9,289 research outputs found
Evolution of Structure Functions And Their Moments In Chiral Field Theory
Evolution of structure functions and their moments at low and moderate
is studied in the chiral field theory. Evolution equations based on
perturbation expansion in the coupling constant of the effective theory are
derived and solved for the moments. The kernels of evolution arising from
different processes have been calculated with contributions from direct and
cross channels, the interference terms being non-negligible in the kinematic
regions under consideration. This is shown to lead to flavor-dependence of the
kernels which manifests in observable effects. The invalidity of the
probabilistic approach to the evolution process is also pointed out.Comment: 18 pages, LaTex, 5 figure
Dual purpose optical instrument capable of simultaneously acting as spectrometer and diffractometer
A dual purpose optical instrument is described capable of simultaneously acting as a spectrometer and diffractometer to respectively perform elemental and structural analysis of an unknown sample. The diffractometer portion of the instrument employs a modified form of Seeman-Bohlin focusing which involves providing a line source of X-rays, a sample, and a detector, all on the same focal circle. The spectrometer portion of the instrument employs a fixedly mounted X-ray energy detector mounted outside of the plane of the focal circle
Microscopic Mechanism of Shear Bands in Amorphous Solids
The fundamental instability responsible for the shear localization which
results in shear bands in amorphous solids remains unknown despite enormous
amount of research, both experimental and theoretical. As this is the main
mechanism for the failure of metallic glasses, understanding the instability is
invaluable in finding how to stabilize such materials against the tendency to
shear localize. In this Letter we explain the mechanism for shear localization
under shear, which is the appearance of highly correlated lines of Eshelby-like
quadrupolar singularities which organize the non-affine plastic flow of the
amorphous solid into a shear band. We prove analytically that such highly
correlated solutions in which \C N quadrupoles are aligned with equal
orientations are minimum energy states when the strain is high enough. The line
lies at 45 degrees to the compressive stress
Entropic Origin of the Growth of Relaxation Times in Simple Glassy Liquids
Transitions between ``glassy'' local minima of a model free-energy functional
for a dense hard-sphere system are studied numerically using a
``microcanonical'' Monte Carlo method that enables us to obtain the transition
probability as a function of the free energy and the Monte Carlo ``time''. The
growth of the height of the effective free energy barrier with density is found
to be consistent with a Vogel-Fulcher law. The dependence of the transition
probability on time indicates that this growth is primarily due to entropic
effects arising from the difficulty of finding low-free-energy saddle points
connecting glassy minima.Comment: Four pages, plus three postscript figure
Investigation of the role of neutron transfer in the fusion of 32,34S with 197Au,208Pb using quasi-elastic scattering
Excitation functions for quasi-elastic scattering have been measured at
backward angles for the systems 32,34S+197Au and 32,34S+208Pb for energies
spanning the Coulomb barrier. Representative distributions, sensitive to the
low energy part of the fusion barrier distribution, have been extracted from
the data. For the fusion reactions of 32,34S with 197Au couplings related to
the nuclear structure of 197Au appear to be dominant in shaping the low energy
part of the barrier distibution. For the system 32S+208Pb the barrier
distribution is broader and extends further to lower energies, than in the case
of 34S+208Pb. This is consistent with the interpretation that the neutron
pick-up channels are energetically more favoured in the 32S induced reaction
and therefore couple more strongly to the relative motion. It may also be due
to the increased collectivity of 32S, when compared with 34S.Comment: 11 pages, 5 figure
- …