Modern Physics Letters A

Transverse momentum dependence in the perturbative calculation of the pion electromagnetic form factor is re-analyzed. It is found that (a) the intrinsic transverse momentum dependence associated with the pion wave function significantly suppresses perturbative prediction for the pion form factor at the energy region of a few GeV, and (b) the transverse momentum dependence in the fermion propagator of the hard scattering leads to a mild reduction of the perturbative calculation. Our formalism is available for both the intermediate energy region (Q~ a few GeV) and the asymptotic energy region (Q→∞).

The infinite limit of matrix theory in four and 10 dimensions is described in terms of Moyal brackets. In those dimensions there exists a Bogomol'nyi bound to the Euclideanized version of these equations, which guarantees that solutions of the first-order equations also solve the second-order matrix theory equations. A general construction of such solutions in terms of a representation of the target space coordinates as nonlocal spinor bilinears, which are generalisations of the standard Wigner functions on phase space, is given.

A video trace analysis of 117 ultra heavy cosmic nuclei detected by NASA space shuttle borne lexan detectors has been presented here. The major axes of the elliptical track etch pits in the long hour etched detectors have been measured using a Hund microscope computerized for the measurements using a Pentium. The major axes distribution exhibits the existence of ultra heavy nuclei of charges of Z ranging from 72 to 96 compatible with the expected results from restricted energy loss calculations. The estimated actinide sub-actinide flux ratio has been found to be 0.0636±0.0248 which is comparable to the earlier observations by Fowler et al., Thompson et al. and O'Sullivan.

A new class of completely integrable models is constructed. These models are deformations of the famous integrable and exactly solvable Gaudin models. In contrast with the latter, they are quasi-exactly solvable, i.e. admit the algebraic Bethe ansatz solution only for some limited parts of the spectrum. An underlying algebra responsible for both the phenomena of complete integrability and quasi-exact solvability is constructed. We call it "quasi-Gaudin algebra" and demonstrate that it is a special non-Lie-algebraic deformation of the ordinary Gaudin algebra.

We study configurations of a single M five-brane in the geometry R⁷× Q where Q is the Taub–NUT space. Taking the IIA limit at each value of their modulus, two possible IIA configurations are revealed.

We discuss the scattering of two light particles in a D-brane background. It is known that, if one light particle strikes the D-brane at small impact parameter, quantum recoil effects induce entanglement entropy in both the excited D-brane and the scattered particle. In this letter we compute the asymptotic "out" state of a second light particle scattering off the D-brane at large impact parameter, showing that it also becomes mixed as a consequence of quantum D-brane recoil effects. We interpret this as a non-factorizing contribution to the superscattering operator $ for the two light particles in a Liouville D-brane background, that appears when quantum D-brane excitations are taken into account.

The process of electron–positron pair production by axion propagating in an external magnetic field is investigated in a model with only induced axion coupling to leptons. Contributions of the lowest and higher Landau levels are analyzed. The results we have obtained demonstrate a strong catalyzing influence of the field.

In this letter we indicate some of the first references on quantum deformations, we point out their physical problematic aspects and outline their invariant formulation which appears to be unknown in the rather vast literature in the field.