A new test for dark matter particles of low mass

Detection of a surprisingly high flux of positron annihilation radiation from the inner galaxy has motivated the proposal that dark matter is made of weakly interacting light particles (possibly as light as the electron). This scenario is extremely hard to test in current high energy physics experiments. Here, however, we demonstrate that the current value of the electron anomalous magnetic moment already has the required precision to unambiguously test the light dark matter hypothesis. If confirmed, the implications for astrophysics are far-reaching.     

Inhomogeneous and homogeneous broadening effects onnuclear resonance experiments

Inhomogeneous broadening of resonance lines causes a reduction of absorption in nuclear resonance experiments. This is particularly devastating to the observation of the Mössbauer effect in isomers like ¹⁰⁷Ag with a half-life of 44s.It has been suggested in the literature that homogeneous broadening can provide overlap of resonance lines and thus theMössbauer effect can be recovered. The analysis presented in this paper shows that this is not the case for Mössbauer experiments, unless the radiative width Γ_Γ also increases. Although overlap occurs when the lines are homogeneously broadened to a total width Γ_{_}H which exceeds the natural width Γ, and the inhomogeneous width Δ, the Mössbauer absorption remains low because it is proportional to the factor of Γ_γ/Γ _H.     

Superfluorescence in the presence of inhomogeneousbroadening and relaxation

In this paper we show how inhomogeneous broadening produces dephasing, inhibits cooperative emission and thus reduces the intensity of the SF pulse. We also show how electronic relaxation or time-dependent hyperfine interactions can mollify the effect of inhomogeneous broadening so that SF can be recovered. This revised version was published online in August 2006 with corrections to the Cover Date.     

The propagation in metal tubing of ultrasonic wave modes equivalent to Lamb waves

The generation of ultrasonic wave modes in thin-walled metal tubing has been investigated experimentally using piezoelectric ultrasonic probes. It is shown that the L(0, 1) mode, which is comparable to the A₀ Lamb wave mode in flat plate, can be generated with acceptable efficiency. The L(0, 2) mode (compare the S₀ Lamb wave mode) is generated rather less efficiently, while its greater group velocity tends to enhance the resolution problems so caused.The initial probe designs were inefficient in that a considerable amount of ultrasonic ‘noise’ was also present which could mask ultrasonic pulses of interest. This would be especially so for short range operation. An improved probe design reduced this background noise to a more acceptable level.The propagation of the L(0, 1) mode around a length of bent (U-form) tubing has also been investigated and it is shown that the ultrasonic pulse is both attenuated and lengthened, while structure has also been introduced. The theoretical implications of this are discussed. Finally a small amount of work is presented on the interaction of both modes with artificial defects.     

The transfer of ultrasonic energy in the diffraction technique for crack sizing

During the past five years a programme of work has been carried out at the Harwell NDT Centre concerned with the use of scattered or diffracted ultrasound in the sizing of defects. The progress made in this direction and some of the possible lines of further research have been indicated in other papers.^1–3 This diffraction technique has been evaluated on a number of fatigue cracked specimens and it has been found that accuracies in crack sizing consistently better than $\text{1}\text{2}$ mm have been achieved. The technique is thus thought to be on the verge of application to practical ndt problems.The basis of the sizing technique is the recognition and subsequent timing of various discrete ultrasonic pulses, as will be outlined later. The scope of the technique thus depends on these signals remaining both well separated and large enough to be resolved in a wide range of examination geometries. The purpose of the present paper is to consider the mechanisms by which two of the ultrasonic pulses of importance in the diffraction technique are produced. In this connection the current theoretical situation is reviewed and this is compared, where appropriate, with experimental measurements taken during the period of this work.     

Dark matter seeding and the kinematics and rotation of neutron stars

Self-annihilation of dark matter accreted from the galactic halo in the inner regions of neutron stars may significantly affect their kinematical properties, namely velocity kicks and rotation patterns. We find that if a stable long-lived single or multiple strangelet off-center seed forms leading to an asymmetric ejection of matter and radiation, there is a significant modification in linear and angular momentum observables of the star.     

Operator algebras and a theorem of Dieudonne

LetA be aC*-algebra with second dualA″. Let (φ _n)(n=1,...) be a sequence in the dual ofA such that limφ _n(a) exists for eacha εA. In general, this does not imply that limφ _n(x) exists for eachx εA″. But if limφ _n(p) exists whenever p is the range projection of a positive self-adjoint element of the unit ball ofA, then it is shown that limφ _n(x) does exist for eachx inA″. This is a non-commutative generalisation of a celebrated theorem of Dieudonné. A new proof of Dieudonné’s theorem, for positive measures, is given here. The proof of the main result makes use of Dieudonné’s original theorem.     

Synthesis of 9-geranylterpinolene as a mixture of isomers,and synthesis of α- and β-springene,possible kairomones of the beech leaf-mining weevil,Orchestes fagi (L.)

The beech leaf-mining weevil, Orchestes fagi (L.), also known as the beech flea weevil, is a common and widespread pest of beech, Fagus sylvatica L., in its native Europe. It now appears to be well established in Nova Scotia, Canada. We have previously reported the synthesis of 9-geranyl-p-cymene and 9-geranyl-α-terpinene, as they are both found in eclosing beech buds, and have researched the synthesis of other diterpenes that are isomers of 9-geranyl-α-terpinene. We now wish to report a synthesis of the diterpene 9-geranylterpinolene as a mixture of isomers, as a novel diterpene, and as a possible kairomone of O. fagi. Also, all trans-α-springene, its 3Z-isomer, and β-springene were synthesized as a mixture, as well as pure β-springene, utilizing known methods.