7 research outputs found
Cosmological Acceleration from Virtual Gravitons
Intrinsic properties of the space itself and quantum fluctuations of its
geometry are sufficient to provide a mechanism for the acceleration of
cosmological expansion (dark energy effect). Applying
Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy approach to self-consistent
equations of one-loop quantum gravity, we found exact solutions that yield
acceleration. The permanent creation and annihilation of virtual gravitons is
not in exact balance because of the expansion of the Universe. The excess
energy comes from the spontaneous process of graviton creation and is trapped
by the background. It provides the macroscopic quantum effect of cosmic
acceleration.Comment: 6 pages, REVTeX
Pressure-induced alpha-to-omega transition in titanium metal: A systematic study of the effects of uniaxial stress
We investigated the effects of uniaxial stress on the pressure-induced
alpha-to-omega transition in pure titanium (Ti) by means of angle dispersive
x-ray diffraction in a diamond-anvil cell. Experiments under four different
pressure environments reveal that: (1) the onset of the transition depends on
the pressure medium used, going from 4.9 GPa (no pressure medium) to 10.5 GPa
(argon pressure medium); (2) the a and w phases coexist over a rather large
pressure range, which depends on the pressure medium employed; (3) the
hysteresis and quenchability of the w phase is affected by differences in the
sample pressure environment; and (4) a short term laser-heating of Ti lowers
the alpha-to-omega transition pressure. Possible transition mechanisms are
discussed in the light of the present results, which clearly demonstrated the
influence of uniaxial stress in the alpha-to-omega transition.Comment: 16 pages, 6 figures, 1 tabl