Temperature dependence of the radiative lifetime in porous silicon

Abstract

Using photoluminescence decay measurements the radiative lifetime of porous silicon is investigated between liquid helium and room temperature. The radiative recombination mechanism in porous silicon is in essence the same as in bulk silicon, viz. a phonon mediated indirect transition. The functional dependence of the lifetime on photon energy reveals the confinement character of the recombination carriers. The high external photoluminescence efficiency is well explained by the reduction of nonradiative recombination owing to low mobility, to low dimensionality, and to the extreme low surface recombination rate, and is further enhanced by the relatively small refractive index.

Superstring one-loop and gravitino contributions to planckian scattering

“…Gravitational scattering at Planckian energies and small angles was investigated in the past [1][2][3][4] and is still under discussion [5,6], in order to understand the role of short distances in string theory and quantum gravity. A similar investigation was also performed [7] from the point of view of reggeized graviton exchange in the multi-Regge kinematics.…”

Physics of trans-Planckian gravity

“…[7]). The discovery of low scale quantum gravity scenarios [8,9] promoted this possibility to a potentially experimentallyobservable phenomenon.…”

Stochastic tachyon fluctuations, marginal deformations, and shock waves in string theory

“…It would also be interesting to consider scattering of particles and strings in the shock wave geometries we have obtained and in particular associate the results (for instance the pole structure of the S-matrix [9]) with the CFT properties of the corresponding backgrounds.…”

“…The main motivation for dealing with gravitational shock waves is that, as was argued in [8], gravitational interactions dominate any other type of interaction at Planckian energies (see [9,10,11,12]) and that in an S-matrix approach to black hole physics [8], one needs to take into account the interactions between Hawking emitted and infalling particles as well as their effect on the original black hole geometry. Thus, having the exact solutions to Einstein's equations (and for that matter to any other theory of gravity) of a background geometry coupled to a distribution of massless matter moving along a null hypersurface is equivalent to fully taking into account all classical backreaction-type effects.…”