A new perspective on nonrelativistic gravity

The geometric reformulation of Newton??s gravity is known as Newton-Cartan theory. We compare the traditional derivation of this theory with a new, algebraic derivation, based on the gauging of a centrally extended Galilean symmetry algebra. In this comparison the role of the central charge gauge field will be explained. In particular, we show that the scalar potential following from this procedure coincides with the one given by the theory of Cartan. Our procedure can be generalized to describe other nonrelativistic limits of gravity involving gravitating strings.     

A new perspective on thermonuclear reactions

正The mechanism of nucleosynthesis from light particles into heavier ones in the early universe has attracted a lot of attention in nuclear astrophysics [1-3]. With great efforts made both experimentally and theoretically, many data of thermonuclear reaction rates on stable targets are now available, and large data sets of nuclear astrophysics regarding the theoretical work on the binding energy, cross section and rate calculations are obtainable via different models. For example, the JINA REACLIB database, which is maintained by the JINA Collaboration, covers more than 8000 nuclides and over 80000 nuclear reactions,     

A proposal for new surface magnetism studies with a repolarization method

A new spectroscopic method to study surface magnetism is proposed. The method measures the time-evolution of spin polarization due to the magnetic coupling with polarized electron spins of unpolarized and slow radioactive probes. Because of the expectedly high sensitivity and efficiency, a large field of applications will be opened by using slow positive muons,¹²B nuclei, etc.     

A new perspective on optoelectric conversion in conjugated polymers

Photoexcitation of a neutral soliton will create a polaron and a charged soliton.According to a tight-binding model and a nonadiabatic method,we investigate the dynamical process of these two photogenerated charge carriers in an external electric field.It is found that the polaron and the soliton can pass through each other,which excludes the possibility of carrier recombination that usually occurs in existing organic solar cells.The results indicate a more efficient way to realize the optoelectric conversion by photoexciting polymer materials with soliton defects.On the other hand,it is found that solitons take on greater stability than polarons during collision.     

Gravity and gauge: A new perspective

Realization of the Poincaré groupP ₁₀ as a subgroup ofGL(5,R) that maps a 4-dimensional affine set into itself has been shown to lead to a direct Yang-Mills gauging process. This paper discusses the differences between direct gauge theory forP ₁₀ and previously published works. These differences are fundamental, both physically and mathematically, and lead to marked departures from previous concepts and interpretations. The translation subgroup is correctly gauged; the metric structure and metric compatibility are derived from the gauging process rather than assumed; spin structures are automatically incorporated in a consistent manner; the local holonomy group is shown to be the component of the Lorentz group connected to the identity; the geometric analog of Yang-Mills minimal coupling precludes dependence of the free gauge field Lagranian on torsion; and the theory reduces exactly to general relativity when the momentumenergy complex is symmetric and all matter fields are spin-free. Gravitational effects on neutral test particles are shown to arise from the compensating 1-forms for local action of Lorentz boosts. The compensating 1-forms for local action of the translation subgroup may be interpreted as space-time dislocations, while the compensating 1-forms for the rotation subgroup can be viewed as space-time disclinations. Unfortunately, there are no clear physical meanings that can be ascribed to space-time dislocations or disclinations.     

A new perspective on anisotropy and multiple energy gaps in superconductors

New perspective on superconducting anisotropy and multiple energy gaps: direct experimental evidence shows that widely accepted anisotropy and multiple energy gap interpretations of tunneling data are consistent with a voltage divider model and may not relate to intrinsic superconducting properties. The model also accounts for other common data anomalies.     

Dependency distance: A new perspective on syntactic patterns in natural languages

Dependency distance, measured by the linear distance between two syntactically related words in a sentence, is generally held as an important index of memory burden and an indicator of syntactic difficulty. Since this constraint of memory is common for all human beings, there may well be a universal preference for dependency distance minimization (DDM) for the sake of reducing memory burden. This human-driven language universal is supported by big data analyses of various corpora that consistently report shorter overall dependency distance in natural languages than in artificial random languages and long-tailed distributions featuring a majority of short dependencies and a minority of long ones. Human languages, as complex systems, seem to have evolved to come up with diverse syntactic patterns under the universal pressure for dependency distance minimization. However, there always exist a small number of long-distance dependencies in natural languages, which may reflect some other biological or functional constraints. Language system may adapt itself to these sporadic long-distance dependencies. It is these universal constraints that have shaped such a rich diversity of syntactic patterns in human languages.     

Tailoring magnetism in artificially structured materials: the new frontier

The current standard of electronic devices and data storage media has reached a level such that magnetic materials have to be fabricated on a nanometer scale. In particular, the emerging concept of spintronics, which is based on fact that current carriers have not only charge but also spin, requires the assembling of nanometer-sized magnetic structures with desired magnetic properties. It is this background that motivates scientists and engineers to attempt to grow and characterize magnetic objects at smaller and smaller length scales, from 2D films and multilayers to 1D wires and eventually to 0D dots. In this article, some of the most significant progress in recent years in the effort of growing artificially structured magnetic materials are reviewed. The new structural and magnetic properties of these materials are discussed, with an emphasis on the correlation between structure and magnetism, which also serves as guidance for improving their magnetic properties. The emerging emphasis is on converting the existing knowledge into growing and studying low-dimensional complex materials, which promise to have considerably higher “tuning” ability for desired properties.     

A new measurement of the weak magnetism term in the betaspectra of B and N

The betaspectra of ¹²B and ¹²N have been measured with a NaI crystal as spectrometer. Assuming a shape correction factor 1 + aW + bW² and b₋ = 1.106 × 10⁻⁴ MeV⁻², b₊ = −1.397 × 10⁻⁴ MeV⁻², the spectra yield a₋ = (+0.91 ± 0.11) × 10⁻² MeV⁻¹ and a₊ = (−0.07 ± 0.09) × 10⁻² MeV⁻. the a₋ − a₊ = (+0.98 ± 0.09) × 10⁻² MeV⁻¹ is in agreement with the weak magnetism prediction.     

Superconductivity,magnetism and metastability of new ternary iridium borides

Superconductivity has been found in the rare earth iridium borides with the general formula MIr₄B₄ and in the pseudoternary (Y_xLu_1?x)?Ir₄B₄ system, M being a rare earth element. The pure phase in itself is only metastable at best. The compounds were found to crystallize with the primitive tetragonal CeCo₄B₄-type structure. The close correlation between superconductivity, magnetism and structural metastability is demonstrated with the study of the pseudoternary systems M(Ir_xRh_1?x)₄B₄ (x = 0.1 and 0.5) and Er(Ir_xRh_1?x)₄B₄.     

A new perspective on the integrability of Inozemtsev’s elliptic spin chain

The aim of this paper is studying from an alternative point of view the integrability of the spin chain with long-range elliptic interactions introduced by Inozemtsev. Our analysis relies on some well-established conjectures characterizing the chaotic vs. integrable behavior of a quantum system, formulated in terms of statistical properties of its spectrum. More precisely, we study the distribution of consecutive levels of the (unfolded) spectrum, the power spectrum of the spectral fluctuations, the average degeneracy, and the equivalence to a classical vertex model. Our results are consistent with the general consensus that this model is integrable, and that it is closer in this respect to the Heisenberg chain than to its trigonometric limit (the Haldane–Shastry chain). On the other hand, we present some numerical and analytical evidence showing that the level density of Inozemtsev’s chain is asymptotically Gaussian as the number of spins tends to infinity, as is the case with the Haldane–Shastry chain. We are also able to compute analytically the mean and the standard deviation of the spectrum, showing that their asymptotic behavior coincides with that of the Haldane–Shastry chain.     

Cation to anion stoichiometry of chromite: A new perspective

Ferric to ferrous ratios of a batch of chromite samples from the Bushveld Complex, South Africa, were measured to calculate the cation to oxygen stoichiometry per unit cell. Cation deficiency, due to post-magmatic oxidation of Fe²⁺ to Fe³⁺ is widespread. Oxidised chromite reduces more readily than unoxidised material and naturally occurring non-stoichiometric chromite is likely to be a more suitable feedstock for the ferro-alloys industry. This factor is often overlooked during routine mineralogical characterisations. This revised version was published online in August 2006 with corrections to the Cover Date.