3 research outputs found
The longitudinal fivebrane and tachyon condensation in matrix theory
We study a configuration in matrix theory carying longitudinal fivebrane
charge, i.e. a D0-D4 bound state. We calculate the one-loop effective potential
between a D0-D4 bound state and a D0-anti-D4 bound state and compare our
results to a supergravity calculation. Next, we identify the tachyonic
fluctuations in the D0-D4 and D0-anti-D4 system. We analyse classically the
action for these tachyons and find solutions to the equations of motion
corresponding to tachyon condensation.Comment: 19 page
Similar level of polyteny in bands and interbands of Drosophila giant chromosomes
The giant polytene chromosomes of Drosophila melanogaster have long been of interest to the geneticist because of the visible map of the genome provided by their characteristic banding patterns. An issue in the understanding of the molecular basis of chromosome banding has been whether the chromosomal DNA is replicated to the same extent in bands and interbands. Although various suggestions have been put forward the point has remained controversial. We have isolated 315 kilobases (kb) of contiguous Drosophila genomic DNA which spans an interval of approximately 13 bands and interbands of the polytene chromosomes. We report here the measurement of the relative level of DNA replication in polytene chromosomes of 84 adjacent restriction fragments of our cloned DNA. We conclude that there are no significant differences in the level of polyteny within the large band and between bands and interbands of this region. This result supports the 'folded fibre' model of polytene chromosome organization, rather than models involving disproportionate replication along the banding pattern