Cusp-like Behavior Research Articles

Study of the Quadrupolar-Glass Region in Solid D_{2} via Proton Magnetic Resonance

Cusplike behavior in the spin-lattice relaxation time of a probe molecule ($o$-${\mathrm{H}}_{2}$) is used to locate the transition temperature (${T}_{c}$) to the quadrupolar glass phase of a host $o\ensuremath{-}{\mathrm{D}}_{2}\ensuremath{-}p\ensuremath{-}{\mathrm{D}}_{2}$ alloy for $p$-${\mathrm{D}}_{2}$ concentrations above 0.29. The values of ${T}_{c}$ obtained here are higher than those obtained from line-shape measurements. The spin-echo height is also strongly affected by the collapse of the correlation frequency spectrum near ${T}_{c}$.

Susceptibilities of spin glass models: a Monte Carlo study

The Monte Carlo method has been used to study the behaviour of Ising model spin glasses. Both the double delta function and Gaussian distributions of interaction strengths have been considered. No evidence for cusp-like behaviour is obtained, but the susceptibilities appear to diverge at low temperature.

Search for the spin glass transition using series methods

High-temperature series expansions for the nearest-neighbour Ising model of a spin glass are derived. The concentration dependence of the critical temperature is analysed by Pade methods, and no indication of a spin glass transition is observed. The analysis does not rule out cusplike behaviour.

Nonlinear effects in the shear viscosity of fluids near the critical point

We present a microscopic theory for the nonlinear shear viscosity of fluids near the critical point, and find that dependence on shear gradients should be observable in capillary viscometer experiments. We suggest that the leveling off (cusplike behavior) of viscosities that has been observed experimentally may be a result of shear gradient effects. Further experiments to test our theory are suggested.

Shear gradient dependence of the viscosity of critical mixtures

We present a theory of the nonlinear shear viscosity of fluids near the critical point, and suggest that the experimentally observed leveling off (cusplike behavior) of the excess viscosity may be due to shear gradient effects.

Total Cross Sections forπ−p→ΛK0from Threshold to 1.13GeVc

Total cross sections for ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\Lambda}{K}^{0}$ have been measured using optical spark chambers from threshold to $1.13\ensuremath{-}\frac{\mathrm{GeV}}{c}$ beam momentum in $19\ensuremath{-}\frac{\mathrm{MeV}}{c}$ intervals, but with a $1\ensuremath{-}\frac{\mathrm{MeV}}{c}$ resolution in the regions of the $\ensuremath{\Lambda}K$ and $\ensuremath{\Sigma}K$ thresholds. The behavior near $\ensuremath{\Lambda}K$ threshold indicates a significant $s$-wave contribution, but this experiment is unable to resolve any cusplike behavior in the region of the $\ensuremath{\Sigma}K$ thresholds. The cross section shows a broad peak in the vicinity of $1.05\ensuremath{-}\frac{\mathrm{GeV}}{\mathbf{c}}$ beam momentum.

Magnetic Susceptibility of Au–Fe Alloys

Over the past years there has been considerable interest in the magnetic properties of the Au(Fe) system. Mössbauer measurements indicate that a complicated type of long-range ordering occurs below concentrations c of ∼12 at.% Fe and extends down to c<1%. Yet no definitive susceptibility study has been carried out over a complete range of temperatures and concentrations in order to characterize the magnetic ordering. We have measured the low-field magnetic susceptibility χ(T) for a series of eight Au–Fe alloys (1–22 at.% Fe), and we observe a definite peak in χ at those ordering temperatures determined from the Mössbauer data. The magnitude of χ greatly increases with c, while the shape of χ(T) in the region of the peak changes from a cusp-like behavior at low c to a behavior for c≳17% in which χ(T) gently rises, then sharply falls. These behaviors confirm the existence of a long-range order suggtesive of antiferromagnetism at low c (≤8%) with a more typical ferromagnetic ordering at high c. At intermediate c (≈12%), χ(T) seems to indicate the presence of a mixed type of long-range order.

Energy Dependence of Reactions at Thresholds

As a development of Wigner's work on the subject, the behavior of nuclear reactions at thresholds is discussed by employing the $\mathcal{R}$-matrix formalism with special attention to the effect of a nuclear reaction threshold in a particular channel on the energy dependence in other channels. In addition to the characteristic cusp-like behavior for $L=0$, ${Z}_{1}{Z}_{2}=0$ it is found that for this case it is also possible to have another type of plot of cross section versus energy. The second type differs from the first by a relative change of sign of the extra effect on one side of the threshold.