper, we study light diffraction with the approach of relativistic quantum theory. We find that the slit length, slit width, slit thickness and wave-length of light have affected to the diffraction intensity and form of diffraction pattern. However, the effect of slit thickness on the diffraction pattern can not be explained by wave-optical approach, and it can be explained in quantum theory. We compare the theoretical results with single and multiple slits experiment data, and find the theoretical results are accordance with the experiment data. Otherwise, we give some theory prediction. We think all the new prediction will be tested by the light diffraction experiment.Comment: 10 page

Entropy inflection and invisible low-energy states: Defensive alliance example

Lower temperature leads to a higher probability of visiting low-energy states. This intuitive belief underlies most physics-inspired strategies for addressing hard optimization problems. For instance, the popular simulated annealing (SA) dynamics is expected to approach a ground state if the temperature is lowered appropriately. Here, we demonstrate that this belief is not always justified. Specifically, we employ the cavity method to analyze the minimum strong defensive alliance problem and discover a bifurcation in the solution space, induced by an inflection point in the entropy-energy profile. While easily accessible configurations are associated with the lower-free-energy branch, the low-energy configurations are associated with the higher-free-energy branch within the same temperature range. There is a discontinuous phase transition between the high-energy configurations and the ground states, which generally cannot be followed by SA. We introduce an energy-clamping strategy to obtain superior solutions by following the higher-free-energy branch, overcoming the limitations of SA

Systemic lupus erythematosus: some historical aspects

O autor apresenta alguns aspectos aliciantes da história do lúpus sistémico. Cita as descrições de Willan, Bateman, Biett, Cazenave, Hebra e Kaposi; aborda a publicação de Libman e Sacks da endocardite verrugosa atípica e os trabalhos de Gross, Klemperer, Baehr, Pollack e Shifrin que levam a estabelecer-se o conceito de doenças difusas do colagénio. Descreve a descoberta sucessiva de marcadores da doença por Hargraves, com as células LE, por Friou com os anticorpos antinucleares por Pincus com os anticorpos anti ADN. Aflora ainda os primeiros avanços terapêuticos com os corticoesteróides e imunossupressores. Numa segunda parte revela a evolução histórica do lúpus em Portugal, descrevendo as fi guras da medicina portuguesa que se debruçaram sobre este tema, dando especial relevo à obra de Bernardino António Gomes que, em 1820, publicou um trabalho no qual classifi cava o lúpus em seis variedades